Optimized position sensors for flying-spot active triangulation systems

Abstract

Permission is granted to quote short excerpts and to reproduce figures and tables from this report, provided that the source of such material is fully acknowledged. Optimized Position Sensors for Flying-Spot Active Triangulation Systems

Evaluating the performance of close-range 3D active vision systems for industrial design applications

“…Diffraction limits impose a constraint on the resolving power along the X and Y-axes as described above, but along the range axis (Z) one could expect a continuous improvement as the amount of laser power is increased or if smaller pixels are used on the position sensor [16]. Unfortunately this is not the case; indeed the coherence of the laser light produces damaging interference effects that limit the resolving power of a position sensor.…”

A CMOS sensor optimized for laser spot-position detection

“…The basic idea underlying the design of the sensor has already been considered by Beraldin et al in [13] and [20]. The novelty of the sensor is that of defining, for readout, only a region of interest window (ROI) around the real position of the spot, according to the estimate provided by a low resolution, but fast position detector.…”

“…The photodetector, as well as analog signal conditioning, timing control, analog to digital conversion and digital processing can be integrated on the same silicon substrate using standard microelectronic technologies. Two different types of photodetectors can be considered for integration: lateral effect photodiodes (LEP) [or continuous response position sensor (CRPS)] and discrete response position sensors (DRPS) [20], i.e., linear array of photodetectors. The former are analog detectors working as photoresistor and have been extensively studied in the past [6]- [9].…”

“…These sensors are currently used in state of the art flying-spot 3-D camera rangers [10], [20]. They allow for the recovery of the full shape of the light distribution on the photosensitive area and are, therefore, very accurate, but suffer for speckle-limited spot-position detection [11] and readout speed.…”

“…The former is due to the continuous decrease in size of the single photodetectors. Commercial devices, in fact, are thought for imaging applications [20] where only the number of photodetectors within the array is important leading, therefore, to a minimum size of photodiode in the order of a few microns. Speed is the second issue of DRPS.…”