Polarimetric endoscope

Abstract

A polarimetric endoscope includes an insertion tube and a polarization imaging channel. The polarization imaging channel includes (i) an imaging fiber bundle having a plurality of optical fibers and being at least partially in the insertion tube, (ii) an imaging lens at a distal tube-end, of the insertion tube, that forms an image at a distal bundle-end of the imaging fiber bundle, and (iii) a polarizer array having a plurality of polarizers each aligned to a distal end of a respective one of the plurality of optical fibers and transmitting one of a plurality of polarization states. Each of the imaging fiber bundle and the first and second illumination channels is at least partially in the insertion tube.

Description

PATENTAttorney Docket No: UOAZ.P2142PCT / 00608558POLARIMETRIC ENDOSCOPECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No.63 / 466,067, filed on 12 May 2023, the disclosure of which is incorporated herein byreference in its entirety.GOVERNMENT RIGHTS

[0002] This invention was made with government support under Grant No.W81XWH-22-1-0211 awarded by ARMY / MRDC. The government has certain rights in theinvention.BACKGROUND

[0003] Esophagogastroduodenoscopy (EGD) offers an unparalleled view of theluminal wall of major gastrointestinal organs afflicted by high incidence and mortality fromcancer and is the only tool that allows for simultaneous visualization, biopsy, and mucosalor submucosal resection. Current endoscopes are primarily limited to the use white lightimaging (WLI) and narrow-band imaging. White light imaging (WLI) yields contrast viaabsorption and reflection of broadband illumination aggregated in three red, green, andblue (RGB) imaging filters. Narrow-band imaging yields vasculature contrast via narrowband illumination at hemoglobin absorption peaks of 415 nm and 540 nm. Incidence andmortality, early diagnosis miss rates, biopsy sampling error / quantity, and burdens onhistopathology, indicate a significant need for improved imaging tools that can: detect andlocalize early, otherwise unseen lesions; be incorporated into endoscopy for screening andevaluation of early symptoms; and provide biopsy guidance.SUMMARY OF THE EMBODIMENTS

[0004] In a first aspect, a polarimetric endoscope includes an insertion tube and apolarization imaging channel. The polarization imaging channel includes (i) an imagingfiber bundle having a plurality of optical fibers and being at least partially in the insertiontube, (ii) an imaging lens at a distal tube-end, of the insertion tube, that forms an image at adistal bundle-end of the imaging fiber bundle, and (iii) a polarizer array having a plurality1 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558of polarizers each aligned to a distal end of a respective one of the plurality of optical fibersand transmitting one of a plurality of polarization states. Each of the imaging fiber bundleand the first and second illumination channels is at least partially in the insertion tube.BRIEF DESCRIPTION OF THE FIGURES

[0005] FIG. 1 shows preliminary imaging data averaged over a region of interest(ROI) exhibiting a decrease in the degree of linear polarization (DOLP) in cancerous tissuebiopsies.

[0006] FIG. 2 demonstrates data collected by a hyperspectral imaging systemaveraged over a region of interest.

[0007] FIGs. 3, 4, and 5 are respective schematics of a polarimetric endoscope, in anembodiment.

[0008] FIG. 6 is a schematic of an imaging fiber bundle and micropolarizer array(MPA), which are examples of an imaging fiber bundle and MPA of the polarimetricendoscope of FIGs 3–5.

[0009] FIG. 7 is a schematic of a polarimetric endoscope, which is an example of thepolarimetric endoscope of FIGs 3–5.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] In recent years, numerous label-free imaging-based techniques haveemerged that are candidates for optical detection of neoplasia. Among these are spectraland polarimetric imaging, which involve different light-tissue interactions. Probingmultiple light-tissue interactions, known as multimodal imaging, integrates complimentarysources of biological contrast to the scene due to the quasi-mutual exclusivity of eachinteraction. Spectral imaging can capture wavelength encoded light-tissue interactionsfrom chromophores, tissue microstructure, higher nuclei density, or collagen matrixtransformations. Polarimetric imaging reveals tissue scattering and absorption informationand provides insight into directional mechanical properties of tissue to monitorpathological changes in collagen and elastin.

[0011] Current approaches to flexible polarimetric endoscopy have significantsystem design or performance drawbacks. For example, using a single fiber scanning2 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558approach necessitates real time-feedback of the fiber’s transmission matrix properties, andrequires a high brightness source like a laser, which could introduce speckle and ultimatelyresult in insensitivity to tissue depolarization properties. Additional complexities arise inminiaturization of actuation components. Advances in flexible polarimetric endoscopycould significantly improve EGD in identifying neoplastic lesions and guidance of biopsies,and perhaps could eventually serve as an optical biopsy tool.

