Patent Description:
Endoscopes in various configurations allow efficient treatment of a range of medical problems, as well as means for manipulating different situations with limited access. Endoscope operations are challenging in that illumination, detection and treatment are confined to long and narrow operations modes. Fiber optics technology is a central enabler for such techniques, and fiber-based endoscope experience continuous improvements.

<CIT> describes endoscopes, multicore endoscope fibers and configuration and operation methods are provided. The fibers may have hundreds or thousands of cores and possibly incorporate working channel(s) and additional fibers. The fiber may be used at different optical configurations to capture images of tissue and objects at the distal tip and to enhance a wide range of optical characteristics of the images such as resolution, field of view, depth of field, wavelength ranges etc..

<CIT> describes an optical device that allows laser beams to be incident to one end of an image fiber and receives a two-dimensional image of a laser irradiation target transmitted through the image fiber. The optical device includes: a mirror that is arranged on the one end side of the image fiber, reflects the laser beams, and transmits the two-dimensional image; a laser beam source that allows the laser beams to be incident to the one end of the image fiber through reflection of the mirror; an imaging device that receives the two-dimensional image from the one end of the image fiber through transmission of the mirror; and an incidence control device that allows the laser beams to be incident to some cores out of the plurality of cores in the one end of the image fiber and changes cores to which the laser beams are incident.

<CIT> describes an endoscope system of the present invention includes: an image fiber with an image fiber main body made of a plurality of cores for forming pixels and a cladding common thereto; and an optical system connected to an eyepiece side of the image fiber for causing laser light to enter the image fiber and for taking in an image from the image fiber, in which the image fiber has the cores arranged substantially uniformly over a cross-section of the image fiber main body, the cross-section being perpendicular to a longitudinal direction of the image fiber main body.

<CIT> describes multicore fibers and endoscope configurations are provided, along with corresponding production and usage methods. Various configurations include an adiabatically tapered proximal fiber tip and/or proximal optical elements for improving the interface between the multicore fiber and the sensor, photonic crystal fiber configurations which reduce the attenuation along the fiber, image processing methods and jointed rigid links configurations for the endoscope which reduce attenuation while maintaining required flexibility and optical fidelity.

The following is a simplified summary providing an initial understanding of the invention. The summary does not necessarily identify key elements nor limit the scope of the invention, but merely serves as an introduction to the following description.

Various aspects of the present invention provide multicore fibers and endoscope configurations, along with corresponding production and usage methods, which any of adiabatically tapered proximal fiber tips and/or proximal optical elements, for improving the interface between the multicore fiber and the sensor, photonic crystal fiber configurations which reduce the attenuation along the fiber, jointed rigid links configurations which reduce attenuation while maintaining required flexibility and optical fidelity, image processing methods, spectral multiplexing approaches, which increase the information content of the radiation delivered through the fibers and endoscope, as well as fiber-based wave-front sensors.

These, additional, and/or other aspects and/or advantages of the present invention are set forth in the detailed description which follows; possibly inferable from the detailed description; and/or learnable by practice of the present An endoscope according to the present invention is defined in claim <NUM> and comprises:.

Claims <NUM>-<NUM> and <NUM> - <NUM> define preferred embodiments thereof.

A method according to the present invention is defined in claim <NUM> and comprises: reducing optically, a fill factor of cores in a fiber cross section of a multicore imaging fiber comprising at least <NUM>,<NUM> cores with a common cladding, configured to deliver image radiation at a distal end of the fiber, wherein the image radiation is confined to the cores and the cores are interspaced within a fiber cross-sectional area to prevent cross-talk therebetween, by re-orienting the delivered image radiation from the cores to fill an area on an adjacent sensor which is smaller with respect to an area of the fiber cross section.

In the following description, various aspects of the present invention are described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well known features may have been omitted or simplified in order not to obscure the present invention. With specific reference to the drawings, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion 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.

Before at least one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments that may be practiced or carried out in various ways as well as to combinations of the disclosed embodiments. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "processing", "computing", "calculating", "determining", "enhancing", "deriving" or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulates and/or transforms data represented as physical, such as electronic, quantities within the computing system's registers and/or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices. Any of the disclosed modules or units may be at least partially implemented by a computer processor.

Multicore fibers and endoscope configurations are provided, along with corresponding production and usage methods. Various configurations include an adiabatically tapered proximal fiber tip and/or proximal optical elements for improving the interface between the multicore fiber and the sensor, photonic crystal fiber configurations which reduce the attenuation along the fiber, image processing methods and jointed rigid links configurations for the endoscope which reduce attenuation while maintaining required flexibility and optical fidelity. Various configurations include spectral multiplexing approaches, which increase the information content of the radiation delivered through the fibers and endoscope, and configurations which improve image quality, enhance the field of view, provide longitudinal information. Various configurations include fiber-based wave-front sensors. Many of the disclosed configurations increase the imaging resolution and enable integration of additional modes of operation while maintain the endoscope very thin, such as spectral imaging and three dimensional imaging. It is noted that while the following refers to tissue as the imaging object, any other element, object, surface or part may be imaged by the disclosed fibers and endoscopes, and the term "tissue" is not to be taken as limiting the invention in any way. It is further noted that configurations are disclosed separately merely to simplify the respective explanations, and configurations may be combined for endoscopes with two or more of the configurations which may be illustrated in different figures and/or disclosed in different embodiments,.

<FIG> is a high level schematic illustration of a multicore imaging fiber <NUM> having a proximal tapered end <NUM>, according to some embodiments of the invention. Multicore imaging fiber <NUM> receives radiation 95A from imaged tissue <NUM> (as a non-limiting example) at a distal end 100A of fiber <NUM>, transmits the radiation throughout the fiber's length and delivers radiation 95B to a sensor <NUM> at a proximal end 100B of fiber <NUM>. Multicore imaging fiber <NUM> may comprise a large number of cores <NUM> within a common cladding and/or multiple cladding structures <NUM>, e.g., multicore imaging fiber <NUM> may comprise tens or hundreds of thousands cores <NUM>. <FIG> illustrates schematically only few cores <NUM> for explanatory purposes. Certain embodiments comprise endoscopes comprising multicore imaging fiber <NUM>.

Multicore imaging fiber <NUM> comprises at least <NUM>,<NUM> cores <NUM> (possibly <NUM>,<NUM> cores, <NUM>,<NUM> cores or any intermediate number) with a common cladding <NUM> and have proximal tip 100A configured to deliver image radiation 95A from tissue <NUM> at distal end 100B of fiber <NUM>. Image radiation 105A may be confined to cores 110A (having a diameter d1, e.g., between <NUM>-<NUM>, between <NUM>-<NUM> etc.) and cores 110A may be interspaced within fiber cross-sectional area A1 (having a diameter D1, with cores 110A interspaced, L1, e.g., by several µm, e.g., <NUM>-<NUM>) to prevent cross-talk between cores 110A. Cross section 100A may be prevalent from distal end 100A and throughout all of fiber <NUM>, but for tapered end <NUM> thereof, and is illustrated to show each core 110A surrounded by cladding material or structures 112A and with image radiation 105A confined to core 110A. It is noted that cores <NUM> may have a varying degree of order, and may be dispersed through the fiber cross section with a certain degree of randomness. The interspacing, or pitch L1 between cores <NUM> may be understood as average or median interspacing.

