Laser ranging method and apparatus

Abstract

The application discloses a laser ranging method and device. The laser ranging method comprises the following steps: a first storage space is arranged, and an adjustment difference value is arranged; the first storage space is used for storing a data; laser exposure is started; a data output by a TDC in real time is compared with a first data in the first storage space; according to a comparison result, the first data is added or subtracted by the adjustment difference value to be saved in the first storage space as updated data, wherein the first data is preset with an initial value; until the exposure is finished, the comparison step is stopped; and a distance measurement value of an object is determined according to the value of the first data. The laser ranging method can reduce the use of a memory, so that the area of a ranging chip is significantly reduced.

Description

Technical Field

[0001] This application relates to the field of optical ranging technology, and more particularly to a laser ranging method and apparatus. Background Technology

[0002] Currently, lidar measurement systems based on dTOF (Direct Time-of-Flight) measurements typically include a transmitter and a receiver. The receiver usually employs a SPAD (Single Photon Avalanche Diode) array to receive the returned light signal and uses a TDC (Time-to-Digital Converter) to convert the time information into a quantized multi-bit digital signal. This signal is then processed through long exposure times and TDC-triggered cumulative values ​​to create a distance-based statistical histogram, from which the object's distance is determined. However, this laser ranging method generally requires a complete statistical histogram for each pixel. As the resolution of area-array lidar increases, the size of the subsequent processing TDC array and memory (such as SRAM (Static Random-Access Memory)) becomes larger, leading to excessively large chip areas for the ranging chip. Summary of the Invention

[0003] In view of this, embodiments of this application provide a laser ranging method and apparatus to solve the problem of excessively large chip area in traditional laser ranging methods that use statistical histograms.

[0004] In a first aspect, embodiments of this application provide a laser ranging method, the method comprising:

[0005] A first storage space is provided, and an adjustment difference is provided. The first storage space is used to store a piece of data.

[0006] When laser exposure begins, the data output in real time by the TDC is compared with the first data in the first storage space. Based on the comparison result, the first data is added to or subtracted from the adjustment difference and stored as updated data in the first storage space. The first data has a preset initial value. The comparison step is stopped when the exposure ends.

[0007] Based on the value of the first data, determine the object distance measurement value.

[0008] In addition to the aspects and any possible implementations described above, a further implementation is provided, wherein the method further includes:

[0009] A second storage space is provided, and the storage capacity of the second storage space is greater than that of the first storage space;

[0010] The first data is added to or subtracted from the adjustment difference and stored as updated data in the first storage space, and simultaneously stored in the second storage space. When the exposure ends, the storage capacity of the second storage space stores N historical values ​​of the first data, where N is a positive integer and the value of N is less than the maximum range of the TDC.

[0011] Calculate the average of N historical values ​​of the first data;

[0012] The distance measurement of the object is determined based on the average of the N historical values ​​of the first data.

[0013] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the first storage space is a part of the second storage space, the second storage space being a shift register capable of storing N data, and the first storage space occupying the first or last position of the second storage space.

[0014] In addition to the aspects and any possible implementations described above, a further implementation is provided, wherein comparing the data output in real time by the TDC with the first data in the first storage space, and based on the comparison result, adding or subtracting the adjustment difference from the first data as updated data and storing it in the first storage space, includes:

[0015] Compare the data output in real time by the TDC with the first data in the first storage space;

[0016] If the first data is less than the data output by the TDC in real time, the first data is added to the adjustment difference to obtain the updated data, which is then stored in the first storage space.

[0017] If the first data is greater than the data output by the TDC in real time, then the first data minus the adjustment difference is used to obtain the updated data, which is then stored in the first storage space.

[0018] If the first data is equal to the data output in real time by the TDC, then the first data is still stored in the first storage space.

[0019] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the initial value preset for the first data is the middle value of the range of the TDC.

[0020] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the adjustment difference includes a first adjustment difference and a second adjustment difference, the value of the first adjustment difference being greater than the value of the second adjustment difference, and the adjustment difference being changed according to the number of times the TDC is received, wherein when the number of comparisons reaches a preset threshold, the first adjustment difference is changed to the second adjustment difference.

[0021] In addition to the aspects and any possible implementations described above, a further implementation is provided that improves the accuracy of the object distance measurement by increasing the number of N or decreasing the adjustment difference.

