U.S. patent application number 14/030464 was filed with the patent office on 2014-01-16 for optical inspection device, electromagnetic wave detection method, electromagnetic wave detection device, organism observation method, microscope, endoscope, and optical tomographic image generation device.
This patent application is currently assigned to OLYMPUS CORPORATION. The applicant listed for this patent is OLYMPUS CORPORATION. Invention is credited to Kenji TAIRA, Shinichi TAKIMOTO, Hiroyoshi YAJIMA.
Application Number | 20140018685 14/030464 |
Document ID | / |
Family ID | 41254957 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140018685 |
Kind Code |
A1 |
TAIRA; Kenji ; et
al. |
January 16, 2014 |
OPTICAL INSPECTION DEVICE, ELECTROMAGNETIC WAVE DETECTION METHOD,
ELECTROMAGNETIC WAVE DETECTION DEVICE, ORGANISM OBSERVATION METHOD,
MICROSCOPE, ENDOSCOPE, AND OPTICAL TOMOGRAPHIC IMAGE GENERATION
DEVICE
Abstract
An optical inspection device 1, comprising a light generation
means 2, a light irradiation means 3 irradiating an object to be
inspected 4 with light generated from the light generation means 2
and a photodetection means 6 photoelectrically converting signal
light obtained from the object to be inspected 4 through
irradiation of light by the light irradiation means 3, and
inspecting the object to be inspected 4 based on output from the
photodetection means 6, wherein a light amplification means 5
amplifying signal light obtained from the object to be inspected 4
is provided. There is thus provided an optical inspection device
capable of photoelectically converting signal light from the object
to be inspected with high sensitivity and promptly with its
inexpensive configuration without increasing the intensity of light
with which the object to be inspected is irradiated and without
using an expensive low-noise and high-sensitivity
photodetector.
Inventors: |
TAIRA; Kenji; (Tokyo,
JP) ; YAJIMA; Hiroyoshi; (Kanagawa, JP) ;
TAKIMOTO; Shinichi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OLYMPUS CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
OLYMPUS CORPORATION
Tokyo
JP
|
Family ID: |
41254957 |
Appl. No.: |
14/030464 |
Filed: |
September 18, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12678390 |
Mar 16, 2010 |
8565861 |
|
|
PCT/JP2009/055654 |
Mar 23, 2009 |
|
|
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14030464 |
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Current U.S.
Class: |
600/476 ;
250/214LA; 600/109 |
Current CPC
Class: |
A61B 5/0084 20130101;
A61B 1/07 20130101; G01N 2021/655 20130101; A61B 5/0066 20130101;
G01N 21/6458 20130101; A61B 1/04 20130101; G01J 1/0407 20130101;
A61B 1/043 20130101; A61B 5/0073 20130101; A61B 5/0071 20130101;
A61B 5/6852 20130101; A61B 5/489 20130101; G01N 21/4795 20130101;
A61B 5/0077 20130101; A61B 5/0068 20130101; G01N 2021/653 20130101;
A61B 5/0075 20130101; G01N 2021/6484 20130101; G01N 21/65
20130101 |
Class at
Publication: |
600/476 ;
600/109; 250/214.LA |
International
Class: |
G01J 1/04 20060101
G01J001/04; A61B 1/04 20060101 A61B001/04; A61B 5/00 20060101
A61B005/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2008 |
JP |
2008-120293 |
May 2, 2008 |
JP |
2008-120331 |
Mar 4, 2009 |
JP |
2009-051172 |
Claims
1. An electromagnetic wave detection device, comprising a mode
adjustment unit adjusting a mode condition of incident multimode
electromagnetic waves; an amplification unit amplifying the
electromagnetic waves in which the mode condition has been adjusted
output from the mode adjustment unit; and a conversion unit
converting the amplified electromagnetic waves output from the
amplification unit to electrical signals, wherein the mode
adjustment unit is configured to adjust, by converting energy mode
distribution, the incident multimode electromagnetic waves to of a
mode substantially equal to an amplification spatial mode by the
amplification unit.
2. An electromagnetic wave detection device according to claim 1,
wherein the mode adjustment unit is configured to reduce the number
of spatial modes of incident electromagnetic waves.
3. An electromagnetic wave detection device according to claim 1,
wherein the mode adjustment unit is configured to vary an energy
ratio among spatial modes of incident electromagnetic waves.
4. An electromagnetic wave detection device according to claim 1,
wherein the incident electromagnetic waves are light; and the mode
adjustment unit is constituted by an optical waveguide.
5. An electromagnetic wave detection device according to claim 4,
wherein the optical waveguide is constituted by an optical
fiber.
6. An electromagnetic wave detection device according to claim 5,
wherein the optical fiber is constituted by a tapered optical
fiber.
7. An electromagnetic wave detection device according to claim 4,
wherein the optical waveguide is constituted by a refractive-index
distribution type waveguide having nonuniform refractive-index
distribution in a longitudinal direction of the optical waveguide
or configured to adjust the mode condition by applying nonuniform
stress distribution or nonuniform temperature distribution in a
longitudinal direction of the optical waveguide.
8. An electromagnetic wave detection device according to claim 1,
wherein the incident electromagnetic waves are light; and the
amplification unit is an optical fiber amplifier.
9. An electromagnetic wave detection device according to claim 8,
wherein the optical fiber amplifier is a rare-earth-doped optical
fiber amplifier.
10. An electromagnetic wave detection device according to claim 9,
wherein the rare-earth-doped optical fiber amplifier is a
rare-earth-doped fluoride optical fiber amplifier.
11. An electromagnetic wave detection device according to claim 8,
wherein the optical fiber amplifier is an optical fiber amplifier
using stimulated Raman scattering effects.
12. An electromagnetic wave detection device according to claim 1,
wherein the incident electromagnetic waves are light; and the
amplification unit is a semiconductor optical amplifier.
13. An electromagnetic wave detection device according to claim 1,
wherein the incident electromagnetic waves are light; and the
amplification unit is an optical amplifier having dye.
14. An electromagnetic wave detection device according to claim 1,
wherein the amplification unit varies a gain depending on timing of
incidence of the incident electromagnetic waves.
15. An electromagnetic wave detection device according to claim 1,
wherein the electromagnetic wave detection unit has, before the
mode adjustment unit, a collecting unit collecting the incident
electromagnetic waves and causing them to be incident on the mode
adjustment unit.
16. An electromagnetic wave detection device according to claim 1,
wherein the electromagnetic wave detection unit has, before the
mode adjustment unit, a plurality of collecting unit collecting the
incident electromagnetic waves in parallel and causing them to be
incident on the mode adjustment unit.
17. An electromagnetic wave detection device according to claim 16,
comprising a multiplex unit multiplexing a plurality of
electromagnetic waves output from the plurality of collecting unit,
wherein electromagnetic waves output from the multiplex unit are
input to the mode adjustment unit.
18. An electromagnetic wave detection device, comprising a
plurality of mode adjustment unit respectively adjusting a mode
condition of incident multimode electromagnetic waves which are
incident in parallel; a multiplex unit multiplexing a plurality of
electromagnetic waves in which the mode condition has been adjusted
output from the plurality of mode adjustment unit; an amplification
unit amplifying electromagnetic waves in which the plurality of
electromagnetic waves have been multiplexed output from the
multiplex unit; and a conversion unit converting the amplified
electromagnetic wave output from the amplification unit to
electrical signals, wherein the mode adjustment unit is configured
to adjust, by converting energy mode distribution, the incident
multimode electromagnetic waves to of a mode substantially equal to
an amplification spatial mode by the amplification unit.
19. An electromagnetic wave detection device, comprising a
plurality of mode adjustment unit respectively adjusting a mode
condition of incident multimode electromagnetic waves which are
incident in parallel; a plurality of amplification unit amplifying
the plurality of electromagnetic waves in which the mode condition
has been adjusted output from each of the mode adjustment unit; and
a parallel conversion unit converting the plurality of amplified
electromagnetic waves output from each of the plurality of
amplification unit to electrical signals in parallel, wherein the
mode adjustment unit is configured to adjust, by converting energy
mode distribution, the incident multimode electromagnetic waves to
of a mode substantially equal to an amplification spatial mode by
the amplification unit.
20. An electromagnetic wave detection method, comprising a mode
adjustment step for adjusting a mode condition of incident
multimode electromagnetic waves; an amplification step for
amplifying the electromagnetic waves in which the mode condition
has been adjusted; and a conversion step for converting the
amplified electromagnetic waves to electrical signals, wherein the
adjustment step adjusts, by converting energy mode distribution,
the incident multimode electromagnetic waves to of a mode
substantially equal to an amplification spatial mode in the
amplification step.
21. An organism observation method, comprising an irradiation step
for irradiating an organism with electromagnetic waves; and a
detection step for detecting, with the electromagnetic wave
detection device according claim 16, electromagnetic waves to be
detected obtained from the organism through irradiation with the
electromagnetic waves, wherein the organism is observed based on
electrical signals obtained in the detection step.
22. A microscope detecting electromagnetic waves to be detected
from an object to be observed, comprising the electromagnetic wave
detection device according to claim 16, wherein the electromagnetic
wave detection device is configured to detect the electromagnetic
waves to be detected from the object to be observed.
23. An endoscope detecting electromagnetic waves to be detected
from a body cavity and observing the inside of the body cavity,
comprising the electromagnetic wave detection device according to
claim 16, wherein the electromagnetic wave detection device is
configured to detect the electromagnetic waves to be detected from
the body cavity.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional Application of U.S. Ser.
No. 12/678,390 filed on Mar. 16, 2010, which is a national stage
application of PCT/JP2009/55654 filed on Mar. 23, 2009, which
claims the benefit of priority to JP 2008-120331 filed on May 2,
2008; JP 2008-120293 filed on May 2, 2008 and JP 2009-051172 filed
on Mar. 4, 2009, the contents of each of which are incorporated
herein by reference.
TECHNICAL FIELD
[0002] This invention relates to an optical inspection device, an
electromagnetic wave detection method, an organism observation
method, a microscope, an endoscope and the like. Furthermore, this
invention relates to an optical tomographic image generation device
irradiating an object to be inspected with light whose wavelength
varies with time to generate a tomographic image of the object to
be inspected.
BACKGROUND ART
[0003] Generally, in various systems using light such as image
observation, a sensor, security, laser radar and the like, the
technique of detecting desired light is a fundamental and important
element significantly influencing their performance. In particular,
the needs for the detection technique with high speed and high
sensitivity are high.
[0004] For example, there has been traditionally and widely used an
optical inspection method in which an organism is irradiated with
light and then the transmitted light, reflected light or scattered
light is detected to extract in vivo information from such detected
signal light. In particular, the optical imaging technique,
two-dimensionally scanning a region to be inspected with light and
displaying information of obtained signal light as an image,
contributes greatly to the field of medicine.
[0005] Moreover, in accordance with the development of laser
technique, there are recently being active the biological or
medical studies using laser scanning-type imaging such as a laser
scanning-type microscope, a laser scanning-type microscopic
endoscope or the like. In particular, the laser scanning-type
fluorescent imaging method enables serial observation of living
cells at a high signal-to-noise ratio, thus being an essential tool
for biological or medical studies. Among such methods, the
multiphoton fluorescent imaging method using multiphoton excitation
when obtaining fluorescence enables observation of deep portion of
an organism, thus drawing attention as a new fluorescent imaging
method (see Non-Patent Documents 1, 2, for example).
[0006] Moreover, there is getting active the research development
of a laser scanning-type imaging method using nonlinear optical
effects in organisms such as Coherent anti-Stokes Raman Scattering
(CARS) imaging (see Non-Patent Document 3, for example),
high-frequency generating imaging (see Non-Patent Document 4) or
the like. Since the laser scanning imaging method using the
nonlinear optical effects does not require dyeing of a sample to be
observed with fluorescent substances such as fluorescent protein,
fluorescent dye or the like, the method has an advantage, as
compared with the fluorescent imaging method, that the true state
of organisms can be observed.
[0007] In this connection, in the optical imaging for organisms
including the laser scanning-type imaging, optical signals obtained
from an organism sample are usually weak due to influences by light
scattering effects and light absorbing effects in the organism
sample, or the like. Particularly in the imaging method using
nonlinear optical effects such as the multiphoton fluorescent
imaging, the CARS imaging or the like, the conversion efficiency
from excitation light to signal light is essentially low, and thus
the optical signals obtained from an organism are significantly
weak. Therefore, it is difficult to obtain a clear image.
[0008] As a method of solving this problem, it is conceivable that
the intensity of excitation light with which an organism is
irradiated is rendered to be higher. However, when an organism is
irradiated with light having excessively high intensity, it could
be possible to damage the organism. Thus, the intensity of
excitation light has an upper limit Therefore, it is difficult to
obtain a clear image in lots of cases.
[0009] Then, it is general that a low-noise high-sensitivity
photodetector is used to obtain a clearer image.
[0010] As the currently-used typical photodetection device, there
can be mentioned PMT (Photo multiplier tube), APD (Avalanche photo
diode) and PD (Photo diode). The PMT and the APD perform electron
multiplying in the detection device, which enables high-sensitive
photodetection. On the other hand, the PD does not have an electron
multiplying function in the detection device and thus signals are
usually amplified with the use of an electric amplifier, although
it achieves a very high response speed. That is, any devices of
PMT, APD and PD perform signal amplification in an electric domain
to improve the sensitivity.
[0011] Moreover, there can be mentioned, as the typical
two-dimensional photodetectors, CCD (Charged coupled device), CMOS
(complementary metal Oxide semiconductor), EM-CCD (Electron
multiplying-CCD), EB-CCD (Electron bombardment-CCD) and I-CCD
(Intensified-CCD). When weak light is detected using the CCD or the
CMOS, it is necessary, like the PD, to dispose an electric
amplifier in a subsequent part so as to improve the sensitivity.
The EM-CCD and the EB-CCD have an electron multiplying function in
the detection device, like the APD, and achieve the higher
sensitivity. The I-CCD has a configuration in which an Image
intensifier (hereinafter referred to as I.I.) is disposed before
the CCD. In the LI, incident light signals are converted to
electrical signals once, and electron multiplying is performed in a
MCP (Micro channel plate) embedded in the LI., thereafter the
multiplied electrons are rendered to collide with a fluorescent
plate so that the multiplied electrical signals are converted to
light again. That is, the I-CCD also performs signal multiplying in
an electric domain, achieving high-sensitive photodetection.
[0012] However, the low-noise and high-sensitivity photodetector is
of particular and very expensive. Moreover, in the above
conventional photodetection technique using signal amplification in
an electric domain, the volume of noises generated from a
photodetector and accumulated time of signal light by the
photodetector have the inverse relationship, that is, the trade-off
relationship therebetween, which requires sufficiently long
accumulated time to obtain low-noise detection signals. As a
result, sufficiently long accumulated time is needed to obtain a
clear image after detecting weak signal light, thus extending time
for obtaining an image. Therefore, real-time properties lack for
needs to properly observe an organism varying with time, and it
could be possible to inhibit basic needs by optical imaging users.
Therefore, it is unavoidable in the present situation that either
of detection speed or detection sensitivity is sacrificed to
perform photodetection.
[0013] It is noted that such problem occurs not only in optical
imaging methods but also in optical measuring methods such as the
flow site meter optically analyzing fine particles in fluid, the
fluorescence correlation spectroscopy (FCS) optically analyzing
motion of fluorescently-labeled biomolecules in solution, the
surface plasmon resonance method (SPR) optically analyzing the
state of connection among biologically-relevant molecules fixed on
the surface of a solid substrate and the latex photometric
immunoassay (LPIA) optically analyzing the state of connection
among biologically-relevant molecules in solution and the
fluoroimmunoassay (FIA) detecting immune response in solution based
on the existence or nonexistence of fluorescent label.
[0014] On the other hand, it has been conventionally active in
development of the optical amplifier using optical fibers as the
light transmission means mainly in the field of long-distance
optical communication. As compared with the electric amplifier, the
optical amplifier is capable of very high-speed wide-bandwidth
operation and has properties, depending on the configuration,
capable of low-noise and high-gain optical amplification. Such an
optical amplifier is disposed before a high-speed photoelectric
conversion device, thereby high-speed and high-sensitive
photodetection can be expected (see Patent Document 1, for
example).
