CN114690195B - A distance measurement method, system and computer readable storage medium - Google Patents
A distance measurement method, system and computer readable storage medium Download PDFInfo
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
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- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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Abstract
本申请适用于飞行时间技术领域，提供一种距离测量系统、方法及计算机可读存储介质。本申请实施例通过控制发射器向待测物发射n种频率的脉冲光束；控制采集器采集待测物反射的n种频率的脉冲光束中的光子并输出多个光子信号；根据多个光子信号计算得到与n种频率一一对应的n个初始飞行时间，根据所述n种频率构建虚拟频率，并结合所述n个初始飞行时间计算测量飞行时间；其中，所述n为大于或等于2的整数。有效提高了测距精度，降低随机误差的产生；并且可以提升测距范围，可以计算出位于最大测距范围之外的待测物的飞行时间。
The present application is applicable to the field of flight time technology, and provides a distance measurement system, method and computer-readable storage medium. The embodiment of the present application controls the transmitter to transmit a pulse beam of n frequencies to the object to be measured; controls the collector to collect photons in the pulse beam of n frequencies reflected by the object to be measured and outputs multiple photon signals; calculates n initial flight times corresponding to the n frequencies one by one according to the multiple photon signals, constructs a virtual frequency according to the n frequencies, and calculates the measured flight time in combination with the n initial flight times; wherein n is an integer greater than or equal to 2. The ranging accuracy is effectively improved, and the generation of random errors is reduced; and the ranging range can be increased, and the flight time of the object to be measured outside the maximum ranging range can be calculated.
Description
Technical Field
The application relates to the technical field of Time of flight (TOF), in particular to a distance measuring method and device.
Background
The distance of the object to be measured can be measured by using the time-of-flight technology, and a depth image containing the depth value of the object to be measured can be further acquired based on the distance of the object to be measured. Distance measurement systems based on time-of-flight technology have been widely used in the fields of consumer electronics, unmanned vehicles, virtual reality, augmented reality, etc. Distance measuring systems generally include a transmitter and a collector, the transmitter transmitting a pulsed light beam to illuminate an object to be measured and the collector receiving a pulsed light beam reflected by the object to be measured, and the distance between the object to be measured and the distance measuring system is calculated by calculating the time the pulsed light beam is transmitted to be received.
The distance measuring method for transmitting the multi-frequency pulse light beam is widely adopted at present, although the distance measuring method increases the distance measuring range compared with the distance measuring method for transmitting the single-frequency pulse light beam, random errors are easy to generate when the multi-frequency pulse light beam is acquired by the collector, calculation errors are easy to be caused by the conditions of algorithm selection errors and the like even if corresponding algorithms are designed for different error conditions, and in addition, when an object to be measured is located outside the maximum distance measuring range, interference is caused when the collector still acquires the reflected pulse light beam, so that the distance measuring errors are large.
Disclosure of Invention
In view of the above, the embodiment of the application provides a profile processing control method, terminal equipment and storage medium, so as to solve the problem of poor stability of a profile processing production line.
A first aspect of an embodiment of the present application provides a distance measurement method, including:
Controlling the transmitter to transmit pulse light beams with n frequencies to an object to be measured;
the control collector collects photons in the n frequency pulse beams reflected by the object to be detected and outputs a plurality of photon signals;
calculating n initial flight times corresponding to the n frequencies one by one according to the photon signals;
constructing virtual frequencies according to the n frequencies, and calculating and measuring flight time by combining the n initial flight time;
wherein n is an integer greater than or equal to 2.
A second aspect of an embodiment of the present application provides a distance measurement system, including a transmitter, a collector, and a processing circuit connected to the transmitter and the collector;
The emitter is used for emitting pulse light beams with n frequencies to an object to be detected;
The collector is used for collecting photons in the n frequency pulse beams reflected by the object to be detected and outputting a plurality of photon signals;
The processing circuit is configured to execute the steps of the distance measurement method provided in the first aspect of the embodiment of the present application.
A third aspect of the embodiments of the present application provides a computer readable storage medium storing a computer program which, when executed by a processor, implements the steps of the distance measurement method provided by the first aspect of the embodiments of the present application.
According to the distance measurement method provided by the first aspect of the embodiment of the application, the emitter is controlled to emit n kinds of frequency pulse light beams to the object to be measured, the collector is controlled to collect photons in the n kinds of frequency pulse light beams reflected by the object to be measured and output a plurality of photon signals, n initial flight times corresponding to the n kinds of frequencies one by one are calculated according to the plurality of photon signals, the measurement flight time is calculated according to the n kinds of frequencies and the n initial flight times, the distance measurement precision is effectively improved, the random error is reduced, the distance measurement range is improved, and the flight time of the object to be measured which is located outside the maximum distance measurement range can be calculated.
