A device and method for optimizing the performance of a three-dimensional laser imager

Abstract

A device and method for optimizing the measurement performance of a three-dimensional laser imager are disclosed. An onboard clock provides a trigger signal for a ToF sensor and a reference timing signal for an adjustable delay phase-locked loop (PLL). A control unit determines the generation of signals with different delay lengths by controlling the operating states of different delay gates in a multi-level delay gate system. The input signal interface of the adjustable delay PLL is connected to the onboard clock, using the reference timing signal as the timing start point for the delay signal. The output signal interface is connected to a VCSEL driver circuit, controlling the VCSEL's operation through the delay length signal generated by the adjustable delay PLL. This method enables calibration of transmitted signals at different modulation frequencies throughout the entire cycle, improving distance measurement accuracy and reducing manpower, material resources, and calibration space. By setting three levels of delay gates, the calibration of all distance values ​​within the modulation cycle is fully covered. Different delay accuracies are determined by changing the operating states of the three delay gates according to the measurement accuracy requirements of the actual application scenario.

Description

Technical Field

[0001] This invention belongs to the technical field of three-dimensional laser imager measurement performance, and particularly relates to a three-dimensional laser imager measurement performance optimization device and a three-dimensional laser imager measurement performance optimization method. Background Technology

[0002] Three-dimensional laser imagers are widely used in target recognition, SLAM, 3D reconstruction, and industrial inspection due to their advantages such as low cost, simple structure, and high precision. They typically employ the iToF principle, acquiring sampled values ​​(DCS0 / 1 / 2 / 3) at four different phases (0 / 90 / 180 / 270°) to calculate the time of flight and thus obtain distance information. The calculation process is shown in Equation 1 below.

[0003]

[0004] In the formula, DCS0 / 1 / 2 / 3 are the sampled values ​​at 0 / 90 / 180 / 270° phase within a single cycle, respectively; f is the modulation frequency; c is the speed of light; and D is the measurement distance.

[0005] In practical applications, the object will move relative to the 3D laser imager during the measurement process. Due to the low frame rate of the 3D laser imager, the depth image will be blurred during the measurement process. In addition, when illuminated by a strong light source, high-brightness areas and low-brightness areas coexist in the field of view. Because the integration time is the same, the output image will show the coexistence of bright areas (overexposure) and dark areas (underexposure), which seriously affects the image quality.

[0006] Secondly, in order to improve measurement accuracy, the 3D laser imager is usually manually placed on the guide rail to calibrate the measurement value. A large flat plate or white wall is set in front of the 3D laser imager, and images are taken at different distances to establish the relationship between the distance measurement value and the actual distance value, thereby correcting the measurement distance error value and improving the measurement accuracy. This method has relatively strict requirements on manpower, material resources and environmental conditions.

[0007] Finally, the requirements for the measurement performance parameters of 3D laser imagers are not entirely the same under different measurement environments, mainly including performance parameters such as resolution, frame rate, sensitivity and measurement accuracy; it is urgent to optimize the measurement performance according to different measurement environments and improve the environmental adaptability of 3D laser imagers. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, the technical problem to be solved by the present invention is to provide a measurement performance optimization device for a three-dimensional laser imager, which can replace traditional guide rail calibration, calibrate the transmitted signal under different modulation frequencies throughout the entire cycle, improve distance measurement accuracy, and reduce manpower, material resources, and calibration space; it can fully cover the calibration of all distance values ​​within the modulation cycle, and can also change the working state of the three-level delay gate to determine different delay accuracies according to the measurement accuracy requirements in actual application scenarios.

[0009] The technical solution of the present invention is: a three-dimensional laser imager measurement performance optimization device, which includes: an onboard clock, a ToF sensor, an adjustable delay phase-locked loop, a VCSEL driving circuit, and a VCSEL;

[0010] The onboard clock is connected to the ToF sensor and the adjustable delay phase-locked loop, providing a data acquisition trigger signal for the ToF sensor and a reference timing signal for the adjustable delay phase-locked loop.

[0011] The adjustable delay phase-locked loop includes multiple multi-level delay gates, a control unit, an input signal interface, and an output signal interface;

[0012] The control unit determines the generation of signals with different delay lengths by controlling the working state of different delay gates in the multi-level delay gate;

[0013] The input signal interface of the adjustable delay phase-locked loop is connected to the onboard clock and uses the reference timing signal as the starting point for the delay signal; the output signal interface is connected to the VCSEL driver circuit, which controls the VCSEL to work through the delay length signal generated by the adjustable delay phase-locked loop.

