CN117949960A - Emission module, device and related equipment for adjusting emission energy based on acousto-optic effect - Google Patents
Emission module, device and related equipment for adjusting emission energy based on acousto-optic effect Download PDFInfo
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Abstract
The application provides an emitting module based on an acousto-optic effect, which comprises a light source module, at least one acousto-optic deflection module and a control module. The light source module is configured to emit a light beam. The acousto-optic deflection module includes an acousto-optic interaction medium and an acoustic wave generator configured to generate an acoustic wave propagating in a preset direction within the acousto-optic interaction medium. The control module includes an acousto-optic deflection control unit configured to deflect a light beam passing through the acousto-optic interaction medium within a preset deflection angle range by controlling an acoustic wave frequency applied by the acoustic wave generator as a sensing light beam of a scan detection range by a plurality of different preset deflection angles, and an emission energy adjustment unit configured to correspondingly adjust an energy of the sensing light beam by changing an acoustic wave power applied by the acoustic wave generator. The application also provides a photoelectric detection device comprising the emission module and electronic equipment.
Description
Technical Field
The application belongs to the field of photoelectric detection, and particularly relates to an emission module, an emission device and related equipment for adjusting emission energy based on an acousto-optic effect.
Background
The ranging function of a lidar is generally based on the principle of Time of Flight (ToF) measurement, that is, by transmitting laser pulses to a measurement scene, measuring the Time of Flight of the laser pulses back and forth between the lidar and a target object to calculate three-dimensional information such as the distance of the target object. The ToF measurement has the advantages of long sensing distance, high precision, low energy consumption and the like, and is widely applied to the fields of consumer electronics, intelligent driving, AR/VR and the like.
In order to increase the detection distance and enlarge the angle of view, the laser radar needs to increase the power of the emitted laser pulse; in order to eliminate interference between the ambient light and the multiple radars to ensure signal-to-noise ratio and ranging accuracy, the lidar also needs to increase the number of laser pulses emitted by a single ranging to statistically eliminate noise. However, the high peak power, multiple frequency and wider pulse width of the laser pulses all mean higher laser radiation energy, which creates a challenge for the lidar to meet the safety standards of the human eye.
Disclosure of Invention
In view of the above, the present application provides a transmitting module, a device and related equipment for adjusting transmitting energy based on acousto-optic effect, which can improve the problems of the prior art.
In a first aspect, the present application provides an emitting module based on acousto-optic effect, which is configured to emit a sensing beam for three-dimensional information detection based on a time-of-flight principle to a detection range, comprising:
A light source module configured to emit a light beam;
At least one acousto-optic deflection module comprising an acousto-optic interaction medium and an acoustic wave generator configured to generate an acoustic wave propagating in a preset direction within the acousto-optic interaction medium; and
A control module including an acousto-optic deflection control unit configured to deflect a light beam passing through the acousto-optic interaction medium within a preset deflection angle range by controlling an acoustic wave frequency applied by the acoustic wave generator as a sensing light beam scanning the detection range by a plurality of different preset deflection angles, and an emission energy adjustment unit configured to correspondingly adjust an energy of the sensing light beam by changing an acoustic wave power applied by the acoustic wave generator.
In a second aspect, the present application provides a photodetection device configured to perform distance detection of an object located within a preset detection range. The photoelectric detection device comprises a receiving module, a processing module and the transmitting module. The receiving module is configured to sense the light signals from the detection range and output corresponding light sensing signals, and the processing module is configured to analyze and process the light sensing signals to obtain three-dimensional information of the object in the detection range.
In a third aspect, the present application provides an electronic device, including an application module and a photodetection device as described above. The application module is configured to realize corresponding functions according to the detection result of the photoelectric detection device.
The application has the beneficial effects that:
According to the application, the emission energy of the sensing light beam is adjusted by changing the sound wave power applied to the acousto-optic deflection module, so that a plurality of different sound wave power value adjusting intervals can be selected for adjustment, the flexibility is higher, and the sensitivity of the emission energy adjustment can be improved.
Drawings
The features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.
Fig. 1 is a schematic diagram of a functional module of an electronic device according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a functional module of an embodiment of the photodetection device shown in FIG. 1;
FIG. 3 is a schematic diagram of a statistical histogram obtained by the processing module shown in FIG. 2;
FIG. 4 is a signal timing diagram of the photo-detection device according to an embodiment of the present application;
FIG. 5 is a schematic view of an optical path of an embodiment of the transmitting module shown in FIG. 2;
FIG. 6 is a schematic structural diagram of the acousto-optic deflection module shown in FIG. 2;
FIG. 7 is a schematic view of an optical path of another embodiment of the transmitting module shown in FIG. 2;
Fig. 8 is a schematic structural diagram of a photoelectric detection device as an automotive laser radar according to an embodiment of the present application.
Detailed Description
Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the application. In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or as implicitly indicating the number or order of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more of the described feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the description of the present application, it should be noted that, unless explicitly specified or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically connected, electrically connected or communicated with each other; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements or interaction relationship between the two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
The following disclosure provides many different embodiments, or examples, for implementing different structures of the application. In order to simplify the present disclosure, only the components and arrangements of specific examples will be described below. They are, of course, merely examples and are not intended to limit the application. Furthermore, the present application may repeat use of reference numerals and/or letters in the various examples, and is intended to be simplified and clear illustration of the present application, without itself being indicative of the particular relationships between the various embodiments and/or configurations discussed. In addition, the various specific processes and materials provided in the following description of the present application are merely examples of implementation of the technical solutions of the present application, but those of ordinary skill in the art should recognize that the technical solutions of the present application may also be implemented by other processes and/or other materials not described below.
Further, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the application. It will be appreciated, however, by one skilled in the art that the inventive aspects may be practiced without one or more of the specific details, or with other structures, components, etc. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the application.
An embodiment of the present application provides an emission module based on an acousto-optic effect, which is characterized by being configured to emit a sensing beam for three-dimensional information detection based on a time-of-flight principle to a detection range, including:
A light source module configured to emit a light beam;
At least one acousto-optic deflection module comprising an acousto-optic interaction medium and an acoustic wave generator configured to generate an acoustic wave propagating in a preset direction within the acousto-optic interaction medium; and
A control module including an acousto-optic deflection control unit configured to deflect a light beam passing through the acousto-optic interaction medium within a preset deflection angle range by controlling an acoustic wave frequency applied by the acoustic wave generator as a sensing light beam scanning the detection range by a plurality of different preset deflection angles, and an emission energy adjustment unit configured to correspondingly adjust an energy of the sensing light beam by changing an acoustic wave power applied by the acoustic wave generator.
Optionally, in some embodiments, the sensing beam is first order diffracted light of a beam diffracted by the acousto-optic interaction medium.
Optionally, in some embodiments, the energy value of the sensing beam is a periodically functionally varying relationship with the corresponding acoustic power value.
Optionally, in some embodiments, the emission energy adjustment unit is configured to correspondingly adjust the emission energy of the sensing light beam by changing the light emitting power of the light source module at the same time.