Proximal tip with tapered end <NUM> may be very short, e.g., shorter than e.g., <NUM>, <NUM>, <NUM> etc. as indicated by the length T, and be adiabatically tapered to reduce the fiber cross-sectional area (e.g., from fiber diameter D1 and cross-sectional area A1 to a fiber diameter D<NUM> and cross-sectional area A2) and to reduce the core diameter (e.g., from core diameter d1 of cores 110A to a core diameter d2 of cores 110B, and correspondingly pitch L1 to reduced pitch L2) by a factor of at least <NUM>, allowing image radiation 105B to exit narrowed cores 110B. Proximal tip with tapered end <NUM> may be further configured to deliver image radiation 105B as radiation 95B to an adjacent sensor <NUM>, with an effective image area to sensor area ratio (A3:A2) which is much larger than the ratio of original fiber cross sectional area to sensor area ratio (A3:A1). For example, effective image area to sensor area ratio (A3:A2) may be at least <NUM>:<NUM>, <NUM>:<NUM> or even larger, possibly approaching <NUM>:<NUM>. The larger ratio of image area to sensor area enables any of: using smaller sensors <NUM> (as sensor coverage by the image is more efficient), using large sensors <NUM> more efficiently (with more pixels sensing image data) and/or using simpler sensors <NUM> (without gaps between pixels, as interspaces between cores 110A are reduced and radiation 105B may be delivered over most or all of the tapered end's cross sectional area A2). Radiation 105B may exit smaller cores 110B at tapered end <NUM> to deliver radiation 95B to sensor <NUM> over an area which is larger than the cumulative area of cores 110B, while avoiding crosstalk due to the shortness of proximal end 100B and due to the fact that tapered end <NUM> is mechanically fixed and cannot bend.

For example, in certain non-limiting embodiments, an effective area of adjacent sensor <NUM>, which receives image radiation 95B from proximal tip <NUM>, may be at least <NUM>% of the total area (A3) of adjacent sensor <NUM>, possibly even at least <NUM>%, <NUM>% or <NUM>% thereof. In certain embodiments, proximal tip <NUM> may be is shorter than <NUM> and/or stiff. In certain embodiments, reduced fiber cross-sectional area A2 may be smaller than <NUM><NUM>, reduced core diameter d<NUM> may be smaller than smaller than the optical wavelength in order to cause light to get out of the core and to travel in the cladding area (e.g., smaller than <NUM> - <NUM>, smaller than <NUM> - <NUM>, or other values. ), and/or reduced core pitch L<NUM> may be smaller than <NUM>.

Advantageously, disclosed designs improve sensor efficiency using multicore fibers. Applying sensing array <NUM> to present multicore fibers having their proximal end similar of distal end 100A - requires the imaging camera to have enough pixels to sample cores 110A as well as cladding 112A between cores 110A. Moreover, as the camera samples the space uniformly but cores 110A are not completely ordered, regions between cores 110A require waste of camera hardware, namely the sensors have a number of pixels which is much larger than the number of cores 110A in the fiber. In disclosed embodiments however, not only is cross-sectional area 100B much smaller than cross-sectional area 100A, but the spaces between cores 110B are significantly reduced or even avoided, to deliver radiation 95B over most or all of cross-sectional area 100B adjacent to sensor <NUM> because due to the tapering the light propagating in the tapered section is not confined any more to the core region but rather leaks out to the cladding area. It is noted that while the spreading of radiation 105B beyond narrowed cores 110B provides more efficient use of sensor <NUM>, it does not result in crosstalk between cores 110B and does not limit the bending of fiber <NUM>, as proximal tapered end <NUM> is very short (and may further be made stiff to prevent bending). For example, in fiber <NUM> having <NUM>,<NUM> cores <NUM>, sensors <NUM> may have only one or few <NUM>,<NUM> pixels to detect all radiation 95B, 95A, while prior art fibers (having proximal cross-section 100A) may require several megapixels to detect all radiation from tissue <NUM>.

<FIG> is a high level schematic illustration of a multicore imaging fiber <NUM> having a proximal optical element <NUM>, according to some embodiments of the invention. Multicore imaging fiber <NUM> receives radiation 95A from imaged tissue <NUM> (as a non-limiting example) at distal end 100A of fiber <NUM>, transmits the radiation throughout the fiber's length and delivers radiation 95B to sensor <NUM> at proximal end 100B of fiber <NUM>. Multicore imaging fiber <NUM> comprises <NUM>,<NUM> cores <NUM> within a common cladding <NUM>, e.g., multicore imaging fiber <NUM> may comprise tens or hundreds of thousands cores <NUM>. Sensor <NUM> may be part of a detector <NUM> connected to a processing unit <NUM> configured to process delivered radiation 95B and form images therefrom.

<FIG> illustrates schematically only few cores <NUM> for explanatory purposes. The embodiments comprise endoscopes comprising multicore imaging fiber <NUM>.

Multicore imaging fiber <NUM> comprises at least <NUM>,<NUM> cores <NUM> (possibly <NUM>,<NUM> cores, <NUM>,<NUM> cores or any intermediate number) with a common cladding <NUM> and have proximal tip 100A configured to deliver image radiation 95A from tissue <NUM> at distal end 100B of fiber <NUM>. Image radiation 105A may be confined to cores 110A (having a diameter d1, e.g., between <NUM>-<NUM>, between <NUM>-<NUM> etc.) and cores 110A may be interspaced within fiber cross-sectional area A1 (having a diameter D1, with cores 110A interspaced, L1, e.g., by several µm, e.g., <NUM>-<NUM>) to prevent cross-talk between cores 110A. Cross section 100A may be prevalent from distal end 100A and throughout all of fiber <NUM> and is illustrated to show each core 110A surrounded by cladding material or structures 112A and with image radiation 105A confined to core 110A. It is noted that cores <NUM> may have a varying degree of order, and may be dispersed through the fiber cross section with a certain degree of randomness. The interspacing, or pitch L1 between cores <NUM> may be understood as average or median interspacing.

Proximal optical element <NUM> is set between distal fiber end 100B and sensor <NUM> and is configured to collect image radiation from cores <NUM> into a smaller area than the area of distal fiber end 100B, to effectively reduce the fill factor of radiation 95B reaching sensor <NUM> (the fill factor may be seen as the ration between the image radiation delivering cross sectional area and the total cross sectional area of fiber <NUM>). For example, proximal optical element <NUM> may comprise one or more prism(s) and/or grating(s) configured to shift closer image radiation from individual cores so that image radiation 95B reaching sensor <NUM> is at a smaller effective pitch than L1. In certain embodiments, delivered radiation 95B may be shifted in a way that mixing the spatial order of cores <NUM>, and detector <NUM> and/or processing unit <NUM> may be configured to rearrange shifted core image radiation to form a correct image. For example, prism(s) with multiple orientations or Dammann grating(s) (see also <FIG> for an analogous solution) may be used to implement proximal optical element <NUM>. For example, proximal optical element <NUM> may be configured to reduce, optically, a fill factor of cores <NUM> in the fiber cross section by re-orienting the delivered image radiation from cores <NUM> to fill a smaller area on adjacent sensor <NUM> with respect to the area of fiber cross section 100B, e.g., to enable using sensor <NUM> with an area of a third or less of fiber cross section 100B (e.g., the area delimited by cores <NUM>).

