U.S. patent application number 12/278740 was filed with the patent office on 2009-12-10 for near infrared imaging.
This patent application is currently assigned to Novadaq Technologies Inc.. Invention is credited to John C. Tesar.
Application Number | 20090303317 12/278740 |
Document ID | / |
Family ID | 38510130 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090303317 |
Kind Code |
A1 |
Tesar; John C. |
December 10, 2009 |
NEAR INFRARED IMAGING
Abstract
An endoscope or wand device comprising transmitting members, in
which the transmitting members comprise a coating that transmits
between about 95% and about 99.5% of energy at a wavelength within
the infra red spectrum.
Inventors: |
Tesar; John C.; (Tucson,
AZ) |
Correspondence
Address: |
RISSMAN HENDRICKS & OLIVERIO, LLP
100 Cambridge Street, Suite 2101
BOSTON
MA
02114
US
|
Assignee: |
Novadaq Technologies Inc.
Ontario
CA
|
Family ID: |
38510130 |
Appl. No.: |
12/278740 |
Filed: |
February 7, 2007 |
PCT Filed: |
February 7, 2007 |
PCT NO: |
PCT/US07/61810 |
371 Date: |
December 10, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60771288 |
Feb 7, 2006 |
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60793979 |
Apr 20, 2006 |
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60828627 |
Oct 6, 2006 |
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Current U.S.
Class: |
348/65 ;
348/E7.085 |
Current CPC
Class: |
G02B 27/145 20130101;
G02B 27/1013 20130101; H04N 5/2256 20130101; H04N 2005/2255
20130101; G02B 23/2453 20130101; A61B 5/0075 20130101; G02B 5/04
20130101; H04N 5/33 20130101; C03C 17/3452 20130101; G02B 27/142
20130101; A61B 1/07 20130101; A61B 1/0661 20130101; C03C 17/3417
20130101 |
Class at
Publication: |
348/65 ;
348/E07.085 |
International
Class: |
H04N 7/18 20060101
H04N007/18 |
Claims
1. An endoscope or wand device comprising light transmitting
members, said light transmitting members comprising an optical
coating that transmits between about 95% and about 99.5% of light
energy at a wavelength within the infra red spectrum.
2. The device of claim 1, further comprising a deviating prism
assembly having at least one surface coated with gold, silver or
aluminum.
3. The device of claim 1, wherein the coating on the transmitting
members comprises alternating layers of dissimilar optically
transparent dielectric materials.
4. The device of claim 3, wherein the dielectric materials are
selected from the group consisting of titanium dioxide (TiO.sub.2),
silicon dioxide (SiO.sub.2), zirconium oxide (ZrO.sub.2), magnesium
fluoride (MgF.sub.2) and tantulum pentoxide (Ta.sub.2O.sub.5).
5. (canceled)
6. (canceled)
7. The device of claim 1, wherein the coating on the transmitting
members comprises between about 2 and about 40 pairs of alternating
layers of dissimilar optically transparent dielectric
materials.
8-10. (canceled)
11. The device of claim 1, wherein the wavelength within the infra
red spectrum is a wavelength at which an excited fluorescent dye
emits energy.
12. The device of claim 11, wherein the fluorescent dye is ICG.
13. The device of claim 11, wherein the wavelength within the infra
red spectrum is between about 825 nm and about 835 nm.
14-21. (canceled)
22. A near infra-red light source comprising: a light emitter that
emits light in the infra red spectrum; a reflector comprising a
first coating that routes light in the infra red spectrum toward a
beam splitter that transmits light in the infra red spectrum; said
beam splitter comprising a second coating for routing light in the
infra red spectrum toward a light guide having a numerical aperture
between about 0.4 and about 0.66.
23. (Canceled)
24. The light source of claim 22, wherein the reflector is
elliptical.
25. The light source of claim 22, wherein the reflector is
parabolic.
26. The light source of claim 22, further comprising a collimating
lens assembly positioned between the beam splitter and the
reflector.
27. The light source of claim 22, wherein the first coating
comprises a metal selected from the group consisting of gold,
silver and aluminum.
28. (canceled)
29. (canceled)
30. The light source of claim 22, wherein the beam splitter routes
light having a wavelength between about 750-800 nm to the light
guide.
31. The light source of claim 22, wherein the beam splitter further
routes light in the visible spectrum to a second light guide.
32. The light source of claim 22, wherein the second coating
includes alternating pairs of high and low index materials.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 60/771,288 filed on Feb. 7, 2006, and entitled
"Endoscopes and Wands", U.S. Provisional Application Ser. No.
60/793,979 filed on Apr. 20, 2006 and entitled "Endoscopes and
wands", and U.S. Provisional Application Ser. No. 60/828,627 filed
on Oct. 6, 2006 and entitled "Endoscopes and Wands". Each of these
applications is hereby incorporated by reference in its entirety.
Each of these are incorporated by reference in their entirety.
TECHNICAL FIELD
[0002] This application relates to endoscopes and similar
devices.
BACKGROUND OF THE INVENTION
[0003] An endoscope or wand viewing apparatus is usually configured
in a way that is well suited for illumination and imaging in
visible light.
[0004] In this background section endoscopes and wand like devices
shall be described in terms of their internal working components.
In the second portion of the background section the shortcomings of
these predicate devices shall be described with respect to their
use for laser induced fluorescence imaging.
[0005] An endoscope is an opto-mechanical imaging device
characterized by the following: an objective lens assembly
containing an optional deviating prism assembly, a relay system
forming a plurality of intermediate images for the case of a rigid
endoscope, an ocular, a camera system containing multiple detectors
with a prism assembly directing sections of the electromagnetic
spectrum to dedicated sensors, or in the case of chip-on-a-stick
endoscope where there are no intermediate images; an objective lens
assembly coupled directly to the camera detector which is embedded
in the distal most portion of the device. In either case the
optical elements are contained in an inner most tube member which
is surrounded by other tube members which may include fiber optics
for illumination in the annulus formed by two or more of the tubes
and may contain other tubes for the passage of instruments and or
irrigation.
[0006] An objective lens assembly in the distal most portion of the
device forms a real image of the scene coincident with the plane of
the detector in the case of a chip-on-a-stick endoscope or
intraoral camera, or distal most plane of a relay system that is
contained within the shaft portion of the endoscope.
[0007] In an endoscope with a relay system (the second case above),
there are 2 basic forms of relays, those of lenses and those using
coherent imaging fibers.
[0008] In both examples the role of the relay is to reform the
image produced by the objective lens through the length of the
shaft by producing intermediate images in the case of a rigid
endoscope to a new position where the ocular, in the case of a
visual endoscope or camera lens group in the case of a digital or
electronic imaging device, may then reform the image originally
produced by the objective lens group for the eye or to a camera
detector.
[0009] The shaft portions of all endoscopes are made to facilitate
the insertion of the device into a body cavity or body lumen, that
is to say diameter is the dimension being minimized. In the case of
a body cavity insertion, the shaft is often rigid and comprised of
thin walled stainless steel tubes. This tube within tube
construction allows for an innermost tube to contain the optical
train and then surrounding tubes can contain fiber optics to
transmit illumination to the scene in the form of an annulus.