Optionally, in some embodiments, the two separate acousto-optic deflection modules are respectively a first acousto-optic deflection module and a second acousto-optic deflection module, the first acousto-optic deflection module is configured to deflect the passing light beam along a first direction by a plurality of different preset deflection angles within a preset deflection angle range, the second acousto-optic deflection module is configured to deflect the passing light beam along a second direction different from the first direction by a plurality of different preset deflection angles within the preset deflection angle range, the light beams emitted by the light source module form sensing light beams which two-dimensionally scan a detection range after being deflected by the first acousto-optic deflection module and the second acousto-optic deflection module respectively, and the emission energy adjustment unit adjusts energy of the sensing light beams by controlling acoustic power applied on at least one of the acousto-optic deflection modules.
Optionally, in some embodiments, the system further includes an electro-optical deflection module configured to deflect the passing light beam in a first direction by a plurality of different preset deflection angles within a preset deflection angle range, the electro-optical deflection module is configured to deflect the passing light beam in a second direction different from the first direction by a plurality of different preset deflection angles within the preset deflection angle range according to an applied electric field intensity, and the light beam emitted by the light source module forms a sensing light beam for performing two-dimensional scanning on a detection range after being deflected by the acousto-optical deflection module and the electro-optical deflection module, and the control module adjusts energy of the sensing light beam by controlling acoustic power applied on the acousto-optical deflection module.
Optionally, in some embodiments, the light source module further comprises beam shrinking optics configured to shrink the strip collimated light beam to a predetermined size before transmitting to the acousto-optic deflection module.
Optionally, in some embodiments, the first direction is a horizontal direction and the second direction is a vertical direction; or the first direction is a vertical direction, and the second direction is a horizontal direction.
The embodiment of the application also provides a photoelectric detection device which is configured to detect three-dimensional information of an object positioned in a preset detection range, and comprises the transmitting module, the receiving module and the processing module. The photoelectric detection device further comprises a receiving module and a processing module, wherein the receiving module is configured to sense optical signals from the detection range and output corresponding light sensing signals, and the processing module is configured to analyze and process the light sensing signals to obtain three-dimensional information of an object in the detection range.
Optionally, in some embodiments, in a same zone detection period in which a zone of the detection range along a preset scan angle is detected, the emission energy adjustment unit adjusts the first sensing beam pulses emitted first in the zone detection period to have lower first emission energy by changing the acoustic power applied to at least one of the acousto-optic deflection modules, and then changes the acoustic power applied to at least one of the acousto-optic deflection modules according to the analysis of the echo of the first sensing beam pulses by the processing module, so as to adjust the emission energy of the second sensing beam pulses emitted after the zone detection period.
Optionally, in some embodiments, if the analysis of the first sensing beam pulse echo shows that there is no object within a preset maximum safe distance, the emission energy adjustment unit adjusts the plurality of second sensing beam pulses emitted after the subarea detection period to have higher second emission energy by changing the acoustic wave power applied on at least one of the acousto-optic deflection modules, and the processing module obtains the sensing result of the current subarea detection period according to the analysis of the second sensing beam pulse echo after the second sensing beam pulse is emitted.
Optionally, in some embodiments, the second emission energy is equal to or greater than a highest emission energy required for sensing a furthest value of the distance that the beam pulse needs to satisfy along the current scan angle; or the second emission energy is less than the highest emission energy, while a suitable emission energy is determined from object distance information obtained from an analysis of the first sensing beam pulse echo.
Optionally, in some embodiments, if the analysis of the first sensing beam pulse echo shows that there is an object within a preset maximum safe distance, the transmitting module stops transmitting the sensing beam pulse, and the processing module directly outputs the analysis result of the first sensing beam pulse echo as the sensing result of the current zone detection period.
Optionally, in some embodiments, if the analysis of the first sensing beam pulse echo shows that there is an object within a preset maximum safe distance, the emission energy adjustment unit may maintain the acoustic power applied on the acousto-optic deflection module, so that the plurality of second sensing beam pulses emitted after the zone detection period still have the lower first emission energy, and after the second sensing beam pulse is emitted, the processing module obtains the sensing result of the current zone detection period according to the analysis of the first sensing beam pulse echo and the second sensing beam pulse echo.
Optionally, in some embodiments, if the analysis of the first sensing beam pulse echo shows that there is an object within a preset maximum safe distance, the emission energy adjustment unit adjusts the plurality of second sensing beam pulses emitted after the same segment detection period to have a third emission energy by changing the acoustic power applied to at least one of the acousto-optic deflection modules, the third emission energy having a positive correlation with the object distance obtained by the processing module for the first sensing beam pulse echo analysis, and not exceeding a relevant safe criterion to be satisfied at the object distance at most.
Optionally, in some embodiments, the emission energy adjustment unit is configured to detect the maximum emission energy required for the furthest value by changing the acoustic power applied on at least one of the acousto-optic deflection modules to emit a plurality of second sensing beam pulses having a second emission energy equal to or greater than the distance that the sensing beam pulses need to satisfy along the current scan angle if the speed of movement of the photo-detection device exceeds a preset speed threshold.
The embodiment of the application also provides electronic equipment, which comprises the photoelectric detection device. The electronic equipment realizes corresponding functions according to the three-dimensional information obtained by the photoelectric detection device. The electronic device is, for example: cell phones, automobiles, robots, access control/monitoring systems, intelligent door locks, unmanned vehicles, unmanned aerial vehicles, and the like. The three-dimensional information is, for example: proximity information, depth information, distance information, coordinate information, and the like of an object within the detection range. The three-dimensional information may be used in fields such as 3D modeling, identity recognition, autopilot, machine vision, monitoring, unmanned aerial vehicle control, augmented Reality (Augmented Reality, AR)/Virtual Reality (VR), instant location and map building (Simultaneous Localization AND MAPPING, SLAM), object proximity determination, etc., which are not limited in this application.
The photoelectric detection device can be, for example, a laser radar and can be used for obtaining three-dimensional information of an object in a detection range. The laser radar is applied to the fields of intelligent driving vehicles, intelligent driving aircrafts, 3D printing, VR, AR, service robots and the like. Taking an intelligent driving vehicle as an example, a laser radar is arranged in the intelligent driving vehicle, and the laser radar can scan the surrounding environment by rapidly and repeatedly emitting laser beams so as to obtain point cloud data reflecting the morphology, the position and the movement condition of one or more objects in the surrounding environment. Specifically, the lidar emits a laser beam to the surrounding environment, receives an echo beam of the laser beam reflected by each object in the surrounding environment, and determines distance/depth information of each object by calculating a time delay (i.e., time of flight) between the emission time of the laser beam and the return time of the echo beam. Meanwhile, the laser radar can also determine angle information describing the orientation of the detection range of the laser beam, combine the distance/depth information of each object with the angle information of the laser beam to generate a three-dimensional map comprising each object in the scanned surrounding environment, and guide the intelligent driving of the unmanned vehicle by using the three-dimensional map.
Hereinafter, an embodiment of a photodetection device applied to an electronic apparatus will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic diagram of a functional module of a photodetection device applied to an electronic device according to an embodiment of the present application. Fig. 2 is a schematic diagram of a functional module of a photodetection device according to an embodiment of the present application.
Referring to fig. 1 and 2, the electronic device 1 comprises a photo detection means 10. The photodetection device 10 can detect the object 2 within a detection range to obtain three-dimensional information of the object 2, where the detection range may be defined as a three-dimensional space range in which the photodetection device 10 can effectively detect three-dimensional information, and may also be referred to as a viewing angle or a viewing field range of the photodetection device 10. Such as, but not limited to, one or more of proximity information of the object 2, depth information of the surface of the object 2, distance information of the object 2, and spatial coordinate information of the object 2.