[0015] The summary of Patent Document 1 is that optical irradiation
is conducted by one of two optical fibers disposed at a given angle
and the other performs photodetection, thereby the axial resolution
in a depth direction of an object to be observed is improved.
[0016] Moreover, Amplified spontaneous emission (ASE) is generated
from the optical amplifier, which is a dominant cause of noises in
photodetection using the optical amplifier. Therefore, for
achieving high-speed and high-sensitive photodetection using the
optical amplifier, it is necessary that the optical amplifier is of
low noise. With respect to the optical amplifier, as the light
intensity of input signals becomes higher, the signal to noise
ratio (hereinafter referred to as the SNR) after optical
amplification is improved and thus the photodetection sensitivity
is improved.
[0017] Moreover, a low-noise optical amplifier used in the field of
long-distance optical communication is constituted by a single-mode
optical fiber. The reasons why such a constitution by single-mode
optical fiber is used are because the consistency with a
transmission path is excellent and noises of the optical amplifier
increase in proportion to a transmission mode of a gain fiber
constituting the optical amplifier. Thus, in the field of
long-distance optical communication, the use of a single-mode
optical fiber as a gain fiber contributes greatly to low-noise
properties of the optical amplifier.
[0018] However, even such a low-noise optical amplifier for
long-distance optical communication constituted by a single-mode
optical fiber has the following problem when used before a
photoelectric conversion device. That is, it is often the case that
signal light detected in the fields of organism observation, a
sensor, security, laser radar and the like is scattered light or
light with distorted wavefront. Such light has significantly low
coupling efficiency to a single-mode optical fiber, and the light
signal which can be taken in the optical amplifier is weak signals
being of limited one portion of the whole. Therefore, the SNR is
deteriorated and thus the high light-receiving sensitivity cannot
be obtained.
[0019] On the other hand, it is conceivable that a multimode
optical fiber amplifier having a large core diameter is disposed
just before the photoelectric conversion device since it collects
scattered light and light with distorted wavefront with high
efficiency. However, since optical noises generated in the optical
amplifier increase in accordance with the increase of the number of
spatial modes resulted by increasing the core diameter, the SNR
deteriorates in this case also and thus the high light-receiving
sensitivity cannot be obtained.
[0020] Although the above is described with an example of a case in
which light is detected, it is conceivable that cases in which
electromagnetic waves other than light such as millimeter waves,
microwaves and the like are detected also have the same
problem.
[0021] On the other hand, there is conventionally known the
organism tomographic image measuring technique using light referred
as Optical coherence tomography (OCT) (see Non-Patent Document 5,
for example). The OCT technique makes it possible to measure a
tomographic image of an organism at a depth position of 1 mm to 2
mm, at resolution of about 1 .mu.m to 10 .mu.m.
[0022] The OCT technique is divided mainly to three methods of
Time-domain (TD) OCT, Frequency-domain (FD) OCT (see Non-Patent
Document 6, for example) and Swept source (SS) OCT (see Non-Patent
Document 7, for example). Among them, the SSOCT using light whose
wavelength varies with time enables measurement of an organism
tomographic image at highest-speed and with highest-sensitivity,
and the technical development thereof is being actively
advanced.
[0023] However, the penetration depth of tomographic images
obtained by OCT is presently about only 1 to 2 mm, and thus the
performance is insufficient in diagnosis of penetration of cancer
which is essential for early detection thereof. Thus, the applied
range is limited.
[0024] The reason why the penetration depth by OCT is not improved
is because optical signals returning from the deep portion of the
organism to the surface thereof are weak due to light scattering
effects or light absorbing effects in the organism and thus the
signals from the deep portion are buried in noises such as shot
noises, thermal noises, quantization noises and the like which are
generated in the detection process. Particularly in the case of
SSOCT, quantization noises (quantization errors) in an
analog-digital converter (ADC) are the cause of limiting the
penetration depth.
[0025] That is, in the SSOCT, analog signals after photoelectric
conversion are of high frequency in a deep portion of an organism
and of low frequency in a shallow portion thereof, and the signal
from a shallow portion of the organism usually has higher intensity
by several orders of magnitude than that from a deep portion
thereof. Therefore, when such a signal is quantized by the ADC,
high-frequency components with small amplitude having information
from the deep portion of the organism are buried in quantization
noises and information from the deep portion cannot be taken out
even when an ADC having a relatively wide dynamic range of 14 bits
is used, for example.
[0026] Patent Document 1: U.S. Pat. No. 6,423,956
[0027] Non Patent Document 1: W. Denk et al., Science 248, 73
(1990)
[0028] Non Patent Document 2: J. Jung and M. J. Schnitzer, Opt.
Lett. 28, 902 (2003)
[0029] Non Patent Document 3: A. Zumbusch et al., Phys. Rev. Lett.
82, 4142 (1999)
[0030] Non Patent Document 4: I. Freund et al., Biophys. J. 50, 693
(1986)
[0031] Non Patent Document 5: D. Huang et al., Science 254,1178
(1991)
[0032] Non Patent Document 6: R. Leitgeb et al., Opt.Lett. 25,820
(2000)
[0033] Non Patent Document 7: S. R. Chinn et al., Opt.Lett. 22,340
(1997)
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0034] Therefore, an object of the invention in view of the above
aspects is to provide an optical inspection device capable of
collecting low-noise detection signals with high efficiency with
its inexpensive configuration even when signals to be detected
transmitted from an object are weak without increasing the
intensity of light with which the object to be observed is
irradiated and without using an expensive low-noise and
high-sensitivity photodetector. Moreover, an object of the
invention is to provide an electromagnetic wave detection method,
an electromagnetic wave detection device, and an organism
observation method, a microscope and an endoscope capable of
detecting electromagnetic waves at high speed and with high
sensitivity even when the electromagnetic waves to be detected
(signals to be detected) are scattered electromagnetic waves or
electromagnetic waves with distorted wavefront due to an organism
and the like.
[0035] Furthermore, an object of the invention is to provide an
optical tomographic image generation device capable of converting
information from a deep portion of an object to be inspected by
SSOCT to digital signals with high accuracy without burying the
information in quantization noises and of improving the penetration
depth of a tomographic image.
SUMMARY OF THE INVENTION
[0036] The invention is based on a fundamental configuration in
which detected signals or detected electromagnetic waves are
amplified not in an electric domain but by a light amplification
means or an electromagnetic wave amplification means before
converting such signals from light or electromagnetic waves to
electrical signals. Moreover, in a plurality of aspects of the
invention, a mode adjustment means is provided before the
amplification means to render the signal mode of detected signals
or detected electromagnetic waves to be substantially equal to the
amplification spatial mode of the amplification means. Furthermore,
other plurality of aspects of the invention, the configuration of
the optical inspection device using the light amplification means
of the application is applied in an optical tomographic image
generation device. The method for solving problems according to
each aspect of the application will be described.
[0037] A first aspect of the invention relating to an optical
inspection device for achieving the above object is an optical
inspection device, comprising a light generation means, a light
irradiation means irradiating an object to be inspected with light
generated from the light generation means and a photodetection
means photoelectrically converting signal light obtained from the
object to be inspected through irradiation of light by the light
irradiation means, and inspecting the object to be inspected based
on output from the photodetection means,
[0038] wherein a light amplification means amplifying signal light
obtained from the object to be inspected is provided.
[0039] A second aspect of the invention is an optical inspection
device according to the first aspect, wherein the light
amplification means comprises a waveguide-type optical
amplifier.
[0040] A third aspect of the invention is an optical inspection
device according to the second aspect, wherein the waveguide-type
optical amplifier is constituted by a semiconductor optical
amplifier.
[0041] A fourth aspect of the invention is an optical inspection
device according to the second aspect, wherein the waveguide-type
optical amplifier is constituted by an optical fiber amplifier.
[0042] A fifth aspect of the invention is an optical inspection
device according to any one of the first to fourth aspects, wherein
the light amplification means amplifies, as the signal light, light
having a wavelength different from that of light with which the
object to be inspected is irradiated.
[0043] A sixth aspect of the invention is an optical inspection
device according to the fifth aspect, wherein the light
amplification means amplifies, as the signal light, fluorescence or
phosphorescence generated from the object to be inspected.
[0044] A seventh aspect of the invention is an optical inspection
device according to the fifth aspect, wherein the light
amplification means amplifies, as the signal light, light generated
by nonlinear optical effects in the object to be inspected.
[0045] An eighth aspect of the invention is an optical inspection
device according to any one of the first to seventh aspects,
comprising a gain control means controlling a gain of the light
amplification means in synchronization with timing of incidence of
the signal light on the light amplification means.
[0046] A ninth aspect of the invention is an optical inspection
device according to any one of the first to eighth aspects, wherein
the light amplification means is configured so that a wavelength
region of light to be amplified is narrower than that of light to
be incident.
[0047] A tenth aspect of the invention is an optical inspection
device according to any one of the first to ninth aspects, wherein
a back reflection prevention means preventing back reflection from
the light amplification means to the object to be inspected is
provided at the input side of the light amplification means.
[0048] An eleventh aspect of the invention is an optical inspection
device according to any one of the first to tenth aspects, wherein
a wavelength selection means selecting a wavelength of signal light
to be photoelectrically converted by the photodetection means is
provided between the light amplification means and the
photodetection means.
[0049] A twelfth aspect of the invention is an optical inspection
device according to any one of the first to eleventh aspects,
comprising an optical system connecting the object to be inspected
with the light amplification means in optical conjugation.
[0050] A thirteenth aspect of the invention is an optical
inspection device according to any one of the first to twelfth
aspects, wherein the object to be inspected is an organism; and the
light amplification means amplifies, as the signal light, light
modulated by the organism.
[0051] A fourteenth aspect of the invention is an optical
inspection device according to any one of the first to thirteenth
aspects, wherein the light generation means generates laser
light.
[0052] A fifteenth aspect of the invention is an optical inspection
device according to any one of the first to fourteenth aspects,
comprising an image display means displaying an image based on
output from the photodetection means,
[0053] wherein the light irradiation means comprises a light scan
means scanning with light with which the object to be inspected is
irradiated in at least two-dimensional direction; and
[0054] an image of an area of the object to be inspected scanned by
the light scan means is displayed on the image display means based
on output from the photodetection means.
[0055] A sixteenth aspect of the invention relating to an
electromagnetic wave detection device for achieving the above
object is an electromagnetic wave detection device, comprising
[0056] a mode adjustment means adjusting a mode condition of
incident multimode electromagnetic waves;
[0057] an amplification means amplifying the electromagnetic waves
in which the mode condition has been adjusted output from the mode
adjustment means; and
[0058] a conversion means converting the amplified electromagnetic
waves output from the amplification means to electrical
signals,
[0059] wherein the mode adjustment means is configured to adjust,
by converting energy mode distribution, the incident multimode
electromagnetic waves to of a mode substantially equal to an
amplification spatial mode by the amplification means.
[0060] A seventeenth aspect of the invention is an electromagnetic
wave detection device according to the sixteenth aspect, wherein
the mode adjustment means is configured to reduce the number of
spatial modes of incident electromagnetic waves.
[0061] A eighteenth aspect of the invention is an electromagnetic
wave detection device according to the sixteenth aspect, wherein
the mode adjustment means is configured to vary an energy ratio
among spatial modes of incident electromagnetic waves.
[0062] A nineteenth aspect of the invention is an electromagnetic
wave detection device according to the sixteenth aspect, wherein
the incident electromagnetic waves are light; and the mode
adjustment means is constituted by an optical waveguide.
[0063] A twentieth aspect of the invention is an electromagnetic
wave detection device according to the nineteenth aspect, wherein
the optical waveguide is constituted by an optical fiber.
[0064] A twenty-first aspect of the invention is an electromagnetic
wave detection device according to the twentieth aspect, wherein
the optical fiber is constituted by a tapered optical fiber.
[0065] A twenty-second aspect of the invention is an
electromagnetic wave detection device according to the nineteenth
aspect, wherein the optical waveguide is constituted by a
refractive-index distribution type waveguide having nonuniform
refractive-index distribution in a longitudinal direction of the
optical waveguide or configured to adjust the mode condition by
applying nonuniform stress distribution or nonuniform temperature
distribution in a longitudinal direction of the optical
waveguide.
[0066] A twenty-third aspect of the invention is an electromagnetic
wave detection device according to the sixteenth aspect, wherein
the incident electromagnetic waves are light; and the amplification
means is an optical fiber amplifier.
[0067] A twenty-fourth aspect of the invention is an
electromagnetic wave detection device according to the twenty-third
aspect, wherein the optical fiber amplifier is a rare-earth-doped
optical fiber amplifier.
[0068] A twenty-fifth aspect of the invention is an electromagnetic
wave detection device according to the twenty-fourth aspect,
wherein the rare-earth-doped optical fiber amplifier is a
rare-earth-doped fluoride optical fiber amplifier.
[0069] A twenty-sixth aspect of the invention is an electromagnetic
wave detection device according to the twenty-third aspect, wherein
the optical fiber amplifier is an optical fiber amplifier using
stimulated Raman scattering effects.
[0070] A twenty-seventh aspect of the invention is an
electromagnetic wave detection device according to the sixteenth
aspect, wherein the incident electromagnetic waves are light; and
the amplification means is a semiconductor optical amplifier.
[0071] A twenty-eighth aspect of the invention is an
electromagnetic wave detection device according to the sixteenth
aspect, wherein the incident electromagnetic waves are light; and
the amplification means is an optical amplifier having dye.
[0072] A twenty-ninth aspect of the invention is an electromagnetic
wave detection device according to the sixteenth aspect, wherein
the amplification means varies a gain depending on timing of
incidence of the incident electromagnetic waves.
[0073] A thirtieth aspect of the invention is an electromagnetic
wave detection device according to the sixteenth aspect, wherein
the electromagnetic wave detection means has, before the mode
adjustment means, a collecting means collecting the incident
electromagnetic waves and causing them to be incident on the mode
adjustment means.
[0074] A thirty-first aspect of the invention is an electromagnetic
wave detection device according to the sixteenth aspect, wherein
the electromagnetic wave detection means has, before the mode
adjustment means, a plurality of collecting means collecting the
incident electromagnetic waves in parallel and causing them to be
incident on the mode adjustment means.
[0075] A thirty-second aspect of the invention is an
electromagnetic wave detection device according to the thirty-first
aspect, comprising a multiplex means multiplexing a plurality of
electromagnetic waves output from the plurality of collecting
means, wherein electromagnetic waves output from the multiplex
means are input to the mode adjustment means.
[0076] A thirty-third aspect of the invention relating to an
electromagnetic wave detection device for achieving the above
object is an electromagnetic wave detection device, comprising
[0077] a plurality of mode adjustment means respectively adjusting
a mode condition of incident multimode electromagnetic waves which
are incident in parallel;
[0078] a multiplex means multiplexing a plurality of
electromagnetic waves in which the mode condition has been adjusted
output from the plurality of mode adjustment means;
[0079] an amplification means amplifying electromagnetic waves in
which the plurality of electromagnetic waves have been multiplexed
output from the multiplex means; and
[0080] a conversion means converting the amplified electromagnetic
wave output from the amplification means to electrical signals,
[0081] wherein the mode adjustment means is configured to adjust,
by converting energy mode distribution, the incident multimode
electromagnetic waves to of a mode substantially equal to an
amplification spatial mode by the amplification means.
[0082] A thirty-fourth aspect of the invention relating to an
electromagnetic wave detection device for achieving the above
object is an electromagnetic wave detection device, comprising
[0083] a plurality of mode adjustment means respectively adjusting
a mode condition of incident multimode electromagnetic waves which
are incident in parallel;
[0084] a plurality of amplification means amplifying the plurality
of electromagnetic waves in which the mode condition has been
adjusted output from each of the mode adjustment means; and
[0085] a parallel conversion means converting the plurality of
amplified electromagnetic waves output from each of the plurality
of amplification means to electrical signals in parallel,
[0086] wherein the mode adjustment means is configured to adjust,
by converting energy mode distribution, the incident multimode
electromagnetic waves to of a mode substantially equal to an
amplification spatial mode by the amplification means.