It is noted that throughout the disclosure, the term "distal" is used to refer to the ends and associated parts of fiber <NUM> and/or endoscope <NUM> which are far from the endoscope's interface (with the detector or the eye of the user) and close to the imaged tissue and to its surroundings, while the term "proximal" is used to refer to the ends and associated parts of fiber <NUM> and/or endoscope <NUM> which are close to the endoscope's interface (with the detector or the eye of the user) and far from the imaged tissue and to its surroundings. Concerning cores <NUM>, it is noted that cores <NUM> may support a single radiation mode, or in certain embodiments, cores may be multimodal, and support more than one radiation mode, as determined by the numerical aperture (NA) and diameter of cores <NUM> and the delivered wavelength.

It is further noted that fiber <NUM> and/or endoscope <NUM> in any of the disclosed embodiments may be used for near or far filed imaging, or any imaging position therebetween. Near field imaging refers to the formation of an image (of imaged objects, tissues and/or their surroundings) at the distal end of the endoscope fiber, typically at the fiber's tip. The image is then typically transferred through the fiber to the detector, possibly through proximal optical elements. Far field imaging refers to the formation of a Fourier transform of imaged objects, tissues and/or their surroundings at the distal end of the endoscope fiber (e.g., the distal end of the endoscope fiber may be at the aperture or pupil plane of the endoscope's optical system), typically at the fiber's tip. The image of the imaged objects, tissues and/or their surroundings may be formed at the proximal end of the endoscope fiber, typically at the fiber's proximal tip or directly on the detector, possibly through proximal optical elements. Near and/or far field imaging may be implemented by various embodiments of optical systems, e.g., direct imaging without any optical elements between the imaged object or tissue and the fiber tip or imaging through any optical element(s) (e.g., lenses). Optical elements may be positioned between the imaged object or tissue and the distal fiber tip, with the distal fiber tip being at least approximately at the Fourier plane (for far field imaging, also termed aperture plane and pupil plane in different contexts) or at the focus plane (for near field imaging, also termed image plane in different contexts) of the optical elements. Intermediate imaging may also be applicable for fiber(s) <NUM> and/or endoscope(s) <NUM>, with a processing unit being configured to determine the spatial configuration (e.g., relative positions of the Fourier and/or image planes with respect to the fiber's distal tip) and process the delivered radiation from the tissue respectively.

In certain embodiments, endoscope <NUM> may be operated to provide far field imaging, with distal tip 100A of fiber <NUM> being at the Fourier plane of the imaging system (deliver Fourier transform of imaged tissue as the delivered radiation), with the output resolution at detector <NUM> determined by the number of the pixels in the delivered radiation (rather than by the number of cores <NUM> as in near field imaging), because the Fourier domain is sparse and a small number of cores is sufficient to transmit the spectral information (especially in cases cores <NUM> are not periodically ordered and thus the sampling of the Fourier is sparse and not uniform/periodic which is even better for properly representing the information of the object that is to be imaged). In certain embodiments, sparse sampling of the Fourier plane, by setting distal end 100A of fiber <NUM> at a corresponding position with respect to tissue <NUM> (far field imaging) may be used to improve the resolution of resulting images, e.g., by implementing compressed sensing algorithms, with respect to near field imaging, by overcoming the difficulty of imaging tissue <NUM> that corresponds to gaps between cores <NUM> (see e.g., pitch L1 in <FIG> and <FIG>).

<FIG> is a high level schematic illustration of a cross section of a multicore photonic crystal fiber <NUM>, according to some embodiments of the invention. All embodiments comprise endoscopes comprising multicore imaging fiber <NUM>.

In certain embodiments, multicore fiber <NUM> may have a photonic crystal structure composed of multiple air holes <NUM> in at least two types: core-type air holes <NUM> interspaced within the fiber cross-sectional area at a specified core-pitch P1 selected to confine image radiation <NUM> within core-type air holes <NUM>, and cladding air-holes <NUM> (between core-type air holes <NUM>) which are interspaced within the fiber cross-sectional area at a specified cladding-pitch P2 selected to prevent cross-talk between core-type air holes <NUM>. The core diameters (denoted by D's for core-type air holes <NUM> and cladding air-holes <NUM>) may also be configured to support image radiation confinement within core-type air holes <NUM> (e.g., the diameter of core-type air holes <NUM> may be between <NUM>-<NUM>, e.g., <NUM>).

Advantageously, using air holes <NUM> to provide core-type air holes <NUM> reduces the attenuation of radiation <NUM> travelling through cores <NUM> which are made e.g., of polymer material such as poly(methyl methacrylate) (PMMA), polystyrene (PS) etc. Cladding air-holes <NUM> are designed to form a periodic structure around each core-type air hole <NUM> to confine radiation <NUM> therein due to the spatial periodicity of the cladding structure rather than due to differences in the refraction index as in polymer cores. In effect, multicore fiber <NUM> may be seen as providing multicore photonic crystal fibers for the first time. For example, in certain embodiments, multicore fiber <NUM> may have an attenuation coefficient which is smaller by e.g., a factor of <NUM> per length of <NUM> than a comparable multicore fiber having a same number of polymer cores.

<FIG> is a high level schematic illustration of a hybrid endoscope <NUM>, according to some embodiments of the disclosure. Endoscope <NUM> may comprise distal multicore fiber <NUM> optically coupled to a plurality of rigid image-relay elements <NUM>, interconnected by a respective plurality of joints <NUM>.

Distal multicore fiber <NUM>, e.g., an imaging fiber, may be configured to receive image radiation 95A from tissue <NUM> at distal end 100A thereof and deliver the image radiation to proximal end 100B of proximal multicore imaging fiber <NUM>. It is notes that rigid image-relay elements <NUM> are made of materials which are more transparent in the respective wavelength range than core material of fiber <NUM>, providing overall reduction of attenuation along endoscope <NUM> (e.g., rigid image-relay elements <NUM> may be made of glass while fiber cores <NUM> may be made of polymers which are less transparent). For example, rigid image-relay elements <NUM> may be GRIN (graded index) rods and/or lenses made of glass.

Rigid image-relay elements <NUM> interconnected by respective plurality of joints <NUM>, may be configured to deliver radiation travelling through fiber <NUM> as radiation 95B to a detector <NUM> (e.g., sensor <NUM> with corresponding optical element(s)). A distal one of rigid image-relay elements <NUM> may be connected via a corresponding joint 140A to proximal end 100B of distal multicore imaging fiber <NUM>.

Joints 140A, <NUM> may be configured to preserve the delivered image radiation from proximal end 100B of distal multicore imaging fiber <NUM> upon angular movements 136A of rigid image-relay elements <NUM> with respect to each other, to deliver the image radiation at a proximal end 100C of endoscope <NUM>.

Optionally, endoscope <NUM> may further comprise a proximal multicore imaging fiber <NUM>-<NUM> connected to a proximal one of rigid image-relay elements <NUM> via corresponding joint 140B, and configured to deliver the image radiation from proximal rigid image-relay element <NUM> to detector <NUM>.

