U.S. patent application number 14/505293 was filed with the patent office on 2015-04-09 for light source apparatus and endoscope system.
This patent application is currently assigned to FUJIFILM CORPORATION. The applicant listed for this patent is FUJIFILM Corporation. Invention is credited to Yoshinori MORIMOTO, Eiji OHASHI, Satoshi OZAWA.
Application Number | 20150099932 14/505293 |
Document ID | / |
Family ID | 51690211 |
Filed Date | 2015-04-09 |
United States Patent
Application |
20150099932 |
Kind Code |
A1 |
MORIMOTO; Yoshinori ; et
al. |
April 9, 2015 |
LIGHT SOURCE APPARATUS AND ENDOSCOPE SYSTEM
Abstract
A fluorescent type of green light source of a semiconductor in a
light source apparatus for an endoscope includes a blue excitation
light source device and green emitting phosphor. The blue
excitation light source device emits blue excitation light. The
green emitting phosphor is excited by the blue excitation light,
and emits green fluorescence. A dichroic filter in a dichroic
mirror cuts off the blue excitation light from an emission spectrum
of mixed light of the blue excitation light and green fluorescence
from the fluorescent type of green light source. Thus, illumination
light with the emission spectrum of a target can be stably supplied
without influence of the blue excitation light to a light amount of
blue light from a blue light source of a semiconductor.
Inventors: |
MORIMOTO; Yoshinori;
(Ashigarakami-gun, JP) ; OZAWA; Satoshi;
(Ashigarakami-gun, JP) ; OHASHI; Eiji;
(Ashigarakami-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIFILM Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
FUJIFILM CORPORATION
Tokyo
JP
|
Family ID: |
51690211 |
Appl. No.: |
14/505293 |
Filed: |
October 2, 2014 |
Current U.S.
Class: |
600/180 ; 257/89;
315/153; 315/294; 362/574 |
Current CPC
Class: |
A61B 1/0661 20130101;
G02B 6/0005 20130101; H01L 2224/48091 20130101; A61B 1/00057
20130101; A61B 1/0684 20130101; H01L 33/50 20130101; G03B 2215/0567
20130101; H01L 2224/48091 20130101; A61B 1/043 20130101; H01L
2924/00012 20130101; H01L 2924/181 20130101; H01L 2924/00014
20130101; H01L 27/15 20130101; A61B 1/0646 20130101; H01L
2224/49107 20130101; H01L 33/58 20130101; H05B 45/10 20200101; A61B
1/07 20130101; G02B 23/2469 20130101; A61B 1/0638 20130101; H01L
2924/181 20130101; A61B 1/0653 20130101; H01L 2924/00012 20130101;
H01L 2924/00014 20130101 |
Class at
Publication: |
600/180 ; 257/89;
315/153; 362/574; 315/294 |
International
Class: |
H01L 33/50 20060101
H01L033/50; A61B 1/06 20060101 A61B001/06; H05B 33/08 20060101
H05B033/08; F21V 8/00 20060101 F21V008/00; H01L 27/15 20060101
H01L027/15; H01L 33/58 20060101 H01L033/58 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 3, 2013 |
JP |
2013-208215 |
Claims
1. A light source apparatus for supplying a light guide device of
an endoscope with light, comprising: a blue semiconductor light
source for emitting blue light of a blue wavelength range; a
fluorescent type of a green semiconductor light source, having a
blue excitation light source device and green emitting phosphor,
said blue excitation light source device emitting blue excitation
light of a violet to blue wavelength range overlapping on said blue
wavelength range of said blue light, said green emitting phosphor
being excited by said blue excitation light for emitting green
fluorescence of a green wavelength range; a wavelength cut-off
filter component, disposed between said blue excitation light
source device and said light guide device, for cutting off said
blue excitation light.
2. A light source apparatus as defined in claim 1, further
comprising a path coupler for coupling two light paths from said
blue and green semiconductor light sources together.
3. A light source apparatus as defined in claim 2, wherein said
wavelength cut-off filter component is disposed on said path
coupler, or disposed between said path coupler and said green
semiconductor light source.
4. A light source apparatus as defined in claim 2, wherein said
path coupler includes optics disposed at an intersection point
between said two light paths; said wavelength cut-off filter
component is a dichroic filter formed on said optics.
5. A light source apparatus as defined in claim 1, further
comprising a driver for simultaneously driving said blue and green
semiconductor light sources for vessel enhancement imaging, to
output mixed light of said blue light and said green
fluorescence.
6. A light source apparatus as defined in claim 1, further
comprising a driver for alternately driving said blue and green
semiconductor light sources for vessel enhancement imaging,
sequentially to output said blue light and said green
fluorescence.
7. Alight source apparatus as defined in claim 1, further
comprising a driver, connected to said blue and green semiconductor
light sources, and changeable between simultaneous lighting and
field sequential lighting; wherein in said simultaneous lighting,
said driver simultaneously drives said blue and green semiconductor
light sources for vessel enhancement imaging, to output mixed light
of said blue light and said green fluorescence; in said field
sequential lighting, said driver alternately drives said blue and
green semiconductor light sources for vessel enhancement imaging,
sequentially to output said blue light and said green
fluorescence.
8. Alight source apparatus as defined in claim. 1, wherein said
blue semiconductor light source emits said blue light with a peak
wavelength of at least one of 405, 415, 430 and 460 nm.
9. Alight source apparatus as defined in claim. 1, further
comprising: a measurement sensor for measuring a light amount of
said blue light or said green fluorescence emitted by at least one
of said blue and green semiconductor light sources; an optical path
device for guiding part of said blue light or said green
fluorescence to said measurement sensor; a light source controller
for controlling power supplied to said blue or green semiconductor
light source according to a measurement result of said measurement
sensor.
10. Alight source apparatus as defined in claim 9, wherein said
measurement sensor and said optical path device are associated with
said green semiconductor light source, and said light source
controller adjusts said power supplied to said blue excitation
light source device according to said measurement result.
11. A light source apparatus as defined in claim 9, further
comprising a band pass filter, disposed upstream of said
measurement sensor, for receiving light emitted by said green
semiconductor light source and reflected by said optical path
device, and cutting off light with a wavelength different from said
green wavelength range of said green fluorescence.
12. A light source apparatus as defined in claim 9, wherein said
wavelength cut-off filter component is a wavelength cut-off filter
of a plate shape disposed between said green semiconductor light
source and said optical path device.
13. A light source apparatus as defined in claim 9, wherein said
optical path device includes a transparent glass plate, disposed
downstream of said blue or green semiconductor light source, for
reflecting said part of said blue light or said green fluorescence
by Fresnel reflection, to guide said part to said sensor.
14. A light source apparatus as defined in claim 1, further
comprising a rotatable disk having said green emitting phosphor
formed on a surface thereof; wherein said blue excitation light
source device emits said blue excitation light toward said
rotatable disk being rotated at an eccentric point thereof.
15. An endoscope system including an endoscope having a light guide
device for guiding light, and a light source apparatus for
supplying said light guide device with said light, said endoscope
system comprising: said light source apparatus including: a blue
semiconductor light source for emitting blue light of a blue
wavelength range; a fluorescent type of a green semiconductor light
source, having a blue excitation light source device and green
emitting phosphor, said blue excitation light source device
emitting blue excitation light of a violet to blue wavelength range
overlapping on said blue wavelength range of said blue light, said
green emitting phosphor being excited by said blue excitation light
for emitting green fluorescence of a green wavelength range; a
wavelength cut-off filter component, disposed between said blue
excitation light source device and said light guide device, for
cutting off said blue excitation light.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 USC 119 from
Japanese Patent Application No. 2013-208215, filed 3 Oct. 2013, the
disclosure of which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a light source apparatus
and endoscope system in which a fluorescent type of green
semiconductor light source is used, and illumination light of an
emission spectrum of a target for use in endoscopic imaging can be
stably obtained.
[0004] 2. Description Related to the Prior Art
[0005] Endoscopic imaging with an endoscope system is widely known
in the field of medical diagnosis. The endoscope system includes an
endoscope, a light source apparatus and a processing apparatus. The
light source apparatus supplies light to the endoscope. The
processing apparatus processes an image signal output by the
endoscope. The endoscope includes an elongated tube for entry in a
body cavity. A tip of the elongated tube has lighting windows and a
viewing window. The lighting windows apply the light to an object
of interest in the body cavity. The viewing window receives object
light from the object of interest for imaging. A light guide device
is incorporated in the endoscope, and includes a fiber bundle of a
plurality of optical fibers. The light guide device guides light
from the light source apparatus to the lighting windows. An image
sensor is disposed behind the viewing window, for example, CCD
image sensor. The object of interest illuminated with the light is
imaged by the image sensor, which outputs an image signal. The
processing apparatus generates a display image of the image signal.
A monitor display panel is driven to display the image, to observe
the object of interest in the body cavity.
[0006] Widely used examples of light sources in the light source
apparatus are a xenon lamp and halogen lamp for emitting normal
white light. JP-A 2007-068699 and U.S. Pat. Nos. 8,337,400 and
8,506,478 (corresponding to JP-A 2009-297290) disclose use of
semiconductor light sources such as laser diodes (LDs), light
emitting diodes (LEDs) and the like for the purpose of the
endoscopic imaging.
[0007] JP-A 2007-068699 discloses the light source apparatus, in
which the semiconductor light sources have three LEDs to emit light
of blue, green and red. Components of the light of blue, green and
red are combined to produce the white light.
[0008] In the xenon lamp and halogen lamp, a ratio between light
components of blue, green and red in the white light is constant
and cannot be adjusted. However, the semiconductor light sources of
blue, green and red are controllable for discretely adjusting light
amounts of the colors. Illumination light of plural types can be
produced easily with various spectra of emission.
[0009] Examples of the semiconductor light sources of green include
a green semiconductor light source having an element for emitting
green light itself, and a fluorescent type of a semiconductor light
source. The fluorescent type includes an excitation light source
device for emitting excitation light, and green emitting phosphor
excited by the excitation light for emitting green fluorescence.
For example, U.S. Pat. Nos. 8,337,400 and 8,506,478 disclose a
fluorescent type of green semiconductor light source having a blue
excitation light source device (blue LED) and green emitting
phosphor. The blue excitation light source device emits blue
excitation light in a violet to blue wavelength range. The green
emitting phosphor is excited by the blue excitation light for
emitting green fluorescence of a green wavelength range.