Additional tubes can be contained within the assembly for the
introduction of surgical instruments for various purposes.
[0010] For the case of an endoscope that utilizes coherent imaging
fibers for the relay system the functional concept being optimized
in the device is flexibility, and to some degree what is being
compromised is resolution, particularly when the diameter of the
tip is small. However, large diameter flexible endoscopes often use
detectors directly behind the objective lens assembly and are
therefore considered "chip-on-a-stick" configurations. These
flexible endoscopes often have internal channels, instrument and
irrigation channels, to pass forceps, etc. and have internal guide
wires and steering mechanisms at the tip controlled by levers at
the proximal end of the device.
[0011] There is a class of smaller diameter endoscopes utilizing
coherent imaging fibers as relays whose shafts have a limited
amount of flexibility, and these devices are commonly called
semi-flexible. Often configured with a working channel, called a
forceps channel, used for instruments and are often used in
Urology.
[0012] Whether rigid, flexible, or semi-flexible, endoscopes have a
proximal eyepiece section for viewing and or coupling to a camera
system. An eyepiece is not present on chip-on-a-stick endoscopes or
intraoral cameras, often called dental cameras, as the camera is
imbedded into the distal portion of the device.
[0013] Where eyepieces are used, manufacturers have almost
universally adopted a nominal 32 mm eye cup for blocking room light
from the physician's view, and this eye cup serves to support the
coupling mechanism to the camera. There are some commercial
applications of directly coupling the camera and optical assemblies
included in the shaft mechanism and or coupling mechanism but this
has not found wide acceptance, except in Orthopedics for
Arthroscopy. The fear among users has been that if the electronics
of the camera fail for some reason then the doctor is left with no
means to view within the patient, hence the continuing presence of
endoscopes with eyepieces.
[0014] The class of endoscopes not utilizing eyepieces is commonly
called chip-on-a-stick. The intraoral dental camera shares the lack
of eyepiece or ocular, as well. Both instruments send a video
signal to a monitor or computer for viewing.
[0015] Endoscopes are most commonly fixed focus imaging devices.
There is a broad distance from the tip of the device to the subject
that is in focus due to the relatively small aperture of the
optical system. A small aperture allows only a small amount of
light to be imagined for any point in the scene. Should focusing be
required it is accomplished by repositioning the optics in the
camera module proximal to the endoscope, or in some cases the
detector itself is moved.
[0016] Such low levels of return signal in the visible spectrum
require endoscopes to have large light sources such as xenon,
halogen, and metal halide.
[0017] In the case of an endoscope, commonly called a
chip-on-a-stick which contain a distal most detector (CCD, CMOS, or
other sensor), the change in image plane position for a near object
of interest versus a far object of interest is usually ameliorated
by installing a very small aperture in the objective lens assembly
to increase depth of field at the expense of a bright field or
higher potential resolution.
[0018] This is a distinction between endoscopes and chip-on-a-stick
endoscopes regarding focus. Endoscopes with proximal cameras do
provide a means for focus even if they themselves are fixed focus.
Chip-on-a-stick endoscopes usually do not provide a focus means.
However, large diameter flexible endoscopes used in
gastroenterology do often have moveable detectors or lenses
providing focus.
[0019] For smaller chip-on-a-stick endoscopes, all of the optical
elements in the objective lens assembly are optimized for the small
aperture which allows great depth of field. It is not the case that
the aperture could be removed for increased brightness. The
advantage is that no motion (focus) is required and when provided
with powerful illumination systems in the visible light the overall
system can perform well given the constraint of illumination.
[0020] A focus means becomes an area of distinction between a
chip-on-a-stick endoscope and a wand imaging device, referred to as
an intraoral or dental camera, as well. Both chip-on-a-stick
endoscope and a wand imaging devices contain the detector plane in
the distal or forward portion of the device directly behind the
objective lens assembly. The intraoral or dental camera is often
required to be used in stand off mode, a distance that is greater
than endoscopy requires. The distinction results from the use;
endoscopy is done in closed surgical or diagnostic sites, the
intraoral devices are used external to the body or inserted in
natural cavities such as the mouth. In such stand off modes, not
the mouth but full face views, great amounts of illumination would
be required to satisfy the large change in s and s' (the optical
path length on either side of the objective lens) in the intraoral
or dental camera where to be fixed focus. Therefore, intraoral or
wand like dental cameras frequently contain a means to move the
detector plane, or focus the device. Using a faster F number, with
inherently less depth of field but higher sensitivity, and by
moving the detector plane a lower powered illumination system is
required. This allows a wand with near IR capabilities to
accommodate large changes in distances to the object of interest,
thereby allowing a faster optical system to be designed, a
characteristic that requires variable focus, but provides higher
inherent resolution, and more conservative illumination
sources.
[0021] Endoscopes and wands are generally designed to visualize in
the visible spectrum. However, fluorescent dyes, such as
indocyanine green (ICG) (Akorn, Inc., Buffalo Grove, Ill.) are
commonly being used to image anatomy in the infra red spectrum. Use
of ICG is described in, for example, U.S. Pat. No. 6,915,154, which
is incorporated herein by reference in its entirety. Once excited,
ICG emits in the infra red spectrum at about 825 to about 835 nm.
FIG. 1 shows the excitation and emission spectrum of the ICG
composition sold by Akorn, Inc. There is therefore a need for
endoscope and wand devices that are capable of imaging and
visualizing in the infrared spectrum.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 shows the excitation and emission spectrum of the ICG
composition sold by Akorn, Inc.
[0023] FIG. 2 illustrates an endoscopic system.
[0024] FIG. 3 illustrates an endoscope.
[0025] FIG. 4 illustrates certain endoscope components. The left
side of FIG. 4 illustrates multiple examples of objective
assemblies, only one of which would commonly be used in any
particular endoscope. The middle of FIG. 4 illustrates multiple
examples of relays, of which only one would commonly be used in a
particular endoscope. The right hand side of FIG. 4 illustrates a 2
channel prism or a 4 channel prism (the bottom two drawings showing
the same 4 channel prism from different views). Commonly only one
of a 2 or a 4 channel prism would be used in any particular
endoscope.
[0026] FIG. 5 illustrates deviating prisms.
[0027] FIG. 6 illustrates representative scans of prior art
coatings.
[0028] FIGS. 7 and 8 each illustrate details of coatings.
[0029] FIG. 9 illustrates a 2 chip prism assembly. Angles shown are
merely exemplary.
[0030] FIG. 10 illustrates a 4 chip prism assembly. Angles shown
are merely exemplary.
[0031] FIG. 11 illustrates a light source.
[0032] FIG. 12 illustrates a second embodiment of the light
source.
MODES FOR CARRYING OUT THE INVENTION AND INDUSTRIAL
APPLICABILITY
[0033] The invention provides endoscope and wand devices and
systems for imaging in the infrared spectrum, and preferably in
multiple spectrums at least one of which is infrared. Imaging of
fluorescent emissions in the infrared spectrum is particularly
difficult because the near infrared light emitted by a fluorescent
dye may be an order of magnitude or more lower than the visible
light reflected or emitted by a subject. A "device" is any
hand-held instrument designed to view or image anatomy, either
inside or outside a patient's body.
