Noise-reduced distance measurement method based on time-of-flight depth camera and single-frequency modulation and demodulation

Abstract

The invention provides a time-of-flight depth camera and a noise-reducing distance measurement method of single-frequency modulation and demodulation. The time-of-flight depth camera includes: a transmitting module, including a light source, used to emit pulsed beams to an object to be measured; an acquisition module, An image sensor consisting of at least one pixel, each of which includes at least 3 taps, the taps are used to collect the charge signal and / or background light generated by the reflected pulse beam reflected back by the object to be tested Charge signal; processing circuit, used to control at least 3 taps to collect the charge signal alternately between at least 3 frame periods of the macro period, and receive the data of the charge signal to calculate the flight time and / or of the pulsed beam The distance of the object to be tested. The expansion of the measurement distance is no longer limited by the pulse width, and the tap rotation acquisition method is used to reduce or eliminate the fixed noise caused by the mismatch between the taps or between the readout circuits due to process manufacturing errors and other reasons.

Description

technical field [0001] The invention relates to the technical field of optical measurement, in particular to a time-of-flight depth camera and a noise-reducing distance measurement method for single-frequency modulation. 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 divided in...

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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