A detection method to eliminate inter-pixel crosstalk

Abstract

This application provides a detection method for eliminating inter-pixel crosstalk, characterized by comprising: determining the range of surrounding pixels that cause crosstalk to a specific pixel; determining the crosstalk rate, absorption rate, and diffusion time of the surrounding pixels to the specific pixel; obtaining the number of crosstalk electrons of the surrounding pixels to the specific pixel and the influence of the surrounding pixel crosstalk on the distance based on the crosstalk rate, absorption rate, and diffusion time; and obtaining the overall influence of the surrounding pixel crosstalk on the ranging based on the number of crosstalk electrons of the surrounding pixels and the influence of the surrounding pixel crosstalk on the distance. Through the solution of this invention, ranging accuracy can be conveniently and effectively improved, meeting ranging requirements.

Description

Technical Field

[0001] This application relates to the field of detection technology, and in particular to a detection method for eliminating pixel crosstalk. Background Technology

[0002] Time-of-flight (TOF) technology has been developed as a method for measuring the distance to objects in a scene. This TOF technology can be applied to various fields, such as the automotive industry, human-machine interfaces, gaming, robotics, and security. Generally, TOF technology works by illuminating a scene with modulated light emitted from a light source and observing the reflected light from objects in the scene. In existing detection systems, to ensure higher detection efficiency and a wider field of view, an array-type receiver module is commonly used. This module can contain tens of thousands of pixels, each of which can be a diode of type CCD or CMOS, etc. However, this is not limited to using only these two types of diodes to form the array-type receiver module.

[0003] The detection array consists of tens of thousands of pixel units. During the ranging process, electrical crosstalk between different adjacent pixels can have a significant impact on the ranging. The common approach to reduce the impact of crosstalk is to change the pixel structure, such as setting up deep p-type wells, thinning epitaxial layers, and guard rings. However, this method of changing the pixel structure is relatively complex and costly. Therefore, there is an urgent need to propose a convenient and accurate method to remove the impact of crosstalk on the ranging results. Summary of the Invention

[0004] The purpose of this application is to provide a detection method for eliminating inter-pixel crosstalk, which is convenient and effectively improves ranging accuracy, in order to address the shortcomings of the prior art.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0006] 1. This application provides a detection method for eliminating inter-pixel crosstalk, characterized in that it includes:

[0007] Determine the range of surrounding pixels that cause crosstalk to a specific pixel;

[0008] Determine the crosstalk rate, absorption rate, and diffusion time of the surrounding pixels to the specific pixel;

[0009] The crosstalk rate, absorption rate, and diffusion time are used to obtain the number of crosstalk electrons of the surrounding pixels to the specific pixel and the influence of the crosstalk of the surrounding pixels on the distance.

[0010] Based on the number of crosstalk electrons in the surrounding pixels and the influence of the crosstalk of the surrounding pixels on the distance, the overall influence of the crosstalk of the surrounding pixels on the ranging is obtained.

[0011] Optionally, the range of the surrounding pixels is obtained through experimental or theoretical methods.

[0012] Optionally, the crosstalk rate, absorption rate, and diffusion time of the surrounding pixels to a specific pixel are obtained experimentally.

[0013] Optionally, the overall impact of peripheral pixel crosstalk on ranging is obtained by weighted averaging of the number of crosstalk electrons in the peripheral pixels and the impact of peripheral pixel crosstalk on distance.

[0014] Optionally, the influence of the crosstalk of the surrounding pixels on the distance can be obtained by the position of the surrounding pixels and the diffusion time.

[0015] Optionally, the range of the surrounding pixels is a range in a one-dimensional direction or a range in a two-dimensional direction.

[0016] Optionally, the crosstalk rate is 49.5%.

[0017] Optionally, the absorption rate is 64%.

[0018] Optionally, the diffusion time is 0.76 ns.

