Method and apparatus for reconfigurable optical endoscopy catheters

Abstract

Several configurations of optical systems are disclosed herein. In some embodiments, the optical system includes a substrate having a first surface and a second surface, and a first reflector disposed on the substrate and configured to receive light. The light includes at least one of light of a first wavelength and light of a second wavelength. The first reflector is configured to reflect the light of the first wavelength along a first optical path toward the first diffractive lens and transmit the light of the second wavelength toward the second reflector. The second reflector is configured to reflect the light of the second wavelength along a second optical path toward the second diffractive lens.

Description

【Technical Field】 【0001】 Cross - Reference to Related Applications This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 189,053, filed May 14, 2021, "Methods and Apparatus for a Reconfigurable Optical Endoscopic Catheter". The entire subject matter of the above application is hereby incorporated by reference in its entirety. Technical Field The present disclosure generally relates to miniaturized optical imaging and irradiation systems, devices, and instruments. More specifically, this disclosure presents methods, systems, devices, and instruments for implementing miniaturized medical imaging based on an optical endoscope catheter, including optical coherence tomography, Raman spectroscopy, and / or fluorescence spectroscopy techniques. 【Background Art】 【0002】 Accurate diagnosis and treatment of diseases in tubular organs such as the coronary arteries, pulmonary airways, and gastrointestinal tract are challenging, especially in vivo, due to the difficulty of accessing the lesions. This is the main motivation behind the miniaturization of optical imaging and irradiation (for therapeutic purposes) systems. One commonly used imaging system is the endoscopic optical coherence tomography (OCT) catheter. In a typical endoscopic catheter, optical power is delivered through an optical fiber to the distal end of the catheter, and then it is redirected and focused into the tissue via several cascaded optical components. Two common approaches to redirecting and focusing the light are based on (i) a distributed refractive index (GRIN) lens and prism, and (ii) an angle-polished ball lens. In the former, the GRIN lens focuses the light, and then the prism redirects the light (radially relative to the length of the fiber) towards the tissue where imaging and / or light irradiation are needed. The latter can be seen as a prism and lens integrated into a single device, where an angle-polished end face redirects light coming from the fiber to the lens (often at 90 degrees), and the lens focuses the light into the tissue. For imaging, scattered light from the tissue is collected by the same lens and redirected back towards the fiber via the angle-polished end face. The fiber then sends this light to a post-processing system (often an interference arm or detector) to process and form an image. The endoscopic catheter (including the fiber and other optical components attached to it) is moved back and forth and rotated along its axis (e.g., around the longitudinal axis running the length of the fiber) to reconstruct a 3D image of the scene (e.g., tissue). [Overview of the Initiative] [Problems that the invention aims to solve] 【0003】 The present invention provides a device for dynamically controlling the propagation direction and shape of light (e.g., focusing, beam width expansion / contraction, coupled input to a substrate, and coupled output from a substrate) and for classifying light based on its characteristics (e.g., polarization, angle, and light / or wavelength). [Means for solving the problem] 【0004】 Summary of Disclosure This abstract is provided to introduce the selection of embodiments in a simplified form. The embodiments will be described in more detail in the following detailed description. This abstract is not intended to identify any major or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 【0005】 According to some embodiments, devices are disclosed for dynamically controlling the propagation direction and shape of light (e.g., focusing, beam width expansion / contraction, coupled input to a substrate, and coupled output from a substrate) and for segmenting light based on its characteristics (e.g., polarization, angle, and light / or wavelength). 【0006】 In one embodiment, an optical system is disclosed. The optical system includes a substrate having a first surface and a second surface, and a first reflector disposed on the substrate and configured to receive light. The light includes at least one of a first wavelength and a second wavelength. The first reflector is configured to reflect the first wavelength of light toward a first diffracting lens and transmit the second wavelength of light toward a second reflector along a first optical path. The second reflector is configured to reflect the second wavelength of light toward a second diffracting lens along a second optical path. 【0007】 In another embodiment, an optical system is disclosed comprising a substrate having a first surface and a second surface, and a collimator configured to receive and collimate input light. The input light includes at least one of a first wavelength and a second wavelength. The first reflector is configured to reflect the first wavelength light toward a first diffracting lens and to transmit the second wavelength light toward a second reflector. The second reflector is configured to reflect the second wavelength light toward a second diffracting lens. 【0008】 Most embodiments include a light source, optical fiber, diffractive optical components (e.g., diffractive lenses, diffraction gratings, metasurface-based lenses, metasurface-based gratings), refractive optical elements (e.g., mirrors, wavelength-selective mirrors, partial mirrors, substrates), and / or liquid crystal (LC), thin films, and polarizing films (e.g., polarizing reflectors, absorbing polarizers, half-wave plates, quarter-wave plates) to control, shape, segment, and guide light in a desired direction for imaging and / or illumination, and ultimately focus the light onto a target. Furthermore, embodiments may include at least one light source, at least one sensor, and at least one control module. The control module may control, adjust, and adjust the function of each component in response to feedback from the sensor or user. The function of some components may be automatically changed by applying voltage and / or current or by changing the characteristics of the incoming light (polarization, wavelength, angle, etc.). The polarization state of the light may be linear, circular, elliptical, random, unpolarized, or any combination thereof. 【0009】 The methods disclosed herein may include the step of receiving feedback data from at least one sensor or image processing software using a communication device or sensor. Using this feedback, a control module may adjust the function of one or more components and / or modify the wavelength, polarization, or other characteristics of the input light in order to improve or adjust the performance of the system / instrument for imaging and / or illumination. 【0010】 Both the above summary and the following detailed description are for illustrative purposes only and provide examples. Therefore, the above summary and the following detailed description should not be considered limiting. Further features or variations may be provided in addition to those described herein. For example, embodiments may be directed to various combinations and subcombinations of features, as described in the detailed description. 【0011】 The accompanying drawings presented herein constitute part of this disclosure and illustrate different embodiments. The incorporated drawings may include various copyright and trademark representations owned by the applicant. All rights to the various trademarks and copyrights shown herein belong to and are the property of the applicant. The applicant reserves and reserves all rights to the trademarks and copyrights contained herein and permits the reproduction of the subject matter only in connection with the reproduction of the granted patent and not for any other purpose. 【0012】 Furthermore, the drawings may include descriptive and / or texts describing specific embodiments of the present disclosure. These texts and descriptives are included for non-limiting, descriptive, and illustrative purposes of the specific embodiments described herein. [Brief explanation of the drawing] 【0013】 [Figure 1A] This figure shows an embodiment of a small form factor endoscopic fiber-based imaging and irradiation system. [Figure 1B] This figure shows an embodiment of a small form factor endoscopic fiber-based imaging and irradiation system. [Figure 1C] This figure shows an embodiment of a small form factor endoscopic fiber-based imaging and irradiation system. [Figure 1D] This figure shows an embodiment of a small form factor endoscopic fiber-based imaging and irradiation system. [Figure 2A] This figure shows an embodiment of multispectral and multizoom imaging using cascaded wavelength-selective reflectors. [Figure 2B] This figure shows an embodiment of multispectral and multizoom imaging using cascaded wavelength-selective reflectors. [Figure 3A] This figure shows embodiments of multispectral and multizoom imaging and irradiation utilizing the dispersion response of a diffraction grating. [Figure 3B] FIG. showing embodiments of multi-spectrum and multi-zone imaging and irradiation using the diffraction grating dispersion response. [Figure 4A] FIG. showing an embodiment of a miniaturized polarization splitting imaging and irradiation system. [Figure 4B] FIG. showing an embodiment of a miniaturized polarization splitting imaging and irradiation system. [Figure 4C] FIG. showing an embodiment of a miniaturized polarization splitting imaging and irradiation system. [Figure 4D] FIG. showing an embodiment of a miniaturized polarization splitting imaging and irradiation system. [Figure 4E] FIG. showing an embodiment of a miniaturized polarization splitting imaging and irradiation system. [Figure 5A] FIG. showing embodiments of multifunctional optical imaging and irradiation. [Figure 5B] FIG. showing embodiments of multifunctional optical imaging and irradiation. [Figure 5C] FIG. showing embodiments of multifunctional optical imaging and irradiation. [Figure 5D] FIG. showing embodiments of multifunctional optical imaging and irradiation. [Figure 6A] FIG. showing an embodiment configured to extend the depth of focus of an optical imaging and irradiation system (OIIS). [Figure 6B] FIG. showing an embodiment configured to extend the depth of focus of an optical imaging and irradiation system (OIIS). [Figure 6C] FIG. showing an embodiment configured to extend the depth of focus of an optical imaging and irradiation system (OIIS). [Figure 7A] FIG. showing an embodiment of an optical imaging and irradiation system with a reconfigurable focal length. [Figure 7B] FIG. showing an embodiment of an optical imaging and irradiation system with a reconfigurable focal length. [Figure 7C]This figure shows an embodiment of an optical imaging and illumination system with a resettable focal length. [Figure 8A] This is an exploded view of one embodiment of an optical imaging and irradiation system, illustrating different integration schemes with various components. [Figure 8B] This is a cross-sectional view of one embodiment of an optical imaging and illumination system, illustrating different integration schemes with various components. [Figure 9] This is a block diagram of various modules for implementing the technology disclosed herein. [Modes for carrying out the invention] 【0014】 Detailed explanation Embodiments of the present invention are described in further detail below with reference to the accompanying drawings, but alternative configurations and embodiments are also possible without departing from the scope of this application. Therefore, this application should not be construed as being limited to the embodiments described herein. Rather, the illustrated and described embodiments are provided as examples to convey the scope of the invention to those skilled in the art. In the drawings, the sizes of layers and regions and their relative sizes may be exaggerated for clarity. 【0015】 The terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or sections, but it will be understood that these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Accordingly, the first element, component, region, layer, or section described below may be referred to as the second element, component, region, layer, or section without departing from the teachings of this disclosure. 【0016】 Where used herein, the singular forms “a,” “an,” and “the” are intended to include the plural form unless the context clearly indicates otherwise. Furthermore, where used herein, the terms “include” and / or “contain” identify the presence of the described feature, complete, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, complete, step, operation, element, component, and / or group thereof. Where used herein, the terms “and / or” include any and all combinations of one or more related enumerated items, and may be abbreviated as “ / .” 【0017】 Throughout this disclosure, the term “any” may be used herein to describe any particular component, or any material, shape, size, feature, sequence, type or kind, orientation, position, quantity, component, and arrangement of components, including single and / or combinations of components, that may enable any particular component / system within the present invention to satisfy the object, function, and intent of this disclosure or the present invention. 【0018】 Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as they are generally understood by those skilled in the art to the extent of this disclosure. Furthermore, it will be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and / or this specification, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein. 【0019】 Firstly, the conventional optical illumination and imaging systems described above have various drawbacks. For example, systems that rely on GRINs and ball lenses suffer from significant optical aberrations, including spherical and astigmatism, which degrade imaging resolution. While one could mitigate these aberrations by cascading multiple lenses, similar to the objective lenses of a microscope, the large size and high cost of systems with multiple lenses make this approach expensive and impractical. 