The electronic device 1 may include an application module 20, where the application module 20 is configured to perform a preset operation or implement a corresponding function according to a detection result of the photodetection device 10, for example, but not limited to: whether the object 2 appears in a detection range preset in front of the electronic equipment 1 can be judged according to the proximity information of the object 2; or the movement of the electronic equipment 1 can be controlled to avoid the obstacle according to the distance information of the object 2; or 3D modeling, identification, machine vision, etc. may be implemented according to depth information of the surface of the object 2. That is, the application module 20 may be a collection of software that includes hardware required to perform the operations and implement the functions described above and control coordination of the hardware operations.
The electronic device 1 may further comprise a storage medium 30, which storage medium 30 may provide support for the storage requirements of the electronic device 1 and/or the photo detection means 10 during operation. As shown in fig. 1, in some embodiments, the storage medium 30 may be disposed inside the electronic device 1. As shown in fig. 2, in some embodiments, the storage medium 30 may also be disposed inside the photodetection device 10.
The electronic device 1 may further comprise a processor 40 which may provide support for data processing requirements of the electronic device 1 and/or the photo detection means 10 during operation. As shown in fig. 1, in some embodiments, the processor 40 may be disposed internal to the electronic device 1. As shown in fig. 2, in some embodiments, the processor 40 may also be disposed within the photodetection device 10.
Alternatively, in some embodiments, the photodetection device 10 may be, for example, a dToF measurement device that performs three-dimensional information sensing based on the direct time of Flight (DIRECT TIME of Flight, dToF) principle. The dToF measuring device can emit the sensing light beam in the detection range and receive the sensing light beam reflected by the object 2 in the detection range, the time difference between the emitting time and the receiving time of the reflected sensing light beam is called as the flight time t of the sensing light beam, and the three-dimensional information of the object 2 can be obtained by calculating half the passing distance of the sensing light beam in the flight time tWherein c is the speed of light.
In other embodiments, the photodetector 10 may also be a iToF measurement device that senses three-dimensional information using an indirect time-of-Flight (INDIRECT TIME of Flight, iToF) measurement principle. The iToF measuring device obtains three-dimensional information of the object 2 by comparing the phase difference of the sensing beam as it is transmitted with that of the sensing beam as it is received back after reflection.
In the following embodiments of the present application, the photodetection device 10 is mainly described as a dToF measuring device.
In some embodiments, as shown in fig. 2, the photodetection device 10 includes a transmitting module 12, a receiving module 14, and a processing module 15. The transmitting module 12 is configured to transmit a sensing beam to the detection range to detect three-dimensional information of the object 2 within the detection range, wherein a part of the sensing beam is reflected by the object 2 and returns, and the reflected sensing beam echo carries the three-dimensional information of the object 2, and a part of the sensing beam echo can be sensed by the receiving module 14 to obtain the three-dimensional information of the object 2. The receiving module 14 is configured to sense the optical signal from the detection range and output a corresponding optical sensing signal, and the three-dimensional information detection of the object 2 in the detection range is realized by analyzing the optical sensing signal. It is understood that the optical signal sensed by the receiving module 14 may be a photon, for example, a photon including a sensing beam echo reflected by the object 2 in the detection range and a photon of ambient light in the detection range. The processing module 15 is configured to analyze and process the photo-sensing signal to obtain a time instant at which the echo of the sensing beam is sensed by the receiving module 14, and to obtain three-dimensional information of the object 2 according to a time difference between the emission time instant and the reflection time instant of the sensing beam.
The processing module 15 may be provided on the photo detection device 10. It will be appreciated that in other embodiments, all or part of the functional units of the processing module 15 may also be provided on the electronic device 1.
In some embodiments, the sensing beam may be, for example, a plurality of laser pulses that are sequentially emitted. The emission module 12 is configured to emit the laser pulses as a sensing beam according to a predetermined time sequence. Specifically, the transmitting module 12 transmits the sensing beam pulses to the subareas with different directions in the detection range in a time-sharing manner according to a preset scanning manner to perform distance detection, and transmits a plurality of sensing beam pulses to each subarea according to a corresponding preset time sequence, so that the distance information of one subarea can be correspondingly obtained after the transmission of the plurality of sensing beam pulses to one subarea is completed. That is, one frame detection of the detection range includes a plurality of partition detection periods corresponding to the partition scanning.
Alternatively, the sensing beam is, for example, visible light, infrared light, or near infrared light, with wavelengths ranging, for example, from 390 nanometers (nm) to 780nm, from 700nm to 1400nm, from 800nm to 1000nm, from 900nm to 1600nm, and the like.
Referring to fig. 2,3 and 4 together, fig. 3 is a schematic diagram of a statistical histogram obtained by the processing module 15 shown in fig. 2. In some embodiments, the processing module 15 may include a timing unit 152, a statistics unit 154, a time-of-flight acquisition unit 156, and a three-dimensional information acquisition unit 158.
The timing unit 152 is configured to determine a time of receipt of the optical signal sensed by the receiving module 14. The photoelectric detection device 10 sends out a plurality of sensing light beams through the transmitting module 12 in the detection process, the timing unit 152 starts timing when the transmitting module 12 transmits the sensing light beams each time so as to record the receiving time of the optical signals sensed by the receiving module 14 between two adjacent sensing light beam transmissions, during which the receiving module 14 outputs corresponding light sensing signals each time when receiving one optical signal, and the timing unit 152 records the receiving time of the sensed optical signals according to the light sensing signals output by the receiving module 14 and counts in time bins corresponding to the receiving time so as to form corresponding optical signal counts. The time bin is the minimum time unit Δt for the timing unit 152 to record the time of the generation of the photo-sensing signal, and can reflect the accuracy of time recording of the receiving time of the photo-sensing signal by the timing unit 152, and the finer the time bin, the higher the accuracy of time recording. In some embodiments, the timing unit 152 may implement a timing function, for example, through a Time-to-Digital Converter, TDC) 1522. The TDC1522 may be connected to the corresponding photo-sensing pixel 142 on the receiving module 14, and configured to record the receiving time of the sensed optical signal according to the photo-sensing signal generated by the corresponding photo-sensing pixel 142. For example, the TDC1522 is synchronously triggered to start timing each time the sensing beam is emitted, and then stops timing in response to the photo-sensing signal generated by the corresponding photo-sensing pixel 142, and takes the counted time period as the receiving time of the corresponding photo-signal that excites the photo-sensing signal.
In some embodiments, the timing unit 152 may include a count memory 1524, where the count memory 1524 has a count memory space allocated correspondingly according to time bins, and each time the TDC1522 records a receiving time of an optical signal is added one in the count memory space corresponding to time bins, that is, the count of the optical signal in the corresponding time bin is increased by one, and the count value of the optical signal in each time bin corresponds to the number of times the optical signal is received at the time represented by the time bin in multiple emission periods of the sensing beam.