[0034] In certain embodiments, the invention provides an endoscope
or wand device having relay optics such as glasses. The
transmitting members have a coating that transmits between about
95% and about 99.5% of energy at a wavelength within the infra red
spectrum.
[0035] In some embodiments, the invention provides a prism assembly
for separating visible light from infra red light. The prism
assembly contains at least one channel configured to receive and
transmit light in the visible spectrum and at least a second
channel configured to receive and transmit light in the infra red
spectrum.
[0036] Hereinafter, aspects in accordance with various embodiments
of the invention will be described. As used herein, any term in the
singular may be interpreted to be in the plural, and alternatively,
any term in the plural may be interpreted to be in the
singular.
Definitions
[0037] "Approximately", "substantially" and "about" each mean
within 10%, preferably within 6%, more preferably within 4% even
more preferably within 2%, and most preferably within 0.5% of the
stated number or range
[0038] "Computer" as used herein, refers to a conventional computer
as understood by the skilled artisan. For example, a computer
generally includes a central processing unit that may be
implemented with a conventional microprocessor, a random access
memory (RAM) for temporary storage of information, and a read only
memory (ROM) for permanent storage of information. A memory
controller is provided for controlling RAM. A bus interconnects the
components of the computer system. A bus controller is provided for
controlling the bus. An interrupt controller is used for receiving
and processing various interrupt signals from the system
components. Mass storage may be provided by diskette, CD ROM, DVD,
USB stick, or hard drive. Data and software may be exchanged with
computer system via removable media such as the diskette, USB
stick, or CD ROM. A CD ROM or DVD drive is connected to the bus by
the controller. The hard disk is part of a fixed disk drive that is
connected to the bus by a controller. User input to the computer
may be provided by a number of devices. For example, a keyboard and
mouse may be connected to the bus by a controller. An audio
transducer that might act as both a microphone and a speaker may be
connected to the bus by an audio controller. It will be obvious to
those reasonably skilled in the art that other input devices, such
as a pen and/or tablet may be connected to the bus and an
appropriate controller and software, as required. A visual display
can be generated by a video controller that controls a video
display. Preferably, the computer further includes a network
interface that allows the system to be interconnected to a local
area network (LAN) or a wide area network (WAN). Operation of the
computer is generally controlled and coordinated by operating
system software, such as the Solaris operating system, commercially
available from Sun Microsystems, the UNIX.RTM. operating system,
commercially available from The Open Group, Cambridge, Mass., the
OS-X.RTM. operating system, commercially available from Apple,
Inc., Cupertino Calif. or the Windows XP.RTM. or VISTA.RTM.
operating system, commercially available from Microsoft Corp.,
Redmond, Wash., or the Linux open source operating system available
from multiple sources. The operating system controls allocation of
system resources and performs tasks such as processing scheduling,
memory management, networking, and I/O services, among things. In
particular, an operating system resident in system memory and
running on the CPU coordinates the operation of the other elements
of computer. "Subject" as used herein, refers to any animal. The
animal may be a mammal. Examples of suitable mammals include, but
are not limited to, humans, non-human primates, dogs, cats, sheep,
cows, pigs, horses, mice, rats, rabbits, and guinea pigs.
[0039] As used herein, "wavelength of interest" refers to light in
both the visible and infra red spectrum. In some embodiments, it
refers to light in only the infra red spectrum. In some
embodiments, it includes light at the wavelength at which ICG
fluoresces. In some embodiments, it includes light between about
825 and about 835 nm. In some embodiments, it includes light
wavelength(s) at which one or more other fluorescent dyes emit
energy when excited. The invention is drawn to endoscopes and wands
that can advantageously be used for visualizing and imaging in the
infrared spectrum, and preferably in both the infrared and visible
spectrums.
[0040] The term "endoscope", as used herein, will be understood to
encompass wands and laparoscopes, as well as endoscopes and other
similar devices.
[0041] FIG. 2 illustrates a highly schematic view of an endoscopic
system. The endoscope 260 is placed in the proximity of a subject's
tissue or inside a natural or surgically created opening in the
subject.
[0042] An endoscope may have one or more illumination sources 220.
Preferably, the illumination 220 source emits radiation having
wavelengths in the infrared spectrum, and images in the infrared
spectrum. Infrared radiation at certain wavelengths can excite a
fluorescent dye that has been administered to the patient and cause
the fluorescent dye to emit radiation. In certain embodiments,
imaging may be performed in multiple discrete bands of the
spectrum. For example, imaging may occur in two distinct infrared
bands, in the infrared and visible spectrum, or in the infrared and
ultraviolet spectrum. In preferred embodiments, both visible and
infrared light is emitted by one or more illumination sources 220
for imaging in both the visible or infrared spectrums.
[0043] The one or more illumination sources 220 is in electrical
communication with the computer 360. Through a computer interface,
a user causes an illumination source(s) 220, such as an HPLD, to
fire or otherwise emit radiation.
[0044] The illumination source 220 can be coupled to the existing
fiber optics in the endoscope or wand or coupled to an external
cannula embedded with fiber optics or containing a working channel
with sufficient diameter to place a fiber optic or fiber optic
probe for the transmission of an excitation wavelength. The
endoscope itself may contain a working channel sufficiently large
for a laser fiber to be inserted and in that case a supplementary
cannula or sheath for an excitation source would not be required.
Other suitable illumination sources are described below.
[0045] In some embodiments, the illumination source 220 is in
optical communication with endoscope 260 by cable(s)/cannula(s)
280. If the illumination source 220 is a single emitter laser then
it could be coupled to one cable 280. Alternately, a bar laser
would require multiple fibers, which might be packed in the same or
in multiple cables. Cable(s) 280 may connect to fibers integrated
into the tubular portion of the endoscope 260 or to a sheath
surrounding part or all of the endoscope 260. Fibers in the tubular
portion or sheath then relay the illumination to the patient's
tissue.
[0046] Light from the illumination source(s) 220 is transmitted to
the subject's tissue. Reflected or emitted light from the subject's
tissue is then transmitted to one or more detectors. These
detector(s) are in electrical communication with computer 360,
which receives the images collected by the detector(s) and causes
them to be displayed on a display 365. The computer 360 may further
include software for image processing.
I. Illumination Sources 220
[0047] The first step in imaging a dye (that is administered to a
patient) that emits in the infrared spectrum is to excite the dye.
The dye may be excited in the visible, ultraviolet or infrared
spectrum. Preferably, the dye is a fluorescent dye. More
preferably, the dye is a tricarbocyanine dye. Most preferably, the
dye is ICG. In some embodiments, multiple dyes may be used for
imaging.