【0020】 In addition to low resolution, refractive-based lenses (such as spherical lenses) have limited functionality. They cannot perform polarization-resolved imaging or multispectral imaging, and their focal lengths are fixed (i.e., cannot be adjusted or changed). Furthermore, these lenses must be cascaded with other large optical components, such as prisms, to perform imaging in the radial direction (e.g., perpendicular to the fiber length in fiber-based endoscopes), which hinders further miniaturization of the imaging system. Since most fiber-based endoscope designs are based on finite / finite conjugate designs (point-to-point focusing and imaging from the fiber core to the focal spot, or vice versa), optical path errors between the fiber and lens (e.g., due to manufacturing tolerances) can cause aberrations, reducing resolution and potentially altering the effective focal length of the imaging system. Using prisms, due to their solid nature, makes it extremely difficult to place any other components between the fiber and lens, thereby limiting the functionality of the entire system. For example, controlling or segmenting light transmitted between a fiber and a lens through a prism, based on its polarization and / or wavelength, can be extremely difficult. Furthermore, both refractive lenses and prisms are passive optical components without adjustment capabilities, which prevents the optical system from being tuned and dynamically operated. This disclosure describes several systems and methods that address these problems and drawbacks. 【0021】 This disclosure describes compact and small form factor instruments, apparatus, and systems that facilitate optical control for imaging and illumination. Furthermore, this disclosure describes various methods that enable multi-zoom imaging, multispectral imaging, and polarization-resolved imaging. In addition, this disclosure relates generally to multifunctional small form factor optical systems that focus light onto tissues / organs for imaging and illumination via optical fibers and overlapping miniaturized optical components and instruments. Optical components and instruments may be based on diffractive optical systems, metasurfaces, and refractive optical systems, and / or combinations thereof. 【0022】 In this disclosure, diffraction components (e.g., gratings, lenses) include any array of subwavelength scatterers, resonators, and / or nanostructures. These scatterers, resonators, and / or nanostructures may be referred to herein as building blocks. Building blocks can simultaneously control one or more fundamental properties of light, individually or collectively, such as phase, amplitude, polarization, spatial and temporal profiles, propagation direction, ray angle, or combinations thereof. For example, a diffraction lens is a very thin lens that can focus, diverge, or concentrate incoming light. Incident light can have any profile and / or angular distribution. Generally, diffraction gratings diffract incoming light to one or more different orders (e.g., ±1, ±2, ±3, etc.) depending on the design parameters of the grating (e.g., pitch and / or pattern). Diffraction axicons can produce Bessel beams of various orders (e.g., J0, J1, etc.). Bessel beams have unique non-diffractive properties, allowing light to be focused and remain at extended distances compared to other similar products such as diffractive lenses. The building blocks of diffractive components can be made from materials including semiconductors (e.g., amorphous silicon, polycrystalline silicon, silicon carbide, gallium nitride, gallium phosphide), crystals (e.g., silicon, lithium niobate, diamond), dielectrics (e.g., silicon dioxide, silicon nitride, aluminum oxide, hafnium oxide, titanium dioxide, indium oxide), polymers (e.g., photoresists, PMMA), metals (e.g., silver, aluminum, gold), two-dimensional (2D) materials (e.g., graphene, boron nitride), phase change materials (e.g., chalcogenides, vanadium dioxide), or any mixtures or alloys thereof. 【0023】 In this disclosure, metasurfaces are advanced forms of diffraction components and may be referred to as metagratings (gritzes based on metasurface designs), metalenses (lenses based on metasurface designs), and metaholograms (holograms based on metasurfaces). These metasurfaces are designed, multifunctional, planar components with dispersion, polarization, and angular response, and may be fabricated using a variety of approaches, including photolithography, deep ultraviolet lithography, electron beam lithography, nanoimprinting, reactive ion etching, electron beam deposition, sputtering, plasma deposition, atomic layer deposition, and any combination of the aforementioned processes in any order. The building blocks of metasurfaces may be fabricated from materials similar to those described above for diffraction components. 【0024】 Throughout this disclosure, the term "optical fiber," which may also be simply referred to as "fiber" in this specification, may refer to a flexible, transparent fiber made by stretching glass (silica), plastic, or other material. Optical fibers as referred to herein may include single-mode fibers, multimode fibers, photonic crystal fibers, and any other fiber for a particular purpose. Fibers may be connected to bare ferrules or to connectors containing ferrules. The type of ferrule may be a ferrule connector (FC), a lucent connector, an angle-polished connector (APC), a physical contact (PC) connector, an ultra-physical contact (UPC), or any combination thereof. Other connectors may be used without departing from the scope of this disclosure. Ferrules may be made of glass, ceramic, plastic, or any other material. Fiber connectors may be FC, PC, APC, a subscriber connector (SC), or any combination thereof. Ferrules may be customized to any shape and size. The working wavelength of the fiber may be ultraviolet (UV), visible, near-infrared (NIR), short-wave infrared (SWIR), and / or longer or shorter wavelengths. The fiber may have a protective layer and may be surrounded by other plastic tubes, polymer tubes, glass tubes, and / or torque coils. Generally, various types of tubes (e.g., plastic, polymer, glass) are used as protective housings for optical systems and devices. Torque coils are used to transmit torque to the optical system (e.g., imaging / irradiation probe) for rotation, and thus perform radiative imaging / irradiation. 【0025】 In this disclosure, the term “light source” refers to coherent, partially coherent, or incoherent light sources that may be based on any technology, including but not limited to sweep-source lasers, light-emitting diodes (LEDs), end-emitting semiconductor laser diodes, vertical-cavity surface-emitting lasers (VCSELs), supercontinuum light sources, superluminescent diodes, white light sources, and halogen lamps. The wavelength of the light source may be in the range of deep ultraviolet, ultraviolet, visible, NIR, SWIR, mid-infrared, or far-infrared, depending on the catheter application (for example, the wavelength may differ for imaging or therapeutic applications). The light may be delivered as pulses of energy (e.g., pulsed lasers) or as continuous waves (CW). 【0026】 Throughout this disclosure, the term “color filter” refers to a device that selectively transmits or reflects light of different colors (i.e., wavelengths). Color filters may be based on a variety of mechanisms, such as absorption (e.g., using dyes, pigments, plasmonic particles, and metal nanostructures), interference (e.g., thin films, subwavelength diffraction gratings, Mie resonant structures, plasmonics, and metal nanostructures), and diffraction (e.g., reflective or transmissive diffraction gratings). In this disclosure, “mirror” may refer to a device that reflects incident light. The reflectivity of a mirror may be less than or greater than 10%, less than or greater than 25%, less than or greater than 75%, or less than 100%. The reflectivity of a mirror may be a function of the wavelength, polarization, and / or angle of incidence of the light. 【0027】 Throughout this disclosure, imaging sensors may refer to any imaging and sensing techniques for detecting or capturing light intensity, or other optical properties such as phase, angle, polarization, and wavelength. Some examples of such any imaging and sensing techniques include complementary symmetric metal oxide semiconductors (CMOS), charge-coupled devices (CCDs), intensified charge-coupled devices (ICCDs), scientific research CMOS (sCMOS), avalanche diodes (ADs), time-of-flight (ToF), Schottky diodes, or any other optical or electromagnetic sensing mechanisms operating at deep ultraviolet, visible, SWIR, NIR, far-infrared, and / or other wavelengths. 【0028】 Furthermore, this disclosure describes hybrid approaches based on refractive optics, diffractive optics, metasurfaces, and other planar optical techniques (e.g., polarizers, waveplates, quarter-waveplates, half-waveplates, mirrors, reflectors, partial reflectors, and color filters). The dynamic capabilities of the various optical systems described herein may be enabled by including components configured to achieve electro-optic effects (e.g., by carrier injection) or thermo-optic effects (e.g., by local heating). Other mechanisms and instruments, such as LCs, may also be used to provide tunability within the optical system. Dynamic capabilities can significantly improve the performance and flexibility of the optical system. The versatility of cascaded planar components allows such dynamic systems to meet the small form factor required for in vivo medical applications. The primary focus of this disclosure is to enable small-form-factor, reconfigurable, high-performance optical systems for medical imaging, diagnostic, and therapeutic purposes. 【0029】 Throughout this disclosure, the term "dynamic component," or "design," or the adjective "dynamic" as used herein, may refer to a component or design having functions, performance, and characteristics that can be tuned over time by selectively changing the properties of light (e.g., polarization, wavelength, intensity) in response to one or more external light, heat, electricity, or mechanical signals. 【0030】 The simulations in this disclosure are performed using ray tracing methods that take into account the laws of reflection, refraction, and diffraction. For all simulations described and illustrated herein, each ray is assumed, for simplicity, to have a single wavelength with a very narrow bandwidth. It is important to note that in experiments and actual equipment, a ray (e.g., input light) can have a considerable bandwidth of less or greater than 10 nm, less or greater than 25 nm, less or greater than 50 nm, or less or greater than 100 nm. In some embodiments, the bandwidth is between about 50 nm and about 100 nm. 【0031】 Figure 1A (top) shows a schematic diagram of an endoscopic catheter 150, including a fiber connector 152, an optical fiber 102, a torque coil 154 (for transmitting torque from one end of the catheter to the other), and other optical and mechanical components enclosed by a sheath 156. A magnified view of the bottom of Figure 1A shows the components at the distal end of the endoscopic catheter, including the torque coil 154 connected to an optical imaging and irradiation system (OIIS) 101 via a ferrule 158. The ferrule 158 holds the end of the fiber 102. The fiber 102 passes through the torque coil 154 and connects to the fiber connector 152 at the other end of the endoscopic catheter 150 (see top of Figure 1A). The torque coil 154, ferrule 158, and OIIS 101 are enclosed by a sheath 156. The sheath 156 may be made of clear plastic, polymer, glass tubing, or a combination thereof. The end of the sheath 156 can be sealed by an enclosure cap 157 (e.g., a plastic or glass substrate, silicone gel, etc.). 【0032】 Figure 1B shows a perspective view of one end embodiment of a small form factor endoscopic catheter 100. In this embodiment, the fiber 102 includes a core 103 configured to receive light from a light source (not shown). In some embodiments, the fiber 102 may be connected to a ferrule (see Figure 1A). The fiber 102 transmits light to the OIIS 101. In some embodiments, the OIIS may have dimensions ranging from about 0.2–1.5 mm in the z dimension, about 0.2–1.5 mm in the y dimension, and about 1–5 mm in the x dimension. In some applications, the size constraint in the x dimension may be looser than the size constraints in the y and z dimensions. 【0033】 In the endoscopic catheter 100, the OIIS 101 includes two wavelength-selective reflectors (WSRs) 104a and 104b, two diffraction gratings 106a and 106b, and two diffraction lenses 107a and 107b, which are located on or within the substrate 105, or supported by the substrate 105. The substrate 105 may be made of materials including glass (e.g., fused silica, Pyrex®, high refractive index glass, quartz), semiconductors (e.g., amorphous silicon, polycrystalline silicon, silicon carbide, gallium nitride, gallium phosphide), crystals (e.g., sapphire silicon, lithium niobate, diamond), dielectrics (e.g., silicon dioxide, silicon nitride, aluminum oxide, hafnium oxide, titanium dioxide, indium oxide), and polymers (e.g., photoresist, PMMA). Herein, for illustrative purposes, a glass substrate is considered. One or more of the diffractive lenses 107a and 107b can be replaced with Fresnel lenses, metasurface-based lenses, and / or refractive lenses (e.g., spherical lenses, aspherical lenses, free-form lenses). WSRs 104a and 104b can be positioned on the first surface 105a. The WSRs can be positioned at a certain angle (e.g., about 37 degrees, 45 degrees, or 50 degrees) with respect to the first surface 105a. The reflectance of the WSRs for a desired wavelength can be less than or greater than 95%, less than or greater than 90%, less than or greater than 80%, or less than or greater than 70%, while allowing other wavelengths to pass through at a maximum transmittance of less than or greater than 95%, less than or greater than 90%, less than or greater than 80%, or less than or greater than 70%. In some embodiments, the reflectance of the WSR for a desired wavelength may be between about 80% and about 95%. In some embodiments, the transmittance of the WSR for a desired wavelength may be between about 80% and about 95%. The first diffraction lens 107a may also be located on the first surface 105a between the two WSRs 104a and 104b. The two diffraction gratings 106a and 106b, as well as the second diffraction lens 107b, may be located on the second surface 105b opposite the first surface 105a of the substrate.The first surface 105a and the second surface 105b may be substantially parallel or may be at an angle to each other. This angle may be less than or greater than 5 degrees, and less than or greater than 10 degrees. The first surface 105a and the second surface 105b may be planar and substantially parallel to each other. The position, size, and shape of each component on the substrate 105 may be selected to receive and direct light in a particular manner, as will be described below herein with respect to Figures 1B-1C. 