Noise-reduced distance measurement method based on time-depth camera and multi-frequency modulation and demodulation

Abstract

The invention provides a time-depth camera and a noise-reducing distance measurement method of multi-frequency modulation and demodulation. The depth camera includes: a transmitting module, including a light source for emitting pulsed beams to an object to be measured; an acquisition module, including at least one An image sensor composed of pixels, each pixel including at least 3 taps, the taps are used to collect the charge signal generated by the reflected pulse beam reflected by the object to be measured and / or the charge signal of the background light; the processing circuit is used to control at least The 3 taps collect the charge signal alternately between at least 3 frame periods of the macro period, adopt different modulation and demodulation frequencies in the two adjacent macro periods, and receive the charge signals received in the two adjacent macro periods data to calculate the time-of-flight of the pulsed beam and / or the distance to the object under test. The expansion of the measurement distance is no longer limited by the pulse width, reducing or eliminating the fixed noise caused by the mismatch between the taps or between the readout circuits caused by the process manufacturing error.

Description

technical field [0001] The invention relates to the technical field of optical measurement, in particular to a time-depth camera and a noise-reducing distance measurement method for multi-frequency modulation and demodulation. Background technique [0002] The full name of ToF is Time-of-Flight, that is, time of flight. The ToF ranging method is a technology that achieves precise ranging by measuring the round-trip flight time of light pulses between the transmitting / receiving device and the target object. In ToF technology, the technology of directly measuring the time of flight of light is called dToF (direct-TOF); the emitted optical signal is periodically modulated, and the phase delay of the reflected optical signal relative to the emitted optical signal is measured, and then by The measurement technology for calculating the time of flight by phase delay is called iToF (Indirect-TOF) technology. According to different modulation and demodulation methods, it can be divi...

AI Technical Summary

Problems solved by technology

[0003] At present, CW-iToF technology is mainly used in measurement systems based on two-tap sensors. The core measurement algorithm is a four-phase modulation and demodulation method, which requires at least two exposures (in order to ensure measurement accuracy, four exposures are usually required ) to complete the acquisition of four phase data and output a frame of depth image, so it is difficult to obtain a higher frame rate

PM-iToF modulation technology is mainly used in four-tap pixel sensors (three taps are used for signal acquisition and output, and one tap is used to release invalid electrons). The measurement distance of this measurement method is currently limited by the modulation and demodulation signal When long-distance measurement is required, the pulse width of the modulation and demodulation signal needs to be extended, and the extension of the pulse width of the modulation and demodulation signal will lead to an increase in power consumption and a decrease in measurement accuracy

[0004] In addition, for multi-tap pixel sensors, there is often a mismatch between the taps or between the readout circuits due to process manufacturing errors, etc., thereby introducing fixed-pattern noise (FPN), which further affects the measurement accuracy.

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