U.S. patent application number 13/882004 was filed with the patent office on 2013-11-07 for optical systems for multi-sensor endoscopes.
This patent application is currently assigned to Peer Medical Ltd.. The applicant listed for this patent is Yaniv Kirma, Moshe Levi, Victor Levin. Invention is credited to Yaniv Kirma, Moshe Levi, Victor Levin.
Application Number | 20130296649 13/882004 |
Document ID | / |
Family ID | 45994487 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130296649 |
Kind Code |
A1 |
Kirma; Yaniv ; et
al. |
November 7, 2013 |
Optical Systems for Multi-Sensor Endoscopes
Abstract
There is provided herein an optical system for a tip section of
a multi-sensor endoscope, the system comprising: a front-pointing
camera sensor; a front objective lens system; a side-pointing
camera sensor; and a side objective lens system, wherein at least
one of said front and side objective lens systems comprises a front
and a rear sub-systems separated by a stop diaphragm, said front
sub-system comprises, in order from the object side, a first front
negative lens and a second front positive lens, said rear
sub-system comprises, in order from the object side, a first rear
positive lens, an achromatic sub-assembly comprising a second rear
positive lens and a third rear negative lens, wherein the following
condition is satisfied: f.sub.(first rear positive
lens).ltoreq.1.8f, where f is the composite focal length of the
total lens system and f.sub.(first rear positive lens) is the focal
length of said first rear positive lens.
Inventors: |
Kirma; Yaniv; (Tzrufa,
IL) ; Levin; Victor; (Haifa, IL) ; Levi;
Moshe; (Ganey Tikva, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kirma; Yaniv
Levin; Victor
Levi; Moshe |
Tzrufa
Haifa
Ganey Tikva |
|
IL
IL
IL |
|
|
Assignee: |
Peer Medical Ltd.
Caesarea
IL
|
Family ID: |
45994487 |
Appl. No.: |
13/882004 |
Filed: |
October 27, 2011 |
PCT Filed: |
October 27, 2011 |
PCT NO: |
PCT/IL11/00832 |
371 Date: |
May 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61407495 |
Oct 28, 2010 |
|
|
|
Current U.S.
Class: |
600/109 ;
359/754 |
Current CPC
Class: |
G02B 13/005 20130101;
G02B 7/04 20130101; A61B 1/00096 20130101; G02B 13/001 20130101;
G02B 13/06 20130101; G02B 23/2461 20130101; A61B 1/05 20130101;
G02B 13/0015 20130101; G02B 23/2484 20130101; G02B 23/2476
20130101; G02B 23/243 20130101; G02B 9/60 20130101; A61B 1/00181
20130101; G02B 23/2407 20130101; A61B 1/00177 20130101; G02B 13/04
20130101; A61B 1/00188 20130101 |
Class at
Publication: |
600/109 ;
359/754 |
International
Class: |
G02B 23/24 20060101
G02B023/24; A61B 1/00 20060101 A61B001/00; A61B 1/05 20060101
A61B001/05 |
Claims
1. An optical system for a tip section of a multi-sensor endoscope,
the system comprising: a front-pointing camera sensor; a front
objective lens system; a side-pointing camera sensor; and a side
objective lens system, wherein at least one of said front and side
objective lens systems comprises a front and a rear sub-systems
seperated by a stop diaphragm, said front sub-system comprises, in
order from the object side, a first front negative lens and a
second front positive lens, said rear sub-system comprises, in
order from the object side, a first rear positive lens, an
achromatic sub-assembly (optionally, a compound achromatic
sub-assembly) comprising a second rear positive lens and a third
rear negative lens, wherein the following condition is satisfied:
f.sub.(first rear positive lens).ltoreq.1.8f, where f is the
composite focal length of the total lens system and f.sub.(first
rear positive lens) is the focal length of said first rear positive
lens.
2. The optical system according to claim 1, wherein said front
sub-system further comprises an additional front meniscus lens
disposed between said first front negative lens and said second
front positive lens.
3. The optical system according to claim 1, wherein said rear
sub-system further comprises a rear protective glass situated
between said third rear negative lens and said front-pointing
and/or side-pointing camera sensor, wherein said rear protective
glass is adapted to protect a detector array of said front-pointing
and/or side-pointing camera sensor.
4. The optical system according to claim 1, wherein: f.sub.(first
rear positive lens)=1.8f, where f is the composite focal length of
the total lens system and f.sub.(first rear positive lens) is the
focal length of said first rear positive lens.
5. The optical system according to claim 1, wherein said
front-pointing camera sensor and said front objective lens system
are adapted to provide a Depth of Focus (DOF) of between 4 and 110
mm.
6. The optical system according to claim 5, wherein said
front-pointing camera sensor and said front objective lens system
are adapted to provide a Depth of Focus (DOF) of between 3.5 and 50
mm.
7. The optical system according to claim 1, wherein said
front-pointing camera sensor and said front objective lens system
are adapted to provide an effective spatial resolution of at least
60 lines per mm at Depth of Focus (DOF) of between 5 and 50 mm.
8. The optical system according to claim 1, wherein said
front-pointing camera sensor and said front objective lens system
are adapted to provide an effective angular resolution of about 2'
per degree or less at Depth of Focus (DOF) of between 5 and 50
mm.
9. The optical system according to claim 1, wherein said
front-pointing camera sensor and said front objective lens system
are adapted to provide a Field of View (FOV) of about 150 degrees
or more.
10. The optical system according to claim 9, wherein said
front-pointing camera sensor and said front objective lens system
are adapted to provide a Field of View (FOV) of about 170 degrees
or more.
11. The optical system according to claim 1, wherein said
front-pointing camera sensor and said front objective lens system
have a total optical length of about 5 mm or less.
12. The optical system according to claim 1, wherein said
side-pointing camera sensor and said side objective lens system are
adapted to provide a Depth of Focus (DOF) of between 3.5 and 50
mm.
13. The optical system according to claim 1, wherein said
side-pointing camera sensor and said side objective lens system are
adapted to provide a Depth of Focus (DOF) of between 3 and 30
mm.
14. The optical system according to claim 1, wherein said
side-pointing camera sensor and said side objective lens system are
adapted to provide an effective spatial resolution of at least 60
lines per mm at Depth of Focus (DOF) of between 5 and 50 mm.
15. The optical system according to claim 1 wherein said
side-pointing camera sensor and said side objective lens system are
adapted to provide an effective angular resolution of about 2' per
degree or less at Depth of Focus (DOF) of between 5 and 50 mm.
16. The optical system according to claim 1, wherein said
side-pointing camera sensor and said side objective lens system are
adapted to provide a Field of View (FOV) of about 150 degrees or
more.