【0034】 For applications where the endoscopic catheter 100 is used for optical coherence tomography, the working wavelength (i.e., the wavelength of light received by the OIIS) may be in the NIR or SWIR region (e.g., wavelengths between 800 nm and 1700 nm). Such wavelengths advantageously allow light penetration into tissue for depth imaging and illumination. For systems using wavelengths in the range of approximately 800 nm to approximately 1700 nm, the diffractive lens may include an array of silicon nanostructures on a glass substrate. Silicon has a high refractive index (e.g., refractive index n > 3) and negligible material loss in this wavelength range. Therefore, silicon nanostructures on a glass substrate can enable low-loss and strong photo-nanostructure interactions necessary for manufacturing highly efficient and high-performance flat devices and components. 【0035】 Figures 1C and 1D show side views of the endoscopic catheter 100 operating in different ways, where the operating method is a function of the input light. Figure 1C shows the operation of the endoscopic catheter 100 using input light with a wavelength of approximately 1300 nm (i.e., ray 108a), while Figure 1D shows the operation of the endoscopic catheter 100 using input light with a wavelength of approximately 800 nm (i.e., ray 108b). While rays 108a and 108b can be delivered to the endoscopic catheter 100 simultaneously, for simplification, the ray tracing simulation is divided into two figures. The first and second wavelengths of 1300 nm and 800 nm are used as examples, but other wavelengths of light may be selected without departing from the scope of this disclosure. 【0036】 In the ray tracing simulation shown in Figure 1C, a ray 108a with a wavelength of 1300 nm exits the fiber end face 102, travels toward WSR 104a, and collides with WSR 104a. WSR 104a is tilted at approximately 45 degrees with respect to the direction of propagation of ray 108a. WSR 104a is designed (as shown in Figure 1D) to reflect ray 108a with a wavelength centered on 1300 nm and allow ray 108b with a wavelength centered on 800 nm to pass through unobstructed. Thus, ray 108a collides with the first WSR 104a and is reflected toward the substrate 105 by the first WSR 104a. The operating bandwidth of the WSR(104a, 104b) can be adjusted according to the design parameters. For example, the operating bandwidth may be less than or greater than 10 nm, less than or greater than 25 nm, less than or greater than 50 nm, or less than or greater than 100 nm. In some embodiments, the bandwidth may be between approximately 50 nm and approximately 100 nm. 【0037】 The light ray 108a reflected by WSR104a enters the substrate 105 substantially perpendicular to the first surface 105a. The light ray 108a travels through the substrate 105 toward the second surface 105b where the diffraction grating 106a is located. The diffraction grating 106a is sized and positioned to block the light ray 108a, taking into account any small amount of light divergence that may occur. The diffraction grating 106a diffracts the light ray 108a at an angle greater than the total internal reflection (TIR) ​​angle of the substrate. The diffracted light bounces off the first surface 105a due to TIR and is directed toward the second diffraction grating 106b located on the second surface 105b. The second diffraction grating 106b is designed to diffract the light after the diffraction event so that it passes through the substrate 105 at an angle substantially perpendicular to the first surface 105a and the second surface 105b. The diffractive lens 107a is positioned on the first surface 105a and receives light diffracted from the second diffraction grating 106b. The diffractive lens 107a may be sized to account for the increase in divergence of the ray 108a as it passes through the optical system. The diffractive lens 107a focuses the ray 108a to a diffraction-limited spot at a focal length (e.g., f1 = 0.9 mm) relative to the first surface 105a of the substrate 105. Here, the focal length of 0.9 mm is chosen for illustrative purposes, and the focal length may be less than or greater than 1 mm, less than or greater than 5 mm, or less than or greater than 10 mm, without departing from the scope of the present disclosure. 【0038】 Referring to Figure 1D, a second method of operation of the endoscopic catheter 100 is shown using an input ray 108b having a wavelength of 800 nm. As described above, the ray 108b passes through the WSR 104a without obstruction until it encounters the second WSR 104b. The second WSR 104b is designed to reflect light centered at 800 nm, and therefore the ray 108b is reflected toward the substrate by the second WSR 104b. The ray 108b passes through the substrate 105 toward the second diffracting lens 107b, which is located on the second surface 105b and configured to receive the reflected ray 108b. The ray 108b will be focused by the diffracting lens 107b toward the second surface 105b of the substrate 105 at a second focal length (f2 = 0.5 mm). Thus, by utilizing reflectors (WSR104a and 104b) that reflect only light of a specific bandwidth, an OIIS with a focal length adjustable according to the wavelength of the input light is described. Here, the endoscopic catheter 100 may be surrounded by a protective tube / sheath made of glass, polymer, or plastic. In this case, the diffractive lenses 107a and 107b may be designed to take into account the optical path added by the protective tube / sheath. 【0039】 In particular, diffractive lenses can have chromatic aberration, and changes in the wavelength of the input light can result in the focal size becoming larger than the diffraction limit, leading to a decrease in focusing efficiency. However, in catheter 100, each of the diffractive lenses 107a and 107b can be designed for a specific working wavelength (e.g., 1300 nm and 800 nm, respectively). This allows each diffractive lens to achieve optimal performance in terms of imaging resolution and focusing efficiency. Another important point regarding the endoscopic catheter 100 is that the light exiting the fiber end face 102 diverges. The beam waist can also be controlled by controlling the optical path length the light travels before reaching the diffractive lens. The longer the light travels, the larger the beam waist. Therefore, for a fixed focal length (or working distance of the lens), assuming the beam waist is equal to the diameter of the lens used to focus the light, the numerical aperture (NA) of the OIIS can also be controlled. Another advantage of having two focal points (upper and lower of the OIIS) is that it improves imaging speed and frame rate. Generally, the OIIS rotates along the fiber axis (X direction) to perform 3D imaging. With upper and lower focal points, one can perform full radial imaging by rotating the OIIS 180 degrees (instead of 360 degrees). In other words, the upper lens 107a forms an image of the upper semicircle, and the lower lens 107b forms an image of the lower semicircle. By combining these two images using, for example, image post-processing software, one can reconstruct a complete image by simply rotating the OIIS 101 180 degrees, thereby increasing the imaging speed. In another scenario where the OIIS 101 rotates 360 degrees, the frame rate can be doubled by combining the images captured by the upper lens 107a and the lower lens 107b. 【0040】 As described above, in addition to imaging the ambient environment using OIIS101, the same OIIS101 can be used to irradiate the ambient environment (e.g., for therapeutic purposes). Therapeutic protocols may require the use of light with multiple different wavelengths, for example, light with wavelengths in the UV or visible light wavelength range. Depending on the specific wavelength used, other materials such as titanium dioxide or hafnium dioxide (with negligible absorption loss in these wavelength ranges and a relatively high refractive index of n = ~2.5) may be used to form one or more components, such as diffraction gratings or diffraction lenses. Titanium dioxide or hafnium dioxide components may be more suitable for assembly on different types of substrates, depending on the operating wavelength. 【0041】 Figures 2A and 2B illustrate embodiments of multispectral and multizoom imaging using a multi-stage wavelength-selective reflector. 【0042】 The number of spectral channels and the achievable focal lengths can be increased by arranging more WSRs and other components at equal intervals along the X direction, as shown in Figures 2A-2B. In particular, the inner diameter of the tubular organ (e.g., the organ being imaged or irradiated) sets a limit on the size of the OIIS along the radial direction (i.e., along the Z and Y directions). However, this size limit is more relaxed along the axial direction (X direction). The radial and axial directions are defined with respect to the length of the fiber, shown as fiber 202. In practice, fiber 202 can extend along the X direction to lengths of several centimeters or even several meters. Fiber 202 shown in Figure 2A guides four spectral channels, for example, centered on the first, second, third, and fourth wavelengths. In some embodiments, the first, second, third, and fourth wavelengths may be 900 nm, 1100 nm, 1300 nm, and 1500 nm, respectively. The first, second, third, and fourth spectral channels are called rays 208a, 208b, 208c, and 208d, respectively. All of these rays diverge after exiting the end face of fiber 202, regardless of their wavelength. In the ray tracing simulations shown in Figures 2A-2B, for simplicity, only rays with wavelengths equal to the center wavelength of each spectral channel are shown. 【0043】 A metasurface design or an achromatic refractive lens may be used to collimate all different wavelengths of light rays 208a–208d. After collimation by the achromatic lens 210, the light rays 208a–208d encounter a series of wavelength-selective reflectors positioned at an angle (e.g., about 45 degrees) to the first surface 205a of the substrate 205. Each WSR may be configured to reflect or transmit light associated with different wavelengths. After collimation by the achromatic lens 210, the light rays 208a–208d encounter a first WSR 204a. The WSR 204a is designed to reflect the light rays 208a through the substrate 205 towards a first diffracting lens 207a, which may be positioned on a second surface 205b opposite the first surface 205a. The first diffracting lens 207a focuses the light rays 208a to a first focal length. For example, the first focal length may be approximately 0.5 mm. The other three spectral channels (i.e., the second, third, and fourth rays 208b-208d) pass through WSR204a and continue unimpeded toward the second WSR204b. 【0044】 WSR204b is designed to reflect the ray 208b through the substrate 205 toward the second diffracting lens 207b, which focuses it to a second focal length (e.g., about 1 mm). WSR204b allows the rays 208c-208d to pass toward WSR204c without obstruction. WSR204c is configured to reflect the ray 208c, centered on the third wavelength, toward the third diffracting lens 207c. The ray 208c is focused by the corresponding diffracting lens 207c to a third focal length (e.g., about 1.5 mm). WSR204c allows the ray 208d to pass toward without obstruction. Finally, the ray 208d, corresponding to the fourth spectral channel, reaches the mirror 209 and is directed toward the diffraction grating 206a. In some embodiments, a fourth WSR configured to reflect the light ray 208d may be used instead of a mirror. 【0045】 The light ray 208d is diffracted by the first diffraction grating 206a, and the diffracted light ray 208d travels at an angle larger than the TIR of the substrate, and therefore the light ray 208d is reflected inside the substrate when it encounters the first surface 205a of the substrate 205. The light ray 208d traveling at the TIR encounters the second diffraction grating 206b, which diffracts the light ray 208d again. Specifically, the diffraction grating 206b diffracts the light ray 208d toward the diffraction lens 207d so that it can be focused to a fourth focal length (e.g., about 2 mm). 【0046】 The use of gratings (e.g., diffraction gratings 206a and 206b) provides a special degree of freedom in directing and shaping light in a small form factor. For example, using two diffraction gratings, ray 208d can be focused from the top of the substrate (i.e., the first surface 205a), while the other rays (i.e., rays 208a-208c) can all be focused from the bottom of the substrate (i.e., the second surface 205b). In the embodiment shown in Figure 2A, it is illustrated that by arranging three WSRs and one mirror at equal intervals, a small OIIS 201a (e.g., an OIIS with sub-millimeter dimensions along both the Y and Z directions) can emit light at four different focal lengths. This OIIS 201a can be used in one spectral range at a time (e.g., by using a single spectral channel of input light) or in a combination of spectral channels at a time (e.g., by using multiple input light) to control the focal length. Performing imaging with four spectral channels not only improves resolution at each depth (e.g., focal length) but also enables multispectral imaging by superimposing images from each spectral channel using image post-processing techniques. When the OIIS201a is used for optical coherence tomography, the depth of image can far exceed the focal length of each diffracting lens, and the depths of focus of each lens can be designed to overlap across the entire spectral range to perform multispectral imaging. Furthermore, the number of WSRs and spectral channels can be increased to further expand the spectral range and to achieve a number of achievable focal lengths. For example, without departing from the scope of this disclosure, five, six, or more spectral ranges, and associated WSRs and diffracting lenses can be incorporated into the OIIS system. 