[0010] Among various products of LEDs available commercially, a
blue-violet LED for lighting in a violet to blue wavelength range
is usable more widely than a green LED for lighting in a green
wavelength range, because of such advantage that efficiency in the
light emission of the blue-violet LED is higher than the green LED,
and that its cost is lower. It is conceivable to use the
fluorescent type of green semiconductor light source disclosed in
U.S. Pat. Nos. 8,337,400 and 8,506,478 with a recently higher
concern than the semiconductor light sources or green LED for
emitting green light.
[0011] Furthermore, narrow band imaging with narrow band light
(special light) has been known recently in the field of the
endoscopic imaging. The narrow band light is light of a limited
wavelength range in contrast with the white light for imaging with
the entirety of a surface of body tissue or the object of interest.
In the narrow band imaging, depth of penetration of light into the
body tissue is characteristically different between plural
wavelengths. According to utilization of this characteristic,
vessel enhancement imaging is performed to enhance part of blood
vessels present in mucosa of the body tissue, as described in JP-A
2011-041758. A state of the blood vessels in abnormal tissue such
as a cancer is different from the normal tissue, so that the vessel
enhancement imaging is useful for discovering an early state of a
cancer in the diagnosis of cancer screening.
[0012] Examples of the semiconductor light sources disclosed in
JP-A 2011-041758 are a fluorescent type of white semiconductor
light source and a green semiconductor light source. The
fluorescent type of white semiconductor light source (white LED)
emits the white light with a continuous spectrum extending fully in
a visible light wavelength range. The green semiconductor light
source (green LED) emits light of a green wavelength range of
530-550 nm. A band pass filter is disposed downstream of the
fluorescent type of white semiconductor light source, and derives
light of a blue wavelength range of 390-445 nm from the white
light. In the vessel enhancement imaging, the semiconductor light
sources are turned on, so as to apply mixed light of the green
light and blue light, the green light being emitted by the green
semiconductor light source in the wavelength range of 530-550 nm,
the blue light being passed through the band pass filter in the
wavelength range of 390-445 nm upon emission of the white light
from the fluorescent type of white semiconductor light source. The
blue light of this wavelength range is highly absorbed by surface
blood vessels present on the epithelium (mucosa surface). The green
light of this wavelength range is highly absorbed by subsurface or
deep blood vessels disposed deeper than the surface blood vessels.
A display image with a high contrast between the blood vessels and
other tissue can be obtained.
[0013] It is conceivable to combine the structures of in JP-A
2007-068699 and U.S. Pat. Nos. 8,337,400 and 8,506,478 on the basis
of the light source apparatus of JP-A 2011-041758 for the purpose
of increasing the degree of freedom in the spectrum of the light.
According to JP-A 2007-068699, the semiconductor light sources of
blue, green and red are used for performing the vessel enhancement
imaging with blue light from the blue semiconductor light source
and green light from the green semiconductor light source.
According to U.S. Pat. Nos. 8,337,400 and 8,506,478, the
fluorescent type of green semiconductor light source is used for
the green light source. However, the combined construction of the
light source apparatus has a drawback in that illumination light of
an emission spectrum cannot be stably obtained as a target of the
vessel enhancement imaging. In relation to the fluorescent type of
green semiconductor light source, the blue excitation light is
largely absorbed by the green emitting phosphor. However, part of
the blue excitation light is not absorbed by the green emitting
phosphor, but passes the green emitting phosphor and becomes
emitted to the object of interest together with the green
fluorescence. Changing the light amount of the green light may
change a light amount of the blue excitation light. As a wavelength
range of the blue excitation light is overlapped on a wavelength
range of blue light emitted by the blue semiconductor light source,
the light amount of the blue light is influenced by the change in
the light amount of the green light.
[0014] In the endoscopic imaging, light amounts of light of blue,
green and red are controlled at a desired ratio in compliance with
the purpose of the imaging, to output illumination light of a
target spectrum. Assuming that color balance of a display image is
changed typically in the vessel enhancement imaging by a change in
the emission spectrum of the illumination light, a serious problem
arises in incorrectness in the endoscopic imaging. It is highly
important to stabilize the output of the illumination light of the
target spectrum. Also, exposure control in the imaging is
performed. In case the exposure amount of the entirety of the image
is too low (underexposure), the light amount of the illumination
light is raised. In case the exposure amount of the entirety of the
image is too high (overexposure), the light amount of the
illumination light is lowered.
[0015] In the exposure control for generating light of a spectrum
as a target for a predetermined ratio between light amounts of the
colors, it is necessary to increase or decrease the total of the
light amounts without changing the spectrum of the light. However,
in the use of the fluorescent type of green semiconductor light
source, changing the light amount of the green fluorescence by
increasing the output of the fluorescent type of green
semiconductor light source may influence to the light amount of the
blue light with the overlap of the wavelength range on that of the
blue excitation light. Thus, the spectrum will be changed in an
unwanted manner. For those reasons, it is impossible stably to
produce illumination light of the spectrum of the target in the use
of the fluorescent type of green semiconductor light source. There
is no known solution of this problem. It is conceivable to consider
an amount of the change in the blue excitation light according to
the change in the light amount of the green fluorescence, and to
adjust the light amount of the blue light with the overlap of the
wavelength range with the blue excitation light by use of the
amount of the change. However, control of lighting for this
conception will be very complicated and cannot be utilized
practically.
[0016] In the patent documents indicated above, there is no
description on the problem of difficulty in stably obtaining
illumination light with a spectrum of a target in use of the
fluorescent type of green semiconductor light source of the vessel
enhancement imaging. No solution of this problem is known in the
field of the endoscopic imaging.
SUMMARY OF THE INVENTION
[0017] In view of the foregoing problems, an object of the present
invention is to provide a light source apparatus and endoscope
system in which a fluorescent type of green semiconductor light
source is used, and illumination light of an emission spectrum of a
target for use in endoscopic imaging can be stably obtained.
[0018] In order to achieve the above and other objects and
advantages of this invention, a light source apparatus for
supplying a light guide device of an endoscope with light includes
a blue semiconductor light source for emitting blue light of a blue
wavelength range. A fluorescent type of a green semiconductor light
source has a blue excitation light source device and green emitting
phosphor, the blue excitation light source device emitting blue
excitation light of a violet to blue wavelength range overlapping
on the blue wavelength range of the blue light, the green emitting
phosphor being excited by the blue excitation light for emitting
green fluorescence of a green wavelength range. A wavelength
cut-off filter component is disposed between the blue excitation
light source device and the light guide device, for cutting off the
blue excitation light.
[0019] Preferably, furthermore, a path coupler couples two light
paths from the blue and green semiconductor light sources
together.
[0020] Preferably, the wavelength cut-off filter component is
disposed on the path coupler, or disposed between the path coupler
and the green semiconductor light source.
[0021] Preferably, the path coupler includes optics disposed at an
intersection point between the two light paths. The wavelength
cut-off filter component is a dichroic filter formed on the
optics.
[0022] Preferably, furthermore, a driver simultaneously drives the
blue and green semiconductor light sources for vessel enhancement
imaging, to output mixed light of the blue light and the green
fluorescence.
[0023] Preferably, furthermore, a driver alternately drives the
blue and green semiconductor light sources for vessel enhancement
imaging, sequentially to output the blue light and the green
fluorescence.
[0024] Preferably, furthermore, a driver is connected to the blue
and green semiconductor light sources, and changeable between
simultaneous lighting and field sequential lighting. In the
simultaneous lighting, the driver simultaneously drives the blue
and green semiconductor light sources for vessel enhancement
imaging, to output mixed light of the blue light and the green
fluorescence. In the field sequential lighting, the driver
alternately drives the blue and green semiconductor light sources
for vessel enhancement imaging, sequentially to output the blue
light and the green fluorescence.
[0025] Preferably, the blue semiconductor light source emits the
blue light with a peak wavelength of at least one of 405, 415, 430
and 460 nm.
[0026] Preferably, furthermore, a measurement sensor measures a
light amount of the blue light or the green fluorescence emitted by
at least one of the blue and green semiconductor light sources. An
optical path device guides part of the blue light or the green
fluorescence to the measurement sensor. A light source controller
controls power supplied to the blue or green semiconductor light
source according to a measurement result of the measurement
sensor.
[0027] Preferably, the measurement sensor and the optical path
device are associated with the green semiconductor light source,
and the light source controller adjusts the power supplied to the
blue excitation light source device according to the measurement
result.
[0028] Preferably, furthermore, a band pass filter is disposed
upstream of the measurement sensor, for receiving light emitted by
the green semiconductor light source and reflected by the optical
path device, and cutting off light with a wavelength different from
the green wavelength range of the green fluorescence.
[0029] In another preferred embodiment, the wavelength cut-off
filter component is a wavelength cut-off filter of a plate shape
disposed between the green semiconductor light source and the
optical path device.
[0030] Preferably, the optical path device includes a transparent
glass plate, disposed downstream of the blue or green semiconductor
light source, for reflecting the part of the blue light or the
green fluorescence by Fresnel reflection, to guide the part to the
sensor.
[0031] Preferably, furthermore, a rotatable disk has the green
emitting phosphor formed on a surface thereof. The blue excitation
light source device emits the blue excitation light toward the
rotatable disk being rotated at an eccentric point thereof.
[0032] Also, an endoscope system is provided, including an
endoscope having a light guide device for guiding light, and a
light source apparatus for supplying the light guide device with
the light. The light source apparatus includes a blue semiconductor
light source for emitting blue light of a blue wavelength range. A
fluorescent type of a green semiconductor light source has a blue
excitation light source device and green emitting phosphor, the
blue excitation light source device emitting blue excitation light
of a violet to blue wavelength range overlapping on the blue
wavelength range of the blue light, the green emitting phosphor
being excited by the blue excitation light for emitting green
fluorescence of a green wavelength range. A wavelength cut-off
filter component is disposed between the blue excitation light
source device and the light guide device, for cutting off the blue
excitation light.