It will be appreciated that the advantages of the second and third aspects may be found in the relevant description of the first aspect and are not described in detail herein.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced 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 according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a distance measurement system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a first flow of a distance measurement method according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a second flow chart of a distance measurement method according to an embodiment of the present application;
FIG. 4 is a schematic diagram of a third flow chart of a distance measurement method according to an embodiment of the present application;
fig. 5 is a fourth flowchart of a distance measurement method according to an embodiment of the present application.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
It should be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It should also be understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
Furthermore, the terms "first," "second," "third," and the like in the description of the present specification and in the appended claims, are used for distinguishing between descriptions and not necessarily for indicating or implying a relative importance.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.
The embodiment of the application provides a distance measurement method, which can be applied to terminal equipment such as mobile phones, tablet computers, wearable equipment, notebook computers, ultra-mobile personal computer (UMPC), netbooks, personal Digital Assistants (PDA) and the like which comprise processing circuits, and can be executed when a computer program with corresponding functions is run by the processing circuits of the terminal equipment, so as to control a transmitter, a collector and the like to realize the distance measurement function.
As shown in fig. 1, an embodiment of the present application provides a distance measurement system 100, including a transmitter 1, a collector 2, and a processing circuit 3 connected to the transmitter 1 and the collector 2;
a transmitter 1 for transmitting a pulse beam 300 of n frequencies to an object 200 to be measured;
a collector 2 for collecting photons in the n-frequency pulse beams 300 reflected by the object 200 and outputting a plurality of photon signals;
The processing circuit 3 is used for calculating n initial flight times corresponding to the n frequencies one by one according to the photon signals, calculating measured flight times according to the n frequencies and the n initial flight times, and calculating calibration flight times according to the n frequencies, the n initial flight times corresponding to the n frequencies one by one and the measured flight times, wherein n is an integer greater than or equal to 2.
In application, the object to be measured may be any object in free space. At least part of the n frequency pulse light beams emitted by the emitter to the object to be detected are reflected back to the collector by the object to be detected, the collector performs photoelectric conversion on the n frequency pulse light beams reflected by the collected object to be detected to obtain a plurality of corresponding photon signals, and then the photon signals are output to the processing circuit. The processing circuit calculates n initial flight times corresponding to n frequencies one by one according to a plurality of photon signals output by the collector, then calculates measurement flight times according to the n frequencies and the n initial flight times, and can calculate the distance between the object to be measured and the distance measurement system based on the measurement flight times. The processing circuit is used for synchronously sending a trigger signal to the emitter and the collector so as to synchronously trigger the emitter to emit a pulse beam and the collector to collect a plurality of light spots formed on the surface of the pixel unit after the pulse beam reflected by the object to be detected is diffracted by the grating. The trigger signal may be a clock signal.
In an application, the transmitter comprises a light source unit comprising at least one light source, each light source being operable to emit a pulsed light beam of at least one frequency. The light source may be a light emitting Diode (LIGHT EMITTING Diode, LED), a Laser Diode (LD), an edge emitting Laser (EDGE EMITTING LASER, EEL), a vertical cavity surface emitting Laser (VerticalCavitySurfaceEmitting Laser, VCSEL), or the like. The number of the light sources included in the light source unit can be set according to actual needs, and the light source unit can be a one-dimensional or two-dimensional light source array consisting of at least two light sources. The light source array can be a vertical cavity surface emitting laser array chip formed by generating a plurality of vertical cavity surface emitting lasers on a single semiconductor substrate, and the arrangement mode of the light sources in the light source array can be regular or irregular. The pulsed light beam emitted by the light source may be visible light, infrared light, ultraviolet light, etc.
In one embodiment, the transmitter further comprises a driver for controlling the light source unit to transmit pulse light beams of preset n frequencies, the preset n frequencies being set according to a ranging range of the distance measuring system, the driver being connected to the light source unit.
In application, the light source unit emits a pulsed light beam to an object under control of the driver. It will be appreciated that a portion of the processing circuitry or other circuitry present independently of the processing circuitry may also be used to control the light source unit to emit a pulsed light beam. The preset n frequencies are inversely related to the ranging range of the distance measuring system, and the preset pulse period is positively related to the ranging range of the distance measuring system.
In one embodiment, the emitter further includes an emitting optical element for optically modulating the pulse beam emitted by the light source unit and projecting the pulse beam onto the object to be measured.
In applications, the optical modulation may be diffraction, refraction, reflection, etc., and the modulated pulsed light beam may be a focused light beam, a flood light beam, a structured light beam, etc. The emission optical element may include at least one of a lens, a liquid crystal element, a diffraction optical element, a microlens array, a super surface (Metasurface) optical element, a mask, a mirror, a Micro-Electro-MECHANICAL SYSTEM, MEMS (Micro-Electro-MECHANICAL SYSTEM, MEMS) galvanometer, and the like.
Fig. 1 exemplarily shows that the emitter 1 includes a light source unit 11, an emitting optical element 12, and a driver 13, the light source unit 11 being connected to the driver 13.