17. The optical system according to claim 1, wherein said
side-pointing camera sensor and said side objective lens system are
adapted to provide a Field of View (FOV) of about 170 degrees or
more.
18. The optical system according to claim 1, wherein said
side-pointing camera sensor and said side objective lens system
have a total optical length of about 5 mm or less.
19. The optical system according to claim 1, wherein the diameter
of said first front negative lens is 2.5 mm or less.
20. An objective lens system for at least one of a front-pointing
and side-pointing camera sensors of a multi-sensor endoscope, the
objective lens system comprising: a front and a rear sub-systems
separated by a stop diaphragm, wherein said front sub-system
comprises a first front negative lens and a second front positive
lens, and said rear sub-system comprises a first rear positive
lens, an achromatic sub-assembly (optionally, a compound achromatic
sub-assembly) comprising a second rear positive lens and a third
rear negative lens, wherein the following condition is satisfied:
f.sub.(first rear positive lens).ltoreq.1.8f, where f is the
composite focal length of the total lens system and f(first rear
positive lens) is the focal length of said first rear positive
lens.
21. A tip section of a multi-sensor endoscope comprising an optical
system comprising: a front-pointing camera sensor; a front
objective lens system; a side-pointing camera sensor; and a side
objective lens system, wherein at least one of said front and side
objective lens systems comprises a front and a rear sub-systems
seperated by a stop diaphragm, said front sub-system comprises a
first front negative lens and a second front positive lens, said
rear sub-system comprises a first rear positive lens, an achromatic
sub-assembly (optionally, a compound achromatic sub-assembly)
comprising a second rear positive lens and a third rear negative
lens, wherein the following conditions are satisfied: f.sub.(first
rear positive lens).ltoreq.1.8f, where f is the composite focal
length of the total lens system and f.sub.(first rear positive
lens) is the focal length of said first rear positive lens.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a national stage entry of PCT
Application Number PCT/IL2011/000832, entitled "Optical Systems for
Multi-Sensor Endoscopes" and filed on Oct. 27, 2011, which relies
on U.S. Provisional Patent Application No. 61/407,495, filed on
Oct. 28, 2010, for priority, both of which are hereby incorporated
by reference in their entirety.
FIELD OF THE INVENTION
[0002] This invention relates to a wide FOV objective lens system
for an endoscope.
BACKGROUND
[0003] Endoscopes have attained great acceptance within the medical
community, since they provide a means for performing procedures
with minimal patient trauma, while enabling the physician to view
the internal anatomy of the patient. Over the years, numerous
endoscopes have been developed and categorized according to
specific applications, such as cystoscopy, colonoscopy,
laparoscopy, upper GI endoscopy and others. Endoscopes may be
inserted into the body's natural orifices or through an incision in
the skin.
[0004] An endoscope is usually an elongated tubular shaft, rigid or
flexible, having a video camera or a fiber optic lens assembly at
its distal end. The shaft is connected to a handle, which sometimes
includes an ocular for direct viewing. Viewing is also usually
possible via an external screen. Various surgical tools may be
inserted through a working channel in the endoscope for performing
different surgical procedures.
[0005] There are known various endoscopes employing in their front
insertion part, optical heads for viewing the interior of a body
cavity or lumen such as the lower digestive track. Such optical
head normally includes at least an illumination means for
illuminating the object, an objective lens system and a sensor
array.
[0006] U.S. Pat. No. 6,956,703 discloses an objective lens for
endoscopes comprises a front lens unit component and a rear lens
unit component, between which a aperture stop is located, wherein
the front lens unit component comprises, in order from the object
side, a first lens having a negative refractive power, and a second
lens having a positive refractive power which directs a surface of
the small radius of curvature toward the object side; wherein the
rear lens unit component comprises a third lens having a positive
refractive power which directs a surface of the small radius of
curvature toward the image side, a fourth lens having a positive
refractive power, and a fifth lens having a negative refractive
power; and wherein the fourth lens and the fifth lens are cemented.
The following condition is satisfied: 2.0<|f3/f|<3.0 where f
is the composite focal length of the total system and f 3 is the
focal length of the third lens. Still, the complexity of the
objects that are inspected by the endoscope (for example, the
asymmetric colon environment), requires high quality images
capturing a wide Field of View (FOV), which cannot be accomplished
using only one detector.
[0007] More efforts have been undertaken to improve the optical
design of these systems and to create a wide FOV, as seen for
example, in U.S. Pat. No. 5,870,234 entitled "Compact wide angle
lens", as well as U.S. Pat. No. 6,476,851 entitled "Electronic
endoscope". Although these patents bring the advantage of a wide
FOV they mainly provide a front view. Another disadvantage is a
significant distortion in the periphery looking at the borders of
the wide view image.
[0008] These disadvantages may be partially solved by using a multi
image lens for example as shown in US patent application number
2005/0168616 entitled "Methods and apparatus for capturing images
with a multi-image lens" or by using other Omni-directional optical
solutions, as disclosed, for example, in U.S. Pat. No. 7,362,516
entitled "Optical lens providing Omni-directional coverage and
illumination". These technologies may support a wide FOV with
relatively low distortion in the periphery of the image however
they suffer from a major disadvantage of low optical resolution on
side views. Another disadvantage of these technologies is the
complexity and space consuming design which typically eliminates
the possibility to combine other crucial features like jet, working
channels and illuminating sources to the endoscope.
[0009] There is still a need in the art for endoscopes, such as
colonoscopies, that provide a wide FOV, a wide range of Depth of
Field/Depth of Focus (DOF) and acceptable resolution within the
required dimensions of the device used of a medical
application.
SUMMARY
[0010] The following embodiments and aspects thereof are described
and illustrated in conjunction with systems, tools and methods
which are meant to be exemplary and illustrative, not limiting in
scope.
[0011] It is an object of the current invention to provide optical
system(s) for front looking and side looking cameras to be housed
in the same head (tip) of an endoscope. The cameras together with
their respective optic systems are adapted to provide a high
quality image capturing a wide FOV of the complex environment
examined by the use of the endoscope. According to some
embodiments, there is provided an endoscope comprising at least a
front looking camera and a side looking camera being essentially
perpendicular to one another. According to some embodiments any of
the cameras may include a small-sized image sensors such as CCD or
CMOS sensors (hereinafter referred to as CCD but can also mean CMOS
or any other sensor). In order to keep the outer diameter of the
front part of the endoscope as small as possible, the optical
systems used in the plurality of cameras need to be compact.