[0048] In one embodiment, the light source only emits light in the
infrared spectrum. In some embodiments, light in both the visible
and infrared spectrum is emitted. In some embodiments, the device
of the invention, such as an endoscope or wand includes one or more
LEDs that emits light in the infrared spectrum and groups of 3
LEDs, producing red, green, or blue illumination, respectively, for
visible imaging. In certain embodiments, the device includes LEDs
producing or restricted to infrared illumination combined with one
or more white light LEDs. Light sources may be bulbs or arc sources
of metal halides, halogens and xenon that emit in the blue, green
and red and infra red wavelengths. LEDs and other light sources
that emit in both the visible and infrared spectrums are well known
to the skilled artisan.
[0049] High power laser diodes (HPLDs) may also be used within the
scope of the invention. Examples of HPLDs include AlInGaAsP lasers
and GaAs lasers which are well known in the art. Such sources can
be single diodes (single emitters), or diode-laser bars, which are
made from edge emitting semiconductor chips. Such sources can be
operated in continuous mode (CW), quasi-CW, or pulsed mode.
[0050] These sources are capable of being remotely mounted in the
system and can be brought to the optical system used for viewing
fluorescence via fiber coupling. This removes the HPLD, a powerful
electrical device, from intimate contact with the patient,
physician or technician.
[0051] The excitation wavelength, .lamda..sub.e, of ICG is 805 nm
in whole blood. The range of excitation wavelengths capable of
exciting ICG ranges from approximately 710 nanometers to 840
nanometers, or more. This range overlaps the fluorescence range of
ICG whose peak, .lamda..sub.f, is 835 nanometers. It is therefore
necessary to use a narrow source such as an HPLD or similarly
filtered Metal halide, Xenon, or Tungsten halogen sources of
radiation by means of an excitation or primary filter or filters to
excite the ICG.
[0052] HPLDs, made of AlInGaAsP/GaAs, have as their peak nominal
output a wavelength of 808 nm, with a tolerance of +/-3 nanometers.
A driving circuit is necessary to provide power to the HPLD, the
current and voltage of which can be varied to lower the peak
wavelength to 805 nm, the peak absorption of ICG.
[0053] Within the endoscope proper, an illumination pathway may
take one of two forms or a combination of the following: an
integrated annulus of fiber optic fibers encircling the optical
elements for the transmission of visible light, and or an annulus
of fiber optic fibers transmitting the energy from an IR excitation
source contained within a sheath or cannula into which the imaging
device is inserted.
II. Endoscopes and Wands
[0054] For example, endoscope 260 is shown in FIG. 3, and certain
components are shown in FIG. 4. The endoscope 260 may include a
distal section 3, a relay section 2, and a proximal section 29.
Light travels from an illumination source 220 (not shown) to fiber
cable 28 through the relay section 2 and to the distal section 3.
Reflected or emitted light travels from the distal section 3 having
the objective assembly, through the relay section 2 and then
through the proximal section 29 having prisms to the detector(s) 33
(shown in FIGS. 9 and 10) in proximal section 29. The detector(s)
33 detect the light and can form an image. The endoscope 260 may
include an ocular and camera optics in the proximal section 29 to
magnify or focus the image.
[0055] All the optical elements along the 3 segments of the
longitudinal axis of the endoscope and wand are required to be
coated for low reflectivity for (preferably all) transmitting
elements across all the wavelengths of interest, high reflectivity
in all wavelengths of interest for reflecting surfaces contained
within the distal section, and high separation ratios in the
proximal beam-splitting section. An embodiment for a wand
configuration contains in its distal portion both a deviating and a
beam-splitting prism assembly. Preferably each optical coating on a
transmitting optical element is optimized for an angle of incidence
of light that is orthogonal or substantially orthogonal to each
surface along a vector describing the opto-mechanical axis of the
system within a range of plus or minus 10, 9, 8, 7, 6, 5, 4, 3, 2,
or 1 degrees. This does not apply to the objective lens assembly
where the departure from normal to the surface is greater.
[0056] The wand has the same components as shown in FIGS. 3 and 4,
but generally has a different form factor since it is optimized for
use outside a person's body while an endoscope is optimized for
insertion into a person's body.
A. Distal Section 3
[0057] The distal section 3 of the inventive device may include an
optical assembly taking the form of an inverse telephoto with a
distal negative power lens group, a prism assembly 18 to deviate
the line of sight within this deviating assembly and a positive
lens group. A deviating prism assembly 18 is contained between the
distal lens group characterized by its negative optical power and a
proximal lens group characterized by its positive power. This
optical form (- +) is commonly called an inverse telephoto. Distal
sections of endoscopes and other devices are well known in the art,
and are described in, for example, U.S. Pat. No. 4,655,557 that is
incorporated herein by reference in its entirety.
[0058] Deviating prism assemblies 18 are routinely placed within
the space between the two powers of endoscopes used in visible
wavelengths, as described, for example, in U.S. Pat. No. 4,917,457,
which is incorporated herein by reference in its entirety. Such
deviating prisms allow the endoscope to be rotated around the shaft
axis for a larger effective field of view. Examples of deviating
prisms 18 are shown in FIG. 5. The angles shown are exemplary since
a skilled artisan may design deviating prisms to facilitate the
passage of the full beam diameter or substantially the full beam
diameter of the objective lens assembly through the prism with the
following constraints, first that the ray path axis exiting the
negative group of the objective lens be coincident or approximately
coincident with the optical axis of the prism assembly group,
second that the ray path enter the front face of the prism assembly
perpendicular or approximately perpendicular to the face of the
first surface of the prism assembly, thirdly, that the ray path
exit the last surface of the deviating prism assembly perpendicular
or approximately perpendicular or normal to the face of the last
prism component, and fourthly that the exit ray path optical axis
be coincident or approximately coincident with the optical axis of
the following optical components.
[0059] The deviating prisms of the invention must displace or
deviate the line of sight. For example, the first prism (FIG. 5
(a)) has a zero percent deviation, meaning that the wavelengths of
interest are transmitted through each of the surfaces 19a, 19b, 19c
and 19d.
[0060] In FIG. 5 (b), the line of sight is deviated thirty degrees.
This means that the line of sight and coincident beam path is
transmitted through surface 19e, 19f, 19g, reflected by surface 19h
and 19i, and then transmitted through surfaces 19j and 19k.
[0061] FIG. 5(c) shows an example of a 45.degree. deviating prisms.
The line of sight and coincident beam path is transmitted through
surfaces 19l, 19m and 19n, reflected by surfaces 19o and 19p, and
then transmitted by surfaces 19q and 19r.
[0062] A final example, FIG. 5d, shows an exemplary 70.degree.
deviating prism. The line of sight and coincident beam path is
transmitted through surfaces 19s and 19t, reflected by surfaces 19u
and 19v, and then transmitted through surfaces 19w and 19x.
[0063] Thus, the reflective surfaces (e.g., 19h, 19i, 19o, 19p, 19u
and 19v) must be coated with a substance that reflects light in the
infrared in preference to one that is optimized for the reflection
of visible only. In preferred embodiments, in which the wavelengths
of interest are in the emission range of ICG, the reflective
surfaces are coated so that they reflect light between about 800
and about 850 nm, preferably between about 825 nm and about 835 nm.
Most preferably, the reflecting surfaces reflect both infrared and
visible light. This high reflectance of wavelengths in the infra
red spectrum, and preferably in both the visible and infra red
spectrums, is achieved with a coating of gold, silver or aluminum.
