CN111983630A - Single photon ranging system, method, terminal equipment and storage medium - Google Patents
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Abstract
The application is applicable to the technical field of flight time, and provides a single photon distance measuring system, a single photon distance measuring method, terminal equipment and a storage medium, wherein a light pulse signal is emitted by controlling a light emitter, and the light pulse signal is transmitted to a target after being attenuated by a variable optical attenuator at the maximum transmittance; controlling the single photon detector to receive an optical signal reflected by a target and processing the optical signal into an optical sensing signal; acquiring the distance between a target and a single photon detector according to the light sensing signal; when the distance is smaller than the distance threshold, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the distance; or acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal; when the light intensity is greater than the light intensity threshold value, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the light intensity, so that the number of photons received by the single photon detector in a pulse period can be reduced when the distance of the target is too close or the light intensity of an optical signal reflected by the target is too strong, and the measurement accuracy is improved.
Description
Technical Field
The application belongs to the technical field of Time of flight (TOF), and particularly relates to a single photon ranging system, a single photon ranging method, a terminal device and a storage medium.
Background
The time-of-flight ranging method is a method in which an optical pulse signal is continuously transmitted to a target, and then an optical signal reflected by the target is received, and the distance to the target is obtained by detecting the time of flight (round trip) of the optical pulse signal. The single photon ranging system based on the flight time technology is widely applied to terminal equipment in the fields of consumer electronics, unmanned driving, virtual reality, augmented reality and the like. The Single Photon ranging system generally includes a light emitter and a Single Photon Detector (SPD), and in order to accurately measure the flight time of an optical pulse signal, the Single Photon Detector is required to receive a small number of photons in one pulse period of the optical pulse signal, and when the number of photons received by the Single Photon Detector in one pulse period of the optical pulse signal is too large, a large measurement error is easily caused.
Disclosure of Invention
In view of this, embodiments of the present application provide a single photon ranging system, a single photon ranging method, a terminal device, and a storage medium, so as to solve the problem in the prior art that when the number of photons received by a single photon detector in one pulse period of an optical pulse signal is too large, a large measurement error is easily caused.
A first aspect of an embodiment of the present application provides a distance measurement method for a single photon distance measurement system, where the single photon distance measurement system includes a controller, a light emitter, a single photon detector, and an adjustable optical attenuator covering the light emitter, the controller is electrically connected to the light emitter, the single photon detector, and the adjustable optical attenuator, respectively, and the distance measurement method includes the following steps executed by the controller:
controlling the optical transmitter to transmit an optical pulse signal, wherein the optical pulse signal is transmitted to a target after being attenuated by the variable optical attenuator at the maximum transmittance;
controlling the single photon detector to receive the optical signal reflected by the target and process the optical signal into an optical sensing signal;
acquiring the distance between the target and the single photon detector according to the optical sensing signal;
when the distance is smaller than a distance threshold value, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the distance;
or acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal;
and when the light intensity is greater than a light intensity threshold value, adjusting the transmittance of the variable optical attenuator to be the transmittance corresponding to the light intensity.
A second aspect of the embodiments of the present application provides a distance measurement method for a single photon distance measurement system, where the single photon distance measurement system includes a controller, a light emitter, a single photon detector, and a light attenuation sheet covering the light emitter, the controller is electrically connected to the light emitter and the single photon detector, the single photon detector includes a single photon sensor array formed by a plurality of single photon sensors, the light attenuation sheet includes at least two attenuation regions that are alternately arranged and have incompletely identical transmittance, and the distance measurement method includes the following steps executed by the controller:
controlling the optical transmitter to transmit an optical pulse signal, wherein the optical pulse signal is transmitted to a target after being attenuated by the optical attenuation sheet;
controlling the single photon detector to receive the optical signal reflected by the target and process the optical signal into a first optical sensing signal;
acquiring a first distance between the target and the single-photon detector according to the first photoinduction signal;
when the first distance is smaller than a distance threshold, acquiring a second light sensing signal output by a single photon sensor receiving a first light signal reflected by the target; the first optical signal is transmitted to the target after being attenuated by an attenuation region with the transmittance positively correlated with the first distance in the optical pulse signal, and is reflected to the single-photon detector by the target;
acquiring a second distance between the target and the single-photon detector according to the second optical sensing signal;
or acquiring the light intensity of the optical signal reflected by the target according to the first optical sensing signal;
when the light intensity is greater than a light intensity threshold value, acquiring a third light sensing signal output by a single photon sensor receiving a second light signal reflected by the target; the second optical signal is transmitted to the target after being attenuated by an attenuation region with the transmittance inversely related to the light intensity in the optical pulse signal, and is reflected to the single-photon detector by the target;
and acquiring a third distance between the target and the single-photon detector according to the third photoinduction signal.
A third aspect of the embodiments of the present application provides a single photon ranging system, including a controller, a light emitter, a single photon detector, and an adjustable optical attenuator covering the light emitter, where the controller is electrically connected to the light emitter, the single photon detector, and the adjustable optical attenuator, respectively, and the controller is configured to execute the ranging method according to the first aspect of the embodiments of the present application.
A fourth aspect of the embodiments of the present application provides a single photon distance measuring system, including a controller, a light emitter, a single photon detector, and an optical attenuation sheet covering the light emitter, where the controller is electrically connected to the light emitter and the single photon detector, the single photon detector includes a single photon sensor array formed by a plurality of single photon sensors, the optical attenuation sheet includes at least two attenuation regions that are alternately arranged and have different transmittances, and the controller is configured to execute the distance measuring method according to the second aspect of the embodiments of the present application.
A fifth aspect of the embodiments of the present application provides a terminal device, including the single photon ranging system according to the third or fourth aspect of the embodiments of the present application.