Specifically, optical track of the side looking camera needs to be
short. In the case where two side looking cameras are positioned
along the same axis, preferably essentially, perpendicular to the
long axis of the endoscope, the minimal diameter of the endoscope's
head is limited to at least twice the total length of the cameras
(which typically includes the optical track of the camera, the
sensor, and any electronic circuitry and wiring which may be
located behind the sensor). Shortening the total length should not
affect the FOV or cause distortion. Both optical characteristics
should be maintained together with minimal total length.
[0012] Additionally, working channel(s) and fluid channel(s) need
to traverse the endoscope's head. Thus, the diameter of the cameras
and its optical systems needs to be small to allow for space
occupied by the channels. Since different sensors may be used per
field of view it opens the opportunity for additional working
channels space giving big advantage to this application.
[0013] In order to effectively work within the confined space in a
body cavity, the cameras may be equipped with wide-angle lens,
capable of imaging close objects and a wide range of working
distances with preservation of image quality.
[0014] Optionally, several optical modules (cameras) in one
endoscope head, with similar or different designs may be used,
optionally each tuned to its desired Depth of Field (DOF).
[0015] According to some embodiments, there is provided herein an
optical system for a tip section of a multi-sensor endoscope, the
system comprising: a front-pointing camera sensor; a front
objective lens system; a side-pointing camera sensor; and a side
objective lens system, wherein at least one of the front and side
objective lens systems comprises a front sub-system and a rear
sub-system seperated by a stop diaphragm, wherein the front
sub-system comprises, in order from the object side, a first front
negative lens and a second front positive lens, the rear sub-system
comprises, in order from the object side, a first rear positive
lens, an achromatic sub-assembly comprising a second rear positive
lens and a third rear negative lens, wherein the following
condition is satisfied:
[0016] f.sub.(first rear positive lens).ltoreq.1.8f, where f is the
composite focal length of the total lens system and f.sub.(first
rear positive lens) is the focal length of the first rear positive
lens.
[0017] The front sub-system may further include an additional front
positive lens (such as a meniscus lens) disposed between the first
front negative lens and the second front positive lens (as seen,
for example, in FIG. 4c).
[0018] The rear sub-system may further include a rear protective
glass situated between the third rear negative lens and the
front-pointing and/or side-pointing camera sensor, wherein the rear
protective glass is adapted to protect a detector array of the
front-pointing and/or side-pointing camera sensor.
[0019] According to some embodiments, the front-pointing camera
sensor and the front objective lens system may be adapted to
provide a Depth of Focus (DOF) of between 4 and 110 mm. Optical
system having a Depth of Focus (DOF) of between 4 and 110 mm may
mean that the optical system is adapted to image objects at an
object distance of 4-110 mm. The front-pointing camera sensor and
the front objective lens system may be adapted to provide a Depth
of Focus (DOF) of between 3.5 and 50 mm. The front-pointing camera
sensor and the front objective lens system may be adapted to
provide an effective spatial resolution of at least 60 lines per mm
at Depth of Focus (DOF) of between 5 and 50 mm. The front-pointing
camera sensor and the front objective lens system may be adapted to
provide an effective angular resolution of about 2' per degree or
less at Depth of Focus (DOF) of between 5 and 50 mm. The
front-pointing camera sensor and the front objective lens system
may be adapted to provide a Field of View (FOV) of at least 150
degrees. The front-pointing camera sensor and the front objective
lens system may be adapted to provide a Field of View (FOV) of at
least 170 degrees.
[0020] According to some embodiments, the front-pointing camera
sensor and the front objective lens system have a total optical
length of 5 mm or less.
[0021] According to some embodiments, the side-pointing camera
sensor and the side objective lens system may be adapted to provide
a Depth of Focus (DOF) of between 3.5 and 50 mm. The side-pointing
camera sensor and the side objective lens system may be adapted to
provide an effective spatial resolution of at least 60 lines per mm
at Depth of Focus (DOF) of between 5 and 50 mm. The side-pointing
camera sensor and the side objective lens system may be adapted to
provide a Depth of Focus (DOF) of between 3 and 30 mm. The
side-pointing camera sensor and the side objective lens system may
be adapted to provide an effective angular resolution of about 2'
per degree or less at Depth of Focus (DOF) of between 4.5 and 25
mm. The side-pointing camera sensor and the side objective lens
system may be adapted to provide a Field of View (FOV) of at least
150 degrees. The side-pointing camera sensor and the side objective
lens system may be adapted to provide a Field of View (FOV) of at
least 170 degrees.
[0022] According to some embodiments, the side-pointing camera
sensor and the side objective lens system may have a total optical
length of 5 mm or less (for example, 4 mm or less, 3 mm or
less).
[0023] According to some embodiments, the diameter of the first
front negative lens may be 2.5 mm or less (without the barrel or
lens holder).
[0024] According to some embodiments, there is provided an
objective lens system for at least one of a front-pointing camera
sensor and a side-pointing camera sensor of a multi-sensor
endoscope, the objective lens system comprising: a front sub-system
and a rear sub-system separated by a stop diaphragm, wherein the
front sub-system comprises a first front negative lens and a second
front positive lens, and the rear sub-system comprises a first rear
positive lens, an achromatic sub-assembly comprising a second rear
positive lens and a third rear negative lens, wherein the following
condition is satisfied:
[0025] f.sub.(first rear positive lens).ltoreq.1.8f, where f is the
composite focal length of the total lens system and f(first rear
positive lens) is the focal length of the first rear positive
lens.
[0026] According to some embodiments, there is provided a tip
section of a multi-sensor endoscope comprising an optical system
comprising: a front-pointing camera sensor; a front objective lens
system; a side-pointing camera sensor; and a side objective lens
system, wherein at least one of the front and side objective lens
systems comprises a front sub-system and a rear sub-system
seperated by a stop diaphragm, the front sub-system comprises a
first front negative lens and a second front positive lens, the
rear sub-system comprises a first rear positive lens, an achromatic
sub-assembly comprising a second rear positive lens and a third
rear negative lens, wherein the following conditions are
satisfied:
[0027] f.sub.(first rear positive lens).ltoreq.1.8f, where f is the
composite focal length of the total lens system and f.sub.(first
rear positive lens) is the focal length of the first rear positive
lens.
[0028] More details and features of the current invention and its
embodiments may be found in the description and the attached
drawings.
[0029] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, suitable methods and materials are described below. In
case of conflict, the patent specification, including definitions,
will control. In addition, the materials, methods, and examples are
illustrative only and not intended to be limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Some embodiments of the invention are herein described, by
way of example only, with reference to the accompanying drawings.
With specific reference now to the drawings in detail, it is
stressed that the particulars shown are by way of example and for
purposes of illustrative discussion of the preferred embodiments of
the present invention only, and are presented in the cause of
providing what is believed to be the most useful and readily
understood description of the principles and conceptual aspects of
the invention. In this regard, no attempt is made to show
structural details of the invention in more detail than is
necessary for a fundamental understanding of the invention, the
description taken with the drawings making apparent to those
skilled in the art how the several forms of the invention may be
embodied in practice.
