WO2023198043A1

WO2023198043A1 - Laser ranging method and device

Info

Publication number: WO2023198043A1
Application number: PCT/CN2023/087577
Authority: WO
Inventors: 唐佳捷; 贾捷阳
Original assignee: 深圳市灵明光子科技有限公司
Priority date: 2022-04-13
Filing date: 2023-04-11
Publication date: 2023-10-19
Also published as: CN115128623A

Abstract

A laser ranging method and device. The laser ranging method comprises: providing a first storage space, and setting an adjustment difference value, the first storage space being used for storing one data; starting laser exposure, comparing data outputted by a TDC in real time with first data in the first storage space, according to the comparison result, adding/subtracting the first data to/from the adjustment difference value, taking the result as updated data and storing same in the first storage space, wherein an initial value is preset for the first data, and the execution of the comparison step stops until the exposure is finished; and determining an object distance measured value according to the value of the first data. According to the laser ranging method, the use of a memory can be reduced, so that the area of a ranging chip is remarkably reduced.

Description

Laser ranging method and device

Technical field

The present application relates to the technical field of optical distance measurement, and in particular to a laser distance measurement method and device.

Background technique

Currently, lidar measurement systems based on dTOF (Directtimeofflight, direct time of flight) measurements usually include a transmitter and a receiver. The receiver usually uses a SPAD (Single Photon Avalanche Diode) array to receive the return The light signal is converted into a quantized multi-bit digital signal through TDC (Time-to-Digital Converter), and then the distance-based distance is drawn through long-term exposure and TDC trigger accumulation value. Statistical histogram, so as to obtain the distance information of the object based on the statistical histogram. However, this laser ranging method generally requires a complete statistical histogram for one pixel. As the resolution of area array lidar becomes higher and higher, the post-processing TDC array and memory (such as SRAM (static random access memory) The larger the memory, the larger the Static Random-Access Memory)), which results in the chip area of the ranging chip being too large.

Contents of the invention

In view of this, embodiments of the present application provide a laser ranging method and device to solve the problem of excessive chip area in the traditional statistical histogram-based laser ranging method.

In a first aspect, embodiments of the present application provide a laser ranging method, which method includes:

A first storage space is provided, and an adjustment difference value is provided, and the first storage space is used to store a piece of data;

When the laser exposure starts, the real-time output data of the TDC is compared with the first data in the first storage space. According to the comparison result, the first data plus or minus the adjustment difference is saved as updated data in the first storage space. In the first storage space, the first data is preset with an initial value, and the comparison step is stopped until the exposure is completed;

Based on the value of said first data, an object distance measurement is determined.

Based on the above aspects and any possible implementation, an implementation is further provided, and 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 plus or minus the adjustment difference is saved in the first storage space as updated data, and is simultaneously saved in the second storage space. When the exposure ends, the storage capacity of the second storage space N historical values of the first data are stored, 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 object distance measurement value is determined based on the average of the N historical values of the first data.

Based on the above aspects and any possible implementation, an implementation is further provided, the first storage space is a part of the second storage space, and the second storage space is a storage space capable of storing N pieces of data. A shift register, the first storage space occupies the first position or the last position of the second storage space.

Based on the above aspect and any possible implementation, an implementation is further provided, in which the data output by TDC in real time is compared with the first data in the first storage space, and according to the comparison result, the The first data plus or minus the adjustment difference is stored in the first storage space as updated data, including:

Compare the data output by the TDC in real time 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 updated data, which is stored in the first storage space;

If the first data is greater than the data output by the TDC in real time, the adjusted difference is subtracted from the first data to obtain the updated data, which is stored in the first storage space;

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

According to the above aspects and any possible implementation, an implementation is further provided, in which the initial value preset by the first data is the middle value of the measurement range of the TDC.

According to the above aspects and any possible implementation, an implementation is further provided, the adjustment difference includes a first adjustment difference and a second adjustment difference, and the first adjustment difference has a value greater than the The value of the second adjustment difference. The adjustment difference is changed according to the number of times the TDC is received. When the number of comparisons reaches a preset threshold, the first adjustment difference is changed to the second adjustment difference. .