[0012] Polarimetric imaging reveals tissue scattering and absorption informationand provides insight into directional mechanical properties of tissue to monitorpathological changes in collagen and elastin. Early tumor development causes collagenreorganization and disruption to the extracellular matrix; thus, polarization imagingprovides information about the microstructural changes of early cancer. In parallel,spectral imaging and polarimetric imaging can highlight pathological features ranging frommicro- and macro- architecture of vasculature and collagen reorganization providing amultimodal set rich with measures that can distinguish normal from neoplastic lesions.

[0013] Embodiments of endoscopes disclosed herein measure spatially resolvedpartial polarimetric information of light-tissue interactions with a flexible endoscope. A keyfeature of certain embodiments is a micro-polarizer array (MPA) between the imaging fiberbundle and an imaging lens. This is an important step forward in flexible endoscopybecause imaging fiber bundles scramble polarization information. By contrast, the MPAcaptures the state of polarization prior to entering the imaging fiber bundle. The approachcould be widely translatable to other miniaturized polarimetric imaging systems (e.g.,laparoscopy, non-GI endoscopy) and has potential to dramatically reduce complexity andcost of polarimetric imaging enabling use in low cost / resource settings. Endoscopesdisclosed herein address a significant need for improved imaging tools to localize earlyneoplastic tissue.Overview^of^a^multi‐modal^endoscope

[0014] The imaging requirements of the endoscope may be based on commercialdiagnostic endoscopes for EGDs. The polarimetric and spectral imaging channels may beforward viewing, have a field of view of approximately 120 degrees, and a depth of fieldbetween 2 mm and 100 mm. To enable polarimetric measurements, a micro-array3 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558polarizer (MPA) may be bonded to the imaging fiber bundle at the distal tip. Illumination atthe peripheral circumference of the distal tip provides six polarization illumination states.To enable spectral imaging, a similar approach to narrow-band imaging may be used toprovide narrow band illumination at multiple wavelengths with a 300-W xenon arc lampsource.

[0015] In embodiments, the polarization imaging channel includes an MPA bondedonto the fiber bundle face of the distal tip. Multiple illumination fibers (e.g., six) may bedelivered to the outer edges of the distal end of the endoscope for a complete achromaticgenerator of polarized illumination. In embodiments, the ^^# of the imaging optics ismatched to that of the etendue of the imaging fiber bundle.

[0016] Pursuit of integrating polarimetric imaging into flexible endoscopy is in partmotivated by our preliminary data. Benchtop ex-vivo imaging systems in our lab have beenused to capture the hyperspectral (470 – 900 nm), autofluorescence (5 excitation, 7emission channels), polarimetric (5 wavelength, reflectance, full Mueller matrix), andoptical coherence tomography (1300-nm central wavelength) datasets of 13 matchedpatient jumbo forceps biopsies from the esophagus of normal adjacent and tissue withadenocarcinoma, squamous cell carcinoma, and / or Barrett’s esophagus.

[0017] FIG. 1 shows imaging data averaged over a region of interest (ROI) exhibitinga decrease in the degree of linear polarization (DOLP) in cancerous tissue biopsies acrossvarious illumination wavelengths. FIG. 1 shows ROI average DOLP at five wavelengths fortwo patients with matched esophageal biopsies of adjacent normal tissue and tumor tissue.

[0018] DOLP only requires the first three elements of the first column of the 4×4Mueller matrix. We have also observed diattenuation, calculated from the first row of the4×4 Mueller matrix, to provide contrast between normal adjacent and tumor tissues acrossall wavelengths – with a pronounced improvement in the 543-nm and 632-nmwavelengths. The full Mueller matrix is critical for ex-vivo benchtop studies to validatesystem design decisions, however, in endoscopy it is critical to reduce system complexity.

[0019] FIG. 2 demonstrates data collected by the hyperspectral imaging systemaveraged over an ROI that has been normalized by the maximum at the 770-nmwavelength. In FIG. 2, ROI normalized average hyperspectral signature of matched4 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558esophageal biopsies of adjacent normal and tumor tissue with the difference squared of theunnormalized data.