[0087] A thirty-fifth aspect of the invention relating to an
electromagnetic wave detection method for achieving the above
object is an electromagnetic wave detection method, comprising
[0088] a mode adjustment step for adjusting a mode condition of
incident multimode electromagnetic waves;
[0089] an amplification step for amplifying the electromagnetic
waves in which the mode condition has been adjusted; and
[0090] a conversion step for converting the amplified
electromagnetic waves to electrical signals,
[0091] wherein the adjustment step adjusts, by converting energy
mode distribution, the incident multimode electromagnetic waves to
of a mode substantially equal to an amplification spatial mode in
the amplification step.
[0092] A thirty-sixth aspect of the invention relating to an
organism observation method for achieving the above object is an
organism observation method, comprising
[0093] an irradiation step for irradiating an organism with
electromagnetic waves; and
[0094] a detection step for detecting, with the electromagnetic
wave detection device according to any one of claims 16 to 35,
electromagnetic waves to be detected obtained from the organism
through irradiation with the electromagnetic waves,
[0095] wherein the organism is observed based on electrical signals
obtained in the detection step.
[0096] A thirty-seventh aspect of the invention relating to a
microscope for achieving the above object is a microscope detecting
electromagnetic waves to be detected from an object to be observed,
comprising the electromagnetic wave detection device according to
any one of claims 16 to 35,
[0097] wherein the electromagnetic wave detection device is
configured to detect the electromagnetic waves to be detected from
the object to be observed.
[0098] A thirty-eighth aspect of the invention relating to an
endoscope for achieving the above object is an endoscope detecting
electromagnetic waves to be detected from a body cavity and
observing the inside of the body cavity, comprising the
electromagnetic wave detection device according to any one of
claims 16 to 35,
[0099] wherein the electromagnetic wave detection device is
configured to detect the electromagnetic waves to be detected from
the body cavity.
[0100] A thirty-ninth aspect of the invention is an optical
inspection device according to the first aspect, comprising
[0101] an optical multiplex-demultiplex unit demultiplexing light
from the light generation means to inspection light and reference
light so that the object to be inspected is irradiated with the
inspection light by the light irradiation means and the reference
light is guided to a light reflection unit, amplifying, by the
light amplification means, reflected inspection light obtained in a
way that the inspection light is reflected and scattered by the
object to be inspected, and multiplexing the amplified reflected
inspection light and reflected reference light obtained in a way
that the reference light is reflected by the light reflection unit
so as to generate interference light;
[0102] an analog signal process unit attenuating low-frequency
components of photoelectric conversion signals obtained from the
photodetection means relative to high-frequency components
thereof;
[0103] an analog-digital conversion unit converting analog output
signals from the analog signal process unit to digital signals;
and
[0104] an image process unit processing digital output signals from
the analog-digital conversion unit so as to generate an optical
tomographic image,
[0105] wherein the light generation means is a wavelength-variable
light source unit emitting light whose wavelength varies with time;
and
[0106] the photodetection means is a photoelectrical conversion
unit receiving interference light generated by the optical
multiplex-demultiplex unit and photoelectrically converting the
same.
[0107] A fortieth aspect of the invention is an optical inspection
device according to the thirty-ninth aspect, wherein an optical
filter removing optical noises is provided between the light
amplification means and the optical multiplex-demultiplex unit.
[0108] A forty-first aspect of the invention is an optical
inspection device according to the fortieth aspect, wherein the
optical filter is constituted by a band-pass filter in which a
transmitted central wavelength is variable; and the transmitted
central wavelength is varied in synchronization with variation with
time of wavelength of light emitted from the wavelength-variable
light source unit.
[0109] A forty-second aspect of the invention relating to an
optical tomographic image generation device for achieving the above
object is an optical tomographic image generation device comprising
the optical inspection device according to any one of claims 39 to
41.
EFFECT OF THE INVENTION
[0110] According to the invention, signal light obtained from an
object to be inspected is amplified by a light amplification means
and then photoelectrically converted by a photodetection means,
which makes it possible to photoelectically convert signal light
from the object to be inspected with high sensitivity and promptly
with its inexpensive configuration without increasing the intensity
of light with which the object to be inspected is irradiated and
without using an expensive low-noise and high-sensitivity
photodetector as the photodetection means.
BRIEF DESCRIPTION OF DRAWINGS
[0111] FIG. 1 is a functional block diagram illustrating a
fundamental configuration of the optical inspection device of the
invention.
[0112] FIG. 2 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
first embodiment of the invention.
[0113] FIG. 3 is a diagram illustrating two examples of an optical
fiber amplifier which can be used as the light amplification means
shown in FIG. 2.
[0114] FIG. 4 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
second embodiment of the invention.
[0115] FIG. 5 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
third embodiment of the invention.
[0116] FIG. 6 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
fourth embodiment of the invention.
[0117] FIG. 7 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the fifth embodiment of the invention.
[0118] FIG. 8 is a diagram explaining mode adjustment by a mode
adjustment means.
[0119] FIG. 9 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
sixth embodiment of the invention.
[0120] FIG. 10 is a diagram illustrating a schematic shape of a
longitudinal section of a core portion of a tapered fiber.
[0121] FIG. 11 is a schematic configuration diagram illustrating an
Er-doped fluoride optical fiber amplifier.
[0122] FIG. 12 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the seventh embodiment of the invention.
[0123] FIG. 13 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
eighth embodiment of the invention.
[0124] FIG. 14 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the ninth embodiment of the invention.
[0125] FIG. 15 is a diagram illustrating a schematic configuration
of the high sensitivity endoscope according to the tenth embodiment
of the invention.
[0126] FIG. 16 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the eleventh embodiment of the invention.
[0127] FIG. 17 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
twelfth embodiment of the invention.
[0128] FIG. 18 is a diagram illustrating a schematic configuration
of a laser scanning multiphoton fluorescence microscope using the
electromagnetic wave detection device according to the thirteenth
embodiment of the invention.
[0129] FIG. 19 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the fourteenth embodiment of the invention.
[0130] FIG. 20 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
fifteenth embodiment of the invention.
[0131] FIG. 21 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the sixteenth embodiment of the invention.
[0132] FIG. 22 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
seventeenth embodiment of the invention.
[0133] FIG. 23 is a functional block diagram illustrating a
fundamental configuration of the optical tomographic image
generation device according to the first reference example of the
invention.
[0134] FIG. 24 is a functional block diagram illustrating a
configuration of the optical tomographic image generation device
according to the first reference example of the invention
[0135] FIG. 25 is a functional block diagram illustrating a
configuration of the optical tomographic image generation device
according to the eighteenth embodiment of the invention.
[0136] FIG. 26 is a functional block diagram illustrating a
configuration of the optical tomographic image generation device
according to the nineteenth embodiment of the invention.
REFERENCE SYMBOLS
[0137] 1 optical inspection device [0138] 2 light generation means
[0139] 3 light irradiation means [0140] 4 object to be inspected
[0141] 5 light amplification means [0142] 6 photodetection means
[0143] 11 fat [0144] 12 blood vessel [0145] 15 movable table [0146]
16 projector lens [0147] 17 collective lens [0148] 21 computer
[0149] 22 movable table control device [0150] 25 single-mode
optical fiber [0151] 26 laser diode (LD) [0152] 27 function
generator [0153] 28 LD driver [0154] 31 multimode optical fiber
[0155] 32 light amplification means [0156] 33 band-pass filter
[0157] 34 photodetection means [0158] 35 transimpedance amplifier
[0159] 36 lock-in amplifier [0160] 37 analog-digital (A/D)
converter [0161] 38 monitor [0162] 41 excitation light source
[0163] 42 multiplex device [0164] 43 rare-earth-doped optical fiber
[0165] 44 excitation light removal device [0166] 45 optical
isolator [0167] 46 optical isolator [0168] 47 Silica optical fiber
[0169] 51 laser scanning confocal fluorescence microscope [0170] 52
He--Ne laser [0171] 53 light intensity adjustment device [0172] 54
dichroic mirror [0173] 55 X-Y galvano scanner mirror [0174] 56
pupil lens [0175] 57 tube lens [0176] 58 objective lens [0177] 60
living cell sample [0178] 61 optical isolator [0179] 62 collective
lens [0180] 63 light amplification means [0181] 64 photomultiplier
tube [0182] 65 computer [0183] 66 monitor [0184] 71 laser scanning
multiphoton fluorescence microscope [0185] 72 Titanium-sapphire
laser [0186] 73 gain control means [0187] 81 laser scanning CARS
microscope [0188] 82 two-wavelength optical pulse source [0189] 83
living cell sample [0190] 84 band-pass filter [0191] 110 mode
adjustment means [0192] 111 tapered fiber [0193] 111a core portion
of tapered fiber [0194] 112 tapered waveguide [0195] 120
amplification means [0196] 121 Er-doped fluoride optical fiber
amplifier [0197] 122 semiconductor optical amplifier (SOA) [0198]
123 semiconductor optical amplifier (SOA) [0199] 130 conversion
means [0200] 131 PIN-PD [0201] 132 CCD camera [0202] 133 PIN-PD
[0203] 140 multiplex means [0204] 141 fiber coupler [0205] 142
multimode fiber coupler [0206] 150 collecting means [0207] 151
collective lens [0208] 152 collective lens [0209] 161 Er-doped
fluoride fiber laser [0210] 162 isolator [0211] 163 SMF [0212] 164a
collimator [0213] 164b lens for lighting [0214] 165 scan mount
[0215] 166 laser driver [0216] 167 electric amplifier [0217] 168 AD
converter [0218] 169 computer [0219] 170 display monitor [0220] 171
driver [0221] 172 driver [0222] 173a isolator [0223] 173b isolator
[0224] 174 WDM coupler [0225] 175 Er-doped fluoride fiber [0226]
176 optical filter [0227] 177 LD [0228] 178 housing [0229] 179
laser driver [0230] 180 LD [0231] 181 isolator [0232] 182a MMF
[0233] 182b MMF [0234] 183 lens for lighting [0235] 184a isolator
[0236] 184b isolator [0237] 185 BPF [0238] 186 driver [0239] 187
Titanium-sapphire laser [0240] 188 light intensity adjustment
device [0241] 189 X-Y galvano scanner mirror [0242] 190 pupil lens
[0243] 191 tube lens [0244] 192 dichroic mirror [0245] 193
objective lens [0246] 200 organism sample [0247] 201 living cell
sample [0248] 202 isolator [0249] 203 gain control means [0250] 301
wavelength-variable light source unit [0251] 302 image process unit
[0252] 303 wavelength control unit [0253] 305 optical
multiplex-demultiplex unit [0254] 306 reference-side optical
transmission unit [0255] 307 inspection-side optical transmission
unit [0256] 308 lens [0257] 309 light reflection unit [0258] 310
lens [0259] 311 object to be inspected [0260] 312 photoelectric
conversion unit [0261] 313 analog signal process unit [0262] 314
analog-digital (A/D) conversion unit [0263] 315 display unit [0264]
321 frequency domain mode synchronization laser (FDML) [0265] 322
image process unit [0266] 323 filter control unit [0267] 324
optical circulator [0268] 325 3 dB coupler [0269] 326 single-mode
optical fiber (SMF) [0270] 327 polarization controller [0271] 328
lens [0272] 329 optical attenuator [0273] 330 reflective mirror
[0274] 331 single-mode optical fiber (SMF) [0275] 332 lens [0276]
333 galvano scanner mirror [0277] 334 lens [0278] 335 object to be
inspected [0279] 336 scanner driver [0280] 337 dual-balanced
receiver [0281] 338 highpass filter (HPF) [0282] 339 amplifier
[0283] 340 A/D conversion unit [0284] 341 monitor [0285] 345 3 dB
coupler [0286] 346 3 dB coupler [0287] 347 optical circulator
[0288] 348 optical circulator [0289] 351 optical amplifier [0290]
352 optical band-pass filter (BPF) [0291] 353 filter control
unit
BEST MODE FOR CARRYING OUT THE INVENTION
[0292] First, before explaining embodiments of the invention, the
fundamental configuration of the optical inspection device of the
invention will be described.
[0293] FIG. 1 is a functional block diagram illustrating a
fundamental configuration of the optical inspection device of the
invention. The optical inspection device 1 has a light generation
means 2, a light irradiation means 3, a light amplification means 5
and a photodetection means 6. The light generation means 2
generates light for obtaining signal light from an object to be
inspected, and generates light having a given wavelength or light
having a given wavelength region according to a type of inspection.
The light irradiation means 3 irradiates an object to be inspected
4 with the light generated by the light generation means 2, thereby
signal light is generated from the object to be inspected 4. Here,
the signal light generated from the object to be inspected 4
through light irradiation therefor is transmitted light or
reflected light of irradiated light, fluorescence or
phosphorescence generated through excitation by irradiated light,
or light generated by nonlinear optical effects, for example,
according to a type of inspection.
[0294] The light amplification means 5 inputs signal light
according to a type of inspection obtained from the object to be
inspected 4, amplifies the input signal light and outputs it to the
photodetection means 6. The photodetection means 6 receives the
signal light amplified by the light amplification means 5 and
photoelectrically converts it. The electrical signals
photoelectrically converted by the photodetection means 6 are
processed according to a type of inspection at a signal processing
circuit which is not shown, thereby the object to be inspected is
inspected.
[0295] As above, signal light obtained from the object to be
inspected 4 is amplified by the light amplification means 5 and
then photoelectrically converted by the photodetection means 6,
which makes it possible to photoelectrically convert signal light
with high sensitivity and promptly without increasing the intensity
of light with which the object to be inspected 4 is irradiated and
without using an expensive low-noise high-sensitivity photodetector
even when signal light obtained from the object to be inspected 4
is weak.
[0296] Next, embodiments of the invention will be described with
reference to the accompanying drawings.
First Embodiment
[0297] FIG. 2 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
first embodiment of the invention. The optical inspection device is
a device for visualizing a route condition of a blood vessel 12
buried in fat 11 when a rigid endoscope is inserted to the inside
of a body to approach organs like a stomach covered by fat. The
device enables the scope-assisted surgery with avoiding bleeding
due to wrong cutting of the blood vessel 12.
[0298] For this reason, the optical inspection device shown in FIG.
2 is provided, at a distal insertion portion of a rigid endoscope
which is not shown, with a movable table 15 which can be moved in
two-dimensional direction in a plane perpendicular to an insertion
direction, and the movable table 15 is provided with a projector
lens 16 for irradiating the object to be inspected with light and a
collective lens 17 for collecting signal light from the object to
be inspected at intervals of about 10 mm, for example. The computer
21 drives the movable table 15 in two-dimensional direction through
a movable table control device 22 so that the movable table 15
scans with light with which the object to be inspected is
irradiated.
[0299] Therefore, in the embodiment, the movable table 15, the
computer 21 and the movable table control device 22 constitute the
light scan means.
[0300] The projector lens 16 is connected to a laser diode (LD) 26
as the light generation means via a single-mode optical fiber 25.
As the laser diode 26, there is used one generating light having
output of 50 mW, a spectral width of 1 nm and a central wavelength
of 980 nm, for example. It is noted that light having a wavelength
of 980 nm is low in optical absorptance at fat 11 of an organism
and high in optical absorptance at hemoglobin in erythrocytes. An
LD driver 28 drives the laser diode 26 based on sinusoidal
modulation signals having a frequency of fm from a function
generator 27. Thus, the laser diode 26 generates light
intensity-modulated at a frequency of fm, and the
intensity-modulated light is guided to the projector lens 16 via
the single-mode optical fiber 25 to be rendered to a parallel beam
by the projector lens 16, with which an organism is irradiated. In
the optical inspection device, therefore, the single-mode optical
fiber 25 and the projector lens 16 constitute the light irradiation
means.
[0301] The light with which an organism is irradiated through the
projector lens 16 is transmitted, reflected or scattered in fat 11,
and when the blood vessel 12 runs in the fat 11, the light is
absorbed by erythrocytes flowing therein and amplitude-modulated.
As above, an organism is irradiated with light from the laser diode
26, thereby signal light obtained from the organism is collected by
the collective lens 17 and the collected signal light is amplified
by a light amplification means 32 via a multimode optical fiber 31.
In the embodiment, the light amplification means 32 uses a
waveguide-type optical amplifier such as a semiconductor optical
amplifier, an optical fiber amplifier or the like, and is
configured so as to have an amplification band of 3 nm and a gain
of about 13 dB in a band having a wavelength of 980 nm, thereby the
optical power of the received signal light is amplified to of about
20 times and the light is output.
