CN115469320A - Laser ranging method, device and medium - Google Patents
Laser ranging method, device and medium Download PDFInfo
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Abstract
The application discloses a method, a device and a medium for laser ranging, and relates to the field of optics. The method comprises the following steps: acquiring first calibration data within an acquisition duration under the condition that a target object does not exist; acquiring actual data within the acquisition duration under the condition that a target object exists; acquiring a first difference value between actual data in each acquisition period and corresponding first calibration data, and taking the first difference value as data after the first calibration data is calibrated; and determining the distance between the time-of-flight module and the target object according to the data after the first calibration. In the method, the actual data is used for subtracting the calibration data, so that the number of the photons at the near end is smaller than the number of the photons returned by the single photon avalanche diode when the target object is detected, the phenomenon that the number of the detected photons is higher than the number of the photons returned by the target object due to near-end crosstalk, the misjudgment caused during distance calculation is avoided as much as possible, and the accuracy of laser ranging is improved.
Description
Technical Field
The present application relates to the field of optics, and in particular, to a method, an apparatus, and a medium for laser ranging.
Background
In order to measure a distance of a distant object or an object located in a complex environment, a laser is generally used to measure the distance of the object. For example, a Time-of-flight module is formed by a Vertical Cavity Surface Emitting Laser (VCSEL), a Single Photon Avalanche Diode (SPAD), and a Time-to-Digital Converter (TDC).
In the process of range finding, VCSEL transmits laser pulse, and the SPAD receives the pulse of following the object reflection, and TDC record SPAD receives the time difference of photon and VCSEL transmission laser, considers the time that the photon quantity that the SPAD received is the most as the time of flight between module to object, and then calculates the distance between module and object according to velocity of light and time of flight. Due to the reasons of near-end crosstalk (including module internal light ring crosstalk and module external light environment crosstalk) and the like, the number of near-end photons is large, and when a peak formed by the near-end crosstalk is higher than a peak formed by photons reflected back by an object, if the peak with the largest number of photons is simply used for calculating the distance, an incorrect distance can be obtained, so that the measured distance of the object is inaccurate.
Therefore, how to improve the accuracy of laser ranging is a technical problem that needs to be solved urgently by those skilled in the art.
Disclosure of Invention
The application aims to provide a laser ranging method, a laser ranging device and a laser ranging medium, which are used for correcting laser ranging errors so as to improve the accuracy of laser ranging.
In order to solve the above technical problem, the present application provides a method for laser ranging, including:
starting a laser emitter to emit laser pulses, and acquiring first calibration data in an acquisition time length; the first calibration data is the number of photons acquired by the single photon avalanche diode in each acquisition period in the acquisition duration under the condition that no target object exists; the acquisition period is less than the acquisition duration;
acquiring actual data in the acquisition time length from the beginning of transmitting laser pulses by the laser transmitter; wherein the actual data is the number of photons acquired by the single photon avalanche diode in each acquisition cycle within the acquisition duration in the presence of the target object;
acquiring a first difference value between the actual data in each acquisition period and the corresponding first calibration data, and taking the first difference value as calibrated data;
and determining the distance between the time-of-flight module and the target object according to the calibrated data.
Preferably, the acquiring the first calibration data within the acquisition duration comprises:
acquiring the first calibration data within a preset time length from the beginning of the laser transmitter transmitting laser pulses; the preset duration is smaller than the acquisition duration, and the acquisition period is smaller than the preset duration.
Preferably, the actual data includes first actual data in the preset duration and second actual data in a remaining duration, and the remaining duration is a duration in the acquisition duration except for the preset duration; the determining the distance between the time-of-flight module and the target object according to the calibrated data comprises:
acquiring a second difference value between the first actual data in each acquisition period and the corresponding first calibration data, and taking the second difference value as first calibrated data in the preset time length;
selecting a first time corresponding to the maximum photon number from the first calibrated data and the second actual data;
acquiring a first product result of the light speed and the first moment;
taking half of the first multiplication result as the distance between the time-of-flight module and the target object.
Preferably, the preset time length is determined according to a distance between the single photon avalanche diode and a lens through which the laser pulse passes, and the preset time length is in positive correlation with a distance between the single photon avalanche diode and the lens.
