Abstract:
An exemplary arrangement can be provided which can include a lens arrangement which can have at least two reflecting surfaces on opposing sides thereof, each of the reflecting surfaces can have a reflectivity that can be greater than 10%. The lens arrangement can include a gradient index lens, and can have a refractive optical element, a diffractive optical element, a planar convex lens, an aspheric lens, a ball lens or a cylindrical lens.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS) 
       [0001]    This application relates to and claim priority from U.S. Patent Application Ser. No. 61/734,675 filed Dec. 7, 2012 and U.S. Patent Application Ser. No. 61/791,394 filed Mar. 15, 2013, the entire disclosures of which are incorporated herein by reference. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates to optical imaging, and more particularly to exemplary embodiments of optical system for endoscopic internally-referenced interferometric imaging, and method for employing the same. 
       BACKGROUND INFORMATION 
       [0003]    Optical coherence tomography (“OCT”) is an imaging modality that provides cellular detail and live motion capture of tissues. It has been employed successfully for microscopic analysis of coronary artery and oesophageal mucosa by the endoscopic approach in living human subjects. OCT is well suited for non-invasive microscopy in cells and tissues since it can be implemented via small, flexible probes, does not require contact with the cell surface or use of contrast medium, and acquires high resolution images with very rapid acquisition times and flexible focal range. 
         [0004]    Micro-Optical Coherence Tomography (“μOCT”) is a second-generation imaging technology which facilitates high-resolution ranging in tissue by detecting spectrally resolved interference between the tissue sample (“sample beam”) and a reference (“reference beam”). Recent studies demonstrated μOCT images with an axial resolution of 1.5 μm, transverse resolution of 2 μm and acquisition rate of fifty million pixels per seconds, potentially facilitating in vivo, non-destructive, cellular level imaging of a cubic mm of tissue in, e.g., thirty seconds. Exploring such large region of interest at the cellular level, can facilitate a better understanding and treatment of disease. 
         [0005]    Exemplary Challenges In μOCT Probe Design 
         [0006]    The unique characteristics of the μOCT modality, including a centrally obscured beam aperture profile (e.g., “donut beam”), require a customized design for the imaging probe. In prior art, a μOCT probe design was demonstrated in which the “donut beam” profile was generated with a right-angle prism coated reflectively with a circular central region remaining uncoated. The fabrication and alignment of such prior design utilizing 2 mm optics would be difficult to further miniaturize to sub-millimeter sizes necessary for human intracoronary use. 
         [0007]    Accordingly, there may be a need to overcome at least some of the issues and/or deficiencies described herein above. 
       SUMMARY OF EXEMPLARY EMBODIMENTS OF PRESENT DISCLOSURE 
       [0008]    To address and/or overcome the above-described problems and/or deficiencies, exemplary embodiments of optical system can be provided for endoscopic internally-referenced interferometric imaging, and method for employing the same. 
         [0009]    According to an exemplary embodiment of the present disclosure, e.g., reflective discs are deposited directly onto the optical lens surfaces to form the desired beam profile and act as the reference reflector, resulting in a more compact probe and a simplified assembly process. This exemplary configuration can resemble a Mirau interferometer in general layout, although differs substantially in two ways: the laser beam is split to sample and reference beams by an aperture apodization that may be either partial reflecting of fully reflecting, rather than partial reflectance in the Mirau inteferometer, and the reference arm resides within a focusing optical element. 
         [0010]    Exemplary Coronary Artery Application 
         [0011]    One exemplary embodiment of a probe design according to the present disclosure can be applicable to microscopic analysis of coronary artery in vivo. For example n optical fiber delivers the broad spectrum laser light to the distal probe, and retrieves the optical signal from the probe to a bedside analysis station, consisting of a spectrometer and image construction and processing system. To physically access the intracoronary environment, the exemplary probe can be miniaturized to a diameter of, e.g., no larger than about 2 mm. 
         [0012]    Exemplary Applications Beyond Cardiovascular System 
         [0013]    The exemplary embodiment of the probe can also be applicable for organs and tissues outside of the coronary arteries. For example, any organ with an endoscope-accessible lumen, including respiratory airways, gastrointestinal tract, urinary tract, and reproductive tract, can be possible targets for endoscopic μOCT imaging. 
