The resolution dependence of spatial-spectral volume holographic imaging systems on angular and spectral bandwidth of non-uniform gratings is investigated. Modeling techniques include a combination of the approximate coupled wave analysis and transfer matrix methods for holograms recorded in absorptive medium. The effective thickness of the holograms is used as an estimator of the resolution of the imaging systems. The methodology presented here assists in the design and optimization of volume holographic Simulation results based on our approach are confirmed with experiments and show proof of consistency and usefulness of the proposed models.
We present the design for an endoscopic system capable of imaging tissues of the ovary at two selected imaging depths simultaneously. The method utilizes a multiplexed volume hologram to select wavefronts from different depths within the tissue. It is the first demonstration of an endoscopic volume holographic imaging system. The endoscope uses both gradient index (GRIN) optical components and off the shelf singlet lenses to relay an image from the distal tip to the proximal end. The endoscope has a minimum diameter of 3.75 mm. The system length is 30 cm which is connected to a handle that includes the holographic components and optics that relay the image to a camera. Preliminary evaluation of the endoscope was performed with tissue phantoms and calibrated targets, which shows lateral resolution ≈ 4 μm at an operating wavelength of 660 nm. The hologram is recorded in phenanthraquinone doped poly methacrylate and is designed to produce images from two tissue depths. One image is obtained at the tissue surface and the second 70 μm below the surface. This method requires no mechanical scanning and acquires an image at the camera frame rate. The preliminary ex-vivo results show good correlation with histology sections of the same tissue sections.
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