[0019] The beneficial effects of this application are:

[0020] This application provides a detection method for eliminating inter-pixel crosstalk, characterized in that it includes:

[0021] Determine the range of surrounding pixels that cause crosstalk to a specific pixel;

[0022] Determine the crosstalk rate, absorption rate, and diffusion time of the surrounding pixels to the specific pixel;

[0023] The crosstalk rate, absorption rate, and diffusion time are used to obtain the number of crosstalk electrons of the surrounding pixels to the specific pixel and the influence of the crosstalk of the surrounding pixels on the distance.

[0024] Based on the number of crosstalk electrons in the surrounding pixels and the influence of the crosstalk of the surrounding pixels on the distance, the overall influence of the crosstalk of the surrounding pixels on the ranging is obtained. Through the solution of the present invention, the ranging accuracy can be improved conveniently and effectively, and the ranging requirements can be met. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of an array-type receiving module provided in an embodiment of this application;

[0027] Figures 2a-2b A schematic diagram illustrating electrical crosstalk between adjacent pixels provided in an embodiment of this application;

[0028] Figure 3 A schematic diagram of one-dimensional directional electronic crosstalk provided for an embodiment of this application;

[0029] Figure 4 This application provides a detection method for improving ranging accuracy.

[0030] Figure 5 This diagram illustrates the comparison between theoretical simulation and experimental results provided in the embodiments of this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] The current detection system basically includes a light source module, a processing module, and a light receiving module. The light source module includes, but is not limited to, semiconductor lasers, solid-state lasers, and may also include other types of lasers. When a semiconductor laser is used as the light source, a vertical-cavity surface-emitting laser (VCSEL) or an edge-emitting semiconductor laser (EEL) can be used. This is only an example and is not a specific limitation. The light source module emits sine waves, square waves, triangular waves, or pulse waves, etc. In ranging applications, lasers with a certain wavelength are often used, such as infrared lasers (ideally near-infrared lasers) at 950nm. The emitted light is projected into the field of view. The object being detected in the field of view can reflect the projected laser and form a return light. The return light enters the detection system and is captured by the light receiving module. The light receiving module may include a photoelectric conversion unit, such as an array sensor composed of CMOS, CCD, etc., and may also include multiple lenses to form more than one image plane. That is, the receiving module contains more than one image plane, and the photoelectric conversion unit of the receiving module is located at one of the image planes.

[0035] The receiving module can be adopted as follows: Figure 1 The array-type receiving module shown contains pixel units composed of diodes. In actual implementation, the active region of the array-type receiving module can be composed of M*N pixel units, and the number of pixel units can be in the tens of thousands or even hundreds of thousands, etc., which is not limited here. The array-type receiving module can include a lens part 101 and a detection unit substrate part. The lens part contains multiple lens units, which can be composed of microlens units with a predetermined curvature. Of course, in order to ensure the maximum utilization of the returned light, the lens part can also contain more than one layer of structure. The specific implementation scheme is not limited here. In a better case, the substrate part can be set at the focal plane position corresponding to the lens part, so as to ensure that the detection pixel unit can obtain the returned light with maximum accuracy. In this case, the lens of the lens section can construct an optical channel, so that the signal received by the photosensitive part of the detection unit is near the corresponding focal position. The substrate of the detection unit contains an array of photosensitive pixels arranged in an array. The photosensitive pixels can be formed by doping on the semiconductor substrate to form photosensitive units of CCD or CMOS, etc. At the same time, the semiconductor substrate can also contain all the analog signal processing circuits used in the readout of the pixel unit, pixel level control circuits, analog-to-digital conversion circuits (ADC), etc. When arranging the positional relationship between the circuit and the photosensitive unit, a front-illumination process can be adopted, in which the circuit layer is arranged upstream of the photosensitive unit along the direction of return light propagation, or a back-illumination process can be adopted, in which the circuit layer is arranged downstream of the photosensitive unit along the direction of return light propagation. The specific implementation method is not limited here.

[0036] Figures 2a-2b This is a schematic diagram illustrating electrical crosstalk between adjacent pixels provided in an embodiment of this application; as shown... Figure 2a The diagram assumes that pixel A has no electrons, and pixel B interfers with electrons to pixel A.

[0037] Crosstalking electrons reach pixel A after a diffusion time Δt, causing pixel A to detect the electrons after time t.