[0022] In addition to the aspects described above and any possible implementation, an implementation is further provided in which the number of N ranges from 2 to 30, and the adjustment difference ranges from 0.5 to 10.

[0023] Secondly, embodiments of this application provide a laser ranging device, the device comprising:

[0024] A laser emitter, used to emit laser light;

[0025] SPAD array, used to receive optical signals;

[0026] TDC arrays are used to convert the time value of optical signal flight into digital signals.

[0027] A comparator is used to compare the data output in real time from one of the TDCs with the first data in the first storage space;

[0028] An up / down counter is used to add or subtract an adjustment difference to the first data as updated data and store it in the first storage space based on the comparison result, wherein the adjustment difference is preset.

[0029] The first storage space is used to store the first data, which has an initial value preset.

[0030] The processing circuit is used to determine the object distance measurement value based on the first data.

[0031] Furthermore, the device also includes a second storage space and a computing unit, wherein the storage capacity of the second storage space is greater than that of the first storage space;

[0032] The up / down counter is also used to add or subtract the adjustment difference from the first data as updated data and store it in the first storage space, and at the same time store it in the second storage space. When the exposure ends, the storage capacity of the second storage space stores N historical values ​​of the first data, where N is a positive integer and the value of N is less than the maximum range of the TDC.

[0033] The calculation unit is used to calculate the average value of N historical values ​​of the first data;

[0034] The processing circuit is further configured to determine the object distance measurement value based on the average of the historical values ​​of the N first data.

[0035] In this embodiment, a first storage space and an adjustment difference are provided. The first storage space is used to store a data point, and the adjustment difference can be used to convergently adjust and update the data in the first storage space so that the first data in the first storage space is closer to the actual object distance measurement value. Specifically, at the start of laser exposure, the data output in real time by the TDC is compared with the first data in the first storage space. Based on the comparison result, the first data plus or minus the adjustment difference is stored in the first storage space as updated data. The first data has a preset initial value. The comparison step is stopped when the exposure ends. By comparing the data output in real time by the TDC with the first data in the first storage space each time, the characteristics of the TDC output data conforming to the Poisson distribution can be utilized to continuously update and adjust the first data through each numerical comparison, so that the first data at the initial value converges quickly to near the actual object distance measurement value through numerical comparison. Finally, the object distance measurement value is determined based on the value of the first data. When the data output in real time by the TDC is compared with the first data in the first storage space a sufficient number of times, the error between the final first data and the actual object distance measurement value is small, and it is basically equivalent to the actual object distance measurement value. When using this laser ranging method, there is no need to store statistical histogram data inside the ranging chip, which can reduce or eliminate the use of SRAM to store data, and the area of ​​the ranging chip is significantly reduced. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure for optical ranging in existing technologies;

[0038] Figure 2 This is a schematic diagram of the process of using optical ranging to achieve histogram statistics in existing technologies;

[0039] Figure 3 This is a flowchart of a laser ranging method according to an embodiment of this application;

[0040] Figure 4This is a schematic diagram of the structure for implementing optical ranging in the embodiments of this application;

[0041] Figure 5 This is a schematic diagram of the process for implementing optical ranging in the embodiments of this application. Detailed Implementation

[0042] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0043] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0044] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0045] It should be understood that the term "and / or" used in this document is merely a description of the same field in the related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0046] It should be understood that although terms such as first, second, third, etc., may be used to describe preset ranges in the embodiments of this application, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from one another. For example, without departing from the scope of the embodiments of this application, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0047] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0048] Figure 1 This is a schematic diagram of a structure used in existing technologies for optical ranging. For example... Figure 1As shown, the lidar device 100 includes a laser emitting device 110, a control module 120, a SPAD module 140, a TDC module 150, and a memory 160. In optical ranging, the laser emitting device 110 emits a laser beam, which, through a lens, illuminates the target object 130, causing continuous exposure. During the exposure of the target object 130, photons are reflected back to the lidar device 100 through the lens. The lidar device 100 receives the returned light signal through the SPAD module 140 and converts the time information into a quantized multi-bit digital signal through the TDC module 150. Based on the long exposure time and the accumulated TDC trigger value, a distance-based dynamic histogram is plotted to obtain the distance information of the target object 130. The control module 120 controls the SPAD module 140, the TDC module 150, and the memory 160 to store the statistical histogram data.