Joints <NUM>, 140A, 140B may be designed according to the illustrated design principles, as mechanical-optical joints which preserve the imaging condition between adjacent rigid image-relay elements <NUM> (as well as thereto and therefrom, relating to joints 140A, 140B to fibers <NUM>, <NUM>-<NUM>, respectively) so that light is continuously coupled from one link to the next, at different angles of rotation of rigid image-relay elements <NUM>. It is emphasized that in endoscope <NUM>, imaging is maintained as well as a certain degree of flexibility between rigid elements <NUM>, which may suffice for most of the length of endoscope <NUM>. Multicore fibers <NUM> may be used only at imaging end 100A of endoscope <NUM>, and possibly at its detector end 100C. Such configurations may be used to yield long endoscopes <NUM>, without limitations resulting from the length of multicore fiber <NUM> (e.g., attenuation, price, optical performance etc. which at least partly are due to light attenuation through polymer cores <NUM>). Endoscope <NUM> may further comprise sleeves (not shown) to support the disclosed structure mechanically.

In certain embodiments, at least some, or all of rigid image-relay elements <NUM> may comprise glass GRIN links and joints <NUM> may comprise spherical ball lenses <NUM> positioned within mechanical joints <NUM> which are connected mechanically to adjacent rigid image-relay elements <NUM> or fibers <NUM>, <NUM>-<NUM> (for joints <NUM>, 140A, 140B, respectively). Spherical ball lenses <NUM> may be positioned to preserve, proximad (in proximal direction), the delivered image radiation in any angular relation between adjacent rigid links <NUM>. For example, spherical ball lens <NUM> may be positioned in the center of mechanical sliding ring <NUM> in distances fulfilling the imaging condition between an exit face 130A of one link <NUM> positioned on one side of joint <NUM> and an entrance face 130B of next adjacent link <NUM> positioned on the other side of joint <NUM>. Alternatively, optical elements <NUM> may be used in place of spherical ball lenses <NUM>. Optical elements <NUM> such as spherical ball lens <NUM> may be configured to create coupling of light from one link <NUM> to the next link <NUM> for any possible angle (or angles within a specified range which is limited mechanically) created between links <NUM>.

<FIG> are high level schematic illustrations of endoscope <NUM> and illumination sources <NUM> thereof, according to some embodiments of the disclsoure.

Certain embodiments comprise endoscopes <NUM> comprising an illumination source <NUM> (see <FIG>), configured to deliver illumination <NUM> (e.g., via one or more illumination fiber(s) <NUM>) at a specified plurality of distinct wavelengths, detector <NUM> comprising a spectrometer <NUM> (in addition to sensor <NUM> and optionally optical elements <NUM>) configured to decode detected radiation 95B in the specified plurality of distinct wavelengths, multicore imaging fiber <NUM> configured to deliver, through cores <NUM> to detector <NUM>, image radiation 95A received from tissue <NUM> illuminated by illumination <NUM> from illumination source <NUM>, and processing unit <NUM> configured to derive, from the decoded detected image radiation of each of cores <NUM>, image data corresponding to the specified plurality of distinct wavelengths. Applying illumination at the plurality of distinct wavelengths, simultaneously or sequentially and analyzing received images with respect to the plurality of wavelengths for each core <NUM>, is referred to herein as spectral, or wavelength, multiplexing.

For example, as illustrated schematically in <FIG>, multiple input fibers <NUM> may be configured to deliver the distinct wavelengths (denoted λ<NUM>. λN) as narrowband radiation to a multiplexer <NUM>, e.g., a wavelength-division multiplexer (WDM), which combines the radiation into illumination <NUM>, delivered through illumination fiber <NUM> to tissue <NUM>. Narrowband input fibers <NUM> may thus be coupled through multiplexer <NUM> to deliver multiple distinct wavelengths simultaneously or temporally separated. Correspondingly, as illustrated schematically in <FIG>, spectrometer <NUM> may receive radiation 95B from multicore fiber <NUM> and separate it into the distinct wavelengths <NUM> (denoted λ<NUM>. λN), by a de-multiplexer <NUM>, e.g., a wavelength-division multiplexer/de-multiplexer (WDM) (possibly even the same as WDM <NUM>). The resulting narrowband radiation channels <NUM> may be delivered to sensor(s) <NUM>, e.g., via optics <NUM>, and the resulting data may be delivered to processing unit <NUM> which may be configured to derive multiple data channels from each core <NUM>. Wavelength multiplexing may thus be configured to increase the information content passed through each core <NUM> significantly, possibly by factors of tens, hundreds or even thousands, depending on the number of the distinct wavelengths and the ability to crowd narrowband wavelength ranges within the spectrum used for imaging (e.g., in the visible range of ca. <NUM>-<NUM>, bandwidths of <NUM> provide N=<NUM> distinct wavelengths denoted λ<NUM>.

Disclosed wavelength multiplexing may be used to enhance resolution of endoscope <NUM> and/or to incorporate additional functionalities or modalities such as OCT (optical coherence tomography), spectroscopical analysis etc. in addition to imaging - to implement multi-functional micro-endoscope <NUM>. For example, an OCT application may be used to extract depth information for internal tissues <NUM>. In certain embodiments, endoscope <NUM> may be configured to implement Fourier domain OCT with illumination source <NUM> being configured to have spectral scanning capability to enable capturing and processing a plurality of 2D images at the range of scanned wavelengths by full field Fourier domain OCT application. In certain embodiments, illumination source <NUM> may be configured to be spectrally tunable, and images at the plurality of wavelengths may be captured and assembled by processing unit <NUM> after each (time scanning) of the range of wavelengths, to provide a 2D spatial image with spectral information per each pixel. In certain embodiments, various spectral ranges may be scanned, e.g., fluorescence bands for fluorescent microscopy or other specific ranges - further enhancing the versatility and number of functionalities of endoscope <NUM>.

Multicore imaging fiber <NUM> and endoscope <NUM> may be implemented as any of the embodiments disclosed herein, e.g., as multicore imaging fiber <NUM> having a proximal tapered end <NUM>, as multicore photonic crystal fibers <NUM> and/or as endoscope <NUM> with distal multicore fiber <NUM> optically coupled to jointedly-interconnected rigid image-relay elements <NUM>.

<FIG> is a high level schematic illustration of temporal spectral multiplexing in illumination source <NUM>, according to some embodiments of the disclosure. Illumination source <NUM> may comprise a fiber laser <NUM> comprising a broadband Bragg filter mirror <NUM> for a range of the specified plurality (N) of distinct wavelengths (denoted λ<NUM>-λN), a controllable <NUM>-to-N switch <NUM> connected to N narrowband Bragg filter mirrors <NUM> (denoted λ<NUM>. λN), for the corresponding distinct wavelengths, each of narrowband Bragg filter mirrors <NUM> designed to reflect only the corresponding distinct wavelength. <NUM>-to-N switch <NUM> may be controlled electrically (or mechanically, optically etc.). Illumination source <NUM> may further comprise a pumped gain in-fiber medium <NUM> connected between Bragg filter mirror <NUM> and controllable <NUM>-to-N switch <NUM> with connected N narrowband Bragg filter mirrors <NUM>. Illumination source <NUM> may further comprise multiplexer <NUM> (e.g., WDM) configured to combine illumination radiation from N narrowband Bragg filter mirrors <NUM> and provide illumination <NUM>, delivered through illumination fiber <NUM> to tissue <NUM> - simultaneously or in a temporally tunable manner with respect to the range or sub-ranges of the distinct wavelengths.