A sixth aspect of embodiments of the present application provides a computer-readable storage medium, which stores a computer program, and the computer program, when executed by a controller, implements the steps of the ranging method according to the first aspect or the second aspect of embodiments of the present application.
A first aspect of the embodiments of the present application provides a distance measuring method for a single photon distance measuring system, where the single photon distance measuring system includes a controller, a light emitter, a single photon detector, and a variable optical attenuator covering the light emitter, where the controller is electrically connected to the light emitter, the single photon detector, and the variable optical attenuator, respectively, and controls the light emitter to emit a light pulse signal, so that the light pulse signal is attenuated by the variable optical attenuator at a maximum transmittance and then transmitted to a target; controlling the single photon detector to receive an optical signal reflected by a target and processing the optical signal into an optical sensing signal; acquiring the distance between a target and a single photon detector according to the light sensing signal; when the distance is smaller than the distance threshold, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the distance; or acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal; when the light intensity is greater than the light intensity threshold value, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the light intensity, and when the distance between the target and the single-photon detector is too close or the light intensity of the optical signal reflected by the target is too strong, the transmittance of the variable optical attenuator is adaptively adjusted to reduce the light intensity of the optical pulse signal transmitted to the target, so that the number of photons received by the single-photon detector in one pulse period of the optical pulse signal is effectively reduced, the measurement error is reduced, and the measurement precision is improved.
A second aspect of the embodiments of the present application provides a distance measuring method for a single photon distance measuring system, where the single photon distance measuring system includes a controller, a light emitter, a single photon detector, and an optical attenuation sheet covering the light emitter, the controller is electrically connected to the light emitter and the single photon detector, the single photon detector includes a single photon sensor array formed by a plurality of single photon sensors, and the optical attenuation sheet includes at least two attenuation regions that are alternately arranged and have different transmittances; the controller controls the light emitter to emit a light pulse signal, and the light pulse signal is transmitted to a target after being attenuated by the light attenuation sheet; controlling the single photon detector to receive an optical signal reflected by a target and processing the optical signal into a first optical sensing signal; acquiring a first distance between a target and a single photon detector according to a first light sensing signal; when the first distance is smaller than the distance threshold, acquiring a second light sensing signal output by the single photon sensor receiving a first light signal reflected by the target; the first optical signal is transmitted to a target after being attenuated by an attenuation region with the transmittance positively correlated with the first distance in the optical pulse signal, and is reflected to the single-photon detector by the target; acquiring a second distance between the target and the single photon detector according to the second optical sensing signal; or acquiring the light intensity of the optical signal reflected by the target according to the first optical sensing signal; when the light intensity is greater than the light intensity threshold value, acquiring a third light sensing signal output by the single photon sensor receiving a second light signal reflected by the target; the second optical signal is an optical signal which is transmitted to a target after being attenuated by an attenuation region with the transmittance negatively correlated with the light intensity in the optical pulse signal and is reflected back to the single photon detector by the target; the third distance between the target and the single-photon detector is obtained according to the third light-induced signal, when the distance between the target and the single-photon detector is too close or the light intensity of the light signal reflected by the target is too strong, the distance between the target and the single-photon detector can be obtained according to the light-induced signal output by the single-photon sensor covered by the attenuation area with the lower transmittance, so that the measurement error can be effectively reduced, and the measurement precision is improved.
It is to be understood that, for the beneficial effects of the third aspect, reference may be made to the relevant description in the first aspect, for the beneficial effects of the fourth aspect, reference may be made to the relevant description in the second aspect, and for the beneficial effects of the fifth aspect and the sixth aspect, reference may be made to the relevant description in the first aspect or the second aspect, which is not repeated herein.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions 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 it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a first single photon ranging system provided in an embodiment of the present application;
fig. 2 is a schematic flowchart of a first ranging method according to an embodiment of the present disclosure;
FIG. 3 is a schematic structural diagram of a second single photon ranging system provided in the embodiments of the present application;
FIG. 4 is a schematic diagram of a first structure of an optical attenuation sheet according to an embodiment of the present application;
FIG. 5 is a schematic diagram of a second structure of an optical attenuation sheet according to an embodiment of the present application;
fig. 6 is a flowchart illustrating a second ranging 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 particular system structures, 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, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
It will 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 this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
As used in this specification and the appended claims, the term "if" may be interpreted contextually as "when", "upon" or "in response to" determining "or" in response to detecting ". Similarly, the phrase "if it is determined" or "if a [ described condition or event ] is detected" may be interpreted contextually to mean "upon determining" or "in response to determining" or "upon detecting [ described condition or event ]" or "in response to detecting [ described condition or event ]".
Furthermore, in the description of the present application and the appended claims, the terms "first," "second," "third," and the like are used for distinguishing between descriptions and not necessarily for describing or implying relative importance.
Reference throughout this 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 present application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," or the like, in various places throughout this specification are not necessarily all referring to the same embodiment, but rather "one or more but not all embodiments" unless specifically stated otherwise. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless expressly specified otherwise.
As shown in fig. 1, the single photon distance measuring system 100 according to the embodiment of the present application includes a controller 1, a light emitter 2, a single photon detector 3, and a Variable Optical Attenuator (VOA) 4 covering the light emitter 2, where the controller 1 is electrically connected to the light emitter 2, the single photon detector 3, and the Variable Optical Attenuator 4 respectively; the optical pulse signal emitted by the optical transmitter 2 is attenuated by the variable optical attenuator 4 and then transmitted to the target 200, the optical signal reflected by the target 200 is received by the single photon detector 3, the solid line represents the electrical connection, and the dotted line with the arrow represents the optical signal.
