Towards Developing a Scanning Position Sensitive Detector (PSD) Microscopy: PSD Measurement Enhancement, Adaptive Local Scanning and Implementation
AuthorRahimi, Seyed M.
Electrical and Biomedical Engineering
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A Position Sensitive Detector/Device (PSD) is a sensor that is capable of trackingthe location of a laser beam on its surface. PSDs are used in many scientific instrumentsand technical applications including but not limited to: Atomic-force microscopy(AFM), human eye movement monitoring, mirrors or machine tool alignment, vibrationanalysis, beam position control and so on. This work intends to propose a newapplication using the PSD. That is a new microscopy system called scanning PSDmicroscopy. The working mechanism is about putting an object on the surface ofthe PSD and fast scanning its area with a laser beam. To achieve a high degree ofaccuracy and precision, a reliable framework was designed using the PSD. In thiswork, we first tried to improve the PSD reading and its measurement performance.This was done by minimizing the effects of noise, distortion and other disturbingparameters. After achieving a high degree of confidence, the microscopy system canbe implemented based on the improved PSD measurement performance. Later toimprove the scanning efficiency, we developed an adaptive local scanning system toscan the whole area of the PSD in a short matter of time. It was validated that ourcomprehensive and adaptive local scanning method can shorten the scanning time inorder of hundreds of times in comparison to the traditional raster scanning withoutlosing any important information about the scanned 2D objects. This developedmethod, would allow to scan the surface of the PSD by using square-shaped blocks oflight instead of a single point of the laser beam. Methods are also introduced to scanvery complicated objects with bifurcations and crossings. By incorporating all thesemethods, the new microscopy system is capable of scanning very complicated objectsin the matter of a few seconds with a resolution that is in order of a few micrometers.