Method for improving tof resolution and laser ranging system

Abstract

The application provides a method for improving TOF resolution and a laser ranging system, and the method comprises the following steps: acquiring a plurality of preset delay times; sequentially inserting the plurality of preset delay times on a laser signal emission link; recording the time of a photon detection event after delay; comparing the time of the photon detection event after delay with a preset histogram; and analyzing the photon flight time according to a comparison result. By inserting a fine configurable delay in the laser signal link, comparing the time of the photon detection event after delay with the preset histogram, and calculating an accurate distance value lower than one quantization interval according to the inserted delay data, the quantization error is reduced, and the ranging precision is improved to the millimeter level.

Description

Technical Field

[0001] This invention relates to the field of laser ranging technology, and more specifically to a method for improving TOF resolution and a laser ranging system. Background Technology

[0002] In laser ranging systems based on photon event detection, a series of laser pulses are typically emitted, and the photon detection times are recorded at the receiving end for dozens or hundreds of times. The photon detection times are then used to generate a corresponding histogram based on the time series, and the peak value of the histogram is the corresponding time of flight (TOF).

[0003] Histogram grouping (BIN) quantizes the time of photon detection events into a finite number of histogram intervals, leading to quantization errors. This limited number of histograms reduces ranging resolution; for example, a 100ps quantization interval results in a resolution of 15mm. Increasing the number of histogram bins can improve distance resolution, but this requires increasing the hardware operating frequency, which is extremely difficult in practical designs. Therefore, there is currently no good solution on the market to improve Time-of-Flight (TOF) resolution. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the deficiency in the prior art that there is currently no good solution on the market to improve the resolution of TOF, thereby providing a method and laser ranging system for improving the resolution of TOF.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a method for improving TOF resolution, applied to a laser ranging system. The method for improving TOF resolution includes: acquiring multiple preset delay times; sequentially inserting multiple preset delay times into a laser signal transmission link; recording the delayed photon detection event time; comparing the delayed photon detection event time with a preset histogram; and analyzing the photon flight time based on the comparison results.

[0007] Optionally, obtaining multiple preset delay times includes: obtaining the preset histogram grouping interval time; dividing the grouping interval into multiple parts; and determining multiple preset delay times based on each part.

[0008] Optionally, the step of sequentially inserting multiple preset delay times into the laser signal transmission link includes: sorting the multiple preset delay times according to their delay duration; and sequentially inserting the multiple preset delay times into the laser signal transmission link according to the sorting result.

[0009] Secondly, embodiments of the present invention provide a laser ranging system, comprising: a TOF module, a microcontroller unit, and a laser signal transmission link, wherein...

[0010] The first end of the TOF module is connected to the first end of the laser signal transmission link, and the second end of the TOF module is connected to the first end of the microcontroller unit. The TOF module is used to generate a laser signal according to the instructions issued by the microcontroller unit and send the laser signal to the laser signal transmission link. The laser signal transmission link emits a series of lasers that hit the obstacle.

[0011] The second end of the microcontroller is connected to the second end of the laser signal transmission link. The microcontroller is used to acquire multiple preset delay times and sequentially insert multiple preset delay times into the laser signal transmission link.

[0012] The TOF module is also used to record the delayed photon detection event time, compare the delayed photon detection event time with a preset histogram, analyze the photon flight time based on the comparison results, and calculate the distance value based on the photon flight time.

[0013] Optionally, the laser signal transmission link includes a delay circuit and a laser driving circuit, wherein the first end of the delay circuit is connected to the first end of the TOF module, the second end of the delay circuit is connected to the second end of the microcontroller unit, and the third end of the delay circuit is connected to the laser driving circuit.

[0014] The technical solution of this invention has the following advantages:

[0015] This invention provides a method for improving Time-of-Flight (TOF) resolution, comprising: acquiring multiple preset delay times; sequentially inserting multiple preset delay times into a laser signal transmission link; recording the delayed photon detection event time; comparing the delayed photon detection event time with a preset histogram; and analyzing the photon time of flight based on the comparison results. By inserting finely configurable delays into the laser signal link, comparing the delayed photon detection event time with the preset histogram, and calculating a precise distance value below one quantization interval based on the inserted delay data, the quantization error is reduced, and the ranging accuracy is improved to the millimeter level.