[0031] In order to understand the invention and to see how it may
be carried out in practice, embodiments will now be described, by
way of non-limiting example only, with reference to the
accompanying drawings, in which:
[0032] FIG. 1a schematically depicts an external isometric view of
an endoscope having multiple fields of view according to an
exemplary embodiment of the current invention.
[0033] FIG. 1b schematically depicts a front view of an endoscope
having multiple fields of view according to an exemplary embodiment
of the current invention.
[0034] FIG. 1c schematically depicts a side view of endoscope
having multiple fields of view according to an exemplary embodiment
of the current invention.
[0035] FIG. 2a schematically depicts a cross section of an
endoscope having multiple fields of view, for use within bodily
cavity according to an exemplary embodiment of the current
invention.
[0036] FIG. 2b schematically depicts a cross section of an
endoscope front head having multiple fields of view showing some
details of the head according to an exemplary embodiment of the
current invention.
[0037] FIG. 2c schematically depicts a cutout isometric view of an
endoscope having multiple fields of view according to another
exemplary embodiment of the current invention.
[0038] FIG. 2d schematically depicts another cutout isometric view
of an endoscope having multiple fields of view according to an
exemplary embodiment of the current invention.
[0039] FIG. 3 schematically depicts a cross section of a lens
assembly of a camera head, according to an exemplary embodiment of
the current invention.
[0040] FIG. 4a schematically illustrates example of light
propagation within an objective lens systems according to an
exemplary embodiment of the current invention.
[0041] FIG. 4b schematically illustrates another example of light
propagation within an objective lens system according to an
exemplary embodiment of the current invention.
[0042] FIG. 4c schematically illustrates another example of light
propagation within an objective lens system according to an
exemplary embodiment of the current invention.
DETAILED DESCRIPTION
[0043] Before explaining at least one embodiment of the invention
in detail, it is to be understood that the invention is not
necessarily limited in its application to the details set forth in
the following description or exemplified by the Examples. The
invention is capable of other embodiments or of being practiced or
carried out in various ways.
[0044] The terms "comprises", "comprising", "includes",
"including", and "having" together with their conjugates mean
"including but not limited to".
[0045] The term "consisting of" has the same meaning as "including
and limited to".
[0046] The term "consisting essentially of" means that the
composition, method or structure may include additional
ingredients, steps and/or parts, but only if the additional
ingredients, steps and/or parts do not materially alter the basic
and novel characteristics of the claimed composition, method or
structure.
[0047] As used herein, the singular form "a", "an" and "the"
include plural references unless the context clearly dictates
otherwise. For example, the term "a compound" or "at least one
compound" may include a plurality of compounds, including mixtures
thereof.
[0048] Throughout this application, various embodiments of this
invention may be presented in a range format. It should be
understood that the description in range format is merely for
convenience and brevity and should not be construed as an
inflexible limitation on the scope of the invention. Accordingly,
the description of a range should be considered to have
specifically disclosed all the possible sub-ranges as well as
individual numerical values within that range.
[0049] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention, which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any suitable sub-combination
or as suitable in any other described embodiment of the invention.
Certain features described in the context of various embodiments
are not to be considered essential features of those embodiments,
unless the embodiment is inoperative without those elements.
[0050] In discussion of the various figures described herein below,
like numbers refer to like parts. In some cases, pluralities of
similar or identical elements are marked with same numbers followed
by letters, in some cases; same number without the letter refers to
any of these elements. The drawings are generally not to scale. For
clarity, non-essential elements were omitted from some of the
drawing.
[0051] The optical setup for endoscopes typically used in the prior
art requires a relatively large overall optical length (total
optical track) of the entire optical system, which is
disadvantageous for endoscopes, in particular those used as
colonoscopes and gastroscopes, particularly if used in endoscopes
having side-viewing camera or cameras, such as endoscopes according
to embodiments of the present invention.
[0052] In addition, in sensors (such as CCD sensors) used in
endoscopes of the prior art, the pixels are partially covered by a
photo-shielding film, so that the light energy is concentrated in
the center of the pixel, where there is a "window" in the
photo-shielding film. This improves the signal-to-noise ratio and
increases the light utilization efficiency. However, this also
causes the sensor to be sensitive to incident angles between the
light rays which have passed the micro-lenses of the sensor and the
optical axis of the system. Thus, light rays having relatively
small incident angles may reach the pixel, while light rays having
relatively large incident angles (between the light rays which have
passed the micro-lenses of the sensor and the optical axis of the
system) may not reach the "window" and thus the pixel, leading to
significant energy losses. The losses are maximized at the edges of
the field of view, i.e. for light rays having incident angles close
to that of the chief ray.
[0053] There is thus provided herein, according to some
embodiments, a lens system (assembly) configured for use in an
endoscope, such as colonoscope, particularly for use in a
multi-sensor endoscope/colonoscope. The lens system, (optionally
together with the sensor) according to some embodiments of the
invention, has a short total optical length (track), for example, 5
mm or less. The lens system, according to some embodiments of the
invention, is configured to provide a large incident angle, for
example, a chief incident angle (for example the incident angles
forming by rays R.sub.6 in FIGS. 4a-4c) larger than 20.degree.,
larger than 25.degree., larger than 30.degree. or between about
20-40.degree.. The lens system, according to some embodiments of
the invention provides minimal distortion (for example, less than
80%).
[0054] According to some embodiments, the sensor which is used
together with the lens system, is configured to have a window in
the photo-shielding film configured to allow rays having large
incident angle (for example, a chief incident angle larger than
20.degree., larger than 25.degree., larger than 30.degree. or
between about)20-40.degree. to reach the pixel and thus improve the
distortion. According to some embodiments, the width of the window
(or any other dimensional parameter) may be about 30-60% of the
width of the corresponding pixel. According to some embodiments,
the micro-lenses of the sensor may be configured to provide
substantially aplanatic conditions. In other words, the sensor may
be configured to provide an image substantially free of
aberrations.
[0055] FIG. 1a schematically depicts an external isometric view of
an endoscope (for example, a colonoscope) 200 having multiple
fields of view according to an exemplary embodiment of the current
invention.
[0056] According to an exemplary embodiment of the current
invention, head 230 of endoscope 200 comprises at least a forwards
looking camera (such as a TV camera) and at least one side looking
camera (such as a TV camera).