[0014] This invention provides a trigger signal for ToF sensor acquisition via an onboard clock, and simultaneously provides a reference timing signal for an adjustable delay phase-locked loop (PLL). The adjustable delay PLL includes multiple multi-level delay gates, a control unit, an input signal interface, and an output signal interface. The control unit determines the generation of signals with different delay lengths by controlling the operating states of different delay gates within the multi-level delay gates. The input signal interface of the adjustable delay PLL is connected to the onboard clock and uses the reference timing signal as the timing start point for the delay signal. The output signal interface is connected to the VCSEL driver circuit, which controls the VCSEL to operate based on the delay length signal generated by the adjustable delay PLL. This invention can replace traditional guide rail calibration, calibrating the transmitted signal at different modulation frequencies throughout the entire cycle, improving distance measurement accuracy, and reducing manpower, material resources, and calibration space. Furthermore, by setting three levels of delay gates, the calibration of all distance values ​​within the modulation cycle can be fully covered. The operating states of the three levels of delay gates can also be changed to determine different delay accuracies according to the measurement accuracy requirements of the actual application scenario.

[0015] A method for optimizing the measurement performance of a three-dimensional laser imager is also provided, which includes the following steps:

[0016] (1) According to the measurement performance requirements, the echo signals under different integration times and different phases are collected, and the pixels in the ToF sensor are combined in different directions to determine the performance parameters of resolution, frame rate, sensitivity and signal-to-noise ratio. After the pixels are combined in different directions, they are measured at different modulation frequencies. The measurement error at different modulation frequencies is corrected by multi-level delay gates.

[0017] (2) Divide the sampling period under different modulation frequencies into 8 equal parts, sample at different phase points, and use the multi-step phase shift method to calculate the distance of the echo signal.

[0018] (3) Using the different length delay signals generated in the three-dimensional laser imager measurement performance optimization device as reference values, compare them with the measurement values ​​obtained by the three-dimensional laser imager at different modulation frequencies to correct the distance measurement error value. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the working principle of the three-dimensional laser imager measurement performance optimization device according to the present invention.

[0020] Figure 2 This is a schematic diagram illustrating the working principle of the multi-stage delay gate according to the present invention.

[0021] Figure 3 This is a framework diagram of the pixel combination method according to the present invention.

[0022] Figure 4 This is a schematic diagram of a pixel assembly unit according to the present invention.

[0023] Figure 5 This is a schematic diagram of the pixel combination planar field according to the present invention.

[0024] Figure 6 This is a diagram illustrating the working mode of a pixel according to the present invention.

[0025] Figure 7 This is a schematic diagram of the pixel downsampling state according to the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] To make the description of this disclosure more detailed and complete, illustrative descriptions of embodiments and specific examples of the present invention are provided below; however, these are not the only forms of implementing or utilizing the specific examples of the present invention. The embodiments cover features of multiple specific examples and methods and steps for constructing and operating these specific examples, and their order. However, other specific examples may also be used to achieve the same or equivalent functions and order of steps.

[0028] like Figure 1 As shown, this 3D laser imager measurement performance optimization device includes: an onboard clock, a ToF sensor, an adjustable delay phase-locked loop, a VCSEL drive circuit, and a VCSEL.

[0029] The onboard clock is connected to the ToF sensor and the adjustable delay phase-locked loop, providing a data acquisition trigger signal for the ToF sensor and a reference timing signal for the adjustable delay phase-locked loop.

[0030] The adjustable delay phase-locked loop includes multiple multi-level delay gates, a control unit, an input signal interface, and an output signal interface;

[0031] The control unit determines the generation of signals with different delay lengths by controlling the working state of different delay gates in the multi-level delay gate;

[0032] The input signal interface of the adjustable delay phase-locked loop is connected to the onboard clock and uses the reference timing signal as the starting point for the delay signal; the output signal interface is connected to the VCSEL driver circuit, which controls the VCSEL to work through the delay length signal generated by the adjustable delay phase-locked loop.