In application, the single photon distance measuring system at least comprises a controller, a light emitter, a single photon detector and an adjustable Optical attenuator, and further comprises a collimating Optical element and a Diffractive Optical Element (DOE) covering the light emitter, a focusing lens or a micro lens array covering the single photon detector, and the like, wherein the collimating Optical element and the Diffractive Optical element can be sequentially arranged between the light emitter and the adjustable Optical attenuator, and the adjustable Optical attenuator can be arranged between the light emitter and the collimating Optical element. The collimating optical element is used for collimating the optical pulse signal emitted by the optical emitter, and the diffraction optical element is used for diffracting the optical pulse signal. The lens or the micro-lens array is used for focusing the optical signal reflected by the target on the photosensitive surface of the single-photon detector. The controller is used for controlling the light emitter, the single photon detector and the variable optical attenuator to be turned on or turned off and adjusting the transmittance of the variable optical attenuator so as to change the light intensity of the light pulse signal emitted to the target. The target may be any object in free space that can reflect the optical pulse signals emitted by a single photon ranging system.
In application, the Light emitter may be set as a Laser, a Light Emitting Diode (LED), a Laser Diode (LD), an Edge-Emitting Laser (EEL), or the like according to actual needs. The Laser may be a Vertical-Cavity Surface-Emitting Laser (VCSEL). The light emitter can be a tunable or non-tunable device, and the light intensity of the light pulse signal emitted by the light emitter is changed only through the adjustable attenuator by setting the light emitter as the non-tunable device, so that the design difficulty of the single photon ranging system can be effectively reduced, and the cost is reduced.
In application, the variable optical attenuator can be set as a Liquid Crystal Diffraction Grating (Liquid Crystal Diffraction Grating), a mechanical optical attenuator or a magneto-optical attenuator with adjustable transmittance according to actual needs.
In application, the Single-Photon detector may be set to include only a Single-Photon sensor or a Single-Photon sensor array formed by a plurality of Single-Photon sensors according to actual needs, and the Single-Photon sensor may be a Single Photon Avalanche photodiode (SPAD). The Single Photon avalanche photodiode can respond to an incident Single Photon and output a signal for indicating the Time when the Photon reaches the Single Photon avalanche photodiode, and based on the Single Photon avalanche photodiode, the weak light signal can be acquired and the flight Time can be calculated by using a Time-Correlated Single Photon Counting (TCSPC) method. The single photon detector may further include at least one of a signal amplifier, a Time-to-Digital Converter (TDC), an Analog-to-Digital Converter (ADC), and the like electrically connected to the single photon sensor or the single photon sensor array, and these devices may be integrated with the single photon sensor or the single photon sensor array to form the single photon detector, or may be a part of the controller.
In Application, the controller may be a Central Processing Unit (CPU), other general purpose controller, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, a discrete hardware component, and the like. The general controller may be a microcontroller or any conventional controller or the like.
As shown in fig. 2, an embodiment of the present application provides a distance measurement method implemented based on the single photon distance measurement system 100 in the embodiment corresponding to fig. 1, including the following steps implemented by the controller 3:
step S201, controlling the optical transmitter to transmit an optical pulse signal, wherein the optical pulse signal is transmitted to a target after being attenuated by the variable optical attenuator at the maximum transmittance, and the step S202 is carried out;
step S202, controlling the single photon detector to receive the optical signal reflected by the target and process the optical signal into an optical sensing signal, and entering step S203 or S205.
In application, when the controller controls the variable optical attenuator to start, the variable optical attenuator may be first controlled to initialize, and the transmittance of the variable optical attenuator is adjusted to be maximum, so that the attenuation degree of the optical pulse signal emitted by the optical transmitter after starting is minimum. The controller can send synchronous signals to the light emitter and the single-photon detector after controlling the variable optical attenuator to start and initialize and adjusting the transmittance of the variable optical attenuator to be maximum so as to synchronize the emission time of the light pulse signal emitted by the light emitter and the receiving time of the light signal reflected by the target received by the single-photon detector.
In one embodiment, before step S201, the method includes:
and adjusting the transmittance of the variable optical attenuator to be the maximum transmittance.
In application, when the distance between the target and the single-photon detector is too close or the light intensity of an optical signal reflected by the target is too strong, the single-photon detector receives too many photons in one pulse period of an optical pulse signal, so that a large measurement error is caused. Therefore, whether the transmittance of the variable optical attenuator is adaptively adjusted or not can be determined by detecting whether the distance between the target and the single-photon detector is smaller than a distance threshold or whether the light intensity of the optical signal reflected by the target is larger than a light intensity threshold, so that the number of photons received by the single-photon detector in one pulse period of the optical pulse signal is reduced, the measurement error is reduced, and the measurement accuracy is improved.
Step S203, acquiring the distance between the target and the single photon detector according to the optical sensing signal, and entering step S204;
and step S204, when the distance is smaller than a distance threshold value, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the distance.
In application, the steps S203 and S204 are to determine whether to adaptively adjust the transmittance of the variable optical attenuator by detecting whether the distance between the target and the single-photon detector is smaller than a distance threshold. Specifically, the controller obtains the flight time of the optical pulse signal emitted by the light emitter by adopting a time-dependent single photon counting method according to the optical sensing signal output by the single photon detector, so as to calculate the distance between the target and the single photon detector according to the flight time, wherein the calculation formula is as follows:
D＝c*t/2；
where D represents the distance of the target, c represents the speed of light, and t represents the time of flight.
In application, when the transmittance of the adjustable optical attenuator is initialized, the transmittance of the adjustable optical attenuator is adjusted to the maximum transmittance, so that the measurement of the target with the distance from the single-photon detector being greater than or equal to the distance threshold can be realized under the condition that the number of photons received by the single-photon detector in one pulse period of the optical pulse signal is less. Therefore, when the distance between the object and the single-photon detector is smaller than the distance threshold, the transmittance of the variable optical attenuator needs to be reduced, in which case the transmittance corresponding to the distance is smaller than the maximum transmittance.