In application, the collector comprises a pixel cell, which may be a pixel array composed of a plurality of photosensitive pixels, which may be one of avalanche photodiodes (AVALANCHE PHOTON DIODE, APD), single photon avalanche photodiodes (Single Photon Avalanche Diode, SPAD), silicon photomultiplier (multi-pixel photon counter, silicon photomultiplier, siPM), etc. for collecting photons. The single photon avalanche photodiode can respond to an incident single photon and output a signal indicative of the Time at which the photon arrived at the single photon avalanche photodiode, with collection of weak light signals and calculation of Time of flight using techniques such as Time-dependent single photon counting (Time-Correlated Single Photon Counting, TCSPC). In one embodiment, the collector further comprises a receiving optical element for focusing the pulsed light beam reflected by the object to be measured to the pixel unit.
In an embodiment, the receiving optical element further comprises a filtering unit for filtering out background light and stray light incident on all pixels. The filter unit may be a low pass filter.
The collector 2 is exemplarily shown in fig. 1 to comprise a pixel unit 21, a filter unit 22 and a receiving optical element 23. It should be understood that, in fig. 1, the filter unit 22 is disposed between the pixel unit 21 and the receiving optical element 23 for convenience of illustration, and is not used to limit the relative positions of the filter unit 22 and the receiving optical element 23 in practical applications.
In application, the processing circuit includes a time-to-digital converter (Time to Digital Converter, TDC) circuit, a histogram circuit, and a signal amplifier, an Analog-to-Digital Converter (ADC), and so on, which are connected to the pixel unit. These devices may be integrated with the pixel cell or may be part of the processing circuitry. The TDC circuit is used for calculating the initial flight time of the pulse light beam according to the receiving time of the received photon signal and the transmitting time of the pulse light beam transmitted by the transmitter to the target, converting the initial flight time into a time code for output, addressing the corresponding time bin (time interval) in the histogram circuit according to the time code, adding 1 to the photon count value in the time interval, counting to obtain a photon count statistical histogram after detecting a large number of repeated pulses, and determining the time corresponding to the peak position of the histogram as the measuring flight time, wherein the time code can be a temperature code or a binary code. The processing circuitry may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processors, system-on-a-chips (SOCs), digital signal processors (DIGITAL SIGNAL processors, DSPs), application Specific Integrated Circuits (ASICs), off-the-shelf Programmable gate arrays (Field-Programmable GATE ARRAY, FPGA) or other Programmable logic devices, discrete gate or transistor logic devices, discrete hardware arrays, or the like. The general purpose processor may be a microprocessor or any conventional processor or the like.
In one embodiment, the distance measurement system further comprises a memory for storing a pulse code program. The driver is connected with the storage for controlling the time, frequency, etc. of the light source unit emitting the pulse light beam by using the pulse coding program.
In one embodiment, the distance measurement system may further include at least one of an RGB camera, an infrared camera, and an inertial measurement unit (Inertialmeasurementunit, IMU) for implementing 3D texture modeling, infrared face recognition, time-positioning and mapping (simultaneous localization AND MAPPING, SLAM), and the like.
As shown in fig. 2, the distance measurement method provided by the embodiment of the present application includes the following steps S201 to S204 implemented by the processing circuit in the above embodiment:
Step S201, controlling a transmitter to transmit pulse beams with n frequencies to an object to be measured, wherein n is an integer greater than or equal to 2.
In application, the sizes of the n frequencies need to be close to each other to ensure the accuracy of distance measurement, and the larger the frequency of the pulse beam is, the higher the frequency of the pulse beam emitted by the emitter, the frequency of the pulse beam collected by the collector, the sensitivity and the distance measurement accuracy of the distance measurement system are, and the frequency of the pulse beam can be set according to actual needs. In one embodiment, the frequency of the pulsed light beam emitted by the emitter is sequentially f 1,f2,f3…fn, wherein the first frequency f 1 is the smallest in value and the next frequencies sequentially increase. In one embodiment, the control transmitter transmits 2 kinds of pulse beams with frequencies f 1 and f 2, respectively, to the object to be measured, and preferably, the pulse beams with the two frequencies can be selected to be transmitted alternately.
Step S202, controlling a collector to collect photons in n frequency pulse beams reflected by the object to be detected and outputting a plurality of photon signals.
In application, at least part of the n kinds of frequency pulse beams emitted by the emitter to the object to be detected are reflected back to the collector by the object to be detected, so that the collector can identify and collect the pulse beams with corresponding frequencies reflected by the object to be detected, perform photoelectric conversion to obtain corresponding photon signals, and then output the photon signals to the processing circuit. The processing circuit synchronously sends a trigger signal to the emitter and the collector so as to synchronously trigger the emitter to emit a pulse beam with corresponding frequency and the collector to collect the pulse beam reflected by the object to be detected. The trigger signal may be a clock signal, and the clock signal for triggering the transmitter to transmit the pulse beams of n frequencies to the object to be measured may be defined as a start clock signal.
Step S203, calculating n initial flight times corresponding to the n frequencies one by one according to the photon signals.
In application, the initial time of flight represents the time of flight of the pulsed light beam during the current period when the pulsed light beam is acquired by the acquisition unit. When the processing circuit controls the emitter to emit the pulse light beams with n frequencies to the object to be detected, the processing circuit calculates n initial flight times corresponding to the n frequencies one by one according to the photon signals, and can perform maximum peak searching according to the histogram to obtain n initial flight times, for example, n flight times corresponding to n peak values with the largest photon signals are obtained in the histogram to serve as the initial flight times.