【0047】 Figure 2B shows a similar concept to that shown in Figure 2A, with the same spectral channels and focal length, but with subtle differences. In OIIS201b, the achromatic lens (210 in Figure 2A) is replaced by a diffracting lens 207e designed for a fourth wavelength (e.g., 1500 nm). Thus, as is evident from the ray tracing simulation, after passing through the diffracting lens 207e, only rays centered on the fourth wavelength will be perfectly collimated. Other rays (e.g., at the first, second, and third wavelengths) will diverge slightly due to the intrinsic chromatic aberration of the diffracting lens 207e. In the case of a diffracting lens, the shorter the working wavelength, the greater the difference between the working wavelength and the design wavelength (e.g., 1500 nm), and therefore the larger the divergence angle. Thus, the ray 208a with the shortest wavelength (e.g., 900 nm) will have the largest divergence angle compared to the other rays with longer wavelengths. These divergent rays may require minor modifications to the design of the diffractive lenses 207a, 207b, and 207c (i.e., necessary phase maps) to ensure that the divergent rays are focused to the diffraction-limited spot. These changes can be determined by calculating the new phase maps for the diffractive lenses using ray tracing or other available optical methods. 【0048】 Figures 3A and 3B illustrate embodiments of multispectral and multizoom imaging and irradiation utilizing the dispersion response of a diffraction grating. 【0049】 Figure 3A shows an embodiment of an endoscopic catheter 300a equipped with a multispectral multizoom OIIS 301a. In catheter 300a, fiber 302 transmits three spectral channels to the OIIS 301a, each having a first, second, and third central wavelength (e.g., a first wavelength of 1000 nm, a second wavelength of 1300 nm, and a third wavelength of 1400 nm). Ray 308a refers to the combination of all three spectral channels. Ray 308a begins to diverge as it exits fiber 302, but is collimated by the diffractive lens 307a. A mirror 309, which may be positioned at an angle (e.g., about 45 degrees) to the upper surface 305a of the substrate 305, reflects ray 308a and redirects it toward the substrate 305. The ray 308a travels through the substrate 305 at an angle that can be substantially perpendicular to the first and second surfaces 305a, 305b of the substrate. The ray 308a encounters a first diffraction grating 306a that diffracts the ray to an angle greater than the TIR threshold of the substrate 305, and the ray is coupled entirely within the substrate. It is worth noting that when the angle of the ray is greater than the TIR of the substrate, the substrate acts as a waveguide, and the ray can propagate through its interior until it is uncoupled by another diffraction grating or any other suitable component. 【0050】 The diffraction grating 306a diffracts and spatially separates rays of different wavelengths, as shown in Figure 3A. As described above, ray 308a contains three rays of different wavelengths, each diffracted by grating 306a at a different angle. Ray 308b, having the shortest wavelength (e.g., 1000 nm), will be diffracted to the steepest TIR angle and directed towards the second diffraction grating 306b. The diffraction grating 306b on the first surface of the substrate is configured to diffract ray 308b toward diffraction lens 307b, where the light is focused to a first focal length (e.g., 0.6 mm). The other two spectral channels (i.e., rays 308c and 308d) do not enter the diffraction grating 306b, but are instead reflected by the first surface 305a of the substrate. A ray 308c having a second wavelength greater than the first wavelength (e.g., a wavelength of 1300 nm) is received and diffracted by a third diffraction grating 306c on the second surface 305b of the substrate. The grating 306c diffracts the ray 308c toward the diffraction lens 307c, where it is focused at a second focal length (e.g., a focal length of 1.2 mm) on the first surface 305a of the substrate 305. A ray 308d having a third longest wavelength (e.g., a wavelength of 1400 nm) is received and diffracted by a fourth diffraction grating 306d. The diffraction grating 306d diffracts the ray 308d toward the diffraction lens 307d, where it is focused at a third focal length (e.g., a focal length of 2 mm). 【0051】 In the OIIS301a, input light (e.g., ray 308a) is spatially separated according to different spectral channels by utilizing the dispersion response of the diffraction grating 306a. Other parameters, such as the thickness of the substrate 305, can also be used as design variables when separating the different spectral channels. While the diffractive lens is described in relation to the OIIS301a, a refractive lens can be used instead of the diffractive lens without altering the function of the OIIS301a. 【0052】 The OIIS301a can perform imaging on the three spectral channels described, and the system's focal length can be controlled by changing the input wavelength. For example, multiplexed input light would pass through the system as described above, resulting in three light beams of different wavelengths that are focused to different focal lengths. Alternatively, if imaging is desired at only one of the available focal lengths, input light having a wavelength associated with that particular focal length can be provided to the OIIS301a. While three spectral channels and associated focal lengths are described, additional channels and focal lengths may be included in the OIIS without departing from the scope of this disclosure. 【0053】 Light projected by OIIS301a may be reflected or scattered by the surrounding environment (e.g., organs or tissues). At least a portion of the reflected or scattered light may be captured by OIIS301a through the same optical path used to project the light into the surrounding environment, but in the opposite direction. For example, reflected light having a first spectral channel may be captured by diffracting lens 307b, diffracted by diffraction gratings 306b and 306a, reflected by mirror 309, shaped (e.g., focused) by diffracting lens 307a, and coupled to fiber 302 for reverse transmission to an imaging system (not shown). Reflected light having second and third spectral channels may follow a similar pattern, so that the light travels through the optical path toward the fiber for image acquisition. Such light capture capabilities are shared by all embodiments disclosed herein. 【0054】 Another OIIS301b with similar functionality is shown in Figure 3B, where the diffraction grating 306b (shown in Figure 3A) is replaced by a wavelength-selective grating (WSG) 311. In the endoscopic catheter 300b, the spatial separation between three different spectral channels (e.g., a first spectral channel centered at 1200 nm, a second spectral channel centered at 1250 nm, and a third spectral channel centered at 1300 nm) is less than that shown in the system 300a described above, after the light has been diffracted by the diffraction grating 306a. The reduced spatial separation can be achieved by reducing the thickness of the substrate 305, adjusting the design of the diffraction grating 306a, and / or by providing three spectral channels whose wavelengths are closer together. All three spectral channels in the input light collide with the WSG 311. WSG311 diffracts only the first spectral range (e.g., ray 308a centered at 1200 nm), allowing other spectral channels to propagate unimpeded. Ray 308a collides with the diffracting lens 307a and is focused to a first focal length (e.g., a focal length of 0.6 mm). The second and third spectral channels (e.g., rays 308b and 308c, respectively) propagate through OIIS301b, similar to the second and third spectral channels described with respect to OIIS301a. Ray 308b collides with the diffraction grating 306b and is directed towards the diffracting lens 307b, where they are focused to a second focal length (e.g., a focal length of 1.2 mm). The light rays 308c collide with the diffraction grating 306c and are directed towards the diffraction lens 307c, where they are focused at a third focal length (for example, a focal length of 2 mm). 【0055】 While specific wavelengths and focal lengths are provided as examples for illustrative purposes, those skilled in the art will understand that other wavelengths and / or focal lengths may be selected without departing from the scope of this disclosure. 【0056】 Figures 4A–4E show five embodiments of a miniaturized polarization-resolved imaging and illumination system. 【0057】 The embodiments shown in Figures 1-3 were described in relation to their imaging capabilities. That is, each OIIS is described by tracking light from the end face of the fiber, through several components, and finally to the focal point. Each OIIS is a reciprocal system, meaning that the same system will collect light from the scene (in the case of medical imaging, the object to be imaged, such as tissue) and send it back to the fiber to be transmitted to an image processing module (not shown) for forming an image. 【0058】 In the ray tracing simulation shown in Figure 4A, the endoscopic catheter 400a with OIIS401a will be described starting from a point source positioned at the focal point of the diffractive lens 407a. One can understand this point source as a minute portion of tissue already illuminated by the same OIIS401a, now scattering light upward (i.e., towards 407a) and downward. The upward scattered ray, referred to as ray 408a, is collected by the diffractive lens 407a and then collimated toward the polarization-selective diffraction grating (PSG) 412. The polarization state of ray 408a can be decomposed into two orthogonal components: polarization #1 (P1) represented by ray 408b and polarization #2 (P2) represented by ray 408c. The PSG 412 diffracts the light in different directions based on its polarization (e.g., spatially separates it). For example, PSG412 diffracts a ray 408b with polarization P1 toward the diffraction grating 406a and a ray 408c with polarization P2 toward the diffraction grating 406b. The diffraction grating 406a diffracts the ray 408b, and the ray 408b is coupled out from the substrate 405 at an angle substantially perpendicular to the first and second surfaces 405a, 405b of the substrate. The ray 408b travels toward a polarization-selective reflector (PSR) 413a, which is oriented such that it reflects the ray 408b toward the fiber at a certain angle (for example, about 0 degrees toward the second surface 405b) (for example, about 45 degrees toward the first surface). Finally, the ray 408b is coupled to the first fiber 402a via a diffraction lens 407b, which focuses the ray 408b to the focal point at the end face of the fiber core in the first fiber 402a. 【0059】 The ray 408c takes a different path toward the second fiber 402b via the diffraction grating 406b, the second PSR 413b, and the diffraction lens 407c. The PSR 413b is oriented such that it reflects the ray 408c toward the fiber at a certain angle (e.g., about 0 degrees toward the second surface 405b) (e.g., about 45 degrees toward the second surface 405b). In some embodiments, the PSR 413b reflects only light with polarization P2 to prevent any stray light P1 from entering the P2 optical path in the fiber. To further reduce the possibility of any P1 polarization entering the P2 path, an absorbing polarizer 414b may be applied to the back of the PSR 413b. The absorbing polarizer ensures that if any polarization components other than the intended polarization are present, they will be absorbed and prevented from continuing to propagate through the system along the wrong path. A similar absorptive polarizer component 414a may be used on the PSR 413a to absorb stray P2 polarized light in the P1 polarized light path. The polarization direction of the absorptive polarizers is orthogonal to the corresponding PSR on which they are stacked. In some embodiments, the PSR 413b and the absorptive polarizer 414b may be replaced by a single metal mirror or dielectric mirror without departing from the scope of this disclosure. In some embodiments, the PSR 413a and the absorptive polarizer 414a may also be replaced by a single metal mirror or dielectric mirror. 【0060】 The OIIS401a spatially separates two orthogonal polarizations of light coming from the imaged object and sends them to two fibers that will ultimately be received by a processing module, which may include a camera or optical sensor (not shown here) to form an image, thus enabling polarization-resolved imaging. In some embodiments, the P1 and P2 polarizations of the light may be coupled to two different fiber cores within a single fiber. 【0061】 Another embodiment capable of polarization-resolved imaging is shown in Figure 4B. The endoscopic catheter 400b having the OIIS401b is a modified version of the embodiment shown in Figure 4A. The OIIS401b does not include one component (i.e., one diffraction grating such as the diffraction grating 406b from Figure 4A). The diffraction lens 407c of the OIIS401b receives scattered or reflected light from the object being imaged, and the received light contains both P1 and P2 polarization components. The light collides with the PSG412, where the first polarization (e.g., P1 polarization) is diffracted toward the diffraction grating 406 and follows the path described with respect to Figure 4. The PSG412 is configured such that light with a second polarization (e.g., P2 polarization) passes through the PSG412 without being diffracted, but rather without being obstructed. The P2 light then encounters the PSR413b and proceeds along a path similar to the path described with respect to Figure 4A. 【0062】 In addition to reducing the number of components on the OIIS401b, the number of components in the endoscopic catheter 400b can be reduced by replacing the two-fiber configuration used in 400a with a single fiber having two cores in 400b. The system can be further simplified by grouping the PSRs 413a, 413b and the absorptive polarizers 414a, 414b. This embodiment is shown in Figure 4C. 【0063】 Another alternative embodiment for polarization-resolved imaging is shown in Figure 4D. In an endoscopic catheter 400d with OIIS401d, the light rays collected by the diffractive lens 407c are separated by a PSR413a that reflects P1 polarization (i.e., ray 408a) and allows orthogonal polarization (i.e., P2, represented by ray 408b) to pass through. The reflected ray 408a is focused by the first diffractive lens 407a and coupled to the first core of the fiber 402. The PSR413b is configured to receive P2 polarization and reflect P2 polarization. Thus, the ray 408b is reflected by the second PSR413b toward the diffractive lens 407b and coupled to the second fiber core. To absorb any stray P1 polarization, an absorptive polarizer 414 may be included in the PSR413b. The light rays 408a and 408b travel along their respective fiber cores to the processing module for image processing. 