B. Büttgen, T. Oggier, M. Lehmann
Feb 2, 2006
Journal name not available for this finding
Optical time-of-flight (TOF) distance measurements can be performed using so-called smart lock-in pixels. By sampling the optical signal 2, 4 or n times in each pixel synchronously with the modulation frequency, the phase between the emitted and reflected signal is extracted and the object's distance is determined. The high integration-level of such lock-in pixels enables the real-time acquisition of the three-dimensional environment without using any moving mechanical components. A novel design of the 2-tap lock-in pixel in a 0.6 μm semiconductor technology is presented. The pixel was implemented on a sensor with QCIF resolution. The optimized pixel design allows for high-speed operation of the device, resulting in a nearly-optimum demodulation performance and precise distance measurements which are almost exclusively limited by photon shot noise. In-pixel background-light suppression allows the sensor to be operated in an outdoor environment with sunlight incidence. The highly complex pixel functionality of the sensor was successfully demonstrated on the new SwissRanger SR3000 3D-TOF camera design. Distance resolutions in the millimeter range have been achieved while the camera is operating with frame rates of more than 20Hz.