[0033] This invention provides a trigger signal for ToF sensor acquisition via an onboard clock, and simultaneously provides a reference timing signal for an adjustable delay phase-locked loop (PLL). The adjustable delay PLL includes multiple multi-level delay gates, a control unit, an input signal interface, and an output signal interface. The control unit determines the generation of signals with different delay lengths by controlling the operating states of different delay gates within the multi-level delay gates. The input signal interface of the adjustable delay PLL is connected to the onboard clock and uses the reference timing signal as the timing start point for the delay signal. The output signal interface is connected to the VCSEL driver circuit, which controls the VCSEL to operate based on the delay length signal generated by the adjustable delay PLL. This invention can replace traditional guide rail calibration, calibrating the transmitted signal at different modulation frequencies throughout the entire cycle, improving distance measurement accuracy, and reducing manpower, material resources, and calibration space. Furthermore, by setting three levels of delay gates, the calibration of all distance values ​​within the modulation cycle can be fully covered. The operating states of the three levels of delay gates can also be changed to determine different delay accuracies according to the measurement accuracy requirements of the actual application scenario.

[0034] Preferably, such as Figure 2 As shown, the multi-level delay gate is divided into three levels of delay according to the delay length, including a first-level delay gate, a second-level delay gate, and a third-level delay gate; wherein the length of the first-level delay gate is determined according to the frequency of the modulation signal and covers the entire modulation signal period, the second-level delay gate covers one delay unit in the first-level delay, and the third-level delay gate covers one delay unit in the second-level delay;

[0035] In a multi-stage delay gate, the three delay gates target successively increasing modulation frequencies {f1,...,f i ,…,f j The transmitted signal undergoes a determined delay length, with the first-stage delay gate having frequencies {f1,...,f}. i Divide the modulated signal within {f} into m equal parts, and divide the frequency {f} into m equal parts. i ,…,f j The modulated signal within} is divided into n equal parts, where m>n.

[0036] A method for optimizing the measurement performance of a three-dimensional laser imager is also provided, which includes the following steps:

[0037] (1) According to the measurement performance requirements, the echo signals under different integration times and different phases are collected, and the pixels in the ToF sensor are combined in different directions to determine the performance parameters of resolution, frame rate, sensitivity and signal-to-noise ratio. After the pixels are combined in different directions, they are measured at different modulation frequencies. The measurement error at different modulation frequencies is corrected by multi-level delay gates.

[0038] (2) Divide the sampling period under different modulation frequencies into 8 equal parts, sample at different phase points, and use the multi-step phase shift method to calculate the distance of the echo signal.

[0039] (3) Using the different length delay signals generated in the three-dimensional laser imager measurement performance optimization device as reference values, compare them with the measurement values ​​obtained by the three-dimensional laser imager at different modulation frequencies to correct the distance measurement error value.

[0040] like Figure 3 As shown, step (1) mainly includes different pixel combination methods, different pixel working modes, and pixel downsampling states. Among them, the different pixel combination methods mainly include along the horizontal direction, vertical direction, and horizontal and vertical directions; the pixel working modes are mainly divided into acquiring different phases under the same integration time and acquiring a single phase under different integration times; the pixel downsampling states mainly include sampling along the y-axis every 2, 4, 8, and n rows.

[0041] Preferably, the uncombined state is as follows: Figure 4As shown in Figure a, in step (1), the pixels are combined according to the horizontal direction, the vertical direction, and different directions of the horizontal and vertical directions, respectively, as shown in Figure a. Figure 4 As shown in b to d, the schematic diagram after applying the pixel combination unit to the pixel planar field is shown below. Figure 5 As shown. Figure 5 'a' indicates that the pixels were not combined; Figure 5 b indicates that the pixel planar field is combined in the horizontal direction; Figure 5 c represents the vertical combination of the pixel plane field; Figure 5 d represents the combination of the pixel plane field in the horizontal and vertical directions.

[0042] Preferably, the pixel combination in step (1) includes the following method:

[0043] (a) Pixel-free combination ( Figure 5 (as shown in a); all pixels are simultaneously acquired to measure the same phase, and the resolution, sensitivity, signal-to-noise ratio, and data readout time parameters in this state are recorded as the baseline;

[0044] (b) Horizontal combination Figure 5 (as shown in b); by combining pixels in pairs along the horizontal direction, compared to (a), the resolution in this state is reduced to the original value. Pixel sensitivity increased by 2 times, signal-to-noise ratio improved The data read time has been reduced by a factor of two to the original time.

[0045] (c) Vertical combination Figure 5 (As shown in c); by combining pixels in pairs along the vertical direction, compared to (a), the resolution in this state is reduced to the original value. Pixel sensitivity increased by 2 times, signal-to-noise ratio improved The data read time has been reduced by a factor of two to the original time.