[0016] The present invention provides a laser ranging system that, by inserting a finely configurable delay into the laser signal link, calculates an accurate distance value below a quantization interval based on the inserted delay data, thereby reducing quantization error and improving ranging accuracy to the millimeter level. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 Histogram grouping is a specific example in an embodiment of the present invention;

[0019] Figure 2 This is a principle block diagram of a specific example of a laser ranging system in an embodiment of the present invention;

[0020] Figure 3 A flowchart illustrating a specific example of a method for improving TOF resolution in an embodiment of the present invention;

[0021] Figure 4 This is a histogram grouping for another specific example in an embodiment of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] In laser ranging, based on histogram grouping, the photon detection event time is quantized into discrete histogram intervals, such as... Figure 1 The time series shown are 100, 101, and 102. Assuming a grouping interval of 100 ps, ​​all measurements with flight times between 100 and 101 will be grouped to time 100, thus introducing a quantization error of 100 ps. To improve the ranging accuracy of Direct Time-of-Flight (DToF) systems and mitigate the quantization error caused by traditional histogram-based binning, this invention provides a method for improving TOF resolution, applicable to systems such as... Figure 2 The laser ranging system shown.

[0027] like Figure 2 As shown, the microcontroller unit (MCU) communicates and interacts with the TOF module. The MCU configures the TOF module parameters and reads the ranging values ​​collected by the TOF module. During ranging, the TOF module generates a laser signal based on the parameters issued by the MCU and sends the laser signal to the laser signal transmission link. Simultaneously, the MCU inserts multiple preset delay times into the laser signal transmission link. After each preset delay, the laser signal transmission link emits a series of lasers that hit the obstacle. These lasers return to the TOF module, which collects and analyzes the data. The time of photon detection after the delay is compared with a preset histogram. Based on the comparison results, the photon flight time is analyzed, and the distance value is calculated based on the photon flight time.

[0028] Based on the working principle of the laser ranging system described above, such as Figure 3 As shown, the method to improve TOF resolution includes the following steps:

[0029] Step S1: Obtain multiple preset delay times.

[0030] In one specific embodiment, multiple preset delay times are obtained in the following manner:

[0031] Step S11: Obtain the preset histogram grouping interval time.

[0032] Step S12: Divide the grouping interval into multiple parts.

[0033] Step S13: Determine multiple preset delay times for each share.

[0034] In this embodiment of the invention, a preset histogram grouping interval time is obtained, and one grouping interval time is taken as a unit time. This unit time is then divided into several equal or unequal delays. For example... Figure 4 As shown, taking a delay divided into four equal parts as an example, if the interval between histogram groupings is 100ps (each equal interval is 25ps), then T0 has a delay of 0ps, T1 has a delay of 25ps, T2 has a delay of 50ps, and T3 has a delay of 75ps. If the delay is divided into four unequal parts, then the first unequal interval is 10ps, the second unequal interval is 20ps, the third unequal interval is 30ps, and the fourth unequal interval is 40ps, meaning T0 has a delay of 0ps, T1 has a delay of 10ps, T2 has a delay of 30ps, and T3 has a delay of 60ps.

[0035] Step S2: Insert multiple preset delay times sequentially into the laser signal transmission link.

[0036] In one specific embodiment, multiple preset delay times are sequentially inserted into the laser signal transmission link, including the following steps:

[0037] Step S21: Sort the multiple preset delay times according to their delay duration;

[0038] Step S22: Insert multiple preset delay times into the laser signal transmission link in sequence according to the sorting results.

[0039] In embodiments of the present invention, such as Figure 4 As shown, taking a four-part delay as an example, the delay times are ordered by duration as T0 delay, T1 delay, T2 delay, and T3 delay. These delays are then sequentially inserted into the laser signal transmission link. After being delayed by T0, T1, T2, and T3 respectively, the laser signal transmission link emits a series of laser beams that hit the obstacle. Inserting any unequal delays into the laser signal transmission link follows the same procedure as with the four-part delay, and will not be detailed here.

[0040] Step S3: Record the delayed photon detection event time, compare the delayed photon detection event time with the preset histogram, and analyze the photon flight time based on the comparison results.

