Moire Doppler Effect: Application to Single-frame Imaging Velocimetry of Range Motion

Abstract

A novel method for imaging velocimetry of range motion distribution is proposed. It is based on what we call “moire Doppler effect” and frequency estimation on each pixel. We project a grating pattern translating laterally with a constant speed. Every point on the object illuminated by it returns a sinusoidally varying intensity, and is detected by the Correlation Image Sensor (CIS). In this setup, a range motion of the object causes a frequency shift of the light intensity proportional to its velocity. We formulate this phenomena as the moire Doppler effect. The CIS can produce the Fourier coefficients of incoming light at up to three frequencies. From them, the frequency shift can be calculated by using the exact algebraic method, and thus the velocity can be estimated in each pixel. Several experiments were done to quantify the moire Doppler effect. A real-time measurement system was constructed which showed a feasible performance of the imaging velocimetry of range motion.