[0020] Further insight is drawn from the difference square of the unnormalizedspectrographs between adjacent normal and tumor tissue. Sub-sampling to severalwavelengths that demonstrate a large and negligible difference in the spectrographs arecritical to creating abundance maps that heatmap suspected neoplasms. Therefore, thespectral imaging channel may sub-select imaging at 405 nm, 543 nm, and 632 nm, whichshares polarimetric illumination wavelengths.Embodiment^of^a^polarimetric^endoscope^

[0021] FIG. 3 is a schematic cross-sectional view of a polarimetric endoscope 300.FIG. 4 is a schematic plan view of a distal end 309 of polarimetric endoscope 300. FIG. 5 is aschematic of polarimetric endoscope 300 illustrating optical components thereof. FIGs. 3–5are best viewed together in the following description.

[0022] Polarimetric endoscope 300 includes an insertion tube 310 and apolarization imaging channel 320. Polarimetric endoscope 300 may also include at leastone illumination channel 330, such as illumination channels 330(1) and 330(2) shown inFIG. 3. Insertion tube 310 has a proximal tube-end 311 and a distal tube-end 319. As shownin FIG. 5, polarimetric endoscope 300 may also include a working channel 502 and one ormore additional channels 504, such as an air channel and a water channel. Insertion tube310 may be more flexible at distal tube-end 319 than at proximal tube-end 311

[0023] Polarization imaging channel 320 includes (i) an imaging fiber bundle 322having a plurality of optical fibers 324, (ii) an imaging lens 327 at distal tube-end 319 thatforms an image at a distal bundle-end 323 of imaging fiber bundle 322, and (iii) a polarizerarray 360. Imaging fiber bundle 322 and imaging fiber bundle 342 have respective distalbundle-ends 325 and 345.

[0024] Polarizer array 360 has a plurality of polarizers 364 each aligned to a distalend of a respective one of the plurality of optical fibers 324. At distal bundle-end 323 theoptical axis of imaging lens 327 may be coaxial with or parallel to an optical axis of imagingfiber bundle 322. In embodiments, at least one of distal bundle-end 323 and polarizer array5 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558360 is within a depth of field of imaging lens 327. Polarizer array 360 may be betweenimaging lens 327 and distal bundle-end 323.

[0025] Each polarizer 364 transmits one of a plurality of polarization states ofconverging light incident thereon propagating from lens 327. Examples of the polarizationstates include linear polarizations and circular polarizations, as shown in FIG. 5. Thepolarization states shown in FIG. 5 are examples of the plurality of polarization statestransmitted by a polarizer 364. The plurality of polarization states may differ from thoseshown in FIG. 5 without departing from the scope hereof.

[0026] Each of the imaging fiber bundle 322 and illumination channels 330 is atleast partially in insertion tube 310. At least part of imaging lens 327 and at least part ofpolarizer array 360 may be within insertion tube 310.

[0027] Illumination channel 330(1) emits, from distal tube-end 319, a firstillumination having a first polarization state of the plurality of polarization states.Illumination channel 330(2) emits, from distal tube-end 319, a second illumination havinga second polarization state of the plurality of polarization states. The first and the secondpolarization states may be orthogonal. Polarimetric endoscope 300 may include additionalillumination channels 330( ^^), where index ^^ greater than equal to three. The plurality ofpolarization states may include multiple pairs of orthogonal polarization states. Inembodiments, a single illumination channel 330 may emit the first polarization stateduring a first time period and emit the second polarization state during a second timeperiod that follows the first time period. In embodiments, one or more illuminationchannels 330 may emit illumination that is either unpolarized, partially polarized, orincludes multiple polarizations.

[0028] Each illumination channel 330( ^^) may emit a respective one of ^^ polarizationstates of the plurality of polarization states. Illumination channel 330 has a distal end 339.In embodiments, each illumination channel 330( ^^) has a respective polarizer 336( ^^) at itsdistal end 339( ^^). For example illumination channels 330(1) and 330(2) may have arespective polarizer 336(1) and 336(2) at their respective distal ends 339. Polarimetricendoscope 300 may include multiple illumination channels 330 that emit the samepolarization state.6 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558

[0029] At distal tube-end 319, respective locations of illumination channels 330 maydefine vertices of a polygon surrounding imaging lens 327. For example, in FIG. 4 thepolygon is a hexagon.