【0064】 Another embodiment of polarization-resolved imaging is shown in Figure 4E. System 400e having OIIS401e includes first and second fibers 402a and 402b, disposed on first and second substrates 405c and 405d, respectively. In this embodiment, the light coupled out from fibers 402a and 402b is already polarized, for example, ray 408a may have P1 polarization and ray 408b may have P2 polarization. In an alternative embodiment, if the light emanating from fibers 402a and 402b is not polarized, one or more polarizer components (not shown) may be placed between the ends of each fiber 402a and 402b and the diffracting lenses 407a and 407b, and / or between the diffracting lenses 407a and 407b and the PSRs 413a and 413b, respectively. The light received by the first PSR413a may be of the first polarization (e.g., P1 polarization), and the light received by the second PSR413b may be of the second polarization (e.g., P2 polarization). 【0065】 The ray 408b, coupled and output from the second fiber 402b, is collimated by the diffraction lens 407b and reflected toward the diffraction grating 406b by the PSR 413b. As shown in the figure, an absorptive polarizer 414b may be included in the PSR 413b. The ray 408b is diffracted toward the PSG 412 by the diffraction gratings 406b and 406c. The PSG 412 allows the ray 408b (i.e., the ray with P2 polarization) to pass through unobstructed. The ray 408b is coupled with the ray 408a and focused by the diffraction lens 407c to a focal length (e.g., a focal length of 0.4 mm). The ray 408a, having orthogonal polarization to the ray 408b (e.g., P1 polarization), is coupled and output from the lower fiber 402a and collimated by the diffraction lens 407a. The light ray 408a is redirected toward the diffracting lens 407c via the PSR 413a, the diffraction grating 406a, and the PSG 412. The PSR 413a may include an absorptive polarizer 414a positioned therein. The PSG 412 is configured to diffract light having polarization P1, and thus the light ray 408a is diffracted by the PSG 412 toward the diffracting lens 407c, where it is focused at the focal length together with the light ray 408b. Due to the reciprocity of the system 400e when collecting light for imaging, each light ray scattered by the object being imaged is separated based on its polarization and coupled to the corresponding fiber core. The light collected in both fiber cores is sent to an image processing module (not shown) to perform polarization-resolved imaging. 【0066】 Figures 4A–4E above illustrate exemplary embodiments of an endoscopic catheter capable of performing polarization-resolved imaging using a small form factor OIIS that utilizes flat components. Those skilled in the art will understand, without departing from the scope of this disclosure, that some of the components may be replaced with refractive or metasurface counterparts. For example, one or more diffractive lenses may be replaced with refractive lenses. Also, several other embodiments, not described in detail herein, may be designed by combining or modifying the various features described with respect to Figures 4A–4E. Notably, each of the embodiments described has the advantage of being particularly well-suited to applications depending on the requirements of imaging or irradiation. For example, in the embodiment shown in Figure 4A, a ray will interact with three polarization components (PSG, PSR, and an absorbing polarizer). The first PSG 412 will segment the ray based on its polarization, and then each of these polarized rays will interact with a PSR that reflects only specific polarizations. If any residual unwanted polarization exists in each optical path, it is absorbed by the absorbing polarizer, which increases the signal-to-noise ratio of the imaging system. Other embodiments, such as system 400d shown in Figure 4D, may benefit from improved efficiency. In particular, the embodiment shown in Figure 4D requires fewer components and, due to absorption or other imperfections in each component, may result in less optical loss of light. 【0067】 Next, referring to Figures 5A–5D, embodiments of multifunctional optical imaging and irradiation are shown. In particular, four embodiments of the multifunctional OIIS are shown, in which the concepts of multispectral, multizoom, and polarization-resolved imaging are combined in a single system. First, referring to Figure 5A, an endoscopic catheter 500a is shown having an OIIS 501a configured to perform multispectral, multizoom, and polarization-resolved imaging simultaneously. This embodiment can be seen as a fusion of the embodiments shown in Figures 2B and 4A. In this endoscopic catheter 500a, the fiber 502 has two cores 503a, 503b, both of which carry two spectral channels centered on a first wavelength and a second wavelength (e.g., 1200 nm and 1300 nm, respectively). The ray 508a coupled from the lower core 503a is collimated by the diffractive lens 507a and becomes linearly polarized (e.g., polarized with P1 polarization) by passing through the absorptive polarizer 514a adjacent to the diffractive lens 507a. The absorptive polarizer is shown stacked with respect to the diffractive lens 507a on the opposite side of the fiber 502, although the absorptive polarizer may be spaced away from the diffractive lens 507a and / or positioned before or after the diffractive lens 507a along the optical path. The ray 508a collides with the WSR 504a, where a first portion of the ray 508a (e.g., a first spectral channel centered at 1200 nm) is reflected toward the substrate 505. The first portion of the ray 508a is diffracted by the diffraction grating 506a, and then diffracted by the PSG 512a toward the diffraction lens 507c, where it is focused to a first focal length (e.g., a focal length of 1 mm). Similarly, the first portion of the ray 508b from the upper core (e.g., a first spectral channel centered at 1200 nm) is focused to the same first focal point after interacting with the diffraction lens 507b, the absorbing polarizer 514b, the WSR 504b, the diffraction grating 506b, the PSG 512a, and the diffraction lens 507c. This optical path shows how the light will be focused toward the object, and the scattered ray will also retrace the same path in reverse through the OIIS 501a and be coupled into the fiber for image processing. 【0068】 A second portion of the ray 508a from the lower core 503a (e.g., a second spectral channel with a central wavelength of 1300 nm) passes through WSRs 504a and 504b unobstructed. This second portion of the ray 508a is reflected by WSR 504c toward the diffraction grating 506c, which then diffracts the ray toward PSG 512b. PSG 512b diffracts the second portion of the ray 508a toward the diffraction lens 507d, which focuses the light to a second focal length (e.g., a focal length of 0.5 mm). Similarly, a second portion of the ray 508b from the upper core 503b (e.g., a second spectral channel with a wavelength centered at 1300 nm) passes through WSR 504b unobstructed. The second portion of the light ray 508b collides with the WSR 504d, where it is reflected toward the substrate 505 and the diffraction grating 506d located on the substrate 505. The diffraction grating 506d diffracts the second portion of the light ray 508b toward the PSG 512b, which then diffracts the light toward the diffraction lens 507d. The diffraction lens 507d combines the light and focuses it to a second focal length. 【0069】 Therefore, the OIIS501a can perform polarization-resolved imaging at two different focal lengths, with the imaging focal length controlled by the central wavelength of the spectral channels of the input light. Additional fiber cores, diffracting lenses, WSRs, PSGs, and diffraction gratings can be added to the system in turn, increasing the number of spectral channels and the associated focal lengths. 【0070】 Figure 5B shows a system 500b having an OIIS501b that can perform multispectral, multizoom, and polarization-resolved imaging in a single embodiment. This embodiment combines the concepts described above with respect to the embodiments in Figures 2B and 4B. The OIIS501b has two fewer components (i.e., diffraction gratings) compared to the OIIS501a, which can result in reduced system complexity and reduced costs associated with manufacturing and assembly. System 500b includes a fiber 502 having a first core 503a and a second core 503b. Cores 503a and 503b can each carry light having two spectral channels (e.g., centered at 1100 nm and 1300 nm). Light from the first core 503a passes through a diffraction lens 507c and is collimated by the diffraction lens 507c. An absorbing polarizer 514a ensures that the passing light has only a single polarization (e.g., P1 polarization). The light encounters WSR504a, where a first portion (e.g., P1 polarization, spectral channel centered at 1100 nm) is reflected toward the substrate 505 and the diffraction grating 506a located on the substrate 505. The diffraction grating 506a directs the first portion of the ray 508a toward PSG512a, where it is again diffracted toward the diffraction lens 507a. Lens 507a focuses the light to a first focal length (e.g., a focal length of 0.75 mm). The second portion of the ray 508a (e.g., P1 polarization, spectral channel centered at 1300 nm) passes unobstructed through WSR504a and 504b and is reflected toward the diffraction grating 506b by WSR504c. The diffraction grating 506b directs a second portion of the light ray 508a towards the PSG 512b, where it is diffracted by the diffraction lens 507b. The lens 507b focuses the light at a second focal length (for example, a focal length of 1 mm). 【0071】 The ray 508b from the second core 503b passes through the diffractive lens 507d and the polarizer 514b. The polarizer 514b causes the ray 508b to have a second polarization (e.g., P2 polarization). The diffractive lens 507c and the polarizer 514a are separated from the diffractive lens 507d and the polarizer 514b by the spacer 515. The first portion of the ray 508b (e.g., P2 polarization, spectral channel centered at 1100 nm) is reflected by the WSR 504b toward the PSG 512a. The PSG 512a allows the P2-polarized first portion of the ray 508b to pass through it, where it collides with the diffractive lens 507a. The light is focused to a first focal length. The second portion of ray 508b (e.g., P2 polarization, spectral channel centered at 1300 nm) passes through WSR504b and is reflected by WSR504d toward the second PSG512b. PSG512b allows the P2-polarized second portion of ray 508b to pass through toward the diffracting lens 507b. The diffracting lens 507b focuses the second portion of ray 508b to a second focal length. 【0072】 The number of components within the endoscopic catheter can be further reduced using the embodiment shown in Figure 5C, where OIIS 501c includes two fewer WSRs compared to OIIS 501b. This embodiment can be understood as a fusion of the OIIS shown in Figures 2B and 4C. The diffracting lenses 507a and 507b (Figure 5C) operate in spectral channels centered on a first wavelength (e.g., 1100 nm) and a second wavelength (e.g., 1300 nm), respectively, resulting in light that is focused at a first focal length (e.g., a focal length of 0.5 mm) and a second focal length (e.g., a focal length of 1 mm). A ray 508a from the first fiber core 503a travels through the diffracting lens 507c and polarizer 514a, where it is polarized with a first polarization (e.g., P1 polarization). The light collides with the first WSR504a, where a first portion (e.g., a spectral channel centered at 1100 nm) is reflected toward the diffraction grating 506a of the substrate 505. The diffraction grating 506a diffracts the light toward the first PSG512a, which is configured to diffract the P1-polarized light toward the first diffraction lens 507a. The first portion of the ray 508a is focused at a first focal length. The second portion of the ray 508a (e.g., a spectral channel centered at 1300 nm) passes through the first WSR504a and is reflected by the second WSR504b toward the second diffraction grating 506b of the substrate 505. The diffraction grating 506b is configured to diffract light toward the second PSG 512b, and the PSG 512b is configured to diffract the P1-polarized light toward the second diffraction lens 507b. The diffraction lens 507b focuses the second portion of the light ray 508a to the second focal length. 【0073】 The ray 508b from the second fiber core 503b travels through the diffracting lens 507d and the polarizer 514b, where they are polarized with a second polarization (e.g., P2 polarization) opposite to the first polarization. The light collides with the first WSR 504a, where a first portion (e.g., a spectral channel centered at 1100 nm) is reflected toward the PSG 512a, which is configured to transmit light with polarization P2. Thus, the first portion of the ray 508b passes unobstructed through the PSG 512a toward the diffracting lens 507a, where it is focused at a first focal length. The second portion of the ray 508b (e.g., a spectral channel centered at 1300 nm) passes through the WSR 504a and is reflected by the second WSG 504b toward the second PSG 512b. The PSG512b is configured to transmit light with polarization P2, and therefore the second portion of the ray 508b passes through the PSG512b unobstructed toward the diffracting lens 507b. Lens 507b focuses the second portion of the ray 508b toward a second focal point. Light reflected from the environment (e.g., surrounding tissue) enters the OIIS501c via the diffracting lenses 507a, 507b and travels backward through the optical path described above for imaging purposes. 