[0033] Consequently, illumination light of an emission spectrum of
a target for use in endoscopic imaging can be stably obtained,
because the wavelength cut-off filter component cuts off a part of
the blue excitation light traveling in an unwanted manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The above objects and advantages of the present invention
will become more apparent from the following detailed description
when read in connection with the accompanying drawings, in
which:
[0035] FIG. 1 is an explanatory view in a perspective illustrating
an endoscope system;
[0036] FIG. 2 is a front elevation illustrating a tip of an
endoscope;
[0037] FIG. 3 is a block diagram schematically illustrating the
endoscope system;
[0038] FIG. 4 is a cross section illustrating a blue semiconductor
light source;
[0039] FIG. 5 is a cross section illustrating a green semiconductor
light source;
[0040] FIG. 6 is a graph illustrating a spectrum of light from the
blue light source;
[0041] FIG. 7 is a graph illustrating a spectrum of light from a
red semiconductor light source;
[0042] FIG. 8 is a graph illustrating spectra of blue excitation
light and green fluorescence of the green light source;
[0043] FIG. 9 is a graph illustrating an absorption spectrum of
hemoglobin;
[0044] FIG. 10 is a graph illustrating a scattering coefficient of
body tissue;
[0045] FIG. 11 is a graph illustrating a spectrum of illumination
light containing the blue light, green fluorescence and red
light;
[0046] FIG. 12 is a graph illustrating a spectrum of illumination
light containing the blue light and green fluorescence;
[0047] FIG. 13 is a graph illustrating a spectral characteristic of
micro color filters;
[0048] FIG. 14 is a timing chart illustrating lighting and imaging
according to normal imaging;
[0049] FIG. 15 is a timing chart illustrating lighting and imaging
according to vessel enhancement imaging;
[0050] FIG. 16 is a flow chart illustrating image processing in the
normal imaging;
[0051] FIG. 17 is a flow chart illustrating image processing in the
vessel enhancement imaging;
[0052] FIG. 18 is an explanatory view in a side elevation
illustrating the light sources and a path coupler;
[0053] FIG. 19 is a graph illustrating a transmission
characteristic of a dichroic filter in a first dichroic mirror;
[0054] FIG. 20 is a graph illustrating a transmission
characteristic of a dichroic filter in a second dichroic
mirror;
[0055] FIG. 21 is an explanatory view in a side elevation
illustrating a second preferred embodiment in which a first
dichroic mirror is disposed in a path coupler;
[0056] FIG. 22 is a graph illustrating a transmission
characteristic of the dichroic filter in the first dichroic
mirror;
[0057] FIG. 23 is an explanatory view in a side elevation
illustrating a third preferred embodiment with a wavelength cut-off
filter;
[0058] FIG. 24 is a graph illustrating a transmission
characteristic of the wavelength cut-off filter;
[0059] FIG. 25 is an explanatory view in a side elevation
illustrating a fourth preferred embodiment with measurement sensors
for light amounts;
[0060] FIGS. 26 and 27 are graphs illustrating transmission
characteristics of filters disposed upstream of the green and red
measurement sensors;
[0061] FIG. 28 is a block diagram schematically illustrating light
amount control with the measurement sensors;
[0062] FIG. 29 is an explanatory view in a side elevation
illustrating a path coupler having the measurement sensors;
[0063] FIG. 30 is an explanatory view in a side elevation
illustrating a fifth preferred embodiment having first and second
blue semiconductor light sources;
[0064] FIGS. 31 and 32 are graphs illustrating spectra of first and
second blue light from the first and second blue light sources;
[0065] FIG. 33 is a graph illustrating a spectrum of white
light;
[0066] FIGS. 34 and 35 are graphs illustrating spectra of
illumination light containing the first and second blue light and
the green fluorescence;
[0067] FIG. 36 is a graph illustrating a transmission
characteristic of a dichroic filter in a third dichroic mirror;
[0068] FIG. 37 is a timing chart illustrating lighting and imaging
according to the normal imaging;
[0069] FIGS. 38 and 39 are timing charts illustrating lighting and
imaging according to the vessel enhancement imaging of mucosal
blood vessels and according to the vessel enhancement imaging of
subsurface blood vessels;
[0070] FIG. 40 is a graph illustrating a transmission
characteristic of a wavelength cut-off filter;
[0071] FIG. 41 is a perspective view illustrating a sixth preferred
embodiment with a green semiconductor light source;
[0072] FIG. 42 is a timing chart illustrating lighting and imaging
according to the vessel enhancement imaging and field sequential
lighting.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE PRESENT
INVENTION
[0073] In FIG. 1, an endoscope system 10 includes an endoscope 11,
a processing apparatus 12, a light source apparatus 13 and a
monitor display panel 14. The endoscope 11 images an object of
interest or body tissue. The processing apparatus 12 receives an
image signal from the endoscope 11 and produces an image of the
object of interest. The light source apparatus 13 supplies light of
illumination to the endoscope 11. The display panel 14 displays the
image from the processing apparatus 12. A user input interface 15
is connected to the processing apparatus 12, inclusive of a
keyboard, mouse and other input devices.
[0074] The endoscope system 10 is changeable between a normal
imaging mode for imaging an object of interest, and a vessel
enhancement imaging mode for enhancing and imaging blood vessels
present in mucosa as object of interest. In the vessel enhancement
imaging mode, a pattern of blood vessels is recorded as blood
vessel information, for use in diagnosis of a benign or malignant
tumor. In the vessel enhancement imaging mode, the object of
interest is illuminated with light containing components of a
particular wavelength range having a high absorption coefficient in
relation to hemoglobin in blood. In the normal imaging mode, a
normal multi-color image is produced with suitability for general
diagnosis of the object of interest. In the vessel enhancement
imaging mode, a vessel enhancement image is produced with
suitability for diagnosing the pattern of blood vessels.
[0075] The endoscope 11 includes an elongated tube 16, a grip
handle 17 and a universal cable 18. The elongated tube 16 is
entered in a body cavity of a patient, for example,
gastrointestinal tract. The grip handle 17 is disposed at a
proximal end of the elongated tube 16. The universal cable 18
connects the endoscope 11 to the processing apparatus 12 and the
light source apparatus 13.
[0076] The elongated tube 16 includes a tip device 19, a steering
device 20 and a flexible device 21 arranged in a proximal
direction. In FIG. 2, various elements are disposed on an end
surface of the tip device 19, including lighting windows 22, a
viewing window 23, a nozzle spout 24 for washing fluid, and a
distal instrument opening 25. The lighting windows 22 apply
illumination light to an object of interest. The viewing window 23
receives image light from the object of interest. The nozzle spout
24 supplies air or water to clean up the viewing window 23. The
distal instrument opening 25 is used to protrude a medical
instrument such as a forceps, electrocautery device and the like
for treatment of various types. An image sensor 56 and an objective
lens 60 are disposed behind the viewing window 23. See FIG. 3.
[0077] The steering device 20 is constituted by a plurality of link
elements connected serially. Steering wheels 26 are disposed on the
grip handle 17, and rotated to bend the steering device 20 up and
down and to the right and left. The tip device 19 is directed in a
desired direction by steering of the steering device 20. The
flexible device 21 is flexible for entry in a body cavity of a
tortuous shape, for example, esophagus or intestines in a
gastrointestinal tract. A communication cable, a light guide device
55 and the like are extended through the elongated tube 16 as
illustrated in FIG. 3. The communication cable transmits a drive
signal for driving the image sensor 56, and an image signal output
by the image sensor 56. The light guide device 55 transmits light
from the light source apparatus 13 to the lighting windows 22.
[0078] The grip handle 17 includes a proximal instrument opening
27, fluid supply buttons 28 and a release button (not shown) in
addition to the steering wheels 26. The proximal instrument opening
27 receives entry of a medical instrument for treatment. The fluid
supply buttons 28 are depressed for supplying air or water through
the nozzle spout 24. The release button is depressible for forming
a still image.
[0079] A tube for the universal cable 18 contains the communication
cable, the light guide device 55 and the like extending from the
elongated tube 16. A composite connector 29 is disposed at a
proximal end of the universal cable 18 on a side of the processing
apparatus 12 and the light source apparatus 13. The composite
connector 29 includes a cable connector plug 29a and a light source
connector plug 29b. Those are coupled to respectively the
processing apparatus 12 and the light source apparatus 13 in a
removable manner. A proximal end of the communication cable is
contained in the cable connector plug 29a. An entrance end 55a of
the light guide device 55 of FIG. 3 is contained in the light
source connector plug 29b.
[0080] In FIG. 3, the light source apparatus 13 includes a light
source unit 40, a path coupler 41 and a light source controller 42.
The light source unit 40 includes a blue light source 35, a
fluorescent type of green light source 36 and a red light source 37
as semiconductor light sources. The path coupler 41 couples light
paths of the B, G and R light sources 35-37 together. The light
source controller 42 controls the B, G and R light sources
35-37.
[0081] The blue light source 35 includes a blue LED 43 (light
emitting diode) for emitting light of a blue wavelength range. The
red light source 37 includes a red LED 45 (light emitting diode)
for emitting light of a red wavelength range. Furthermore, the
green light source 36 includes a blue excitation light source
device 44 or light source LED (light emitting diode), and green
emitting phosphor 47. The blue excitation light source device 44
emits blue excitation light of a violet to blue wavelength range.
The green emitting phosphor 47 is excited by the blue excitation
light, and emits green fluorescence of a green wavelength
range.
[0082] Each of the LEDs 43-45 has a p-type semiconductor and an
n-type semiconductor attached together as is well-known in the art.
Upon application of voltage, recombination of a positive hole and
an electron occurs across the band gap at the p-n junction, for a
current to flow. Light is emitted by generation of energy according
to the band gap. A light amount emitted by the LEDs 43-45 is
increased by an increase in supplied power. In the green light
source 36 as a combination of the blue excitation light source
device 44 and the green emitting phosphor 47, a light amount of the
green fluorescence is increased by an increase in a light amount of
the blue excitation light from the blue excitation light source
device 44.
[0083] In FIG. 4, the blue light source 35 includes a semiconductor
substrate 35a or semiconductor die, a cavity mold 35b and resin
encapsulant 35c. On the semiconductor substrate 35a, the blue LED
43 is mounted. The cavity mold 35b is formed in the semiconductor
substrate 35a, and has a cavity for containing the blue LED 43. The
resin encapsulant 35c is filled in the cavity for encapsulation. An
inner surface of the cavity is a reflector for reflecting light.