It is emphasized that the configuration illustrated in <FIG> may also be reversed to be used as spectrometer <NUM>, as shown schematically in <FIG> with respect to <FIG>, for example, spectrometer <NUM> configured to provide narrow band imaging detection. In certain embodiments, narrow band imaging detection may be used for improved diagnosis of cancerous tissues.

Alternative or complementary implementations of spectral multiplexing may comprise a plurality of wavelength specific beam splitters or gratings, configured to provide the multiple narrowband spectral ranges at λ<NUM>.

Spectral multiplexing may be used to enhance any of various characteristics of fiber(s) <NUM> and endoscope(s) <NUM> such as resolution, field of view, working distance, depth of focus, 3D capability etc. - by multiplying the amount of information delivered through each core <NUM> by a factor of <NUM>, <NUM> or even <NUM> (depending on the spectral range and spectral resolution). These enhancements may be carries out with respect to one or more fiber modules in endoscope <NUM> and/or replace the need to use several fiber modules in the endoscope (fiber modules referring to associated fibers <NUM> which handle image delivery cooperatively). Spectral multiplexing may also be used to implement super resolved imaging achieved by various means, utilizing the multiple inputs per core <NUM> which correspond to the multiple wavelengths.

<FIG> are high level schematic illustrations of endoscope <NUM> and illumination sources <NUM> thereof, configured to implement wavelength multiplexing super resolved imaging, according to some embodiments of the disclosure. Endoscope <NUM> may be configured to have broadband illumination source <NUM>, e.g., a white light source, and comprise a spatial encoder <NUM> configured to split the broadband illumination spatially, delivering different narrowband wavelength ranges to different locations on tissue <NUM> (illustrated schematically in <FIG> as pattern <NUM>, <FIG> illustrates a non-limiting example for pattern <NUM>). Spatial encoder <NUM> may comprise e.g., dispersive optical elements such as one or more gratings, transmissive optical elements such as one or more prisms and/or may possibly comprise de-multiplexer <NUM> as disclosed above for separating individual wavelengths λ<NUM>. λN from the broadband illumination in combination with elements such as DLP (digital light processing elements), mirror arrays etc. - and delivering different λ<NUM>. λN to different locations on tissue <NUM>.

For example, the wavelength range λ<NUM>. λN may be scanned at a folded linear pattern <NUM> exemplified in <FIG> to cover given region 90A with different locations illuminated by different wavelengths λ<NUM>. The spatio-spectral resolution may be configured to cover larger region 90A with larger locations per wavelength, or smaller region 90A with smaller locations per wavelength; or alternatively or complementarily, the number of distinct wavelengths (N) and/or the wavelength range (λ<NUM>, λN) may be configured to increase or reduce the spectrally-encoded spatial resolution.

Illumination <NUM> may therefore be configured to be spatially encoded by wavelength, illuminating each location on tissue <NUM> at a different wavelength, possibly according to a specified pattern <NUM>. <FIG> illustrates schematically a non-limiting example for the optical implementation of illuminating pattern <NUM>, namely by using a first grating <NUM> for implementing the spectral raster splitting and a second Dammann-like grating <NUM> configured to replicate the spectral raster encoding to fully illuminate the full field of view of tissue <NUM>, illuminating pattern <NUM> on all tissue regions 90A of tissue <NUM> (illustrated in a highly schematic manner in <FIG>). Spatial encoder <NUM> may be configured to use white light illumination <NUM> with grating <NUM>, <NUM> to deliver multiple illuminating patterns <NUM> to all tissue regions 90A of tissue <NUM>, with radiation from each tissue region 90A delivered to a different core <NUM>. Encoded radiation <NUM> may be delivered to tissue <NUM> through one or more optical element(s) 168A, e.g., configured to delivered focused encoded radiation <NUM>, to project pattern <NUM> of tissue regions 90A (with the distance of optical element(s) 168A from tissue <NUM> being equal to the focus length, F, of optical element(s) 168A).

It is emphasized that fiber <NUM> may be configured to have sparse cores <NUM> (see <FIG>, <FIG>), with some or each of cores <NUM> receiving radiation 105A from region 90A illuminated by full pattern <NUM> (or possibly a part thereof) so that the region between any two cores <NUM> may be multiplexed with wavelengths λ<NUM>. λN to make each spatial pixel guided in core <NUM> include actually many spatial points of information encoded by the different wavelengths according to pattern <NUM>. The resulting is image, analyzed by spatial decoder <NUM>, may therefore have much more spatial pixels of information than the number of cores <NUM> (e.g., maximally N times the number of cores).

Radiation 95A from tissue <NUM> may therefore be likewise spatio-spectrally encoded, and multicore fiber <NUM> may be configured to deliver radiation 95A from a region 90A (indicated schematically) of tissue <NUM>, including multiple wavelengths which encode different locations in region 90A, to detector <NUM>. Each core <NUM> may therefore be configured (e.g., by focusing and de-focusing) to deliver spectrally-encoded information from multiple locations on tissue <NUM>, e.g., region 90A). Detector <NUM> may comprise spectrometer <NUM> (e.g., implemented as disclosed above, using principles disclosed in <FIG> and/or 4D) and a spatial decoder <NUM> configured to decode spatial reflectivity information from the spectral information - providing N data points for each core <NUM>. Therefore each core <NUM> may be used to deliver data for multiple pixels on sensor <NUM>, which correspond to the spectrally encoded region 90A of tissue <NUM>.

Certain embodiments comprise endoscope <NUM> comprising illumination source <NUM> comprising spatial encoder <NUM>, configured to deliver illumination <NUM> at specified plurality of spatially-encoding distinct wavelengths λ<NUM>. λN , with different wavelengths illuminating different locations on a tissue according to specified spatio-spectral pattern <NUM>; detector <NUM> comprising spectrometer <NUM> and spatial decoder <NUM>, configured to decode detected radiation 95B in specified plurality of distinct wavelengths λ<NUM>. λN according to specified spatio-spectral pattern <NUM>; multicore imaging fiber <NUM> comprising cores <NUM> and configured to deliver (95B), through cores <NUM> to detector <NUM>, image radiation 95A received from tissue <NUM> illuminated by illumination source <NUM>, wherein at least some, or each core <NUM> is configured to deliver image radiation 95A from a tissue region illuminated by specified spatio-spectral pattern <NUM>; and processing unit <NUM> configured to derive, from spatio-spectrally decoded detected image radiation 95B of single cores <NUM>, image data corresponding to specified plurality of distinct wavelengths λ<NUM>. λN from image radiation delivered by each core <NUM>. In certain embodiments, spatial encoder <NUM> may be implemented by first grating <NUM> configured to split broadband (e.g., white light) illumination into specified plurality of distinct wavelengths λ<NUM>. λN and second grating <NUM> configured to replicate the split broadband illumination to multiple patterns <NUM> corresponding to different regions of tissue <NUM>.