In the application, in the case that the distance between the target and the single-photon detector is smaller than the distance threshold, the relationship between the distance between the target and the single-photon detector and the transmittance that the variable optical attenuator should achieve can be obtained by pre-measurement, for example, can measure targets at different distances in advance through a single-photon distance measuring system, continuously adjust the transmittance of the variable optical attenuator when measuring the target at each distance, when the number of photons received by the single-photon detector within one pulse period of the optical pulse signal is equal to the preset number threshold, recording the distance and the transmittance at the moment and establishing the corresponding relationship between the distance and the transmittance, so as to obtain the corresponding relationship between different distances and corresponding transmittances, therefore, when the distance is smaller than the distance threshold value, the corresponding transmittance can be quickly found according to the recorded corresponding relation and the recorded distance. The preset number threshold value can be set to any value between 0.01 and 0.1.
In one embodiment, step S204 includes:
when the distance is smaller than a distance threshold value, acquiring luminous power corresponding to the distance;
obtaining the transmittance corresponding to the distance according to the luminous power; after the variable optical attenuator attenuates the optical pulse signal at the transmittance corresponding to the distance, the optical intensity of the optical pulse signal is equal to the optical intensity of the optical pulse signal emitted by the optical emitter at the light emitting power.
In application, the corresponding relationship between the targets at different distances and the light emitting power that the light emitter should achieve can be obtained in advance, and then the transmittance that the variable optical attenuator should achieve is obtained according to the light emitting power of the light emitter. After the light emitting power is determined according to the distance, when the light emitting power of the light emitter is not adjustable, the light intensity attenuation effect equivalent to the adjustment of the light emitting power of the light emitter can be realized by adjusting the transmittance of the variable optical attenuator, that is, after the variable optical attenuator attenuates the light pulse signal at the transmittance corresponding to the distance, the light intensity of the light pulse signal is equivalent to the light intensity of the light pulse signal emitted by the light emitter at the light emitting power corresponding to the distance.
In one embodiment, the obtaining the luminous power corresponding to the distance when the distance is less than a distance threshold value includes:
obtaining the luminous power corresponding to the distance according to a preset relation and the distance, wherein the preset relation is as follows:
wherein, Plight sourceRepresenting said luminous power, R representing said distance, NeRepresenting the average photon number of a single pixel in the single photon detector after the light emitter emits a primary light pulse signal to a target, wherein FOV represents the field angle of a lens of the single photon detector, FF represents a filling factor, ApixelRepresents the area of a single pixel in the single-photon detector, h represents the Planck constant, c represents the speed of light, TpulseRepresenting the pulse time of the light emitter, ρ representing the reflectivity of the target, F representing the focal length of the lens of the single-photon detector, F/# representing the aperture of the lens of the single-photon detector, koptRepresents the loss of optical components of the single photon detector, PDE represents the photon detection efficiency of the single photon detector, and λ is the center wavelength of the light emitter.
In application, the obtained corresponding relationship between the targets at different distances and the light emitting power that the light emitter should achieve is the preset relationship. The light emitting power is unknown quantity, the distance and the average photon number are known quantities obtained according to the light sensing signal, and the field angle, the filling factor, the area of a single pixel, the Planck constant, the light speed, the pulse time, the reflectivity of a target, the focal length of a lens, the aperture of the lens, the loss of an optical component, the photon detection efficiency and the central wavelength are all predetermined known quantities.
In one embodiment, after step S204, the method comprises:
returning to execute the step of acquiring the distance between the target and the single-photon detector according to the optical sensing signal;
and when the distance is greater than or equal to a distance threshold value, adjusting the transmittance of the variable optical attenuator to the maximum transmittance.
In application, after the distance between the target and the single-photon detector is smaller than the distance threshold and the transmittance of the variable optical attenuator is adjusted to be smaller than the transmittance of the maximum transmittance, the step S404 may be executed again to continuously detect the distance between the target and the single-photon detector, so that when the distance between the target and the single-photon detector changes, the transmittance of the variable optical attenuator may be adaptively adjusted to enable the single-photon ranging system to always work in a state with high measurement accuracy.
In an application, the controller may return to execute step S204 at a first preset time, where the first preset time may be set according to actual needs, for example, the first preset time may be set as a time when a trigger instruction input by a user is received, or may be set as a first time at every interval or in real time. The first time may be set to any time period, for example, 30 seconds or 1 minute, according to actual needs.
Step S205, acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal, and entering step S206;
and step S206, when the light intensity is greater than the light intensity threshold value, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the light intensity.
In application, steps S205 and S206 determine whether to adaptively adjust the transmittance of the variable optical attenuator by detecting whether the optical intensity of the optical signal reflected by the target is greater than the optical intensity threshold. Specifically, the controller obtains the light intensity of the optical signal reflected by the target by adopting a time-dependent single photon counting method according to the optical sensing signal output by the single photon detector.