[0046] (d) Combination of horizontal and vertical directions Figure 5 (As shown in d); by combining pixels in pairs along the horizontal and vertical directions, compared to (a), the resolution in this state is reduced to the original.

[0047] Pixel sensitivity is increased by 4 times, signal-to-noise ratio is increased by 2 times, and data readout time is reduced to the original value.

[0048] Preferably, after different combination methods are applied to the pixels, measurements of different phases are acquired at different integration times, including the following operating modes:

[0049] Under the same integration time, all pixels acquire measurements of a single phase (e.g.) Figure 6(as shown in a), and then four measurements under different phases are collected sequentially to calculate depth information;

[0050] Measurements of different phases were acquired under the same integration time (e.g.) Figure 6 (As shown in b). Odd-numbered rows (black boxes) and even-numbered rows (white boxes) within a pixel are sampled in DCS0 and DCS1 with a phase difference of 90° within the same integration time. Subsequently, DCS2 and DCS3 are simultaneously sampled to calculate depth information. This mode reduces the resolution of the depth image but increases the frame rate, effectively eliminating motion blur.

[0051] Measurements of a single phase were acquired at different integration times (e.g.) Figure 6 (As shown in c). Odd-numbered rows (black box) and even-numbered rows (dashed box) of pixels are controlled by different integration times. The measurements acquired in a single phase have exposure times with different integration times, thus effectively eliminating wide dynamic range imaging phenomena.

[0052] Preferably, such as Figure 7 As shown, after processing through the aforementioned combination methods and working modes, the frame rate can be increased by reducing the number of pixel sampling points. This mainly includes the following states: Figure 7 'a' represents the full sampling state; Figure 7 b represents the sampling state with an interval of 2 rows; Figure 7 c represents the sampling state with an interval of 4 rows; Figure 7 d represents the sampling state with an interval of 8 rows; the sampling state with an interval of n rows is not listed here. Only the state when all pixels are not combined is listed here. The three pixel combination states mentioned above are all applicable and will not be specifically described in the attached figure.

[0053] (1) All pixels in the pixel plane field are acquired in the same integration time using the full-resolution mode, such as... Figure 7 As shown in a, no resolution downgrading was performed, and the parameters (resolution, frame rate) in this mode were recorded as the baseline.

[0054] (2) Select each column on the x-axis, and sample every 2 rows along the y-axis, such as... Figure 7 As shown in b, this mode reduces the resolution to the original value compared to (1). The frame rate has been increased by 2 times;

[0055] (3) Select each column on the x-axis, and sample every 4 rows along the y-axis, such as... Figure 7 As shown in c, this mode reduces the resolution to the original value compared to (1). The frame rate has been increased by 4 times;

[0056] (4) Select each column on the x-axis, and sample every 8 rows along the y-axis, such as... Figure 7As shown in d, this mode reduces the resolution to the original compared to (1). The frame rate has been increased by 8 times;

[0057] (5) Select each column on the x-axis and sample every n rows in the y-axis direction. The value of n is selected according to the actual frame rate requirements. Compared with state (1), the resolution is reduced to the original value.

[0058] The frame rate has been increased by n times.

[0059] Preferably, after the pixels are combined in different directions, they are measured at different modulation frequencies, and the measurement error at different modulation frequencies is corrected by step (4).

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for optimizing the measurement performance of a three-dimensional laser imager, comprising a device for optimizing the measurement performance of a three-dimensional laser imager, the device comprising: Onboard clock, ToF sensor, adjustable delay phase-locked loop, VCSEL driver circuit, VCSEL; The onboard clock is connected to the ToF sensor and the adjustable delay phase-locked loop, providing a data acquisition trigger signal for the ToF sensor and a reference timing signal for the adjustable delay phase-locked loop. The adjustable delay phase-locked loop includes multiple multi-level delay gates, a control unit, an input signal interface, and an output signal interface; The control unit determines the generation of signals with different delay lengths by controlling the working state of different delay gates in the multi-level delay gate; The input signal interface of the adjustable delay phase-locked loop is connected to the onboard clock and uses the reference timing signal as the timing start point of the delay signal; the output signal interface is connected to the VCSEL driver circuit, which controls the VCSEL to work through the delay length signal generated by the adjustable delay phase-locked loop. The method is characterized by the following steps: (1) According to the measurement performance requirements, the echo signals under different integration times and different phases are collected, and the pixels in the ToF sensor are combined in different directions to determine the performance parameters of resolution, frame rate, sensitivity and signal-to-noise ratio. After the pixels are combined in different directions, they are measured at different modulation frequencies. The measurement error at different modulation frequencies is corrected by multi-level delay gates. (2) Divide the sampling period of different modulation frequencies into 8 equal parts, sample at different phase points, and use the multi-step phase shift method to calculate the distance of the echo signal; (3) Using the different length delay signals generated in the three-dimensional laser imager measurement performance optimization device as reference values, compare them with the measurement values ​​obtained by the three-dimensional laser imager at different modulation frequencies to correct the distance measurement error value; In step (1), the pixels are combined according to the horizontal direction, the vertical direction, and different directions of the horizontal and vertical directions.