<FIG> is a high level schematic illustration of endoscope <NUM> with a multimode, multicore illumination fiber <NUM>, according to some embodiments of the disclosure. In certain embodiments, illumination source <NUM> may be configured to deliver illumination <NUM> through single mode, multicore illumination fiber <NUM> to generate a speckle pattern <NUM> on tissue <NUM> which is more uniform and with larger speckles than different types of illumination, such as by a multimode illumination fiber with a large-area core. Single mode, multicore illumination fiber <NUM> may be configured to have about the same area as a single core multimode illumination fiber, to deliver a comparable amount of illumination or energy, while delivering the illumination through multiple cores having almost identical axial lengths of the respective light channels (due to the fabrication process). As the optical paths are practically identical, resulting speckle pattern <NUM> consists of large speckles (due to interference of light coming from the different cores which are small in dimensions) and is more uniform than single core multimode illumination. Advantageously, larger speckles require simpler speckle averaging and reduction and are therefore advantageous with respect to resulting image quality and required processing power. Moreover, cores of single mode, multicore illumination fiber <NUM> may be optimized with respect to core size and number to maximize the size of speckles in the illumination channel and in pattern <NUM>. Processing of the distal tip of illumination fiber <NUM> (e.g., may also be configured to enhance the coherence of illumination radiation delivered through different cores.

Processing unit <NUM> may be configured to identify and remove from delivered image radiation 95B, speckle pattern <NUM> from illumination <NUM> by single mode, multicore illumination fiber <NUM>.

In certain embodiments, illumination may be implemented by one or more multimode multicore illumination fiber <NUM> with cores having a small number of multiple modes (e.g., <NUM>-<NUM> modes, or few tens, e.g., <NUM>-<NUM> modes) to provide additional flexibility in enhancing the uniformity of the speckle's formation altogether.

In certain embodiments, the shape of the illumination spot may be modulated to remove secondary speckle patterns, which depend on the spot size, by image processing. In certain embodiments, processing unit <NUM> may be configured to modulate, via illumination source <NUM>, illumination <NUM> with respect to at least one illumination spot parameter such as any of the shape, the diameter and/or the spatial modes of the illumination spot, e.g., according to a specified pattern. Processing unit <NUM> may be further configured to use the specified pattern to analyze resulting changes in the image of the illumination spot, as detected by detector <NUM>, and remove features of the image that fluctuate according to the specified pattern, as being related to secondary speckle patterns rather than to the imaged tissue. Advantageously, the contrast of the secondary speckle patterns may be significantly reduced and the image quality significantly improved. It is noted that removable secondary speckle patterns relate to features that may be modified by modulating illumination <NUM>, while some residual, primary speckle patterns may remain, such as features relating e.g., to the size of the diffuser (not shown) through which illumination <NUM> is performed.

<FIG> are high level schematic illustrations of endoscope <NUM> with multicore fiber <NUM> with multimode cores having tens of modes, according to some embodiments of the disclosure. Multicore fiber <NUM> may be configured to have a relatively small number of cores, e.g., several tens of modes (e.g., <NUM>, <NUM>, <NUM>, <NUM>) or a few hundred modes (e.g., <NUM>, <NUM>, <NUM>) to implement a hybrid multicore fiber <NUM> in the sense that cores <NUM> are not single mode cores, but also not the customary multimode cores supporting many hundreds or thousands of modes. Complementarily, processing unit <NUM> may comprise a mode-decoupling module <NUM>, configured to remove distortions which may be caused by mode mixing at bends of hybrid multicore fiber <NUM>. Advantageously, while the use of multimode cores increases the information content of delivered radiation 95B, endoscope <NUM> does not become as sensitive to bending of fiber <NUM> as are prior art fibers supporting thousands or even tens of thousands of modes, because the computational effort in removing the distortions due to mode mixing is tolerable, and achievable by available processors for such applications.

When fiber <NUM> is bended in operation, the different modes are mixed and the image guided by through them is distorted, yet the distortions may be inverted by applying e.g., deep learning neural network algorithms by mode coupling module <NUM>. Since every core <NUM> has small number of modes (e.g., tens of modes, much less than regular multimode fibers) the inversion of the modes-mixing due to bending may be carried out in real time.

In certain embodiments (see e.g., <FIG> as a non-limiting example), illumination source <NUM> may be configured to project a point (or any pattern) <NUM> on tissue <NUM> and processing unit <NUM> may be configured to estimate distortions by analyzing a distortion of illuminated point (or pattern) <NUM> in its image <NUM> (illustrated schematically) delivered through fiber <NUM> (within region 90B of tissue <NUM> imaged by fiber <NUM> and indicated schematically as image 95B). Mode coupling module <NUM> may be configured to enhance distortion cleaning calculations using the distortion estimation of illuminated point or pattern <NUM>. Advantageously, the overall resolution is significantly increased without adding too much overload to the processing power of processing unit <NUM>. For instance, in an illustrative non-limiting example, assuming a 450X450 micron fiber <NUM> with <NUM>,<NUM> cores <NUM>, with every core <NUM> having <NUM> modes, the received image (95B) would have of <NUM> pixels instead of only <NUM> pixels when cores <NUM> are single mode. Certain embodiments of hybrid fiber <NUM> avoid both the difficulty in producing single mode cores in the multicore fiber and the requirement for rigidity in multimode fibers (to prevent mixing of modes which not feasible to correct) to combine the benefits of information increase when using multimode multicore fibers with reduced sensitivity to bending due to the relatively small number of modes.

<FIG> are high level schematic illustrations of endoscope <NUM> with enhanced field of view, according to some embodiments of the disclosure. In certain embodiments, endoscope <NUM> may be configured to have a large field of view without need to bend the distal tip of endoscope <NUM> and fiber <NUM>. It is noted that the common practice of bending the distal tip of endoscope <NUM> to increase the field of view requires a large volume near tissue <NUM> for handling the distal tip of endoscope <NUM> (due to the limited bending radius thereof), while in disclosed embodiments a much smaller volume is required to accommodate disclosed distal tip optical elements <NUM> which provide a large enhancement of the field of view. Distal tip optical elements <NUM> may be configured to be controllably displaceable with respect to each other (perpendicularly to their optical axes), with relative displacement 192A configured to change the field of view (192B) of fiber <NUM>, as illustrated schematically in <FIG>.

As illustrated schematically in <FIG>, in a non-limiting example, distal tip optical elements <NUM> may comprise a first lens 191A with a negative focal length and a second lens 191B with a positive focal length at distal tip 100A of fiber <NUM>. Shifting 192A of the relative position of lenses 191A, 191B may be configured to implement a tunable prism (see Equation <NUM> below). With distal tip optical elements <NUM>, shifting (192A) lenses 191A, 191B with respect to each other increases the field of view (192B) of endoscope <NUM> by increasing only the size of the distal tip of endoscope <NUM> without requiring to bend the distal tip of endoscope <NUM>, which requires large free volume available. Moreover, changing the distance (192A) between lenses 191A, 191B may be configured to realize optical zooming (alternatively or possibly in addition to field of view enhancement). A mechanism <NUM> may be configured to perform shifts 192A between lenses 191A, 191B (perpendicularly to their optical axes). For example, mechanical implementations of mechanism <NUM> may comprise controllably movable sleeves connected to lenses 191A, 191B and/or by springs similar to existing springs connected to the navigation shield (not shown) of endoscope <NUM> which may transfer a longitudinal shift 192C of these elements to perpendicular shift 192A of lenses 191A, 191B.