In application, when the transmittance of the variable optical attenuator is initialized, the transmittance of the variable optical attenuator is adjusted to the maximum transmittance, so that the target with the light intensity of the reflected optical signal smaller than or equal to the light intensity threshold can be measured under the condition that the single-photon detector is ensured to receive fewer photons in one pulse period of the optical pulse signal. Therefore, when the light intensity of the optical signal reflected by the target is greater than the light intensity threshold, the transmittance of the variable optical attenuator needs to be reduced, in which case the transmittance corresponding to the light intensity is less than the maximum transmittance. In the case where the light intensity of the optical signal reflected by the target is greater than the light intensity threshold value, the relationship between the light intensity of the optical signal reflected by the target and the transmittance that should be achieved by the variable optical attenuator can be obtained by measuring, for example, the single photon ranging system can be used for measuring targets with different light intensities of the reflected light signals in advance, the transmittance of the variable optical attenuator can be continuously adjusted when each target is measured, when the number of photons received by the single-photon detector within one pulse period of the optical pulse signal is equal to the preset number threshold, recording the light intensity and transmittance at the moment and establishing the corresponding relationship between the light intensity and the transmittance, thus obtaining the corresponding relationship between different light intensities and corresponding transmittances, therefore, when the light intensity is greater than the light intensity threshold value, the corresponding transmittance can be quickly found according to the recorded corresponding relation and the light intensity.
In one embodiment, after step S206, the method includes:
returning to execute the step of acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal;
and when the light intensity is less than or equal to a light intensity threshold value, adjusting the transmittance of the variable optical attenuator to the maximum transmittance.
In application, after the light intensity of the optical signal reflected by the target is greater than the light intensity threshold value and the transmittance of the variable optical attenuator is adjusted to a transmittance smaller than the maximum transmittance, the process may return to step S206 to continue to detect the light intensity of the optical signal reflected by the target, so that when the light intensity of the optical signal reflected by the target changes, the transmittance of the variable optical attenuator may be adaptively adjusted to enable the single-photon ranging system to always operate in a state with high measurement accuracy.
In application, the controller may return to execute step S406 at a second preset time, where the second preset time may be set according to actual needs, for example, the second preset time may be set as a time when a trigger instruction input by a user is received, or may be set as a second time per interval or in real time. The second time can be set to any time length according to actual needs, for example, 30 seconds or 1 minute.
The embodiment corresponding to fig. 2 provides a distance measurement method implemented based on the single-photon distance measurement system in the embodiment corresponding to fig. 1, and the optical transmitter is controlled to transmit an optical pulse signal, so that the optical pulse signal is transmitted to a target after being attenuated by the variable optical attenuator with the maximum transmittance; controlling the single photon detector to receive an optical signal reflected by a target and processing the optical signal into an optical sensing signal; acquiring the distance between a target and a single photon detector according to the light sensing signal; when the distance is smaller than the distance threshold, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the distance; or acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal; when the light intensity is greater than the light intensity threshold value, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the light intensity, and when the distance between the target and the single-photon detector is too close or the light intensity of the optical signal reflected by the target is too strong, the transmittance of the variable optical attenuator is adaptively adjusted to reduce the light intensity of the optical pulse signal transmitted to the target, so that the number of photons received by the single-photon detector in one pulse period of the optical pulse signal is effectively reduced, the measurement error is reduced, and the measurement precision is improved.
As shown in fig. 3, an embodiment of the present application provides a single photon distance measuring system 300, which includes a controller 1, a light emitter 2, a single photon detector 3, and a light attenuation sheet 5 covering the light emitter 2, where the controller 1 is electrically connected to the light emitter 2 and the single photon detector 3, the single photon detector 3 includes a single photon sensor array formed by a plurality of single photon sensors, and the light attenuation sheet 5 includes at least two attenuation regions that are alternately arranged and have different transmittances; the optical pulse signal emitted by the optical emitter 2 is attenuated by the optical attenuation sheet 5 and then transmitted to the target 200, the optical signal reflected by the target 200 is received by the single photon detector 3, the solid line represents the electrical connection, and the dotted line with the arrow represents the optical signal.
The structure of the device with the same name in the embodiment corresponding to fig. 1 in fig. 3 is the same, and is not described herein again, except that the single photon detector in the embodiment corresponding to fig. 3 must include a single photon sensor array formed by a plurality of single photon sensors.
In application, the single photon distance measuring system at least comprises a controller, a light emitter, a single photon detector and a light attenuation sheet, and also comprises a collimating optical element and a diffracting optical element which cover the light emitter, a focusing lens or a micro-lens array which cover the single photon detector and the like, wherein the collimating optical element and the diffracting optical element can be sequentially arranged between the light emitter and the light attenuation sheet, and the light attenuation sheet can be arranged between the light emitter and the collimating optical element. The collimating optical element is used for collimating the optical pulse signal emitted by the optical emitter, and the diffraction optical element is used for diffracting the optical pulse signal. The lens or the micro-lens array is used for focusing the optical signal reflected by the target on the photosensitive surface of the single-photon detector. The controller is used for controlling the light emitter and the single-photon detector to be turned on or turned off, and selectively acquiring light sensing signals output by the single-photon sensors in different areas in the single-photon detector so as to change a distance measurement result.
In application, the light attenuating panel may include at least two attenuation regions arranged in a one-dimensional or two-dimensional array. When the light attenuation sheet comprises at least two attenuation regions arranged in a one-dimensional array, the attenuation regions may be in the shape of a strip, and the transmittance of any two adjacent attenuation regions is different. When the light attenuation sheet includes at least two attenuation regions arranged in a two-dimensional array, the attenuation regions may be rectangular in shape, and any two adjacent attenuation regions have different transmittances. When the number of attenuation regions is greater than two, the transmittance of each attenuation region may be set to be different, or the transmittance of a part of attenuation regions may be set to be the same, as long as the light attenuation sheet is ensured to have attenuation regions with at least two transmittances. The transmittance of each attenuation region can be set according to actual needs, and can be uniformly distributed between 0% and 100%, for example, when the light attenuation sheet has attenuation regions with two transmittances, one transmittance can be 50%, and the other transmittance can be 100%; when the optical attenuation sheet has attenuation regions of ten kinds of transmittance, the ten kinds of transmittance may be 10%, 20%, …, and 100%, respectively.