         [0014]    Exemplary Interferometric Probe Optical Assembly 
         [0015]    One exemplary embodiment of the present disclosure provides an exemplary endoscopic interferometric probe. The exemplary probe can include an optical fiber for delivering illumination and extraction of the interferometer output, collimating and focusing optics, selectively deposited reflective surfaces to apodize the illumination and to act as the reference reflector, an angled mirror to turn the optical axis perpendicularly towards the sideways view, and a rigid enclosure to encase the assembly and isolate the optical components from the biological environment. 
         [0016]    Exemplary μOCT Platform With Endoscopic Probe Interface 
         [0017]    According to another embodiment of the present disclosure, an integrated imaging system can be provided that can include the exemplary probe described in the previously-described exemplary embodiment and an exemplary platform that can acquire optical reflectance depth profiles, images, volumes, or movies of tissues, or organs, including their secretions and immediate environment, using μOCT technology. In this exemplary embodiment, the endoscopic probe can provide an interface between the exemplary μOCT platform and the imaging target, thus facilitating imaging at the cellular level of tissue accessible to the exemplary endoscope. 
         [0018]    These and other objects of the present disclosure can be achieved by provision of an arrangement which can include a lens arrangement which can have at least two reflecting surfaces on opposing sides thereof, each of the reflecting surfaces can have a reflectivity that can be greater than 10%. The lens arrangement can include a gradient index lens, and can have a refractive optical element, a diffraction optical element, a planar convex lens, an aspheric lens, a ball lens or a cylindrical lens. 
         [0019]    In certain exemplary embodiments of the present disclosure, at least one of the reflective surfaces can include a metallic coating(s) or a dielectric coating. In some exemplary embodiments of the present disclosure, upon an entry of a first radiation through the lens arrangement, a first portion(s) of the first radiation can impact a first portion of the surfaces to reflect as a second electromagnetic radiation can impact a second one of the surfaces. A second portion(s) of the first radiation can be transmitted as a third electromagnetic radiation via the lens arrangement to reach a sample(s). A spatial electrical field distribution of the second radiation can be different from that of the third radiation along a dimension that can be non-parallel to an optical axis of transmission of the first radiation. 
         [0020]    In certain exemplary embodiments of the present disclosure, the focus of the second radiation can be provided at a predetermined optical path length difference from a focus of the third radiation. The predetermined optical path length difference can be less than 10 mm, 3mm 1 mm and/or 100 μm. The spatial electrical field distributions of the second and third radiations can be symmetric along the dimension non-parallel to the optical axis of transmission, and/or rotationally symmetric with respect to the optical axis. A first one of the surfaces can have a first reflectivity profile that can be rotationally symmetric, and a second one of the surfaces can have a second reflectivity profile that can be rotationally symmetric. The first reflectivity profile can be different from the second reflectivity profile along a radius of each of the surfaces. 
         [0021]    In certain exemplary embodiments of the present disclosure, a detection apparatus can be configured to detect a fourth radiation provided from the sample(s) that can be associated with the third radiation, and a fifth radiation can be provided from a second one of the surfaces which can be associated with the second radiation, so as to generate a detected signal. A processing apparatus can be configured to determine depth information regarding the sample(s) based on the detected signal. 
         [0022]    In certain exemplary embodiments of the present disclosure, the lens arrangement can be situated at least partially in a probe, and the probe can be a catheter or an endoscope. The lens arrangement can be situated at a housing that can have a shape of a pill that can be configured to be swallowed. In certain exemplary embodiments of the present disclosure, an apparatus can be configured to translate or rotate the lens arrangement. In some exemplary embodiments of the present disclosure, an apparatus can be configured to deflect the third and fourth radiations. A wave-guiding arrangement can be provided in an optical path of the lens arrangement, which can include a fiber or a fiber bundle. A source apparatus can provide a radiation to the lens arrangement, and can include a wavelength tunable source(s) or a broadband source. In certain exemplary embodiments of the present disclosure, the detector apparatus can include a spectrometer. 