And S204, constructing virtual frequencies according to the n frequencies, and calculating and measuring flight time by combining the n initial flight time.
In application, the maximum detection distance of the system can be extended by emitting pulsed light beams of n frequencies. Since there are some situations that the measured time of flight exceeds the cycle number corresponding to the frequency, assuming that the first frequency is the minimum frequency, the second frequency starts to gradually increase, when the time of flight of the object to be measured is greater than the cycle corresponding to the first frequency, the time of flight measured in the cycle corresponding to each frequency is different, we define the calculated time of flight at each frequency as the initial time of flight, and if the measured time of flight exceeds the cycle number corresponding to a certain frequency by m, the measured time of flight is actually the sum of m cycles corresponding to the frequency and the initial time of flight. In the present invention, the measured time of flight is calculated by constructing a new virtual frequency from the transmitted n frequencies, which is smaller than any one of the n frequencies such that the measured time of flight does not exceed the period corresponding to the virtual frequency, and combining the calculated initial time of flight.
Because the constructed virtual frequency is smaller, the sensitivity and the ranging accuracy of the distance measurement system are not high, and errors possibly exist in the calculated measurement flight time, the distance measurement method of the application further comprises the following steps:
Step S205, calculating calibration flight time according to the n frequencies, n initial flight times corresponding to the n frequencies one by one and the measured flight time.
In the application, the ith frequency, the ith initial flight time corresponding to the ith frequency and the measured flight time are selected, the cycle number m of the ith initial flight time is calculated, and then the sum of the time of the corresponding m complete cycles of the initial flight time and the initial flight time is calculated to be used as the calibration flight time t. It is understood that the ith frequency may be any of n frequencies.
Further, the distance between the distance measuring system and the object to be measured can be calculated according to the calibrated flight time, and the calculation formula is as follows:
Wherein D represents the distance between the object to be measured and the distance measuring system, c represents the speed of light, and t represents the calibrated flight time.
As shown in fig. 3, in one embodiment, step S204 includes the following steps S301 to S303:
And step 301, obtaining the phase of the ith initial flight time according to the ith frequency and the ith initial flight time corresponding to the ith frequency, wherein i=1, 2.
In one embodiment, the calculation formula for calculating the phase of the i-th initial time of flight in step S301 is:
Wherein, The phase representing the i-th initial flight time, f i representing the i-th frequency, and t i representing the i-th initial flight time corresponding to the i-th frequency.
In application, the triangular function characterizing the phase of the ith initial time of flight is:
sin(2πfiti);
cos(2πfiti);
since the measured time of flight satisfies the relationship The calculation formula for measuring the phase of the flight time corresponding to the ith frequency can be obtained as follows:
Wherein, Representing the phase of the measured time of flight, f i representing the i-th frequency,Representing the measured time of flight, m i represents the i-th cycle number, i.e. the measured time of flight exceeds the multiple of the cycle corresponding to the i-th frequency.
Further, from the formula (1), it can be obtained that the phase of the measured time of flight and the i-th initial time of flight satisfies the following relation:
In one embodiment, the transmitter is controlled to transmit 2 pulse beams with frequencies f 1 and f 2 to the object to be measured, where the initial flight times t 1 and t 2 are obtained correspondingly, and the calculation formula for calculating the phase of the initial flight time in step S301 is as follows:
Wherein, Indicating the phase corresponding to the 1 st initial time of flight t 1,The phase corresponding to the 2 nd initial time of flight t 2 is shown.
In application, the transmitter is controlled to transmit a pulse beam with the frequency f 1 to the object to be measured, and the initial flight time t 1 is correspondingly obtained, so that the phase of the measured flight time and the phase of the 1 st initial flight time satisfy the following relation:
And controlling the transmitter to transmit a pulse light beam with the frequency of f 2 to the object to be measured, correspondingly obtaining the initial flight time of t 2, and enabling the phase of the measured flight time and the phase of the 2 nd initial flight time to meet the following relation:
The derivation of the above relation and the above embodiment AndIs consistent with the derivation process of (c), and is not described in detail herein.
Step S302, a first virtual frequency is constructed by selecting two frequencies according to the n frequencies.
In one embodiment, the calculation formula for constructing the first virtual frequency according to the n frequencies in step S302 is:
f′k＝|fi-fj|,k=1,2,...,n(n-1)/2,j=1,2,...,n,i≠j;
f=min(f′k);
Where f 'k denotes an absolute value of a difference between the i-th frequency and the j-th frequency, f denotes a first virtual frequency, and min (f' k) denotes a minimum value of absolute values of differences between any two different frequencies among the n frequencies.
In application, the processing circuit may subtract n frequencies from each other to obtain a total of n (n-1)/2 absolute values of a difference between the ith frequency and the jth frequency, and obtain a minimum value of the n (n-1)/2 absolute values as the first virtual frequency.