The statistics unit 154 is configured to count the optical signal counts accumulated in each time bin, so as to obtain a statistical histogram that can reflect the distribution of the number of optical signals accumulated and sensed by the receiving module 14 over the course of multiple sensing beam emissions. As shown in fig. 3, the abscissa of the statistical histogram represents the time stamp of each corresponding time bin, and the ordinate of the statistical histogram represents the light signal count value accumulated in each corresponding time bin. In some embodiments, the statistics unit 154 may include a histogram circuit 1544 (see fig. 2), the histogram circuit 1544 configured to count the light signal counts within each time bin to generate a statistical histogram. It should be understood that the statistics unit 154 performs a statistical analysis on the counts of the optical signals corresponding to the counts accumulated during the process of emitting the sensing light beams multiple times in one segment detection period, so that the counts have a mathematical statistical significance, and the number of the emissions of the sensing light beams in one segment detection period may be up to hundreds, thousands, tens of thousands, or even millions.
During the sensing process, a large number of photons of ambient light are also sensed by the receiving module 14 to generate corresponding counts of the optical signals. The probability that photons of these ambient light are sensed leaving counts in each time bin tends to be the same, constituting Noise floors (Noise levels) within the detection range, which are measured relatively high in scenes where the ambient light is strong and relatively low in scenes where the ambient light is weak. On this basis, the sensing beam echo reflected from the object 2 is sensed and the corresponding generated optical signal count is superimposed on the noise back, so that the optical signal count in the time bin corresponding to the sensing time of the sensing beam echo is obviously higher than the optical signal count of other time bins, and further, a prominent signal peak is formed. It will be appreciated that the count value of the signal peak may be affected by factors such as the optical power of the sensing beam, the reflectivity of the object 2, the detection range of the photodetection device 10, and the like, and the width of the signal peak may be affected by factors such as the pulse width of the emitted sensing beam, the time jitter of the photoelectric conversion element of the receiving module 14 and the TDC1522, and the like. Thus, the time-of-flight acquisition unit 156 can obtain the time-of-flight of the relevant sensing beam reflected back by the object 2 from the time difference between the time stamp t1 of the time bin corresponding to the peak value of the signal peak and the emission time t0 of the relevant sensing beam generating the signal peak. The three-dimensional information acquisition unit 158 may be configured to obtain three-dimensional information between the object 2 reflecting the sensing light beam and the photodetection device 10 from the time of flight of the sensing light beam determined by the statistical histogram, for example: the distance between the object 2 and said photo detection means 10 in the detection range.
It should be understood that the transmitting module 12 and the receiving module 14 are disposed adjacent to each other side by side, the light emitting surface of the transmitting module 12 and the light entering surface of the receiving module 14 face the same side of the photodetecting device 10, and the distance between the transmitting module 12 and the receiving module 14 may be, for example, 2 millimeters (mm) to 20mm. Because the transmitting module 12 and the receiving module 14 are relatively close to each other, the transmitting path of the sensing beam from the transmitting module 12 to the object 2 and the returning path from the object 2 to the receiving module 14 after reflection are not completely equal, but are far greater than the distance between the transmitting module 12 and the receiving module 14, which can be regarded as approximately equal. Thereby, the distance between the object 2 and the photo detection means 10 can be calculated from the product of half the time of flight t of the sensing beam reflected back by the object 2 and the speed of light c.
In some embodiments, as shown in fig. 2, the receiving module 14 may include a photosensor 140 and receiving optics 144. The receiving optics 144 is disposed on the light-in side of the photosensor 140 and is configured to propagate an optical signal from a detection range to the photosensor 140 for sensing. For example, the receiving optics 144 may include a receiving lens (not shown). Alternatively, the receiving lens may include one lens or a plurality of lenses. The photosensor 140 is configured to sense optical signals propagating from the detection range via the receiving optics 144 and output corresponding photo-sensing signals.
In some embodiments, the receiving module 14 may further include a peripheral circuit (not shown) formed by one or more of a signal amplifier, an Analog-to-Digital Converter (ADC), and the like, and the peripheral circuit may be partially or fully integrated in the photosensor 140.
Alternatively, the photosensor 140 may include a single photosensitive pixel 142 or include a plurality of photosensitive pixels 142 to form a photosensitive pixel array. The detection range of the photodetection device 10 may include a plurality of partitions respectively located at different positions, the photosensitive pixels 142 of the photosensor 140 have corresponding partitions in the detection range, and the optical signals returned from the partitions propagate to the corresponding photosensitive pixels 142 via the receiving optical device 144 for sensing. That is, the partition corresponding to the photosensitive pixel 142 can be regarded as a spatial range covered by the angle of view of the photosensitive pixel 142 formed by the receiving optical device 144. Thus, when the sensing beam emitted by the emitting module 12 scans the area and there is an object 2 on the area, the sensing beam echo reflected by the object 2 propagates to the corresponding photosensitive pixel 142 for sensing through the receiving optical device 144. That is, the optical signal returned from the zone comprises photons of ambient light from the zone, and also comprises a sensing beam echo projected onto the zone and reflected back by the object 2 when the object 2 is present in the zone.
One of the photosensitive pixels 142 may include a single photoelectric conversion device or include a plurality of photoelectric conversion devices. The photoelectric conversion device is configured to sense a received optical signal and convert the received optical signal into a corresponding electrical signal to be output as the photo-sensing signal. Optionally, the photoelectric conversion device is, for example, a single photon avalanche diode (Single Photon Avalanche Diode, SPAD), an avalanche photodiode (AVALANCHE PHOTON DIODE, APD), a silicon photomultiplier (Silicon Photomultiplier, siPM) provided in parallel by a plurality of SPADs, and/or other suitable photoelectric conversion elements.
As shown in fig. 2, the emission module 12 includes a light source module 122 and at least one acousto-optic deflection module 124. The light source module 122 is configured to emit a light beam, and the acousto-optic deflection module 124 is configured to deflect the light beam emitted by the light source module 122 by a plurality of different preset deflection angles within a preset deflection angle range according to the applied acoustic wave frequency. Thus, the angle of deflection of the beam by the acousto-optic deflection module 124 can be controlled by adjusting the frequency of the applied acoustic wave.
In some embodiments, the transmit module 12 may also include at least one secondary deflection module 126. The secondary deflection module 126 is configured to further deflect the light beam deflected by the acousto-optic deflection module 124 by a preset angle within a preset deflection angle range.
It should be appreciated that in some embodiments, the secondary deflection module 126 may deflect the light beam using an acousto-optic effect as the acousto-optic deflection module 126; in other embodiments, the secondary deflection module 126 may also deflect the light beam in other ways, such as: the secondary deflection module 126 may be an electro-optic deflector, a liquid crystal polarization grating, a lens or group of lenses, a superlens, or the like.
It should be appreciated that in some embodiments, the number of secondary deflection modules 126 may be two or more to expand the deflection angle range of the sensing beam emitted by the entire emission module 12 by deflecting multiple times.
It should be appreciated that in some embodiments, the direction in which the secondary deflection module 126 deflects the light beam may be different from the direction in which the acousto-optic deflection module 124 deflects the light beam, thereby enabling two-dimensional deflection of the sensing light beam. For example: the acousto-optic deflection module 124 deflects the passing light beam in a horizontal direction and the secondary deflection module 126 deflects the passing light beam in a vertical direction. The direction of the deflected light beam is here different from the emission direction of the light beam, which is understood to be the direction in which the trend changes when the emission direction of the light beam is changed.