[0049] Understandably, the SPAD module 140 includes multiple SPAD units, each capable of photon sensing and detection. The size of the SPAD array in the SPAD module 140 (the number of SPAD units it contains) characterizes the resolution of the ranging chip, such as 320*240 or 640*480. Higher resolution requires a larger scale and storage capacity from the subsequent TDC module 150 and memory 160 for histogram statistics. Generally, one SPAD unit corresponds to one complete statistical histogram. In the histogram, the horizontal axis represents time (or distance, where D = C * TOF / 2, where D represents distance, TOF is the conversion of time information into numerical time representation, and C represents the speed of light). The smallest division on the horizontal axis represents a time bin, corresponding to the minimum precision of the TDC; the vertical axis represents the accumulated count value of each time bin over a period of time. Therefore, for the storage requirements of the ranging chip, to achieve long-distance laser ranging, the memory depth needs to be large enough (to store a sufficient number of timebins); to achieve a high signal-to-noise ratio, the memory bit width needs to be wide enough (to store a larger accumulated count value). Assuming a dTOF receiver has 80x60 = 4800 pixels (SPAD unit), a TDC data bit width of 10 bits, a minimum precision of 0.1ns (corresponding to a distance of 1.5cm), and each time bin is represented by an 8-bit count value (maximum count value of 255), for a maximum detection distance of 6m (corresponding to 400 time bins, 400 * 1.5cm = 6m), the minimum memory size required for one frame of image is: 400 * 8 * 4800 = 15.36 Mbit = 1.92 Mbyte. If the resolution changes to 320x240 = 76800, while the maximum detection distance remains 6m, then the memory size required for one frame of image becomes: 400 * 8 * 76800 = 245.76 Mbit = 30.72 Mbyte. It is evident that as the resolution of area array lidar increases, the size of the subsequent processing TDC array and memory increases, and the chip area of ​​the ranging chip also increases accordingly.

[0050] Figure 2 This is a schematic diagram of the process for histogram statistics using optical ranging methods in existing technologies. For example... Figure 2As shown, for SPAD (cell) 1, the addressing method of TDC (cell) 1 determines the cumulative counting position of SPAD 1 in Memory 1. Specifically, Memory 1 may include 1024 10-bit wide timebins. During continuous exposure of the object, Memory 1 counts the light signals received on SPAD 1 and outputs the statistical data as the actual result. A statistical histogram is generated with the timebin as the minimum scale on the horizontal axis and the vertical axis representing the cumulative count value of each timebin over an exposure period. Similarly, Memory n (the nth storage cell) may include 1024 10-bit wide timebins. During object exposure, Memory 1 counts the light signals received on SPAD n (the nth SPAD cell) and outputs the statistical histogram corresponding to SPAD n.

[0051] Understandably, since this ranging method uses histogram statistics, the size of the memory 160 of the lidar device 100 will become very large when long-distance laser ranging or high resolution is achieved, which will place high storage requirements on the lidar device 100 and result in an excessively large chip area for the ranging chip.

[0052] In view of the problem of excessive chip area in the above-mentioned statistical histogram-based laser ranging method, this application proposes a laser ranging method and a laser ranging device.

[0053] Figure 3 This is a flowchart of a laser ranging method according to an embodiment of this application. Figure 3 As shown, this laser ranging method includes the following steps:

[0054] S10: A first storage space is provided, and an adjustment difference is provided. The first storage space is used to store a piece of data.

[0055] In this application, the first storage space stores data in units of one data item. The storage capacity occupied by this one data item should be understood as including at least the bit width of one TDC (Time-Digital Converter). For example, if the bit width of one TDC is 10, then the bit width of the data stored in the first storage space in this application is at least 10. In this embodiment, a first storage space is provided, and the first data stored in this first storage space is used for numerical comparison. The data for numerical comparison also includes real-time input data that changes over time after being converted by the TDC. This application also includes an adjustment difference, which is used by the first storage space to adjust the comparison result after numerical comparison, so that the value obtained after multiple adjustments is closer to the actual object distance measurement value.

[0056] S20: Laser exposure begins. The data output in real time by the TDC is compared with the first data in the first storage space. Based on the comparison result, the difference between the first data and the adjustment is added or subtracted and stored as updated data in the first storage space. The first data has a preset initial value. The comparison step is stopped when the exposure ends.