[0038] The distance corresponding to pixel A is d1=Δt / 2*c. This distance represents the influence of crosstalk of pixel B on the ranging of pixel A. Multiplying it by its influence weight gives its actual influence on the ranging distance of pixel A, as shown in formula (1).

[0039]

[0040] like Figure 2b As shown, assume pixel B is in the back and pixel A is in the front.

[0041] After a distance-induced delay time t, the crosstalk electrons reach pixel A after a diffusion time Δt, so that pixel A can detect the electrons after a time of Δt+t.

[0042] The distance corresponding to pixel A is d1'=Δt / 2*c+t / 2*c, d1'=d1+Δd, which gives the magnitude of the ranging error of pixel A caused by pixel crosstalk at different depths, as shown in formula (2).

[0043]

[0044] From formulas (1) and (2), we can conclude that the effect of pixel crosstalk is equivalent to the weighted average of the effect of surrounding pixels on the crosstalk of the pixel under study, as shown in formula (3).

[0045]

[0046] In equation (3), d i This represents the impact of crosstalk from a neighboring pixel on distance. Q represents the weight of the crosstalk effect of a neighboring pixel. i The number of electrons representing crosstalk to a certain neighboring pixel.

[0047] Figure 3 This diagram illustrates one-dimensional directional electron crosstalk as provided in an embodiment of this application. The delay effect caused by pixel electron crosstalk corresponds to the electron diffusion time. The number of crosstalk electrons in a pixel is related to the pixel's crosstalk rate and the probability of the crosstalk electron being absorbed by each pixel. Considering one-dimensional directional crosstalk... Figure 3As shown, the number of crosstalk electrons that reach the Nth adjacent pixel from the electron generated by the pixel is:

[0048] Q i =Q * crosstalk * (1 - absorption) N-1 *absorption (4)

[0049] Since the crosstalk range is mainly related to the pixel's absorptivity, a rough value of the absorptivity is determined based on the crosstalk range of the black-and-white board crosstalk experiment. The amplitude ratio and size of the crosstalk region are related to the crosstalk rate and diffusion time. The crosstalk rate and diffusion time are adjusted in combination with the experimental results to make the simulation results the same as the crosstalk results. Furthermore, the results remain the same even when the experimental conditions are changed. Finally, the pixel's crosstalk rate is determined to be 49.5%, the absorptivity to be 64%, and the diffusion time to be 0.76 ns. The crosstalk rate, absorptivity, and diffusion time obtained through the experiment can be used to obtain Q through formula (4). i d can be obtained by considering the diffusion time and the pixel position. i According to formula (3), the influence of crosstalk between adjacent pixels on a specific pixel on the ranging can be obtained. Compensating for the influence of crosstalk on the ranging during the ranging process can improve the ranging accuracy.

[0050] exist Figure 3 Once the value of N in the surrounding pixels reaches a certain range, the crosstalk to a specific pixel can be ignored. The value of N can be obtained experimentally or through theoretical calculation. This invention does not impose any limitations on this.

[0051] Figure 4 This application provides a detection method to improve ranging accuracy. Figure 4 The detection method shown includes the following steps:

[0052] S401: Determine the range of surrounding pixels that cause crosstalk to a specific pixel; that is, determine... Figure 3 The range of N in the illustrated embodiment can be determined by experimental data or by theoretical calculation. Figure 3 The illustrated embodiment only shows the peripheral pixels in a one-dimensional direction. In actual detection, peripheral pixels can also be in other directions, such as two-dimensional peripheral pixels. Two-dimensional peripheral pixels can be as follows: Figure 2b The situation shown could also be other situations. Figures 2a-2b and Figure 3 This is merely for illustrative purposes and does not impose any specific limitations.