In application, the ith frequency and the jth frequency of the n frequencies satisfy the relation:
wherein min (f i,fj) represents the minimum value of the i-th frequency and the j-th frequency, |f i-fj | represents the absolute value of the difference between the i-th frequency and the j-th frequency;
since the frequency of the pulse beam emitted by the emitter, the frequency of the pulse beam collected by the collector, the sensitivity and the distance measurement accuracy of the distance measurement system are higher, and the difference between the ith frequency and the jth frequency is smaller, the first virtual frequency constructed by the ith frequency and the jth frequency is smaller, the first virtual frequency is formed by the first virtual frequency Where f represents a first virtual frequency, D max represents a maximum ranging range of the distance measurement system, and it is possible to obtain that the smaller the first virtual frequency is, the larger the maximum ranging range of the distance measurement system is, and therefore, by the above-mentioned relation, the i-th frequency and the j-th frequency can be set to be sufficiently large, so that the maximum ranging range of the distance measurement system is increased. It should be noted that, the limitation that the absolute value of the difference between the ith frequency and the jth frequency is smaller than the fifth of the minimum value of the ith frequency and the jth frequency is merely exemplary, and may be limited to one third, one seventh, one tenth, etc. according to the actual needs, and the magnitude relation between the ith frequency and the jth frequency is not limited in any way in the embodiment of the present application.
For example, the transmitter is controlled to transmit 3 kinds of pulse beams with frequencies f 1、f2 and f 3 respectively to the object to be measured, the 1 st frequency is f 1 =50 Hz, the 2 nd frequency is f 2 =49 Hz, the 3 rd frequency is f 3 =47 Hz, and the calculation formula for constructing the first virtual frequency by selecting two kinds of frequencies according to n kinds of frequencies is as follows:
f′1＝|f1-f2|=1Hz;
f′2＝|f1-f3|=3Hz;
f′3＝|f2-f3|=2Hz;
and acquiring the minimum value f' 1 as a first virtual frequency. It should be noted that, the above calculation formula for constructing the first virtual frequency is only exemplary, and the embodiment of the application does not limit the construction manner of the first virtual frequency.
In one embodiment, the transmitter is controlled to emit a pulsed light beam having two frequencies f 1 and f 2 toward the target, for example, an alternate emission scheme may be employed. In step S302, the calculation formula for constructing the first virtual frequency according to the n frequencies is:
f=|f1-f2|;
where f 1 denotes the 1 st frequency, and f 2 denotes the 2 nd frequency.
In application, when the transmitter transmits a pulsed light beam with two frequencies to the object to be measured, the processing circuit may acquire the absolute value of the difference between the 1 st frequency and the 2 nd frequency as the first virtual frequency.
Step S303, calculating and measuring the flight time according to the first virtual frequency and the phase of the initial flight time corresponding to the two frequencies used for constructing the first virtual frequency.
In one embodiment, the calculation formula for calculating the measured time of flight in step S303 is:
assuming a first virtual frequency f=f i-fj, then
Wherein, A phase representing a first initial time of flight corresponding to a first frequency used to construct a first virtual frequency,Representing the phase of a second initial time of flight corresponding to another frequency used to construct the first virtual frequency.
In application, since the frequency value of the first virtual frequency is much smaller than that of the ith frequency, the period length of the pulse beam of the first virtual frequency is much longer than that of the pulse beam of the ith frequency, so that the pulse beam of each frequency can be emitted by the emitter, reflected by the object to be measured and collected by the collector within the period corresponding to the first virtual frequency, that is, the period number of the measurement flight time is 0, and the measurement flight time calculated by the calculation formula for calculating the measurement flight timeWherein, Indicating that the measured time of flight exceeds a multiple of the period corresponding to the first virtual frequency f, noted as the number of periods,Representing the initial flight time corresponding to the first virtual frequency, takingCan obtain the measured flight timeSince the trigonometric function has periodicity, the trigonometric function is calculated by the formula Can calculate two measurement flight times according to the calculation formula The application can overcome the periodicity of trigonometric function by combining the two calculation formulas to calculate the actual measurement flight time.
In one embodiment, the transmitter is controlled to transmit 2 pulse beams with frequencies f 1 and f 2 to the object to be measured, and initial flight times t 1 and t 2 are obtained correspondingly, and the calculation formula for calculating the measured flight time in step S303 is as follows:
Wherein, Indicating the phase corresponding to the 1 st initial time of flight t 1,The phase corresponding to the 2 nd initial time of flight t 2 is shown.
In application, when the transmitter is controlled to transmit 2 pulse beams with frequencies f 1 and f 2 to the object to be measured, the calculation process of the calculation formula for measuring the flight time is identical to that in the foregoing embodiment, and will not be described in detail herein.
In application, the frequency value of the first virtual frequency is far smaller than the frequency value of the ith frequency, so that the period length corresponding to the first virtual frequency is far longer than the period length corresponding to the ith frequency, the range of the pulse beam transmitting the first virtual frequency can be far longer than the range of the pulse beam of the ith frequency, and the problem of distance aliasing generated after the detected object is located outside the range corresponding to the minimum frequency is effectively solved.