[0057] Specifically, after each comparison between the real-time output data of TDC and the first data in the first storage space, the first data in the first storage space will be updated based on the comparison result and an adjustment difference. Specifically, the value in the first storage space will be compensated accordingly based on the numerical difference between the real-time output data of TDC and the first data in the first storage space. This compensation value is the adjustment difference, which can be positive or negative; that is, the adjustment difference can be added or subtracted when the first data is updated.

[0058] The first data has a preset initial value. After comparing the data output by TDC in real time with the first data in the first storage space multiple times, the initial value will converge to the vicinity of the actual object distance measurement value.

[0059] For dTOF lidar, its corresponding statistical histogram follows a Poisson distribution. Most of the seemingly discrete values ​​in these statistical histograms tend to cluster around a fixed value, which represents the distance to the object. From the statistical histogram, the position of the peak represents the distance to the object. In this embodiment, the first data in the continuously updated first storage space and the adjustment difference are used to make the final first data approximate the value corresponding to the peak acquired using the statistical histogram acquisition method. Specifically, this application abandons the traditional statistical histogram method. Instead of recording the data representing the object's measured distance and the photon count value converted by each SPAD through TDC, it compares the real-time output data of TDC with the first data in the first storage space each time it obtains the real-time output data of TDC. Based on the characteristic that the values ​​of statistical histograms mostly concentrate on a certain fixed value, the difference between the values ​​of the real-time output data of TDC and the first data in the first storage space is compensated by adjusting the difference. This makes the updated value of the first data obtained after comparison increasingly closer to the timebin value corresponding to the peak value in the statistical histogram. In this way, after multiple comparisons between the real-time output data of TDC and the values ​​of the first data in the first storage space, the first data in the first storage space will be updated to be closer and closer to the actual object distance measurement value.

[0060] S30: Determine the object distance measurement value based on the value of the first data.

[0061] In one embodiment, after the exposure is completed, the step of comparing the data output by the TDC in real time with the first data in the first storage space will also stop. At this time, the first data stored in the first storage space that was last updated can be used as the object distance measurement value.

[0062] Understandably, after multiple comparisons (the number of times determined by the number of SPAD triggers within the exposure time), the final first data will be very close to the actual object distance measurement value. Compared with the method using statistical histograms, the laser ranging method used in this application embodiment does not require a memory to store the statistical histogram of each SPAD unit. It only uses the first storage space as the storage unit for the first data, which can save a large amount of storage capacity for the photon count values ​​corresponding to the real-time output data of TDC that need to be stored in the middle. This can reduce the use of memory (such as a large amount of SRAM) and significantly reduce the area of ​​the ranging chip.

[0063] In steps S10-S30, a first storage space and an adjustment difference are provided. The data in the first storage space is compared with the data output in real time by the TDC. The adjustment difference is used to convergently adjust and update the data in the first storage space, making the first data in the first storage space closer to the actual object distance measurement value. After exposure, the object distance measurement value can be determined based on the final obtained first data. The error between the final obtained first data and the actual object distance measurement value is small, essentially equivalent to the actual object distance measurement value. The laser ranging method of this application does not require storing statistical histogram data within the ranging chip, effectively reducing storage requirements and significantly reducing the area of ​​the ranging chip.

[0064] Further, in step S20, the data output in real time by the TDC is compared with the first data in the first storage space. Based on the comparison result, the difference between the first data and the adjusted value is added or subtracted and stored as the updated data in the first storage space. Specifically, this includes the following steps:

[0065] S21: Compare the data output by TDC in real time with the first data in the first storage space.

[0066] In one embodiment, the first data in the first storage space can be referred to as PEAK_BIN, representing the timebin (value) corresponding to the peak value in the histogram of the first data. Understandably, in the initial stage of comparing the data output by the TDC in real time with the first data in the first storage space, PEAK_BIN has not yet fully converged, and PEAK_BIN is not actually close to the peak value in the histogram. However, as the number of comparisons increases until the comparison ends, PEAK_BIN will eventually approach the actual object distance measurement value infinitely.

[0067] Further, the preset initial value of the first data can be the middle value of the TDC range. For example, when the TDC range is 10-bit wide and the TDC range is 1024 timebins, the middle value is the 512th timebin. In the embodiments of the present application, presetting the initial value of the first data as the middle value of the TDC range can make the first data converge to the timebin corresponding to the peak in the statistical histogram as soon as possible. For example, assuming that the measured value of the object distance is the distance corresponding to the 150th timebin unit, when the preset initial value of the first data is the middle value of the TDC range (such as 512 timebin units), the first data will converge to the vicinity of the 150th timebin unit after multiple updates.