【0074】 Referring here to Figure 5D, a catheter system 500d having an OIIS501d is shown. The OIIS501d combines the concepts described above with respect to Figures 2B and 4E. The OIIS501d (shown in Figure 5D) is configured to provide multispectral, multizoom, and polarization-resolved imaging with two spectral channels (i.e., centered at 1200 nm and 1300 nm) having two different focal lengths (i.e., focal lengths of 1 mm and 0.4 mm). The rays 508a emanating from the first fiber 502a may contain the first and second spectral channels. The rays 508a are collimated and polarized by the diffracting lens 507a and the polarizer 514a, respectively. All rays 508a may have a first polarization (e.g., P1 polarization). The ray 508a encounters WSR504a, which is configured to reflect a first spectral channel and transmit a second spectral channel. Thus, the first spectral channel is reflected toward the first diffraction grating 506a of the first substrate 505c, where it is diffracted within the substrate toward PSG512a, which is configured to diffract light having a first polarization (e.g., P1 polarization). The rays 508a having the first spectral channel are focused by the diffraction lens 507b to a first focal point (e.g., 1 mm) as they exit the first substrate toward the environment. The second spectral channel continues through WSR504a toward a second WSR504b, which is configured to reflect light toward the second spectral channel. Therefore, the light rays in the second spectral channel are reflected toward the second diffraction grating 506b of the first substrate, and the second diffraction grating 506b diffracts the light toward the second PSG 512b, which is configured to diffract light having a first polarization (e.g., P1 polarization). The light is diffracted toward the diffraction lens 507c, where it is focused to a second focal point (e.g., 0.4 mm) after leaving the first substrate. 【0075】 The light rays exiting the second fiber 502b follow a separate but similar path. The light ray 508b, containing light centered on the first and second spectral channels, passes through the diffracting lens 507d and the polarizer 514b, where they are substantially collimated and polarized with a second polarization (e.g., P2 polarization). The light in the first spectral channel is reflected by the WSR 504c, where it is diffracted by the diffraction grating 506c of the second substrate 505d. The diffraction grating 506c diffracts the light toward the diffraction grating 506e, which diffracts the light toward the PSG 512a after leaving the second substrate 505d. The first spectral channel of the light ray 508b may exit the second substrate 505d and travel substantially perpendicular to the PSG 512a, aligned with the PSG 512a. Since this light is P2 polarized, it passes through PSG512a to the diffraction lens 507b, where it is focused to a first focal point along with the first spectral channel of ray 508a. The second spectral channel of ray 508b passes through WSR504c, where it is reflected by WSR504d, which is configured to reflect the light in the second spectral channel. The light is diffracted by the diffraction grating 506d of the second substrate 505d toward diffraction grating 506f, which diffracts the light having the second polarization P2. The second spectral channel of the light then exits the second substrate nearly perpendicular to and aligned with PSG512b, which is configured to transmit the light having the second polarization P2 toward the diffraction lens 507c, where it is focused to a second focal length along with the second spectral channel of ray 508a. The spacer 515 is placed between the first substrate 505c and the second substrate to facilitate their assembly and angular alignment. In system 500d, the first substrate 505c and the second substrate 505d are substantially parallel. 【0076】 As described in the previous embodiment, system 500d is a reciprocal system and is configured to capture light scattered or reflected by the surrounding environment (e.g., tissues and organs). The reflected or scattered light enters system OIIS501d through diffracting lenses 507b, 507c and travels in the reverse direction of the optical path described above. Thus, light with a first polarization P1 at first and second spectral lengths is captured by the first fiber 502a, and light with a second polarization P2 at first and second spectral lengths is captured by the second fiber 502b. In the first fiber 502a, light in the first spectral channel is focused at a first focal length, and light in the second spectral channel is focused at a second focal length. Similarly, in the second fiber 502b, light in the first spectral channel is focused at a first focal length, and light in the second spectral channel is focused at a second focal length. 【0077】 Figures 6A–6C show three embodiments configured to extend the depth of focus of an optical imaging and illumination system (OIIS). 【0078】 In three-dimensional medical imaging, depth information is crucial for diagnosis and / or treatment. Generally, in OCT systems, radial resolution (e.g., depth into the tissue of a tubular organ along the optical axis of the OIIS) is determined by the interferometry process, but the acquisition efficiency of the OIIS depends, at least in part, on the depth of focus of the OIIS. Acquisition efficiency is defined as how much signal (i.e., light scattered by tissue) at various depths can be acquired by the OIIS and sent to the image processing module to form an image and perform analysis. However, there is a trade-off between transverse resolution (e.g., imaging resolution in a plane perpendicular to the optical axis) and its depth of focus. For example, increasing the NA of the OIIS can focus the light into a smaller spot, resulting in higher transverse resolution. However, increasing the NA generally results in a decrease in depth of focus. Three embodiments configured to extend the depth of focus while maintaining high transverse resolution are described. 【0079】 Catheter system 600a is shown in Figure 6A. System 600a includes OIIS601a, which uses a polarization-selective diffraction lens (PSDL) to extend the depth of focus of the OIIS. The PSDL diffracts light differently depending on its polarization; for example, light with a first polarization may be diffracted toward a first focal point, while light with a second polarization may be diffracted toward a second focal point, which is different from the first focal point. Thus, a beam formed from light with two different polarizations results in a beam portion that can be focused to two different focal lengths. 【0080】 Fiber 602 (for simplicity, the ferrule holding fiber 602 is not shown here) receives two spectral channels from a light source (not shown), the first spectral channel centered on a first wavelength (e.g., 800 nm), and the second spectral channel centered on a second wavelength (e.g., 1300 nm). The first and second spectral channels are contained in the illustrated ray 608 that exits fiber 602 toward the diffracting lens 607. In some embodiments, one of the spectral channels (e.g., the second spectral channel) is nearly collimated by the diffracting lens 607, while the other spectral channel (e.g., the first spectral channel) is shaped toward a more collimated beam but is not collimated. The difference in optical shaping between the two spectral channels may arise because the diffracting lens 607 is designed to collimate one spectral channel, while the ray in the other spectral channel is not completely collimated by the diffracting lens due to chromatic dispersion. Both spectral channels encompass two orthogonal polarizations (e.g., P1 polarization and P2 polarization). A ray 608 having the first spectral channel is reflected by WSR604a, which is designed to reflect the first spectral channel and transmit the second spectral channel. The reflected ray travels toward the first PSDL616a on the substrate 605. The first PSDL616a is configured to focus a portion of the first spectral channel having polarization P1 (shown by a solid line) at a first focal length (e.g., f1 = 1.2 mm) and to focus a portion of the first spectral channel having polarization P2 (shown by a dotted line) at a second focal length (e.g., f2 = 0.8 mm). Focusing light centered on the same spectral channel at both the first and second focal lengths extends the depth of focus of OIIS601a in the spectral channel. Light scattered by the object being imaged can be more efficiently captured by the OIIS601a if it is within a specific distance (depth of focus) of either the first or second focal length.Depth of focus (DOF) can be defined as shown in Equation 1, where n is the refractive index of the medium, λ is the wavelength of light, and NA is the numerical aperture. 【0081】 【number】 【0082】 This DOF ​​value determines the distance along the optical axis near the focal point at which the image remains in focus. In an OIIS with two focal lengths, it can be beneficial to have a DOF for the overlap of each focal point through appropriate design of parameters (e.g., wavelength, numerical aperture), resulting in an extended depth of field beyond what is conventionally possible. 【0083】 The second spectral channel passes unobstructed through WSR604a and is reflected by the second WSR604b toward the second PSDL616b. Rays with P1 polarization (shown by dashed lines) are focused at a third focal length (e.g., f3 = 0.5 mm), and rays with P2 polarization (shown by dashed lines) are focused at a fourth focal length (e.g., f4 = 0.3 mm). Making collected light within the range of the third and fourth focal lengths available, as described above for the first and second focal lengths, extends the depth of focus of OIIS601a in the second spectral channel. 【0084】 In OCT imaging systems, or other types of imaging systems, the excitation light (e.g., light emitted into the surrounding environment such as tissue) can have a considerable bandwidth, meaning it is not a single wavelength with a very narrow bandwidth. The excitation light can be emitted from LEDs, swept-source lasers, VCSELs, supercontinuum sources, superluminescent diodes, or other types of sources, each with a tunable center wavelength and / or tunable bandwidth. By designing diffractive lenses with tuned chromatic dispersion, a broad bandwidth of input light can be used to extend the depth of focus of an OIIS system. The focal length of each diffractive lens is assumed to be a function of wavelength, as shown in Equation 2. 【0085】 【number】 【0086】 In Equation 2, f is the focal length, C is a constant, λ is the wavelength, and m is an integer value. Referring now to Figure 6B, the catheter system 600b includes OIIS601b, which shows two examples of diffractive lenses that can be described by Equation 2 above. The first diffractive lens 607a is shown with m=1 (e.g., a normal diffractive lens), and the second diffractive lens 617 is shown with m=3 (e.g., a superdispersive diffractive lens). In this embodiment, the fiber 602 outputs coupled a first spectral channel (e.g., centered at 1000 nm) and a second spectral channel (e.g., centered at 1300 nm). Each channel has a spectral bandwidth of full width at half maximum (FWHM) (e.g., each spectral channel may have an FWHM of 200 nm). In ray tracing simulations, for simplicity, each ray may be modeled as having a single wavelength, as shown in Figure 6B. Four different rays with wavelengths 1, 2, 3, and 4 are shown. In some embodiments, the 1st, 2nd, 3rd, and 4th wavelengths may be approximately 900 nm (solid line), 1100 nm (dotted line), 1200 nm (dashed line), and 1400 nm (dotted-dotted line), respectively. All rays exit fiber 602 and pass through diffracting lens 607b, where they are nearly collimated. Lens 607b may be designed to completely collimate light having one wavelength within the range of wavelengths covered by the 1st to 4th rays. For example, lens 607b may be designed to completely collimate light having a wavelength of 1300 nm. Rays with wavelengths different from the designed wavelength are not completely collimated, and they may diverge or converge slightly after lens 607b. 【0087】 In this example, first and second rays, having wavelengths of 900 nm and 1100 nm, are reflected by WSR604a toward the diffracting lens 607a. WSR604a may be positioned at an angle (e.g., about 45 degrees) to the upper surface of the substrate 605, so that the reflected rays are incident on the substrate almost perpendicular to the upper surface. The diffracting lens 607a is a standard diffracting lens where m=1 in equation 2. Thus, lens 607a focuses the first and second rays at first and second focal lengths (e.g., f1=0.611 mm and f2=0.5 mm), respectively, thereby extending the depth of focus of OIIS601b in the first and second spectral channels. The third and fourth rays (for example, rays with wavelengths of 1200 nm and 1400 nm, respectively) pass through WSR604a and are reflected by the second WSR604b toward the superdispersive diffraction lens 617. The focal length of this superdispersive diffraction lens 617 follows Equation 2, where m=3. Using the superdispersive diffraction lens, a larger focal length shift can be achieved by changing the wavelength. This effect is shown in ray tracing simulations, where the third ray is focused to a third focal length (e.g., 1.588 mm at a wavelength of 1200 nm) and the fourth ray is focused to a fourth focal length (e.g., 1 mm at a wavelength of 1400 nm). Thus, the superdispersive diffraction lens can be used to further extend the depth of focus of OIIS601b in the third and fourth spectral channels. 【0088】 Referring here to Figure 6C, the catheter system 600c with OIIS601c shows an embodiment in which the depth of focus is extended by utilizing axicons to focus light. In OIIS601c, four axicons 618a-618d are assumed to generate a J0 Bessel beam, but have different numerical apertures (NAs). In system 600c, fiber 602 transmits four spectral channels centered on first, second, third, and fourth wavelengths (e.g., 1000 nm, 1100 nm, 1200 nm, and 1300 nm, respectively). These spectral channels are collimated or nearly collimated by the diffractive lens 607. The first ray having the first wavelength is reflected toward the substrate 605 by WSR604a and focused by the first axicon 618a. This axicon is designed for a first wavelength (e.g., 1000 nm) and has a first numerical aperture (e.g., NA1 = 0.15). This relatively small NA results in a relatively large depth of field (e.g., on a millimeter scale), as shown in Figure 6C. The second to fourth rays pass through the WSR604a. The second ray is reflected by the second WSR604b and focused by the second axicon 618b. In some embodiments, the second axicon 618b has a second NA (e.g., NA2 = 0.25) that is larger than the first NA. Increasing the NA results in a smaller focal spot. A smaller focal spot provides better resolution for imaging at the expense of a reduced depth of field. 