As shown in fig. 4, in one embodiment, step S205 includes steps S401 to S402:
And S401, calculating an ith cycle number according to the ith frequency, the ith initial flight time corresponding to the ith frequency and the measured flight time, wherein the ith cycle number is a multiple of a cycle of which the measured flight time exceeds the ith frequency.
In one embodiment, the calculation formula for calculating the i-th cycle number in step S401 is:
Wherein m i represents the i-th cycle number, Representing measured time of flight, t i represents the i-th initial time of flight corresponding to the i-th frequency, and f i represents the i-th frequency.
In the application, since the frequency value of the first virtual frequency is far smaller than the frequency value of the ith frequency, the accuracy of the measured flight time corresponding to the first virtual frequency is not high, and the flight time of the object to be measured cannot be accurately calculated due to the possible error. Therefore, the number of cycles of the measured time of flight exceeding the period corresponding to the ith frequency is calculated according to the calculated measured time of flight and the initial time of flight of the ith frequency, the calculated number of cycles may be rounded off by rounding, and step S402 is further performed according to the number of cycles and the corresponding initial time of flight to calculate an accurate measured time of flight, i.e. a calibration time of flight. It will be appreciated that any one of the n frequencies and the initial time of flight corresponding to that frequency may be selected to calculate the number of cycles of the target time at the period corresponding to that frequency.
In one embodiment, the transmitter is controlled to transmit 2 pulse beams with frequencies f 1 and f 2 to the object to be measured, where the initial flight times t 1 and t 2 are obtained correspondingly, and the calculation formula for calculating the number of cycles of the ith initial flight time in step S401 is as follows:
Or alternatively, the first and second heat exchangers may be,
Wherein m 1 represents a multiple of the period corresponding to the measured time of flight exceeding the first frequency f 1, noted as a first period number,Representing the measured time of flight, m 2 representing the measured time of flight exceeding a multiple of the period corresponding to the second frequency f 2, noted as the second number of periods.
In application, the processing manner of the first cycle number and the second cycle number is identical to that of the foregoing embodiment, and will not be described herein. It will be appreciated that only one cycle number need be counted in the actual calculation process to calculate the calibrated time of flight for the corresponding frequency.
Step S402, calculating and obtaining a calibration flight time according to the ith frequency, the ith initial flight time corresponding to the ith frequency and the ith period number.
In one embodiment, the calculation formula of the calibration flight time calculated in step S402 is:
Where t represents a calibration time of flight, t i represents an i-th initial time of flight corresponding to an i-th frequency, round (m i) represents an i-th rounded number of cycles, and f i represents the i-th frequency.
In application, since the frequency value of the ith frequency is much larger than the first virtual frequency, the calculated accuracy of the calibrated time of flight is more accurate than the measured time of flight. It will be appreciated that the ith frequency used to calculate the calibration time of flight is any one of n frequencies, and is not necessarily the two frequencies that construct the first virtual frequency, and regardless of which frequency is selected, the exact time of flight of the object to be measured may be obtained.
In one embodiment, n=2, the calibrated time of flight calculated in step S402 may be calculated by selecting the time of flight corresponding to the frequency f 1 or the time of flight corresponding to the frequency f 2, where the specific calculation formula is as follows:
Or alternatively, the first and second heat exchangers may be,
Wherein round (m 1) represents the rounded first number of cycles and round (m 2) represents the rounded second number of cycles.
In application, since the frequency values of the 1 st frequency and the 2 nd frequency are much larger than the first virtual frequency, the calculated accuracy of the calibrated time of flight is more accurate than the measured time of flight.
In the application, according to the n kinds of frequencies transmitted by the transmitter, the ith frequency, the ith initial flight time corresponding to the ith frequency and the measured flight time, the cycle number of the measured flight time exceeding the cycle corresponding to the ith frequency is calculated, and the calibration flight time is further calculated by combining with the ith initial flight time, and since the frequency value of the ith frequency is far greater than the frequency value of the measured flight time, the more accurate calibration flight time than the measured flight time can be calculated, thereby improving the accuracy of distance measurement.
As shown in fig. 5, in another embodiment, steps S501 to S504 are included after step S303:
step S501, a second virtual frequency is constructed by selecting two frequencies according to the n frequencies.
In one embodiment, the calculation formula for constructing the second virtual frequency according to the n frequencies in step S501 is:
f′′k＝fi+fj,k=1,2,...,n(n-1)/2,j=1,2,...,n,i≠j;
f′=max(f′′k);
Wherein f ' k represents the sum of the ith frequency and the jth frequency, f ' represents the second virtual frequency, and max (f ' k) represents the maximum value of the sum of any two different frequencies of the n frequencies.
In application, the processing circuit can add n frequencies two by two to obtain a sum of n (n-1)/2 ith frequencies and jth frequencies, and obtain the maximum value of the sum as the second virtual frequency. Since the higher the frequency of the pulse light beam emitted by the emitter and the frequency of the pulse light beam collected by the collector, the higher the sensitivity and the ranging accuracy of the distance measuring system are, the sensitivity and the ranging accuracy of the distance measuring system can be increased by setting the second virtual frequency large enough.