Light diffusing material is mixed with and dispersed in the
semiconductor substrate 35a for diffusing light. An LED wire 35d
extends from the blue LED 43 to the semiconductor substrate 35a for
connection with conductivity. In the technical field of the LED,
this type of mounting of the blue light source 35 is referred to as
a surface mounting type. Note that, in the red light source 37, the
structure of the blue light source 35 is repeated. Details of the
red light source 37 are not described herein.
[0084] In FIG. 5, the green light source 36 of the fluorescent type
includes a semiconductor substrate 36a or semiconductor die, and a
cavity mold 36b, and is packaged with the blue excitation light
source device 44 in the surface mounting type, in a manner similar
to the blue and red light sources 35 and 37. The green light source
36 is different from the blue and red light sources 35 and 37 in
that the green emitting phosphor 47 is contained in the cavity of
the cavity mold 36b. The green emitting phosphor 47 in the blue
excitation light source device 44 is dispersed in resin
encapsulant, and includes dispersed materials such as phosphor,
light diffusing material and the like. An LED wire 36d is disposed
to connect the semiconductor substrate 36a to the blue excitation
light source device 44.
[0085] In FIG. 6, the blue LED 43 emits blue light LB of which a
wavelength range is 390-445 nm of violet to blue colors, and a peak
wavelength is 430 plus or minus 10 nm. In FIG. 7, the red LED 45
emits red light LR of which a wavelength range is 615-635 nm of a
red color, and a peak wavelength is 620 plus or minus 10 nm.
[0086] In FIG. 8, the green light source 36 emits mixed light
(LBe+LGf) of blue excitation light LBe from the blue excitation
light source device 44 and green fluorescence LGf emitted by the
green emitting phosphor 47 excited by the blue excitation light
LBe. The blue excitation light LBe has a violet to blue wavelength
range of 420-440 nm and a peak wavelength of 430 plus or minus 10
nm. The green fluorescence LGf has a green wavelength range of
500-600 nm and a peak wavelength of 520 plus or minus 10 nm. The
peak wavelength of the blue excitation light LBe is equal to that
of the blue light LB emitted by the blue light source 35. The
wavelength range of the blue excitation light LBe is overlapped
with that of the blue light LB. See FIG. 19.
[0087] The green emitting phosphor 47 absorbs a large part of the
blue excitation light LBe to emit the green fluorescence LGf. A
remaining part of the blue excitation light LBe passes the green
emitting phosphor 47 without absorption. A spectrum of light
emitted by the green light source 36, as illustrated in the
drawing, contains a component of the passed part of the blue
excitation light LBe through the green emitting phosphor 47 and a
component of the green fluorescence LGf.
[0088] In FIG. 9, an absorption spectrum of hemoglobin in blood is
illustrated. An absorption coefficient .mu.a has dependency to the
wavelength, namely increases abruptly in a wavelength range equal
to or lower than 450 nm, and comes to a peak at approximately 405
nm. Also, the absorption coefficient comes to a smaller peak at a
wavelength of 530-560 nm. In case light of a wavelength range with
a high value of the absorption coefficient .mu.a is applied to body
tissue or an object of interest, an image with a difference in the
contrast between blood vessels and other tissue can be obtained,
because the light is largely absorbed by the blood vessels.
[0089] In FIG. 10, a scattering characteristic of body tissue to
light also has dependency to the wavelength. A scattering
coefficient .mu.S increases according to smallness of the
wavelength. The scattering influences a depth of penetration of
light into the body tissue. An amount of light reflected in the
vicinity of the epithelium (mucosa surface) of the body tissue is
high according to highness of the scattering, so as to decrease an
amount of light reaching a portion of a medium depth or large depth
(lamina propria or muscularis mucosae). Accordingly, the depth of
penetration decreases according to the smallness of the wavelength,
and increases according to greatness of the wavelength. A
wavelength of light for the vessel enhancement is selected
according to the absorption characteristic of hemoglobin and
scattering characteristic of body tissue to light.
[0090] The blue light LB with the peak wavelength of 430 plus or
minus 10 nm from the blue LED 43 has a relatively small depth of
penetration with a relatively short wavelength. Absorption of the
blue light LB in surface blood vessels is large. Thus, the blue
light LB is used for enhancement of surface blood vessels. It is
possible to obtain a vessel enhancement image in which surface
blood vessels are expressed with high contrast by use of the blue
light LB. Also, green fluorescence LGf with the peak wavelength of
520 plus or minus 10 nm is used for enhancement of subsurface or
deep blood vessels. In FIG. 9 for the absorption spectrum, the
absorption coefficient changes gradually in a green wavelength
range of 530-560 nm in comparison with a blue wavelength range
equal to or less than 450 nm. There is no requirement of narrow
band light for the purpose of enhancement of subsurface or deep
blood vessels in a manner different from the blue light LB. Thus, a
green image signal after color separation with a micro color filter
of green in the image sensor 56 is used for enhancement of the
subsurface or deep blood vessels, as will be described later.
[0091] In FIG. 3, drivers 50, 51 and 52 are connected to
respectively the LEDs 43-45. The light source controller 42
controls the drivers 50-52 to turn on and off the LEDs 43-45 and
adjust their light amounts. According to an exposure control signal
from the processing apparatus 12, the light source controller 42
adjusts the light amounts by changing power supplied to the LEDs
43-45.
[0092] The drivers 50-52 are controlled by the light source
controller 42, and turn on respectively the LEDs 43-45 by
application of drive currents. In response to the exposure control
signal from the processing apparatus 12, the drivers 50-52 change
the current values to adjust power for the LEDs 43-45, so that
light amounts of the blue light LB, green fluorescence LGf and red
light LR are controlled. Control of the light amount of the green
fluorescence LGf is performed by controlling a light amount of the
blue excitation light LBe from the blue excitation light source
device 44. In case an operator wishes an increase of the light
amount of the green fluorescence LGf, the current value from the
driver 51 to the blue excitation light source device 44 is
increased to increase the light amount of the blue excitation light
LBe. Note that various methods of supplying a drive current can be
used, such as controls of PAM (pulse amplitude modulation) and PWM
(pulse width modulation). In the PAM, an amplitude of a pulse of
the drive current is changed. In the PWM, a duty factor of the
pulse of the drive current is changed.
[0093] The path coupler 41 couples light paths of light from the B,
G and R light sources 35-37 together into one light path. There is
a receptacle connector 54 for connection of the light source
connector plug 29b. A distal end of the path coupler 41 is disposed
near to the receptacle connector 54. The path coupler 41 receives
the light from the B, G and R light sources 35-37 and outputs the
light toward the entrance end 55a of the light guide device 55 in
the endoscope 11. Protectors (not shown) of glass are associated
with respectively the light source connector plug 29b and the
receptacle connector 54.
[0094] In FIG. 11, a spectrum of mixed light of the blue light LB,
green fluorescence LGf and red light LR from the B, G and R light
sources 35-37 at a point downstream of the path coupler 41 is
illustrated. The mixed light is white light with the continuous
spectrum fully extending in a visible light range, and used as
illumination light LW0 in the normal imaging mode. In the vessel
enhancement imaging mode, illumination light LW1 is applied to an
object of interest as mixed light of the blue light LB and green
fluorescence LGf. See FIG. 12. A second dichroic mirror 80 of FIG.
18 cuts off the blue excitation light LBe, so that no component of
the blue excitation light LBe is contained in a spectrum of the
illumination light LW0 and LW1. Note that the spectra of the
illumination light LW0 and LW1 in FIGS. 11 and 12 are only
examples. Spectra of the illumination light LW0 and LW1 can be
changed suitably as target according to color balance of a display
image or the like. For example, a ratio between light amounts of
the blue light LB, green fluorescence LGf and red light LR (ratio
between current values of drive currents for the LEDs 43-45) is
adjusted to produce the illumination light LW0 and LW1 with a
spectrum of the target.
[0095] The light source controller 42 controls the exposure of the
light of illumination by maintaining the spectrum of light emission
as a target. Should a ratio of light amounts of the colors be
changed within the light of illumination, color balance of a
display image may change with a change in the spectrum of the light
emission. Thus, the light source controller 42 discretely changes a
current value of driving the LEDs 43-45 by controlling the drivers
50-52, to increase or decrease the light amounts of the colors.
[0096] The light source controller 42 changes the spectrum of light
between the normal imaging mode and the vessel enhancement imaging
mode. For example, the light source controller 42 sets the ratio of
the light amount of the blue light LB higher in the vessel
enhancement imaging mode than in the normal imaging mode, so as to
use the blue light LB with higher importance than the green
fluorescence LGf.
[0097] In FIG. 3, the endoscope 11 includes the light guide device
55, the image sensor 56, an analog processing unit 57 or analog
front end (AFE), and an imaging control unit 58. The light guide
device 55 is a fiber bundle constituted by bundling plural optical
fibers. Upon coupling the light source connector plug 29b to the
light source apparatus 13, the entrance end 55a of the light guide
device 55 in the light source connector plug 29b is aligned with an
exit end of the path coupler 41. A distal exit end of the light
guide device 55 inside the tip device 19 has two branches for
transmitting light to the lighting windows 22.
[0098] A lighting lens 59 is disposed behind each of the lighting
windows 22. Illumination light from the light source apparatus 13
is guided by the light guide device 55 to the lighting lens 59, and
applied through the lighting windows 22 to an object of interest.
The lighting lens 59 is a concave lens and enlarges a divergence
angle of light from the light guide device 55. The illumination
light can be applied to a wide area in a body cavity with the
object of interest.
[0099] The objective lens 60 and the image sensor 56 are disposed
behind the viewing window 23. Image light from the object of
interest enters the objective lens 60 through the viewing window
23, and is focused on an imaging surface 56a of the image sensor 56
by the objective lens 60.
[0100] Examples of the image sensor 56 are a CCD image sensor and
CMOS image sensor. A plurality of photoconductive elements or
photoconductors are arranged as pixels of arrays on the imaging
surface 56a, for example, photo diodes. The image sensor 56
photoelectrically converts light received by the imaging surface
56a, and stores signal charge according to light amounts of light
received by the pixels. The signal charge is converted by an
amplifier into a voltage signal, which is read out. The voltage
signal is transmitted by the image sensor 56 to the analog
processing unit 57 as an image signal.