[0302] The signal light amplified by the light amplification means
32 is received by a photodetection means (PD) 34 via a band-pass
filter 33 and photoelectrically converted. As the band-pass filter
33, there is used of dielectric-multilayer-type having a central
wavelength of 980 nm and a passband width of about 1 nm, for
example. As a photodetection means 34, InGaAs/PIN photodiode is
used, for example.
[0303] Outputs photoelectrically converted by the photodetection
means 34 are converted to electric voltage by a transimpedance
amplifier 35 and input in a lock-in amplifier 36. With sinusoidal
modulation signals having a frequency of fm from the function
generator 27 as reference signals, the lock-in amplifier 36
extracts voltage signals synthesized with the reference signals
from input voltage signals from the transimpedance amplifier 35,
The analog output signals extracted by the lock-in amplifier 36 are
converted to digital signals by an analog-digital (A/D) converter
37 and provided to the computer 21.
[0304] The computer 21 processes digital signals of each point of
an organism obtained from the A/D converter 37 through optical
scanning by two-dimensional driving of the movable table 15, and
displays an image on a monitor 38.
[0305] According to the embodiment, signal light from an organism
collected by the collective lens 17 is amplified by the light
amplification means 32 via the multimode optical fiber 31 and then
photoelectrically converted by the photodetection means 34, which
makes it possible to photoelectrically convert signal light with
high sensitivity and promptly with constituting the photodetection
means 34 by an inexpensive photodetector without increasing outputs
of the laser diode 26 even when signal light obtained from an
organism is weak. Then, there are obtained, from the lock-in
amplifier 36, output voltage lower at scanned points where blood
vessels run than at scanned points where blood vessels do not run
within scanned area of the fat 11. Thus, it is possible to
visualize the route of a blood vessel having a diameter of about 3
mm buried under fat having a thickness of 4 mm, for example.
Therefore, an image displayed on the monitor 38 is observed, which
enables the scope-assisted surgery with avoiding blood vessels,
that is, with preventing bleeding due to cutting of blood
vessels.
[0306] FIG. 3 is a diagram illustrating two examples of an optical
fiber amplifier which can be used as the light amplification means
32 shown in FIG. 2. FIG. 3(a) illustrates a configuration of a
rare-earth-doped optical fiber amplifier, and FIG. 3(b) illustrates
a configuration of an optical Raman amplifier.
[0307] The rare-earth-doped optical fiber amplifier shown in FIG.
3(a) has an excitation light source 41, a multiplex device 42 such
as a dichroic mirror or the like, a rare-earth-doped optical fiber
43 and an excitation light removal device 44, furthermore, it has
optical isolators 45 and 46 at the input end and the output end
respectively in order to prevent laser oscillation thereof. As the
rare-earth-doped optical fiber 43, there is used one in which an
optical fiber is doped with a rare earth such as Nd, Yb, Er, Tm, Pr
or the like.
[0308] In FIG. 3(a), signal light having a wave length of Xs input
through the optical isolator 45 is multiplexed with excitation
light having a wavelength of .lamda.p emitted from the excitation
light source 41 at the multiplex device 42, and input into the
rare-earth-doped optical fiber 43. Thus, the signal light is
amplified using stimulated emission in the rare-earth-doped optical
fiber 43 excited by excitation light. The output light from the
rare-earth-doped optical fiber 43 is rendered to be incident on the
excitation light removal device 44, in which residual excitation
light is removed so that only signal light is transmitted.
Thereafter, signal light having transmitted through the excitation
light removal device 44 is output via the optical isolator 46.
[0309] When signal light having a wavelength of 980 nm is amplified
by the rare-earth-doped optical fiber amplifier, as shown in FIG.
2, there is used, as each component, one having the following
properties, for example. That is, as the excitation light source
41, there is used one having a wavelength of 915 nm, optical output
of 50 mW and a spectral width of 1 nm. As the multiplex device 42,
an optical fiber wavelength multiplex coupler is used. As the
rare-earth-doped optical fiber 43, there is used a single clad
multimode Yb-doped optical fiber or a single clad single-mode
Yb-doped optical fiber having a length of 1 m and a low level of Yb
added. The excitation light removal device 44 removes excitation
light having a wavelength of 915 nm and uses a dielectric
multilayer filter allowing signal light having a wavelength of 980
nm to pass therethrough. As the isolators 45 and 46, there are used
ones having an operation wavelength of 980 nm, an isolation band of
about 30 nm and return loss of 30 dB. Thus, it is possible to
achieve a Yb-doped optical fiber amplifier for a wavelength band of
980 nm with low noise and high sensitivity.
[0310] With respect to the optical Raman amplifier shown in FIG.
3(b), in the configuration of the rare-earth-doped optical fiber
amplifier shown in FIG. 3(a), a Silica optical fiber 47 is used
instead of the rare-earth-doped optical fiber 43 and the Silica
optical fiber 47 is excited by excitation light, thereby signal
light is amplified using stimulated Raman scattering effects. The
other configurations and operation are the same as in the
rare-earth-doped optical fiber amplifier. Therefore, the same
components are represented with the same reference symbols, and the
description thereof will be omitted.
[0311] When signal light having a wavelength of 980 nm is amplified
by the optical Raman amplifier, as shown in FIG. 2, there is used,
as the excitation light source 41, one having a wavelength of 940
nm, optical output of 300 mW and a spectral width of 6 nm, for
example. As the Silica optical fiber 47, there is used a multimode
optical fiber or a single-mode optical fiber having a core diameter
of 6 .mu.m and a length of 2 km. The excitation light removal
device 44 removes excitation light having a wavelength of 940 nm
and uses a dielectric multilayer filter allowing signal light
having a wavelength of 980 nm to pass therethrough. As the other
components, there are used ones having properties described for the
rare-earth-doped optical fiber amplifier shown in FIG. 3(a). Thus,
it is possible to achieve an optical Raman amplifier for a
wavelength of 980 nm with low noise and high sensitivity.
[0312] It is noted that, although the configurations shown in FIGS.
3(a) and 3(b) are of forward excitation so that excitation light is
transmitted in the rare-earth-doped optical fiber 43 and the Silica
optical fiber 47 in the same direction as signal light, they can be
of backward excitation so that excitation light is transmitted in
the opposite direction of signal light, or bidirectional
excitation.
Second Embodiment
[0313] FIG. 4 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
second embodiment of the invention. In the embodiment, a laser
scanning confocal fluorescence microscope 51 is constituted, and a
He--Ne laser 52 continuously oscillating at a wavelength of 543 nm
is provided as the light generation means. With respect to laser
light emitted from the He--Ne laser 42, its light intensity is
adjusted by a light intensity adjustment device 53 such as an
acousto-optic modulator (AOM) or the like, for example. Then, the
light passes through a dichroic mirror 54, an X-Y galvano scanner
mirror 55, a pupil lens 56, a tube lens 57 and an objective lens
58, and is collected so that a living cell sample 60 to be
inspected is irradiated therewith. Thus, in the laser scanning
confocal fluorescence microscope 51, the light intensity adjustment
device 53, the dichroic mirror 54, the X-Y galvano scanner mirror
55, the pupil lens 56, the tube lens 57 and the objective lens 58
constitute the light irradiation means. Moreover, the X-Y galvano
scanner mirror 55 constitutes the light scan means.
[0314] It is noted that there is used, as the living cell sample
60, an object to be inspected dyed with fluorescent dye or an
object to be inspected in which fluorescent protein is expressed.
Here, an object to be inspected in which fluorescent protein DsRed
is expressed, is used. Thus, when the living cell sample 60 is
irradiated with laser light from the He--Ne laser 52, DsRed is
excited and thus fluorescence having a wavelength of about 570 nm
to 650 nm is generated.
[0315] The fluorescence generated from the living cell sample 60
passes through the objective lens 58, the tube lens 57, the pupil
lens 56 and the X-Y galvano scanner mirror 55 to the dichroic
mirror 54. The dichroic mirror 54 is configured so as to allow
light having a wavelength of 543 nm to pass therethrough and so as
to reflect light having a wavelength longer than 570 nm. Thereby,
the fluorescence having a wavelength of about 570 nm to 650 nm
generated in the living cell sample 60 is reflected by the dichroic
mirror 54.
[0316] The fluorescence reflected by the dichroic mirror 54 passes
through an optical isolator 61 and is collected by a collective
lens 62, thereafter it is amplified by a light amplification means
63 having a semiconductor optical amplifier or an optical fiber
amplifier. Then, the amplified fluorescence is received by a
photomultiplier tube (PMT) 64 as the photodetection means and
photoelectrically converted. The light amplification means 63 is
configured so as to have a gain band having a gain of about 10 dB
and a wavelength of 620 nm to 650 nm, for example.
[0317] The whole of laser scanning confocal fluorescence microscope
51 is controlled by a computer 65. Thus, laser light from the
He--Ne laser 52 is deflected by the X-Y galvano scanner mirror 55,
and the living cell sample 60 is two-dimensionally scanned in a
plane perpendicular to a light axis from the objective lens 58.
Then, the photoelectrically-converted output obtained from the
photomultiplier tube 64 is processed at each scanned point to
display a fluorescence image on a monitor 66.
[0318] According to the embodiment, fluorescence generated from the
living cell sample 60 through irradiation with laser light from the
He--Ne laser 52 is amplified by the light amplification means 63
and then photoelectrically converted by the photomultiplier tube
64, which makes it possible to photoelectrically convert
fluorescence with high sensitivity and promptly with using the
inexpensive photomultiplier tube 64 without increasing the
intensity of laser light with which the living cell sample 60 is
irradiated even when fluorescence as signal light obtained from the
living cell sample 60 is weak.
[0319] In addition, the optical isolator 61 is disposed at the
input side of the light amplification means 63, which can prevent
back reflection to the living cell sample 60. Thereby, it is
possible to prevent damages to the living cell sample 60 due to
excessive light irradiation therefor and variation given to signal
light. The reason will be described below. Generally, when light is
amplified using an optical amplifier, it is unavoidable to add
amplified spontaneous emission (ASE) noises. Thus, in the
configuration of FIG. 4, it could be possible that one part of ASE
generated at the light amplification means 63 is returned to the
side of the living cell sample 60 and the excessive light
irradiation damages the living cell sample 60 or varies signal
light emitted from the living cell sample 60. In the embodiment,
however, the optical isolator 61 is disposed at the incidence side
of the light amplification means 63, which can prevent back
reflection with ASE to the living cell sample 60 and thus prevent
damages to the living cell sample 60 and variation of signal light
therefrom.
Third Embodiment
[0320] FIG. 5 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
third embodiment of the invention. In the embodiment, a laser
scanning multiphoton fluorescence microscope 71 is constituted, and
this embodiment is different, as compared with the configuration of
the laser scanning confocal fluorescence microscope 51 shown in
FIG. 4, mainly in aspects that a Titanium-sapphire laser 72 is used
as the light generation means; the gain of the light amplification
means 63 is controlled by the computer 65 through a gain control
means 73; and the dichroic mirror 54 is disposed between the tube
lens 57 and the objective lens 58 and its optical properties are
rendered to be applied for the wavelength of emitted light from the
Titanium-sapphire laser 72.
[0321] In the embodiment, ultrashort optical pulses having a
repetition rate of 80 MHz, a pulse width of 150 fs and an
oscillation wavelength of 1000 nm are generated from the
Titanium-sapphire laser 72. With respect to the ultrashort optical
pulses from the Titanium-sapphire laser 72, its optical average
power is adjusted to 500 mW by the light intensity adjustment
device 53. Then, the pulses pass through the X-Y galvano scanner
minor 55, the pupil lens 56, the tube lens 57, the dichroic mirror
54 and the objective lens 58, and are collected to irradiate the
living cell sample 60 to be inspected therewith. Thereby, DsRed,
for example, in the living cell sample 60 is multiphoton-excited
(two-photon-excited, for example) to generate fluorescence.
[0322] The fluorescence generated from the living cell sample 60
passes through the objective lens 58 to the dichroic mirror 54. The
dichroic mirror 54 is configured so as to allow light having a
wavelength of 1000 nm from the Titanium-sapphire laser 72 to pass
therethrough and so as to reflect light having a short wavelength
of 700 nm or shorter. Thereby, fluorescence having a wavelength of
about 570 nm to 650 nm generated in the living cell sample 60 is
reflected by the dichroic minor 54.
[0323] The fluorescence reflected by the dichroic mirror 54 passes
through the optical isolator 61, is collected by the collective
lens 62 and amplified by the light amplification means 63,
thereafter the amplified fluorescence is received by the
photomultiplier tube 64 and photoelectrically converted.
[0324] Here, the fluorescence generated from the living cell sample
60 through two-photon excitation, for example, by excitation
optical pulses from the Titanium-sapphire laser 72 lasts for about
some nanoseconds. That is, the fluorescence generated from the
living cell sample 60 becomes pulse light synchronized with
excitation optical pulses from the Titanium-sapphire laser 72.
Thus, in the embodiment, the computer 65 controls through the gain
control means 73 so that, in synchronization with the timing at
which this pulse form of fluorescence is incident on the light
amplification means 63, the gain of the light amplification means
63 is increased at the timing of incidence of fluorescence.
[0325] The gain of the light amplification means 63 is controlled
in a way that when a semiconductor optical amplifier is used, its
driving current is increased or decreased or turned on or off, or
in a way that when an optical fiber amplifier is used, the
intensity of excitation light from an excitation light source is
increased or decreased or the excitation light is turned on or
off.
[0326] According to the embodiment, fluorescence generated from the
living cell sample 60 through multiphoton excitation by excitation
optical pulses from the Titanium-sapphire laser 72 is amplified by
the light amplification means 63 and then photoelectrically
converted by the photomultiplier tube 64, which makes it possible
to photoelectrically convert fluorescence resulted by two-photon
excitation with high sensitivity and promptly with using the
inexpensive photomultiplier tube 64 without increasing the
intensity of laser light with which the living cell sample 60 is
irradiated even when fluorescence as signal light obtained from the
living cell sample 60 is weak.
[0327] In addition, the gain of the light amplification means 63 is
controlled in synchronization with the timing of incidence of
fluorescence on the light amplification means 63, which can reduce
the mixture of ASE noises during time in which fluorescence is not
incident and thus improve the S/N.
Fourth Embodiment
[0328] FIG. 6 is a functional block diagram illustrating a
configuration of the optical inspection device according to the
fourth embodiment of the invention. In the embodiment, a laser
scanning CARS microscope 81 is constituted, and a two-wavelength
optical pulse source 82 is provided as the light generation means.
The two-wavelength optical pulse source 82 is configured so as to
generate light having a wave length of 1064 nm and 816 nm, for
example, at a pulse width of about 5 ps and a repetition rate of 80
MHz, respectively. With respect to two-wavelength pulse light from
the two-wavelength optical pulse source 82, its optical average
power is adjusted to some tens of mW respectively by the light
intensity adjustment device 53. Then, the light passes through the
X-Y galvano scanner mirror 55, the pupil lens 56, the tube lens 57
and the objective lens 58 and is collected to irradiate a non-dyed
living cell sample 83 to be inspected therewith. Thereby, CARS
light is generated from the living cell sample 83.
[0329] The transmitted light including CARS light from the living
cell sample 83 is collected by the collective lens 62 and amplified
by the light amplification means 63, thereafter the output light is
rendered to be incident on a band-pass filter 84 to extract CARS
light having desired wavelength components. Then, the CARS light
having passed through the band-pass filter 84 is received by the
photomultiplier tube 64 and photoelectrically converted.
[0330] That is, in the embodiment, the transmitted light including
CARS light from the living cell sample 83 is amplified by the light
amplification means 63 having a gain band wider than the wavelength
region of the CARS light, thereafter the band-pass filter 84
extracts CARS light having desired wavelength components and the
photomultiplier tube 64 receives it. For example, when the
wavelength of CARS light generated from the living cell sample 83
is about 660 nm, the light amplification means 63 is configured so
as to have a gain band of wavelength from 650 nm to 670 nm and
amplify transmitted light in such a gain band by 10 dB, for
example, and the band-pass filter 84 is constituted by a dielectric
multilayer filter having a central wavelength of 660 nm and a
transmitted band width of about 10 nm Moreover, CARS light
generated from the living cell sample 83 is generated with the same
repetition rate as of the excitation optical pulse train from the
two-wavelength optical pulse source 82 and with duration of about
some picoseconds. Thus, the computer 65 controls through the gain
control means 73 so that, in synchronization with the timing at
which CARS light is generated, the gain of the light amplification
means 63 is increased at the timing of incidence of CARS light, in
the same way as in the third embodiment.
