We describe a heterodyne interferometry system based on a complementary metal-oxide semiconductor digital signal processor (CMOS-DSP) camera that is utilized for full-field optical phase measurement using a carrier-based phase retrieval algorithm, with no need for electro-mechanical scanning. Camera characterization test results support the adoption of a single-pixel approach to perform quasi-instantaneous differential phase measurements, which are immune to mechanical vibrations and thermal drifts. We developed an optical configuration based on a Mach-Zehnder heterodyne interferometer to perform a static test on a mirror surface. The profiles of the mirror surface set at two angular positions, the relative displacements in the range of nanometers, and the corresponding tilt angle were determined.
This investigation describes the implementation of a Single Pixel Carrier Based Demodulation (SPCBD) approach on a digital CMOS-DSP camera for full-field heterodyne interferometry. A full-field vibration measurement system is presented as an alternative to a classical scanning Laser Doppler Vibrometer (LDV). The Heterodyne set-up, CMOS-DSP camera and the signal demodulation techniques adopted are described. Characterisation tests that describe the basic performance of the CMOS-DSP camera, in terms of acquisition rates and time response are presented. A simple experiment was performed to demonstrate the novel laser vibrometry system that consisted of determining the displacement of a point on the surface of a vibrating mirror. The measured velocity and displacement data were compared to the output from a commercial LDV. The integration of a CMOS sensor, DSP and a laser-doppler interferometer has lead to the development of a fully digital “functional” machine vision system that provides a flexible, compact and inexpensive tool for automated high-precision optical measurements.
This study concerns the application of a novel digital CMOS-DSP camera in full-field interferometry for vibration analysis and quasi real time processing in optical metrology. Characterisation tests on the digital camera have been performed. Both quasi-static and carrier-based approaches have been considered and will be presented in this paper. The CMOS-DSP camera is a primary component of a compact and low cost system for classical image processing and an innovative element for full field vibration measurement using a single pixel carrier based approach.