[0057] FIG. 1a shows front camera element 236 of forwards looking
camera 116 (seen in FIG. 2c) on the front face 320 of head 230. The
term "camera element" may generally refer to a camera and the
optical system/assembly related to the camera. Optical axis of
forwards looking camera 116 (seen for example in FIG. 2a) is
substantially directed along the long dimension of the endoscope.
However, since forwards looking camera 116 is typically a wide
angle camera, its Field of View (FOV) may include viewing
directions at large angles to its optical axis. Additionally,
optical windows 242a and 242b of discrete light sources such as
Light Emitting Diodes (LEDs) 240a and 240b are also seen on front
face 320 of head 230. It should be noted that number of LEDs used
for illumination of the FOV may vary. Distal opening 340 of working
channel 262 (seen for example in FIG. 2d) may preferably be located
on front face 320 of head 230, such that a surgical tool inserted
through working channel 262 and deployed beyond front face 320 may
be viewed by forwards looking camera 116.
[0058] Distal opening 344 of a fluid channel may preferably also be
located on front face 320 of head 230. The fluid channel leading to
distal opening 344 may be used as a jet channel for cleaning the
colon.
[0059] Liquid injector 346 having a nozzle 348 aimed at front
camera element 236 is used for injecting fluid to wash contaminants
such as blood, feces and other debris from front camera element 236
of forwards looking camera. Optionally the same injector is used
for cleaning both front camera element 236 and one or both optical
windows 242a and 242b. Injector 346 may receive fluid (for example,
water and/or gas) from the fluid channel or may be fed by a
dedicated cleaning fluid channel.
[0060] Visible on the side wall 362 of head 230 is the front camera
element 256 of side looking camera 220 (two such cameras are seen
in FIG. 2a) and optical window 252 of a discrete light sources such
as LED 250. It is noted that the number of the discrete light
sources may vary. Optical axis of side looking camera 220 may be
substantially directed perpendicular to the long dimension of the
endoscope. However, since side looking camera 220 is typically a
wide angle camera, its field of view may include viewing directions
at large angles to its optical axis.
[0061] Liquid injector 366 having a nozzle 368 aimed at front
looking camera element 256 is used for injecting fluid to wash
contaminants such as blood, feces and other debris from front
camera element 256 of side looking camera. Optionally the same
injector is used for cleaning both front camera element 256 and
optical windows 252. Preferably, injectors 346 and 366 are fed from
same channel. An optional groove 370 helps directing the cleaning
fluid from nozzle 368 towards front camera element 256. Groove 370
may be beneficial when side wall 362 is near or pressed against the
rectal wall. Optionally, injector 366 may be at least partially
recessed in groove 370, thus reducing the maximum diameter of head
230 and reduce the risk of injury to the rectal wall due to
friction with injector 366.
[0062] In the depicted embodiment, flexible shaft 260 is
constructed of a plurality of links 382 connected to each other by
pivots 384. Links 382 allows pushing, pulling and rotating the
endoscope while pivots 384 provide limited flexibility. The shaft
is preferably covered with an elastic sheath (removed for clarity
in this figure). The lumen in links 382 holds the working channel
262. Not seen in this figure are the fluid channel connected to
opening 344, optional cleaning fluid channel and electrical cables
supplying power to the LEDs and cameras and transmitting video
signals from the camera. Generally, the shaft may also comprise
mechanical actuators (not seen), for example cables attached to the
links for directing and aiming the head during use.
[0063] It should be noted that while only one side looking camera
is seen in FIG. 1a, optionally, according to some embodiments, two
or more side looking cameras may be located within head 230. When
two side looking cameras are used, the side looking cameras are
preferably installed such that their field of views are
substantially opposing. According to some embodiments, Different
configurations and number of side looking cameras are possible and
covered within the general scope of the current invention.
[0064] FIG. 1b schematically depicts a front view of head 230 of
endoscope 200 having multiple fields of view according to an
exemplary embodiment of the current invention.
[0065] According to an exemplary embodiment of the current
invention, head 230 of endoscope 200 comprises at least a forwards
looking camera and at least one side looking camera. FIG. 2b shows
a front camera element 236 of forwards looking camera 116 on the
front face 320 of head 230. Additionally, optical windows 242a and
242b of LEDs 240a and 240b are also seen on front face 320 of head
230. Distal opening 340 of working channel and distal opening 344
of a fluid channel are preferably also located on front face 320 of
head 230. Liquid injector 346 having a nozzle 348 is also visible
in this view.
[0066] Additionally, Liquid injectors 366a and 366b aimed at side
looking camera element 256a and 256b respectively are used for
injecting fluid to wash contaminants such as blood, feces and other
debris from front camera element 256 of side looking cameras.
[0067] FIG. 1c schematically depicts a side view of endoscope 200
having multiple fields of view according to an exemplary embodiment
of the current invention.
[0068] FIG. 1c shows front camera element 256 of side looking
camera 220, groove 370 and optical window 252 on the side wall 362
of head 230. Liquid injectors 346 and 366 are also visible in this
view.
[0069] FIG. 2a schematically depicts a cutout isometric view of an
endoscope 400 having multiple fields of view according to another
exemplary embodiment of the current invention.
[0070] According to an exemplary embodiment of the current
invention, head 230 of endoscope 200 comprises at least a forwards
looking camera 116 and two side looking cameras 220a and 220b.
[0071] Optical windows 242a and 242b of LEDs used for forward
illumination are also seen on front face of head 230.
[0072] Distal opening 340 of working channel is preferably located
on front face of head 230 such that a surgical tool inserted
through the working channel 262 and deployed beyond front face may
be viewed by forwards looking camera 116.
[0073] Distal opening 344 of a fluid channel is preferably also
located on front face of head 230. The fluid channel leading to
distal opening 344 may be used as a jet channel for cleaning the
colon.
[0074] Liquid injector 346 having a nozzle aimed at front camera
element of camera 116 is used for injecting fluid to wash
contaminants such as blood, feces and other debris from front
camera element of forwards looking camera 116. Optionally the same
injector is used for cleaning the front camera element and one or
both optical windows 242a and 242b. Injector 346 may receive fluid
from the fluid channel or may be fed by a dedicated cleaning fluid
channel.
[0075] Visible on right hand side of head 230 is the front camera
element 256b of side looking camera 220b and optical window 252b of
side illuminating LED.
[0076] Liquid injector 366b having a nozzle aimed at front camera
element 256b is used for injecting fluid to wash contaminants such
as blood, feces and other debris from front camera element 256b of
side looking camera 220b. Optionally the same injector is used for
cleaning both front camera element 256b and optical windows 252b.
An optional groove 370b helps directing the cleaning jet from
injector 366b towards front camera element 256b.
[0077] Although not seen in this figure, it is understood that
equivalent elements 366a, 370a, 256a and 252a are present on the
left hand side of head 230.
