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CN-116068533-B - Method for resisting noise of non-self-system laser source for DTOF image sensor

CN116068533BCN 116068533 BCN116068533 BCN 116068533BCN-116068533-B

Abstract

The invention discloses a method for resisting noise of a non-self system laser source for a DTOF image sensor, which comprises the steps that the laser source of the system emits optical pulse signals according to N working periods, a certain number of delay intervals are inserted between two adjacent working periods, the number of the delay intervals inserted between the two adjacent working periods is different, and the optical pulse signals of the N working periods after the delay intervals are accumulated on a histogram to form corresponding peaks. The system has the capability of suppressing the noise of the laser source of the system, and does not affect the accumulation of the laser source signal of the system, particularly, the system still has good suppressing effect under the condition that the conventional suppressing method fails to use the dichotomy and the quartering system, thereby fully avoiding the failure of the dichotomy and the quartering system, improving the signal-to-noise ratio of the system and improving the detecting distance and the accuracy of the system.

Inventors

  • NIE KAIMING
  • SUN MINGHAO
  • XIE JIYONG
  • XU JIANGTAO

Assignees

  • 天津大学合肥创新发展研究院

Dates

Publication Date
20260512
Application Date
20230208

Claims (10)

  1. 1. A method for resisting noise of a non-self system laser source for a DTOF image sensor, the method comprising: the laser source of the system emits light pulse signals according to N working periods; a certain number of delay intervals are inserted between two adjacent working periods, and the number of the delay intervals inserted between the two adjacent working periods is different; And accumulating the optical pulse signals of N working periods after the delay interval is inserted on the histogram to form corresponding peaks.
  2. 2. The method for resisting noise of non-self-system laser source for DTOF image sensor as recited in claim 1, wherein the total number of delay intervals inserted between N duty cycles and the length of each delay interval are constant.
  3. 3. The method for noise immunity to non-self-contained laser sources for a DTOF image sensor as recited in claim 1, wherein said inserting a number of delay intervals between adjacent two duty cycles comprises: And inserting N delay intervals between the nth working period and the (n+1) th working period, wherein N is more than or equal to 1 and less than or equal to N-1.
  4. 4. The method for noise immunity to non-self-contained laser sources for a DTOF image sensor as recited in claim 1, wherein said inserting a number of delay intervals between adjacent two duty cycles comprises: M 1 of the delay intervals are inserted between the nth and n+1th duty cycles, and m 2 of the delay intervals are inserted between the n+1th and n+2th duty cycles, where m 1 +m 2 =n.
  5. 5. The method for noise immunity to non-self-contained laser sources for a DTOF image sensor as recited in claim 1, wherein said inserting a number of delay intervals between adjacent two duty cycles comprises: Delay intervals of the numbers m n and m N-n are inserted at the nth interval and the N-nth interval, respectively, and m n +m N-n =n.
  6. 6. The method for resisting noise of non-self-system laser source for DTOF image sensor as claimed in claim 3, wherein the sum of more delays of each stage than the previous stage is taken as total dislocation delay, ta= (N-1) T is the delay interval, the total dislocation delay ta is more than or equal to MT, M is more than or equal to 2, and T is the working period.
  7. 7. A non-self system laser source noise resistant system for a DTOF image sensor, the system comprising: the laser source of the system is used for emitting optical pulse signals according to N working periods; the delay interval module is used for inserting a certain number of delay intervals between two adjacent working periods, and the number of the delay intervals inserted between the two adjacent working periods is different; And the receiving and quantizing module is used for accumulating the optical pulse signals of the N working periods inserted into the delay interval on the histogram to form corresponding peaks.
  8. 8. The non-self-contained system for a DTOF image sensor as recited in claim 7, wherein the total number of delay intervals interposed between N duty cycles and the length of each delay interval are constant.
  9. 9. The non-self system laser source noise resistant system for DTOF image sensor as recited in claim 7, wherein the delay interval module is specifically configured to: inserting N delay intervals between the nth working period and the (n+1) th working period, wherein N is more than or equal to 1 and less than or equal to N-1; Or inserting m 1 said delay intervals between the nth and n+1th duty cycles, and inserting m 2 said delay intervals between the n+1th and n+2th duty cycles, wherein m 1 +m 2 =n; Or delay intervals of the numbers m n and m N-n are inserted in the nth interval and the N-nth interval, respectively, and m n +m N-n =n.
  10. 10. The system of claim 7, wherein the delay interval module is configured to insert N delay intervals between the nth and the (n+1) th working cycles, wherein when 1≤n≤N-1, the sum of the delays of each stage more than the previous stage is taken as the total dislocation delay, ta= (N-1) T is the delay interval, the total dislocation delay ta is more than or equal to MT, M is more than or equal to 2, and T is the working period.