[0068] S22: If the first data is less than the data output by the TDC in real time, the first data is added with an adjustment difference to obtain updated data, which is stored in the first storage space.

[0069] S23: If the first data is greater than the data output by the TDC in real time, the first data is subtracted by the adjustment difference to obtain updated data, which is stored in the first storage space.

[0070] S24: If the first data is equal to the data output by the TDC in real time, the first data remains stored in the first storage space.

[0071] In steps S22 - S24, it can be expressed as: when TDCdata (the data output by the TDC in real time) > PEAK_BIN, PEAK_BIN(new) = PEAK_BIN(old) + delta; when TDCdata < PEAK_BIN, PEAK_BIN(new) = PEAK_BIN(old) - delta; when TDCdata = PEAK_BIN, PEAK_BIN remains unchanged, where PEAK_BIN (new) refers to the first data updated after comparison, PEAK_BIN(old) refers to the first data during comparison, and delta represents the adjustment difference.

[0072] In steps S21 - S24, the user can update PEAK_BIN according to the comparison result of TDCdata and PEAK_BIN by adjusting the difference delta, so that PEAK_BIN is closer to the timebin corresponding to the peak in the statistical histogram after multiple updates, that is, closer to the actual object detection distance.

[0073] Furthermore, the adjustment difference includes a first adjustment difference and a second adjustment difference. The value of the first adjustment difference is greater than the value of the second adjustment difference. The adjustment difference is changed according to the number of times the TDC receives data. When the number of comparisons reaches a preset threshold, the first adjustment difference is changed to the second adjustment difference.

[0074] In one embodiment, delta1 and delta2 are provided, where delta1 is greater than delta2. At the initial stage of the comparison, the larger delta1 value is used to facilitate rapid convergence of the first data. In the middle or later stages of the comparison, to ensure more stable convergence of the first data and to approximate the actual object detection distance, the smaller delta2 value is used. This further improves the efficiency of updating the first data and reduces the gap between the first data and the actual object detection distance. The preset threshold can be determined based on the number of comparisons. For example, the preset threshold can be 1 / 5 or 1 / 4 of the total number of comparisons. That is, in the first 1 / 5 or 1 / 4 of the comparison, the larger delta1 value is used, and in the later stages, the smaller delta2 value is used. Furthermore, the range of the difference is adjusted to 0.5-10; for example, delta1 is specifically set to 5, and delta2 is specifically set to 1.

[0075] Furthermore, the laser ranging method also includes the following steps:

[0076] S40: A second storage space is provided, and the storage capacity of the second storage space is greater than that of the first storage space.

[0077] In one embodiment, to further improve the accuracy of the final object distance measurement, a second storage space can be added to the first storage space. The storage capacity of the second storage space can be N times the storage capacity of the first storage space. The second storage space can store some of the newer PEAK_BINs that have just been updated; that is, it can be understood that the second storage space can store N historical PEAK_BINs.

[0078] Furthermore, the first storage space is a part of the second storage space, which is a shift register capable of storing N data items. The first storage space occupies either the first or last position of the second storage space. In one embodiment, the first storage space is a part of the second storage space and is located at one end of the second storage space. Thus, utilizing the characteristics of the shift register, after each update of PEAK_BIN, the newly updated PEAK_BIN (new) is stored as the first data in the first storage space, and the newly updated PEAK_BIN (old) is moved to the next storage space of the first storage space. Other storage portions of the second storage space are also shifted and replaced accordingly. When the second storage space is full, the earliest stored N+1th PEAK_BIN is removed. In other words, the second storage space can store a maximum of N of the latest PEAK_BINs, while the first storage space stores PEAK_BINs updated from the most recent value comparison history.

[0079] S50: The difference between the first data and the adjustment is added or subtracted and stored as updated data in the first storage space, and simultaneously stored in the second storage space. When the exposure ends, the storage capacity of the second storage space contains N historical values ​​of the first data, where N is a positive integer and the value of N is less than the maximum range of TDC.

[0080] In one embodiment, updated data (i.e., data obtained by comparing the updated PEAK_BIN) is stored in a first storage space and simultaneously stored in a second storage space. It is understood that the first storage space may be a part of the second storage space, or the second storage space may include storage spaces containing the same content as the first storage space, and updates are also stored in the second storage space when the data in the first storage space is updated.