For example, the transmitter is controlled to emit a pulsed light beam with three frequencies f 1、f2 and f 3 toward the target, the 1 st frequency has a size of f 1 =50 Hz, the 2 nd frequency has a size of f 2 =49 Hz, the 3 rd frequency has a size of f 3 =47 Hz, and the calculation formula for constructing the second virtual frequency according to the n frequencies is:
f′′1＝f1+f2=99Hz;
f′′2＝f1+f3=97Hz;
f′′3＝f2+f3=96Hz;
The maximum value f' 1 therein is acquired as the first virtual frequency. It should be noted that, the above calculation formula for constructing the second virtual frequency is only exemplary, and the embodiment of the application does not limit the construction manner of the second virtual frequency.
In one embodiment, the transmitter is controlled to emit a pulsed light beam having two frequencies f 1 and f 2 toward the target, for example, an alternate emission scheme may be employed. In step S501, the calculation formula for constructing the second virtual frequency according to the n frequencies is:
f′=f1+f2;
Where f' represents the second virtual frequency, f 1 represents the 1 st frequency, and f 2 represents the 2 nd frequency.
In application, when the transmitter transmits the pulse light beams with two frequencies to the object to be measured, the processing circuit can acquire the sum of the 1 st frequency and the 2 nd frequency as the second virtual frequency.
Step S502, calculating an initial flight time corresponding to the second virtual frequency according to the second virtual frequency and a phase for constructing the initial flight time corresponding to the second virtual frequency.
In one embodiment, the calculation formula for calculating the initial flight time corresponding to the second virtual frequency in step S502 is as follows:
Assuming a second virtual frequency f' =f i+fj, then
Wherein, Representing an initial time of flight corresponding to the second virtual frequency,Representing the phase of a third initial time of flight corresponding to the first frequency used to construct the second virtual frequency,Representing the phase of a fourth initial time of flight corresponding to another frequency used to construct the second virtual frequency.
In the application, the sum of the time of m complete cycles elapsed by the initial flight time corresponding to the second virtual frequency and the initial flight time corresponding to the second virtual frequency is calculated as the calibration flight time. The measured time of flight satisfies the following relationship: Representing a multiple of the period corresponding to a measured flight time exceeding the second virtual frequency f', taking the period number equal to 0, i.e The initial flight time corresponding to the second virtual frequency can be obtainedSince the trigonometric function has periodicity, the trigonometric function is calculated by the formulaThe initial flight time corresponding to the two second virtual frequencies can be calculated by a calculation formula The application can overcome the periodicity of the trigonometric function by combining the two calculation formulas to calculate the initial flight time of the actual second virtual frequency.
Step S503, calculating a multiple of the measured flight time exceeding the period corresponding to the second virtual frequency according to the second virtual frequency, the initial flight time of the second virtual frequency, and the measured flight time.
In one embodiment, the calculation formula for calculating the multiple of the measured flight time exceeding the period corresponding to the second virtual frequency in step S503 is:
in application, the processing manner of measuring the multiple of the period corresponding to the flight time exceeding the second virtual frequency is consistent with the processing manner of the number of periods of the ith initial flight time in the step S401, which is not described herein.
Step S504, calculating to obtain a calibration flight time according to the second virtual frequency, the initial flight time of the second virtual frequency and the multiple of the period corresponding to the measured flight time exceeding the second virtual frequency.
In one embodiment, the calculation formula for calculating the calibration time of flight in step S504 is:
Wherein, And representing that the measured flight time exceeds the integral multiple of the period corresponding to the second virtual frequency.
In application, since the frequency value of the second virtual frequency is larger than the frequency value of the i-th frequency, a more accurate calibration time of flight can be calculated.
In application, the second virtual frequency is constructed according to n frequencies sent by the reflector, the initial flight time corresponding to the second virtual frequency is calculated according to the second virtual frequency and the phase of the initial flight time corresponding to the two frequencies used for constructing the second virtual frequency, and the measurement flight time is further combined with the calculation and calibration of the integral multiple of the period corresponding to the second virtual frequency, and the frequency value of the second virtual frequency is far greater than the frequency value of the ith frequency.
The distance measurement method comprises the steps of transmitting n kinds of frequency pulse light beams to an object to be measured through a control transmitter, controlling a collector to collect photons in the n kinds of frequency pulse light beams reflected by the object to be measured and output a plurality of photon signals, calculating n initial flight times corresponding to the n kinds of frequencies one by one according to the plurality of photon signals, constructing virtual frequencies according to the n kinds of frequencies, and calculating measurement flight times by combining the n initial flight times, wherein n is an integer greater than or equal to 2. The method effectively improves the ranging precision, reduces the generation of random errors, can improve the ranging range and can calculate the flight time of the object to be measured which is positioned outside the maximum ranging range.
The embodiment of the application also provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program realizes the steps in the embodiments of the distance measuring method when being executed by a controller.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and in part, not described or illustrated in any particular embodiment, reference is made to the related descriptions of other embodiments. In the embodiments provided by the present application, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the device embodiments described above are merely illustrative.
