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Improving Resolution in Lensless Holographic Imaging

Doosthoseini, Amir Hossein | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51793 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Amini, Arash; Kavehvash, Zahra
  7. Abstract:
  8. High-resolution microscopy with the high field of view is necessary for a lot of applications related to medical studies in different areas and to reach this goal, Imaging Systems with high space bandwidth is required. Since CMOS and CCD image sensors are used for capturing digital images, the large amount of studies has been dedicated to optics and signal processing in order to achieve high resolution and the high field of view images.In lens-based imaging systems, large space-bandwidth is achieved through large lenses with higher magnification and larger image sensors with more number of pixels. The drawback of this methods is using larger optic components that lead to increased cost and bulkiness of imaging system. Therefore, The interests of lensless imaging systems have been increased. In this methods, The images are made based on the recorded holograms and reconstruction algorithms. The major limitation of this method is low resolution of output images because of diffraction limit and pixel size of the detector. In order to overcome this limitation a large amount of research has been done in super-resolution holographic imaging. In this thesis, we have proposed two structures for lensless imaging. the first method tries to improve lateral resolution and uses the synthetic aperture structure. In this method the source frequency is constant and source location changes on a spherical surface and the object is assumed 2D. The second method is for improving depth resolution or in fact achieving images from the depth of a 3D object. In the related structure, the source location is fixed however the frequency varies in the range of optics frequency. The simulation results indicate that both of the proposed methods reconstruct the images with the low number of data and presence of noise. Also, They improve the resolution of the lateral and depth directions
  9. Keywords:
  10. Lensless Imaging ; Lateral Resolution ; Depth Resolution ; Synthetic Aperture ; Diffraction Limit ; Holography

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