Time-of-flight (TOF) range sensors acquire distances by means of an optical signal delay measurement. As the signal travels at the speed of light, distance resolutions in the subcentimeters range require a time measurement resolution that is in the picoseconds range. However, typical clock synthesizers and digital buffers possess cycle-to-cycle jitter values of up to hundreds of picoseconds, which can potentially have a noticeable impact on the TOF system performances. In this publication, we investigate the influence of two common types of cycle-to-cycle jitter distributions on the measured distance. This includes a random Gaussian distribution, which is caused by, e.g., stochastic noise sources, and a discrete jitter distribution, which is found when timing constraints fail in synchronous digital designs. It was demonstrated that a Gaussian cycle-to-cycle jitter has only a negligible impact on the performance of the TOF distance sensors up to a standard deviation of 1 ns of the Gaussian jitter distribution. However, even the discrete cycle-to-cycle jitter investigated in its simplest form lowers the distance precision of the TOF sensor by a factor of 2.86, i.e., the standard deviation increases from 2.9 to 8.3 mm.
A single-pixel sensor consisting of a dual-lock-in amplifier with an innovative dual-cathode photodetector is presented. The sensor is fabricated in 0.35 μm CMOS and is designed to be integrated in a multipixel array working with a frequency shifted feedback (FSF) laser. The realised single-pixel structure occupies an area of 120 × 100 μm² at a 58% fill factor. This pixel ensures frequency detection of the optical signal independently of its phase and power. The bandwidth of the interleaved pin photodiodes is larger than 100 MHz even for 850 nm. The sensor shows a dynamic range of ∼24 dB at a modulation frequency of 10 MHz. Signals up to 35 MHz can be detected.
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