A laser diffraction measuring system for submicron pixel size image sensor

Abstract

This paper reports a laser diffraction measuring system based on a lab made 26M (5120×5120) pixels image sensor with a pixel pitch of 0.95μm. The long distance required in the traditional method to match the surface of the image sensor with large pixels is shortened, and the image sensor with submicron pixels becomes the key to capture the patterns at short range which is still meet the condition of fraunhofer approximation. The system refers to using a digital optoelectronic sensor array to sample the light transmitted through a specimen without the use of any imaging lenses between the object and the sensor planes. The hardware for such an imaging geometry is significantly simpler and much more compact and lightweight than that of conventional measuring system. In addition, an algorithm of image processing, termed super resolution image reconstruction, is used to further improve the resolution and is required to achieve subpixel spatial resolution in measuring system. In the experimental measurement, the final result can reach the accuracy of 0.98%.