As shown in FIG. 4, the exemplary light-attenuating sheet 5 is shown to include a plurality of strip-shaped attenuation regions arranged in a one-dimensional array; here, the attenuation region having the first transmittance is denoted as 51, and the attenuation region having the second transmittance is denoted as 52.
As shown in FIG. 5, the exemplary illustrated light attenuation sheet 5 includes a plurality of rectangular attenuation regions arranged in a two-dimensional array; the attenuation region having the first transmittance is denoted by 51, the attenuation region having the second transmittance is denoted by 52, and the attenuation region having the third transmittance is denoted by 53.
As shown in fig. 6, an embodiment of the present application provides a distance measurement method implemented based on the single photon distance measurement system 200 in the embodiment corresponding to fig. 3, including the following steps implemented by the controller 3:
step S601, controlling the light emitter to emit a light pulse signal, transmitting the light pulse signal to a target after the light pulse signal is attenuated by the light attenuation sheet, and entering step S602;
step S602, controlling the single photon detector to receive the optical signal reflected by the target and process the optical signal into a first optical sensing signal, and entering step S603 or S606.
In application, the controller may send synchronization signals to the light emitter and the single-photon detector to synchronize the emission time of the light pulse signal emitted by the light emitter and the receiving time of the light signal reflected by the target received by the single-photon detector.
In application, when the distance between the target and the single-photon detector is too close or the light intensity of an optical signal reflected by the target is too strong, the single-photon detector receives too many photons in one pulse period of an optical pulse signal, so that a large measurement error is caused. Therefore, whether the distance between the target and the single photon detector is recalculated according to the light sensing signal output by the single photon sensor receiving the light signal with lower light intensity reflected by the target can be determined by detecting whether the distance between the target and the single photon detector is smaller than a distance threshold or whether the light intensity of the light signal reflected by the target is larger than a light intensity threshold, so as to improve the measurement accuracy. The optical pulse signals emitted by the light emitter are attenuated by at least two attenuation areas with incompletely same transmittance in the optical attenuation sheet to obtain optical signals with at least two light intensities and transmitted to a target, and the target reflects the optical signals with at least two light intensities back to the single photon detector, so that the single photon detector receives the optical signals with different light intensities.
Step S603, acquiring a first distance between the target and the single photon detector according to the first light sensing signal, and entering step S604;
step S604, when the first distance is smaller than the distance threshold, acquiring a second light sensing signal output by the single photon sensor receiving the first light signal reflected by the target, and entering step S605; the first optical signal is transmitted to the target after being attenuated by an attenuation region with the transmittance positively correlated with the first distance in the optical pulse signal, and is reflected to the single-photon detector by the target;
and step S605, acquiring a second distance between the target and the single photon detector according to the second light sensing signal.
In application, the steps S603 and S604 determine whether to recalculate the distance between the target and the single photon detector based on the light sensing signal output by the single photon sensor receiving the light signal with low light intensity reflected by the target by detecting whether the distance between the target and the single photon detector is smaller than a distance threshold. The first light sensing signal comprises light sensing signals output by all single photon sensors of the single photon detector, when the distance between a target and the single photon detector is smaller than a distance threshold value, the first distance between the target and the single photon detector, which is obtained according to the first light sensing signal, is inaccurate and cannot be used as a final distance measurement result, at the moment, a second light sensing signal output by the single photon sensor, which receives the first light signal reflected by the target, can be obtained, and the time-of-flight of an optical pulse signal emitted by the optical emitter is obtained by adopting a time-dependent single photon counting method, so that the second distance between the target and the single photon detector is calculated according to the time-of-flight, and the second distance is more accurate relative to the first. The first distance is positively correlated with the transmittance of an attenuation region for attenuating the optical pulse signal to obtain the first optical signal, that is, the closer the distance between the target and the single photon detector is, the more accurate the distance is calculated from the optical sensing signal output by the single photon sensor that receives the first optical signal after the first optical signal obtained by attenuating the optical pulse signal by the attenuation region having the lower transmittance is reflected back to the single photon detector by the target. When the first distance is larger than or equal to the distance threshold value, the first distance between the target and the single photon detector obtained according to the first light sensing signal is accurate and can be used as a final distance measurement result.
In application, when the first distance is smaller than the distance threshold, the relationship between the first distance and the transmittance may be obtained by pre-measuring, for example, measuring targets at different distances in advance by a single photon ranging system, and when measuring a target at each distance, obtaining the number of photons received by a single photon sensor receiving the first optical signal after a first optical signal obtained by attenuating an optical pulse signal by an attenuation region of each transmittance is reflected back to a single photon detector by the target, and when the number of photons received by the single photon sensor receiving the first optical signal in one pulse period of the optical pulse signal is equal to a preset number threshold after the first optical signal obtained by attenuating the optical pulse signal by a certain attenuation region is reflected back to the single photon detector by the target, recording the corresponding relationship between the transmittance of the attenuation region and the distance at that time, therefore, the corresponding relation between different distances and corresponding transmittances can be obtained, and the corresponding transmittances can be quickly found according to the recorded corresponding relation and the recorded distances when the distances are smaller than the distance threshold. The preset number threshold value can be set to any value between 0.01 and 0.1.
Step S606, obtaining the light intensity of the optical signal reflected by the target according to the first optical sensing signal, and entering step S607;
step S607, when the light intensity is greater than the light intensity threshold, acquiring a third light sensing signal output by the single photon sensor receiving the second light signal reflected by the target, and entering step S608; the second optical signal is transmitted to the target after being attenuated by an attenuation region with the transmittance inversely related to the light intensity in the optical pulse signal, and is reflected to the single-photon detector by the target;
and step S608, acquiring a third distance between the target and the single photon detector according to the third photoinduction signal.