[0078] Preferably, all the injectors 346 and 366 are fed from same
channel.
[0079] In the depicted embodiment, flexible shaft 260 is
constructed of a plurality of links 382 (only one is marked for
clarity). Electrical cable 396 within shaft 260 is seen connected
to cameras 116, 220a and 220b. The same or separate electrical
cable is used to power the LEDs.
[0080] FIG. 2b schematically depicts a cross section of an
endoscope 200 having multiple fields of view showing some details
of the head 230 according to an exemplary embodiment of the current
invention.
[0081] According to the current invention, head 230 of endoscope
200 comprises at least a forwards looking camera 116 and two side
looking cameras 220a and 220b. Each of cameras 116 and 220 is
provided with an optical imaging system such as lens assemblies
(systems) 132 and 232 respectively and solid state detector arrays
134 and 234 respectively. Front camera elements 236 and 256 of
cameras 116 and 220 respectively may be a flat protective window,
but optionally an optical element used as part of the imaging
systems such as solid state detector arrays 134 and 234
respectively. Optionally, cameras 116 and 220 are similar or
identical, however different camera designs may be used, for
example, field of views 118 and 218 may be different. Additionally
or alternatively, other camera parameters such as: resolution,
light sensitivity, pixel size and pixel number, focal length, focal
distance and depth of field may be selected to be same or
different.
[0082] Light is provided by Light Emitting Diodes (LED) that
illuminates the field of views. According to some embodiments,
white light LEDs may be used. According to other embodiments, other
colors of LEDs or any combination of LEDs may be used (for example,
red, green, blue, infrared, ultraviolet).
[0083] In the depicted embodiment, field of view 118 of forwards
looking camera 116 is illuminated by two LEDs 240a and 240b located
within the endoscope head 230 and protected by optical window 242a
and 242b respectively.
[0084] Similarly, in the depicted embodiment, field of views of
side looking camera 220 is illuminated by a single LED 250 located
within the endoscope head 230 and protected by optical window 252.
It should be noted that number of LED light sources and their
position in respect to the cameras may vary within the scope of the
current invention. For example few LEDs may be positioned behind
the same protective window, a camera and an LED or plurality of LED
may be located behind the same protective window, etc.
[0085] Head 230 of endoscope 200 is located at the distal end of a
flexible shaft 260. Similarly to shafts of the art, shaft 260
comprises a working channel 262 for insertion of surgical tools.
Additionally, shaft 260 may comprises channels for irrigation,
insufflation, suction and supplying liquid for washing the colon
wall.
[0086] FIG. 2c schematically depicts a cross section cutout of an
endoscope 200 showing some details of the head 230 according to an
exemplary embodiment of the current invention. For simplicity,
details of one of the two side looking cameras are marked in the
figure.
[0087] According to the current invention, head 230 of endoscope
200 comprises at least one side looking camera 220. Each of cameras
220 is provided with an optical imaging system such as lens
assemblies 232 and solid state detector arrays 234. Front camera
element 256 of camera 220 may be a flat protective window or an
optical element used as part of the imaging system 232.
[0088] FIG. 2d schematically depicts a cross section of an
endoscope 200 having multiple fields of view showing some details
of the head 230 according to an exemplary embodiment of the current
invention.
[0089] According to some embodiments of the current invention, the
interior of the head 230 comprises forward looking and side looking
cameras 116 and 220, respectively. Cameras 116 and/or 220 comprise
lens assemblies 132 and 232 (not shown), respectively, having a
plurality of lenses 430 to 434 and protective glass 436 (not shown)
and a solid state detector arrays 134 and 234 (not shown) connected
to a printed circuit board 135 and 235 (not shown) respectively. It
is noted that cameras 116 and 220 or any element related to them
(such as lens assemblies 132 and 232, lenses 430 to 434 and
protective glass 436, solid state detector arrays 134 and 234
and/or printed circuit board 135 and 235) may be the same or
different. In other words the front looking camera and the side
looking camera(s) may be the same or different in any one or any
combinations of their components or other element related to them
(such as optical elements).
[0090] FIG. 3 schematically depicts a cross section of cameras 116
or 220, showing some details of lens assemblies 132 and 232
according to an exemplary embodiment of the current invention. It
should be noted that according to some embodiments of the
invention, cameras 116 and 220 may be similar or different.
Optionally, the focusing distance of camera 116 is slightly
different than that of camera 220. Differences in focusing
distances may be achieved, for example, by (slightly) changing the
distance between the lenses that comprise the lens assemblies 132
and/or 232, or between the lens assembly and the detector
array.
[0091] Air gap "S" between lenses 431 and 432 acts as a stop. Air
gap S may affect the focal range (the distance between the closest
object and farther objects that can be imaged without excessive
blurring caused by being out of optimal focusing of the lens
system).
[0092] According to an exemplary embodiment of the current
invention, cameras 116 and 220 comprise lens assemblies 132 and 232
respectively. The lens assemblies comprise a set of lenses 430 to
434 and protective glass 436.
[0093] Lenses 430 to 434 are situated within a (optionally
metallic) barrel 410 and connecter thereto (for example, glued in
barrel 410). Any one of lens assemblies 132 and/or 232 may also
include an adapter 411, optionally, as shown in FIG. 3, positioned
within barrel 410. Adapter 411 is configured to adjust the location
of one or more of the lenses and adjust the distance between
lenses. Adapter 411 may also be configured to function as a stop
(in this case, between lenses 432 and 433. Protective glass 436 is
situated in proximity to the solid state detector arrays 134 or 234
and is optionally attached thereto.
[0094] Focal distance (the distance to the object to be optimally
focused by the lens system) may be changed by changing the distance
between lenses 434 and protective glass 436. As lens 434 is fixed
to the barrel, and protective glass 436 is fixed to lens holder 136
(236), this distance may be varied by changing the relative
positioning of lens holder 136 (236) with respect to barrel 410.
The space between the lenses 434 and protective glass 436 may be an
empty space or may be filled with glass or other transparent
material, or a tubular spacer may be inserted to guarantee the
correct distance between these lenses. Optionally, optical filters
may be placed within the space. Cameras 116 and 220 further
comprise solid state detector arrays 134 and 234 respectively.
Solid state detector arrays 134 and 234 may each be connected to
printed circuit boards. An electrical cabling may connect the
printed boards to a central control system unit of the
endoscope.
[0095] Solid state detector arrays 134 and 234 are attached to lens
holders 136 and 236 respectively. Lens holder 136 or 236 are
attached to lens assemblies 132 or 232 respectively by attaching
detector array cover to barrel 410.