[0081] The second storage space can store N values ​​of the same size as the first data. At the end of the exposure, the second storage space saves the N most recent PEAK_BIN values, which are the N historical values ​​of the first data in the most recent numerical comparison. Understandably, since the distance range of photometry is limited, the value of N should be limited to less than the maximum range of TDC.

[0082] S60: Calculate the average of the historical values ​​of the N first data points.

[0083] S70: Determine the object distance measurement value based on the average of the historical values ​​of N first data points.

[0084] In one embodiment, compared to steps S10-S30, steps S40-S70 expand a second storage space on top of the first storage space. This second storage space can store the latest N historical values ​​of the first data; that is, the values ​​stored in the second storage space are the first data updated after the last N comparisons. In this embodiment, the object distance measurement value can be determined by rounding down the average of the N historical values ​​of the first data. This is more fault-tolerant than steps S10-S30, which use the last first data to determine the object distance measurement value, making the obtained object distance measurement value closer to the actual object distance measurement value.

[0085] Figure 4 This is a schematic diagram of the structure implementing optical ranging in an embodiment of this application. For example... Figure 4 As shown, the lidar device 100 includes a laser emitting device 110, a control module 120, a SPAD module 140, a TDC module 150, a comparator 160, an up / down counter 170, a register 180, and an averaging circuit 190. In optical ranging, the laser emitting device 110 emits a laser beam, which illuminates a target object 130 through a lens, and the target object 130 is continuously exposed. During the exposure of the target object 130, photons are reflected back to the lidar device 100 through the lens. The lidar device 100 receives the returned light signal through the SPAD module 140 and converts the time information into a quantized multi-bit digital signal through the TDC module 150, outputting it to the comparator 160 in real time. The comparator 160 compares the data transmitted in real time by the TDC with the first data stored in the register 180, and adjusts the difference in the comparison result using the up / down counter 170, storing the modified first data in the register 180. The register 180 may include a second storage space containing the first storage space. Finally, the averaging circuit 190 calculates the average of the N historical first data points to obtain the object's distance information. The control module 120 controls the SPAD module 140 and the TDC module 150, enabling the data from the TDC module 150 to be fed back to the comparator 160 in real time according to the optical signals received by the SPAD.

[0086] Figure 5 This is a schematic diagram illustrating the process of implementing optical ranging in an embodiment of this application. For example... Figure 5As shown, after receiving the light signal, SPAD (unit) 1 sends the signal to TDC (unit) 1 for conversion and sends the converted data to comparator 1 in real time for comparison. The numerical update is completed by the up / down counter circuit 1. Another data point for comparison is retrieved from the register, specifically the first data in the first storage space of the register. After exposure, the register stores multiple (e.g., N=20) historical data points of the first data, i.e., multiple recently updated historical data points. These historical data points of the first data are sent to the averaging circuit 1 to obtain the timebin value M1. Similarly, SPADn represents the nth SPAD unit in the SPAD module, and its optical ranging process is similar to that of SPAD1, which will not be described further here.

[0087] Will Figure 4 , Figure 5 and Figure 1 , Figure 2 By comparison, it can be seen that the memory and memory control circuitry that originally occupied most of the chip area will be replaced by comparators, up / down counters, and averaging circuits. The benefits of this include, but are not limited to:

[0088] The chip does not need to store statistical histogram data internally, eliminating the need for SRAM memory and allowing for the use of a very small register, significantly reducing chip area. This reduction in chip area also leads to a significant decrease in power consumption and cost. Compared to SRAM memory, which requires at least two clock cycles to complete a data accumulation (one read cycle, one write cycle), the up / down counter circuit can perform data addition or subtraction calculations in a single cycle, thus doubling the data processing speed of the entire TDC module and doubling the overall chip data throughput. Since the statistical histogram is no longer used to calculate depth values, but instead the chip directly outputs depth data (timebin values), the chip's data output and the subsequent computational workload of the statistical histogram (such as matched filtering and peak finding algorithms) are significantly reduced, improving the chip's processing efficiency.

[0089] Furthermore, the number of N can be specifically set to 2-30.

[0090] Furthermore, in this embodiment, by increasing the number of N values ​​or decreasing the adjustment difference, the accuracy of the object distance measurement can be effectively improved. In one embodiment, when it is necessary to further improve the accuracy of the object distance measurement, the number of N values ​​can be set higher in advance, so that the average of the historical values ​​of the N first data points is closer to the actual object distance measurement. Alternatively, the adjustment difference can be reduced to make the first data converge more accurately, thus obtaining a more accurate object distance measurement.