[0331] The whole of laser scanning CARS microscope 81 is controlled
by the computer 65, in the same way as in the third embodiment.
Thereby, excitation pulses from the two-wavelength optical pulse
source 82 are deflected by the X-Y galvano scanner mirror 55, and
the living cell sample 60 is two-dimensionally scanned in a plane
perpendicular to a light axis from the objective lens 58. Then,
photoelectrically-converted output obtained from the
photomultiplier tube 64 at each scanned point is processed so that
a fluorescence image is displayed on the monitor 66.
[0332] According to the embodiment, CARS light generated from the
non-dyed living cell sample 83 is amplified by the light
amplification means 63 and then photoelectrically converted by the
photomultiplier tube 64, which makes it possible to
photoelectrically convert CARS light with high sensitivity and
promptly with using the inexpensive photomultiplier tube 64 without
increasing the intensity of laser light with which the living cell
sample 83 is irradiated even when CARS light as signal light
obtained from the living cell sample 83 is weak.
[0333] In addition, the band-pass filter 84 extracts CARS light
having desired wavelength components from output light of the light
amplification means 63, and the gain of the light amplification
means 63 is controlled in synchronization with the timing of
incidence of CARS light generated from the living cell sample 83,
which makes it possible to remove undesired ASE noises which are
within the gain band but out of desired wavelength region of the
light amplification means 63 and thus improve the S/N.
Fifth Embodiment
[0334] FIG. 7 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the fifth embodiment of the invention. The
electromagnetic wave detection device amplifies electromagnetic
waves to be detected emitted from a sample to be observed and
provides them as electrical signals to a signal processing system.
In the embodiment, since used for observing electromagnetic waves
which are spontaneously emitted such as fluorescence and the like
through bioluminescence, chemiluminescence and bioluminescence
energy transfer, unlike the first to the fourth embodiments, the
light generation means and the light irradiation means are not
essential components.
[0335] The electromagnetic wave detection device according to the
embodiment is provided with a mode adjustment means 110 adjusting
the mode state of detected incident multimode electromagnetic
waves, an amplification means 120 amplifying the electromagnetic
waves whose mode state has been adjusted by the mode adjustment
means 110 and a conversion means 130 converting the electromagnetic
waves amplified by the amplification means 120 to electrical
signals and outputting them to the signal processing system. The
amplification means 120 has amplification properties excellent in
the SNR for a specific amplification spatial mode, and the mode
adjustment means 110 adjusts incident multimode electromagnetic
waves to of a mode substantially equal to the amplification spatial
mode by the amplification means 120 by converting the energy mode
distribution.
[0336] FIG. 8 is a diagram explaining mode adjustment by the mode
adjustment means 110. The mode adjustment means 110 is configured
so that incidence of multimode electromagnetic waves is allowed at
the incidence side and, at the output side, adjustment is made to
have the energy mode distribution substantially equal to of the
amplification spatial mode of the subsequent amplification means
120, that is, the energy mode distribution with high consistency.
FIG. 8(a) is an example of energy mode distribution of incident
electromagnetic waves at the incidence side of the mode adjustment
means. In this example, energy is distributed to a fundamental mode
represented by the mode No. 1 and high-order modes represented by
mode No. 2 to No. 7 FIGS. 8(b) and 8(c) are diagrams illustrating
energy mode distribution of electromagnetic waves at the output
side of the mode adjustment means 110 in different cases,
respectively. In FIG. 8(b), the allowed mode is only two modes
represented by mode No. 1 and No. 2, and energy in each mode at the
incidence side of the mode adjustment means 110 is converted to
these two modes with low loss. Moreover, FIG. 8(c) shows an example
in which each of modes No. 1 to No. 7, which is the same for the
incidence side, is allowed as energy mode distribution at the
output side of the mode adjustment means but the distribution of
two modes with mode No. 1 and No. 2 is significantly high because
of the variation of energy mode distribution. That is, the number
of spatial modes is artificially reduced in FIG. 8(c). The mode
adjust means 110 may be either of one reducing the number of modes
itself as in FIG. 8(b) or one varying the energy distribution as in
FIG. 8(c).
[0337] With the schematic configuration of FIG. 7, electromagnetic
waves to be detected which are scattered waves or waves with
distorted wavefront are incident on the mode adjustment means 110
according to a mode allowed at the incidence side of the mode
adjustment means 110. At that time, as a larger number of
high-order modes are allowed, the coupling efficiency between
detected electromagnetic waves and the mode adjustment means 110
becomes higher. Thereafter, the detected light is subjected to mode
adjustment by the mode adjustment means 110 and emitted to the
amplification means 120. Then, the mode distribution of energy of
detected electromagnetic waves emitted from the mode adjust means
110 is substantially equal to the amplification spatial mode of the
amplification means 120, which reduces energy loss due to
inconsistency of the mode. Furthermore, the detected
electromagnetic waves are amplified by the amplification means 120,
emitted to the conversion means 130, and converted to electrical
signals by the conversion means 130. The electrical signals output
from the conversion means 130 are converted to desired data by the
subsequent signal processing system.
[0338] According to the embodiment, as explained above, there is
disposed the mode adjustment means 110 adjusting, by converting the
energy mode distribution, incident multimode electromagnetic waves
to of a mode substantially equal to the amplification spatial mode
of the amplification means 120 before the amplification means and
the conversion means, which makes it possible to collect detected
electromagnetic waves with high efficiency even when they are
scattered electromagnetic waves or electromagnetic waves with
distorted wavefront, thus enabling high-speed high-sensitivity
photodetection.
Sixth Embodiment
[0339] FIG. 9 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
sixth embodiment of the invention. The device detects signal light
to be detected obtained by irradiation with laser light and
visualizes the position of blood vessels existent under fat.
[0340] The rigid endoscope blood vessel imaging device is
configured so that an organism sample 200 is irradiated with laser
light for lighting while being scanned, and light reflected or
scattered in the surface and the inside of the organism sample 200
is detected by the electromagnetic wave detection device having the
configuration shown in FIG. 7 and converted to electrical signals,
thereafter the electrical signals are processed by the signal
processing system to display an image.
[0341] The rigid endoscope blood vessel imaging device is provided,
as the lightning optical system, with a single-mode fiber (SMF)
outputting Er-doped fluoride fiber laser 161 having a wavelength of
543 nm and output of 2 mW, an isolator 162, a single-mode fiber
(SMF) 163 and a collimator 164, and is configured so that the
desired observation position of the organism sample 200 is
irradiated with laser light emitted from the Er-doped fluoride
fiber laser 161 as a substantially-parallel beam through the
collimator 164 via the isolator 162 and the SMF 163.
[0342] Furthermore, a laser driver 166 driving the Er-doped
fluoride fiber laser 161 is provided, and the Er-doped fluoride
fiber laser 161 is configured so that its output condition is
controlled through the laser driver 166, by the computer 169 to be
described controlling the whole of rigid endoscope blood vessel
imaging device.
[0343] Moreover, in order to detect signal light from the organism
sample 200, the rigid endoscope blood vessel imaging device shown
in FIG. 9 is provided, as components corresponding respectively to
the mode adjustment means 110, the amplification means 120 and the
conversion means 130 in the electromagnetic wave detection device
shown in FIG. 7, with a tapered fiber 111, an Er-doped fluoride
optical fiber amplifier 121 and a silicon PIN-PD (PIN photo diode)
131. Furthermore, there are provided, after PIN-PD 131, an electric
amplifier 167 amplifying electrical signals output from the PIN-PD
131 and an analog-to-digital (AD) converter 168 converting analog
electrical signals amplified by the electric amplifier 167 to
digital signals.
[0344] The tapered fiber is an optical fiber having a configuration
in which the diameter of core portion where light is wave-guided is
varied from the input side to the output side. The incidence
surface of the tapered fiber 111 is disposed at a position front
onto the organism sample 200 and adjacent to the collimator 164 and
fixed, together with the collimator 164, on a scan mount 165. As
FIG. 10 shows a schematic shape of a longitudinal section of the
core portion, the tapered fiber 111 is of tapered form with a core
diameter at the input side being larger than that at the output
side. In the embodiment, there is used one with a core diameter at
the input side and the output side being 50 .mu.m and 4 .mu.m
respectively and a length being 1.0 m.
[0345] The Er-doped fluoride optical fiber amplifier 121 is
configured including isolators 173a, 173b, a wavelength divisional
multiplexing (WDM) coupler 174, an Er-doped fluoride fiber 175, an
optical filter 176 and a laser diode (LD) 177, as FIG. 11 shows its
configuration diagram.
[0346] The isolators 173a and 173b are disposed at the input side
and the output side of the Er-doped fluoride optical fiber
amplifier 121 to block back reflection. The LD 177 is excitation
light source of the Er-doped fluoride fiber 175, and a laser diode
having a wavelength of 975 nm and output of 100 mW is used.
Moreover, a driver 172 connected to the LD 177 and driving it is
provided. The WDM coupler 174 is configured so as to multiplex
excitation light from the LD 177 and signal light emitted from the
isolator 173a at the incidence side and output it to the Er-doped
fluoride fiber 175. The Er-doped fluoride fiber 175 is a
single-mode Er-doped fluoride fiber having a core diameter of 4
.mu.m, and it amplifies signal light by excitation light and
outputs residual excitation light and ASE. The optical amplifier
176 is provided at the output side of the Er-doped fluoride fiber
175, and it removes residual excitation light and ASE to emit only
signal light. The signal light is emitted from the Er-doped
fluoride optical fiber amplifier 121 through the isolator 173b. The
Er-doped fluoride optical fiber amplifier 121 can amplify output of
the tapered fiber 111 by about 15 dB.
[0347] Moreover, the rigid endoscope blood vessel imaging device of
the embodiment has a computer 169 controlling each unit of the
device and processing digital signals output from an AD converter
168, as shown in FIG. 9. The computer 169 is connected to the laser
driver 166, the driver 171 and the driver 172 to control the
Er-doped fluoride fiber laser 161, the Er-doped fluoride optical
fiber amplifier 121 and the scan mount 165 respectively, and is
configured to perform signal processing with associating output
signals of the AD converter 168 with each information of output of
the Er-doped fluoride fiber laser 161, the gain of the Er-doped
fluoride optical fiber amplifier 121 and the position of the scan
mount 165 and display the result on a display monitor 170.
[0348] With the above configuration, when the rigid endoscope blood
vessel imaging device of the embodiment is used in observing an
organism sample, the computer 169 causes the scan mount 165 to scan
through the driver 171, and drives the Er-doped fluoride fiber
laser 161 through the laser driver 166 so that the organism sample
200 is irradiated with laser light from the collimator 164. The
laser light is reflected or scattered in the surface and the inside
of the organism sample 200 and incident on the tapered fiber 111 as
signal light having a wavelength of 543 nm.
[0349] Here, since the core diameter at the incidence side of the
tapered fiber 111 is 50 .mu.m, as compared with a fiber having a
core diameter of 4 .mu.m, the area of incidence surface is larger
and a spatially wider range of signals can be collected, and a
large number of other high-order modes in addition to the
fundamental mode can be incident. At the output side of the tapered
fiber, on the other hand, the core diameter is as small as 4 .mu.m,
and thus the energy distribution among modes is adjusted and
concentrated to the fundamental mode.
[0350] The signal light whose mode has been adjusted is incident on
the Er-doped fluoride optical fiber amplifier 121 and then on the
single-mode Er-doped fluoride fiber 175, shown in FIG. 11, having a
fundamental mode as the amplification spatial mode and a core
diameter of 4 .mu.m. Since the mode distribution at the output side
of the tapered fiber is substantially equal to the amplification
spatial mode of the Er-doped fluoride fiber 175, the coupling
efficiency at the combining portion thereof is higher. Thus, energy
loss of signal light incident on the tapered fiber 111 can be
minimized and amplification can be performed in a
substantially-single mode at the Er-doped fluoride optical fiber
amplifier 121, which makes it possible to suppress generation of
ASE and thus obtain signal light having the high SNR.
[0351] Furthermore, signal light emitted from the Er-doped fluoride
optical fiber amplifier 121 is converted to electrical signals by
the PIN-PD 131, amplified by the electric amplifier 167, converted
to digital signals by the AD converter 168 and transmitted to the
computer 169, as shown in FIG. 9. The computer 169 performs signal
processing with associating the electrical signals with information
of scanned position and the like obtained from the driver 171 to
generate a blood vessel image, and displays it on the monitor 170.
Thus, it becomes possible to image the position of blood vessels
existent under fat at high speed.
[0352] According to the embodiment, as explained above, the tapered
fiber 111 is disposed before the Er-doped fluoride optical fiber
amplifier 121, which can expand a light receiving surface and,
further, since the number of spatial modes allowed at the incidence
side is large, lots of signal light to be detected can be incident
even if it is scattered light or light with distorted wavefront.
Moreover, the tapered fiber 111 converts energy mode distribution
to of a mode substantially equal to the amplification spatial mode
of the Er-doped fluoride optical fiber amplifier 121 having a small
number of amplification spatial modes, which can reduce ASE, thus
enabling optical amplification with high SNR. Furthermore, the use
of the tapered fiber 111 enables mode adjustment with small energy
losses. Therefore, the optical amplification in which the light
intensity of signals is high but the light intensity of noises is
low is enabled even when detected signal light is scattered light
or light with distorted wavefront. Therefore, the optical amplifier
is disposed before the PIN-PD 131, which enables photodetection at
high speed and with high sensitivity.
[0353] Moreover, the tapered fiber 111, which is one kind of
optical fibers, is used as the mode adjustment means 110, which
stably achieves a long spatial-mode-adjustment waveguide. When the
waveguide is longer, it becomes possible to adjust spatial mode
adiabatically, thus enabling the spatial mode adjustment with
smaller loss. Moreover, the use of the optical fiber makes fine
adjustment of spatial optical system unnecessary, thus improving
the degree of freedom in use. Furthermore, with respect to the
tapered fiber 111, the degree of freedom for its design is
significantly high, which enables the mode adjustment means
suitable for the condition of light to be detected. Moreover, the
tapered fiber 111 can be produced relatively easily, which makes it
possible to provide a low-cost photodetection device.
[0354] Moreover, there is used, as the amplification means 120, the
Er-doped fluoride optical fiber amplifier 121, which enables
amplification having the high amplification efficiency with high
gain and low noise. Furthermore, the optical amplification is
enabled in wavelength regions where no operation is possible with
the Silica optical fiber amplifier and, in particular, the
efficient optical amplification in visible bands becomes
possible.
Seventh Embodiment
[0355] FIG. 12 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the seventh embodiment of the invention. With respect
to the electromagnetic wave detection device, in the configuration
of the electromagnetic wave detection device shown in FIG. 7, a
plurality of mode adjustment means 110 is provided and a multiplex
means 140 is provided between the mode adjustment means 110 and the
amplification means 120.
[0356] With the configuration, electromagnetic waves to be detected
are input to the plurality of mode adjustment means 110 so that the
spatial mode is adjusted in each of the mode adjustment means 110.
Thereafter, the electromagnetic waves output from the plurality of
mode adjustment means 110 are input to the multiplex means 140 to
be multiplexed. The detected electromagnetic signal waves output
from the multiplex means 140 are amplified by the amplification
means 120 and also converted to electrical signals by the
conversion means 130. The electrical signals output from the
conversion means 130 are converted to desired data by the
subsequent signal processing system.
[0357] According to the embodiment, there is disposed, before the
amplification means 120 and the conversion means 130, the plurality
of mode adjustment means 110 adjusting the mode of incident
multimode electromagnetic waves which are incident in parallel,
which makes it possible to collect signal waves with high
efficiency even when the electromagnetic waves to be detected are
scattered electromagnetic waves or electromagnetic waves with
distorted wavefront, thus enabling electromagnetic wave detection
at high speed and with high sensitivity, in addition to the effects
exerted by the first embodiment. Furthermore, there is provided the
multiplex means 140 multiplexing a plurality of electromagnetic
waves output from the plurality of mode adjustment means 110, which
can further improve the operation stability of the whole device by
multiplexing incident electromagnetic waves with the number of
modes reduced.