The acousto-optic deflection module 124 can deflect the passing light beam with high precision, but the angle range of the deflected light beam is too small, so that the requirement of high-angle and high-precision scanning can be met by further deflecting the light beam deflected by the acousto-optic deflection module 124 by arranging one or more secondary deflection modules 126 on the light emitting side of the acousto-optic deflection module 124, and the two-dimensional deflection of the sensing light beam can be realized.
Referring to fig. 4, the light source module 122 includes one or more light emitting units 1220, and the light emitting units 1220 are configured to emit light beams. The light emitting unit 1220 may be a light emitting structure in the form of a vertical cavity Surface emitting Laser (VERTICAL CAVITY Surface EMITTING LASER, abbreviated as VCSEL, or may be translated into a vertical cavity Surface emitting Laser), a side emitting Laser (EDGE EMITTING LASER, EEL), a light emitting Diode (LIGHT EMITTING Diode, LED), a Laser Diode (LD), a fiber Laser, or the like. The edge emitting laser may be a Fabry Perot (FP) laser, a distributed feedback (Distribute Feedback, DFB) laser, an Electro-absorption modulated laser (Electro-absorption Modulated, EML), or the like, which is not limited in the embodiment of the present application. In some embodiments, the light source module 122 may employ a collimating optical device 1222 such as a superlens or a cylindrical lens to collimate the light beam emitted from the light emitting unit 1220, so as to improve the collimation of the light beam emitted from the light source module 122.
In some embodiments, the light source module 122 may further include beam shrinking optics 1223 that may be used to narrow the cross-sectional dimension of the light beam, i.e., the dimension of the light beam in a cross-section perpendicular to the direction of light beam propagation. The beam shrinking optics 1223 may be disposed in the optical path before the light beam enters the acousto-optic deflection module 124, and configured to shrink the light beam emitted by the light source module 122 to a preset size before transmitting the light beam to the acousto-optic deflection module 124. Since the incident area of the acousto-optic deflection module 124 for receiving the light beam has a certain size, in order to allow the light beam incident on the acousto-optic deflection module 124 to enter from the incident area, it is necessary to modulate the light beam to a size matching the incident area before transmitting to the acousto-optic deflection module 124. It should be understood that in other embodiments, the beam shrinking optics 1223 may be omitted if the collimated beam emitted by the light source module 122 has a size that meets the requirements of the incident acousto-optic deflection module 124.
In some embodiments, the light source module 122 may further include a linear polarizer 1221. The linear polarizer 1221 is disposed on the optical path of the light beam before entering the acousto-optic deflection module 124, and is configured to convert the light beam into linearly polarized light having a predetermined polarization state before entering the acousto-optic deflection module 124. It should be understood that in other embodiments, the linear polarizer 1221 may be omitted if other optical elements can convert the light beam to linearly polarized light in a predetermined deflection state before the light beam is transmitted to the acousto-optic deflection module 124.
In the embodiment of fig. 4, the beam reduction optics 1223 are disposed between the light emitting unit 1220 and the linear polarizer 1221. It should be understood that in other embodiments, the arrangement order of the beam shrinking optics 1223 and the linear polarizer on the optical path may be interchanged, so long as both are disposed in the optical path before the light beam enters the acousto-optic deflection module 124, which is not particularly limited by the present application.
As shown in fig. 5, in some embodiments, the acousto-optic deflection module 124 includes an acousto-optic interaction medium 1241 and an acoustic wave generator 1242. The acousto-optic interaction medium 1241 has a predetermined light incident surface 1244, a predetermined light emergent surface 1246 and a predetermined sound wave incident surface 1248. The sound wave generator 1242 is disposed on the sound wave incident surface 1248 and configured to generate sound waves propagating in a predetermined direction in the acousto-optic interaction medium 1241. The light beam emitted by the light source module 122 enters the acousto-optic interaction medium 1241 from the light incident surface 1244 along a preset incident angle, the acousto-optic interaction medium 1241 deflects the propagation direction of the light beam under the action of the sound wave, and the deflected light beam is emitted from the light emergent surface 1246.
The incident angle may be defined as an angle between an incident direction of the light beam and a normal direction of the light incident surface 1244. In some embodiments, the material of the acousto-optic interaction medium 1241 is tellurium dioxide (TeO 2), the range of the incident angle is 2-10 degrees, and the preset off-axis angle θ α exists between the propagation direction of the sound wave in the tellurium dioxide crystal and the lattice direction [1, 0] of the tellurium dioxide crystal (not shown).
In some embodiments, the acoustic wave generator 1242 may be a piezoelectric transducer that generates ultrasonic waves to propagate into the acousto-optic interaction medium 1241 to deflect the propagation direction of the light beam passing through the acousto-optic interaction medium 1241 at a preset angle of incidence.
It should be understood that, the propagation of the acoustic wave in the acousto-optic interaction medium 1241 may cause the refractive index inside the acousto-optic interaction medium 1241 to change, by reasonably configuring parameters, the incident beam may cause abnormal bragg diffraction in the acousto-optic interaction medium 1241 under the action of the acoustic wave, the propagation direction of the formed diffracted beam is deflected compared with the propagation direction of the incident beam, and the deflection angle α is related to the frequency f of the acoustic wave by formula (1):
Wherein θ d is the exit angle of the diffracted beam, representing the propagation direction of the diffracted beam, θ i is the incident angle of the incident beam, representing the propagation direction of the incident beam, λ is the wavelengths of the incident beam and the diffracted beam, n is the refractive index of the acousto-optic interaction medium 1241, V is the function value associated with the off-axis angle θ α, denoted as v=v (θ a), and the above reasonably configured parameters include the wavelength, polarization state, incident angle, propagation direction, frequency of the acoustic wave, propagation direction, and the like of the incident beam. Thus, by varying the frequency of the sound wave applied to the acousto-optic interaction medium 1241, the deflection angle of the light beam passing through the acousto-optic interaction medium 1241 can be controlled, and when the frequency of the sound wave is changed to Δf, the deflection angle of the light beam is correspondingly changed, i.e. the scan angle is
The deflection angle α and the scan angle Δα refer to angles inside the acousto-optic interaction medium 1241, and in practical applications, angles outside the acousto-optic interaction medium 1241 are used, and it is known from the law of refraction that the angles outside the acousto-optic interaction medium 1241 need to be multiplied by corresponding refractive index factors. Furthermore, since the time required for the propagation of the acoustic wave, when the frequency of the acoustic wave is just changed from f1 to f2, the acousto-optic interaction medium 1241 is changed from f1 to f2 only in the part next to the acoustic wave generator 1242, the deflection angle of the light beam is changed from α1 to α2, the deflection time required for the light beam to complete one deflection is considered to be equal to the transit time of the acoustic wave when the acoustic wave propagates through the entire region where the light beam passes in the acousto-optic interaction medium 1241, that is, the width of the acousto-optic interaction medium 1241, the time required is called the transit time, the acoustic wave frequency in the entire acousto-optic interaction medium 1241 is changed from f1 to f2 after the transit time passes, and the deflection angle of the light beam is completely changed to α2 when the acoustic wave frequency is adjusted to change the deflection angle of the light beam, the deflection time required for the light beam to complete one deflection can be considered to be equal to the transit time of the acoustic wave, and the calculation of the deflection time τ satisfies the following relation (2):
Where W is the aperture of the incident aperture of the light beam on the acousto-optic interaction medium 1241, that is, the width of the light beam incident on the acousto-optic interaction medium 1241 is also generally equal to the width of the acousto-optic interaction medium 1241, and V is a function value related to the off-axis angle θ α, denoted as v=v (θ a).