Preferably, after the acquiring actual data within the acquisition duration, the method further comprises:
determining a second moment corresponding to the maximum photon number according to the actual data;
judging whether the second moment is within the remaining duration or not;
if yes, obtaining a first ratio of the first actual data in each acquisition period to the corresponding first calibration data;
obtaining products of the first ratios and the corresponding first calibration data, and taking the products as second calibration data;
acquiring a third difference value between the first actual data in each acquisition period and the corresponding second calibration data, and taking the third difference value as second calibrated data in the preset time length;
selecting a third time corresponding to the maximum number of photons from the second calibrated data and the second actual data;
under the condition that the second time and the third time are the same, acquiring a second product result of the light speed and the second time or the third time;
taking half of the second product result as the distance between the time-of-flight module and the target object.
Preferably, after determining that the second time is within the remaining time period, before the obtaining the first ratio of the first actual data and the corresponding first calibration data in each of the acquisition periods, the method further includes:
obtaining a first maximum number of photons from the first actual data and a second maximum number of photons from the first calibration data;
obtaining a second ratio of the first maximum number of photons to the second maximum number of photons;
if the second ratio is greater than or equal to a threshold value, the step of obtaining the first ratio of the first actual data and the corresponding first calibration data in each acquisition period is performed.
Preferably, the method further comprises:
and under the condition that the laser transmitter emits laser pulses to touch the target object, outputting prompt information for representing the touch of the target object and/or recording the corresponding moment of the touch of the target object.
In order to solve the above technical problem, the present application further provides a device for laser ranging, including:
the first acquisition module is used for acquiring first calibration data in an acquisition time length when the laser transmitter transmits laser pulses; the first calibration data is the number of photons acquired by the single photon avalanche diode in each acquisition period in the acquisition duration under the condition that no target object exists; the acquisition period is less than the acquisition duration;
the second acquisition module is used for acquiring actual data in the acquisition time length from the beginning of transmitting the laser pulse by the laser transmitter; wherein the actual data is the number of photons acquired by the single photon avalanche diode in each acquisition cycle within the acquisition duration in the presence of the target object;
a third obtaining module, configured to obtain a first difference between the actual data in each acquisition period and the corresponding first calibration data, and use the first difference as calibrated data;
and the determining module is used for determining the distance between the time-of-flight module and the target object according to the calibrated data.
In order to solve the above technical problem, the present application further provides a device for laser ranging, including:
a memory for storing a computer program;
a processor for implementing the steps of the above-described laser ranging method when executing the computer program.
In order to solve the above technical problem, the present application further provides a computer-readable storage medium, on which a computer program is stored, and the computer program, when executed by a processor, implements the steps of the above method for laser ranging.
The laser ranging method provided by the application comprises the following steps: starting to emit laser pulses by a self-excited light emitter, and acquiring first calibration data in an acquisition duration; the first calibration data is the number of photons acquired by the single photon avalanche diode in each acquisition period in the acquisition duration under the condition that the target object does not exist; the acquisition period is less than the acquisition duration; starting to emit laser pulses by a self-excited light emitter, and acquiring actual data in an acquisition duration; the actual data is the number of photons acquired by the single photon avalanche diode in each period in the acquisition time length under the condition that the target object exists; acquiring a first difference value between actual data in each acquisition period and corresponding first calibration data, and taking the first difference value as calibrated data; and determining the distance between the time-of-flight module and the target object according to the calibrated data. In the method, the actual data is used for subtracting the calibration data, so that the number of the photons at the near end is smaller than the number of the photons returned by the single photon avalanche diode when the target object is detected, the phenomenon that the number of the detected photons is higher than the number of the photons returned by the target object due to near-end crosstalk, the misjudgment caused during distance calculation is avoided as much as possible, and the accuracy of laser ranging is improved.
In addition, the application also provides a laser ranging device and a computer readable storage medium, which have the same or corresponding technical characteristics with the above mentioned laser ranging method, and the effects are the same as the above.
Drawings
In order to more clearly illustrate the embodiments of the present application, the drawings needed for the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained by those skilled in the art without inventive effort.
Fig. 1 is a schematic diagram of a time-of-flight module ranging provided in an embodiment of the present application;
fig. 2 is a dtod direct measurement time-of-flight histogram when the near-end crosstalk noise intensity is smaller than the signal intensity of the object to be measured according to the embodiment of the present application;
fig. 3 is a dtod direct measurement time-of-flight histogram when the near-end crosstalk noise strength exceeds the signal strength of the object to be measured according to the embodiment of the present application;
fig. 4 is a flowchart of a method for laser ranging according to an embodiment of the present disclosure;
FIG. 5 is a histogram of corrected dToF direct measured time-of-flight in accordance with an embodiment of the present application;
fig. 6 is a structural diagram of a laser distance measuring device according to an embodiment of the present application;
fig. 7 is a structural diagram of a laser ranging apparatus according to another embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without any creative effort belong to the protection scope of the present application.