According to the above aspect and any possible implementation, an implementation is further provided to improve the accuracy of the object distance measurement value by increasing the number of N or reducing the adjustment difference.

Based on the above aspects and any possible implementation, an implementation is further provided, the number of N ranges from 2 to 30, and the adjustment difference ranges from 0.5 to 10.

In a second aspect, embodiments of the present application provide a laser ranging device, which includes:

Laser transmitter, used to emit laser;

SPAD array, used to receive optical signals;

TDC array, used to convert the flight time value of the optical signal into a digital signal;

A comparator, used to compare the real-time output data of one of the TDCs with the first data in the first storage space;

An up/down counter, used to save the first data addition and subtraction adjustment difference as updated data in the first storage space according to the comparison result, wherein the adjustment difference is preset;

The first storage space is used to save the first data, and the first data is preset with an initial value;

A processing circuit configured to determine an object distance measurement value based on the first data.

Further, the device further includes a second storage space and a computing unit, wherein the second storage space has a greater storage capacity than the first storage space;

The up/down counter is also used to add and subtract the adjustment difference to the first data and save it in the first storage space as updated data, and simultaneously save it in the second storage space. At the end, 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 an average of N historical values of the first data;

The processing circuit is also configured to determine the object distance measurement value based on the average of the N historical values of the first data.

In the embodiment of the present application, there is a first storage space and an adjustment difference value. The first storage space is used to store a piece of data. The adjustment difference value can be used to perform convergent adjustment and update on the data in the first storage space, so that the third The first data in a storage space is closer to the actual object distance measurement value; specifically, when the laser exposure starts, the data output by the TDC in real time is The data is compared with the first data in the first storage space, and according to the comparison result, the plus or minus adjustment difference of the first data is saved in the first storage space as updated data, wherein the first data is preset with an initial value, Until the end of the exposure, the comparison step is stopped, and the data output in real time by each TDC is compared with the first data in the first storage space. The data output by the TDC can be used to conform to the characteristics of the Poisson distribution, and the data can be continuously compared through each numerical comparison. The first data is updated and adjusted accordingly, so that the first data quickly converges to the vicinity of the actual object distance measurement value through numerical comparison at the initial value; finally, the object distance measurement value is determined based on the value of the first data. When the TDC real-time output data and After the number of comparisons of the first data in the first storage space is sufficient, the error between the finally obtained first data and the actual object distance measurement value is small, and is basically equal to the actual object distance measurement value. When using this laser ranging method, there is no need to save statistical histogram data inside the ranging chip, SRAM can be reduced or not used to save data, and the area of the ranging chip is significantly reduced.

Description of the drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting any creative effort.

Figure 1 is a schematic structural diagram of optical ranging in the prior art;

Figure 2 is a schematic flow chart of using optical ranging methods to achieve histogram statistics in the prior art;

Figure 3 is a flow chart of a laser ranging method in an embodiment of the present application;

Figure 4 is a schematic structural diagram of optical ranging in an embodiment of the present application;

FIG. 5 is a schematic flowchart of realizing optical ranging in an embodiment of the present application.

Detailed ways

In order to better understand the technical solution of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

It should be clear that the described embodiments are only some of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

The terminology used in the embodiments of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application. As used in the embodiments and the appended claims, the singular forms "a," "the" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

It should be understood that the term "and/or" used in this article is just a way to describe the same field of associated objects, indicating that there can be three relationships, for example, A and/or B, which can mean: A alone exists, and A exists at the same time and B, there are three cases of B alone. In addition, the character "/" in this article generally indicates that the related objects are an "or" relationship.

It should be understood that although the terms first, second, third, etc. may be used to describe the preset range and the like in the embodiments of the present application, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present application, the first preset range may also be called the second preset range, and similarly, the second preset range may also be called the first preset range.