The diffracted beam in the acousto-optic interaction medium 1241, the incident beam and the wave vector of the acoustic wave need to satisfy the momentum matching condition to form a stable coherent diffracted beam in the acousto-optic interaction medium 1241, the incident angle of the beam generating abnormal bragg diffraction will change along with the change of the acoustic wave frequency, however, in practical application, the incident angle of the beam of the acousto-optic interaction medium 1241 remains unchanged, the momentum matching condition is no longer satisfied along with the change of the acoustic wave frequency, the farther the momentum matching condition is deviated, the more the diffraction efficiency is reduced, and the acoustic wave frequency range capable of effectively completing abnormal bragg diffraction is called as the bragg bandwidth. In some embodiments, the wavelength of the sensing beam is 905nm, the material of the acousto-optic interaction medium 1241 is tellurium dioxide crystal, the bragg bandwidth of the corresponding acousto-optic deflection module 124 is about 30 megahertz (MHz), the scanning angle is about 40 milliradians (mrad), that is, about 2.3 degrees, the deflection time τ required for completing one beam deflection is about 10 microseconds (μs), the accuracy of the change of the acoustic wave frequency is about 30 kilohertz (KHz), and the accuracy of the change of the corresponding scanning angle is about 0.04mrad. Realizing acousto-optic deflection in tellurium dioxide crystal by utilizing anomalous Bragg diffraction requires that the incident light beam has a dextrorotation e light component, alternatively, if the incident light beam is linear polarization e light, the diffracted light beam emitted after the acousto-optic deflection is linear polarization o light; if the incident light beam is right circularly polarized light, the diffracted light beam emitted after acousto-optic deflection is left circularly polarized light. The utilization of the outgoing diffracted beam is determined by the ellipticity of the eigenmode dextrorotatory e-light of the incident beam, which is determined by the wavelength of the incident light, the angle of incidence and the material properties of the acousto-optic interaction medium 1241.
As shown in fig. 2, the photodetection device 10 further includes a control module 18, where the control module 18 is configured to control the transmitting module 12 to emit a sensing beam to scan the detection range, and control the receiving module 14 to sense a beam returned from the detection range in coordination with the scanning of the sensing beam.
In some embodiments, the control module 18 may include a light source control unit 182, an acousto-optic deflection control unit 184, and a sensing control unit 186.
The light source control unit 182 is configured to control the light source module 122 to emit sensing beam pulses according to a preset time sequence. As described above, in order to make dToF the time-dependent single photon counting method used for measurement have a mathematical statistical significance, the light source control unit 182 controls the corresponding light source module 122 to emit a plurality of sensing beam pulses according to a preset time sequence within one partitioned detection period, for example: tens, hundreds, thousands, tens of thousands, or even millions of sensing beam pulses are emitted corresponding to one sensing period, i.e., one divisional detection period includes a plurality of sensing periods.
It should be appreciated that the duration of the sensing period may be set according to the distance detection furthest value that the detected partition needs to satisfy, at least greater than the photon flight time corresponding to the distance detection furthest value. The plurality of different sensing periods that belong to one partition detection period may be set to have the same duration.
It should be appreciated that in some embodiments, for a plurality of different sensing periods, corresponding sensing beam pulses may be emitted at the same instant in time of the sensing period, for example: are all transmitted at the beginning of the sensing period; in other embodiments, the corresponding sensing beam pulses may be emitted at different times during the sensing period for a plurality of different sensing periods, which may belong to one or different sub-area detection periods, to prevent interference between different photo-detection devices 10 or reduce crosstalk between adjacent photo-sensitive pixels on the receiving module.
It should be understood that in some embodiments, the length of the sensing period when scanning the partitions located in different angular orientations within the detection range may be different, for example: the length of the sensing time period in the partition detection time period and the distance detection furthest value which needs to be met by the corresponding detection area form a positive correlation relation, and the sensing time period for implementing corresponding sensing is longer for the detection area with larger distance detection furthest value; for a detection region where the distance detection furthest value is smaller, the sensing period for performing the corresponding sensing is shorter.
The sensing control unit 186 is configured to control the associated photosensitive pixels 142 to perform sensing for a corresponding sensing period in response to the light signal returned from the detection range for counting. It should be appreciated that in some embodiments, the sensing control unit 142 controls a portion of the photosensitive pixels 142 to operate in conjunction with the receiving optics 144 to correspondingly sense the light signal returned from the predetermined orientation, the associated photosensitive pixels 142 operating in relation to the scanning direction of the current sensing beam pulse. Thus, when the sensing beam pulse corresponds to the different direction of the scanning detection range in the different partition detection periods, the sensing control unit 142 correspondingly controls the different related photosensitive pixels 142 to perform the sensing operation.
It should be appreciated that in some embodiments, the light source control module 182 controls the light source module 122 to periodically emit sensing beam pulses at a preset frequency, and the sensing control unit 142 may control the associated photosensitive pixels 142 to periodically perform sensing at the same preset frequency as the sensing period. Alternatively, the timing at which the associated photosensitive pixel 142 starts to perform sensing and the timing of the emission of the corresponding sensing beam pulse may or may not be kept in synchronization within the same sensing period in which the emission and sensing correspond to each other.
The acousto-optic deflection control unit 184 is configured to control the acousto-optic deflection module 124 to deflect the passing light beam by a preset deflection angle within a corresponding deflection angle range. As previously described, the acousto-optic deflection control unit 184 can control the deflection angle of the passing beam by the acousto-optic deflection module 124 by adjusting the frequency of the acoustic wave applied to the acousto-optic interaction medium 1241. The acousto-optic deflection module 124 requires a deflection time τ of about 10 microseconds to change the primary beam deflection angle. It should be appreciated that for each beam deflection angle, the transmitting module 12 needs to transmit a plurality of sensing beam pulses to detect the distance information in the direction of illumination by the beam deflection angle. The number of sensing beam pulses emitted by the emitting module 12 along different beam deflection angles may be different, for example, the number of sensing beam pulses emitted along the direction may be set according to the distance detection furthest value that needs to be satisfied by the photoelectric detection device 10 in the direction irradiated by each beam deflection angle, and a sensing time period corresponding to the number of sensing beam pulses is set in the partition detection time period related to the beam deflection angle.
In use, the acousto-optic deflection control unit 184 controls the acousto-optic deflection module 124 to deflect the light beam with a preset acousto-optic deflection accuracy within a corresponding deflection angle range. The light source control unit 182 controls the light source module 122 to emit sensing light beam pulses according to a preset time sequence corresponding to each preset deflection angle of the light beam, and the sensing control unit 186 controls the associated photosensitive pixels 142 to sense the light signal returned from the direction corresponding to the deflection angle of the light beam to perform three-dimensional detection of the direction corresponding to the deflection angle of the light beam.
It should be appreciated that the acousto-optic deflection control unit 184 may include at least a drive circuit for the acoustic wave generator 1242 to control the frequency of the acoustic wave applied to the acousto-optic deflection module 124.