The core of the application is to provide a method, a device and a medium for laser ranging, which are used for correcting laser ranging errors, so that the accuracy of laser ranging is improved.
In order to measure a distance of a distant object or an object located in a complex environment, a laser is generally used to measure the distance of the object. Fig. 1 is a schematic diagram of time-of-flight module ranging provided in an embodiment of the present application. The distance between the time-of-flight module and the object 6 is measured during the distance measurement. The time-of-flight module specifically comprises a laser emitter 1, a single photon avalanche diode 2, a time-to-digital converter 3, a lens 4 and a baffle 5. The SPAD can generate a current signal only by receiving a photon.
The principle of using time-of-flight module ranging is as follows:
1. the VCSEL emits a laser pulse and the SPAD receives the pulse reflected from the object.
2. The TDC is capable of recording the time difference between the receipt of photons by the SPAD and the emission of laser light by the VCSEL.
3. Fig. 2 is a diagram illustrating a direct measurement time-of-flight histogram of dtofs when the intensity of the near-end crosstalk noise is smaller than the signal intensity of the object to be measured according to the number of photons received by the SPAD in different time periods. As shown in fig. 2, the number of photons received by SPAD is counted every 1ps from the time when VCSEL emits light, and plotted as a histogram.
4. Most of the photons emitted by the VCSELs return when hitting the detected object, so the time period t when the number of received photons in the histogram is the largest is considered as the flight time of the photons between the module and the object.
5. Calculating the distance d between the module and the object according to the light speed c as formula (1):
d＝c*t/2 (1)
6. in the ranging process, the number of near-end photons is large due to near-end crosstalk and the like.
7. The number of photons at the far end will be small due to the loss of photons in the propagation process (VCSEL- > object- > SPAD).
8. Fig. 3 is a dtod direct-measure time-of-flight histogram when the near-end crosstalk noise strength exceeds the signal strength of the object to be measured according to an embodiment of the present disclosure. As shown in fig. 3, the peak at 1ps is a large number of photons generated by near end crosstalk detected by SPAD; the peak at 150ps is the amount of photons returned by the SPAD detected from the object being measured. When the peak formed by the near-end crosstalk is higher than the peak formed by the photons reflected back from the object, if the distance is calculated by simply using the peak with the largest number of Counts, an erroneous distance is obtained:
8.1 when t =1ps, d = c t/2=3 × 108 (m/s) × 1 × 10-12 (s)/2 =0.15mm (error).
8.2 when t =150ps, d = c t/2=3 × 108 (m/s) × 150 × 10-12 (s)/2 =22.5mm (correct).
In practice, there are many reasons for the generation of the near-end crosstalk, and the noise may come from the noise generated by the crosstalk inside the module, and when the lens is installed outside the module, the lens reflects light to a certain extent, so that the photons reflected by the lens and the crosstalk inside the module are superimposed to form noise. One of the key technical problems of the time-of-flight ranging apparatus is how to determine the time-of-flight of light. The currently common method is to record the time of detecting photons by the SPAD through the TDC, wherein the time of receiving the largest number of photons is considered as the flight time t of light between the module and the object to be measured, and when the flight time t of light between the module and the object to be measured is confirmed, the distance between the module and the object to be measured can be calculated by using the formula (1). As described above, when the number of crosstalk photons received by the SPAD is the largest in the presence of near-end crosstalk, the obtained time t is not the flight time of light between the module and the object to be measured, and the calculated distance is also wrong, which results in a decrease in accuracy in laser ranging.
Therefore, in order to improve the accuracy of ranging, the laser ranging error needs to be calibrated. According to the method, laser ranging is calibrated before leaving a factory, and the number of photons at the near end is smaller than that of photons returned by an SPAD when the SPAD detects a target object by subtracting calibration data from actual data, so that correct flight time is obtained, and accurate distance between a module and the object is obtained according to the flight time; in addition, the calibration data may not completely and effectively cancel noise such as near-end crosstalk due to different factors such as the intensity of the environment in actual use and the intensity of the environment calibrated in factory, so that the ranging is calibrated again in actual use besides calibrating the ranging before factory shipment, and the accuracy of ranging is further improved.
In order that those skilled in the art will better understand the disclosure, the following detailed description will be given with reference to the accompanying drawings. Fig. 4 is a flowchart of a method for laser ranging according to an embodiment of the present application, and as shown in fig. 4, the method includes:
s10: starting from VCSEL (vertical cavity surface emitting laser) pulse emission, acquiring first calibration data in an acquisition time length; wherein the first calibration data is the number of photons acquired by the SPAD in each acquisition period within the acquisition duration in the absence of the target object; the acquisition period is less than the acquisition duration.