In application, steps S606 and S607 determine whether to recalculate the distance between the target and the single photon detector based on the light sensing signal output from the single photon sensor receiving the light signal with low light intensity reflected by the target by detecting whether the light intensity of the light signal reflected by the target is greater than the light intensity threshold. The first light sensing signal comprises light sensing signals output by all single photon sensors of the single photon detector, when the light intensity of the light signal reflected by the target is larger than a light intensity threshold value, a first distance between the target and the single photon detector, which is obtained according to the first light sensing signal, is inaccurate and cannot be used as a final distance measurement result, a third light sensing signal output by the single photon sensor, which receives a second light signal reflected by the target, can be obtained at the moment, the flight time of the light pulse signal emitted by the light emitter is obtained by adopting a time-dependent single photon counting method, so that a third distance between the target and the single photon detector is calculated according to the flight time, and the third distance is more accurate relative to the first distance. The light intensity is inversely related to the transmittance of the attenuation region required to be selected, that is, the smaller the light intensity of the optical signal reflected by the target is, the more accurate the distance calculated from the optical sensing signal output by the single photon sensor receiving the second optical signal after the second optical signal obtained by attenuating the optical pulse signal according to the attenuation region with the lower transmittance is reflected back to the single photon detector by the target.
In application, when the light intensity is greater than the light intensity threshold, the relationship between the light intensity and the transmittance may be obtained by pre-measurement, for example, a single photon ranging system may be used to measure targets with different light intensities of the reflected light signals in advance, and when each target is measured, after a second light signal obtained by attenuating the light pulse signal by an attenuation region of each transmittance is reflected by the target to a single photon detector, the number of photons received by a single photon sensor receiving the second light signal in one pulse period of the light pulse signal is obtained, and when there is a second light signal obtained by attenuating the light pulse signal by a certain attenuation region reflected by the target to a single photon detector, and the number of photons received by the single photon sensor receiving the second light signal in one pulse period of the light pulse signal is equal to a preset number threshold, the corresponding relationship between the transmittance of the attenuation region and the light intensity at that time is recorded, therefore, the corresponding relation between different light intensities and corresponding transmittances can be obtained, and the corresponding transmittances can be quickly found according to the recorded corresponding relation and the recorded light intensities when the light intensities are greater than the light intensity threshold. When the light intensity is smaller than or equal to the light intensity threshold value, the first distance between the target and the single photon detector obtained according to the first light sensing signal is accurate and can be used as a final distance measurement result.
Fig. 6 illustrates an embodiment of a distance measurement method implemented by providing a single photon distance measurement system according to the embodiment of fig. 3, where a controller controls a light emitter to emit a light pulse signal, and the light pulse signal is attenuated by a light attenuation sheet and then transmitted to a target; controlling the single photon detector to receive an optical signal reflected by a target and processing the optical signal into a first optical sensing signal; acquiring a first distance between a target and a single photon detector according to a first light sensing signal; when the first distance is smaller than the distance threshold, acquiring a second light sensing signal output by the single photon sensor receiving a first light signal reflected by the target; the first optical signal is transmitted to a target after being attenuated by an attenuation region with the transmittance positively correlated with the first distance in the optical pulse signal, and is reflected to the single-photon detector by the target; acquiring a second distance between the target and the single photon detector according to the second optical sensing signal; or acquiring the light intensity of the optical signal reflected by the target according to the first optical sensing signal; when the light intensity is greater than the light intensity threshold value, acquiring a third light sensing signal output by the single photon sensor receiving a second light signal reflected by the target; the second optical signal is an optical signal which is transmitted to a target after being attenuated by an attenuation region with the transmittance negatively correlated with the light intensity in the optical pulse signal and is reflected back to the single photon detector by the target; the third distance between the target and the single-photon detector is obtained according to the third light-induced signal, when the distance between the target and the single-photon detector is too close or the light intensity of the light signal reflected by the target is too strong, the distance between the target and the single-photon detector can be obtained according to the light-induced signal output by the single-photon sensor covered by the attenuation area with the lower transmittance, so that the measurement error can be effectively reduced, and the measurement precision is improved.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.
The distance measurement method of the single photon distance measurement system provided by the embodiment of the application can be applied to terminal devices such as mobile phones, tablet computers, wearable devices, vehicle-mounted devices, Augmented Reality (AR) devices, Virtual Reality (VR) devices, notebook computers, netbooks, Personal Digital Assistants (PDAs), and the like, and the embodiment of the application does not limit the specific types of the terminal devices at all. The terminal device comprises the single-photon ranging system in the embodiment corresponding to fig. 1 or fig. 3.
The embodiments of the present application further provide a computer-readable storage medium, where a computer program is stored, and when the computer program is executed by a controller, the steps in the foregoing ranging method embodiments may be implemented.
The embodiments of the present application further provide a computer program product, which when running on a terminal device, enables a mobile terminal to implement the steps in the foregoing ranging method embodiments when executed.
In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to the related descriptions of other embodiments for parts that are not described or illustrated in a certain embodiment. In the embodiments provided in the present application, it should be understood that the disclosed system/terminal device and method may be implemented in other ways. For example, the system/terminal device embodiments described above are merely illustrative.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (10)
1. A distance measurement method of a single photon distance measurement system is characterized in that the single photon distance measurement system comprises a controller, a light emitter, a single photon detector and an adjustable optical attenuator covering the light emitter, the controller is respectively and electrically connected with the light emitter, the single photon detector and the adjustable optical attenuator, and the distance measurement method comprises the following steps executed by the controller:
controlling the optical transmitter to transmit an optical pulse signal, wherein the optical pulse signal is transmitted to a target after being attenuated by the variable optical attenuator at the maximum transmittance;
controlling the single photon detector to receive the optical signal reflected by the target and process the optical signal into an optical sensing signal;
acquiring the distance between the target and the single photon detector according to the optical sensing signal;
when the distance is smaller than a distance threshold value, the transmittance of the variable optical attenuator is adjusted to be the transmittance corresponding to the distance;
or acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal;
and when the light intensity is greater than a light intensity threshold value, adjusting the transmittance of the variable optical attenuator to be the transmittance corresponding to the light intensity.