Gold is particularly preferred for reflecting only wavelengths in
the near infra red spectrum. Silver is particularly preferred for
reflecting wavelengths in the visible and near infra red spectrums.
These coatings can be applied directly to the reflecting prism
surface and are between about 1 and about 20 micrometers in
thickness, and preferably between about 1 and about 10 micrometers
in thickness. They can be purchased from, for example, TYDEX
J.S.Co. (St. Petersburg, Russia) and vapor deposited onto the
surface of interest by any number of thin film coaters in the world
using vacuum deposition chambers. Gold coatings are especially
preferred because they are known to reflect well in the near IR and
withstand autoclaving processes. In some embodiments, any coating
that reflects at least 80%, preferably at least 90% and most
preferably at least 95% of light energy that is within the
wavelengths of interest may be used. A second coating, such silicon
dioxide (SiO.sub.2), magnesium fluoride, silicon monoxide or a
dielectric overcoat may be applied. Such coatings can be purchased
from, for example, OFR, Inc., Caldwell , N.J.
[0064] The transmitting prism surfaces (e.g., 19a, 19b, 19c, 19d,
19e, 19f, 19j, 19k, 29l, 19m, 19q, 19r, 19s, 19t, 19w and 19x each
transmit wavelengths of light in the infrared and the visible
spectrums. Any surface that is glued and not air-glass does not
need an anti-reflecting coating applied.
B. Transmitting Members
[0065] The vast majority of optical surfaces that are used for
transmitting the wavelengths of interest ("transmitting members")
are in the relay section. The discussion of transmission coatings,
below, is framed in reference to transmitting members in the relay
section, though it is equally applicable to transmitting members in
other parts of the endoscope or wand.
[0066] The positive lens group in the objective lens assembly forms
a real image from the energy received from outside the device for
relay to the relay section 2. The relay section 2 includes multiple
relay optics (not shown) that relay the image by producing a series
of intermediate images to the proximal section 29. The proximal
section 29 will be further described below.
[0067] The prior art optical coatings on devices such as endoscopes
and wands having relay optics are optimized for the visible
spectrum and are biased towards the blue as shown in the
representative scans of such coatings on optical glasses, such as
F2 and SF6 in FIG. 6. However, such prior art coatings reflect more
than 5% of the infrared energy at each glass/air surface. Since a
typical relay section 2 could have a large number (e.g., 30-40)
glass/air surfaces, the resulting reflectance makes the devices
unusable for infrared imaging.
[0068] Devices of the invention must have coatings in the relay and
other sections that transmit wavelengths in the infrared spectrum
that are of interest. Preferably, the coatings have a reflectance
of the wavelengths of interest that are no more than about 0.5%, no
more than about 0.4%, no more than about 0.3%, no more than about
0.2% and most preferably no more than about 0.5%. In some
embodiments, coated relay optics each reflect between about 0.5%
and about 5% of the wavelengths of interest, and preferably between
about 0.5% and about 3%.
[0069] The wavelengths of interest will depend on the application.
For example, if ICG is injected into and excited in a human being,
the wavelengths of interest will include the wavelengths at which
ICG emits energy. In such an application, the wavelengths of
interest might be 825-830 nm. In a preferred embodiment, the
coating is optimized to minimize reflectance both in the infrared
and visible spectrums, thus allowing viewing in both the infrared
and visible spectrums. The visible spectrum is commonly considered
to be between about 400 nm and about 700 nm.
[0070] The coating preferably includes alternating layers or pairs
of layers. These pairs include a high and a low index coating
material that together make up a pair. Suitable pairs include
TiO.sub.2 and MgF.sub.2, TiO.sub.2 and SiO.sub.2, Zirconium Oxide
(ZrO.sub.2) and MgF.sub.2, and tantulum pentoxide (Ta.sub.2O.sub.5)
and SiO.sub.2. The number of repeating pairs that may be used is
between about 2 and about 100, preferably between about 2 and about
50, between about 2 and about 40, between about 2 and about 30, and
between about 2 and about 20 for any optical surface. In some
embodiments, the coating has a minimum of 6, 7, or 8 pairs. In
certain embodiments, the coating has a minimum of 4 pairs. In some
embodiments, the coating has a minimum of 10 pairs. A coating may
have one or more different pairs. A useful low index material is
SiO.sub.2 with an index of refraction of approximately 1.45 in the
visible. SiO.sub.2 would be paired with a high index material such
as Ta.sub.2O.sub.5, which has an index of 2.4 in the visible, in
slightly different ratio when placed on a low index of refraction
glass, such as BK7, than on a high index glass, such as N-SF57. In
some embodiments, a high refractive index material is one having an
index of refraction from about 1.9 to about 2.4 in the visible
spectrum as measured at 633 nm. A low refractive index, in some
embodiments, is one having an index of refraction from about 1.45
to about 1.8 as measured at 633 nm.
[0071] FIG. 7 illustrates an example of one such coating that is
optimized to have low reflectance around the emission range of ICG.
It is comprised of alternating layers of MgF.sub.2 and
TiO.sub.2.
[0072] FIG. 8 illustrates another example of a low reflectance
coating suitable for use in the relay optics of the invention. This
coating has alternating layers of SiO.sub.2 and TiO.sub.2, and one
pair of MgF.sub.2 and TiO.sub.2.
[0073] In choosing glasses or optical surfaces, the skilled artisan
considers a number of factors to favorably correct the optical
aberrations and cover the desired field of view on the detector
chosen with a minimum of uncorrected residual aberrations. In
choosing the glass type, factors to consider are measure of bending
power, index, a measure for their dispersing power, and geometric
variables such as radius of curvature, thickness of glass and
thickness of air, the order of glasses through the system and other
factors well within the ability of the skilled artisan. Glasses
used in the relay sections of the devices of the invention could,
for example, cover a range of about 1.5 to about 2.0 as a measured
by their index of refraction. While there are many air-glass
surfaces in a device of the invention, not every one will represent
a distinct coating choice. There may be groupings of glasses with
similar indices that will be coated in the same vacuum deposition
chamber run. For example, a grouping might be made of glasses with
an index range of 1.5 to 1.65, 1.65 to 1.7, and so forth. The
judgment will be made based on performance of the whole stack of
pairs used for the particular coating design. The criteria for the
design goals will include wavelengths and or range of interest
chosen and their relative weighing at measurable points, angles of
incidence chosen and their relative weighing, environmental
considerations, and cost.
[0074] The thin film designer, in designing a coating suitable for
one or more relay glasses, considers, for example, pairs of high
and low index material, their individual thickness (in optical
terms, i.e. they are wavelength dependent because they have an
index of refraction), their pair thickness, and the substrate glass
index. Antireflective coatings and dielectric mirrors are discussed
in the publication Electromagnetic Waves and Antennas, published by
Sophocles J. Orfanidis on the website
<http://www.ece.rutgers.edu/.about.orfanidi/ewa> which are
attached at the end of this specification.