In some embodiments, the control module 18 may further include one or more secondary deflection control units 188 corresponding to the secondary deflection modules 126 in the emission module 12, configured to control the corresponding secondary deflection modules 126 to deflect the passing light beam by a preset deflection angle within the corresponding deflection angle range. It should be appreciated that the specific manner of control of the secondary deflection control unit 188 is related to the type of secondary deflection module 126 that is correspondingly controlled. For example: in the case where the secondary deflection module 126 is also an acousto-optic deflection module, the corresponding secondary deflection control unit 188 is similar to the acousto-optic deflection control unit 184, and controls the deflection angle of the secondary deflection module 126 to the passing beam by adjusting the frequency of the acoustic wave applied to the acousto-optic interaction medium 1241; in the case where the secondary deflection module 126 is a liquid crystal polarization grating, the corresponding secondary deflection control unit 188 controls the angle of deflection of the passing beam by controlling the application of voltage to the liquid crystal polarization grating plate and/or half-wave plate.
In the case where the secondary deflection module 126 is an electro-optic deflection module, the corresponding secondary deflection control unit 188 controls the angle of deflection of the passing beam by adjusting the strength of the electric field applied to the electro-optic deflection module 126. In some embodiments, the acousto-optic deflection module 124 is configured to deflect the passing light beam along a first direction by a plurality of different preset deflection angles within a preset deflection angle range, the electro-optic deflection module 126 is configured to deflect the passing light beam along a second direction different from the first direction by a plurality of different preset deflection angles within the preset deflection angle range according to the intensity of the electric field applied by the electro-optic deflection module, and the light beam emitted by the light source module 122 forms a sensing light beam for two-dimensional scanning of the detection range after being deflected by the acousto-optic deflection module 124 and the electro-optic deflection module 126 respectively. Alternatively, the first direction may be a horizontal direction, and the second direction may be a vertical direction; or the first direction is a vertical direction, and the second direction is a horizontal direction.
In some embodiments, the control module 18 may further include an emission energy adjustment unit 189 configured to adjust the energy of the emitted sensing beam emitted by the entire emission module 12 by adjusting the energy of the beam emitted after being deflected by at least one of the acousto-optic deflection modules 124.
As described above, the acousto-optic deflection module 124 deflects the passing light beam by using the abnormal bragg diffraction of the light beam in the acousto-optic interaction medium 1241, and the abnormal bragg diffraction of the light beam in the acousto-optic interaction medium 1241 only considers the zero-order light and the first-order diffracted light which are not deflected, wherein the deflection angle of the first-order diffracted light relative to the incident light beam is proportional to the frequency of the sound wave, and the zero-order light does not participate in scanning, that is, the sensing light beam in the subsequent light path is the first-order diffracted light of the light beam diffracted by the acousto-optic interaction medium 1241.
If the diffraction efficiency η is defined as the ratio of the optical power of the first-order diffracted light to the total optical power, the diffraction efficiency is highest when the wave vectors of the incident light beam, the outgoing first-order diffracted light beam, and the acoustic wave satisfy the momentum matching condition. In practice, the acousto-optic deflection module 124 is typically designed to satisfy the momentum matching condition at the center frequency of the Bragg bandwidth, while the acousto-optic momentum matching condition is approximately satisfied at other acoustic wave frequencies within the Bragg bandwidth. When the momentum matching condition is satisfied when the center frequency of the Bragg bandwidth is taken at the acoustic wave frequency, the calculation formula of the diffraction efficiency can be represented by the following relational expression (3):
Where L is the length of the effective area of the acousto-optic interaction medium 1241 in the direction of the incident beam, H is the length of the effective area of the acousto-optic interaction medium 1241 in the direction perpendicular to the plane formed by the incident beam and the diffracted beam, λ is the wavelength of the diffracted beam, M 2 is the acousto-optic figure of merit of the acousto-optic interaction medium 1241, and I is the acoustic power. If order The calculation formula of the diffraction efficiency η can be simplified expressed as a relation (4):
It can be seen that the diffraction efficiency η and the corresponding applied acoustic wave power value are in a periodic function variation relationship, and the energy value of the sensing beam emitted after deflection and the corresponding applied acoustic wave power value are also in a periodic function variation relationship The maximum value is reached. In practical applications, the diffraction efficiency η does not reach a theoretical maximum value due to the divergence angle of the incident beam itself. When the acoustic wave frequency is not at the center frequency of the Bragg bandwidth, the actual maximum value of the diffraction efficiency is reduced along with the increase of the momentum mismatch due to the momentum mismatch among the incident beam vector, the emergent diffraction beam vector and the acoustic wave vector, but the overall change rule can still be regarded as a change relation which approximately meets the periodic function. Therefore, the change condition of the diffraction efficiency eta along with the sound wave power I when the sound wave frequency takes the center frequency of the Bragg bandwidth can be used as the basis for qualitatively judging the change of the diffraction efficiency eta along with the sound wave power I under different sound wave frequencies.
Taking the example that the sound wave frequency is at the center frequency of the Bragg bandwidth, if the theoretical maximum value of diffraction efficiency is 100% when the maximum sensing beam emission energy is reached, the corresponding applied sound wave power I needs to be satisfied Let us note that the applied acoustic wave power I at this time is 1, the following table 1 gives the required corresponding applied acoustic wave power I when the diffraction efficiency η is 50%, 10% and 1% of the theoretical maximum value, respectively: /(I)
TABLE 1
| Sonic power (I) | Diffraction efficiency eta |
| 0.004 | 1％ |
| 0.042 | 10％ |
| 0.25 | 50％ |
| 1 | 100％ |
From the above, the emission energy of the sensing beam can be reduced to 1% of the maximum emission energy by adjusting the acoustic wave power to 0.4% of the applied acoustic wave power I when the maximum diffraction efficiency η is obtained.
Because of the periodic functional variation between diffraction efficiency η and the corresponding applied acoustic power, higher acoustic powers may also be used to obtain the same diffraction efficiency η, as shown in table 2 below:
TABLE 2
| Sonic power (I) | Diffraction efficiency eta |
| 1 | 100％ |
| 2.25 | 50％ |
| 3.22 | 10％ |
| 3.75 | 1％ |
From the above, the emission energy of the sensing beam can also be reduced to 1% of the maximum emission energy by adjusting the acoustic power to about 4 times the acoustic power I applied when the maximum diffraction efficiency η is obtained, in which case the sensitivity of the diffraction efficiency η to changes in acoustic power is improved, which is advantageous for more accurate adjustment of the emission energy of the sensing beam by changing the acoustic power.
Based on the analysis, the emission energy adjustment unit 189 can correspondingly adjust the energy of the light beam emitted after being deflected by at least one of the acousto-optic deflection modules 124 by changing the applied acoustic wave power, thereby adjusting the energy of the sensing light beam emitted by the entire emission module 12. Due to the periodic functional variation relationship between the diffraction efficiency η and the corresponding acoustic power value as in the relationship (4), the emission energy adjustment unit 189 may select a plurality of different acoustic power value adjustment intervals to correspondingly adjust the emission energy of the sensing beam according to the actual situation. In practical application, the acoustic wave power required to be applied by the different emission energies of the corresponding sensing light beams can be determined through test calibration before delivery.
It should be appreciated that the emission energy adjustment unit 189 may include at least a driving circuit of the sonic generator 1242 to control sonic power applied to the acousto-optic deflection module 124.