         [0023]    These and other objects, features and advantages of the exemplary embodiments of the present disclosure will become apparent upon reading the following detailed description of the exemplary embodiments of the present disclosure, when taken in conjunction with the appended paragraphs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0024]    Further objects, features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying drawings showing illustrative embodiments of the present disclosure, in which: 
           [0025]      FIG. 1  is a system diagram of an exemplary embodiment of a micron resolution Optical Coherence Tomography (μOCT) endoscopic-probe imaging platform according to the present disclosure; 
           [0026]      FIG. 2  is a side cross-sectional view of an exemplary internally referenced interferometric probe; 
           [0027]      FIG. 3A  is a side cross-sectional view of an input face of an exemplary GRIN fragment as experienced by the light traveling to the sample; 
           [0028]      FIG. 3B  is a side cross-sectional view of an output face of the GRIN lens as experienced by the light traveling to the sample; 
           [0029]      FIG. 3C  is a side cross-sectional view of an isomeric image of the exemplary GRIN lens, with deposited mirrors on input and output faces of the GRIN lens; 
           [0030]      FIG. 3D  is a ray-tracing diagram as being view through the side of the exemplary GRIN lens; and 
           [0031]      FIG. 4  is a diagram of a lens configuration composed of diffractive or refractive elements with reflective components to produce an internal interferometric reference. 
       
    
    
       [0032]    Throughout the figures, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components or portions of the illustrated embodiments. Moreover, while the subject description will now be described in detail with reference to the figures, it is done so in connection with the illustrative embodiments. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the subject disclosure. 
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0033]    An exemplary embodiment of an integrated μOCT system according to the present disclosure which includes an exemplary imaging platform and endoscopic probe is shown in  FIG. 1 . For example, as illustrated in  FIG. 1 , light or another electro-magnetic radiation provided from a broadband source  100  can be collimated by a lens  110 . A collimated beam provided from the lens  110  then passes through a beam splitter  120  before it is focused by another lens  130  unto a single-mode fiber-optic patch-cable  140  that transmits the light to a probe  150 . Probe  150  is mounted on a translational and/or rotational actuator  145  allowing for precision positioning of the probe tip and for the translation of the position of the probe tip in a desirable fashion during measurement. Probe  150  delivers the light or another electro-magnetic radiation to the target tissue  160 . Light reflected from the target tissue  160  is collected by the probe  150  and transmitted back through the single-mode optical fiber  140 . The reflected light or another electro-magnetic radiation is then collimated by the lens  130 , and then it passes through the beam splitter  120 . 
         [0034]    Further, the light beam or another electro-magnetic radiation can be separated to its spectral components by a diffraction grating  170 , that are then focused by lens  180  onto a detector (e.g., a detection array)  190 , thereby creating an A-line of interferometric information. Such information can be transmitted from the detector  190  to an image acquisition device  191  and then to one or more computers  192 , where data undergoes processing for display  195  and storage  194 . The computer(s)  192  can additionally output analog and/or digital signals  193  to control various parts of the exemplary system, including the light source  100 , the detection array  190 , and other peripheral devices not shown. 
         [0035]    The exemplary probe and the light/radiation path within the exemplary are shown in  FIG. 2 . In summary, light or another electro-magnetic radiation can be delivered to the probe via an optical fiber, and is shaped and delivered to the sample tissue at the right. The beam can be expanded by the spacer, and focused by two fragments of a gradient-index (GRIN) lens. The second GRIN lens fragment is selectively coated with spatially patterned mirrors on both ends to form a beam splitter and reference reflector. These two mirrors can be either fully reflective or partially reflective coated with a spectrally dependent c. An angled mirror turns the optical axis towards the side to be perpendicular to the axis of the probe. 
         [0036]    Particularly, in the exemplary probe, the light or other electro-magnetic radiation can emerge from a fiber  200 , and propagates as a first radiation  205  through a spacer  210 . The first radiation is partially focused by a first GRIN lens  215 , and then further focused by a second GRIN lens  220 . An output face of the second GRIN lens  220  can be at least partially covered by an apodizing reflector  230 . A beam diameter at this point can be larger than the diameter of the apodizing reflector  230 . A center part of the beam, designated the second radiation  217 , can be reflected back into the second GRIN lens  220 , while the light/radiation not redirected by the mirror  230  forms a third radiation  265 , which may be of annular shape as illustrated in  FIG. 4 . The third radiation is reflected by a 45-degree mirror  240 , and can be focused through a window  250  to the sample  260 . The light/radiation backscattered by the sample  260  can be incident on the second GRIN lens  220 , and can be recombined with light reflected from a reference mirror  270 , which can reach the apodizing reflector  230  at a second time. This returning light/radiation can contain an interference pattern, e.g., representing the reflectance of the sample  260  as a function of depth. The combined returning light/radiation can be focused by the second GRIN lens  220  and the first GRIN lens  215  back to the fiber  200 . 
