A new edge detection method based on nonlinear fitting is used in the measurement of the curvature of lens in this paper. Non-contact Newton's rings are formed by an interferometer. In order to detect the diameters of dark rings and calculate the lens radius of curvature, the edge detection method is used for the image process. The auto-measuring system of lens curvature captures the gray scale image by CMOS image sensor, and then processes the data and calculates the position by a microprocessor. The scale of image pixels corresponding to Newton's rings that are related to the radius of curvature is obtained by scanning fringes or other optical methods. The accuracy of measurement is better than 0.3 percent.
Implementation of a 4 by 1 comb-type Position sensitive detector (PSD) array for position sensing applications is presented. Unlike conventional application, we utilize the method of subdivision to increase the resolution of PSD beyond the feature of photosensitive area, which is presented periodically. To obtain output signal of comb-type PSD, classic grating subdivision circuit is used. Resolution of 6.25μm of comb-type PSD is achieved using optical grating array of a 50μm in pitch and signal power of 3mW. The resolution is limited by the spacing of comb-type PSD and the mismatch of position of PSD array and optical grating array.
Position Sensitive Detector (PSD) is a position sensor utilizing the lateral photoelectric effect produced by the non-uniform illumination of a rectifying semiconductor junction. Recently, mostly researches of PSD focus on the linear requirements or response characters of PSD with p-n junction. However, this paper concentrates on a novel characteristics of PSD based on the Schottky junction. This junction has many distinguished traits comparing with the p-n junction. Since the intrinsic excellent characteristics, the Schottky PSD has faster response and higher sensitivity to the incident radiation, lager current density, low current leakage and so on. This paper provides an analysis and model of the Schottky-barrier PSD lateral potential creation, response characteristic and position linearity condition with the Schottky junction, which is deduced by the charge conversation law and the model of carriers transport. All the study work is the theoretical basis for design of this junction with better performance.