[0075] In some embodiments, devices such as a "chip-on-a-stick" do
not use relay optics, but rather pass light energy from the distal
section 3 to the proximal section 29 through fiber optics. In such
embodiments, the skilled artisan will understand that there are no
relay optics to be coated. Chip-on-a-stick designs eliminate the
proximal position of the detector and move said detector plane to
the image plane of the objective lens assembly. The preferred
inventive chip-on-a-stick design only images in the infra red
spectrum though those that image in both the infra red and visible
spectrum are within the scope of the invention.
C. Summary of Dichroic Filter and Cameras
[0076] Referring to FIGS. 3, 4, 5, 9, 10, and 11, the beam
splitting proximal prisms/dichroic filters 31 receive light from
relay section 2 or the exit pupil of a distal section 3 and focuses
light onto the detectors 33. In some embodiments, the relayed image
only includes light in the infra red spectrum. This image is
directed to detector 33b which may be a single charge coupled
device (CCD) or complementary metal-oxide semiconductor (CMOS) or
any other type of detector that can detect infrared light. While
infrared blocking filters are commonly used to block out infrared
light in endoscopes that do not obtain infrared images, the skilled
artisan will understand that such filters should not be used in
this embodiment.
[0077] In certain embodiments, the device is configured to
visualize both in the infrared and visible spectrum. Thus, the
light energy received from the distal and relay sections is in both
the visible and infrared spectrum. In this embodiment, the proximal
prisms 31 separate the wavelengths and relay them to detectors
capable of detecting appropriate wavelengths.
[0078] The proximal prisms 31 must have substantially equal path
lengths to each detector 33 to yield similar magnifications for
such comparisons or superimposed imaging. These proximal prisms 31
could take many forms, but they share approximately equal path
lengths per detector and the use of dichroic filters that
substantially enhance the optical efficiency or throughput of the
system when compared with metalized beam splitter coatings.
[0079] Preferably, the ratio of the unfolded optical path length to
diameter ratio in each light pathway through the proximal prism
assembly is given by:
1.75W<L<3W [0080] where [0081] W is the diagonal of the exit
face of the unfolded path of any or all of the prisms [0082] L is
the path length along the optical axis and corresponds to the focal
length of the focusing optics minus an air space on either side of
L
[0083] As described above, ICG has a peak excitation wavelength at
805 nm. The range of excitation wavelengths capable of exciting ICG
ranges from approximately 710 nanometers to 840 nanometers, or
more. This range overlaps the fluorescence range of ICG whose peak,
.lamda..sub.f, is 835 nanometers. The challenge is that the
fluorescent return signal, in the near infrared (NIR) for example,
can be significantly lower than that of the visible channels which
are transmitting a scattered return. This differential between low
fluorescent return and normal visible return requires not only
highly efficient coatings not found on normal endoscopes and wands
but also improvements associated with the detector assembly. An
optical design optimized for the visible is slightly different than
that of an optical design for visible (VIS) plus NIR imaging.
However, a comparable design can be used for both regions, if the
back focus is allowed to vary in length along the z or optical
axis. A NIR image is formed behind that of a visible wavelength of
either Red, Green or Blue because NIR wavelengths are longer; hence
we want to vary the back focus of the NIR image found exiting the
face of the proximal prism assembly.
[0084] In certain embodiments, the proximal prism assembly 31 is
organized by wavelength in a short to long or long to short order
by means of dichroic beam-splitting coatings contained within the
prism assembly. For example, in the case of a 4 channel prisms
associated with three detectors that detect in the visible range,
and one detector that detects in the infrared range,
.lamda.1<.lamda.2<.lamda.3<.lamda.4. Thus, .lamda.1,
.lamda.2, and .lamda.3 are associated with 400 nm to 700 nm and
.lamda.4 is dedicated to 810 nm to 870 nm, approximately for the
long pass configuration.
[0085] An imaging pathway will require a barrier or secondary
filter required to block the excitation radiation from reaching the
detectors. This barrier filter is a dichroic filter made up of high
and low index materials evaporated onto a substrate whose
arrangement disposes the filter to have a lower and upper cutoff
encompassing a range of wavelengths above that of the excitation
wavelength, .lamda..sub.e, whose peak is 805 nm for ICG. The
skilled artisan will understand that other dyes will have other
.lamda..sub.e and will hence require different filters for imaging.
Wavelength ranges below the cutoff frequency must be blocked to an
optical density of 5 or more so that the detector does not view any
portion of the energy from the illumination source, as it may be 2
or more orders of magnitude more intense than the fluorescent
response. The dichroic filter may be positioned as a plane parallel
plate orthogonal to the optical axis or at some preferential angle
to minimize ghost images.
[0086] To maximize the lens coupling efficiency to the detector it
is important to design the focusing optics and beamsplitting prism
assembly to produce a marginal ray angle in the corner of the field
which departs from the opto-mechanical axis by 10 or 15 degrees or
less from the last optical element in the focusing optics to the
detector. It is in this path that the prism assembly 31 is placed.
By possessing a shallow marginal ray angle, the ray paths from the
various fields within the prism reflect or pass the dichroic
filters 31 at a nearly common angle or over a small range of
angles. The more similar these angles, the better optical
efficiency or throughput for each wavelength range, as dichroic
filters by their nature are angle sensitive. Preferably, these
angles do not differ from each other by more than 10, 9, 8, 7, 6,
5, 4, 3, 2, or 1 degrees.
[0087] Moreover, due to the low signal strength in the NIR path of
the weak fluorescent scenes the f-number of the combined NIR VIS
focusing and beamsplitting assembly should be as fast as possible
for increased sensitivity. The increased sensitivity yields a
larger cone angle from the last focusing element through the
beamsplitting assembly creating a larger angle range than would be
required for VIS imaging alone. Likewise, it is important to make
each channel's ray path similar in length so that the resulting
image height, magnification, on all detectors is comparable.
[0088] In the case of exceptionally weak NIR fluorescent signals, a
cooled or intensified detector may be used on the NIR path. The
improved sensitivity may be provided by an intensified CCD (ICCD)
or electron multiplying CCD (EMCCD). Similarly, an intensifier or
cooler means may be integrated to the infrared detector or
beamsplitting assembly associated with the detector to make an
integrated and compact system. A barrier filter may be used
adjacent to an infrared detector to remove wavelengths outside
those of interest.
[0089] In certain embodiments, a total of two detectors 33 are used
(see e.g., the top prism 31 in FIG. 4 and FIG. 9). One detector 33a
detects light in the visible spectrum and the second detector 33b
detects light in the infrared spectrum. Proximal prism assembly 31
includes a first channel 31a and a second channel 31b.
[0090] Light from the relay section 2 enters channel 31a through
surface 34a. Visible light is transmitted through surface 34b and
34c to a polychromatic detector 33a. The polychromatic detector 33a
may be a single CCD or CMOS detector with an integrated color
filter, such as a Bayer pattern directly on the detector.
[0091] Infrared light from relay section 2 is reflected by surface
34b and 34c onto surface 34d, through which it is transmitted to
infrared detector 33b. Acceptable infrared detectors for any
embodiments described herein include silicon. Silicon is the base
material of almost all detectors commonly used, and it has a peak
efficiency in the near infra red spectrum.