[0101] The analog processing unit 57 is constituted by a correlated
double sampler (CDS), auto gain controller (AGC) and A/D converter
(all not shown). The correlated double sampler processes the image
signal of an analog form from the image sensor 56 in the correlated
double sampling, and removes electric noise due to reset of the
signal charge. The auto gain controller amplifies the image signal
after removal of the noise in the correlated double sampler. The
A/D converter converts the amplified image signal from the auto
gain controller into a digital image signal having a gradation
value according to a predetermined bit number, and sends the
digital image signal to the processing apparatus 12.
[0102] A controller 65 in the processing apparatus 12 is connected
with the imaging control unit 58, which supplies the image sensor
56 with a drive signal according to a clock signal from the
controller 65 as a reference. The image sensor 56 generates an
image signal at a predetermined frame rate according to the drive
signal from the imaging control unit 58, and sends the image signal
to the analog processing unit 57.
[0103] The image sensor 56 is a color image sensor. The imaging
surface 56a of the image sensor 56 has a great number of micro
color filters of blue, green and red with spectral characteristics
in FIG. 13 in correspondence with pixels. An example of arrangement
of the micro color filters is a Bayer arrangement.
[0104] The B pixels with the B filters are sensitive to light of a
wavelength of approximately 380-560 nm. The G pixels with the G
filters are sensitive to light of a wavelength of approximately
450-630 nm. The R pixels with the R filters are sensitive to light
of a wavelength of approximately 580-800 nm. Reflected light
corresponding to the blue light LB is mainly received by the B
pixels. Reflected light corresponding to the green fluorescence LGf
is mainly received by the G pixels. Reflected light corresponding
to the red light LR is mainly received by the R pixels. The blue
excitation light LBe does not travel to the object of interest
because cut off by the second dichroic mirror 80. Assuming that the
blue excitation light LBe illuminates the object, reflected light
from the object is sensed by the B pixels.
[0105] In FIGS. 14 and 15, the image sensor 56 operates for the
storing and readout in a period of acquiring one frame, and in the
storing, stores signal charge in pixels, and in the readout, reads
out the stored signal charge. In FIG. 14, the B, G and R light
sources 35-37 in the normal imaging mode are turned on according to
a time point of the storing of the image sensor 56, to apply the
illumination light LW0 (LB+LGf+LR) to an object of interest, the
illumination light LW0 being mixture of the blue light LB, green
fluorescence LGf and red light LR. Object light or reflected light
becomes incident upon the image sensor 56. The image sensor 56
separates the reflected light of the illumination light LW0 with
the micro color filter. Blue pixels receive reflected light derived
from the blue light LB. Green pixels receive reflected light
derived from the green fluorescence LGf. Red pixels receive
reflected light derived from the red light LR. The image sensor 56
sequentially outputs image signals B, G and R of one frame
according to pixel values of the blue, green and red pixels at a
time point of the readout and with the frame rate. The imaging
sequence is repeated while the normal imaging mode is set.
[0106] In FIG. 15, the blue and green light sources 35 and 36 in
the vessel enhancement imaging mode are turned on according to a
time point of the storing of the image sensor 56, to apply
illumination light LW1 (LB+LGf) to the object of interest, the
illumination light LW1 being mixture of the blue light LB and green
fluorescence LGf.
[0107] The illumination light LW1 is separated by the micro color
filters in the image sensor 56 in a manner similar to the normal
imaging mode. The B and G pixels receive reflected light derived
from the blue light LB and from the green fluorescence LGf in a
manner similar to the normal imaging mode. The image sensor 56
outputs image signals B, G and R sequentially in a sequence of
readout in the vessel enhancement imaging mode. Those steps of the
imaging are repeated while the vessel enhancement imaging mode is
set.
[0108] In FIG. 3, the processing apparatus 12 includes a digital
signal processor 66 (DSP), an image processing unit 67, a frame
memory 68 and a display control unit 69 together with the
controller 65. The controller 65 has a CPU with a ROM and a RAM.
The ROM stores control programs and control data. The RAM is a
working memory for loading of the control programs. The CPU runs
the control programs to control various elements in the processing
apparatus 12.
[0109] The digital signal processor 66 acquires an image signal
output by the image sensor 56. The digital signal processor 66
separates the image signal of the mixture for blue, green and red
pixels into image signals of blue, green and red. The image signals
of the colors are interpolated in the operation of pixel
interpolation. The digital signal processor 66 performs signal
processing of various functions, such as gamma correction, white
balance correction and the like for the image signals of blue,
green and red.
[0110] The digital signal processor 66 determines an exposure
amount according to the image signals B, G and R. Should the
exposure amount of the entirety of the image be too low
(underexposure), the digital signal processor 66 outputs a control
signal to the controller 65 to raise the light amount of the
illumination light. Should the exposure amount of the entirety of
the image be too high (overexposure), the digital signal processor
66 outputs a control signal to the controller 65 to lower the light
amount of the illumination light. The controller 65 sends the
control signal to the light source controller 42 of the light
source apparatus 13.
[0111] The frame memory 68 stores image data output by the digital
signal processor 66, processed image data from the image processing
unit 67, and the like. The display control unit 69 reads out the
processed image data from the frame memory 68, converts this into a
video signal such as a composite signal, component signal or the
like, which is output to the display panel 14.
[0112] In FIG. 16, the image processing unit 67 in the normal
imaging mode generates a normal image according to the image
signals B, G and R after color separation by the digital signal
processor 66. The normal image is output to the display panel 14.
The image processing unit 67 updates the normal image at each time
that the image signals B, G and R in the frame memory 68 are
updated.
[0113] In FIG. 17, the image processing unit 67 generates a vessel
enhancement image according to image signals B and G in the vessel
enhancement imaging mode. The image signal B in the vessel
enhancement imaging mode includes a component of reflected light
derived from the blue light LB having a wavelength of 390-445 nm
and a peak wavelength of 430 plus or minus 10 nm. Thus, the surface
blood vessels can be expressed at a high contrast. It is medically
known that there is a characteristic pattern of the particular
surface blood vessels in body tissue of a cancer, malignant tumor
or other lesions, because higher vessel density of the particular
surface blood vessels is found than normal body tissue. It is
preferable to express the particular surface blood vessels
distinctly with advantages for the diagnosis of a benign or
malignant tumor.
[0114] It is also possible to extract an area of the surface blood
vessels within the endoscopic image according to the image signal
B, and process the area of the surface blood vessels in edge
enhancement as processing well-known in the art. The image signal B
after the edge enhancement is combined with the image signal G, to
produce a vessel enhancement image. Also, an area of subsurface or
deep blood vessels can be processed in the edge enhancement in
addition to the surface blood vessels. To this end, an area of the
subsurface or deep blood vessels is extracted from the image signal
G containing much information of the subsurface or deep blood
vessels, and is processed in the edge enhancement. A vessel
enhancement image is produced according to the image signal G after
the edge enhancement and the image signal B.
[0115] The image processing unit 67 generates the vessel
enhancement image at each time that the image signals B and G in
the frame memory 68 are updated. The display control unit 69
allocates the image signal B to the B and G channels of the display
panel 14, and the image signal G to the R channel of the display
panel 14, and drives the display panel 14 to display the vessel
enhancement image in a form of pseudo color.
[0116] In FIG. 18, the path coupler 41 includes collimator lenses
75, 76 and 77, a first dichroic mirror 79, the second dichroic
mirror 80 and a condenser lens 82. The collimator lenses 75-77
collimate light of the colors from respectively the B, G and R
light sources 35-37. The condenser lens 82 condenses light from the
path coupler 41 to the entrance end 55a of the light guide device
55. Each of the first and second dichroic mirrors 79 and 80 is
optics including a transparent glass plate and a layer of a
dichroic filter formed on the glass plate with a predetermined
transmission characteristic.
[0117] The green light source 36 is so disposed that its light path
is aligned with an optical axis of the light guide device 55. The
light paths of the green and red light sources 36 and 37 are
perpendicular with one another. The first dichroic mirror 79 is
positioned at a point of the intersection between the light paths
of the green and red light sources 36 and 37. Also, the light paths
of the blue and green light sources 35 and 36 are perpendicular
with one another. The second dichroic mirror 80 is positioned at a
point of the intersection between the light paths of the blue and
green light sources 35 and 36. The first dichroic mirror 79 is
oriented with an inclination of 45 degrees with respect to the
light paths of the green and red light sources 36 and 37. The
second dichroic mirror 80 is oriented with an inclination of 45
degrees with respect to the light paths of the blue and green light
sources 35 and 36.
[0118] In FIG. 19, the dichroic filter of the first dichroic mirror
79 has a transmission characteristic of reflecting light of a red
wavelength range equal to or more than approximately 600 nm and
passing light of a blue to green wavelength range less than the
same. The first dichroic mirror 79 passes the mixed light of the
blue excitation light LBe and green fluorescence LGf from the green
light source 36 through the collimator lens 76, and reflects the
red light LR from the red light source 37 through the collimator
lens 77. Thus, a light path of the mixed light of the blue
excitation light LBe and green fluorescence LGf is combined with
that of the red light LR for coupling.
[0119] A dichroic filter in the second dichroic mirror 80 has a
transmission characteristic of cutting off at least the blue
excitation light LBe from a spectrum of mixed light of the blue
excitation light LBe and green fluorescence LGf downstream of the
green light source 36 as illustrated in FIG. 8. In short, the
dichroic filter in the second dichroic mirror 80 operates as an
excitation light cut-off filter (wavelength cut-off filter
component) for cutting off the blue excitation light LBe.