Depending on the context, the word "if" as used herein may be interpreted as "when" or "when" or "in response to determination" or "in response to detection." Similarly, depending on the context, the phrase "if determined" or "if detected (stated condition or event)" may be interpreted as "when determined" or "in response to determination" or "when (stated condition or event) is detected" or "in response to detection (stated condition or event)."

Figure 1 is a schematic structural diagram of optical ranging in the prior art. As shown in FIG. 1 , 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 . When realizing optical distance measurement, the laser emitting device 110 emits laser light to illuminate the target object 130 with photons through the lens, and the target object 130 is continuously exposed. During exposure of target object 130, photons are illuminated through the lens back to lidar device 100 by reflection. The lidar device 100 receives the returned optical signal through the SPAD module 140, and converts the time information into a quantized multi-bit digital signal through the TDC module 150, and then draws a distance-based dynamic histogram based on the long-term exposure and TDC trigger accumulation value. Figure, thereby obtaining the distance information of the target object 130. Among them, the control module 120 is used to control the SPAD module 140, the TDC module 150 and the memory 160 to complete the storage of statistical histogram data.

It can be understood that the SPAD module 140 includes many SPAD units, and each SPAD unit can realize the induction detection of photons. The size of the SPAD array in the SPAD module 140 (the number of SPAD units included) characterizes the ranging chip. The resolution is, for example, 320*240, or 640*480. When the resolution is higher, the TDC module 150 and the memory 160 that complete histogram statistics at the subsequent stage require higher scale and storage capacity. Generally, one SPAD unit corresponds to a complete statistical histogram. In a statistical histogram, the abscissa represents time (it can also represent distance, and D=C*TOF/2, where D represents distance, TOF is digital information that is converted into time based on time information, and C represents the speed of light) , where the minimum scale on the abscissa represents a time bin (time bin), corresponding to the minimum accuracy of TDC; the ordinate represents the cumulative count value of each time bin within a period of time. It can be seen from this that for the storage requirements of the ranging chip, to achieve long-distance laser ranging, the memory depth is required to be large enough (can store a sufficient number of timebins); to achieve a high signal-to-noise ratio, the memory is required The bits are wide enough (can store larger accumulated count values). Assume there is a dTOF receiver with 80x60 = 4800 pixels (SPAD unit), the TDC data bit width is 10 bits, the minimum accuracy is 0.1ns (corresponding to a distance of 1.5cm), and each time bin is represented by an 8-bit count value (maximum count value is 255), for the requirement that the furthest detection distance is 6m (corresponding to 400 timebins, 400*1.5cm=6m), the minimum memory size required for one frame of image is: 400*8*4800=15.36Mbit=1.92Mbyte, If the resolution changes to 320x240=76800 and the maximum detection distance is still 6m, the memory size required for one frame of image becomes: 400*8*76800=245.76Mbit=30.72Mbyte. It can be seen that with the resolution of the area array lidar As the rate becomes higher and higher, the TDC array and memory size for post-processing will become larger, and the chip area of the ranging chip will also increase accordingly.

Figure 2 is a schematic flowchart of using optical ranging methods to implement histogram statistics in the prior art. As shown in Figure 2, for SPAD (unit) 1, it determines the cumulative count position that SPAD1 needs to be in Memory1 (storage unit 1) through TDC (unit) 1 by using addressing. Among them, Memory1 can specifically include 1024 timebins with a width of 10 bits. When the object is continuously exposed, Memory1 will count the light signals received on SPAD1, and finally output the statistical data as the actual result, with timebin as the abscissa. On the minimum scale, a statistical histogram is generated with the ordinate as the cumulative count value of each timebin within a period of exposure. Similarly, Memoryn (nth storage unit) can include 1024 10-bit wide timebins. During the object exposure, Memory1 will count the light signals received on SPADn (nth SPAD unit) and store the SPADn The corresponding statistical histogram output.

It is understandable that since the ranging method adopts histogram statistics, when long-distance laser ranging or high resolution is achieved, the size of the memory 160 of the lidar device 100 will become very large, which is detrimental to the lidar. The device 100 has high storage requirements, which will result in an excessively large chip area for the ranging chip.