Eighth Embodiment
[0358] FIG. 13 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
eighth embodiment of the invention using the electromagnetic wave
detection device shown in FIG. 12. With respect to the rigid
endoscope blood vessel imaging device, in the rigid endoscope blood
vessel imaging device shown in FIG. 9, a lens for lighting 164b is
used instead of a collimator 164a, and a plurality of tapered
fibers 111 is provided in parallel and at the output side thereof a
fiber coupler 141 is provided as the multiplex means 140. Moreover,
the lens for lighting 164b and the plurality of tapered fibers 111
are fixed to the scan mount 165 so that their incidence surfaces
are front onto the organism sample 200.
[0359] Unlike the collimator 164a shown in FIG. 9, the lens for
lighting 164b diffuses laser light having transmitted through the
SMF 163 to irradiate the area of organism sample 200 front onto the
incidence surface of the tapered fiber 111. The laser light is
reflected or scattered in the surface and the inside of the
organism sample 200 and incident on the plurality of tapered fibers
111 as multimode light. With respect to the signal light incident
on each of tapered fibers 111, its energy distribution among modes
is adjusted, thereafter the light is incident, as light with the
small number of modes including the fundamental mode, on the fiber
coupler 141 to be multiplexed. Then, the signal light multiplexed
by the fiber coupler 141 is incident on the Er-doped fluoride
optical fiber amplifier 121. Since other configurations and
operation are the same as in the sixth embodiment, the same
components are represented with the same reference symbols, and the
description thereof will be omitted.
[0360] According to the embodiment, as explained above, the
plurality of tapered fibers 111 is provided, and more light can be
collected. Moreover, a device having a smaller number of spatial
modes generally achieves more stable operation, so that the
operation stability of the whole device can be further improved
when multiplexing signal light by the multiplex means with the
number of spatial modes reduced.
Ninth Embodiment
[0361] FIG. 14 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the ninth embodiment of the invention. The
electromagnetic wave detection device is configured so that one
mode adjustment means 110 and one amplification means 120 are
paired and a plurality thereof is provided in parallel in the
configuration of the electromagnetic wave detection device shown in
FIG. 7 and the output from each of the amplification means 120 is
input to the conversion means 130 capable of processing the output
in parallel.
[0362] In the above configuration, electromagnetic waves to be
detected are input to the plurality of mode adjustment means 110 so
that the spatial mode is adjusted in each of the mode adjustment
means 110. Thereafter, electromagnetic waves output from the
plurality of mode adjustment means 110 are input to the
corresponding amplification means 120 to be amplified, and also
converted to electrical signals in parallel by the conversion means
130. The electrical signals output from the conversion means 130
are converted to desired data by the subsequent signal processing
system.
[0363] According to the embodiment, there are disposed a plurality
of mode adjustment means 110 adjusting, by converting the energy
mode distribution, incident multimode electromagnetic waves which
are incident in parallel to of a mode substantially equal to the
amplification spatial mode of the amplification means 120 before
the corresponding amplification means 120 and the conversion means
130 respectively, which makes it possible to collect detected
electromagnetic waves with high efficiency even when they are
scattered electromagnetic waves or electromagnetic waves with
distorted wavefront, thus enabling photodetection at high speed and
with high sensitivity. Furthermore, a plurality of mode adjustment
means 110 and a plurality of amplification means 120 corresponding
thereto are provided, and electromagnetic waves output from each of
amplification means 120 are converted to electrical signals in
parallel, which makes it possible to simultaneously obtain
information of a plurality of points such as image information and
the like.
Tenth Embodiment
[0364] FIG. 15 is a diagram illustrating a schematic configuration
of the high sensitivity endoscope according to the tenth embodiment
of the invention using the electromagnetic wave detection device
shown in FIG. 14. The high sensitivity endoscope is configured so
that it irradiates the organism sample 200 with laser light for
lighting and the light reflected or scattered in the surface and
the inside of the organism sample 200 is detected by the
electromagnetic wave detection device shown in FIG. 14 and
converted to electrical signals, thereafter the electrical signals
are processed by signal processing system to display an image.
[0365] As the optical system irradiating the organism sample 200
with laser light for lighting, the high sensitivity endoscope is
provided with an LD 180 having a wavelength of 635 nm and output of
20 mW, an isolator 181, a multi-mode fiber (MMF) 182a and a lens
for lighting 183, and is configured so that the output from the LD
180 as the light source is output, via the isolator 181 and the MMF
182a, to the air from the lens for lighting 183, with which the
organism sample 200 is irradiated.
[0366] Moreover, a laser driver 179 driving the LD 180 is provided,
and the LD 180 is configured so that its output is controlled
through the laser driver 179 by the computer 169 controlling the
whole of the high sensitivity endoscope.
[0367] Furthermore, The electromagnetic wave detection device
detecting light to be detected from the organism sample 200 uses
128.times.128 tapered fibers 111 as the mode adjustment means 110,
128.times.128 semiconductor optical amplifiers (SOA) 122
corresponding to each of the tapered fibers 111 as the
amplification means 120 and a CCD camera 132 having 128.times.128
pixels as the conversion means 130, respectively. Moreover, an
isolator 184a is provided between each of tapered fibers 111 and
the corresponding SOA 122 respectively, and an isolator 184b and a
band-pass filter (BPF) 185 for removing ASE are provided between
each of the SOA 122 and the CCD camera 132. The analog-to-digital
(AD) converter 168 converting analog electrical signals to digital
signals is provided after the CCD camera 132.
[0368] It is noted that there is used, as the tapered fiber 111,
one having a core diameter at the input side and the output side of
50 .mu.m and 9 .mu.m respectively and a length of 1.0 mm, and it is
configured so that the incident surface thereof is front onto the
organism sample 200 and signal light from respectively different
positions of the organism sample 200 is incident by irradiation
with laser light from the lens for lighting 183, and it is fixed,
together with the lens for lighting 183, to a housing 178.
Moreover, the SOA 122 is configured to be controlled by the
computer 169 through the driver 186.
[0369] Thus, signal light having a wavelength of 635 nm reflected
or scattered in the surface or the inside of the organism sample
200 is input on each of the tapered fibers 111 and its mode is
adjusted. Output from each of the tapered fiber 111 is input to the
corresponding SOA 122 through the isolator 184 and amplified by
about 18 dB. Output from each SOA 122 is incident on the
corresponding BPF 185 via the corresponding isolator 184, and ASE
is removed. Output from each BPF 185 is input so as to correspond
to each pixel of the CCD camera 132 having 128.times.128 pixels,
and converted to electrical signals. Furthermore, signal output
converted to electrical signals by the CCD camera 132 is converted
to digital signals by the AD converter 168.
[0370] Moreover, the high sensitivity endoscope of the embodiment
has a computer 169 controlling each unit of the device and
processing digital signals output from the AD converter 168. The
computer 169 is connected to the laser driver 179 and the driver
186 respectively to control the LD 180 and the SOA 122, and
performs signal processing with associating output signals from the
AD converter 168 with output of the LD 180 and the gain of the SOA
122 so as to display the result on the display monitor 170 as an
endoscope image, for example.
[0371] According to the embodiment, as explained above, it is
possible to achieve the same effects as in the sixth embodiment and
obtain an endoscope image at higher speed and with higher
sensitivity as compared with the conventional technique. In the
embodiment, moreover, a plurality of tapered fibers 111 and a
plurality of SOA 122 corresponding thereto are provided, and it is
possible to simultaneously obtain information of a plurality of
points of the organism sample 200 by converting optical output from
each SOA 122 to electrical signals in parallel. Therefore, the
embodiment is effective particularly when generating
two-dimensional images.
[0372] Furthermore, the SOA 122 is used as the amplification means
122, which makes it possible to constitute a compact and low-cost
photodetection system and to integrate with a plurality of
semiconductor optical amplifiers or other semiconductor devices
such as photodiode (PD) or the like. Moreover, the embodiment also
has an advantage that provided power may be small. Furthermore, the
SOA can operate in a wider wavelength region as compared with the
optical fiber amplifier, and thus it can be applied for a variety
of detected light.
Eleventh Embodiment
[0373] FIG. 16 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the eleventh embodiment of the invention. With respect
to the electromagnetic wave detection device, in the configuration
of the electromagnetic wave detection device shown in FIG. 7, a
collecting means 150 collecting electromagnetic waves to be
detected is provided before the mode adjustment means 110. Thus, it
is possible to further increase the amount of signal
electromagnetic waves which can be detected, in addition to the
effects exerted by the invention of claim 16.
Twelfth Embodiment
[0374] FIG. 17 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
twelfth embodiment of the invention using the electromagnetic wave
detection device shown in FIG. 16. With respect to the rigid
endoscope blood vessel imaging device, a collective lens 151 is
provided before the incidence surface of the tapered fiber 111 in
the rigid endoscope blood vessel imaging device shown in FIG. 9.
The collective lens 151 is provided before the tapered fiber 111,
which makes it possible to take a larger portion of light reflected
or scattered in the surface and the inside of the organism sample
200 into the tapered fiber 111. Moreover, there is an advantage
that even substances to be detected existent in a deep portion of
an object to be detected or far portion therefrom can be also
detected with high sensitivity and high SNR.
Thirteenth Embodiment
[0375] FIG. 18 is a diagram illustrating a schematic configuration
of a laser scanning multiphoton microscope according to the
thirteenth embodiment of the invention. In the embodiment, the
electromagnetic wave detection device shown in FIG. 16 is used in
the laser scanning multiphoton microscope so as to detect signal
light from the living cell sample.
[0376] As shown in FIG. 18, the laser scanning multiphoton
microscope of the embodiment is constituted including a
Titanium-sapphire laser 187, a light intensity adjustment device
188, an X-Y galvano scanner mirror 189, a pupil lens 190, a tube
lens 191, a dichroic mirror 192, and an objective lens 193
constituting the objective optical system, an isolator 202, a
collective lens 152, a tapered waveguide 112, an SOA 123, a PIN-PD
133, an electric amplifier 167, an AD converter 168 and a gain
control means 203.
[0377] The Titanium-sapphire laser 187 is a light source generating
ultrashort optical pulses having a repetition rate of 80 MHz, a
pulse width of 150 fs and an oscillation wavelength of 1060 nm With
respect to the ultrashort optical pulses from the Titanium-sapphire
laser 187, their optical average power is adjusted to 100 mW by the
light intensity adjustment device 188, and the pulses pass through
the X-Y galvano scanner mirror 189, the pupil lens 190, the tube
lens 191, the dichroic mirror 192 and the objective lens 193 and
are collected so that the living cell sample 201 to be inspected is
irradiated therewith. At that time, the X-Y galvano scanner mirror
189 is driven to scan the position on the sample irradiated with
laser light. Thus, it is possible to generate fluorescence in a
desired area in the living cell sample 201 through multiphoton
excitation (two-photon excitation, for example) of red fluorescent
protein (DsRed), for example.
[0378] Moreover, the objective lens 193 guides fluorescence
generated from the living cell sample 201 to the dichroic mirror
192. The dichroic mirror 192 is configured so as to allow light
having a wavelength of 1060 nm from the Titanium-sapphire laser 187
to pass therethrough and so as to reflect light having a short
wavelength of 700 nm or shorter. Thus, fluorescence having a
wavelength of about 570 nm to 650 nm generated in the living cell
sample 201 is reflected by the dichroic mirror 192.
[0379] The collective lens 152, the tapered waveguide 112, the SOA
123 and the PIN-PD 133 correspond respectively to the collecting
means 150, the mode adjustment means 110, the amplification means
120 and the conversion means 130 of the electromagnetic wave
detection device shown in FIG. 16. The fluorescence reflected by
the dichroic mirror 192 is collected by the collective lens 152 via
the isolator 202 and input to the tapered waveguide 112. The
tapered waveguide 112 has 8 spatial modes at the incidence side,
and is configured so that the number of modes is decreased to 2 at
the output side by mode adjustment. The fluorescence output from
the tapered waveguide 112 is incident on the SOA 123 controlled by
the external computer 169 through the gain control means 203 and
amplified, thereafter the silicon PIN-PD 133 converts it to
electrical signals. Since the number of modes of incident signal
light is decreased, the SOA 123 can suppress the occurrence of ASE
and perform amplification with high SNR.
[0380] Furthermore, electrical signals output from the PIN-PD 133
are amplified by the electric amplifier 167, converted to digital
signals by the AD converter 168 and transmitted to the external
computer 169. The computer 169 performs signal processing with
associating signals received from the AD converter 168 with
information of scanned positions and the like obtained from the X-Y
galvano scanner mirror 189 and displays the result on the monitor
170 as a microscope image.
[0381] It is noted that, in the laser scanning multiphoton
fluorescence microscope, the fluorescence generated from the living
cell sample 201 through two-photon excitation, for example, by
excitation optical pulses from the Titanium-sapphire laser 187
lasts for about some nanoseconds. That is, the fluorescence
generated from the living cell sample 201 becomes pulse light
synchronized with excitation optical pulses from the
Titanium-sapphire laser 187. Thus, in the embodiment, the computer
169 controls so that, in synchronization with the timing at which
the pulse form of fluorescence is incident on the SOA 123, the gain
of the SOA 123 is increased at the timing of incidence of
fluorescence.
[0382] According to the embodiment, fluorescence generated from the
living cell sample 201 through multiphoton excitation by excitation
optical pulses from the Titanium-sapphire laser 187 is subjected to
mode adjustment so that the number of spatial modes is decreased
using the tapered waveguide 112, amplified by the SOA, and then
photoelectrically converted by the silicon PIN-PD 133. Thus, it is
possible to photoelectrically convert fluorescence resulted by
two-photon excitation with high sensitivity and at high speed
without excessively increasing the intensity of laser light with
which the living cell sample 201 is irradiated even when
fluorescence as signal light obtained from the living cell sample
201 is weak.
[0383] In addition, the gain of the SOA 123 is controlled in
synchronization with the timing of incidence of fluorescence on the
SOA 123, which can reduce the mixture of ASE generated by providing
power to the optical amplifier during time in which fluorescence is
not incident, thus improving the S/N. Furthermore, it is possible
to easily adjust the level of signals to be detected by varying the
gain of the SOA 123.
Fourteenth Embodiment
[0384] FIG. 19 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the fourteenth embodiment of the invention. With
respect to the electromagnetic wave detection device, in the
configuration of the electromagnetic wave detection device shown in
FIG. 7, a plurality of collecting means 150 and the multiplex means
140 multiplexing detected electromagnetic waves from the plurality
of collecting means 150 are provided before the mode adjustment
means 110.
[0385] In the above configuration, electromagnetic waves to be
detected are collected by the plurality of collecting means 150 and
input to the multiplex means 140. The multiplex means 140
multiplexes the input plurality of detected light, and outputs it
to the mode adjustment means 110. The other operation is the same
as in the electromagnetic wave detection device in FIG. 7.
[0386] According to the embodiment, a plurality of collecting means
150 is provided, which makes it possible to collectively obtain
signal electromagnetic waves from a plurality of parts and,
further, multiple means 140 collects the signal electromagnetic
waves from a plurality of parts, which increases the energy of the
signal electromagnetic waves input to the amplification means 120
and further improves the SNR.
Fifteenth Embodiment
[0387] FIG. 20 is a diagram illustrating a schematic configuration
of rigid endoscope blood vessel imaging device according to the
fifteenth embodiment of the invention shown in FIG. 19. With
respect to the rigid endoscope blood vessel imaging device, in the
rigid endoscope blood vessel imaging device shown in FIG. 9, the
lens for lighting 164b is used instead of the collimator 164a and
there are provided, before the tapered fiber 111, a plurality of
collective lenses 151, a plurality of multi-mode fiber (MMF) 182b
connected to the collective lenses 151 and the multimode fiber
coupler 142 multiplexing signal light from each MMF 182b. It is
noted that the collective lens 151 and the multimode fiber coupler
142 correspond respectively to the collecting means 150 and the
multiplex means 140 in FIG. 19.
[0388] Moreover, the lens for lighting 164b and each collective
lens 151 are fixed to the scan mount 165 so that they are front
onto the sample 200. Furthermore, unlike the collimator 164a shown
in FIG. 9, the lens for lighting 164b diffuses laser light having
transmitted through the SMF 163 to irradiate the area of the
organism sample 200 front onto the incidence surface of each
collective lens 151.