[0030] In embodiments, each polarizer 364 of polarizer array 360 may transmit oneof the plurality of polarization states. In embodiments, at least one of (i) polarizer array360 is bonded to distal bundle-end 323 and (ii) polarizer array 360 is a pixelatedmicropolarizer array. For each of the plurality of polarization states, polarizer array 360may include at least one polarizer 364 that transmits the polarization state. Polarizer array360 may include, for each of the ^^ polarization states, multiple polarizers 364 that transmitthe ^^^୦ polarization state.

[0031] Polarimetric endoscope 300 may include a spectral imaging channel 340.Spectral imaging channel 340 includes an imaging fiber bundle 342 at least partly ininsertion tube 310. Imaging fiber bundle 342 includes an additional plurality of opticalfibers. Imaging channel 340 also includes an imaging lens 347 at distal tube-end 319. Atleast part of imaging lens 347 may be within insertion tube 310.

[0032] Imaging lens 347 forms an image at a distal bundle-end 343 of imaging fiberbundle 342. Respective fields of view of imaging lenses 327 and 347 overlap, such thatimaging lenses 327 and 347 capture an image of a scene defined by this overlap, andpolarimetric endoscope 300 captures both a polarimetric image and a spectral image of thescene.

[0033] In embodiments, MPA 360 is attached to the distal end of imaging fiberbundle 322. This enables a partial polarization analyzer that samples light after itsinteraction with tissue prior to being scrambled by the imaging fiber bundle.

[0034] Polarimetric endoscope 300 may include a plurality of light sources 370 (FIG.3) each coupled to a respective illumination channel 330. At least one of light sources 370may be a polarized light source, in which case the illumination channel 330 coupled theretomay include one or more polarization-maintaining optical fibers.

[0035] Polarimetric endoscope 300 may include one or more sensors 372, whichmay be high-speed, back-illuminated sensors. For example, distal bundle-end 325 anddistal bundle-end 345 of respective imaging fiber bundles 322 and 342 may be directlybonded to respective sensors 372(1) and 372(2).7 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558

[0036] FIG. 6 is a schematic of an imaging fiber bundle 622, with an MPA 660 on itsdistal end. Fiber bundle 622 and MPA 660 are respective examples of imaging fiber bundle322 and MPA 360. Imaging fiber bundle 622 may have a square lattice configuration, asshown in FIG. 6, or a hexagonal lattice configuration. The pitch may equal ten micrometers,for example. The distal end of the flexible imaging fiber bundle may be bonded to MPA 660.

[0037] MPA 660 includes a plurality of micropolarizers 664. MPA 660 may includean array of super pixels 662, each of which includes an array of micropolarizers 664. In theexample of MPA 660, each super pixel 662 is a 2×2 array of micropolarizers 664 thattransmit a different polarization state, e.g., different linear and / or circular polarizations.Each micropolarizer 664 is an example of polarizer 364.

[0038] The diameter of MPA 360 may be between 3.5 mm and 4 mm. Thisconfiguration provides a resolution of approximately 50-line pairs per mm (lp / mm) inimage space. In embodiments, MPA 360 is aligned to distal bundle-end 323 of imaging fiberbundle 322 with a microscope and micro positioning stages and bonded with a UVactivated adhesive.

[0039] FIG. 7 is a schematic of an endoscope 700 coupled to one or more outputdevices 790. Output devices 790 may include at least one of computer, a mobile device, andan augmented reality headset. Endoscope 700 is an example of endoscope 300. Endoscope700 includes polarization imaging channel 720, illumination channels 730, spectralimaging channel 740, and a light source 770, which are examples of polarization imagingchannel 320, illumination channels 730, spectral imaging channel 340, and light sources370, respectively. Channels 720 and 740 includes respective imaging fiber bundle 322 and342. Light source 770 includes multiple LEDs, which in this example emit light at 632 nm,543 nm, and 405 nm.Generating^a^stereoscopic^3D^model^from^the^imaging^channels

[0040] In embodiments, a model generation method includes generating, with animage processing algorithm, a 3D object model of lesion topography from the imagescaptured by polarimetric endoscope 300. A subsequent step includes, using markings alongthe length of the endoscope tubing, assigning displacement between captured images,which enables an absolute measurement scale to be applied to the 3D model. This8 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558technique provides height information of the organ traversed by the endoscope, therebyhighlighting irregularities in small bumps or divots that would otherwise go unseen bystandard imaging.A^method^for^rendering^a^still^AR^scene^from^stereo^data^from^the^endoscope

[0041] In embodiments, polarization imaging channel 320 and spectral imagingchannel 340 endoscope 300 act as two pupils similar to the vision system of a human. Themethod includes porting images from spectral channel 340 to one eye and porting imagesfrom polarimetric channel 320 to the other eye to form a 3D scene. This method does notrequire heavy computational processing associated with 3D modeling from stereoscopicimages. The method may include adjusting the respective images corresponding to onescene to have similar mean gray values across the different illumination wavelengths. Themethod may also include loading, into an output device 790, such as an AR display, theimages captured by each imaging channel and displaying the images to the left and righteye of the user.Combinations^of^Features^

[0042] Features described above, as well as those claimed below, may be combinedin various ways without departing from the scope hereof. The following enumeratedexamples illustrate some possible, non-limiting combinations.