[0041] In one specific embodiment, such as Figure 4As shown, taking a four-part delay as an example, without any delay processing (delay time T0 = 0 ps), the TOF module measures a flight time between 100 and 101. The position of the solid four-pointed star in the diagram, without any other processing, is categorized as position 100 in the time series. If the delay times are configured sequentially as T1, T2, and T3, the flight time measured by the TOF module will be shifted. However, due to the existence of histogram grouping, the measured times for delays T1 and T2 are still categorized as position 100. With a delay of T3, the distance will span 100 ps and will be categorized as part of the 101 series. From the above process, we can see that when the delay is T0, T1, or T2, the time series measured by TOF is 100, and when the delay is T3, the time series measured is 101. Therefore, we can deduce that the actual flight time is between 1 / 4 and 2 / 4 of the distance between 100 and 101, i.e., between 100 plus 25 ps and 50 ps. Thus, the original quantization error of 100 ps is reduced to a quantization error of 25 ps. It can be inferred that regardless of the actual flight time, repeating the above process, i.e., delaying by T0, T1, T2, and T3 respectively, can reduce the quantization error from 100 ps to 25 ps. It can be concluded that setting the delay time as n equal parts of a grouping interval interval can obtain a time resolution of 1 / n grouping interval time intervals.

[0042] This invention provides a method for improving Time-of-Flight (TOF) resolution, comprising: acquiring multiple preset delay times; sequentially inserting multiple preset delay times into a laser signal transmission link; recording the delayed photon detection event time; comparing the delayed photon detection event time with a preset histogram; and analyzing the photon time of flight based on the comparison results. By inserting finely configurable delays into the laser signal link, comparing the delayed photon detection event time with the preset histogram, and calculating a precise distance value below one quantization interval based on the inserted delay data, the quantization error is reduced, and the ranging accuracy is improved to the millimeter level.

[0043] In one embodiment, to reduce the number of searches and improve search efficiency, a binary search method is preferred. That is, a unit of time is divided into two equal parts, with each grouping interval time being considered a unit of time. If the histogram grouping interval time is 100 ps, ​​then each equal interval is 50 ps, ​​with T0 delayed by 0 ps and T1 delayed by 50 ps. Specifically, during the ranging process, T0 is delayed first, then T1. If the photon detection event time has not changed from 100 to 101, the actual flight time is determined to be between 0 and 1 / 2 of the interval between 100 and 101. If the photon detection event time changes from 100 to 101, the actual flight time is determined to be between 1 / 2 and 1 of the interval between 100 and 101. Therefore, the original quantization error of 100 ps is reduced to a quantization error of 50 ps. By using the binary search method, both resolution is improved and the number of searches is reduced.

[0044] This invention also provides a laser ranging system, such as... Figure 2 As shown, it includes: a TOF module, a microcontroller unit, and a laser signal transmission link, wherein,

[0045] The first end of the TOF module is connected to the first end of the laser signal transmission link, and the second end of the TOF module is connected to the first end of the microcontroller unit. The TOF module is used to generate laser signals according to the instructions issued by the microcontroller unit and send the laser signals to the laser signal transmission link. The laser signal transmission link emits a series of lasers that hit the obstacle.

[0046] The second end of the microcontroller is connected to the second end of the laser signal transmission link. The microcontroller is used to acquire multiple preset delay times and insert multiple preset delay times into the laser signal transmission link in sequence.

[0047] The TOF module is also used to record the delayed photon detection event time, compare the delayed photon detection event time with a preset histogram, analyze the photon flight time based on the comparison results, and calculate the distance value based on the photon flight time.

[0048] In one specific embodiment, such as Figure 2 As shown, the laser signal transmission link includes a delay circuit and a laser driving circuit. The delay circuit can be located at any node on the laser signal link, such as inside the TOF module, after the laser driving circuit, or in the link where the laser returns from an obstacle to the TOF module. In this embodiment of the invention, only the following example is used... Figure 2 The settings shown are for illustrative purposes only and are not exhaustive. For example... Figure 2 As shown, the first end of the delay circuit is connected to the first end of the TOF module, the second end of the delay circuit is connected to the second end of the microcontroller unit, and the third end of the delay circuit is connected to the laser drive circuit.

[0049] Specifically, the microcontroller unit communicates and interacts with the TOF module. The microcontroller unit configures the TOF module parameters and reads the ranging values ​​acquired by the TOF module. During ranging, the TOF module generates a laser signal based on the parameters sent by the microcontroller unit and sends the laser signal to the delay circuit. Simultaneously, the microcontroller unit sets multiple preset delay times on the delay circuit. Under the action of the delay circuit, the laser drive circuit emits a series of lasers after each of the preset delay times, hitting the obstacle. The series of lasers returns to the TOF module, which collects and statistically analyzes the photon detection event times after the delays, comparing them with a preset histogram. Based on the comparison results, the photon flight time is analyzed, and the distance value is calculated based on the photon flight time.