[0092] In certain embodiments (FIGS. 4 and 10), a 4 channel prism
assembly 31 is used. Prism assembly 31 includes a channel for each
of red, green, blue, and infrared, and is coupled to a detector
capable of detecting such light. In the case of the 4 channel prism
the 4.sup.th detector is into the page and not seen.
[0093] Thus, in certain embodiments, multiple detectors are present
in an endoscope of the invention. Preferably, the diagonal of the
infrared detector or intensifier associated with the infrared
detector is approximately the same length as the diagonal of one or
more of the other detectors that image in another spectrum.
[0094] Acceptable dichroic coatings which may be used within the
context of the 2 and 4 channel prisms (31) may be purchased from
Feldmann Optics in Wetzlar Germany, for example. Prism surfaces
designed to transmit the wavelengths of interest are preferably
coated as described in the transmitting members section, above.
[0095] The detectors 33a and 33b are synchronized and the frame
grabber sends signals from all detectors to a computer. The sent
data is input in video RAM. The user can access one or both of the
visible and/or infrared images. Preferably, the computer includes
computer program code that, when executed, gives the user the
choice to either see (a) the visible image, (b) the infra red
image, (c) both simultaneously (i.e., one superimposed over the
other) with controls to dim the visible image, for example, so
there is some color information in the displayed image, (d)
alternating display of visible and infra red images, and/or (e)
side by side viewing in different windows. Preferably, when both
infra red and visible images are obtained, the two sets of images
are viewed with perfect or substantially perfect registration.
[0096] In certain embodiments, field sequential illumination
technology, such as described in U.S. Pat. No. 6,960,165, U.S. Pat.
No. 6,388,702, and U.S. Pat. No. 6,907,527 may be used These
patents are incorporated herein by reference in their entirety.
[0097] A number of functionalities are made possible because
detectors 33 detect one or both of infrared and visible light. For
example, in embodiments where multiple detectors 33 are used (e.g.,
an infrared and a visible light detector), the detectors may have
an automatic gain function. For example, the two detectors may send
information to the computer 360 indicating the amount of energy
detected by each. The computer 360 may have computer code for
adjusting the gain of each camera based on this information. In
some embodiments, the user may adjust the gain of the detectors
through a computer interface.
[0098] CMOS sensors allow gain manipulation of individual
photodiodes, region-of-interest read-out, high speed sampling,
electronic shuttering and exposure control. They have a large
dynamic range as well as a format for the computer interface. The
skilled artisan will understand that the gain of individual pixels
may be asynchronously modified in CMOS detectors. For example,
areas for which greater performance is required may be made more
sensitive. Similarly, in certain areas, response from the detectors
may be decreased to, for example, counteract blooming. Such
fine-tuning may be effected by the user or automatically as
described above.
[0099] In certain embodiments, the detectors may be used to
regulate the amount of illumination emitted by the illumination
source(s) 220. This is particularly important as infrared energy
may be harmful to humans, and while the photo bleaching properties
of dyes such as ICG provide an upper limit on the energy applied to
the tissue and require low dosages of wavelengths not unlike red in
amounts of approximately 50 milliwatts per cm squared. Nonetheless,
the perception of NIR as wavelengths which produce a substantial
amount of heat is well founded. For example, detectors 33b and 33a
automatically sense exposure levels of infra red energy and visible
energy, respectively, and electronically communicate this
information to the computer 360. Software on the computer may then
compare the energy level indications received from the different
detectors 33a and 33b. If the software determines that the level of
infrared energy exceeds the level of visible light energy, the
software may instruct the computer 360 to decrease the output of
the infrared illumination source. In certain embodiments, the
software may have a pre-set threshold or may allow a user to set a
threshold as to an acceptable difference in energy output between
different power sources. If a determination is made that the
infrared detected energy exceeds the detected visible light energy
by the threshold amount, the computer will then instruct the
illumination source 220 to decrease output.
[0100] In some embodiment, if the software on the computer 360
determines that no infrared energy is being detected by the
infrared detector, it may instruct the infrared camera to cease
transmitting information to the computer or no longer use
information transmitted from the infrared detector in calculations
and imaging.
[0101] In some embodiments, proximal section 29 comprises an ocular
member with an exit window. Such a window is useful to a physician
who wishes to look through the endoscope without a camera. Proximal
prisms will be provided to relay a visible image to the window, or
the visible/infra red proximal prism camera invention may be
used.
[0102] In certain embodiments, the physician may not wish to image
in the infrared spectrum. In such embodiments, the infrared camera
may be turned off, powered down or removed from the endoscope. In
preferred embodiments, such turning off, powering down or removal
will activate sensors or be otherwise detected by the computer,
which will then send a shut off command to the infrared
illumination source.
[0103] Preferably, where the aspect ratio of the prism contained
within the focused beam path to the detector is defined by the exit
face to the prism, the face in near proximity to the detector, and
its length, as defined by the path along the optical axis,
-yields:
0.167<D/L<0.25 [0104] where: [0105] D is defined by the
diameter of the exit face, and [0106] L is the path along the
optical axis contained within the prism
[0107] In certain embodiments, the proximal prism assembly is
removable from the endoscope eyepiece or last optical relay member,
thus requiring a focusing lens assembly that focuses the relayed
light from the relay section of endoscope 260 to an external exit
pupil. This focusing lens assembly is preferably color corrected to
produce comparably sized images free of dominating aberrations in
each of the desired color bands and corrected to compensate for the
positioning of the compact proximal color splitting prism assembly.
The focusing assembly must be telecentric in object space, that
space between the endoscope relay and the detachable compact prism
assembly first optical element. In the case of a proximal prism
assembly detachable from an endoscope eyepiece the focusing lens
assembly must have an external entrance pupil that maps or is
positioned in close proximity to the exit pupil of the endoscope
eyepiece.
[0108] In the later case an endoscope exit pupil cannot be designed
much larger than the human eye pupil that views it. The mismatch
between human eye pupil and endoscope exit pupil would be seen as a
reduction in brightness by the user of the endoscope when used
without a camera, whereas the larger the pupil the faster the
f-number of the focusing lens assembly and more sensitive the
system from the camera or detector's point of view.
III. Light Sources
[0109] The invention further provides a non-laser infra-red light
source that can be used with endoscopes, wands, macro telephoto
imagers, or any other imaging device that is capable of receiving
an optical fiber. Thus, the dangers associated with lasers, such as
damage to a user's or subject's retina are removed or minimized. In
some embodiments, the non-laser source is part of a combined
illumination source comprised of both VIS and NIR illumination. In
certain other embodiments, the non-laser source is contained in a
distinct housing (e.g., a light box) in optical communication with
the imaging device through fiber optics.
[0110] Referring now to FIG. 11, the light source includes light
emitting member. Light emitting member is any light emitter that
emits light energy in the infra red spectrum. Examples include
tungsten halogen, xenon, and metal halide bulbs or arcs. In some
embodiments, a member that emits in multiple wavelength ranges
(e.g, infra red and visible) is chosen.