[0120] In FIG. 20, the dichroic filter of the second dichroic
mirror 80 has a transmission characteristic of reflecting light of
a violet to blue wavelength range less than approximately 460 nm
and passing light of a green to red wavelength range more than the
same. The second dichroic mirror 80 reflects the blue excitation
light LBe in the mixed light of the blue excitation light LBe and
green fluorescence LGf downstream of the first dichroic mirror 79,
and passes the green fluorescence LGf. Also, the second dichroic
mirror 80 passes the red light LR reflected by the first dichroic
mirror 79, and reflects the blue light LB from the blue light
source 35 through the collimator lens 75. Thus, the second dichroic
mirror 80 couples light paths of the blue excitation light LBe,
green fluorescence LGf and red light LR together. Note that the
blue excitation light LBe does not enter the entrance end 55a of
the light guide device 55, and is prevented from illuminating an
object of interest.
[0121] The operation of the present embodiment is described now.
For endoscopic imaging, the endoscope 11 is connected to the
processing apparatus 12 and the light source apparatus 13. A power
source for the processing apparatus 12 and the light source
apparatus 13 is turned on to start up the endoscope system 10.
[0122] The elongated tube 16 of the endoscope 11 is entered in the
gastrointestinal tract of the patient to start imaging. In the
normal imaging mode, the B, G and R light sources 35-37 are turned
on. The light source controller 42 sets current values for driving
the LEDs 43-45 at a level suitable for the normal imaging mode, and
starts driving the B, G and R light sources 35-37. The light source
controller 42 controls light amounts by maintaining a spectrum of
emission for a target.
[0123] In the blue and red light sources 35 and 37, the LEDs 43 and
45 emit blue light LB and red light LR. The green light source 36
of the fluorescent type emits mixed light of the blue excitation
light LBe from the blue excitation light source device 44 and the
green fluorescence LGf from the green emitting phosphor 47 upon
excitation with the blue excitation light LBe. The components of
the light enter the collimator lenses 75-77 in the path coupler
41.
[0124] The red light LR is reflected by the first dichroic mirror
79 and passed through the second dichroic mirror 80. The mixed
light of the blue excitation light LBe and green fluorescence LGf
is passed through the first dichroic mirror 79. The blue excitation
light LBe is reflected by the second dichroic mirror 80. The green
fluorescence LGf is passed through the second dichroic mirror 80.
Thus, the first dichroic mirror 79 couples light paths of the red
light LR, the blue excitation light LBe and the green fluorescence
LGf in mixture. The second dichroic mirror 80 cuts off the blue
excitation light LBe. The dichroic filter in the second dichroic
mirror 80 operates as an excitation light cut-off filter
(wavelength cut-off filter component), so that the optical system
of the path coupler 41 can be constructed with simplicity.
[0125] The blue light LB is reflected by the second dichroic mirror
80. The second dichroic mirror 80 couples the paths of the blue
light LB, green fluorescence LGf and red light LR together. The
light components of the blue light LB, green fluorescence LGf and
red light LR become incident upon the condenser lens 82. Thus,
illumination light LW0 is produced from the combination of the blue
light LB, green fluorescence LGf and red light LR. The condenser
lens 82 condenses the illumination light LW0 at the entrance end
55a of the light guide device 55 of the endoscope 11, and supplies
the endoscope 11 with the illumination light LW0.
[0126] In the endoscope 11, the illumination light LW0 is guided
through the light guide device 55 to the lighting windows 22, and
applied to an object of interest. Reflected light of the
illumination light LW0 from the object of interest becomes incident
upon the image sensor 56 through the viewing window 23. The image
sensor 56 outputs image signals B, G and R to the digital signal
processor 66 of the processing apparatus 12. The digital signal
processor 66 separates the image signals B, G and R by color
separation, and inputs those to the image processing unit 67.
Imaging of the image sensor 56 is repeated at a predetermined frame
rate. The image processing unit 67 generates a normal image
according to the image signals B, G and R. The display control unit
69 outputs the normal image to the display panel 14. Also, the
normal image is updated according to the frame rate of the image
sensor 56.
[0127] The digital signal processor 66 obtains an exposure amount
according to the image signals B, G and R, and transmits an
exposure control signal to the light source controller 42 of the
light source apparatus 13 according to the obtained exposure
amount. The light source controller 42 acquires current values of
driving the B, G and R light sources 35-37 according to the
exposure control signal so as to keep a constant ratio between the
light amounts of the colors (or not to change the spectrum of the
light emission of a target). Thus, the B, G and R light sources
35-37 are driven according to the acquired current values. It is
therefore possible to keep the light amounts of the blue light LB,
green fluorescence LGf and red light LR from the B, G and R light
sources 35-37 at the constant ratio suitable for the normal imaging
mode.
[0128] To change the light amount of green fluorescence LGf in the
exposure control, the light amount of blue excitation light LBe
from the blue excitation light source device 44 is changed. In FIG.
19, a wavelength range of the blue excitation light LBe overlaps on
that of the blue light LB. Assuming that the blue excitation light
LBe is emitted for illumination, a light amount of the blue light
LB is also changed by a change in that of the blue excitation light
LBe. The spectrum of the light is changed. However, the second
dichroic mirror 80 cuts off the blue excitation light LBe, so that
the light amount of the blue light LB is controlled discretely from
the green fluorescence LGf without influence of the blue excitation
light LBe to the light amount of the blue light LB. Consequently,
the endoscope 11 can be supplied with light of the spectrum
appropriate for the normal imaging mode even upon performing the
exposure control. No change occurs in the color balance of the
normal image.
[0129] Assuming that an object with appearance of a lesion is
discovered in the normal imaging mode, the imaging mode is changed
over to the vessel enhancement imaging mode. The red light source
37 is turned off, and the blue and green light sources 35 and 36
are turned on. Color light from the blue and green light sources 35
and 36 is combined to become the illumination light LW1 by the path
coupler 41, and is supplied to the endoscope 11. In a manner
similar to the normal imaging mode, the second dichroic mirror 80
cuts off the blue excitation light LBe. Thus, the endoscope 11 can
be supplied constantly with light of a spectrum suitable for the
vessel enhancement imaging mode, without change in the color
balance of a vessel enhancement image.
[0130] The image sensor 56 receives reflected light from an object
of interest illuminated by the illumination light LW1, and outputs
image signals B, G and R to the digital signal processor 66. The
digital signal processor 66 separates the image signals B, G and R
and inputs those to the image processing unit 67, which generates a
vessel enhancement image according to the image signals B and G.
The vessel enhancement image is output to the display panel 14.
This image is updated according to the frame rate of the image
sensor 56.
[0131] Therefore, reliability of a vessel enhancement image can be
high owing to constant emission of light of a spectrum suitable of
the vessel enhancement imaging. The vessel enhancement image is
used for diagnosing a benign or malignant tumor. Reliability in the
diagnosis of a tumor can be high according to the highness in the
reliability in the vessel enhancement image.
[0132] The blue excitation light LBe with influence to the light
amount of the blue light LB is cut off by the second dichroic
mirror 80. Thus, it is possible to supply light of illumination
with the spectrum of target without complicated control of
adjusting the light amount of the blue light LB and the like in
consideration of a change in the blue excitation light LBe with a
change in the green fluorescence LGf.
Second Preferred Embodiment
[0133] In the first embodiment, the second dichroic mirror 80
includes the dichroic filter functioning as an excitation light
cut-off filter. In the second embodiment, a dichroic mirror
separate from the second dichroic mirror 80 has a dichroic filter
functioning as an excitation light cut-off filter (wavelength
cut-off filter component).
[0134] In FIG. 21, a path coupler 90 in a light source apparatus 85
includes a first dichroic mirror 91, which corresponds to the first
dichroic mirror 79 of the first embodiment, and couples a light
path of mixed light of the blue excitation light LBe and green
fluorescence LGf from the green light source 36 with a light path
of the red light LR from the red light source 37. A dichroic filter
in the first dichroic mirror 91 operates also as an excitation
light cut-off filter. In the path coupler 90, the path coupler 41
is repeated except for having the first dichroic mirror 91 instead
of the first dichroic mirror 79.
[0135] As illustrated in FIG. 22, the dichroic filter of the first
dichroic mirror 91 is caused to have a characteristic of reflecting
light of a red wavelength range equal to or more than approximately
600 nm and light of a violet to blue wavelength range less than
approximately 460 nm, and passing other light of a green wavelength
range. In other words, the dichroic filter comes to have the
band-pass characteristic of combining transmission characteristics
of the first and second dichroic mirrors 79 and 80 in the first
embodiment. However, there is a shortcoming of a high manufacturing
cost of this band-pass characteristic in comparison with a short
pass filter of transmitting light of only a short wavelength side
or a long pass filter of transmitting light of only a long
wavelength side. The structure of the first embodiment has an
advantage in a lower cost, in that the dichroic filter in the
second dichroic mirror 80 of a long pass characteristic has a
function of the excitation light cut-off filter.
Third Preferred Embodiment
[0136] In FIG. 23, another preferred light source apparatus 95 is
illustrated. A path coupler 96 has a dichroic mirror and an
excitation light cut-off filter separate from the dichroic mirror.
A wavelength cut-off filter 97 or excitation light cut-off filter
(or reduction filter) is disposed between the green light source 36
and the first dichroic mirror 79. In FIG. 24, the wavelength
cut-off filter 97 reflects light of a violet to blue wavelength
range less than approximately 460 nm, and passes light of a green
to red wavelength range other than the same. Furthermore, the
wavelength cut-off filter 97 may be disposed between the first and
second dichroic mirrors 79 and 80. In conclusion, entry of the blue
excitation light LBe to the entrance end 55a of the light guide
device 55 should be prevented. An excitation light cut-off filter
can be disposed between the blue excitation light source device 44
and the light guide device 55, and more precisely, a coupling
position (intersection point) of coupling a light path of mixed
light of the blue excitation light LBe and green fluorescence LGf
from the green light source 36 and a light path of the blue light
LB from the blue light source 35, or a position upstream from the
coupling position in the light path.
Fourth Preferred Embodiment
[0137] In the first embodiment, the current values for the LEDs
43-45 are controlled. However, a light amount of a semiconductor
light source relative to a current value of driving may be changed
by influence of various factors, including heat generated by LEDs
or phosphor or degradation with time. In the fourth embodiment,
measurement sensors are used for measuring light amounts of the
colors, to monitor a reach of the light amounts of the colors to a
target value according to an output signal from the measurement
sensors.
