PROCEEDINGS ARTICLE | May 23, 2013
Proc. SPIE. 8791, Videometrics, Range Imaging, and Applications XII; and Automated Visual Inspection
KEYWORDS: Clocks, Modulation, Cameras, Sensors, Phase shift keying, Field programmable gate arrays, Stereoscopic cameras, Distance measurement, Evolutionary algorithms, Phase shifts
Time-of-Flight (TOF) 3D cameras determine the distance information by means of a propagation delay measurement. The delay value is acquired by correlating the sent and received continuous wave signals in discrete phase delay steps. To reduce the measurement time as well as the resources required for signal processing, the number of phase steps can be decreased. However, such a change results in the arising of a crucial systematic distance dependent distance error. In the present publication we investigate this phase dependent error systematically by means of a fiber based measurement setup. Furthermore, the phase shift is varied with an electrical delay line device rather than by moving an object in front of the camera. This procedure allows investigating the above mentioned phase dependent error isolated from other error sources, as, e.g., the amplitude dependent error. In other publications this error is corrected by means of a look-up table stored in a memory device. In our paper we demonstrate an analytical correction method that dramatically minimizes the demanded memory size. For four phase steps, this approach reduces the error dramatically by 89.4 % to 13.5 mm at a modulation frequency of 12.5 MHz. For 20.0 MHz, a reduction of 86.8 % to 11.5 mm could be achieved.