[0096] In some applications, protective glass 436 may be a
flat-flat optical element, acting primarily as a protection of the
detector array (such as detector arrays 134 and 234), and may
optionally be supplied with the array. However, optical properties
of protective glass 436 need to be accounted for in the optical
design.
[0097] In order to assemble lens assemblies 132 or 232, lens 430
may first be inserted from left, then 431, and 432 from right.
Lenses 433 and 434 which may be glued together (or separated for
example by air) are then inserted from right. The complete set is
now assembled in a barrel. The assembled detector (such as detector
arrays 134 and 234), protective glass 436 and cover 136(236) are
then added.
[0098] FIGS. 4a, 4b and 4c illustrate three examples for the lens
assemblies such as lens assemblies 132 and 232 according to the
present invention, having objective lens systems 510, 520 and 530
respectively. The sensor used in the lens assemblies 132 and 232,
according to this exemplary embodiment, may be a Charge Coupled
Device sensor (CCD) having an array of micro-lenses but other
sensors, such as CMOS, may also be used.
[0099] In an exemplary embodiment of the invention, a color CCD
camera having resolution of approximately 800.times.600 pixels were
used with total active area of approximately 3.3.times.2.95 mm. The
optical resolution of the lens, according to exemplary embodiments
of the current invention, was designed to match the resolution of
the sensor. The objective lens system 510 (520/530) are preferably
corrected for chromatic; spherical and astigmatism aberrations. In
an exemplary embodiment of the invention, objective lens system 510
(520/530) is approximately 4.60 mm (4.62) total length, measured
from front face of front lens to the front surface of the sensor.
In an exemplary embodiment of the invention, objective lens systems
510 and 520 are wide angle objectives having approximately 170
degrees acceptance angle. In an exemplary embodiment of the
invention, objective lens system 510 (520/530) has a short focal
distance of measured from the front surface of the front lens to
the imaged object. In an exemplary embodiment of the invention
objective lens system 510 (520/530) has Depth of Focus (DOF)
allowing to effectively image objects between 4-110 mm (or between,
3.5-50 mm). In an exemplary embodiment of the invention, objective
lens system 510, 520 and 530 has maximum diameter of about 2.5 mm,
defined by the diameter of the front lens, and is housed in a
barrel having maximum outer diameter of approximately 3.6 mm. It
should be noted that other design parameters may be selected within
the general scope of the current invention.
[0100] The objective lens system 510 (520/530) has an optical axis
"O" depicted by the dashed line. The lens system comprises a front
sub-system 510a (520a/530a) and a rear sub-system 510b
(520b/530b).
[0101] Front sub-system 510a (520a) (FIGS. 4a (4b)) comprises a
front lens 430 (430') located closest to the object to be viewed,
having a negative power and lens 431(431') having a positive
power.
[0102] Front lens 430 (430') is oriented with its concave surface
facing the object to be viewed and optionally having a diameter
substantially greater than the largest dimension of the rear
sub-system 510b in the direction perpendicular to the optical axis.
Lens 431(431') has a positive power.
[0103] Rear sub-system 510b (520b) comprises lenses 432, 433; 434;
and protective glass 436 (lenses 432; 433; 434; and 436'), wherein
432 (432'), has a negative power, 433 (433') has a positive power,
434 (434') has a negative power, and 436 (436') has essentially no
optic power. It is noted that protective glass 436 (436') may be a
part of the sensor or a part of the rear sub-system 510b (520b).
Lenses 433 and 434 (433' and 434') of the rear sub-system 510b
(520b) compose an achromatic sub-assembly (a compound achromatic
sub-assembly as seen in FIG. 4a, where lenses 433 and 434 are
cemented or non-compound achromatic sub-assembly as seen in FIG.
4b, where lens 433' and lens 434' are separated). Lens 433 (433')
may be biconvex with radius of curvature of its front surface being
smaller than radius of curvature of its rear surface, as indicated
in Tables T.sub.1,T.sub.2 below.
[0104] Lens 432 of the objective lens systems 510 may have a focal
length f.sub.432 satisfying the following condition:
f.sub.432.ltoreq.1.8f, where f is the composite focal length of the
total system. Particularly, for the data indicated in Table T.sub.1
f.sub.432=2.05 and f=1.234 mm, the condition: f.sub.432.ltoreq.1.8f
is satisfied.
[0105] Lens 432' of the objective lens systems 520 may have a focal
length f.sub.432' satisfying the following condition:
f.sub.432.ltoreq.1.8f.
[0106] Particularly, for the data indicated in Table T.sub.2
f.sub.432=2.05 and f=1.15 mm, the condition: f.sub.432.ltoreq.1.8f
is satisfied.
[0107] The lenses may be coated with an anti-reflection coating (AR
coating) for further improving the efficiency of the lens
assemblies 132 (232).
[0108] An effective aperture stop S.sub.1 (S.sub.2) is formed
between lenses 431 and 432 (431' and 432'). Effective aperture stop
S.sub.1 (S.sub.2) may separate between front sub-system 510a (520a)
and rear sub-system 510b (520b).
[0109] Front sub-system 530a (FIG. 4c) comprises a front lens 430''
located closest to the object to be viewed, having a negative power
and lens 431'', having a positive power. Front sub-system 530a
(FIG. 4c) further comprises an additional front positive lens (such
as the meniscus lens 429) disposed between the first front negative
lens 430'' and the second front positive lens 431''.
[0110] Front lens 430'' is oriented with its concave surface facing
the object to be viewed and optionally having a diameter
substantially greater than the largest dimension of the rear
sub-system 530b in the direction perpendicular to the optical
axis.
[0111] Rear sub-system 530b comprises lenses 432'', 433'', 434'';
and protective glass 436'', wherein 432'', has a negative power,
433'' has a positive power, 434'' has a negative power, and 436''
has essentially no optic power. It is noted that protective glass
436'' may be a part of the sensor or a part of the rear sub-system
530b. Lenses 433'' and 434'' compose an achromatic sub-assembly of
the rear sub-system 530b and may or may not be cemented to each
other. Lens 433'' may be biconvex with radius of curvature of its
front surface being smaller than radius of curvature of its rear
surface, as indicated in Table T.sub.3 below.
[0112] Lens 432'' of the objective lens systems 530 may have a
focal length f.sub.432 satisfying the following condition:
f.sub.432''.ltoreq.1.8f, where f is the composite focal length of
the total system. Particularly, for the data indicated in Table
T.sub.3 f.sub.432''=2.26 and f=1.06 mm, the condition:
f.sub.432''.ltoreq.1.8f is satisfied.
[0113] The lenses may be coated with an anti-reflection coating (AR
coating) for further improving the efficiency of the lens
assemblies 132 (232).