【0089】 The third and fourth rays pass through the second WSR604a unobstructed. The third ray is reflected by the third WSR604c, while the fourth ray passes through the third WSR604c and is reflected by the fourth WSR604d. The third ray is focused by the third axicon 618c, which has a third NA (e.g., NA3 = 0.5), and the fourth ray is focused by the fourth axicon 618d, which has a fourth NA (e.g., NA4 = 0.8). Increasing the NA decreases the depth of focus and increases the resolution. Overall, the depth of focus of the OIIS601c is increased by utilizing one or more axicons for focusing. One or more depths of focus can be selected for imaging by changing the spectral channels of the input signal; therefore, the OIIS601c provides adjustable depth of focus and NA. 【0090】 Figures 7A–7C illustrate embodiments of an optical imaging and illumination system that allows for reconfiguration of the focal length. In the previously described embodiments, the multi-zoom function within the OIIS was achieved by changing the central wavelength of the input light. This can be achieved using an adjustable input light source. Figures 7A–7C describe embodiments in which the focal length of the OIIS embodiment can be reconfigured using a liquid crystal (LC) based device without the need to change the wavelength of the light source. 【0091】 In the catheter system 700a shown in Figure 7A, the OIIS 701a is designed at a first wavelength (e.g., a central wavelength of 800 nm). The coupled ray 708 from the fiber 702 is collimated by the diffracting lens 707d. An absorptive polarizer 714 is stacked adjacent to the diffracting lens 707d to linearly polarize the ray 708 (e.g., to have P1 polarization). The functions of the LCGs 719a and 719b can be controlled by adjusting the input polarization. In some embodiments, a quarter-wave plate or other type of wave plate (not shown) may be included after the absorptive polarizer 714 as desired, to produce different polarizations (e.g., P2 polarization) as desired. The polarized ray is reflected toward the substrate 705 by the mirror 709. The substrate may have an anti-reflective coating on at least the first surface 705a to reduce reflection loss when incident on the substrate 705. The ray 708 is diffracted by the diffraction grating 706a toward the first liquid crystal grating (LCG) 719a (for example, at a diffraction angle greater than the TIR angle of the substrate). The function of each LCG can be independently controlled by one or more electrical signals (not shown). The electrical signals can be controlled by a control module and can be controlled manually or automatically. In the off state, the LCG can function as a grating tuned to the wavelength of the ray 708, and the ray 708 is diffracted by the LCG 719a. In the on state, the LCG 719a does not interact with the incoming ray, and the ray 708 continues to remain at the TIR through the substrate 705. 【0092】 First, a system 700a having an LCG719a in the OFF state is described. A ray 708 is diffracted by the diffraction grating 706a toward the OFF LCG719a. The OFF LCG719a diffracts the ray 708 toward the diffraction lens 707a, where they are focused at a first focal length (e.g., a focal length of 0.5 mm). This is the end of the optical path when the LCG719a is OFF. 【0093】 In the second scenario, where LCG719a is ON, the ray 708 is diffracted toward LCG719a by the diffraction grating 706a and does not interact with LCG719a. Instead, the ray 708 is reflected by the upper surface of the substrate 705 by TIR. After reflection from the upper surface 705a, the ray 708 reaches the second LCG719b. When the second LCG719b is OFF, the ray 708 is diffracted toward the diffraction lens 707b, where they are focused at a second focal length (e.g., a focal length of 1.5 mm). This is the end of the optical path when LCG719a is ON and LCG719b is OFF. 【0094】 In the third scenario, both LCG719a and LCG719b are turned on, and therefore the light rays will not interact with either the first or second LCG719a, 719b. The light rays 708 propagate through the substrate 705 in TIR until they reach the second diffraction grating 706b. After being diffracted by the grating 706b, the light rays 708 are focused by the diffraction lens 707c to a third focal length (e.g., a focal length of 3 mm). 【0095】 By switching the LCG on and off, the OIIS701a can be reconfigured to emit light at a desired focal length (and can also be focused by the reciprocity of the system). In some embodiments, three distinct focal lengths (e.g., 0.5 mm, 1 mm, and 3 mm) can be achieved. Those skilled in the art will understand that the number of achievable focal lengths can be increased or decreased, respectively, by cascading more or fewer LCGs, along with other suitable components (e.g., diffraction gratings and / or diffractive lenses designed to have selected focal lengths). 【0096】 Figure 7B shows an embodiment in which the catheter system 700b includes a liquid crystal half-wave plate (LCHWP) within the OIIS 701b. The LCHWP is used to realize a reconfigurable multi-zoom OIIS 701b. In system 700b, the ray 708 has a spectral channel with a central wavelength (e.g., 1100 nm). After exiting the fiber, the ray 708 is collimated by a diffracting lens 707e designed for the wavelength of the ray 708. The collimated ray is linearly polarized by an absorptive polarizer 714 (e.g., with P1 polarization). The polarized ray 708 interacts with the first LCHWP 720a. 【0097】 First, the optical path will be described for the first scenario (shown by the solid line) in which the first LCHWP720a is in the off state. When in the off state, the LCHWP720a functions as a half-wave plate (HWP), changing the incident linearly polarized light ray to an orthogonal state (e.g., P2 polarization). The light ray interacts with the first polarization-selective reflector (PSR) 713a. All PSRs in the system (e.g., 713a, 713b, 713c, 713d) are copolarized with the absorptive polarizer 714, meaning that if a linearly polarized light ray 708 passes through 714, the light ray 708 also passes through the PSRs. In this example, the absorptive polarizer 714 transmits light rays with P1 polarization, and the PSRs transmit P1 polarized light rays and reflect P2 polarized light rays. A ray 708 passing through the first LCHWP720a in the off state will have its polarization switched (for example, from P1 polarization to P2 polarization), so the ray will be reflected by the PSR713a toward the diffracting lens 707a located on the substrate 705. The lens 707a focuses the ray 708 to a first focal length (for example, a focal length of 0.25 mm). 【0098】 In the second scenario, the first LCHWP720a is in the ON state and the second LCHWP720b is in the OFF state. In this case, after passing through 720a, the light rays 708 pass through PSR713a without changing their polarization (e.g., remaining P1 polarized), and then they reach the second LCHWP720b. In the OFF state, LCHWP720b functions as an HWP that switches the polarization of light rays (e.g., from P1 polarization to P2 polarization). Therefore, light rays 708 passing through the OFF state LCHWP720b are reflected by PSR713b toward the diffracting lens 707b, where they are focused at a second focal length (e.g., a focal length of 0.5 mm). Similarly, by adjusting the first and second LCHWP720a,720b to ON and LCHWP720c to OFF, the light rays are reoriented toward the diffracting lens 707c and focused to a third focal length (e.g., a focal length of 0.75 mm). 【0099】 The final scenario is when the first three LCHWP720a-720c are ON and the fourth LCHWP720d is OFF. The polarization of ray 708 is switched by the fourth LCHWP720d, and ray 708 is reflected by PSR713d toward diffracting lens 707d, where it is focused at a fourth focal length (e.g., a focal length of 1 mm). Thus, by adjusting the selected LCHWP on and off, ray 708 can be directed toward a specific diffracting lens, thereby focusing the light to a selected focal length. OIIS701b can focus light at four discrete values ​​(e.g., focal lengths of 0.25 mm, 0.5 mm, 0.75 mm, and 1 mm), and more or fewer focal lengths can be achieved by adding or removing one or more LCHWPs, PSRs, and diffracting lenses. 【0100】 The fourth LCHWP720d is shown positioned at a certain angle (e.g., about 45 degrees) relative to the fourth PSR713d, while the first, second, and third LCHWP720a-c are positioned at angles equal to those of the first, second, and third PSR713a, 713b, and 713c, respectively. The angles of the LCHWPs relative to the PSRs can be adjusted according to the design of the LCHWPs, as long as similar results are achieved. In an alternative embodiment, the fourth LCHWP720d may be removed, and the PSR713d may be reoriented such that the PSR713d (e.g., the last PSR in a series) is cross-polarized with respect to the absorptive polarizer 714. The resulting OIIS has similar functionality to the OIIS701b but with one less component. As with other embodiments disclosed herein, this configuration can be combined with other embodiments described herein to add further functionality, such as polarization-resolved imaging or multispectral imaging. 【0101】 Referring here to Figure 7C, an embodiment is shown in which an OIIS having four reconfigurable focal lengths can be achieved. The catheter system 700c includes an OIIS 701c. A ray tracing simulation is shown in which a ray 708 having a first wavelength (e.g., a wavelength of 1300 nm) propagates through the system 700c. These rays are collimated by a diffractive lens 707. To ensure that the ray 708 is linearly polarized with a first polarization (e.g., P1 polarization), an absorptive polarizer 714 is placed after the diffractive lens 707. In system 700c, a PSR 713a is oriented to a cross-polarization position relative to the absorptive polarizer 714. In particular, the PSR 713a may be designed to be copolarized with the polarizer 714, and the resulting OIIS operates similarly to the OIIS 701c. Therefore, similar system functionality can be achieved by changing the orientation of components or making other minor adjustments in the design, and such changes and adjustments are design choices and do not deviate from the scope of this disclosure. 【0102】 Referring to Figure 7C, the first optical path is illustrated and shown by a solid line. In this first scenario, LCHWP720a is ON and does not change the polarization of the ray (e.g., ray 708 remains P1 polarized). The first PSR713a is cross-polarized with polarizer 714, and therefore ray 708 is reflected by PSR713a toward LCHWP720c of substrate 705. Since LCHWP720c is also ON, it does not change the polarization of ray 708. As a result, ray 708 will maintain its original polarization state (e.g., P1 polarization) and will be focused by polarization-selective diffraction lens (PSDL) 716a at a first focal length (e.g., f1 = 0.25 mm). 【0103】 If the state of LCHWP720a remains ON and LCHWP720c is switched OFF, the polarization of ray 708 will be switched to an orthogonal state (e.g., P2 polarization) by LCHWP720c before interacting with PSDL716a. Since PSDL focuses light differently depending on the polarization of the light, PSDL716a will focus the P2 polarized ray 708 at a second focal length (e.g., f2 = 0.5 mm) different from the first focal length. PSDL716a is designed so that it focuses P1 polarized light at focal length f1 and P2 polarized light at focal length f2. P1 and P2 are linear polarizations of two arbitrarily selected orthogonal states, but they can alternatively be circularly polarized or elliptically polarized, while achieving the same functionality as OIIS701c. 【0104】 In the second scenario, LCHWP720a is switched off, which results in the polarization of the incident ray 708 switching to orthogonal polarization (e.g., P2 polarization). The P2-polarized ray 708 will pass through PSR713a and reach PSR713b. PSR713b is oriented to be cross-polarized with respect to PSR713a, and therefore PSR713b reflects the P2-polarized ray toward LCHWP720b. When LCHWP720b is on, it does not change the polarization of ray 708 (e.g., ray 708 maintains P2 polarization). PSDL716b will focus these rays at a third focal length (e.g., f3 = 0.75 mm). However, when LCHWP720b is switched off, LCHWP720b will switch the polarization of the incoming rays. Therefore, when LCHWP720b is off, the ray 708 switches to P1 polarization, and PSDL716b will focus the P1-polarized ray 708 at a fourth focal length (e.g., f4=1mm) that is different from the third focal length. Thus, by appropriately changing the on / off state of each LCHWP in the system and utilizing polarization-selective diffractive lenses whose focal length depends on the polarization of the incident ray, an OIIS with reconfigurable focal lengths can be realized using one or more input electrical signals to the LCHWP components. 【0105】 OIIS with reconfigurable focal lengths are advantageous for depth imaging. In particular, adjustable focal lengths can be used to obtain the best image quality at the depth of interest. For irradiation, the focal length can be selected to achieve maximum light intensity at a specific depth of tissue for therapeutic purposes, such as tissue ablation or other laser surgical applications, or for other uses. 【0106】 Figure 8A shows an exploded view of an embodiment of the OIIS801a, illustrating different integration schemes with various components. In particular, Figure 8A shows how one can utilize horizontal cascading and / or vertical stacking of various components to add special functionality to the optical imaging and illumination system. Most of the components used in the embodiments described above have a planar shape that can be easily integrated / stacked with other planar components such as substrates 805c and 805d, WSG811, PSR813a-813b, absorptive polarizers 814a-814c, spacer 815, PSDL816, LCG819, LCHWP820, waveplates (WP) 821a-821b (e.g., half-waveplates and quarter-waveplates), color filters 822, thin films 823 (e.g., AR coatings), diffracting elements 824 (e.g., holograms, diffusers, subwavelength diffraction gratings), and angle-selective surfaces 826. Furthermore, these components can be integrated with or combined with refractive components such as lens 825. This vertical integration capability can advantageously extend the functionality of the OIIS described herein. For example, by stacking liquid crystals, polarizers, and waveplates, one can control / modify the polarization of light as desired and / or remove unwanted polarization. Several other examples include stacking thin films 823 and color filters 822 to control the reflection or transmission of light depending on its wavelength. To avoid reflection losses, thin films can be used to form AR coatings on substrate surfaces or various other components such as fiber end faces. 