[0389] Thus, laser light emitted from the lens for lighting 164b is
reflected or scattered in the surface and the inside of the
organism sample 200, collected by the plurality of collective lens
151 and multiplexed by the multimode fiber coupler 142 through the
MMF 182b, thereafter it is incident on the tapered fiber 11 as
multimode light. Since other configurations and operation are the
same as in the sixth embodiment, the same components are
represented with the same reference symbols, and the description
thereof will be omitted.
[0390] According to the embodiment, as explained above, the
plurality of collective lenses 151 is provided, which make it
possible to collectively obtain signal light from a plurality of
parts and thus to further increase the amount of signal light which
can be detected. Moreover, signal light from a plurality of parts
is collected by the multimode fiber coupler 142 and thus the number
of the subsequent tapered fiber 111, Er-doped fluoride optical
fiber amplifier 121 and PIN-PD 131 can be reduced to one. In
addition, signal light from a plurality of parts is collected,
which can increase signal light energy input to the Er-doped
fluoride optical fiber amplifier 121. Therefore, it becomes
possible to obtain an endoscope image at higher speed and with
higher sensitivity.
Sixteenth Embodiment
[0391] FIG. 21 is a block diagram illustrating a schematic
configuration of the electromagnetic wave detection device
according to the sixteenth embodiment of the invention. With
respect to the electromagnetic wave detection device, the
collecting means 150 is provided before each mode adjustment means
110 in the configuration of the electromagnetic wave detection
device shown in FIG. 14. Thus, it becomes possible to guide a
larger amount of detected electromagnetic wave to the mode
adjustment means 110, in addition to the effects exerted by the
electromagnetic wave detection device according to the ninth
embodiment.
Seventeenth Embodiment
[0392] FIG. 22 is a diagram illustrating a schematic configuration
of the rigid endoscope blood vessel imaging device according to the
seventeenth embodiment of the invention using the electromagnetic
wave detection device shown in FIG. 21. With respect to the rigid
endoscope blood vessel imaging device, the collective lens 152 is
provided before the plurality of tapered fibers 111 in the rigid
endoscope blood vessel imaging device according to the tenth
embodiment shown in FIG. 15. The collective lens 152 is provided
before the tapered fiber 111, which makes it possible to take a
larger portion of light reflected or scattered in the surface and
the inside of the organism sample 200 into each tapered fiber 111.
Since other configurations and operation are the same as in the
tenth embodiment, the same components are represented with the same
reference symbols, and the description thereof will be omitted.
[0393] According to the embodiment, as explained above, the
collective lens 152 is provided before the tapered fiber 111, which
make it possible to further increase the amount of signal light
which can be detected. Therefore, it becomes possible to obtain an
endoscope image at higher speed and with higher sensitivity.
[0394] It is noted that the invention is not limited to the above
embodiments, and many variations and modifications can be
implemented. For example, the laser scanning confocal fluorescence
microscope 51 shown in the second embodiment and the laser scanning
multiphoton fluorescence microscope 71 shown in the third
embodiment are not limited to of reflection type, and can be
configured as of transmission type. Similarly, the laser scanning
CARS microscope 81 shown in the fourth embodiment is not limited to
of transmission type and can be configured as of reflection type,
respectively.
[0395] Moreover, although the tapered fiber 111 or the tapered
waveguide 112 is used as the mode adjustment means, the means is
not limited thereto, and a tapered photonic crystal waveguide, a
long-period fiber bragg grating, a refractive-index modulation flat
waveguide or the like can be used.
[0396] For example, in the thirteenth embodiment, there can be
used, instead of the tapered waveguide 112, a refractive-index
distribution type waveguide having nonuniform refractive-index
distribution in a longitudinal direction of the waveguide or a
waveguide having nonuniform stress distribution or nonuniform
temperature distribution in a longitudinal direction of the
waveguide. In this case, the variation of refractive-index, stress
or temperature in the optical waveguide causes energy transfer
among spatial modes. Such variation of refractive-index, stress or
temperature is intentionally given into the optical waveguide,
which can induce the variation of energy ratio among spatial
modes.
[0397] Moreover, although the Er-doped fluoride optical fiber
amplifier or the SOA is used as the amplification means 120 in the
fifth to seventeenth embodiments, the means is not limited thereto.
For example, instead of these amplifiers, there can be used an
optical fiber amplifier using stimulated Raman scattering effects.
The wavelength region where the rare-earth-doped optical fiber
amplifier operates is very discrete, and thus there is wavelength
region in which optical amplifying effects cannot be obtained.
However, since the optical fiber amplifier using stimulated Raman
scattering effects do not specify the wavelength region where it
operates, the use thereof enables optical amplification in any
wavelength region. Moreover, other optical fiber amplifiers like a
fiber Brillouin optical amplifier, a fiber parametric optical
amplifier and the like can be also used. Furthermore, a dye
amplifier can be also used. Since the dye has a wider range of
amplification band as compared with the fiber amplifier or the
semiconductor optical amplifier, the use thereof enables
amplification of a wider band range of signals. In addition, the
optical amplification at a variety of wavelengths becomes possible,
depending on design of the dye.
[0398] Moreover, although the PIN-PD or the CCD camera is used as
the conversion means 130, the means is not limited thereto, and
APD, PMT, CMOS, EM-CCD or EB-CCD can be used, for example.
[0399] Although the fiber coupler or the multimode fiber coupler is
used as the multiplex means 140, the means is not limited thereto,
and a flat waveguide optical coupler, a spatial beam combiner, a
polarized wave synthesis coupler, a wavelength synthesis coupler
and the like, for example, can be also used.
[0400] Although the collective lens is used as the collecting
means, the means is not limited thereto, and a Gradient Index
(GRIN) lens, a lensed fiber or the like can be used, for
example.
[0401] Moreover, the invention can be effectively applied not only
to the imaging device, the endoscope and the like shown in the
above embodiments but also to the case in which the above optical
measurement method such as flow site meter, FCS, SPR, LPIA, HA or
the like is performed.
[0402] It is noted that, as explained in the above fifth to
seventeenth embodiments, the inventions according to the sixteenth
to the thirty-eighth aspects of the application have the following
effects.
[0403] Moreover, according to the invention of the sixteenth aspect
of the application, there is disposed the mode adjustment means
adjusting, by converting the energy mode distribution, incident
multimode electromagnetic waves to of a mode substantially equal to
the amplification spatial mode of the amplification means before
the amplification means and the conversion means, which makes it
possible to collect electromagnetic waves to be detected with high
efficiency even when they are scattered electromagnetic waves or
electromagnetic waves with distorted wavefront, thus enabling
electromagnetic wave detection at high speed and with high
sensitivity.
[0404] Furthermore, according to the invention of the seventeenth
aspect of the application, the mode adjust means reduces the number
of spatial modes of incident electromagnetic waves, which makes it
possible to reduce the number of spatial modes with small loss,
thus enabling electromagnetic amplification with high SNR by the
amplification means, in addition to the effects exerted by the
invention in claim 16.
[0405] Moreover, according to the invention of the eighteenth
aspect of the application, the energy ratio among spatial modes of
incident electromagnetic waves is varied, which can vary the energy
ratio among spatial modes, in addition to the effects exerted by
the invention in claim 16. Thus, a large amount of energy is
concentrated to a part of spatial modes, and the artificial
reduction of the number of spatial modes can be achieved.
[0406] Furthermore, according to the invention of the nineteenth
aspect of the application, the waveguide is used as the mode adjust
means, which can achieve variation of spatial modes with high
stability, in addition to the effects exerted by the invention in
claim 16.
[0407] Moreover, according to the invention of the twentieth aspect
of the application, the optical fiber is used as the waveguide,
which can stably achieve a long spatial-mode-adjustment waveguide,
in addition to the effects exerted by the invention in claim 19.
When the waveguide is longer, it becomes possible to adjust the
spatial mode adiabatically, thus enabling the spatial mode
adjustment with smaller loss. Moreover, the use of optical fiber
makes fine adjustment of the spatial optical system unnecessary,
thus improving the degree of freedom in use.
[0408] Furthermore, according to the invention of the twenty-first
aspect of the application, there is used, as the mode adjustment
means, the tapered optical fiber with a degree of freedom in design
being significantly high among optical fibers, which achieves the
mode adjustment means suitable for the condition of light to be
detected, in addition to the effects exerted by the invention in
claim 20. Moreover, the tapered fiber can be produced relatively
easily, which makes it possible to provide a low-cost
photodetection device.
[0409] Moreover, according to the invention of the twenty-second
aspect of the application, the variation of refractive-index,
stress or temperature is intentionally given into the optical
waveguide, which can induce the variation of energy ratio among
spatial modes, in addition to the effects exerted by the invention
in claim 19.
[0410] Furthermore, according to the invention of the twenty-third
aspect of the application, the optical fiber amplifier is used as
the amplification means, which enables optical amplification with
high gain and low noise, in addition to the effects exerted by the
invention in claim 16.
[0411] Moreover, according to the invention of the twenty-fourth
aspect of the application, the rare-earth-doped optical fiber
amplifier is used as the optical fiber amplifier, which enables
optical amplification with high gain, low noise and high
efficiency, in addition to the effects exerted by the invention in
claim 23.
[0412] Furthermore, according to the invention of the twenty-fifth
aspect of the application, the rare-earth-doped fluoride optical
fiber amplifier is used as the rare-earth-doped optical fiber
amplifier, which enables optical amplification in wavelength
regions where no operation is possible with the Silica optical
fiber amplifier, in addition to the effects exerted by the
invention in claim 24. Particularly, the efficient optical
amplification in visible bands becomes possible.
[0413] Moreover, according to the invention of the twenty-sixth
aspect of the application, there is used, as the fiber amplifier,
the optical fiber amplifier using stimulated Raman effects, which
enables optical amplification in any wavelength regions, in
addition to the effects exerted by the invention in claim 23.
[0414] Furthermore, according to the invention of the
twenty-seventh aspect of the application, the semiconductor optical
amplifier is used as the amplification means, which makes it
possible to constitute a compact and low-cost photodetection
system, in addition to the effects exerted by the invention in
claim 16.
[0415] Moreover, according to the invention of the twenty-eighth
aspect of the application, the optical amplifier including dye is
used as the amplification means, which makes it possible to amplify
a wider band range of signals, in addition to the effects exerted
by the invention in claim 16. Furthermore, the optical
amplification at a variety of wavelengths becomes possible,
depending on design of the dye.
[0416] Furthermore, according to the invention of the twenty-ninth
aspect of the application, the amplification means varies the gain
depending on the timing of incidence of incident electromagnetic
waves, which can prevent, in detecting intermittent signal light,
mixture of excessive noises by turning the optical amplifier on or
off in synchronization with the signal light, in addition to the
effects exerted by the invention in claim 16.
[0417] Moreover, according to the invention of the thirtieth aspect
of the application, the collecting means is used before the mode
adjust means, which can further increase the amount of incident
electromagnetic waves which can be detected, in addition to the
effects exerted by the invention in claim 16.
[0418] Furthermore, according to the invention of the thirty-first
aspect of the application, a plurality of collecting means is
provided, which makes it possible to collectively obtain incident
electromagnetic waves from a plurality of parts and thus further
increase the amount of incident electromagnetic waves which can be
detected, in addition to the effects exerted by the invention in
claim 16.
[0419] Moreover, according to the invention of the thirty-second
aspect of the application, the multiplex means collects incident
electromagnetic waves from a plurality of parts, which can reduce
the number of the subsequent mode adjustment means, amplification
means and conversion means, in addition to the effects exerted by
the invention in claim 31. Besides, incident electromagnetic waves
from a plurality of parts are collected, which can increase the
energy of incident electromagnetic waves input to the amplification
means.
[0420] Furthermore, according to the invention of the thirty-third
aspect of the application, there is disposed a plurality of mode
adjustment means adjusting, by converting the energy mode
distribution, incident multimode electromagnetic waves which are
incident in parallel to of a mode substantially equal to the
amplification spatial mode of the amplification means before the
amplification means and the conversion means, which makes it
possible to collect signal waves with high efficiency even when
incident electromagnetic waves are scattered electromagnetic waves
or electromagnetic waves with distorted wavefront, thus enabling
photodetection at high speed and with high sensitivity. In
addition, there is provided the multiplex means multiplexing a
plurality of electromagnetic waves output from a plurality of mode
adjustment means, which can further improve the operation stability
of the whole device when multiplexing electromagnetic waves with
the number of modes reduced.
[0421] Moreover, according to the invention of the thirty-fourth
aspect of the application, there is disposed a plurality of mode
adjustment means adjusting, by converting the energy mode
distribution, incident multimode electromagnetic waves which are
incident in parallel to of a mode substantially equal to the
amplification spatial mode of the amplification means before each
corresponding amplification means and conversion means, which makes
it possible to collect signal waves with high efficiency even when
incident electromagnetic waves are scattered electromagnetic waves
or electromagnetic waves with distorted wavefront, thus enabling
photodetection at high speed and with high sensitivity. In
addition, a plurality of mode adjustment means and a plurality of
amplification means corresponding thereto are provided, and
electromagnetic waves output from each of amplification means are
converted to electrical signals in parallel, which makes it
possible to simultaneously obtain information of a plurality of
points such as image information and the like.
[0422] Furthermore, according to the invention of the thirty-fifth
aspect of the application, incident multimode electromagnetic waves
are adjusted to of a mode substantially equal to the amplification
spatial mode at the amplification step by converting the energy
mode distribution, which makes it possible to collect the incident
electromagnetic waves with high efficiency even when they are
scattered electromagnetic waves or electromagnetic waves with
distorted wavefront, thus enabling photodetection at high speed and
with high sensitivity.
[0423] Moreover, according to the invention of the thirty-sixth
aspect of the application, electromagnetic waves to be detected
obtained from an organism are detected by the electromagnetic wave
detection device described in any one of claims 16 to 35, which
makes it possible to collect electromagnetic waves to be detected
with high efficiency even when they are scattered electromagnetic
waves or electromagnetic waves with distorted wavefront, thus
enabling observation of the organism through electromagnetic wave
detection at high speed and with high sensitivity.
[0424] Furthermore, according to the invention of the
thirty-seventh aspect of the application, there is provided the
electromagnetic wave detection device described in any one of
claims 16 to 35, which makes it possible to collect electromagnetic
waves to be detected with high efficiency even when they are
scattered electromagnetic waves or electromagnetic waves with
distorted wavefront, thus enabling microscope observation through
electromagnetic wave detection at high speed and with high
sensitivity.
[0425] Moreover, according to the invention of the thirty-eighth
aspect of the application, there is used the electromagnetic wave
detection device described in any one of claims 16 to 35, which
makes it possible to collect electromagnetic waves to be detected
with high efficiency even when they are scattered electromagnetic
waves or electromagnetic waves with distorted wavefront, thus
enabling generation of endoscope image through electromagnetic wave
detection at high speed and with high sensitivity.
[0426] There will be described an example in which the optical
detection device according to the first aspect of the application
is applied in the optical tomographic image generation device.
Before explaining the optical tomographic image generation device
according to the invention of the application, there will be
described a reference example of the optical tomographic image
generation device which has been developed together with the
invention of the application.
First Reference Example
[0427] FIG. 23 is a functional block diagram illustrating a
fundamental configuration of the optical tomographic image
generation device according to the first reference example of the
application. The optical tomographic image generation device has a
wavelength-variable light source unit 301 which can control the
wavelength of light to be emitted. The wavelength-variable light
source unit 301 is controlled by an image process unit 302 having a
personal computer through a wavelength control unit 303, so that
the wavelength-variable light source unit 301 emits light having a
smooth variation of light intensity and a wavelength varying with
time, as shown in FIG. 23.
[0428] The wavelength-variable light source unit 301 is connected
to one end of an optical multiplex-demultiplex unit 305. The
optical multiplex-demultiplex unit 305 demultiplexes light from the
wavelength-variable light source unit 301 to two, and causes one to
be incident, as reference light, on a reference-side optical
transmission unit 306 and the other to be incident, as inspection
light, on a inspection-side optical transmission unit 307. The
reference light incident on the reference-side optical transmission
unit 306 is emitted from the reference-side optical transmission
unit 306, passes through a lens 308 and is reflected by a light
reflection unit 309, thereafter the reflected reference light
passes through the lens 308 again, is transmitted through the
reference-side optical transmission unit 306 and incident on the
optical multiplex-demultiplex unit 305.