The foregoing embodiments are merely for illustrating the technical solution of the present application, but not for limiting the same, and although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solution described in the foregoing embodiments may be modified or substituted for some of the technical features thereof, and that these modifications or substitutions should not depart from the spirit and scope of the technical solution of the embodiments of the present application and should be included in the protection scope of the present application.
Claims (8)
1. A distance measurement method, comprising:
Controlling the transmitter to transmit pulse light beams with n frequencies to an object to be measured;
the control collector collects photons in the n frequency pulse beams reflected by the object to be detected and outputs a plurality of photon signals;
calculating n initial flight times corresponding to the n frequencies one by one according to the photon signals;
Constructing virtual frequencies according to the n frequencies, and calculating and measuring flight time by combining the n initial flight time, wherein n is an integer greater than or equal to 2;
calculating calibration flight time according to the n frequencies, n initial flight times corresponding to the n frequencies one by one and measured flight time, wherein the calculation comprises the steps of constructing a second virtual frequency according to the n frequencies, calculating the initial flight time corresponding to the second virtual frequency according to the second virtual frequency and phases of the initial flight times corresponding to the two frequencies used for constructing the second virtual frequency, calculating the multiple of the measured flight time exceeding the period corresponding to the second virtual frequency according to the second virtual frequency, the initial flight time of the second virtual frequency and the measured flight time, and calculating the calibration flight time according to the multiple of the period corresponding to the second virtual frequency, the period corresponding to the second virtual frequency exceeding the period corresponding to the second virtual frequency.
2. The distance measurement method of claim 1, wherein said constructing virtual frequencies from said n frequencies and calculating measured time-of-flight in combination with said n initial time-of-flight comprises:
Selecting two frequencies according to the n frequencies to construct a first virtual frequency;
calculating the measurement flight time according to the first virtual frequency and the phases of the initial flight time corresponding to the two frequencies used for constructing the first virtual frequency;
the phase of the initial flight time is calculated according to an ith frequency and an ith initial flight time corresponding to the ith frequency, i=1, 2.
3. The distance measurement method according to claim 2, wherein the calculation formula of the phase of the initial time of flight is:
Wherein, A phase representing the i-th initial flight time, f i representing the i-th frequency, t i representing the i-th initial flight time corresponding to the i-th frequency;
the calculation formula for constructing the first virtual frequency according to the n frequencies is as follows:
fk ′＝|fi-fj|,k=1,2,...,n(n-1)/2,j=1,2,...,n,i≠j;
f=min(fk ′);
Wherein f k ′ represents an absolute value of a difference between the i-th frequency and the j-th frequency, f represents a first virtual frequency, and min (f k ′) represents a minimum value of absolute values of differences between any two different frequencies of the n frequencies;
the calculation formula for calculating the measurement flight time according to the first virtual frequency and the phases of the initial flight time corresponding to the two frequencies for constructing the first virtual frequency is as follows:
Wherein, Representing the time of flight of the measurement,Representing the phase of a first initial time of flight corresponding to one of the frequencies used to construct the first virtual frequency,Representing the phase of a second initial time of flight corresponding to another frequency used to construct the first virtual frequency.
4. The distance measurement method according to claim 1, wherein the calculating the calibration time of flight from the n frequencies, the n initial times of flight corresponding to the n frequencies one to one, and the measured time of flight includes:
Calculating an ith cycle number according to an ith frequency, an ith initial flight time corresponding to the ith frequency and the measured flight time, wherein the ith cycle number is a multiple of a cycle corresponding to the ith frequency exceeded by the measured flight time;
and calculating the calibration flight time according to the ith frequency, the ith initial flight time corresponding to the ith frequency and the ith period number.
5. The distance measuring method according to claim 4, wherein the calculation formula for calculating the i-th cycle number based on the i-th frequency, the i-th initial flight time corresponding to the i-th frequency, and the measured flight time is:
Wherein m i represents the i-th cycle number, Representing the measured time of flight, t i representing an i-th initial time of flight corresponding to the i-th frequency, f i representing the i-th frequency;
the calculation formula for calculating the calibration flight time according to the ith frequency, the ith initial flight time and the ith period number is as follows:
Where t represents the calibration time of flight and round (m i) represents the number of cycles of the ith rounding.
6. The distance measuring method according to any one of claims 1 to 5, wherein the transmitter is controlled to transmit two pulsed light beams of frequencies f 1 and f 2, respectively, to the object to be measured, and the first initial time of flight and the second initial time of flight corresponding to the two frequencies, respectively, are calculated.
7. A distance measurement system comprising a transmitter, a collector, and a processing circuit coupled to the transmitter and the collector;
The emitter is used for emitting pulse light beams with n frequencies to an object to be detected;
The collector is used for collecting photons in the n frequency pulse beams reflected by the object to be detected and outputting a plurality of photon signals;
the processing circuit for performing the steps of the distance measuring method according to any one of claims 1 to 5.
8. A computer-readable storage medium storing a computer program, characterized in that the computer program, when being executed by a processing circuit, implements the steps of the distance measurement method according to any one of claims 1 to 5.
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