2. The method for optimizing the measurement performance of a three-dimensional laser imager according to claim 1, characterized in that: The multi-level delay gate is divided into three levels of delay according to the delay length, including a first-level delay gate, a second-level delay gate, and a third-level delay gate; the length of the first-level delay gate is determined according to the frequency of the modulation signal and covers the entire modulation signal period; the second-level delay gate covers one delay unit in the first-level delay; and the third-level delay gate covers one delay unit in the second-level delay. In a multi-stage delay gate, the three stages of delay gates are for successively increasing modulation frequencies. f 1,..., f i ,…, f j The transmitted signal undergoes a determined delay length, and the frequency of the first-stage delay gate is { f 1,..., f i Divide the modulated signal within} into m equal parts, and divide the frequency of { f i ,…, f j The modulated signal within} is divided into n equal parts, where m>n.

3. The method for optimizing the measurement performance of a three-dimensional laser imager according to claim 2, characterized in that: The pixel combination in step (1) includes the following methods: (a) No pixel combination; all pixels simultaneously acquire the same phase measurement value, and the resolution, sensitivity, signal-to-noise ratio and data readout time parameters in this state are recorded as the reference; (b) Horizontal combination; combining pixels in pairs along the horizontal direction, compared to (a), the resolution in this state is reduced to the original. Pixel sensitivity is increased by 2 times, and signal-to-noise ratio is improved. The data read time has been reduced by a factor of two to the original time. ; (c) Vertical combination; combining pixels in pairs along the vertical direction, compared to (a), the resolution in this state is reduced to the original. Pixel sensitivity is increased by 2 times, and signal-to-noise ratio is improved. The data read time has been reduced by a factor of two to the original time. ; (d) Horizontal and vertical combination; combining pixels in pairs along the horizontal and vertical directions, compared to (a), the resolution in this state is reduced to the original. Pixel sensitivity is increased by 4 times, signal-to-noise ratio is increased by 2 times, and data readout time is reduced to the original time. .

4. The method for optimizing the measurement performance of a three-dimensional laser imager according to claim 3, characterized in that: After different combination methods, the pixels acquire measurements of different phases at different integration times, including the following operating modes: All pixels acquire single-phase measurements within the same integration time. Measurements of different phases were collected under the same integration time. DCS0 and DCS1 with a phase difference of 90° were collected in the odd-numbered rows and even-numbered rows of the pixel, respectively. Measurements of a single phase are acquired at different integration times. Odd-numbered and even-numbered rows of pixels are controlled by different integration times, and all pixels acquire measurements of the same phase.

5. The method for optimizing the measurement performance of a three-dimensional laser imager according to claim 4, characterized in that: Different operating modes increase the frame rate by reducing the number of pixel sampling points, including the following states: (I) Full resolution mode is used without resolution downgrading. The resolution and frame rate parameters in this state are recorded as the baseline. (II) Selection x Each column on the axis, and in y Sampling is performed every two rows along the axis, reducing the resolution to the original value compared to state (I). The frame rate is increased by 2 times; (III) Selection x Each column on the axis, and in y Sampling is performed every 4 rows along the axis, reducing the resolution to the original value compared to state (I). The frame rate is increased by 4 times; (IV) Selection x Each column on the axis, and in y Sampling is performed every 8 rows along the axis, reducing the resolution to the original value compared to state (I). The frame rate is increased by 8 times; (V) Select x Each column on the axis, and in y Every axial direction n Sampling is performed in rows. n The value is selected based on the actual frame rate requirements, and the resolution is reduced to the original value compared to state (I). The frame rate has been improved. n times.

6. The method for optimizing the measurement performance of a three-dimensional laser imager according to claim 5, characterized in that: After the pixels are combined in different directions, they are measured at different modulation frequencies. The measurement error at different modulation frequencies is corrected through step (4).

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