In view of the problem that the chip area is too large in the above statistical histogram implementation of laser ranging method, this application Please propose a laser ranging method and laser ranging device.

Figure 3 is a flow chart of a laser ranging method in an embodiment of the present application. As shown in Figure 3, the laser ranging method includes the following steps:

S10: There is a first storage space and an adjustment difference value. The first storage space is used to store one piece of data.

The unit of data stored in the first storage space is one, and the storage capacity occupied by one piece of data should be understood as a capacity that at least includes the bit width of one TDC. For example, if the bit width of one TDC is 10, then this The bit width of the data stored in the first storage space in the application is at least 10. In the embodiment of the present application, a first storage space is provided, and the first data stored in the first storage space is used for numerical comparison. The data for numerical comparison also includes real-time input and TDC-converted data that changes with time. This application also provides an adjustment difference value, which is used in 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.

S20: The laser exposure starts, and the data output by the TDC in real time is compared with the first data in the first storage space. According to the comparison result, the addition and subtraction adjustment difference of the first data is saved in the first storage space as updated data. Among them, the first data is preset with an initial value, and the comparison step is stopped until the exposure ends.

Among them, after each time the data output by the TDC in real time is compared with the first data in the first storage space, the first data in the first storage space will be updated according to the comparison result and the adjustment difference. Specifically, the numerical value of the first storage space will be compensated accordingly according to the numerical difference between the data output by the TDC in real time and the first data of the first storage space, and the compensated numerical value is the adjustment difference, wherein the compensation can be It is positive compensation or negative compensation, that is, the adjustment difference can be added or subtracted when the first data is updated.

The first data is preset with an initial value, which will converge to near the actual object distance measurement value after comparing the data output by the TDC in real time multiple times with the first data in the first storage space.

For dTOF lidar, its corresponding statistical histogram satisfies the Poisson distribution. Most of the values of these seemingly discrete statistical histograms will be concentrated around a certain fixed value, and this fixed value is the distance value corresponding to the object. From the statistical histogram, the position of the peak represents the distance corresponding to the object. . In the embodiment of the present application, the constantly updated first data in the first storage space and the adjusted difference are used, so that the finally obtained first data is close to the value corresponding to the wave peak collected using the statistical histogram collection method. Specifically, this application abandons the traditional statistical histogram statistical method. There is no need to record the data representing the object measurement distance and the photon count value converted by each SPAD through TDC. Instead, each time the data output by TDC is obtained in real time, the The output data is compared with the first data in the first storage space. Based on the characteristic that most of the statistical histogram values are concentrated at a certain fixed value, the real-time output data of TDC is compared with the first data in the first storage space. For the numerical difference after comparing the data, the first data is compensated by adjusting the difference, so that the value of the updated first data obtained after the comparison is closer and closer to the timebin value corresponding to the peak value in the statistical histogram. In this way, After multiple times of TDC real-time output data and the first data value in the first storage space are compared, the first data in the first storage space will be updated to be closer and closer to the actual object distance measurement value.

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

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 last updated data stored in the first storage space can be A data as an object distance measurement.

It is understandable that after multiple comparisons (the number of times is determined by the number of SPAD triggers during the exposure time), the first data finally obtained will be very close to the actual object distance measurement value. Compared with the statistical histogram method, this application The laser ranging method adopted in the embodiment does not need to be equipped with a memory to store the statistical histogram of each SPAD unit. It only uses the first storage space as the storage unit of the first data, which can save a large amount of TDC real-time output that needs to be stored in the middle. The storage capacity of the photon count value corresponding to the data can reduce the use of memory (such as a large amount of SRAM) and significantly reduce the area of the ranging chip.

