New optical four-quadrant phase detector integrated into a photogate array for small and precise 3D cameras

摘要

Abstract: The photonic mixer device (PMD) is a new electro-optical mixing semiconductor device. Integrated into a line or an array it may contribute a significant improvement in developing an extremely fast, flexible, robust and low cost 3D-solid-state camera. Three dimensional (3D)-cameras are of dramatically increasing interest in industrial automation, especially for production integrated quality control, in- house navigation, etc. The type of 3D-camera here under consideration is based on the principle of time-of-flight respectively phase delay of surface reflected echoes of rf- modulated light. In contrast to 3D-laser radars there is no scanner required since the whole 3D-scene is illuminated simultaneously using intensity-modulated incoherent light, e.g. in the 10 to 1000 MHz range. The rf-modulated light reflected from the 3D-scene represents the total depth information within the local delay of the back scattered phase front. If this incoming wave front is again rf- modulated by a 2D-mixer within the whole receiving aperture we get a quasi-stationary rf-inference pattern respectively rf-interferogram which may be captured by means of a conventional CCD-camera. This procedure is called rf- modulation interferometry (RFMI). Corresponding to first simulative results the new PMD-array will be appropriate to the RFMI-procedure. Though looking like a modified CCD-array or CMOS-photodetector array it will be able to perform both, the pixelwise mixing process for phase delay respectively depth evaluation and the pixelwise light intensity acquisition for gray level or color evaluation. Further advantageous properties are achieved by means of a four- quadrant (4Q)-PMD array which operates as a balanced inphase/quadrature phase (I/Q)-mixer and will be able to capture the total 3D-scene information of several 100,000 voxels within the $mu@s- to ms-range. !23