         [0037]      FIGS. 3A-3D  illustrate exemplary diagrams of an exemplary GRIN lens fragment with deposited circular reflectors on each end face, according to exemplary embodiments of the present disclosure. In particular,  FIG. 3A  shows a cross-sectional diagram of an input face of the GRIN lens. For example,  FIG. 3A  illustrates the exemplary GRIN lens with the circular small reference reflector  320  deposited in a center of the face, e.g., concentric with the optical axis.  FIG. 3B  shows a cross-sectional diagram of an output face of the exemplary GRIN lens, and in its center, the circular larger apodizing reflector  320  can be provided concentric with the optical axis.  FIG. 3C  illustrates an isometric view of the exemplary GRIN lens providing both reflectors  310  and  320 .  FIG. 3D  shows a ray-tracing diagram of a two-dimensional cross section from the side of the exemplary GRIN lens. For example, a beam can enter from the input face on the left and travels through the GRIN lens. On the output face, the beam can be spatially split by the apodizing reflector  310 . The beams central part can be reflected back, while its rim would not be reflected, thus forming an annulus. The central part of the beam, having been reflected by the apodizing reflector  310 , can travel back to the input face of the GRIN lens, and can then be focused there onto the reference reflector  320 . 
         [0038]      FIG. 4  illustrates an exemplary diagram of a general lens arrangement with apodizing reflectors as in  FIG. 3 , but where the focusing elements can be diffractive or refractive lenses or any combination thereof. A first radiation  400  enters the lens arrangement and is partially focused or collimated by focusing optic  405 , which is composed of at least one diffractive or refractive element. The partially focused or collimated output radiation  410  continues to focusing optic  420 . A reflecting surface  435  present near the exit surface of  420  divides the radiation along two paths. One portion of the first radiation is reflected as a second radiation in a manner such that the second radiation traverses the focusing optic  420  in the reverse direction of the first radiation. A reflecting element  430  is placed near the focus of the second radiation, such that a larger portion of the second radiation energy is reflected than that of the first radiation. The portion of the first radiation that is not reflected by element  435  continues forward as a third radiation  425  towards the sample.  440  illustrates an exemplary intensity profile of the third radiation. 
         [0039]    The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. Indeed, the arrangements, systems and methods according to the exemplary embodiments of the present disclosure can be used with and/or implement any OCT system, OFDI system, SD-OCT system or other imaging systems, and for example with those described in International Patent Application PCT/US2004/029148, filed Sep. 8, 2004 which published as International Patent Publication No. WO 2005/047813 on May 26, 2005, U.S. patent application Ser. No. 11/266,779, filed Nov. 2, 2005 which published as U.S. Patent Publication No. 2006/0093276 on May 4, 2006, and U.S. patent application Ser. No. 10/501,276, filed Jul. 9, 2004 which published as U.S. Patent Publication No. 2005/0018201 on Jan. 27, 2005, and U.S. Patent Publication No. 2002/0122246, published on May 9, 2002, the disclosures of which are incorporated by reference herein in their entireties. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures which, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. In addition, all publications and references referred to above can be incorporated herein by reference in their entireties. It should be understood that the exemplary procedures described herein can be stored on any computer accessible medium, including a hard drive, RAM, ROM, removable disks, CD-ROM, memory sticks, etc., and executed by a processing arrangement and/or computing arrangement which can be and/or include a hardware processors, microprocessor, mini, macro, mainframe, etc., including a plurality and/or combination thereof. In addition, certain terms used in the present disclosure, including the specification, drawings and claims thereof, can be used synonymously in certain instances, including, but not limited to, e.g., data and information. It should be understood that, while these words, and/or other words that can be synonymous to one another, can be used synonymously herein, that there can be instances when such words can be intended to not be used synonymously. Further, to the extent that the prior art knowledge has not been explicitly incorporated by reference herein above, it can be explicitly being incorporated herein in its entirety. All publications referenced above can be incorporated herein by reference in their entireties.