[0091] In this embodiment, a first storage space and an adjustment difference are provided. The first storage space is used to store a data point, and the adjustment difference can be used to convergently adjust and update the data in the first storage space so that the first data in the first storage space is closer to the actual object distance measurement value. Specifically, at the start of laser exposure, the data output in real time by the TDC is compared with the first data in the first storage space. Based on the comparison result, the first data plus or minus the adjustment difference is stored in the first storage space as updated data. The first data has a preset initial value. The comparison step is stopped when the exposure ends. By comparing the data output in real time by the TDC with the first data in the first storage space each time, the characteristics of the TDC output data conforming to the Poisson distribution can be utilized to continuously update and adjust the first data through each numerical comparison, so that the first data at the initial value converges quickly to near the actual object distance measurement value through numerical comparison. Finally, the object distance measurement value is determined based on the value of the first data. When the data output in real time by the TDC is compared with the first data in the first storage space a sufficient number of times, the error between the final first data and the actual object distance measurement value is small, and it is basically equivalent to the actual object distance measurement value. When using this laser ranging method, there is no need to store statistical histogram data inside the ranging chip, which can reduce or eliminate the use of SRAM to store data, and the area of ​​the ranging chip is significantly reduced.

[0092] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0093] This application provides a laser ranging device. The laser ranging device includes:

[0094] A laser emitter, used to emit laser light;

[0095] SPAD array, used to receive optical signals;

[0096] TDC arrays are used to convert the time value of optical signal flight into digital signals.

[0097] A comparator is used to compare the data output in real time from one of the TDCs with the first data in the first storage space;

[0098] An up / down counter is used to add or subtract an adjustment difference to the first data based on the comparison result and save it as updated data in the first storage space, wherein the adjustment difference is preset.

[0099] The first storage space is used to store the first data, which has an initial value preset.

[0100] The processing circuit is used to determine the object distance measurement value based on the first data.

[0101] Furthermore, the laser ranging device also includes:

[0102] A second storage space and a computing unit, wherein the storage capacity of the second storage space is greater than that of the first storage space;

[0103] The up / down counter is also used to save the adjustment difference of the first data as updated data in the first storage space and simultaneously in the second storage space. When the exposure ends, the storage capacity of the second storage space stores N historical values ​​of the first data, where N is a positive integer and the value of N is less than the maximum range of TDC.

[0104] The calculation unit is used to calculate the average of the historical values ​​of N first data points;

[0105] The processing circuit is also used to determine the object distance measurement value based on the average of the historical values ​​of N first data.

[0106] In this embodiment, a first storage space and an adjustment difference are provided. The first storage space is used to store a data point, and the adjustment difference can be used to convergently adjust and update the data in the first storage space so that the first data in the first storage space is closer to the actual object distance measurement value. Specifically, at the start of laser exposure, the data output in real time by the TDC is compared with the first data in the first storage space. Based on the comparison result, the first data plus or minus the adjustment difference is stored in the first storage space as updated data. The first data has a preset initial value. The comparison step is stopped when the exposure ends. By comparing the data output in real time by the TDC with the first data in the first storage space each time, the characteristics of the TDC output data conforming to the Poisson distribution can be utilized to continuously update and adjust the first data through each numerical comparison, so that the first data at the initial value converges quickly to near the actual object distance measurement value through numerical comparison. Finally, the object distance measurement value is determined based on the value of the first data. When the data output in real time by the TDC is compared with the first data in the first storage space a sufficient number of times, the error between the final first data and the actual object distance measurement value is small, and it is basically equivalent to the actual object distance measurement value. When using this laser ranging method, there is no need to store statistical histogram data inside the ranging chip, which can reduce or eliminate the use of SRAM to store data, and the area of ​​the ranging chip is significantly reduced.

[0107] Furthermore, in this embodiment, a second storage space can be extended based on the first storage space. This second storage space can store the latest N historical values ​​of the first data, that is, the value stored in the second storage space is the first data updated after the last N comparisons. In this embodiment, the object distance measurement value can be determined by rounding down the average of the N historical values ​​of the first data. This is more fault-tolerant than using the last first data to determine the object distance measurement value in steps S10-S30, making the obtained object distance measurement value closer to the actual object distance measurement value.