In steps S10-S30, a first storage space and an adjustment difference are provided. By numerically comparing the first data in the first storage space with the data output by the TDC in real time, the adjustment difference is used to compare the data in the first storage space. Perform convergence adjustment and update to make the first data in the first storage space closer to the actual object distance measurement value. After the exposure is completed, the object distance measurement value can be determined based on the finally obtained first data, which is finally obtained The error between the first data and the actual object distance measurement value is small, and is basically the same as the actual object distance measurement value. The laser ranging method of the present application does not need to save statistical histogram data inside the ranging chip, which can effectively reduce storage requirements and significantly reduce the area of the ranging chip.

Further, in step S20, the data output by the TDC in real time is compared with the first data in the first storage space, and based on the comparison result, the first data plus or minus adjustment difference is saved in the first storage space as updated data. within, specifically including the following steps:

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

In one embodiment, the first data in the first storage space may be called PEAK_BIN, which represents the timebin (value) corresponding to the peak value in the histogram corresponding to the first data. It is understandable that in the initial stage when the data output by TDC in real time is compared with the first data in the first storage space, PEAK_BIN has not completely converged, and PEAK_BIN is not actually close to the peak value in the histogram. However, with the number of comparisons, increase until the end, and eventually PEAK_BIN will be infinitely close to the actual object distance measurement value.

Further, the initial value preset by the first data may be an intermediate value of the TDC measurement range. For example, when the TDC measurement range is 10 bits wide, and the TDC measurement range is 1024 timebins, the 512th timebin can be taken as the middle value. In the embodiment of the present application, the initial value of the first data is preset to the middle value of the TDC range, so that the first data can converge to the time bin corresponding to the peak value in the statistical histogram as quickly as possible. For example, assuming that the object distance measurement value is the distance corresponding to the 150th timebin unit, then when the initial value preset for the first data is the middle value of the TDC range (such as 512 timebin units), the first data will be processed multiple times after After the update, it will converge from the middle value of the TDC range to around 150 timebin units.

S22: If the first data is smaller than the data output by TDC in real time, add the adjustment difference to the first data to obtain updated data, which is stored in the first storage space.

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

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

In steps S22-S24, it can be expressed as: when TDCdata (TDC real-time output data)>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.

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

Further, the adjustment difference value includes a first adjustment difference value and a second adjustment difference value. The value of the first adjustment difference value is greater than the value of the second adjustment difference value. The adjustment difference value changes according to the number of TDC receptions, wherein, when compared When the number of times reaches the preset threshold, the first adjustment difference value is changed to the second adjustment difference value.

In one embodiment, delta1 and delta2 are provided, where the value of delta1 is greater than the value of delta2. In the initial stage of comparison, delta1 with a larger value can be used to make the first data converge quickly. In the intermediate stage of comparison or In the later stage, in order for the first data to converge more stably and close to the actual object detection distance, a smaller delta2 value can be used. In this way, the efficiency of the first data update can be further improved, and the first data can be closer to the actual object detection distance. The gap between them is smaller. Among them, the preset threshold can be determined according to the number of comparisons. For example, the preset threshold takes 1/5 or 1/4 of the total number of comparisons, that is, in the first 1/5 or 1/4 stage of comparison, the larger value delta1 is used. In later stages, delta2 with a smaller value is used. Further, the range of the adjustment difference is 0.5-10. For example, delta1 is specifically set to 5, and delta2 is specifically set to 1.

Further, the laser ranging method also includes the following steps:

S40: There is a second storage space, and the storage capacity of the second storage space is greater than that of the first storage space.

In one embodiment, in order to further improve the accuracy of the final object distance measurement value, the first storage space can be expanded into a second storage space. The storage capacity of the second storage space may 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 and replaced. That is, it can be understood that the second storage space can store PEAK_BINs of N historical records.

Further, the first storage space is part of the second storage space, the second storage space is a shift register capable of storing N pieces of data, and the first storage space occupies the first position or the last position of the second storage space. In one embodiment, the first storage space is part of the second storage space and is provided at one of two ends of the second storage space. In this way, the characteristics of the shift register can be used. After each update of PEAK_BIN, the newly updated PEAK_BIN (new) is stored in the first storage space as the first data, and the newly updated PEAK_BIN (old) is moved into the first storage space. In the next storage space of one storage space, other storage parts of the second storage space are also shifted and replaced. When the second storage space is full, the earliest stored N+1 PEAK_BIN will be removed, and That is to say, it is understood that the second storage space can store up to N latest PEAK_BINs, and the first storage space stores PEAK_BINs updated in the recent numerical comparison history.

