Abstract
In this article, we describe several enhancements of a three-phase correlation image sensor (3PCIS) toward its uses for a direct algebraic method of optical flow detection, i.e., determining velocity field of image patterns for detecting, tracking, and three-dimensional recovery of objects in a scene. A recent theoretical study has provided an exact closed-form solution of the velocity from temporal Fourier integral measurements of a time-varying intensity distribution. An accurate analog multiplication and integration of incident light and reference signals required for this type of measurements is the inherent advantage of a 3PCIS. We fabricate and compare several types of correlation detection block. As continuous-value inputs of the algebraic solution, compensation operations of systematic sources of error are so designed to realize a near shot-noise-limited performance. For random telegraph noise and interference reduction, we show that a p-epi channel, deep p-well structure is the best 3P multiplier. Several experimental results of optical flow detection including an accuracy evaluation and the dense motion capture of a traffic scene are given.
Highlights
The three-phase correlation image sensor (3PCIS) [1] is a device that simultaneously produces the temporal integrals of incident light f (r, t) on pixel coordinate r = (x, y) with and without the orthogonal reference signal wn(t) as gn(r) = f (r, t)wn(t)dt, g0(r) = f (r, t)dt (1)
DEVICE STRUCTURE The 3PCIS we describe here is composed of a 704×512 array of black-and-white, 12×12 μm2 correlation detection pixels with Bayer-arrayed 3P reference signals, and 120 fps max, triple CMOS readout lines, which are built using 0.18 μm CMOS image sensor process
This means that the noise variances of the intensity and correlation in electron counts are equal to the total electron count
Summary
The optical flow is the two-dimensional velocity field that describes the translational motion of image intensity distribution It has been widely studied, motivated by a broad range of applications such as the detection, tracking, and three-dimensional recovery of objects in a scene [19], [21], [22], [23]. In the range of velocity and accuracy due to an approximation of temporal differential using two consecutive frames In this respect, the combination of a 3PCIS and the WIM offers an effective and straightforward approach because the WIM provides an exact closed-form solution of the velocity from Fourier integral measurements (see Appendix A). The purpose of this study is to obtain a sufficient accuracy and signal-to-noise ratio (SNR) of pixel outputs and subsequent compensation operations suitable for optical flow detection required in automotive and traffic scene analysis. Several experimental results of optical flow detection are given including the dense motion capture of a traffic scene
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