Since the range error caused by the near-end crosstalk is reduced as much as possible, the number of photons collected needs to be obtained from the beginning of emitting laser pulses from the VCSEL to the end of SPAD reception. Calibration data is first acquired. Calibrating the distance measuring device before delivery, calibrating when the assembly of the module, the lens and other components is finished, and referring calibration data obtained after delivery calibration as first calibration data. The first calibration data describes the number of photons acquired by the SPAD in each acquisition cycle, and the value of each acquisition cycle is not limited, and preferably each acquisition cycle has the same duration. In order to obtain the first calibration data mode, the module is directed to an open area, no target object exists (an object needing distance measurement is the target object), the number of returned photons is ensured to be not the photons returned by the target object as much as possible, and the number of photons obtained in each acquisition period due to near-end crosstalk is obtained. In this embodiment, first calibration data within an acquisition duration is obtained from the beginning of emission of a laser pulse by a VCSEL. The value of the acquisition duration is not limited, and the maximum value of the acquisition duration is usually determined according to the performance of the module. In order to be able to measure the distance to the target object, it is at least ensured that the laser pulse can hit the target object and the module can receive the photons returning after hitting the target object.
S11: acquiring actual data in an acquisition time length from the beginning of emitting laser pulses by the VCSEL; wherein the actual data is the number of photons acquired by the SPAD at each acquisition period within the acquisition duration in the presence of the target object.
First calibration data is obtained in the above steps. In order to calibrate the actual data, the actual data must be acquired. The actual data is the number of photons acquired by the SPAD in each acquisition cycle in the presence of the target object, and likewise, the values of each acquisition cycle are not limited, and preferably each acquisition cycle has the same duration. In order to make the process of calibrating the actual data according to the first calibration data faster and more convenient, each acquisition cycle when the actual data is acquired is selected to be the same as each acquisition cycle when the first calibration data is acquired.
S12: and acquiring a first difference value between the actual data and the first calibration data in each acquisition period, and taking the first difference value as calibrated data.
S13: and determining the distance between the time-of-flight module and the target object according to the calibrated data.
After the first calibration data and the actual data are acquired, a first difference value between the actual data of each acquisition period and the first calibration data is acquired respectively, and the first difference value is calibrated data acquired by calibrating the actual data according to the first calibration data. When the distance between the time-of-flight module and the target object is determined according to the calibrated data, the time corresponding to the maximum number of photons in the calibrated data is selected and is used as the time of flight, so that the distance between the time-of-flight module and the target object is calculated according to the formula (1), the laser ranging error correction is completed, and the accurate laser ranging result is obtained.
The laser ranging method provided by the embodiment includes: acquiring first calibration data within an acquisition duration from the beginning of emitting laser pulses by a VCSEL (vertical cavity surface emitting laser); wherein the first calibration data is the number of photons acquired by the SPAD in each acquisition period within the acquisition duration in the absence of the target object; the acquisition period is less than the acquisition duration; acquiring actual data in an acquisition time length from the beginning of emitting laser pulses by the VCSEL; the actual data is the number of photons acquired by the SPAD in each period in the acquisition time length under the condition that the target object exists; acquiring a first difference value between actual data in each acquisition period and corresponding first calibration data, and taking the first difference value as calibrated data; and determining the distance between the time-of-flight module and the target object according to the calibrated data. In the method, the actual data is used for subtracting the calibration data, so that the number of the photons at the near end is smaller than that of the photons returned by the SPAD when the target object is detected, the phenomenon that the number of the detected photons is higher than that of the photons returned by the target object due to near-end crosstalk is avoided as much as possible, the misjudgment caused during distance calculation is avoided, and the accuracy of laser ranging is improved.
In practice, since the number of photons at the far end is gradually reduced in the propagation process of the photons, and the number of photons caused by the near-end crosstalk is higher than the number of photons returned by the target object, in order to obtain the first calibration data more quickly, it is preferable that the obtaining the first calibration data in the acquisition time period includes:
the method comprises the steps that first calibration data within a preset time length are obtained from the beginning of emitting laser pulses by a VCSEL; the preset time is shorter than the acquisition time, and the acquisition period is shorter than the preset time.
The preset time length is determined according to the distance between the SPAD and the lens through which the laser pulse passes, and the preset time length is in positive correlation with the distance from the SPAD to the lens. The value of the preset duration is not limited, and the preset duration does not need to be set to be large, for example, the preset duration is set to be the duration of five times of the photon back and forth between the SPAD and the lens.