[0138] In FIG. 25, a path coupler 100 in a light source apparatus
99 has the elements in the path coupler 41 of FIG. 18, and also
includes a blue measurement sensor 101, a green measurement sensor
102 and a red measurement sensor 103 for light amounts, and glass
plates 105, 106 and 107. The measurement sensors 101-103 measure
the light amounts of the light of the colors from the B, G and R
light sources 35-37. The glass plates 105-107 are disposed directly
downstream of respectively the B, G and R light sources 35-37, and
partially reflect light from the B, G and R light sources 35-37, to
guide the light toward the measurement sensors 101-103.
[0139] The glass plates 105-107 are inclined with an angle of
approximately 35 degrees with reference to the optical axes of the
B, G and R light sources 35-37. The glass plates 105-107 pass light
of the colors from the B, G and R light sources 35-37. There occurs
Fresnel reflection upon incidence of the light on the glass plates
105-107. The glass plates 105-107 (optical path devices) guide
partial light (as small as 4-8%) included in the light from the B,
G and R light sources 35-37 toward the measurement sensors 101-103
by utilizing the Fresnel reflection. Also, it is possible to use
other optical path devices such as optical fibers or the like,
instead of the glass plates.
[0140] A band pass filter 109 and a long pass filter 110 are
disposed upstream of respectively the measurement sensors 102 and
103. The band pass filter 109 at the green measurement sensor 102
converts light into light of a limited wavelength range of the
green fluorescence LGf constituting the illumination light LW0 and
LW1 for final supply to the endoscope 11. In FIG. 26, the band pass
filter 109 has a transmission characteristic of reflecting light of
a red wavelength range equal to or more than approximately 600 nm
and light of a violet to blue wavelength range less than
approximately 460 nm, and passing light of a green wavelength range
other than those wavelength ranges. In short, the band pass filter
109 has a band pass characteristic in combination of the
transmission characteristics of the first and second dichroic
mirrors 79 and 80 of the first embodiment, in a manner similar to
the first dichroic mirror 91. The band pass filter 109 causes entry
of the green fluorescence LGf to the green measurement sensor 102
after cutting off the blue excitation light LBe as a partial
component of the illumination light LW0 and LW1. It is possible to
measure the light amount of the green fluorescence LGf
precisely.
[0141] The long pass filter 110 at the red measurement sensor 103
converts light into light of a limited wavelength range of the red
light LR constituting the light LW0 for final supply to the
endoscope 11. In FIG. 27, the long pass filter 110 has a
transmission characteristic of reflecting light of a green to blue
wavelength range less than approximately 600 nm and passing light
of a red wavelength range more than 600 nm. In short, the
transmission characteristic of the long pass filter 110 is opposite
to the transmission characteristic of the first dichroic mirror 79
of the first embodiment as illustrated in FIG. 19. In operation of
the long pass filter 110, only the red light LR output as a part of
the illumination light LW0 becomes incident upon the red
measurement sensor 103. Thus, a light amount of the red light LR
can be measured with precision.
[0142] In FIG. 28, the measurement sensors 101-103 receive light of
the colors guided by the glass plates 105-107 of the Fresnel
reflection, and output measurement signals to the light source
controller 42 according to light amounts of the colors. The light
source controller 42 compares each of the measurement signals to a
reference signal of a target light amount, and finely adjusts the
current values of the drive currents for the B, G and R light
sources 35-37 according to the exposure control to set the light
amounts equal to the target light amount according to the
comparison. This is effective in constantly controlling the light
amounts by monitoring with the measurement sensors 101-103 and the
fine adjustment of the current values. The light of a spectrum of
the target can be obtained with high stability.
[0143] In FIG. 29, another preferred light source apparatus 115 is
illustrated. A path coupler 116 has a wavelength cut-off filter 117
or excitation light cut-off filter (or reduction filter) at a plate
shape disposed between the green light source 36 and the first
dichroic mirror 79 (the position of the wavelength cut-off filter
97 of the third embodiment in FIG. 23) with the same transmission
characteristic as the band pass filter 109. Thus, it is unnecessary
to use the band pass filter 109. However, there is a shortcoming in
that a size of the wavelength cut-off filter 117 is larger than the
band pass filter 109. The use of the band pass filter 109 is
advantageous in view of reducing a cost and saving a space in
comparison with the wavelength cut-off filter 117.
[0144] In the fourth embodiment, the measurement sensors are used
for all of the semiconductor light sources. However, it is possible
only to use the measurement sensor for the green light source 36,
but not to use measurement sensors for the remaining semiconductor
light sources, as a change in the light amount relative to the
current value is remarkably large in the green light source 36.
[0145] In the fourth embodiment, the measurement sensors 101-103
measure light amounts downstream of the collimator lenses 75-77.
However, the light amounts may be measured between the collimator
lenses 75-77 and the B, G and R light sources 35-37 by use of the
measurement sensors 101-103. Components of the light of the colors
are diffused light, so that the measurement sensors 101-103 can
directly measure the light amounts from the B, G and R light
sources 35-37. Thus, it is unnecessary to dispose the glass plates
105-107 as an optical path device for guiding light.
Fifth Preferred Embodiment
[0146] The blue light source 35 in the above embodiments is a
single device with its wavelength range and peak wavelength.
Another preferred embodiment has a plurality of blue light sources
of which the wavelength range and peak wavelength are different
from one another. Those light sources are used in a distinct manner
from one another by considering a state of surface blood
vessels.
[0147] In FIG. 30, a light source apparatus 120 includes a light
source unit 123 and a path coupler 124. The light source apparatus
120 has the green and red light sources 36 and 37, and also a first
blue light source 121 and a second blue light source 122 of a
semiconductor. The path coupler 124 couples light paths from the
blue and green light sources 35 and 36 and the blue light sources
121 and 122. The first blue light source 121 is present in place of
the blue light source 35 of the above embodiments. For remaining
parts, the first embodiment is repeated. Elements similar to those
of the above embodiments are designated with identical reference
numerals.
[0148] For the blue light sources 121 and 122, the form of the blue
light source 35 in FIG. 4 is repeated. In FIG. 31, the first blue
light source 121 emits first blue light LB1 having a component of
400-470 nm as a blue wavelength range, and a peak wavelength of 460
plus or minus 10 nm. In FIG. 32, the second blue light source 122
emits second blue light LB2 having a component of 395-415 nm as a
violet to blue wavelength range, and a peak wavelength of 405 plus
or minus 10 nm.
[0149] The path coupler 124 includes the path coupler 41, a
collimator lens 125 and a third dichroic mirror 126. The collimator
lens 125 collimates the second blue light LB2 from the second blue
light source 122. The collimator lens 125 couples light paths of
the first blue light LB1 from the first blue light source 121 and
the second blue light LB2 from the second blue light source 122.
The path coupler 124 combines the light paths of the first and
second blue light LB1 and LB2, green fluorescence LGf and red light
LR to form one light path. In FIG. 33, a spectrum of the mixed
light of the first blue light LB1, green fluorescence LGf and red
light LR downstream of the path coupler 124 is illustrated. The
mixed light is used as the illumination light LW2 in the embodiment
for the normal imaging mode.
[0150] In FIG. 34, a spectrum of mixed light of the first blue
light LB1 and green fluorescence LGf is illustrated. In FIG. 35, a
spectrum of mixed light of the second blue light LB2 and green
fluorescence LGf is illustrated. The illumination light LW3 and LW4
is utilized in the present embodiment for the vessel enhancement
imaging mode by way of the mixed light in FIGS. 34 and 35.
[0151] The blue light sources 121 and 122 are so disposed that
their light paths extend perpendicularly with one another. The
third dichroic mirror 126 is positioned at a point of the
intersection of those light paths. The third dichroic mirror 126 is
oriented with an inclination of 45 degrees with reference to the
blue light sources 121 and 122.
[0152] In FIG. 36, the dichroic filter of the third dichroic mirror
126 has a transmission characteristic of reflecting light of a
violet wavelength range less than approximately 430 nm and passing
light of a blue, green and red wavelength range more than the same.
The third dichroic mirror 126 passes the first blue light LB1 from
the first blue light source 121 through the collimator lens 75, and
reflects the second blue light LB2 from the second blue light
source 122 through the collimator lens 125. Thus, light paths of
the blue light LB1 and LB2 are coupled together. In FIG. 20, the
second dichroic mirror 80 has a transmission characteristic of
reflecting light of a blue wavelength range less than approximately
460 nm. Thus, the second blue light LB2 reflected by the third
dichroic mirror 126 is reflected by the second dichroic mirror 80
and directed to the condenser lens 82. Consequently, all of the
light paths of the blue light LB1 and LB2, green fluorescence LGf
and red light LR are coupled together.
[0153] The absorption coefficient .mu.a of hemoglobin in blood
comes to the peak at approximately 405 nm, as has been described
with FIG. 9. Light applied to an object of interest has a small
depth of penetration according to smallness of the wavelength. See
FIG. 10. The first blue light LB1 from the first blue light source
121 with the central wavelength of 460 plus or minus 10 nm has a
relatively large depth of penetration with a relatively large
wavelength, and is absorbed in mucosal blood vessels (medium deep)
disposed at a lamina propria of the mucosa more than in surface
blood vessels as a target of the above embodiment. Thus, the first
blue light LB1 is used as special light for enhancement of the
mucosal blood vessels. In contrast, the second blue light LB2 from
the second blue light source 122 with the central wavelength of 405
plus or minus 10 nm has a relatively small depth of penetration
with a relatively small wavelength, and is absorbed in subsurface
blood vessels disposed at an epithelium (mucosa surface). Thus, the
second blue light LB2 is used as special light for enhancement of
the subsurface blood vessels. The blue light sources 121 and 122
are switched on and off selectively to use the blue light LB1 and
LB2, so that a vessel enhancement image can be obtained with high
contrast of the mucosal blood vessels or the subsurface blood
vessels.