[0114] An effective aperture stop S.sub.3 is formed between lenses
431'' and 432''. Effective aperture stop S.sub.3 may separate
between front sub-system 530a and rear sub-system 530b.
[0115] Tables T.sub.1 T.sub.2 and T.sub.3 summarize the parameters
of lenses in the objective lens systems 510, 520 and 530,
respectively, according to some embodiments of the current
invention:
TABLE-US-00001 TABLE T.sub.1 (FOV = 164.degree., DOF = 3-110 mm. f
= 1.234 mm, total optical track 4.09 mm) Semi-Diameter
Semi-Diameter Lens Type R.sub.1 R.sub.2 Th D Glass d.sub.1/2
d.sub.2/2 f.sub.mm 430 Negative 15 0.7 0.2 0.18 N-LASF3 1.2 0.64
-0.837 431 Plan-convex 0.9 Infinity 0.56 0.27 N-LASF3 0.8 0.8 1.02
S.sub.1 Stop 0.05 0.104 432 Plan-convex Infinity -1.0 0.75 0.09 FK5
0.8 0.8 2.05 433 Biconvex 1.93 -4.2 0.75 0.005 N-LAK22 1.1 1.1 2.13
434 Biconcave -4.2 4.44 0.3 0.65 N-SF66 1.1 1.2 -2.3 436 Protection
Glass Infinity Infinity 0.3 0 N-BK7 1.5 1.5 Infinity
TABLE-US-00002 TABLE T.sub.2 (FOV = 164.degree., DOF = 3-110 mm, f
= 1.15 mm, total optical track 4.09 mm) Semi-Diameter Semi-Diameter
Lens Type R.sub.1 R.sub.2 Th D Glass d.sub.1/2 d.sub.2/2 f.sub.mm
430 Negative 6 0.7 0.2 0.3 N-LASF3 1.2 0.66 -0.913 431 Plan-convex
1.26 Infinity 0.50 0.27 N-LASF3 0.8 0.8 1.43 S.sub.1 Stop 0.05
0.105 432 Plan-convex Infinity -1.0 0.60 0.15 FK5 0.8 0.8 2.05 433
Biconvex 1.67 -1.65 0.70 0.30 FK5 0.95 0.95 1.83 434 Meniscus -1.33
-12.0 0.35 0.40 N-SF66 1.0 1.2 -1.65 436 Protection Glass Infinity
Infinity 0.3 0 N-BK7 1.5 1.5 Infiniy
[0116] Table 3, shows an example of a six-component system also
comprising an additional positive lens 429 (for example, as
indicated in Table 3, a meniscus lens).
TABLE-US-00003 TABLE T.sub.3 (FOV = 164.degree., DOF = 3-110 mm, f
= 1.06 mm, total optical track 4.69 mm) Semi-Diameter Semi-Diameter
Lens Type R.sub.1 R.sub.2 Th D Glass d.sub.1/2 d.sub.2/2 f.sub.mm
430'' Negative 4.3 0.75 0.2 0.22 N-LASF3 1.3 0.72 -1.06 429
Meniscus 0.95 0.9 0.44 0.18 N-SF66 0.8 0.65 5.75 431'' Plan-convex
2.0 Infinitiy 0.75 0.02 N-LASF3 0.8 0.8 2.26 S.sub.3 Stop 0.02
0.116 432'' Plan-convex Infinitiy -1.0 0.78 0 N-PSK5 0.8 0.8 1.69
433'' Biconvex 2.52 -2.0 0.50 0.154 YGH52 0.8 0.8 1.49 434''
Biconcav -1.44 11.0 0.25 0.91 PBH56 0.8 0.9 -1.50 436'' Protection
Glass Infinity Infinity 0.3 0 N-BK7 1.5 1.5 Infiniy
R.sub.1--radius of curvature of the lens front surface (front
surface is the surface facing the direction of the object);
R.sub.2--radius of curvature of the lens rear surface (facing away
from the object); Th--thickness of the lens--from center of front
surface to center of rear surface; Glass--lens glass type;
d.sub.1--radius of the front optical surface of the lens;
d.sub.2--radius of the rear optical surface of the lens;
D--distance between components such as lenses, measured front
center of rear surface of the component, such as lens to the front
surface of the next optical element (in the case of a stop, S, the
distance is measured front center of rear surface of a component on
the front side of the stop, to the front surface of the next
component), As commonly used, radius of curvature equal to infinity
is interpreted as planar. All lenses are optionally spherical.
[0117] FIGS. 4a, 4b and 4c also show the propagation of five
incident rays of light R.sub.1 to R.sub.6 through the objective
lens system 510, 520 and 530 respectively, from the front lens 430
(FIG. 4a), 430' (FIG. 4b) or 430'' (FIG. 4c) till the creating of
an image of the object at an image plane.
[0118] Rays R.sub.1 to R.sub.6, enter the lens assembly at angles
.alpha..sub.1 (alpha 1) to .alpha..sub.6 (alpha 6), respectively,
for example, essentially equal to the following angles:
.alpha..sub.1=0.degree., .alpha..sub.2=45.degree.,
.alpha..sub.3=60.degree., .alpha..sub.4=75.degree. and
.alpha..sub.5=84.degree.. The corresponding incident angles (the
angles between the light rays which have passed the micro-lenses of
the sensor and the optical axis of the system) are
.quadrature..sub.1 (beta 1)-.quadrature..sub.6 (beta 6). According
to some embodiments, the chief incident angle (for example the
incident angles forming by rays R.sub.6 in FIGS. 4a-4c) is larger
than 20.degree., larger than 25.degree., larger than 30.degree. or
between about 20-40.degree.. The lens system, according to some
embodiments of the invention provides minimal distortion (for
example, less than 80%).
[0119] The optical system assembly 132 (232) may be assembled by a
method comprising the step of:
[0120] Optionally, cementing the rear doublet of lenses 433-434
(433'-434');
[0121] and:
[0122] Assembling in the barrel the front lenses 430 (430');
[0123] Assembling lens 431 (431') in the barrel;
[0124] Assembling lens 432 (432') in the barrel;
[0125] Assembling in the barrel, the rear doublet 433-434
(433'-434'); and
[0126] Note that front lens 430 (430') may be assembled last.
[0127] Although the invention has been described in conjunction
with specific embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, it is intended to embrace
all such alternatives, modifications and variations that fall
within the spirit and broad scope of the appended claims. All
publications, patents and patent applications mentioned in this
specification are herein incorporated in their entirety by
reference into the specification, to the same extent as if each
individual publication, patent or patent application was
specifically and individually indicated to be incorporated herein
by reference. In addition, citation or identification of any
reference in this application shall not be construed as an
admission that such reference is available as prior art to the
present invention.
* * * * *