The self-emission laser pulse provided by the embodiment starts, only the number of photons within a preset time length is acquired as first calibration data, and since the number of photons at a far end is gradually reduced in the propagation process of the photons, the self-emission laser pulse has no great significance if the number of photons exceeding the preset time length is acquired; in addition, compared with the number of photons for acquiring the whole acquisition time, the preset time is shorter than the acquisition time, so that the number of photons for acquiring the preset time is faster, the calculated amount can be reduced when the difference value between the actual data and the first calibration data is acquired, and the efficiency of ranging calibration is improved.
On the basis of acquiring the number of photons in the preset time length as the first calibration data in the above embodiment, in order to perform distance measurement on the target object, a preferred embodiment is that the actual data includes first actual data in the preset time length and second actual data in a remaining time length, and the remaining time length is a time length in the acquisition time length except for the preset time length; determining the distance between the time-of-flight module and the target object based on the calibrated data comprises:
acquiring a second difference value between the first actual data in each acquisition period and the corresponding first calibration data, and taking the second difference value as first calibrated data in a preset time length;
selecting a first time corresponding to the maximum photon number from the first calibrated data and the second actual data;
obtaining a first product result of the light speed and a first moment;
and taking half of the first product result as the distance between the time-of-flight module and the target object.
The preset time length is 100ps, the ranging error caused by the near-end crosstalk in fig. 3 is corrected, the acquisition period in fig. 3 is 1ps, and the acquisition time length is 400ps. The specific correction process is as follows:
1. calibrating the distance measuring device before leaving factory, and calibrating when the assembly of the module, the lens and other components is finished
2. A calibration step:
2.1, the module is directed to the open area (no object to be measured at this time).
2.2, 100ps of data before recording, a total of 100 data, here denoted by C1 to C100.
2.3, C1 to C100 are recorded in a Read Only Memory (ROM) as first calibration data (which may be understood as factory calibration data).
And 2.4, after leaving the factory, reading the calibration data from the ROM when the distance measuring device is used for measuring the distance.
2.5, first actual data X1.. X100 of the first 100ps acquired in actual use minus the first calibration data C1.. C100 yields first calibrated data Y within 100ps, i.e. Y = X-C, and then the distance is calculated using the Y data.
2.6, the Y data (within 100 ps) and the X data within 100ps to 400ps are pieced together, the distance is calculated, and a histogram of the pieced data is shown in fig. 5, where fig. 5 is a corrected histogram of dtofs directly measured time-of-flight according to an embodiment of the present invention.
2.7, the purpose of subtracting the first calibration data is: the maximum value of Y is far smaller than the wave peak value of the measured object.
2.8, if some values of Y are reduced to negative numbers, processing when the value is 0;
3. with reference to fig. 5, after calibration, the first 100ps signal is significantly attenuated, and the distance is calculated using the peak with the largest count (t =150 ps), so that a correct distance is obtained:
when t =150ps, d = c × t/2=3 × 108 (m/s) × 150 × 10-12 (s)/2 =22.5mm.
According to the first calibration data with preset time length before leaving the factory, the calibration of actual data is achieved, and the accuracy of laser ranging is improved.
In the above, the laser ranging is calibrated before leaving a factory, but factors such as the light intensity of the environment in the use environment and the environment calibrated after leaving the factory are different in actual use, the first calibration data obtained in the above cannot completely and effectively cancel noise such as near-end crosstalk, and the reflection rate of the lens is changed due to the possible existence of fingerprints, oil stains and the like on the lens, and the original first calibration data is not applicable. Therefore, in order to solve the interference factors such as different environmental lights (including oil stains), the first calibration data needs to be calibrated again in actual use. In performing the recalibration, it is a preferred embodiment that after acquiring the actual data within the acquisition time period, the method of laser ranging further comprises:
determining a second moment corresponding to the maximum photon number according to the actual data;
judging whether the second moment is within the remaining duration;
if yes, acquiring a first ratio of the first actual data in each acquisition period to the corresponding first calibration data;
obtaining products of the first ratios and the corresponding first calibration data, and taking the products as second calibration data;
acquiring a third difference value between the first actual data and the corresponding second calibration data in each acquisition period, and taking the third difference value as second calibrated data in a preset time length;
selecting a third moment corresponding to the maximum photon number from the second calibrated data and the second actual data;
under the condition that the second time and the third time are the same, acquiring a second product result of the light speed and the second time or the third time;
and taking half of the second product result as the distance between the time-of-flight module and the target object.