[0053] S402: Determine the crosstalk rate, absorptivity, and diffusion time of a specific pixel from its surrounding pixels. The crosstalk range of a specific pixel from its surrounding pixels is mainly related to the pixel's absorptivity. A rough value for the absorptivity is determined based on the crosstalk range obtained from the black-and-white board crosstalk experiment. The amplitude ratio and size of the crosstalk region are related to the crosstalk rate and diffusion time. The crosstalk rate and diffusion time are adjusted based on the experimental results to ensure that the simulation results match the actual crosstalk results. Further adjustments are made to the experimental conditions, ensuring the results remain consistent. Finally, the pixel's crosstalk rate, absorptivity, and diffusion time are determined. Different detector arrays will yield different crosstalk rates, absorptivity, and diffusion times through experimental methods.

[0054] S403: Based on the crosstalk rate, absorption rate, and diffusion time, the number of crosstalk electrons from surrounding pixels to a specific pixel and the influence of crosstalk from surrounding pixels on the distance can be obtained. Once the crosstalk rate and absorption rate are determined, the number of crosstalk electrons from surrounding pixels to a specific pixel can be obtained using formula (4); once the diffusion time is determined, the influence of crosstalk from surrounding pixels on the distance can be obtained based on the diffusion time and the position of the surrounding pixels.

[0055] S404: Based on the number of crosstalk electrons in the surrounding pixels and the influence of the crosstalk of the surrounding pixels on the distance, the overall influence of the crosstalk of the surrounding pixels on the ranging is obtained by weighted averaging. The overall influence of the crosstalk of the surrounding pixels on the ranging can be obtained by formula (3).

[0056] S405: Corrects the ranging result based on the overall impact of crosstalk from surrounding pixels on the ranging, resulting in a high-precision ranging result. This improves ranging accuracy.

[0057] Figure 5 This is a schematic diagram comparing theoretical simulation and experimental results provided for embodiments of this application. Figure 5 As shown, using Figure 4 The simulated crosstalk results show good agreement with the experimental results, thus verifying the detection method. Figure 4 The effectiveness of the detection method shown.

[0058] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application. It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need further definition and explanation in subsequent figures. The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A detection method for eliminating inter-pixel crosstalk, characterized in that, include: Determine the range of surrounding pixels that cause crosstalk to a specific pixel; Determine the crosstalk rate, absorption rate, and diffusion time of the surrounding pixels to the specific pixel; Based on the crosstalk rate, absorption rate, and diffusion time, the number of crosstalk electrons from surrounding pixels to the specific pixel and the influence of crosstalk from surrounding pixels on distance are obtained. The number of crosstalk electrons from a pixel reaching the Nth adjacent pixel is: Q i =Q * crosstalk * (1 - absorption) N-1 *absorption, Q i Let Q be the number of crosstalk electrons in a pixel, Q be the number of electrons generated by the pixel, crosstalk be the crosstalk rate of the pixel, and absorption be the probability that the crosstalk electrons are absorbed when passing through a pixel. Based on the number of crosstalk electrons of the surrounding pixels and the influence of the crosstalk of the surrounding pixels on the distance, the overall influence of the crosstalk of the surrounding pixels on the ranging is obtained, and the influence of the crosstalk of the surrounding pixels on the distance is obtained by the position of the surrounding pixels and the diffusion time. The overall impact of peripheral pixel crosstalk on ranging is obtained by weighted averaging of the number of crosstalk electrons in the peripheral pixels and the impact of peripheral pixel crosstalk on distance.

2. The detection method for eliminating inter-pixel crosstalk as described in claim 1, characterized in that, The range of the surrounding pixels is obtained through experimental or theoretical methods.

3. The detection method for eliminating inter-pixel crosstalk as described in claim 1, characterized in that, The crosstalk rate, absorption rate, and diffusion time of the surrounding pixels to the specific pixel were obtained experimentally.

4. The detection method for eliminating inter-pixel crosstalk as described in claim 1, characterized in that, The range of the surrounding pixels is either a range in a one-dimensional direction or a range in a two-dimensional direction.

5. The detection method for eliminating inter-pixel crosstalk as described in claim 1, characterized in that, The crosstalk rate is 49.5%.

6. The detection method for eliminating inter-pixel crosstalk as described in claim 1, characterized in that, The absorption rate is 64%.

7. The detection method for eliminating inter-pixel crosstalk as described in claim 1, characterized in that, The diffusion time is 0.76 ns.

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