[0043] Embodiment 1. A polarimetric endoscope comprising: an insertion tube havinga proximal tube-end and a distal tube-end; a polarization imaging channel including (i) animaging fiber bundle having a plurality of optical fibers and being at least partially in theinsertion tube (ii) an imaging lens at the distal tube-end that forms an image at a distalbundle-end of the imaging fiber bundle, and (iii) a polarizer array having a plurality ofpolarizers each aligned to a distal end of a respective one of the plurality of optical fibersand transmitting one of a plurality of polarization states.

[0044] Embodiment 2. The endoscope of embodiment 1, an optical axis of the imaginglens being coaxial with the imaging fiber bundle at the distal bundle-end.9 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558

[0045] Embodiment 3. The endoscope of either one embodiments 1 or 2, at least oneof the distal bundle-end and the polarizer array being within a depth of field of the imaginglens.

[0046] Embodiment 4. The endoscope of any one embodiments 1–3, the polarizerarray being between the imaging lens and the distal bundle-end.

[0047] Embodiment 5. The endoscope of any one embodiments 1–4, furthercomprising: a spectral imaging channel including (i) an additional imaging fiber bundle atleast partly in the insertion tube and including an additional plurality of optical fibers, and(ii) an additional imaging lens at the distal tube-end that forms an additional image at anadditional distal bundle-end of the additional imaging fiber bundle.

[0048] Embodiment 6. The endoscope of any one embodiments 1–5, the polarizerarray being bonded to the distal bundle-end.

[0049] Embodiment 7. The endoscope of any one embodiments 1–6, the polarizerarray being a pixelated micropolarizer array.

[0050] Embodiment 8. The endoscope of any one embodiments 1–7, the plurality ofpolarization states including multiple pairs of orthogonal polarization states.

[0051] Embodiment 9. The endoscope of any one embodiments 1–8, the insertiontube being more flexible at the distal tube-end than at the proximal tube-end.

[0052] Embodiment 10. The endoscope of any one embodiments 1–9, furthercomprising: a first illumination channel, at least partially in the insertion tube, that emits,from the distal tube-end, first illumination having a first polarization state of the pluralityof polarization states.

[0053] Embodiment 11. The endoscope of embodiment 10, the plurality of polarizersincluding multiple polarizers that transmit the first polarization.

[0054] Embodiment 12. The endoscope of either one of embodiments 10 or 11, thefirst illumination channel including a polarization-maintaining fiber.

[0055] Embodiment 13. The endoscope of any one embodiments 10–12, furthercomprising a light source coupled to the first illumination channel.

[0056] Embodiment 14. The endoscope of any one embodiments 10–13, furthercomprising: a second illumination channel, at least partially in the insertion tube, that10 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558emits, from the distal tube-end, second illumination having a second polarization state ofthe plurality of polarization states.

[0057] Embodiment 15. The endoscope of embodiment 14, the second polarizationbeing orthogonal to the first polarization.

[0058] Embodiment 16. The endoscope of either one of embodiments 14 or 15, theplurality of polarizers including multiple polarizers that transmit the second polarization.

[0059] Embodiment 17. The endoscope of any one embodiments 14–16, furthercomprising a plurality of illumination channels that each emit, from the distal tube-end,illumination having one of the plurality of polarization states, the first illumination channeland the second illumination channel each being one of plurality of illumination channels.

[0060] Embodiment 18. The endoscope of embodiment 17, at the distal tube-end,respective locations the plurality of illumination channels defining vertices of a polygonsurrounding the imaging lens.

[0061] Embodiment 19. The endoscope of either one of embodiments 17 or 18, eachof the plurality of illumination channels including one of a plurality of polarizers at a distalend of the illumination channel.

