The company's 135-page patent application WO2016120392 "Detector for an optical detection of at least one object" by Sebastian Valouch, Ingmar Bruder, Robert Send, Christoph Lungenschmied, Wilfried Hermes, Erwin Thiel, and Stephan Irle gives quite a detailed overview of the imager:
"According to the so-called "FiP effect", the sensor signal, given the same total power of the illumination, is hereby dependent on a geometry of the illumination, in particular on a beam cross-section of the illumination on the sensor region.
Given the same total power of the illumination, the electrical conductivity of the sensor region, therefore, depends on the beam cross-section of the light beam in the sensor region, be denominated as a "spot size" generated by the incident beam within the sensor region. Thus, the observable property that the electrical conductivity of the photoconductive material depends on an extent of the illumination of the sensor region comprising the photoconductive material by an incident light beam particularly accomplishes that two light beams comprising the same total power but generating different spot sizes on the sensor region provide different values for the electrical conductivity of the photoconductive material in the sensor region and are, consequently, distinguishable with respect to each other.
Further, since the beam cross-section of the light beam in the sensor region, according to the above-mentioned FiP effect, given the same total power of the illumination, depends on the longitudinal position or depth of an object which emits or reflects the light beam which impinges on the sensor region, the longitudinal optical sensor may, therefore, be applied to determining a longitudinal position of the respective object."
"Figures 4 A to D show experimental results of further measurements in which the sensor region 130 of the longitudinal optical sensor 1 14 comprised lead sulfide (PbS) as the photoconductive material 134. Again, the setup of the optical detector 110 comprised a green light-emitting diode (LED) 158 which was placed 80 cm in front of the refractive lens 122 and which was, again, simultaneously employed as both the illumination source 156 for the optical wavelength of 530 nm and the object 112. The longitudinal optical sensor 1 14 with the photoconductive material 134 lead sulfide (PbS) was operated under a 10 V bias voltage provided by the bias voltage source 150. In this particular experiment, the light-emitting diode 158 was again used as the illumination source 156 which was modulated with a modulation frequency by means of the modulation device 162, wherein, however in contrast to the experiments as performed according to Figures 3A to C, different values for one of the photocurrent and the modulation frequency were applied. Consequently, the longitudinal sensor signal was, again, measured by using the lock-in amplifier 164."