S50: Save the first data addition and subtraction adjustment difference as updated data in the first storage space and simultaneously in the second storage space. At the end of the exposure, the storage capacity of the second storage space holds N first The historical value of the data, where N is a positive integer and the value of N is less than the maximum range of TDC.

In one embodiment, the updated data (that is, the updated PEAK_BIN by comparison) will be stored in the first storage space and simultaneously stored in the second storage space. It can be understood that the first storage space can be set as a part of the second storage space, or the second storage space includes the same storage space as the first storage space. When the first storage space data is updated, the second storage space Also updated and saved.

The second storage space can store N values with the same size as the first data. At the end of the exposure, the second storage space saves the N latest PEAK_BIN, that is, the historical values of the N first data in the recent numerical comparison. Understandably, since the distance range of optical measurement is limited, the value of N should be limited to a maximum range smaller than TDC.

S60: Calculate the average of the historical values of the N first data.

S70: Determine the object distance measurement value based on the average of the historical values of the N first data.

In one embodiment, compared with steps S10-S30, steps S40-S70 expand the first storage space based on the first storage space. A second storage space is displayed, which 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 the embodiment of the present application, according to the average value of the historical values of N first data, the average value can be rounded to determine the object distance measurement value. In this way, compared with steps S10-S30, the last first data is used to determine The object distance measurement value is more error-tolerant, making the object distance measurement value closer to the actual object distance measurement value.

FIG. 4 is a schematic structural diagram for realizing optical ranging in an embodiment of the present application. As shown in FIG. 4 , 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 . When realizing optical distance measurement, the laser emitting device 110 emits laser light to illuminate the target object 130 with photons through the lens, and the target object 130 is continuously exposed. During exposure of target object 130, photons are illuminated through the lens back to lidar device 100 by reflection. The lidar device 100 receives the returned optical signal through the SPAD module 140 and converts the time information into a quantized multi-bit digital signal through the TDC module 150 and outputs 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, changes the comparison result by adjusting the difference through the up/down counter 170, and stores the modified first data in the register 180 , wherein the register 180 may include a second storage space including the first storage space. Finally, the averaging circuit 190 performs averaging calculation on the N historical first data to obtain the distance information of the object. Among them, the control module 120 is used to control the SPAD module 140 and the TDC module 150, so that the data on the TDC module 150 can be fed back to the comparator 160 in real time according to the SPAD received optical signal.

FIG. 5 is a schematic flowchart of realizing optical ranging in an embodiment of the present application. As shown in Figure 5, after receiving the optical 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 and passes through the up/down counter circuit 1 The numerical update is completed, in which another data used for comparison is searched from the register, and what is searched is the first data in the first storage space in the register. After the exposure is completed, there will be multiple (for example, N=20) historical data of the first data stored in the register, that is, multiple historical data that have just been updated recently. These historical data of the first data will be sent to the average In circuit 1, the timebin value M1 will be obtained. Similarly, SPADn represents the nth SPAD unit in the SPAD module. Its optical ranging process is similar to SPAD1 and will not be described again here.

Comparing Figures 4 and 5 with Figures 1 and 2, we can see that the memory and memory control circuit that originally occupied most of the chip area will be replaced by comparators, up/down counters, and averaging circuits. This will bring Future benefits include but are not limited to:

There is no need to save statistical histogram data inside the chip. SRAM memory can no longer be used to save data. A very small register can be used. The chip area is significantly reduced. While the chip area is reduced, the chip power consumption and cost are significantly reduced. Compared with SRAM The memory needs at least 2 beats to complete a data accumulation (one beat for reading, one beat for writing). The addition and subtraction counter circuit can realize data addition or subtraction calculation in one beat, thus doubling the data processing speed of the entire TDC module, that is, the entire The chip data throughput is doubled; since the statistical histogram is no longer used to calculate the depth value, but the chip directly outputs the depth data (timebin value), the data output volume of the chip, as well as the post-level calculation amount of the statistical histogram ( For example, matched filtering + peak-finding algorithm, etc.) will be significantly reduced, which can improve the processing efficiency of the chip.

