Time depth camera and multi-frequency modulation and demodulation distance measurement method for reducing noise

Abstract

The invention provides a time depth camera and a multi-frequency modulation and demodulation distance measurement method for reducing noise. The time depth camera comprises: an emission module including a light source used for emitting a pulse light beam to an object to be measured; an acquisition module including an image sensor formed by at least one pixel, each pixel comprising at least three taps, and the taps being used for acquiring charge signals generated by the reflected pulse beams reflected by the object to be measured and / or charge signals of background light; and a processing circuit used for controlling the at least three taps to alternately acquire the charge signals among the at least three frame periods of a macrocycle, adopting different modulation and demodulation frequencies in every two adjacent macrocycles, and receiving data of the charge signals received in the two adjacent macrocycles to calculate the flight time of the pulse light beam and / or the distance of the object to be measured. The extension of the measurement distance is no longer limited by the pulse width, the fixed noise caused by mismatch between taps or between readout circuits due to processmanufacturing errors and the like is reduced or eliminated.

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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