2. The distance measuring method of the single photon distance measuring system of claim 1 wherein said adjusting the transmittance of said variable optical attenuator to a transmittance corresponding to said distance when said distance is less than a distance threshold comprises:
when the distance is smaller than a distance threshold value, acquiring luminous power corresponding to the distance;
obtaining the transmittance corresponding to the distance according to the luminous power; after the variable optical attenuator attenuates the optical pulse signal at the transmittance corresponding to the distance, the optical intensity of the optical pulse signal is equal to the optical intensity of the optical pulse signal emitted by the optical emitter at the light emitting power.
3. The distance measurement method of the single photon distance measurement system of claim 2, wherein said obtaining the luminous power corresponding to said distance when said distance is smaller than a distance threshold comprises:
obtaining the luminous power corresponding to the distance according to a preset relation and the distance, wherein the preset relation is as follows:
wherein, Plight sourceRepresenting said luminous power, R representing said distance, NeRepresents the average photon number FO of a single pixel in the single photon detector after the light emitter transmits a light pulse signal to a targetV represents the field angle of the lens of the single-photon detector, FF represents the fill factor, ApixelRepresents the area of a single pixel in the single-photon detector, h represents the Planck constant, c represents the speed of light, TpulseRepresenting the pulse time of the light emitter, ρ representing the reflectivity of the target, F representing the focal length of the lens of the single-photon detector, F/# representing the aperture of the lens of the single-photon detector, koptRepresents the loss of optical components of the single photon detector, PDE represents the photon detection efficiency of the single photon detector, and λ is the center wavelength of the light emitter.
4. The distance measuring method of the single photon distance measuring system according to claim 2 or 3, wherein said adjusting the transmittance of said variable optical attenuator to the transmittance corresponding to said distance when said distance is less than a distance threshold value comprises:
returning to execute the step of acquiring the distance between the target and the single-photon detector according to the optical sensing signal;
and when the distance is greater than or equal to a distance threshold value, adjusting the transmittance of the variable optical attenuator to the maximum transmittance.
5. The distance measuring method of the single photon distance measuring system of claim 1, wherein said adjusting the transmittance of said variable optical attenuator to the transmittance corresponding to said light intensity when said light intensity is greater than a light intensity threshold value comprises:
returning to execute the step of acquiring the light intensity of the optical signal reflected by the target according to the optical sensing signal;
and when the light intensity is less than or equal to a light intensity threshold value, adjusting the transmittance of the variable optical attenuator to the maximum transmittance.
6. The distance measurement method of the single photon distance measurement system is characterized in that the single photon distance measurement system comprises a controller, a light emitter, a single photon detector and an optical attenuation sheet covering the light emitter, the controller is respectively and electrically connected with the light emitter and the single photon detector, the single photon detector comprises a single photon sensor array formed by a plurality of single photon sensors, the optical attenuation sheet comprises at least two attenuation areas which are alternately arranged and have incompletely same transmittance, and the distance measurement method comprises the following steps executed by the controller:
controlling the optical transmitter to transmit an optical pulse signal, wherein the optical pulse signal is transmitted to a target after being attenuated by the optical attenuation sheet;
controlling the single photon detector to receive the optical signal reflected by the target and process the optical signal into a first optical sensing signal;
acquiring a first distance between the target and the single-photon detector according to the first photoinduction signal;
when the first distance is smaller than a distance threshold, acquiring a second light sensing signal output by a single photon sensor receiving a first light signal reflected by the target; the first optical signal is transmitted to the target after being attenuated by an attenuation region with the transmittance positively correlated with the first distance in the optical pulse signal, and is reflected to the single-photon detector by the target;
acquiring a second distance between the target and the single-photon detector according to the second optical sensing signal;
or acquiring the light intensity of the optical signal reflected by the target according to the first optical sensing signal;
when the light intensity is greater than a light intensity threshold value, acquiring a third light sensing signal output by a single photon sensor receiving a second light signal reflected by the target; the second optical signal is transmitted to the target after being attenuated by an attenuation region with the transmittance inversely related to the light intensity in the optical pulse signal, and is reflected to the single-photon detector by the target;
and acquiring a third distance between the target and the single-photon detector according to the third photoinduction signal.
7. A single photon ranging system comprising a controller, a light emitter, a single photon detector and an adjustable optical attenuator covering the light emitter, the controller being electrically connected to the light emitter, the single photon detector and the adjustable optical attenuator respectively, the controller being configured to perform the ranging method of any one of claims 1 to 5.
8. The single-photon distance measuring system is characterized by comprising a controller, a light emitter, a single-photon detector and a light attenuation sheet covering the light emitter, wherein the controller is electrically connected with the light emitter and the single-photon detector respectively, the single-photon detector comprises a single-photon sensor array formed by a plurality of single-photon sensors, the light attenuation sheet comprises at least two attenuation areas which are arranged alternately and have different transmittances, and the controller is used for executing the distance measuring method of claim 6.
9. A terminal device comprising the single photon ranging system of claim 7 or 8.
10. A computer-readable storage medium, in which a computer program is stored which, when being executed by a controller, carries out the steps of the ranging method according to any one of claims 1 to 6 or claim 7.
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