When the ambient light is particularly strong or the structure is slightly changed due to collision of the modules, crosstalk signals are enhanced, actual data X may be very large and cannot be predicted when leaving a factory, so that calibration parameters need to be automatically adjusted. Specifically, a second moment corresponding to the maximum number of photons is determined according to actual data; if the second time is within the remaining time, the measured object is far away from the distance measuring device, and the photons collected within the preset time are considered to be noise instead of the photons returned by the measured object, wherein the photons are generated by interference factors such as near-end crosstalk, a glass lens, oil stains, ambient light and the like. When the peak appears outside 100ps as in fig. 5, it is considered that photons collected within 100ps are returned not by the measured object but by noise, and the second calibration data W1 to W100 are calculated.
The process of calculating the first ratio R is shown in equation (2):
Ri＝Xi/Ci (2)
the process of calculating the second calibration data W from the first ratio R is shown in equation (3):
Wi＝Ci*Ri (3)
calculating second calibrated data Y' according to the second calibration data W with preset time length and the first actual data, wherein the calculation process is shown as a formula (4):
Yi’＝Xi-Wi (4)
taking the preset time length as 100ps as an example, calculating R1 to R100 through a formula (2), calculating second calibration data W1 to W100 through a formula (3), and calculating Y1 'to Y100' through a formula (4); and selecting a third time corresponding to the time with the maximum photon number from Y1 'to Y100' and X101 to X400, substituting the second time or the third time into the formula (1) to calculate the distance between the flight time module and the target object under the condition that the third time and the previous second time are the same, and finishing laser ranging error correction to obtain a more accurate laser ranging result.
In the method provided by this embodiment, on the basis of calibration before delivery, calibration is performed again in actual use, so that the influence of ambient light (including oil stains) and the like on the ranging accuracy is reduced as much as possible.
In the foregoing embodiment, the first calibration data in the preset duration is calibrated again, and in practice, in order to improve the efficiency of laser ranging, a preferred embodiment is that after determining that the second time is within the remaining duration, before acquiring the first ratio between the first actual data and the corresponding first calibration data in each acquisition period, the method for laser ranging further includes:
obtaining a first maximum number of photons from the first actual data and a second maximum number of photons from the first calibration data;
obtaining a second ratio of the first maximum number of photons to the second maximum number of photons;
and if the second ratio is greater than or equal to the threshold, the step of obtaining the first ratio of the first actual data and the corresponding first calibration data in each acquisition period is carried out.
In the first actual data X1 to X100, the maximum number of Counts N1 is recorded, the maximum value in the first calibration data C1 to C100 is taken as N2, and when the ratio of N1 to N2 is greater than or equal to the threshold, it indicates that there is a large difference between the environment during use and the calibrated light environment before factory shipment, so the first calibration data needs to be calibrated again to obtain the second calibration data. Typically, the threshold is selected to be 1.2, i.e., the second ratio is greater than or equal to 1.2.
In this embodiment, the second calibration is performed only when the second ratio is greater than or equal to the threshold, and compared with a manner of directly performing the second calibration during use, if the difference between the light environment during use and the calibrated light environment before factory shipment is not large, it indicates that the first calibration data can be used, and if the first calibration data is calibrated again, the efficiency of ranging is reduced.
In implementation, in order to facilitate the user to know whether the emitted laser pulse hits the target object and to facilitate finding the flight time, the preferred embodiment is that the laser ranging method further includes:
when the VCSEL emits laser pulses to hit the target object, prompt information for representing the hitting of the target object is output and/or the corresponding time when the target object is hit is recorded.
The manner of the prompt message, the content of the prompt message, and the like are not limited as long as the user can be prompted that the emitted laser pulse hits the target object. Except that output prompt message, can also record the moment that the record was met the target object, can estimate the distance between time of flight module and the target object according to the moment of actual record, can compare the distance of estimating with the distance that calculates through this application to the accuracy of this application range finding of analysis.
In the above embodiments, the method of laser ranging is described in detail, and the present application also provides embodiments corresponding to the device of laser ranging. It should be noted that the present application describes the embodiments of the apparatus portion from two perspectives, one from the perspective of the function module and the other from the perspective of the hardware.
