Fundus Imaging using Aplanat

Rathod, Vishwanath Manik and Jana, Soumya (2018) Fundus Imaging using Aplanat. Masters thesis, Indian Institute of Technology Hyderabad.

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Retinal photography requires the use of a complex optical system called a fundus camera, capable of illuminating and imaging simultaneously. Because of restriction of aperture stop(pupil), available fundus imaging system suffer limited field of view. Hence peripheral area of retina remains undetected in traditional way. Also, system being prone to common aberrations always makes them to compromise with quality of image. In this thesis we propose a system that uses an aberration free reflector called Aplanat instead of the conventional lens system for the fundus imaging. So Imaging optics will be based on reflection unlike the convectional system which uses lens system and hence refraction principle which results in very negligible aberrations. Also, small reflector size makes it a hand-held system with minimum complexity and power loss for illumination purpose. Working under thermodynamic limit and high numerical aperture makes it possible to inject maximum light at wide angle inside eye which abolish the necessity of mydriasis. The optical system was designed in Zemax Optical Studio 15.5 in mixed sequential mode abilities by inserting aplanat as non sequential CAD object in sequential system comprised of eye and imaging sensor. CAD object was designed using Solid Edge ST8 using the Cartesian data points created in MATLAB. This solid object then imported to Zemax through CAD import ability. Present system propose 3 phase to image retina completely. A narrow throat aplanat for for some part close to optical axis leaving a small hole at optical axis. A wide throat aplanat to image peripheral area. a normal lens system that will cover the center hole. Exploiting overlapping part in the images from all the systems, stitching can be used to get the final complete image. Conjugate plane of retina found to be a curved surface and inside the aplanat which restricts us from using Zemax tool for the imaging purpose as it can not have of axis multiple sensor at desired location in align with conjugate of retina to sense ray bundle. Also, we loose smoothness and accuracy of reflector surface while im- porting the CAD object. So 3D image reconstruction of retina was performed in tool developed by project partner. All three phases covers almost 2000 wide field of retina which counts for 87% of the retina surface. Exploiting overlapping part in the images from all the systems, stitching can be used to get the final complete image.

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IITH Creators:
IITH CreatorsORCiD
Item Type: Thesis (Masters)
Uncontrolled Keywords: Aplanat, Fundu Cameza, wide-Field, image Formation, funds Photography
Subjects: Electrical Engineering
Divisions: Department of Electrical Engineering
Depositing User: Team Library
Date Deposited: 03 Jul 2018 05:59
Last Modified: 03 Jul 2018 05:59
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