An analog motion field detection chip for image segmentation

In this paper, we propose an analog integrated circuit to compute the motion field of a time-varying image by means of a multiple-constraint method. The chip converts optical input to electrical form with an array of on-chip image sensors. A resistive network is used to smooth the input image. The spatial and temporal derivatives of the image are used to compute the optical-flow constraint. An array of motion cells enforce the optical-flow constraints, and two nonlinear resistive networks enforce the smoothness constraint over the optical-flow field. In order to preserve object boundaries, the smoothness constraint must be adjusted according to discontinuities in the optical-flow field and edges in the image. This is achieved by the nonlinear nature of the resistors and by adjusting the conductance of the resistors according to spatial gradients of image intensity. A 32 32 optical-flow based motion field detection chip is fabricated using a 0.5m CMOS process. Measurement results show that the proposed IC can compute the optical-flow field in a scene efficiently and correctly so as to facilitate segmentation of moving objects in image sequences.