The following Equation <NUM> demonstrates that changing a relative shift between lenses 191A, 191B (left-hand expression in Equation <NUM>) is equivalent to a prism (right-hand expression in Equation <NUM>) with an angle that is proportional to the amount of the relative shift (192A) between lenses 191A, 191B, with T(x) denoting the overall transmission expression of lenses 191A, 191B as illustrated schematically in <FIG>, having the same focal length F in absolute value (lens 191A with -F and 191B with +F), positioned sequentially with a relative transversal shift of <NUM>Δx between them, and λ denoting the optical wavelength.

The overall transmission expression of the emulated prism (right-hand expression in Equation <NUM>) reflects a prism positioned on the aperture plane of an imaging lens which shifts the obtained image by a factor of 2Δx which is exactly the relative shift between two lenses 191A, 191B. By tuning (192A) the amount of shift (by changing Δx), the field of view of fiber <NUM> may be scanned, providing a larger field of view than merely the physical field of view of the given imaging lens.

<FIG> are high level schematic illustrations of longitudinally-sensing endoscope <NUM>, according to some embodiments of the disclosure. In certain embodiments, endoscope <NUM> may be configured to have sensing capabilities along at least part of its length. For example, fiber <NUM> may be configured to have a plurality of peripheral radiation entrance locations <NUM> ("windows"), configured to allow radiation from the sides of fiber <NUM> to enter peripheral cores 110C of fiber <NUM>, as illustrated schematically in <FIG>. Different peripheral cores 110C may be configured along fiber <NUM> to receive radiation 95C from different locations, e.g., from locations along a body conduit <NUM> such as a blood vessel, by corresponding configuration of peripheral radiation entrance locations <NUM> along endoscope <NUM>. Illumination fiber <NUM> may be configured to emit radiation 65A along endoscope <NUM>, to improve or enable sensing reflected radiation 95C from surrounding tissue <NUM> by fiber <NUM>.

For example, peripheral radiation entrance locations <NUM> may be arranged in circles <NUM>, each circle <NUM> being connected to a different peripheral core 110C as illustrated schematically in <FIG>. Such configurations may be used to extract the distance of fiber <NUM> from tissue <NUM> along its longitudinal axis by extracting the readout of peripheral cores 110C while internal cores <NUM> are used to imaging explained above. The longitudinal sensing may therefore be used to improve the control of endoscope <NUM>, avoiding lateral damage to tissue <NUM> and provide data concerning tissue <NUM>. In certain embodiments, peripheral radiation entrance locations <NUM> such as circles <NUM> may be formed by controlled twisting of the pre-form during its drawing to yield fiber <NUM>. <FIG> provides a non-limiting example for such actual fiber <NUM> with slits <NUM> produced by the inventors.

Endoscope <NUM> may further comprise processing unit <NUM> configured to derive longitudinal data <NUM> from radiation 95C delivered through the specified peripheral cores, in addition to image data <NUM> delivered from the distal tip of fiber <NUM>. Illumination fiber <NUM> may correspondingly be configured to emit radiation 65A along endoscope <NUM>, in addition to illuminating <NUM> tissue <NUM> at the distal end thereof. Endoscope <NUM> may be further configured, e.g., via processing unit <NUM>, to derive indications for tissue <NUM> in proximity to fiber <NUM> along its length.

<FIG> is a high level schematic illustration wave-front sensing endoscopes <NUM>, according to some embodiments of the disclosure.

Endoscope <NUM> may comprise illumination source <NUM>, configured to deliver illumination <NUM> at a specified plurality of spatially distinct locations on tissue <NUM>, detector <NUM> and multicore imaging fiber <NUM> comprising multimode cores <NUM> which are configured to support more than one radiation mode in core <NUM>, e.g., any of <NUM>-<NUM> modes, or possibly between <NUM>-<NUM> or <NUM>-<NUM> modes (configured, without being bound by theory, according to V=π·A·(NA/λ)<NUM>, with V the number of modes, A the cross sectional area of core <NUM>, NA the numerical aperture of core <NUM> and λ the corresponding wavelength, see the detailed analysis below). Multicore imaging fiber <NUM> may be configured to deliver, through multimode cores <NUM> to detector <NUM>, wave-front radiation <NUM> received from tissue <NUM> illuminated by illumination source <NUM>. Wave-front radiation <NUM> may be delivered though cores <NUM> without any optical elements at distal fiber tip 100A, or as modified wave-front radiation 96A which may be modified by optical elements <NUM> between distal fiber tip 100A and tissue <NUM> (e.g., perforations, lenslets, Shack Hartmann interferometer configurations, pinholes array configurations, etc.). For example, optical elements <NUM> may be configured to focus sections of wave-front radiation <NUM> into cores <NUM>, to generate modified wave-front radiation 96A in which phase information in wave-front radiation <NUM> is modified to spatial information (e.g., orthogonal focus point translations illustrated schematically by the double-headed arrow), which is delivered through cores <NUM> along multicore fiber <NUM>. Endoscope <NUM> may further comprise processing unit <NUM> configured to derive, from the delivered wave-front radiation <NUM> and/or 96A, three dimensional (3D) image data <NUM> derived from wave-front radiation <NUM>, e.g., according to spot position changes associated with each or some of cores <NUM>. The spot position changes indicate the angle of the wave-front entering respective cores <NUM>.

An example for such configurations follows. The number of modes supported by multimode cores <NUM> may be selected as a tradeoff between information delivery capacity of cores <NUM> and the sensitivity of the delivered modes to bending of fiber <NUM> (e.g., configurations less prone to bending, cores <NUM> may be configured to support more modes). This tradeoff is described below, and fibers <NUM> may be configured to implement various tradeoffs, with cores supporting a range of number of modes. The number of modes (V) may be expressed by Equation <NUM>, with NA denoting the numerical aperture, a is the radius of a core, λ denoting the wavelength of the light, and ncore and ncladding denoting the corresponding refractive indices.

The single mode condition requires V<<NUM> and the number of modes (M) is proportional to <NUM>·(V/<NUM>)<NUM> , or specifically for a step index fibers M=4V<NUM>/π<NUM>. The tradeoff of the number of modes with respect to crosstalk between cores <NUM> may be expressed in terms of the width of the Gaussian profile of the field propagating through optical core <NUM> (denoted by W, defined for a field value that is <NUM>/e of its maximal value) and the pitch L between cores <NUM> - expressed in Equations <NUM> in terms of V (number of modes) and a (core radius). For example, a condition for preventing crosstalk between cores <NUM> may be defined as L≥2W, providing a relation between pitch (L) and core radius (a).

Such condition may be balanced in fiber design with respect to the 3D resolution achievable by the core multimode configuration, which may be expressed as follows. The 3D resolution in space equals to the pitch size L (related to the core size) and the resolution in phase φ sensitivity to wavefront <NUM> equals to 2π/√M in every axis (y and x). Thus, the angular sensitivity in the direction of propagation along the axial direction Z, Δθz, may be expressed and approximated and expressed in to Equation <NUM>.