[0062] Embodiment 20. The endoscope of embodiment 19, each of the plurality ofpolarizers transmitting one of the plurality of polarization states.* * *

[0063] Changes may be made in the above methods and systems without departingfrom the scope of the present embodiments. It should thus be noted that the mattercontained in the above description or shown in the accompanying drawings should beinterpreted as illustrative and not in a limiting sense. Herein, and unless otherwiseindicated the phrase “in embodiments” is equivalent to the phrase “in certainembodiments,” and does not refer to all embodiments.

[0064] Regarding instances of the terms “and / or” and “at least one of,” for example, inthe cases of “A and / or B” and “at least one of A and B,” such phrasing encompasses theselection of (i) A only, or (ii) B only, or (iii) both A and B. In the cases of “A, B, and / or C” and“at least one of A, B, and C,” such phrasing encompasses the selection of (i) A only, or (ii) B11 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 00608558only, or (iii) C only, or (iv) A and B only, or (v) A and C only, or (vi) B and C only, or (vii)each of A and B and C. This may be extended for as many items as are listed.

[0065] The following claims are intended to cover all generic and specific featuresdescribed herein, as well as all statements of the scope of the present method and system,which, as a matter of language, might be said to fall therebetween.12 LEGAL\70494295\11

Claims

Attorney Docket No: UOAZ.P2142WO / 00608558CLAIMSWe claim:

1. A polarimetric endoscope comprising:an insertion tube having a proximal tube-end and a distal tube-end;a polarization imaging channel including (i) an imaging fiber bundle having a pluralityof optical fibers and being at least partially in the insertion tube, (ii) an imaginglens at the distal tube-end that forms an image at a distal bundle-end of theimaging fiber bundle, and (iii) a polarizer array having a plurality of polarizerseach aligned to a distal end of a respective one of the plurality of optical fibers andtransmitting one of a plurality of polarization states.

2. The endoscope of claim 1, an optical axis of the imaging lens being coaxial with theimaging fiber bundle at the distal bundle-end.

3. The endoscope of claim 1, at least one of the distal bundle-end and the polarizer arraybeing within a depth of field of the imaging lens.

4. The endoscope of claim 1, the polarizer array being between the imaging lens and thedistal bundle-end.

5. The endoscope of claim 1, further comprising:a spectral imaging channel including (i) an additional imaging fiber bundle at leastpartly in the insertion tube and including an additional plurality of optical fibers,and (ii) an additional imaging lens at the distal tube-end that forms an additionalimage at an additional distal bundle-end of the additional imaging fiber bundle.

6. The endoscope of claim 1, the polarizer array being bonded to the distal bundle-end.

7. The endoscope of claim 1, the polarizer array being a pixelated micropolarizer array.

8. The endoscope of claim 1, the plurality of polarization states including multiple pairs oforthogonal polarization states.13 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 006085589. The endoscope of claim 1, the insertion tube being more flexible at the distal tube-endthan at the proximal tube-end.

10. The endoscope of claim 1, further comprising:a first illumination channel, at least partially in the insertion tube, that emits, from thedistal tube-end, first illumination having a first polarization state of the plurality ofpolarization states.

11. The endoscope of claim 10, the plurality of polarizers including multiple polarizers thattransmit the first polarization.

12. The endoscope of claim 10, the first illumination channel including a polarization-maintaining fiber.

13. The endoscope of claim 10, further comprising a light source coupled to the firstillumination channel.

14. The endoscope of claim 10, further comprising:a second illumination channel, at least partially in the insertion tube, that emits, fromthe distal tube-end, second illumination having a second polarization state of theplurality of polarization states.

15. The endoscope of claim 14, the second polarization being orthogonal to the firstpolarization.

16. The endoscope of claim 14, the plurality of polarizers including multiple polarizers thattransmit the second polarization.

17. The endoscope of claim 14, further comprising a plurality of illumination channels thateach emit, from the distal tube-end, illumination having one of the plurality ofpolarization states, the first illumination channel and the second illumination channeleach being one of plurality of illumination channels.14 LEGAL\70494295\11Attorney Docket No: UOAZ.P2142WO / 0060855818. The endoscope of claim 17, at the distal tube-end, respective locations the plurality ofillumination channels defining vertices of a polygon surrounding the imaging lens.

19. The endoscope of claim 17, each of the plurality of illumination channels including oneof a plurality of polarizers at a distal end of the illumination channel.

20. The endoscope of claim 19, each of the plurality of polarizers transmitting one of theplurality of polarization states.15 LEGAL\70494295\11

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