Fig. 6 is a structural diagram of a laser distance measuring device according to an embodiment of the present application. The present embodiment is based on the angle of the function module, including:
the device comprises a first acquisition module 10, a second acquisition module and a third acquisition module, wherein the first acquisition module is used for acquiring first calibration data in an acquisition time length from the beginning of emitting laser pulses by a VCSEL; wherein the first calibration data is the number of photons acquired by the SPAD in each acquisition period within the acquisition duration in the absence of the target object; the acquisition period is less than the acquisition duration;
the second acquisition module 11 is configured to acquire actual data within an acquisition duration from the beginning of emitting laser pulses by the VCSEL; the actual data is the number of photons acquired by the SPAD in each acquisition period in the acquisition duration under the condition that the target object exists;
a third obtaining module 12, configured to obtain a first difference between actual data in each acquisition period and corresponding first calibration data, and use the first difference as calibrated data;
and the determining module 13 is configured to determine a distance between the time-of-flight module and the target object according to the calibrated data.
Since the embodiments of the apparatus portion and the method portion correspond to each other, please refer to the description of the embodiments of the method portion for the embodiments of the apparatus portion, which is not repeated here.
In the laser ranging device provided in this embodiment, first calibration data within an acquisition duration is acquired by a first acquisition module from the beginning of emitting a laser pulse by a VCSEL; wherein the first calibration data is the number of photons acquired by the SPAD in each acquisition period within the acquisition duration in the absence of the target object; the acquisition period is less than the acquisition duration; acquiring actual data within the acquisition duration from the beginning of emitting laser pulses by the VCSEL through a second acquisition module; the actual data is the number of photons acquired by the SPAD in each acquisition period in the acquisition time length under the condition that the target object exists; acquiring a first difference value between actual data in each acquisition period and corresponding first calibration data through a third acquisition module, and taking the first difference value as calibrated data; and determining the distance between the time-of-flight module and the target object through the determining module according to the calibrated data. In the device, the calibration data is subtracted from the actual data, so that the number of the near-end photons is smaller than that of the photons returned by the SPAD when the target object is detected, the phenomenon that the number of the detected photons is higher than that of the photons returned by the target object due to near-end crosstalk is avoided as much as possible, the condition of misjudgment caused when distance calculation is carried out is further avoided, and the accuracy of laser ranging is improved.
Fig. 7 is a structural diagram of a laser ranging apparatus according to another embodiment of the present application. In this embodiment, based on the hardware angle, as shown in fig. 7, the laser ranging apparatus includes:
a memory 20 for storing a computer program;
a processor 21 for implementing the steps of the method for laser ranging as mentioned in the above embodiments when executing the computer program.
The laser ranging device provided in this embodiment may include, but is not limited to, a smart phone, a tablet computer, a notebook computer, or a desktop computer.
The processor 21 may include one or more processing cores, such as a 4-core processor, an 8-core processor, and the like. The Processor 21 may be implemented in hardware using at least one of a Digital Signal Processor (DSP), a Field-Programmable Gate Array (FPGA), and a Programmable Logic Array (PLA). The processor 21 may also include a main processor and a coprocessor, where the main processor is a processor for Processing data in a wake state, and is also called a Central Processing Unit (CPU); a coprocessor is a low power processor for processing data in a standby state. In some embodiments, the processor 21 may be integrated with a Graphics Processing Unit (GPU) which is responsible for rendering and drawing the content required to be displayed by the display screen. In some embodiments, the processor 21 may further include an Artificial Intelligence (AI) processor for processing computing operations related to machine learning.
In some embodiments, the laser ranging device may further include a display 22, an input/output interface 23, a communication interface 24, a power supply 25, and a communication bus 26.
Those skilled in the art will appreciate that the configuration shown in fig. 7 does not constitute a limitation of the means for laser ranging and may include more or fewer components than those shown.
The laser ranging device provided by the embodiment of the application comprises a memory and a processor, wherein when the processor executes a program stored in the memory, the following method can be realized: the effect of the laser ranging method is the same as that of the laser ranging method.
Finally, the application also provides a corresponding embodiment of the computer readable storage medium. The computer-readable storage medium has stored thereon a computer program which, when being executed by a processor, carries out the steps as set forth in the above-mentioned method embodiments.
It is to be understood that if the method in the above embodiments is implemented in the form of software functional units and sold or used as a stand-alone product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application may be embodied in the form of a software product, which is stored in a storage medium and executes all or part of the steps of the methods described in the embodiments of the present application, or all or part of the technical solutions. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The computer-readable storage medium provided by the present application includes the above-mentioned laser ranging method, and the effects are the same as above.
The method, the device and the medium for laser ranging provided by the present application are described in detail above. The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description. It should be noted that, for those skilled in the art, without departing from the principle of the present application, the present application can also make several improvements and modifications, and those improvements and modifications also fall into the protection scope of the claims of the present application.