The reciprocal relation between Δθz and V indicates that increasing the number of modes (V) improves sensitivity (as smaller angles Δθ can be sensed) but as shown above, increasing V also increases the sensitivity to fiber bending (increases crosstalk through modes coupling). The reduction in the bending angle (affects the bending radius of the fiber) is proportional to the root of the number of modes, √M, which is proportional to 4a·NA/λ.

Equations <NUM>-<NUM> and the considerations presented above clearly describe the ways specific fiber configurations may be carried out to optimize endoscope performance with respect to mechanical requirements and wave-front sensing (3D resolution) requirements. Various applications of endoscope may imply different fiber configurations with respect to fiber rigidness, core parameters (size and pitch) and achieved spatial resolution.

It is noted that wave-front sensing endoscopes <NUM> may be implemented as any of the embodiments disclosed herein, e.g., as multicore imaging fiber <NUM> having a proximal tapered end <NUM>, as multicore photonic crystal fibers <NUM> and/or as endoscope <NUM> with distal multicore fiber <NUM> optically coupled to jointedly-interconnected rigid image-relay elements <NUM>.

<FIG> is a high level flowchart illustrating a method <NUM>, according to some embodiments of the invention. The method stages may be carried out with respect to endoscopes <NUM> and/or fibers <NUM> described above, which may optionally be configured to implement method <NUM>. Method <NUM> may be at least partially implemented by at least one computer processor. Certain embodiments comprise computer program products comprising a computer readable storage medium having computer readable program embodied therewith and configured to carry out of the relevant stages of method <NUM>. Method <NUM> may comprise stages for producing, preparing and/or using device endoscopes <NUM> and/or fibers <NUM>, such as any of the following stages, irrespective of their order.

Method <NUM> may comprise adiabatically tapering a proximal tip of a multicore imaging fiber (stage <NUM>) comprising at least <NUM>,<NUM> cores with a common cladding, configured to deliver image radiation from tissue at a distal end of the fiber, wherein the image radiation is confined to the cores and the cores are interspaced within a fiber cross-sectional area to prevent cross-talk therebetween, and configuring the adiabatically tapered proximal tip (stage <NUM>) to be shorter than <NUM> and have a fiber cross-sectional area and a core diameter which are reduced by a factor of at least <NUM> with respect to the multicore imaging fiber, to allow the image radiation exit the narrowed cores and deliver the image radiation to an adjacent sensor. Certain embodiments comprise reducing, optically, the fill factor of the delivered image by re-orienting delivered image radiation from the cores to fill a smaller area on the sensor (stage <NUM>).

Method <NUM> may comprise configuring multicore fiber from a photonic crystal structure (stage <NUM>) composed of multiple air holes, by designing the air holes to be in at least two types: core-type air holes, interspaced within a fiber cross-sectional area at a specified core-pitch selected to confine image radiation within the core-type air holes, and cladding air-holes between the core-type air holes, the cladding air-holes interspaced within the fiber cross-sectional area at a specified cladding-pitch selected to prevent cross-talk between the core-type air holes.

Method <NUM> may comprise configuring an endoscope from a distal multicore imaging fiber and a plurality of rigid image-relay elements (stage <NUM>), wherein the distal multicore imaging fiber is configured to receive image radiation from tissue at a proximal end thereof and deliver the image radiation to a distal end of the distal multicore imaging fiber, and interconnecting the rigid image-relay elements by a respective plurality of joints (stage <NUM>), wherein a distal one of the rigid image-relay elements is connected via a corresponding joint to the proximal end of the distal multicore imaging fiber. The joints are configured to preserve the delivered image radiation from the proximal end of the distal multicore imaging fiber upon angular movements of the rigid image-relay elements with respect to each other, to deliver the image radiation at a proximal end of the endoscope. Method <NUM> may further comprise connecting a proximal multicore imaging fiber (stage <NUM>) to a proximal one of the rigid image-relay elements via a corresponding joint, to deliver the image radiation from the proximal rigid image-relay element.

Method <NUM> may comprise using spectral multiplexing to enhance the information content of the delivered radiation (stage <NUM>) and encoding, spectrally, the radiation delivered through each of the cores, and decoding therefrom multiple data points per core (stage <NUM>). For example, method <NUM> may comprise illuminating tissue by a specified plurality of distinct wavelengths, delivering image radiation received from illuminated tissue through each of a plurality of cores of a multicore imaging fiber, decoding, for each of the cores, detected radiation in the specified plurality of distinct wavelengths, and deriving from the decoded detected image radiation of each of the cores, image data corresponding to the specified plurality of distinct wavelengths. Method <NUM> may further comprise implementing super resolved imaging utilizing multiple inputs per core which correspond to the multiple wavelengths (stage <NUM>).

Method <NUM> may comprise using spatio-spectral encoding and decoding of illumination to enhance spatial resolution by spatio-spectral patterned illumination (stage <NUM>), e.g., by illuminating tissue by a specified plurality of distinct wavelengths at a specified spatio-spectral pattern, delivering image radiation received from illuminated tissue through each of a plurality of cores of a multicore imaging fiber, decoding, for each of the cores, detected radiation in the specified plurality of distinct wavelengths according to the specified spatio-spectral pattern, and deriving from the decoded detected image radiation of each of the cores, image data corresponding to the specified plurality of distinct wavelengths and according to the specified spatio-spectral pattern.

Method <NUM> may comprise illuminating the tissue by a single mode, multicore illumination fiber to increase speckle size and possibly removing speckle effects (stage <NUM>), e.g., by using a single mode, multicore illumination fiber to illuminate a tissue imaged by a multicore imaging fiber and optionally identifying and removing from image radiation delivered by a multicore imaging fiber, a speckle pattern from the illumination by the single mode, multicore illumination fiber. Method <NUM> may further comprise modulating the shape of the illumination spot and removing secondary speckle patterns, which depend on the spot size, by image processing (stage <NUM>).

Method <NUM> may comprise imaging an illuminated tissue by a multicore imaging fiber having cores configured to support between <NUM>-<NUM> modes, and decoupling the modes by removing mode-mixing distortions from image radiation delivered by the fiber (stage <NUM>).

Method <NUM> may comprise increasing a field of view of an imaging fiber (stage <NUM>) by implementing a tunable prism at a distal tip thereof, e.g., by controllably displacing distal tip optical elements with respect to each other to change a field of view of the fiber, possibly using distal tip optical elements with opposite focal lengths +F and -F.

Method <NUM> may comprise introducing radiation laterally into peripheral cores to derive indications of the proximity of surrounding tissue (stage <NUM>), e.g., by enabling radiation to enter through sides of a multicore imaging fiber and into specified peripheral cores thereof, and deriving longitudinal data concerning tissue surrounding the fiber from radiation delivered through the specified peripheral cores. For example, method <NUM> may comprise designing peripheral slits in the fiber to enable the radiation enter the specified peripheral cores.

Claim 1:
An endoscope comprising:
a multicore imaging fiber comprising at least <NUM>,<NUM> cores with a common cladding and configured to deliver image radiation at a distal end of the fiber, wherein the image radiation is confined to the cores and the cores are interspaced within a fiber cross-sectional area to prevent cross-talk therebetween;
a sensor adjacent to a proximal tip of the multicore imaging fiber; and
a proximal re-orienting element for re-orienting the delivered image radiation from the cores to fill an area on the adjacent sensor that is smaller than a cross-section area of the multicore imaging fiber.