【0107】 The integration of sensors / detectors 827 on the OIIS platform, which can receive feedback from the imaging / irradiation scene, is also contemplated herein. An example of a sensor is a depth sensor for measuring the distance from the OIIS to the object being imaged (such as an organ or tissue) and adjusting its focal length and other parameters accordingly. The adjustment may be made manually based on readings from the depth sensor, or it may be controlled automatically by a control module (not shown). Various circuits to one or more components within the OIIS, such as sensors and electrically actuated LC-based components, may be included in the substrate or other components within the OIIS. For clarity, these circuits are omitted from the illustration. 【0108】 The components included in OIIS801a or 801b may have any angle with respect to the substrate 805, as shown in Figure 8B. For example, one or more of the components may have an angle θ with respect to the substrate. The angle θ may be 30°, 35°, 45°, 50°, 55°, or any other value. Figure 8B also shows an example of OIIS801b enclosed by a tube 828. This tube may have any inner diameter (ID) and outer diameter (OD). It may also be made of glass, plastic, polymer, or other suitable material. This tube is in the optical path (for example, between the lens of various OIIS systems and the tissue or object being imaged), and the lens will focus light through this tube. Therefore, the contour and material of the tube may be taken into consideration when designing the lenses and other components within the OIIS. 【0109】 In Figure 9, a block diagram shows different modules for carrying out the methods disclosed herein according to several embodiments. Figure 9 shows a high-level schematic diagram of the different modules and systems, some of which may be optional, illustrating how they can work together to improve the performance of the overall imaging and illumination system. The imaging and illumination system may include one or more embodiments of the OIIS, as described herein. In the system shown in Figure 9, the OIIS 901 is designed to focus light onto a target and / or collect scattered light from the target to form an image. The OIIS 901 receives input light from the processing module 930 via a transmission module 929. The transmission module may include one or more single-mode fibers, one or more photonic crystal fibers, and / or one or more multimode fibers. The fibers transmit input light from a light source (such as a laser, LED, supercontinuum, or sweeping light source) to the OIIS and then collect image information from the OIIS for reverse transmission to the processing module. Furthermore, the transmission module 929 may include at least one wire and / or at least one wireless transmitter. The wire and / or wireless transmitter may be used to transmit electrical or electromagnetic signals between the sensor (see sensor / detector 827 in Figure 8A) and the processing module. The processing module may include at least one interference arm (in the case of optical coherence tomography), at least one photodetector, at least one camera, at least one image sensor, at least one fiber coupler (e.g., 50 / 50 fiber coupler, 30 / 70 fiber coupler, 20 / 80 fiber coupler, 10 / 90 fiber coupler), and / or at least one spectrometer for image processing purposes. All of these components within the processing module may be used collectively to form and analyze images and send them to the display module 932. The user / artificial intelligence (AT) module 933 receives image information from the display module and then determines which parameters in the processing module or OIIS need to be changed / adjusted to improve image quality.The user and / or AI933 analyze the data and make necessary changes and adjustments via the control module 931, processing module 930, and transmission module 929. 【0110】 The foregoing description and drawings illustrate various embodiments of the invention and should not be construed as limiting the invention. Although several exemplary embodiments of this invention have been specifically described, those skilled in the art will readily understand that many modifications are possible in the exemplary embodiments without substantially departing from the novel teachings and merits of this disclosure. Thus, many different embodiments arise from the above description and drawings.

Claims

[Claim 1] An optical system for an endoscope, wherein the optical system is A substrate having a first surface and a second surface, wherein at least the first surface is configured to transmit light propagating along the axial direction and is oriented substantially parallel to the axial direction of a fiber, An optical component disposed on the first surface of the substrate and supported by the substrate, wherein the optical component directs the light from the fiber into at least two optical paths, each of which is reoriented perpendicular to the optical axis and focused to different focal spots located on one side of the optical system, Includes, An optical system characterized in that each of the two optical paths propagates through the substrate. [Claim 2] An optical system according to claim 1, wherein the optical system has a cross-section of 1.5 mm × 1.5 mm or less. [Claim 3] An optical system according to claim 2, wherein the optical system has a length of 5 mm or less. [Claim 4] An optical system according to claim 1, wherein light exits the fiber propagating along the axial direction and is directed toward the substrate by a light reflector mounted on the first surface, and the reflection of the light by the light reflector is not based on total internal reflection. [Claim 5] An optical system according to claim 1, wherein the optical system further collects light scattered from tissue located at the focal spot via propagation along the two optical paths in opposite directions. [Claim 6] An optical system according to claim 1, wherein the optical component is attached to the first surface and extends in a transverse direction away from the first surface. [Claim 7] The optical system according to claim 6, wherein the optical component includes a wavelength-selective reflector mounted at a certain angle to the first surface. [Claim 8] The optical system according to claim 6, wherein the optical component includes a flat component mounted on the first surface at an angle selected from the group consisting of about 37 degrees, about 45 degrees, and about 50 degrees. [Claim 9] An optical system according to claim 1, characterized in that the optical components are arranged flatly on at least the first surface. [Claim 10] An optical system according to claim 9, wherein the optical component includes a diffraction grating. [Claim 11] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising a diffractive lens arranged flatly on at least the first surface, wherein one of the optical paths exits the substrate in a transverse direction, and the diffractive lens focuses the optical path to a corresponding focal spot. [Claim 12] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising a diffraction grating arranged flatly on at least the first surface, wherein the diffraction grating redirects one of the optical paths propagating within the substrate. [Claim 13] An optical system according to claim 12, characterized in that the diffraction grating redirects the optical path to a propagation angle larger than the total internal reflection angle of the substrate. [Claim 14] An optical system according to claim 1, characterized in that one of the optical paths propagates through the substrate using total internal reflection at least on the first surface. [Claim 15] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising an axicon disposed planarly on at least the first surface, wherein one of the optical paths emits light transversely across the substrate, and the axicon focuses the optical path to a corresponding focal spot with an extended depth of focus. [Claim 16] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising a collimator attached to the first surface, wherein the collimator causes light present in the fiber propagating along the axial direction to collimate. [Claim 17] An optical system according to claim 1, characterized in that the different focal spots have different focal lengths. [Claim 18] An optical system according to claim 1, characterized in that the different focal spots have different numerical apertures. [Claim 19] An optical system according to claim 1, characterized in that the different focal spots have different working distances. [Claim 20] An optical system according to claim 1, characterized in that the different focal spots have different depths of focus. [Claim 21] An optical system according to claim 1, characterized in that the two optical paths include two different spectral channels. [Claim 22] An optical system according to claim 1, characterized in that the two optical paths include two different polarization channels. [Claim 23] The optical system according to claim 1, wherein the optical system further comprises a pair of at least two optical components supported by the substrate, the pair of optical components directing the light from the fiber into at least three optical paths, the three optical paths comprising at least two with different focal parameters, different wavelengths, and different polarizations. [Claim 24] An optical system according to claim 1, wherein the optical system further includes a controller, the optical component being wavelength-selective, and the controller adjusting the wavelength composition of light transmitted by the fiber. [Claim 25] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising a controller, wherein the optical path includes wavelength-sensitive or wavelength-selective components, and the controller adjusts the wavelength composition of light emitted by the fiber. [Claim 26] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising a controller, wherein the optical component is wavelength-selective, and the controller adjusts the wavelength selectivity of the optical component. [Claim 27] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising a controller, wherein the optical path includes a wavelength-sensitive component, and the controller adjusts the wavelength sensitivity of the component. [Claim 28] The optical system according to claim 1, wherein the optical system further comprises: An optical system comprising a controller, wherein the optical path includes at least one electro-optical component, and the controller includes a controller that adjusts the electro-optical component. [Claim 29] An optical system according to claim 28, wherein the electro-optical component includes a liquid crystal component. [Claim 30] An optical system for an endoscope, wherein the optical system is A substrate having a first surface and a second surface, wherein at least the first surface is configured to collect light propagating along the axial direction, and the substrate is oriented substantially parallel to the axial direction of a pair of at least two fiber cores, An optical component disposed on the first surface of the substrate and supported by the substrate, wherein the optical component directs light from a focal spot located on one side of the optical system into at least two optical paths, each of which is redirected in the axial direction and collected by a corresponding fiber core, Includes, An optical system characterized in that each of the two optical paths propagates through the substrate. [Claim 31] An optical system according to claim 30, wherein the optical component includes a polarization-selective grating. [Claim 32] An optical system according to claim 30, wherein the optical component includes a polarization-selective reflector. [Claim 33] An optical system according to claim 30, wherein the optical component includes a polarization-selective diffractive lens. [Claim 34] An optical system for an endoscope, wherein the optical system is A substrate having a first surface and a second surface, wherein at least the first surface is oriented substantially parallel to the axial direction of two fiber cores configured to collect light propagating along the axial direction, An optical component disposed on the first surface of the substrate and supported by the substrate, wherein the optical component directs light from a focal spot located on one side of the optical system into at least two optical paths, each of which is redirected in the axial direction and collected by a corresponding fiber core, Includes, An optical system characterized in that each of the two optical paths propagates through the substrate. [Claim 35] The optical system according to claim 34, wherein the two fiber cores include a single fiber having two fiber cores. [Claim 36] The optical system according to claim 34, characterized in that the two fiber cores include two fibers, each having a single fiber core. [Claim 37] An optical system according to claim 34, characterized in that the two optical paths propagate light in opposite directions. [Claim 38] An optical system for an endoscope, wherein the optical system is Two substrates, each having a first surface and a second surface, the first surface being configured to transmit light propagating along the axial direction, and the two substrates being oriented substantially parallel to the axial direction of the fiber, An optical component disposed on the first surface of the substrate and supported by the substrate, wherein the optical component directs the light from the fiber into at least two optical paths, each of which is reoriented perpendicular to the optical axis and focused to different focal spots located on one side of the optical system, Includes, An optical system characterized in that each of the two optical paths propagates through the substrate. [Claim 39] An optical system according to claim 38, characterized in that the two optical paths propagate light in opposite directions. [Claim 40] An endoscope catheter, wherein the endoscope catheter is An optical fiber having two ends, A fiber connector coupled to one end of the optical fiber, An optical system coupled to the other end of the optical fiber, wherein the optical system includes any of the optical systems from claims 1 to 39, An endoscopic catheter characterized by containing [a specific component]. [Claim 41] An endoscopic catheter according to claim 40, wherein the endoscopic catheter further comprises: A ferrule connecting the optical system to the optical fiber, A torque coil for rotating the optical system, An endoscopic catheter characterized by containing [a specific ingredient / feature].