A method for quickly calibrating a TOF module

Abstract

The present invention discloses a method for quickly calibrating a TOF module, the method comprising: S1, delaying the light signal of the TOF module light source; S2, the reflected light reaches a plurality of pixel points on the TOF module sensor; S3, pixel point calibration; S4, determining the relationship constant between pixel correspondence and distance; S5, performing distance calibration and compensation. The method has a small amount of calculation and a small error, and can be widely used for calibration of various applications of TOF modules.

Description

Technical Field

[0001] The present invention belongs to the technical field of TOF, and in particular relates to a method for quickly calibrating a TOF module. Background Art

[0002] With the development of LiDAR technology, the technology based on TOF (Time of Flight) modules has gradually matured and has begun to be applied in the fields of three-dimensional ranging, work automation, security, and automobiles. Its basic principle is to capture images by measuring the flight time of photons. Since the flight time of photons is extremely short, usually 30cm / ns, if you want to achieve this centimeter-distance resolution and accuracy, you must achieve a time measurement accuracy of 30 picoseconds. This is a very demanding requirement, especially when tens of thousands of pixels have to provide dozens of such precise measurements per second at the same time. Therefore, the calibration of the TOF module is particularly important.

[0003] In the prior art, due to the differences between different pixels on the depth sensor of the TOF module, there is a deviation in distance measurement, which is one of the main sources of error in the TOF module.

[0004] A Chinese invention patent with application number 201810896521.8 discloses a "TOF depth camera distance calibration method and device". The calibration method can solve the problem of differences between pixels and keep each pixel consistent within the measurement range of the TOF depth camera. However, the calculation is large and the calibration process defaults to an ideal state without a lens, which makes the actual measurement results inaccurate. Summary of the invention

[0005] Based on the above problems, the present invention provides a method for quickly calibrating a TOF module, comprising the following calibration steps:

[0006] S1: Delay processing of the optical signal of the TOF module light source;

[0007] S2: The reflected light reaches multiple pixels on the TOF module sensor;

[0008] S3: pixel calibration;

[0009] S4: Determine the relationship constant between pixel correspondence and distance;

[0010] S5: Perform distance calibration and compensation.

[0011] As a further illustration of the above solution, in step S3, the pixel calibration adopts a non-uniformity calibration algorithm to make the pixels in different spatial domains tend to be uniform and the response rate of each pixel is basically consistent.

[0012] As a further explanation of the above solution, in step S4, when determining the relationship constant between pixel correspondence and distance, a curve may be fitted using a central pixel for multiple different delay amounts.

[0013] As a further illustration of the above solution, in the step S5, in actual measurement, the distance calibration and compensation can be performed using a single pixel and a constant after the non-uniformity calibration.

[0014] As a further explanation of the above scheme, in step S1, the optical signal of the TOF module light source is delayed, and a delay circuit can be used to delay the light source modulation clock signal of the TOF module, and the delayed light source modulation clock signal is used to drive the light source to emit an optical signal.

[0015] The beneficial effects of the present invention are as follows: the deviation in distance measurement of the depth camera caused by the difference between different pixels on the depth sensor can be eliminated, the amount of calculation is small, the actual error is small, and the present invention is generally applicable to actual measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a method for calibrating a TOF module according to an embodiment of the present invention;

[0017] Figure 2 This is the optical path diagram of the calibration process;

[0018] Figure 3 It is the spatial distribution diagram of light intensity on the reflecting surface.

[0019] Description of reference numerals:

[0020] 1: LiDAR; 2. Reflective surface. DETAILED DESCRIPTION

[0021] In order to make the method of the present invention clearer, the present invention is further described below with reference to examples.

[0022] Combination Figure 1 , Figure 2 and Figure 3 , a solution for quickly calibrating the TOF module can be implemented in the following steps:

[0023] S10, delaying the light source modulation clock signal of the TOF module through a delay circuit, and using the delayed light source modulation clock signal to drive the laser radar 1 to emit a light signal. This step effectively reduces the space requirements.

[0024] S20, the emitted light signal is reflected by the reflective surface 2 to multiple pixels on the TOF group sensor to improve the accuracy of the distance measurement of the TOF module. The sensor receives the phase difference of the reflected light: Where Q1, Q2, Q3, and Q4 represent ADC (analog-to-digital converter) values ​​of different phases.

[0025] S30, according to the special non-uniformity calibration algorithm, makes the pixels in different spatial domains tend to be uniform, and the response rate of each pixel is basically the same. The original calculated value of the test distance is:

[0026]

[0027] Where, d is the test distance; c is the speed of light; f is the modulation frequency; Q1, Q2, Q3, Q4—represent the ADC values ​​of different phases.

[0028] S40, using a central pixel, fitting a curve for a plurality of different delay amounts, i.e., different distances, to obtain a constant k of the relationship between pixel responsivity and distance;

[0029] S50, in actual measurement, after non-uniform calibration, distance calibration and compensation are performed using a single pixel and a constant k.

[0030] Beneficial effects of this embodiment: After the TOF module is non-uniformly calibrated, this embodiment uses one pixel point to calibrate and compensate for the distance error. Compared with the prior art, it not only greatly reduces the amount of calculation and can quickly calibrate the TOF module; it can also eliminate the actual error caused by the lack of a lens in the existing calibration process. The calibrated TOF module can be directly used in actual measurements.

[0031] The above embodiment is only one of the practical applications of the present invention and does not limit the scope of application of the present invention. Those skilled in the art should know that all modifications, replacements and improvements based on the expansion of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for quickly calibrating a TOF module, characterized in that: The calibration steps include: S1: Delay processing of the optical signal of the TOF module light source; S2: Reflected light reaches multiple pixels on the TOF module sensor: The emitted light signal is reflected by the reflective surface to multiple pixels on the TOF module sensor to improve the accuracy of the TOF module distance measurement. The sensor receives the phase difference of the reflected light: Where Q1, Q2, Q3, and Q4 represent ADC (analog-to-digital converter) values ​​of different phases; S3: Pixel calibration: According to the special non-uniformity calibration algorithm, the pixels in different spatial domains are made uniform, and the corresponding degree of each pixel is basically the same. The original calculated value of the test distance is: In the formula, d is the value of the test distance; c is the speed of light; f is the modulation frequency; Q1, Q2, Q3, Q4—represent the ADC values ​​of different phases; S4: Determine the relationship constant between pixel response and distance: Use a certain central pixel to fit a curve for multiple different delays to obtain a constant k between pixel response and distance; S5: Perform distance calibration and compensation: After the non-uniform calibration, use a single pixel and a constant k to perform distance calibration and compensation.

2. A method for quickly calibrating a TOF module as claimed in claim 1, characterized in that: In step S3, the pixel calibration adopts a non-uniformity calibration algorithm to make the pixels in different spatial domains tend to be uniform and the corresponding degree of each pixel is basically consistent.

3. A method for quickly calibrating a TOF module as claimed in claim 2, characterized in that: In step S4, when determining the relationship constant between pixel correspondence and distance, a curve is fitted using a central pixel for a plurality of different delay amounts.

4. A method for quickly calibrating a TOF module as claimed in claim 3, characterized in that: In the step S5, in actual measurement, distance calibration and compensation are performed using a single pixel and a constant after non-uniformity calibration.

5. A method for quickly calibrating a TOF module as claimed in claim 4, characterized in that: In the step S1, the light signal of the TOF module light source is delayed, a delay circuit is used to delay the light source modulation clock signal of the TOF module, and the delayed light source modulation clock signal is used to drive the light source to emit a light signal.

Images