Real-time range sensing with a Scheimpflug camera and a single custom sensor/processor chip

Abstract

An image-based range sensing technique is presented. The technique is originally considered for highway collision avoidance applications but its generality makes it suitable for application in robotics, manufacturing and metrology as well. It relies on depth from focus but, unlike conventional techniques, it extracts range with a single unmodulated Scheimpflug camera in continuous time. The range extraction algorithm is memoryless and simple enough to be implemented on the same chip with photosensors. The technique deploys a sensor plane that is tilted at a non-orthogonal angle with respect to the optical axis of the lens, and the optical axis intersects the sensor plane at the focal point. This optical arrangement creates a focusable object plane in an orientation parallel to the optical axis, and thus, enables range sensing along the same axis. The paper elaborates on the details of focus sensing on the tilted sensor plane, describes the CMOS sensor/processor chip designed and prototyped for this application, and presents experimental results.