Time-of-Flight Based Pixel Architecture with Integrated Double- Cathode Photodetector

摘要

For various industrial applications contact-less optical 3D distance measurement systems with active illumination are suitable. A new approach for a pixel of such a 3D-camera chip for applications in displacement and 3D-shape measurement is presented here. The distance information is gained by measuring the Time-of-Flight (TOF) of photons transmitted by a modulated light source to a diffuse reflecting object and back to the receiver IC. The receiver is implemented as an opto-electronic integrated circuit (OEIC). It consists of a double-cathode photodetector performing an opto-electronic correlation, a decoupling network and an output low-pass filter on a single silicon chip. The correlation of the received optical signal and the electronic modulation signal enables the determination of the phase-shift between them. The phase-shift is directly proportional to the distance of the object. The measurement time for a single distance measurement is 20 ms for a range up to 6.2 m. The standard deviation up to 3.4 m is better than lcm for a transmitted optical power of 1.2 Mw at a wavelength of 650 nm. The OEIC was fabricated in a slightly modified 0.6 μm BiCMOS technology with a PIN-photodetector. The photosensitive area of the integrated PIN-photodetector is 120×115 μm~2. A fill factor of ～67 % is reached.