Further, the number of N can be specifically set to 2-30.

Furthermore, in the embodiment of the present application, by increasing the number of N or reducing the adjustment difference, the accuracy of the object distance measurement value 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 can be set to a high point in advance, so that the average value of the historical values of the N first data is closer to the actual object distance. Measurement value, or the adjustment difference can be reduced, so that the first data converges with higher accuracy and a more accurate object can be obtained Distance measurement.

In the embodiment of the present application, there is a first storage space and an adjustment difference value. The first storage space is used to store a piece of data. The adjustment difference value can be used to perform convergent adjustment and update on the data in the first storage space, so that the third The first data in a storage space is closer to the actual object distance measurement value; specifically, when the laser exposure starts, the data output by the TDC in real time is compared with the first data in the first storage space, and according to the comparison result, the first data is The addition and subtraction adjustment difference values are stored in the first storage space as updated data. The first data is preset with an initial value until the exposure is completed and the comparison step is stopped. Through each TDC real-time output data and the first storage space For comparison, the data output by TDC conforms to the characteristics of Poisson distribution, and the first data is continuously updated and adjusted through each numerical comparison, so that the first data quickly converges to the actual value through numerical comparison at the initial value. near the object distance measurement value; finally, determine the object distance measurement value based on the value of the first data. When the data output by the TDC in real time and the first data in the first storage space are compared a sufficient number of times, the finally obtained first data will be compared with the actual The object distance measurement value has a small error and is basically equivalent to the actual object distance measurement value. When using this laser ranging method, there is no need to save statistical histogram data inside the ranging chip, SRAM can be reduced or not used to save data, and the area of the ranging chip is significantly reduced.

It should be understood that the sequence number of each step in the above embodiment does not mean 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 embodiment of the present application.

An embodiment of the present application provides a laser ranging device. The laser ranging device includes:

Laser transmitter, used to emit laser;

SPAD array, used to receive optical signals;

An up/down counter, used to store the addition and subtraction adjustment difference of the first data as updated data in the first storage space according to the comparison result, where the adjustment difference is preset;

Further, the laser ranging device also includes:

a second storage space and a computing unit, wherein the second storage space has a greater storage capacity than the first storage space;

The plus/minus counter is also used to save the plus/minus adjustment difference of the first data as updated data in the first storage space and at the same time 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;

The calculation unit is used to calculate the average of the historical values of the N first data;

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

In the embodiment of the present application, there is a first storage space and an adjustment difference value. The first storage space is used to store a piece of data. The adjustment difference value can be used to perform convergent adjustment and update on the data in the first storage space, so that the third The first data in a storage space is closer to the actual object distance measurement value; specifically, when the laser exposure starts, the data output by the TDC in real time is compared with the first data in the first storage space, and according to the comparison result, the first data is The addition and subtraction adjustment difference values are stored in the first storage space as updated data. The first data is preset with an initial value until the exposure is completed and the comparison step is stopped. Through each TDC real-time output data and the first storage space The first data within the comparison can be utilized The data output by TDC conforms to the characteristics of Poisson distribution. The first data is continuously updated and adjusted through each numerical comparison, so that the first data quickly converges to the actual object distance measurement value through numerical comparison at the initial value; finally, according to the The value of a data determines the object distance measurement value. When the data output by the TDC in real time and the first data in the first storage space are compared enough times, the error between the finally obtained first data and the actual object distance measurement value is small, basically Equivalent to actual object distance measurement. When using this laser ranging method, there is no need to save statistical histogram data inside the ranging chip, SRAM can be reduced or not used to save data, and the area of the ranging chip is significantly reduced.

