Direct read-out CMOS camera with applications to full-field optical coherence tomography

Abstract

A comprehensive characterisation of a complementary metal-oxide semiconductor (CMOS) and digital signal processor (DSP) camera, used typically in machine vision applications, is presented in this paper. The camera consists of a direct read-out CMOS sensor, each pixel giving a direct analogue voltage output related to light intensity, with an analogue-to-digital converter and digital signal processor on the back-end. The camera operates as a stand-alone device using a VGA display; code being pre-programmed to the onboard random access memory of the DSP. High detection rates (kHz) on multiple pixels were achieved, and the relationship between pixel response time and light intensity was quantified. The CMOS sensor, with 1024x1024 pixels randomly addressable in space and time, demonstrated a dynamic logarithmic light intensity sensitivity range of 120dB. Integrating the CMOS camera with a low coherence Michelson interferometer, optical coherence tomography (OCT) axial depth scans have been acquired. The intended application is an imaging device for simple yet functional full-field optical coherence tomography. The advantages of the CMOS sensor are the potential for carrier-based detection, through the very fast pixel response with under-sampling, and the elimination of the electromechanical lateral scanning of conventional OCT by replacing it with electronic pixel scanning.