[0108] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0109] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A laser ranging method, characterized in that, include: A first storage space is provided, and an adjustment difference is provided. The first storage space is used to store a piece of data. When laser exposure begins, the data output in real time by the TDC is compared with the first data in the first storage space. Based on the comparison result, the first data is added to or subtracted from the adjustment difference and stored as updated data in the first storage space. The first data has a preset initial value. The comparison step stops when the exposure ends. The type of the first data is a timebox, and the type of the adjustment difference is a timebox. The adjustment difference includes a first adjustment difference and a second adjustment difference. The value of the first adjustment difference is greater than the value of the second adjustment difference. The adjustment difference changes according to the number of times the TDC receives data. When the number of comparisons is less than a preset threshold, the adjustment difference is the first adjustment difference. When the number of comparisons reaches the preset threshold, the adjustment difference is the second adjustment difference. The object distance measurement value is determined based on the value of the first data time box.

2. The method according to claim 1, characterized in that, The method further includes: A second storage space is provided, and the storage capacity of the second storage space is greater than that of the first storage space; The first data is added to or subtracted from the adjustment difference and stored as updated data in the first storage space, and simultaneously stored in the second storage space. When the exposure ends, the storage capacity of the second storage space stores N historical values ​​of the first data, where N is a positive integer and the value of N is less than the maximum range of the TDC. Calculate the average of N historical values ​​of the first data; The distance measurement of the object is determined based on the average of the N historical values ​​of the first data.

3. The method according to claim 2, characterized in that, The first storage space is a part of the second storage space, which is a shift register capable of storing N data. The first storage space occupies the first or last position of the second storage space.

4. The method according to claim 1, characterized in that, The step of comparing the data output in real time by the TDC with the first data in the first storage space, and based on the comparison result, adding or subtracting the adjustment difference from the first data as updated data and storing it in the first storage space, includes: Compare the data output in real time by the TDC with the first data in the first storage space; If the first data is less than the data output by the TDC in real time, the first data is added to the adjustment difference to obtain the updated data, which is then stored in the first storage space. If the first data is greater than the data output by the TDC in real time, then the first data minus the adjustment difference is used to obtain the updated data, which is then stored in the first storage space. If the first data is equal to the data output in real time by the TDC, then the first data is still stored in the first storage space.

5. The method according to claim 1, characterized in that, The initial value preset for the first data is the midpoint of the range of the TDC.

6. The method according to claim 2, characterized in that, The accuracy of the object distance measurement can be improved by increasing the number of N values ​​or decreasing the adjustment difference.

7. The method according to claim 6, characterized in that, The number of N ranges from 2 to 30, and the adjustment difference ranges from 0.5 to 10.

8. A laser ranging device, characterized in that, include: A laser emitter, used to emit laser light; SPAD array, used to receive optical signals; TDC arrays are used to convert the time value of optical signal flight into digital signals. A comparator is used to compare the data output in real time from one of the TDCs with the first data in the first storage space; An up / down counter is used to add or subtract an adjustment difference to the first data as updated data and store it in the first storage space based on the comparison result. The adjustment difference is preset, the first data is of type timebox, and the adjustment difference is of type timebox. The adjustment difference includes a first adjustment difference and a second adjustment difference, where the value of the first adjustment difference is greater than the value of the second adjustment difference. The adjustment difference changes according to the number of times the TDC receives data. Specifically, when the number of comparisons is less than a preset threshold, the adjustment difference is the first adjustment difference; when the number of comparisons reaches the preset threshold, the adjustment difference is the second adjustment difference. The first storage space is used to store the first data, which has an initial value preset. The processing circuit is used to determine the object distance measurement value based on the value of the first data time box.

9. The apparatus according to claim 8, characterized in that, It also includes a second storage space and a computing unit, wherein the storage capacity of the second storage space is greater than that of the first storage space; The up / down counter is also used to add or subtract the adjustment difference from the first data as updated data and store it in the first storage space, and at the same time store it in the second storage space. When the exposure ends, the storage capacity of the second storage space stores N historical values ​​of the first data, where N is a positive integer and the value of N is less than the maximum range of the TDC. The calculation unit is used to calculate the average value of N historical values ​​of the first data; The processing circuit is further configured to determine the object distance measurement value based on the average of the historical values ​​of the N first data.

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