[0050] Furthermore, the microcontroller acquires the preset histogram grouping interval time, taking one grouping interval time as a unit of time, and divides this unit of time into several equal or unequal delays, thereby setting the delay time of the delay circuit. For example... Figure 4 As shown, taking a four-part delay as an example, if the interval between histogram groupings is 100ps (each equal interval is 25ps), then T0 has a delay of 0ps, T1 a delay of 25ps, T2 a delay of 50ps, and T3 a delay of 75ps. Based on these delay settings, the microcontroller controls the delay circuit, setting the delay time. Under the action of the delay circuit, the laser drive circuit sequentially delays T0, T1, T2, and T3 before emitting a series of laser beams that hit the obstacle.

[0051] like Figure 4 As shown, without any delay processing (T0 = 0 ps), the TOF module measures a flight time between 100 and 101 ps. The position of the solid-lined four-pointed star in the diagram, without any other processing, is categorized as time series position 100. When the delay times are configured sequentially as T1, T2, and T3, the flight time measured by the TOF module will be shifted. However, due to the existence of histogram grouping, the measured time is still categorized as 100 ps when the delay is T1 and T2. When the delay is T3, the distance will cross a 100 ps cycle and be categorized as 101 ps. From the above process, we can conclude that when the delay is T0, T1, or T2, the TOF measures a time series of 100 ps, ​​and when the delay is T3, the time series is 101 ps. Therefore, the actual flight time is between 1 / 4 and 2 / 4 of the distance between 100 and 101 ps, that is, between 100 plus 25 ps and 50 ps. Therefore, the original quantization error of 100ps was reduced to 25ps. It can be deduced that regardless of the actual flight time, repeating the above process, i.e., delaying by T0, T1, T2, and T3 respectively, can reduce the quantization error from 100ps to 25ps.

[0052] The present invention provides a laser ranging system that, by inserting a finely configurable delay into the laser signal link, calculates an accurate distance value below a quantization interval based on the inserted delay data, thereby reducing quantization error and improving ranging accuracy to the millimeter level.

[0053] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for improving TOF resolution, characterized in that, When applied to laser ranging systems, the method for improving TOF resolution includes: Get multiple preset delay times; Multiple preset delay times are sequentially inserted into the laser signal transmission link; The delayed photon detection event time is recorded, and the delayed photon detection event time is compared with a preset histogram. The photon flight time is analyzed based on the comparison results. The comparison of the delayed photon detection event time with the preset histogram includes: comparing the interval number of the photon detection event time in the preset histogram under different delay conditions, and determining the offset of the photon flight time in a single interval based on the delay time when the interval number changes. The process of obtaining multiple preset delay times includes: Obtain the preset histogram grouping interval time; The grouping interval is divided into multiple parts; Multiple preset delay times are determined for each share.

2. The method for improving TOF resolution according to claim 1, characterized in that, The step of sequentially inserting multiple preset delay times into the laser signal transmission link includes: Sort the multiple preset delay times according to their delay duration; Based on the sorting results, multiple preset delay times are sequentially inserted into the laser signal transmission link.

3. A laser ranging system, characterized in that, include: The TOF module, microcontroller unit, and laser signal transmission link are included. The first end of the TOF module is connected to the first end of the laser signal transmission link, and the second end of the TOF module is connected to the first end of the microcontroller unit. The TOF module is used to generate a laser signal according to the instructions issued by the microcontroller unit and send the laser signal to the laser signal transmission link. The laser signal transmission link emits a series of lasers that hit the obstacle. The second end of the microcontroller is connected to the second end of the laser signal transmission link. The microcontroller is used to acquire multiple preset delay times and sequentially insert the multiple preset delay times into the laser signal transmission link. Acquiring the multiple preset delay times includes: acquiring a preset histogram grouping interval time; dividing the grouping interval into multiple parts; and determining multiple preset delay times according to each part. The TOF module is also used to record the delayed photon detection event time, compare the delayed photon detection event time with a preset histogram, analyze the photon flight time based on the comparison results, and calculate the distance value based on the photon flight time. The comparison of the delayed photon detection event time with the preset histogram includes: comparing the interval number of the photon detection event time in the preset histogram under different delay conditions, and determining the offset of the photon flight time in a single interval based on the delay time when the interval number changes.

4. The laser ranging system according to claim 3, characterized in that, The laser signal transmission link includes: a delay circuit and a laser driving circuit, wherein... The first end of the delay circuit is connected to the first end of the TOF module, the second end of the delay circuit is connected to the second end of the microcontroller unit, and the third end of the delay circuit is connected to the laser driving circuit.

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