It should also be noted that, in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. A method of laser ranging, comprising:
starting a laser emitter to emit laser pulses, and acquiring first calibration data in an acquisition time length; the first calibration data is the number of photons acquired by the single photon avalanche diode in each acquisition period in the acquisition time length under the condition that a target object does not exist; the acquisition period is less than the acquisition duration;
acquiring actual data within the acquisition duration from the beginning of the laser emitter emitting laser pulses; wherein the actual data is the number of photons acquired by the single photon avalanche diode in each acquisition cycle within the acquisition duration in the presence of the target object;
acquiring a first difference value between the actual data in each acquisition period and the corresponding first calibration data, and taking the first difference value as calibrated data;
and determining the distance between the time-of-flight module and the target object according to the calibrated data.
2. The method of claim 1, wherein said obtaining first calibration data over an acquisition duration comprises:
acquiring the first calibration data within a preset time length from the beginning of the laser transmitter transmitting laser pulses; the preset duration is less than the acquisition duration, and the acquisition period is less than the preset duration.
3. The laser ranging method according to claim 2, wherein the actual data comprises first actual data within the preset duration and second actual data within a remaining duration, and the remaining duration is a duration within the acquisition duration except for the preset duration; the determining the distance between the time-of-flight module and the target object according to the calibrated data comprises:
acquiring a second difference value between the first actual data in each acquisition period and the corresponding first calibration data, and taking the second difference value as first calibrated data in the preset time length;
selecting a first moment corresponding to the maximum photon quantity from the first calibrated data and the second actual data;
acquiring a first product result of the light speed and the first moment;
taking half of the first multiplication result as the distance between the time-of-flight module and the target object.
4. The laser ranging method of claim 3, wherein the preset time duration is determined according to a distance between the single photon avalanche diode and a lens through which the laser pulse passes, and the preset time duration is positively correlated with the distance from the single photon avalanche diode to the lens.
5. The method of laser ranging according to claim 4, wherein after said acquiring actual data over the acquisition time period, the method further comprises:
determining a second moment corresponding to the maximum photon number according to the actual data;
judging whether the second moment is within the remaining duration;
if yes, acquiring a first ratio of the first actual data and the corresponding first calibration data in each acquisition period;
obtaining products of the first ratios and the corresponding first calibration data, and taking the products as second calibration data;
acquiring a third difference value between the first actual data and the corresponding second calibration data in each acquisition period, and taking the third difference value as second calibrated data in the preset time length;
selecting a third time corresponding to the maximum number of photons from the second calibrated data and the second actual data;
under the condition that the second time and the third time are the same, acquiring a second product result of the light speed and the second time or the third time;
taking half of the second product result as the distance between the time-of-flight module and the target object.
6. The laser ranging method according to claim 5, wherein after determining that the second time is within the remaining time period, before the obtaining the first ratio of the first actual data and the corresponding first calibration data in each of the acquisition periods, the method further comprises:
obtaining a first maximum number of photons from the first actual data and a second maximum number of photons from the first calibration data;
obtaining a second ratio of the first maximum number of photons to the second maximum number of photons;
if the second ratio is greater than or equal to a threshold value, the step of obtaining the first ratio of the first actual data and the corresponding first calibration data in each acquisition period is performed.
7. The laser ranging method of any one of claims 1 to 6, further comprising:
and under the condition that the laser transmitter emits laser pulses to touch the target object, outputting prompt information for representing the touch of the target object and/or recording the corresponding moment of the touch of the target object.
8. A laser ranging apparatus, comprising:
the first acquisition module is used for acquiring first calibration data in an acquisition time length when the laser transmitter transmits laser pulses; the first calibration data is the number of photons acquired by the single photon avalanche diode in each acquisition period in the acquisition duration under the condition that no target object exists; the acquisition period is less than the acquisition duration;
the second acquisition module is used for acquiring actual data in the acquisition time length from the beginning of transmitting the laser pulse by the laser transmitter; wherein the actual data is the number of photons acquired by the single photon avalanche diode in each acquisition cycle within the acquisition duration in the presence of the target object;
a third obtaining module, configured to obtain a first difference between the actual data in each acquisition period and the corresponding first calibration data, and use the first difference as calibrated data;
and the determining module is used for determining the distance between the time-of-flight module and the target object according to the calibrated data.
9. A laser ranging apparatus, comprising:
a memory for storing a computer program;
a processor for implementing the steps of the method of laser ranging as claimed in any one of claims 1 to 7 when executing the computer program.
10. A computer-readable storage medium, characterized in that a computer program is stored thereon, which computer program, when being executed by a processor, carries out the steps of the method of laser ranging according to any one of claims 1 to 7.
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