Furthermore, in the embodiment of the present application, a second storage space can be expanded based on the first storage space. The second storage space can store the latest N historical values of the first data, that is, the second storage space stores The value of is the first data updated after the last N comparisons. In the embodiment of the present application, according to the average value of the historical values of N first data, the average value can be rounded to determine the object distance measurement value. In this way, compared with steps S10-S30, the last first data is used to determine The object distance measurement value is more error-tolerant, making the object distance measurement value closer to the actual object distance measurement value.

Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above functional units and modules is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs. Module completion means dividing the internal structure of the device into different functional units or modules to complete all or part of the functions described above.

The above embodiments are only used to illustrate the technical solutions of the present application, but are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments. Modifications are made to the recorded technical solutions, or equivalent substitutions are made to some of the technical features; these 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 shall be included in this application. within the scope of protection.

Claims

A laser ranging method, characterized by including:

A first storage space is provided, and an adjustment difference value is provided, and the first storage space is used to store a piece of data;

When the laser exposure starts, the real-time output data of the TDC is compared with the first data in the first storage space. According to the comparison result, the first data plus or minus the adjustment difference is saved as updated data in the first storage space. In the first storage space, the first data is preset with an initial value, and the comparison step is stopped until the exposure is completed;

Based on the value of said first data, an object distance measurement is determined.
The method of claim 1, further comprising:

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 plus or minus the adjustment difference is saved in the first storage space as updated data, and is simultaneously saved in the second storage space. When the exposure ends, the storage capacity of the second storage space N historical values of the first data are stored, 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 object distance measurement value is determined based on the average of the N historical values of the first data.
The method of claim 2, wherein the first storage space is part of the second storage space, the second storage space is a shift register capable of storing N pieces of data, and the first storage space is a shift register capable of storing N pieces of data. A storage space occupies the first position or the last position of the second storage space.
The method according to claim 1, characterized in that the data output by the TDC in real time is compared with the first data in the first storage space, and the first data is added or subtracted according to the comparison result. The adjusted difference value is saved in the first storage space as updated data, including:

Compare the data output by the TDC in real time 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 updated data, which is stored in the first storage space;

If the first data is greater than the data output by the TDC in real time, the adjusted difference is subtracted from the first data to obtain the updated data, which is stored in the first storage space;

If the first data is equal to the data output by the TDC in real time, the first data is still stored in the first storage space.
The method of claim 1, wherein the initial value preset by the first data is an intermediate value of the measurement range of the TDC.
The method of claim 1, wherein the adjustment difference includes a first adjustment difference and a second adjustment difference, and the first adjustment difference is greater than the second adjustment difference. , the adjustment difference value is changed according to the number of times of TDC reception, wherein when the number of comparisons reaches a preset threshold, the first adjustment difference value is changed to the second adjustment difference value.
The method according to claim 2, characterized in that by increasing the number of N or reducing the adjustment difference, the accuracy of the object distance measurement value is improved.
The method according to any one of claims 1 to 7, characterized in that the number of N ranges from 2 to 30, and the adjustment difference ranges from 0.5 to 10.
A laser ranging device, characterized by including:

Laser transmitter, used to emit laser;

SPAD array, used to receive optical signals;

TDC array, used to convert the flight time value of the optical signal into a digital signal;

A comparator, used to compare the real-time output data of one of the TDCs with the first data in the first storage space;

An up/down counter, used to save the first data addition and subtraction adjustment difference as updated data in the first storage space according to the comparison result, wherein the adjustment difference is preset;

The first storage space is used to save the first data, and the first data is preset with an initial value;

A processing circuit configured to determine an object distance measurement value based on the first data.
The device according to claim 9, further comprising 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 and subtract the adjustment difference to the first data and save it in the first storage space as updated data, and simultaneously save it in the second storage space. At the end, 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 an average of N historical values of the first data;

The processing circuit is also configured to determine the object distance measurement value based on the average of the N historical values of the first data.