[0429] On the other hand, the inspection light demultiplexed by the
optical multiplex-demultiplex unit 305 and incident on the
inspection-side optical transmission unit 307 is emitted from the
inspection-side optical transmission unit 307 and passes through a
lens 310, thereafter an object to be inspected 311 such as an
organism or the like is irradiated with the light. The inspection
light with which the object to be inspected 311 has been irradiated
is reflected and scattered in the surface and the inside of the
object. With respect to the reflected and scattered inspection
light, one part thereof is rendered to pass through the lens 310
and is incident on the inspection-side optical transmission unit
307 again, thereafter it is transmitted through the inspection-side
optical transmission unit 307 and incident on the optical
multiplex-demultiplex unit 305 again.
[0430] The optical multiplex-demultiplex unit 305 multiplexes
reflected reference light and reflected inspection light incident
respectively from the reference-side optical transmission unit 306
and the inspection-side optical transmission unit 307 to generate
interference light such as one shown in FIG. 23. The interference
light generated by the optical multiplex-demultiplex unit 305 is
received by a photoelectric conversion unit 312 and
photoelectrically converted.
[0431] The photoelectric conversion signals output from the
photoelectric conversion unit 312 are provided to an analog signal
process unit 313, and the analog signal process unit 313 attenuates
low-frequency components of the photoelectric conversion signals
relative to high-frequency components thereof. That is, in the
analog signal process unit 313, a High-Pass Filter (HPF) or a
Band-Pass Filter (BPF) removes low-frequency components of the
photoelectric conversion signals, and a high-frequency amplifier
amplifies only high-frequency components or high-frequency
components are amplified while reducing low-frequency components,
for example. The analog output signals from the analog signal
process unit 313 are converted to digital signals by an
analog-digital (A/D) conversion unit 314 and provided to the image
process unit 302.
[0432] The image process unit 302 performs Fourier transformation
for digital output signals from the A/D conversion unit 314 and
converts the frequency to spatial distance. Therefore, the
information corresponds to optical signals reflected and scattered
in each depth position at which the inspection-side optical
transmission unit 307 irradiates the object to be inspected 311
with inspection light. The image process unit 302 obtains
information from each depth position, as described above, every
time a position of the object to be inspected 311 which the
inspection-side optical transmission unit 307 irradiates with
inspection light is varied, and generates a tomographic image of
the object to be inspected 311 based on such information to display
it on a display unit 315.
[0433] As above, before the A/D conversion unit 314 converts
photoelectric conversion signals of interference light of reflected
reference light and reflected inspection light obtained from the
photoelectric conversion device 312 to digital signals, the analog
signal process unit 313 attenuates low-frequency components
relative to high-frequency components, which can emphasize
information from deep portion of the object to be inspected 311.
Therefore, when analog output signals from the analog signal
process unit 313 are converted to digital signals by the A/D
conversion unit 314 later, it is possible to convert information
from the deep portion of the object to be inspected 311 to digital
signals with high accuracy without burying the information in
quantization noises, thus improving the penetration depth of a
tomographic image.
[0434] Next, a concrete embodiment of the first reference example
will be described with reference to the accompanying drawings.
[0435] FIG. 24 is a functional block diagram illustrating a
configuration of the optical tomographic image generation device
according to the first reference example of the invention. In the
embodiment, a Fourier domain mode locked laser (FDML) 321 is used
as the wavelength-variable light source unit. The FDML 321 is
constituted by a semiconductor optical amplifier (SOA), a fiber
Fabry-Perot wavelength tunable filter (FFPTF), an optical isolator,
a single-mode fiber (SMF) and an optical fiber coupler for output,
as disclosed in US 2006/0,187,537, for example. A plurality kinds
of SMF is used and the total length thereof is 4.3 km, and
wavelength distribution of the whole of a laser resonator is
arranged to be nearly zero.
[0436] In the embodiment, an image process unit 322 having a
personal computer controls FFPTF of an FDML 321 through a filter
control unit 323 so as to output, from the FDML 321, light having a
swept wavelength range of 1010 nm to 1090 nm, a repetition rate of
50 kHz and optical average power of about 5 mW.
[0437] The output end of the FDML 321 is connected to a first port
24a of an optical circulator 324 having the first port 24a to the
third port 24c. The optical circulator 324 outputs light input from
the first port 24a to the second port 24b, and outputs light input
from the second port 24b from the third port 24c.
[0438] The second port 324b of the optical circulator 324 is
connected to a first port 325a of a 3 dB coupler 325 as the optical
multiplex-demultiplex unit having a first port 325a to the fourth
port 325d, and the 3 dB coupler 325 demultiplexes light input to
the first port 325a to the third port 325c and the fourth port 325d
with an intensity ratio of 50:50 respectively.
[0439] The third port 325c of the 3 dB coupler 325 is connected to
a single-mode fiber (SMF) 326 as the reference-side optical
transmission unit, and light demultiplexed by the 3 dB coupler 325
is input to the SMF 326 as reference light. The SMF 326 is provided
with a polarization controller 327 along the path thereof to adjust
a polarization state of reference light. The reference light having
transmitted through the SMF 326 is converted to a parallel beam by
a lens 328 and emitted into the air, thereafter the emitted
reference light is attenuated by an optical attenuator 329 to have
a desired light intensity and then reflected by a reflective mirror
330. The reference light reflected by the reflective mirror 330 is
rendered to be incident on the SMF 326 through the optical
attenuator 329 and the lens 328, and input to the third port 325c
of the 3 dB coupler 325.
[0440] On the other hand, the fourth port 325d of the 3 dB coupler
325 is connected to an SMF 331 as the inspection-side optical
transmission unit, and light demultiplexed by the 3 dB coupler 325
is input to the SMF 331 as inspection light. The inspection light
having transmitted through the SMF 331 is converted to a parallel
beam by a lens 332 and emitted into the air, thereafter transmitted
direction of the emitted inspection light is two-dimensionally
scanned by a galvano scanner mirror 333 and collected by the lens
334 on the object to be inspected 335 such as an organism and the
like. The galvano scanner mirror 333 is controlled by the image
process unit 322 through a scanner driver 336. The inspection light
reflected and scattered in the surface or the inside of the object
to be inspected 335 is rendered to be transmitted, as reflected
inspection light, through the lens 334, the galvano scanner mirror
333, the lens 332 and the SMF 331 again and input to the fourth
port 325d of the 3 dB coupler 325.
[0441] The reflected reference light input to the third port 325c
of the 3 dB coupler 325 and the reflected inspection light input to
the fourth port 325d thereof are rendered to interfere with each
other at the 3 dB coupler 325, and output as interference light
from the first port 325a and the second port 325b. Here, the
interference light output from the first port 325a and the
interference light output from the second port 325b have a phase
opposite from each other.
[0442] The interference light output from the first port 325a of
the 3 dB coupler 325 passes through the second port 324b and the
third port 324c of the optical circulator 324 and is input to the
first port 337a of a Dual-balanced receiver 337 as the
photoelectric conversion unit. Moreover, the interference light
output from the second port 325b of the 3 dB coupler 325 is input
to the second port 337b of the dual-balanced receiver 337. Thus,
the dual-balanced receiver 337 photoelectrically converts
interference light input respectively to the first port 337a and
the second port 337b to obtain analog signals in which
direct-current components have been cancelled and only interference
components (alternating-current components) are existent. As the
dual-balanced receiver 337, there is used one having an electric
response band of 80 MHz, for example. It is noted that the
polarization controller 327 provided in the reference-side optical
transmission unit adjusts a polarization state of the reference
light so that analog signals obtained from the dual-balanced
receiver 337 are increased, that is, so that the reflected
reference light and the reflected inspection light appropriately
interfere with each other.
[0443] The analog signals output from the dual-balanced receiver
337 are input to a highpass filter (HPF) 338 as the analog signal
process unit so that low-frequency components thereof are removed.
The analog output signals from the HPF 338 are amplified by an
amplifier 339 by about 10 dB, and then input to the A/D conversion
unit 340 to be converted to digital signals. It is noted that there
is used, as the A/D conversion unit 340, one with 14 bits and 100
MS/s, for example.
[0444] The digital output signals from the A/D conversion unit 340
are input to the image process unit 322. The image process unit 322
performs Fourier transformation for digital output signals from the
A/D conversion unit 340 to calculate a power spectrum. The
frequency is converted from a wavelength swept rate of the FDML 321
to the spatial distance in a depth direction of the object to be
inspected 335, and the power is converted to the reflected and
scattered light intensity in each depth position in the object to
be inspected 335. As above, the image process unit 322 calculates
and obtains the distribution between the spatial distance and the
reflected and scattered light intensity in a depth direction, and
generates a tomographic image of the object to be inspected 335
based on such data to display it on a monitor 341.
[0445] Thus, in the embodiment, the photoelectric conversion
signals of interference light of the reflected reference light and
the reflected inspection light obtained from the dual-balanced
receiver 337 are input to the HPF 338 so that low-frequency
components thereof are removed, and analog output signals from
which the low-frequency components have been removed are amplified
by the amplifier 339 and converted to digital signals by the A/D
conversion unit 340, which makes it possible to convert information
from the deep portion of the object to be inspected 335 to digital
signals with emphasizing the information without burying it in
quantization noise, thus improving the penetration depth of a
tomographic image.
Eighteenth Embodiment
[0446] FIG. 25 is a functional block diagram illustrating a
configuration of the optical tomographic image generation device
according to the eighteenth embodiment of the invention. With
respect to the embodiment, in the first reference example, the
reflected inspection light obtained from the object to be inspected
335 is amplified and then rendered to interfere with the reflected
reference light. For this reason, with respect to the embodiment,
optical multiplex-demultiplex unit is constituted by a 3 dB coupler
345 for optical demultiplex wave and a 3 dB coupler 346 for optical
multiplex wave in the configuration shown in
[0447] FIG. 24. In the following description, the components having
a function same as of the component shown in FIG. 24 are
represented with the same reference symbols, and the description
thereof will be omitted.
[0448] In FIG. 25, the output end of the FDML 321 is connected to
the first port 345a of the 3 dB coupler 345 for optical demultiplex
wave, and the 3 dB coupler 345 demultiplexes light from the FDML
321 input to the first port 345a to the third port 345c and the
fourth port 345d with an intensity ratio of 50:50 respectively.
[0449] The third port 345c of the 3 dB coupler 345 is connected to
the first port 347a of an optical circulator 347, and reference
light from the 3 dB coupler 345 is output from the second port 347b
of the optical circulator 347. Moreover, the fourth port 345d of
the 3 dB coupler 345 is connected to the first port 348a of the
optical circulator 348, and inspection light from the 3 dB coupler
345 is output from the second port 348b of the optical circulator
348. It is noted that the second port 345b of the 3 dB coupler 345
is free.
[0450] The second port 347b of the reference-side optical
circulator 347 is connected to the SMF 326, and the polarization
state of reference light output from the second port 347b is
adjusted by the polarization controller 327, in the same way as in
the first reference example, thereafter the light passes through
the lens 328 and the optical attenuator 329 and is reflected by the
reflective mirror 330. The reflected reference light reflected by
the reflective mirror 330 is rendered to be incident on the SMF 326
again through the optical attenuator 329 and the lens 328, input to
the second port 347b of the optical circulator 347 and output from
the third port 347c thereof.
[0451] On the other hand, the second port 348b of the
inspection-side optical circulator 348 is connected to the SMF 331,
and the inspection light output from the second port 348b through
the SMF 331 passes through the lens 332, the galvano scanner mirror
333 and the lens 334 and is collected on the object to be inspected
335, in the same way as in the first reference example. With
respect to the inspection light reflected and scattered by the
object to be inspected 335 through irradiation for the object to be
inspected 335 with inspection light, one part thereof passes
through, as reflected inspection light, the lens 334, the galvano
scanner mirror 333, the lens 332 and the SMF 331 again and is input
to the second port 348b of the optical circulator 348 and output
from the third port 348c thereof.
[0452] In the embodiment, the reflected inspection light from the
object to be inspected 335 output from the third port 348c of the
optical circulator 348 is amplified by an optical amplifier 351 by
10 dB, for example. As the optical amplifier 351, there is used a
rare-earth-doped optical fiber amplifier using rare-earth-doped
optical fibers, an optical fiber amplifier using Silica optical
fibers such as the optical Raman amplifier or a semiconductor
optical amplifier.
[0453] The third port 347c of the reference-side optical circulator
347 is connected to the first port 346a of the 3 dB coupler 346 for
optical multiple wave. Moreover, the third port 348c of the
inspection-side optical circulator 348 is connected to the second
port 346b of the 3 dB coupler 346 for optical multiple wave.
[0454] Thus, in the 3 dB coupler 346 for optical multiple wave,
reflected reference light input to the first port 346a and the
reflected inspection light input to the second port 346b are
rendered to interfere with each other, and output from the third
port 346c and the fourth port 346d.
[0455] The third port 346c and the fourth port 346d of the 3 dB
coupler 346 are connected to the first port 337a and the second
port 337b of the dual-balanced receiver 337 respectively to obtain
analog signals in which direct-current components have been
cancelled by the dual-balanced receiver 337 and only interference
components (alternating-current components) are existent. The other
configurations and operations are the same as in the first
reference example.
[0456] According to the embodiment, the reflected inspection light
obtained from the object to be inspected 335 is amplified by the
optical amplifier 351 and then rendered to interfere with the
reflected reference light, which makes it possible to extract
information from the deep portion of the object to be inspected 335
and thus further improve the penetration depth of a tomographic
image.
Nineteenth Embodiment
[0457] FIG. 26 is a functional block diagram illustrating a
configuration of the optical tomographic image generation device
according to the nineteenth embodiment of the invention. With
respect to the embodiment, an optical band-pass filter (BPF) 352 is
disposed between the optical amplifier 351 and the second port 346b
of the 3 dB coupler 346 for optical multiplex wave in the
configuration of the eighteenth embodiment shown in FIG. 25. The
optical BPF 352 has a dielectric multilayer having a transmitted
wavelength bandwidth of 1 nm, for example, and is configured so
that the transmitted central wavelength is variable by changing an
angle of the dielectric multilayer relative to the incident light
axis. With respect to the optical BPF 352, the image process unit
322 controls the angle of the dielectric multilayer relative to the
incident light axis through the filter control unit 353, and varies
the transmitted central wavelength in synchronization with
variation with time of swept wavelength output from the FDML 321.
That is, the transmitted central wavelength of the optical BPF 352
is controlled to have the same wavelength as one swept and output
from the FDML 321. Since other configurations and operation are the
same as in the eighteenth embodiment, the same components having a
function same as of the components shown in FIG. 25 are represented
with the same reference symbols, and the description thereof will
be omitted.
[0458] Thus, in the embodiment, the reflected inspection light
obtained from the object to be inspected 335 is amplified by the
optical amplifier 351, thereafter the optical BPF 352 in which the
transmitted wavelength is variable allows only reflected inspection
light having a wavelength to be swept to pass therethrough, which
enables lower noise of the reflected inspection light to be
multiplexed with the reflected reference light. Therefore,
information from the deep portion of the object to be inspected 335
can be extracted with higher accuracy.
[0459] It is noted that, for the inventions of the application
disclosed in the eighteenth and nineteenth embodiments, many
variations and modifications can be implemented. For example, the
amplifier 339 can be disposed between the dual-balanced receiver
337 and the HPF 338. Moreover, the analog signal process unit is
not limited to the HPF 338 and can be constituted using the BPF.
Furthermore, in the first to third embodiments, there can be used,
instead of the HPF 338 and the amplifier 339, the high-frequency
amplifier having a low gain in a low-frequency band and a high gain
in a high-frequency band.
[0460] Moreover, according to the thirty-ninth aspect of the
application, as described in the above eighteenth and nineteenth
embodiments, the photoelectric conversion signals of interference
light of the reflected inspection light and the reflected reference
light though SSOCT are provided to the analog signal process unit
so that low-frequency components of the photoelectric conversion
signals are attenuated relative to high-frequency components, and
then the analog-digital conversion unit converts them to digital
signals so that a tomographic image is generated, which makes it
possible to convert information from the deep portion of the object
to be inspected such as an organism or the like to digital signals
with high accuracy without burying the information in quantization
noises, thus improving the penetration depth of the tomographic
image.
* * * * *