[0154] In FIG. 37, the green and red light sources 36 and 37 and
the first blue light source 121 in the normal imaging mode are
turned on according to a time point of the storing of the image
sensor 56, to apply the illumination light LW2 (LB1+LGf+LR) to an
object of interest, the illumination light LW2 being mixture of the
first blue light LB1, green fluorescence LGf and red light LR. In
FIG. 38, the green light source 36 and the first blue light source
121 in the vessel enhancement imaging of mucosal blood vessels
(medium deep) are turned on according to a time point of the
storing of the image sensor 56, to apply the illumination light LW3
(LB1+LGf) to an object of interest, the illumination light LW3
being mixture of the first blue light LB1 and green fluorescence
LGf. In FIG. 39, the green light source 36 and the second blue
light source 122 in the vessel enhancement imaging of subsurface
blood vessels are turned on according to a time point of the
storing of the image sensor 56, to apply the illumination light LW4
(LB2+LGf) to an object of interest, the illumination light LW4
being mixture of the second blue light LB2 and green fluorescence
LGf.
[0155] Each component of the light LW2-LW4 is separated by the
micro color filters in the image sensor 56. Reflected light
corresponding to the blue light LB1 and LB2 is mainly received by
the B pixels. Reflected light corresponding to the green
fluorescence LGf is mainly received by the G pixels. Reflected
light corresponding to the red light LR is mainly received by the R
pixels. The image sensor 56 sequentially outputs the image signals
B, G and R at the frame rate according to a time point of the
readout.
[0156] The image signal B contains a component of reflected light
corresponding to the first or second blue light LB1 or LB2, so that
mucosal blood vessels (medium deep) or subsurface blood vessels can
be expressed with high contrast. In a manner similar to surface
blood vessels, vessel density between the mucosal blood vessels or
subsurface blood vessels is likely to be higher in a lesion of a
cancer or the like than that in normal body tissue. Thus, the
feature of the light source apparatus 120 in the embodiment is
effective in clearly expressing the mucosal blood vessels or
subsurface blood vessels with a specifically patterned form in the
mucosal blood vessels or subsurface blood vessels.
[0157] In the above embodiments, the peak wavelengths of blue light
are 430, 405 and 460 nm. However, a peak wavelength of blue light
from a blue light source can be 415 nm.
[0158] Especially, the wavelengths 405, 415 and 430 nm are
characterized in that the absorption coefficient .mu.a of
hemoglobin in blood is high in the absorption spectrum of the
hemoglobin in blood in FIG. 9. Therefore, a vessel enhancement
image can be obtained with enhanced contrast between blood vessels
and other tissue. Should a balance of the spectrum of light for the
vessel enhancement imaging be lost in use of the blue excitation
light LBe from the green light source 36, serious influence occurs
to the imaging due to changes in color balance of the vessel
enhancement image.
[0159] It follows that cutting off the blue excitation light LBe
from the green light source 36 with the excitation light cut-off
filter (wavelength cut-off filter component) is effective typically
in case a peak wavelength of blue light from a blue light source is
one of 405, 415 and 430 nm.
[0160] In FIG. 40, a transmission characteristic of another example
is illustrated. The wavelength cut-off filter 97 of the third
embodiment or the wavelength cut-off filter 117 of the fourth
embodiment can have the transmission characteristic as depicted.
This is a narrow band filter of green with a band pass
characteristic of reflecting light of a green and red wavelength
range equal to or more than approximately 550 nm and light of a
green and blue wavelength range less than approximately 530 nm, and
passing other light of a green wavelength range. The excitation
light cut-off filter of this transmission characteristic can cut
off the blue excitation light LBe and obtain light of a wavelength
range of 530-550 nm included in the green fluorescence LGf, so that
contrast of subsurface or deep blood vessels in the display image
can be enhanced.
[0161] To this end, a filter moving mechanism is disposed for
moving the excitation light cut-off filter between an active
position in a light path of the green light source 36 and an
inactive position set out of the light path of the green light
source 36. In the normal imaging mode, the excitation light cut-off
filter is shifted to the inactive position. In the vessel
enhancement imaging mode, the excitation light cut-off filter is
shifted to the active position.
[0162] The mounting method of the LEDs in the invention is not
limited to the first embodiment. For example, a micro lens can be
disposed on an exit surface of the resin encapsulant 35c or the
green emitting phosphor 47 in FIGS. 4 and 5 for adjusting an angle
of divergence. Also, a housing of a bullet shape including a micro
lens can be used for containing an LED in place of the surface
mounting type. In the above embodiments, the green emitting
phosphor 47 and the blue excitation light source device 44 are both
mounted on the semiconductor substrate 36a by way of the green
light source 36. However, the green emitting phosphor 47 can be
separate from the semiconductor substrate 36a. To this end, guiding
optics such as a lens or fiber optics can be added between the blue
excitation light source device 44 and the green emitting phosphor
47, to guide excitation light from the blue excitation light source
device 44 to the green emitting phosphor 47.
Sixth Preferred Embodiment
[0163] In FIG. 41, another preferred light source apparatus
includes a blue excitation light source device or light source LD
131 (light source laser diode), in place of the LED. A fluorescent
type of green light source 130 of a semiconductor includes the
light source LD 131 and green emitting phosphor 132 disposed
downstream of the light source LD 131. The green light source 130
is used in place of the green light source 36 of the above
embodiments.
[0164] For this purpose, a transparent rotatable disk 133 is
prepared. A coating is applied to a surface of the rotatable disk
133 to form the green emitting phosphor 132. A rotating mechanism
134 with a motor and the like rotates the rotatable disk 133. Blue
excitation light from the light source LD 131 is applied to a point
that is disposed eccentrically on the rotatable disk 133. Rotation
of the rotatable disk 133 can prevent the excitation light from
concentrating at one point on the green emitting phosphor 132.
Should excitation light concentrate at one point on the green
emitting phosphor 132, the point of the green emitting phosphor 132
will be overheated to quicken degradation of the green emitting
phosphor 132. However, the feature of the embodiment can prevent
such a difficulty. Note that a condenser lens 135 condenses the
blue excitation light from the light source LD 131 on the rotatable
disk 133.
[0165] Also, an excitation light cut-off filter (wavelength cut-off
filter component) may be formed on an exit surface of the rotatable
disk 133. It is possible to use an organic electro luminescence
device (EL device) and the like may be used instead of the LEDs and
LDs. Furthermore, the blue and red light sources 35 and 37 and the
like other than the light source of a type with green emitting
phosphor can be constituted by an LD, organic EL device and the
like.
[0166] The excitation light cut-off filter for cutting all of the
excitation light is used in the above embodiments. However, the
invention is not limited to those embodiments. An excitation light
cut-off filter (wavelength cut-off filter component) according to
the invention can be an element with a transmission characteristic
for reducing a light amount of the excitation light, for example,
reducing the light amount by 50%. However, it is desirable for an
excitation light cut-off filter to cut off 100% of the excitation
light because of high effect.
[0167] The path coupler of the invention is not limited to the
above embodiments. It is possible to use a dichroic prism including
a prism and a dichroic filter formed thereon in place of the
dichroic mirror. For the purpose of coupling the light paths, it is
possible to use a light guide device of a branch form having plural
entrance ends for light sources and one exit end directed to the
entrance end of the light guide device of the endoscope, in place
of the optics having the dichroic filter. The light guide device of
the branch form is a fiber bundle of plural optical fibers.
Proximal ends of the optical fibers are grouped at a predetermined
number of fibers to form the plural entrance ends. Light sources of
a semiconductor are disposed upstream of respectively the entrance
ends. An excitation light cut-off filter is disposed between the
fluorescent type of green light source and one of the entrance
ends.
[0168] In the above embodiments, the image sensor is the color
image sensor. However, an image sensor in an endoscope system of
the invention may be a monochromatic image sensor. In the above
embodiment, the lighting control is the simultaneous lighting (with
normal white light), with which the color image sensor acquires
image signals of B, G and R simultaneously. However, a lighting
control in a light source apparatus can be field sequential
lighting, in which blue, green and red light components are applied
to an object of interest one after another, for a monochromatic
image sensor to acquire image signals of B, G and R
sequentially.
[0169] In FIG. 42, the field sequential lighting is illustrated. In
the vessel enhancement imaging mode, the blue and green light
sources 35 and 36 are turned on and off alternately according to
time points of the storing of the image sensor. The blue light LB
and the green fluorescence LGf are applied to an object of interest
alternately. The image processor produces a vessel enhancement
image of one frame according to image signals of two consecutive
frames.
[0170] Furthermore, the lighting control in the endoscope system
can be changeable between simultaneous lighting and field
sequential lighting. In FIG. 15, the simultaneous lighting is set
for emitting the mixed illumination light LW1 of the blue light LB
and the green fluorescence LGf. In FIG. 42, the field sequential
lighting is set for sequentially emitting the blue light LB and the
green fluorescence LGf. It is possible to utilize advantages of
both the simultaneous lighting and the field sequential
lighting.
[0171] Furthermore, the features of the various embodiments can be
combined with one another according to the present invention.
[0172] Furthermore, a light source apparatus with the feature of
the invention can be a light source apparatus including a violet
semiconductor light source (violet LED). In the above embodiments,
the wavelength range of the blue light LB from the blue LED 43
overlaps on that of the blue excitation light LBe from the blue
excitation light source device 44. Similarly, a wavelength range of
violet light from the violet semiconductor light source is likely
to overlap partially on that of the blue excitation light LBe from
the blue excitation light source device 44. However, the feature of
the invention is effective in preventing influence of the blue
excitation light LBe to a light amount of the violet light.
[0173] In the above embodiments, the light source apparatus 13 is
separate from the processing apparatus 12. However, a composite
apparatus including components of the processing apparatus 12 and
the light source apparatus 13 may be used in the invention.
Furthermore, an endoscope and light source apparatus of the
invention can be used with a fiber scope for guiding reflected
light from an object of interest by use of an image guide, an
ultrasonic endoscope including an image sensor and an ultrasonic
transducer incorporated in the tip device.
[0174] According one embodiment mode of the invention, furthermore,
a red semiconductor light source emits red light of a red
wavelength range.
[0175] According another embodiment mode of the invention, the blue
semiconductor light source emits the blue light with a peak
wavelength of at least one of 405, 415, 430 and 460 nm.
[0176] According still another embodiment mode of the invention,
the blue excitation light source device is a light emitting
diode.
[0177] Although the present invention has been fully described by
way of the preferred embodiments thereof with reference to the
accompanying drawings, various changes and modifications will be
apparent to those having skill in this field. Therefore, unless
otherwise these changes and modifications depart from the scope of
the present invention, they should be construed as included
therein.
* * * * *