[0111] The light source includes an integrated reflector.
Preferably, the reflector captures a significant portion of the
total source power of the bulb or arc. An elliptical reflector
captures a significant portion of the solid angle of the source
when the reflector is positioned at one of the two foci of the
ellipse, where the reflector can then redirect energy from the
source arc or filament to the second foci defined by the elliptical
reflector. In other embodiments, the reflector is parabolic.
[0112] The reflector has a coating that reflects infra red light to
the beamsplitter that separates light of different wavelength.
Infra red light from beamsplitter is then focused onto light fiber
by optical assembly. The light fiber for NIR has a diameter and
acceptance angle to favorably capture a substantial portion of the
infra red light. Preferably, the beamsplitter routes light in the
range of about 750 nm and about 800 nm to the optical assembly. In
one embodiment, the numerical aperature is between about 0.4 and
about 0.66. In some embodiments, the numerical aperture is between
about 0.55 and about 0.66 NA. Such a combined VIS and NIR source
can be used to provide illumination for endoscopes, wands, and
macrotelephoto imaging devices used for NIR fluorescent imaging or
combined VIS and NIR fluorescent imaging in either mono or stereo
viewing mode.
[0113] In cases where the reflector is elliptical, the light member
will be positioned approximately at the first foci of the ellipse,
and the light fiber will be positioned approximately at the second
foci which may be reimaged by a condenser lens assembly with a
collimated or nearly collimated section between the said condenser
lenses. Preferably, an assembly of collimating and focusing lenses
is positioned between the member and the light beam splitter to
collimate the light directed to beamsplitter 320. The advantage of
the above configuration is the creation of near parallel paths of
rays, the collimated condition, when intersecting a dichroic
coating. The cut on cut off slope of such a coating is steeper if
all rays are more or less parallel when interacting with the
coating, therefore making it more efficient at dividing a
spectrum.
[0114] In certain embodiments, the integrated reflector is
parabolic. In these embodiments, the reflected light will be
approximately collimated, and a collimating assembly may not be
necessary to collimate the reflected light. A focusing lens or lens
assembly is required to focus the energy from the source to the
fiber optic cable.
[0115] Reflectors of other shapes may be used. Examples include: a
reflector whose shape is modified to compensate for the aberrations
of the glass envelope surrounding an arc source.
[0116] As discussed above, reflector has a coating for
preferentially reflecting light in the infra red spectrum.
Preferably, light at wavelengths between about 750 nm- about 820 nm
is reflected. In certain embodiments, light between about 750 nm
and about 800 nm is reflected. In some embodiments, light having a
wavelength of between about 770 and 800 nm is reflected. In some
embodiments, a coating is chosen that reflects significant amounts
of light in multiple spectrums (e.g., ultraviolet, visible and/or
infrared) and/or within multiple ranges within one or more of these
spectrums.
[0117] In some embodiments, the coating is one of gold, silver or
aluminum. Gold is particularly preferred for reflecting only
wavelengths in the near infra red spectrum. Silver is particularly
preferred for reflecting wavelengths in the visible and near infra
red spectrums. These coatings can be preferably applied directly to
the reflecting reflector 310 and are between about 1 and about 20
micrometers in thickness, and preferably between about 1 and about
10 micrometers in thickness. They can be purchased from, for
example, TYDEX J.S.Co. (St. Petersburg, Russia) and vapor deposited
onto the surface of interest by any number of thin film coaters in
the world using vacuum deposition chambers. Gold coatings are
especially preferred because they reflect well in the near IR. In
some embodiments, any coating that reflects at least 80%,
preferably at least 90% and most preferably at least 95% of light
energy that is within the wavelengths of interest may be used. A
second coating, such silicon dioxide (SiO.sub.2), magnesium
fluoride, silicon monoxide or a dielectric overcoat may be applied.
Such coatings can be purchased from, for example, OFR, Inc.,
Caldwell, N.J. In some embodiments, the coating is a dichroic
coating or mirror (provided by a coating supplier such as Omega
Optical Inc. Brattleboro, Vt. or Chroma Technology Corp.,
Rockingham, Vt.) A coating of gold, silver or aluminum is preferred
over dichoroic coatings for efficiency since they are angle
sensitive and such coatings could, over the collecting surface of
the reflector, vary in efficiency.
[0118] Referring now to the beamsplitter, it routes energy in the
infra red spectrum to light fiber. The light energy routed to light
fiber is within the spectrum desired for imaging. In other words,
if the dye being used is ICG, the beamsplitter will direct light to
the light guide that is capable of exciting the ICG. For example,
it may have a wavelength between about 750- about 820 nm, and more
preferably between about 750 nm and 800 nm, or between about 770 nm
and about 800 nm. The beam splitter may be an optical plate coated
with, or cube containing a dichroic coating or interference filter
such as a high/low index pair coating described above in relation
to the endoscope relay section. The configuration of such an
interference filter varies from transmission filters in selection
and placement of high/low index pairs to optimize blockage and
spectral width. In some embodiments, the beamsplitter assembly may
require an absorptive filter that absorbs light rays that are at a
wavelength above or below the wavelengths of interest. If the
energy is sufficiently intense there may be excess heating that can
be ameliorated with the addition of a fan.
[0119] FIG. 12 shows another embodiment of the light source. It is
similar to the previously described light source except that the
light member includes a second optical fiber that provides light at
different wavelengths than the first optical fiber. Thus, it can be
used for multimodal imaging (e.g., simultaneous imaging in the
infra red spectrum and also imaging in the visible spectrum). In
this embodiment, light emitting member is chosen such that it
produces light both in the infra red and in the second desired
range. Preferably, the second range is within the visible spectrum
of about 400 nm to about 700 nm. Reflector includes a coating that
reflects light in both the infra red and in the second desired
range, e. g., silver. The beam splitter than routes light within
the second desired range to second light fiber.
[0120] In some embodiments, additional absorptive filters may be
placed between beamsplitter and one or more of the first and second
light fibers to further reduce unwanted energy. Locating these
filters in this position has several advantages. The first is;
there is physically more room than the earlier case where the
absorbing filters were located between the first and second foci of
the elliptical reflector. The second advantage is also associated
with more space, as the beam diameter may be larger than in the
converging beam path between the two foci. This results in less
flux density on the filter and less substrate heating in the
filter. Thirdly, more room results in freedom to use more filters
of differing configurations. Fourthly, more room permits the use of
thicker more efficient absorptive filters.
[0121] In certain embodiments, the alpha angle of the light
emitting member, the reflector and focusing lens in a
one-dimensional direction satisfy the condition of 0.42 for the
ratio of D/L<tan alpha<1.4 D/L where alpha is the angle of
the marginal ray and where D is one half of the effective diameter
of the reflector adjacent to the light emitting member 300 or
focusing lens to insert energy from light emitting member 300 to
the light fiber and L is the distance from the limiting aperture of
either the reflector or focusing lens.
[0122] Many modifications and variations of this invention can be
made without departing from its spirit and scope, as will be
apparent to those skilled in the art. The specific embodiments
described herein are offered by way of example only and are not
meant to be limiting in any way. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *
References