Description

Method for resisting noise of non-self-system laser source for DTOF image sensor Technical Field The invention relates to the technical field of TOF image sensors and circuits, in particular to a method for resisting noise of a non-self system laser source for a DTOF image sensor. Background Image sensors have been hot spots for human attention and research, but with the development of modern scientific technology, two-dimensional images cannot meet the needs of human beings, and more application scenes need to accurately sense distance information, so three-dimensional imaging technologies have been developed. The DTOF image sensor is a novel three-dimensional image sensor, and can realize long-distance high-precision multi-point distance imaging, thereby realizing 3D surface reconstruction of an object. The DTOF image sensor system is composed of a laser emitter, optical elements, a SPAD macro-pixel array, a pixel front-end circuit, a time-to-digital converter (Time to Digital Converter, TDC), a timing control circuit and some peripheral circuits. DTOF image sensors rely on measuring the time difference between the transmitted and received light pulses to calculate the distance between the target and the sensor, whose performance is limited by a number of noise, including dark noise, post-pulse noise, noise due to ambient light, and multi-peak noise due to multiple laser sources. The most deadly noise is multimodal noise caused by a plurality of non-self-system laser sources, the noise and the response form of the self-system laser sources to the self-system are the same, the accumulated noise and the response form of the self-system laser sources are all a series of signal peaks, the difference is that the positions of the signal peaks on a time axis are different, so that a TDC circuit has no way to distinguish which signal peak is the signal peak corresponding to the self-system laser sources, and the DTOF system is completely disabled. In order to distinguish the signal peaks corresponding to different laser sources, different laser sources can be encoded so as to generate peaks with encoded information, so that different peaks can be screened, the peaks corresponding to the light sources of the system are obtained, and the real distance is calculated. A simpler coding form is shown in figure 1, wherein the laser source of the system emits one pulse and emits a second pulse at a fixed time tn, so that the laser source of the system can generate two peaks, the time distance between the two peaks is the emission interval tn of the two pulses, the other laser sources can also generate two peaks at a distance tm, the distances between the two peaks generated by different laser sources are different, and the distance t between the different peaks can be identified after accumulation until the two peaks corresponding to the two pulses of the laser source are found. The above method is effective for a DTOF system of a histogram accumulation type, but the above method loses operability for a DTOF system of a time quantization method using a dichotomy, a quartering method, and the like, because the dichotomy and the quartering method and the like are only used for the process of counting pulse data, the data is not accumulated, no peak value in the result occurs, and the failure of the original coding method is caused, wherein the dichotomy quantization process is as shown in fig. 2, in each quantization, the currently quantized sign bit 0 or1 is obtained by comparing the pulse numbers of two intervals, and all sign bits are finally obtained as quantization code values by repeating the process. The traditional method is based on the fact that the code of a laser source signal and the accumulation of trigger signal pulses of the laser source signal are carried out for a plurality of times, so that the code is characterized, but the dichotomy and the quartering method do not support the accumulation of data, and therefore, the original method for inhibiting the noise of a light source of a non-self system based on the code of the laser source signal is invalid. In the related art, the Chinese patent application publication No. CN110632578A discloses a system and a method for measuring time-of-flight distance of time codes, wherein the system comprises a transmitter, a collector and a processing circuit, wherein the transmitter is configured to transmit an optical signal pulse string with double random time codes, the pulse string comprises N pulse groups transmitted in a second random time code form, the pulse groups comprise N pulses transmitted in a first random time code form, the collector is configured to collect photons in the optical signal pulse string reflected by an object, the processing circuit is connected with the transmitter and the collector and is configured to count the photons to form N pulse group period single photon count time sequence strings, and a histogram is drawn based on the first ra