It should be understood that the acousto-optic deflection control unit 184 adjusts the deflection angle of the sensing beam by changing the frequency of the acoustic wave and the emission energy adjustment unit 189 adjusts the emission energy of the sensing beam by changing the power of the acoustic wave for a time equal to about the transit time τ of the acoustic wave in the acousto-optic interaction medium 1241, so that the acousto-optic deflection control unit 184 and the emission energy adjustment unit 189 can simultaneously change the frequency and power of the acoustic wave signal applied to the acousto-optic deflection module 124 while correspondingly changing the deflection angle of the sensing beam.
In some examples, the emission energy adjustment unit 189 may also adjust the emission energy of the sensing beam by changing the light emitting power of the light source module 122. For example, the emission energy adjusting unit 189 adjusts the light emitting power thereof by adjusting the driving current or the driving voltage of the light emitting unit 1220 of the light source module 122.
In some embodiments, the emission energy adjustment unit 189 is configured to adjust the emission energy of the sensing beam by simultaneously changing the acoustic wave power and the light emitting power of the light source module 122. In this case, compared to adjusting the emission energy of the sensing beam in only one way, adjusting the emission energy of the sensing beam simultaneously in two different ways can increase the adjustment amplitude of the emission energy of the sensing beam, or can reduce the difficulty of the emission energy adjustment, such as: each of these modes of adjustment requires a smaller individual change in amplitude to achieve a more pronounced adjustment of the emitted energy, and a smaller change in amplitude is easier to achieve.
In some embodiments, the photo-detection device 10 may have a difference in the distance detection range along different angles in the detection range, for example, when the photo-detection device 10 is used as a main lidar of an automobile, the requirement for the distance detection range of the central angle of the detection range is higher and the requirement for the distance detection range of the edge angle of the detection range is relatively lower, and the distance detection range to be satisfied and the energy of the sensing beam to be emitted are generally in a positive correlation. Correspondingly, the emission energy adjusting unit 189 adjusts the applied acoustic power to increase the emission energy of the sensing beam when the sensing beam is deflected to the central angle of the detection range, and adjusts the applied acoustic power to decrease the emission energy of the sensing beam when the sensing beam is deflected to the edge angle of the detection range, so as to reduce the potential safety risk brought by the high-energy sensing beam as much as possible on the premise of meeting the requirement of different distance detection maximum values in the detection range.
In some embodiments, as shown in fig. 6, the emission module 12 includes two separate acousto-optic deflection modules, namely a first acousto-optic deflection module 124a and a second acousto-optic deflection module 124b, where the first acousto-optic deflection module 124a is configured to deflect the light beam passing through the first acousto-optic deflection module 124a in a first direction within a predetermined deflection angle range, and the second acousto-optic deflection module 124b is configured to deflect the light beam deflected by the first acousto-optic module 124a in a second direction within a predetermined deflection angle range, and the second direction is different from the first direction. Thus, the light beams emitted by the light source module 122 are deflected by the first acousto-optic deflection module 124a and the second acousto-optic deflection module 124b to form sensing light beams for two-dimensional scanning of the detection range. Alternatively, the first direction may be a horizontal direction, and the second direction may be a vertical direction; or the first direction is a vertical direction, and the second direction is a horizontal direction.
It should be understood that the second acousto-optic deflection module 124b may be disposed close to the light emitting side of the first acousto-optic deflection module 124a, or may be spaced from the first acousto-optic deflection module 124a by a plurality of other optical path devices, which is not particularly limited in the present application.
In this case, the emission energy adjusting unit 189 is connected to the first acousto-optic deflection module 124a and the second acousto-optic deflection module 124b, respectively, and adjusts the diffraction efficiency of the first acousto-optic deflection module 124a and the second acousto-optic deflection module 124b on the passing light beam by changing the first acoustic wave power applied to the first acousto-optic deflection module 124a and the second acoustic wave power applied to the second acousto-optic deflection module 124b, thereby adjusting the energy of the sensing light beam emitted from the entire emission module 12. According to the above qualitative analysis, if the theoretical maximum value of the diffraction efficiency is 100% when the maximum sensing beam emission energy is reached, the same acoustic power I is correspondingly applied to the first acoustic-optical deflection module 124a and the second acoustic-optical deflection module 124b, so as to satisfy the following requirements Let us note that the applied acoustic wave power I at this time is 1, the following table 3 shows the required corresponding applied acoustic wave power I when the first diffraction efficiency η1 of the first acousto-optic deflection module 124a and the second diffraction efficiency η2 of the second acousto-optic deflection module 124b are 50%, 10% and 1% of the theoretical maximum, respectively:
TABLE 3 Table 3
| Sonic power (I) | First diffraction efficiency eta 1 | Second diffraction efficiency eta 2 | Total diffraction efficiency eta |
| 1 | 100％ | 100％ | 100％ |
| 0.25 | 50％ | 50％ | 25％ |
| 0.042 | 10％ | 10％ | 1％ |
| 0.004 | 1％ | 1％ | 0.01％ |
From the above, the sensing light beam with the highest emission energy as low as 1% can be emitted to the whole emission module only by reducing the diffraction efficiency of the single acousto-optic deflection module to 10%, so that the design difficulty of the emission energy adjusting unit on the adjustment of the acoustic wave power can be reduced. On the other hand, the control of the sensing beam emergent energy with high accuracy on the level of 0.01% can be realized for the whole transmitting module by reducing the diffraction efficiency of each acousto-optic deflection module to 1%. It should be appreciated that in other embodiments, the emitting module 12 may also include more than two acousto-optic deflection modules 124, so that the deflection of the sensing beam within the detection range is achieved by these acousto-optic deflection modules 124. The emission energy adjustment unit 189 may also adjust the energy of the entire emission module 12 emitted sensing beam by varying the acoustic power applied to any one or each of the acoustic-optic modules 124.
For sensing of a scanning angle within the detection range, the emission energy adjustment unit 189 may adjust the first plurality of sensing beam pulses emitted first in one zone detection period to have a lower first emission energy by changing the acoustic power applied to at least one of the acousto-optic deflection modules 124, and then change the acoustic power applied to at least one of the acousto-optic deflection modules 124 according to the analysis of the sensed echoes of the first sensing beam pulses by the processing module 15 to adjust the emission energy of the second plurality of sensing beam pulses emitted later in the same zone detection period. It should be appreciated that the first emission energy may be set according to the relevant safety standard to be met when the photo-detection device 10 performs the close range detection, where the close range may refer to, for example, one fifth, one tenth, one twentieth, one thirty th, etc. of the distance detection furthest value to be met by the current scanning angle of the sensing beam, or may also be a distance value related to the actual use scenario, for example: 2 meters, 3 meters, 5 meters, 8 meters, 10 meters, etc.
In some embodiments, if the analysis of the first sensing beam pulse echo shows that there is an object within the preset maximum safe distance, the transmitting module 12 stops transmitting the sensing beam pulse, and the processing module 15 directly outputs the analysis result of the first sensing beam pulse echo as the sensing result of the current zone detection period, where the analysis result may include, but is not limited to, distance information of the object, reflectivity of the object, and the like.
If the analysis of the first sensing beam pulse echoes shows that no object is present within a preset maximum safe distance, the emission energy adjustment unit 189 adjusts the plurality of second sensing beam pulses emitted later within the same zone detection period to have a higher second emission energy, i.e. the second emission energy is greater than the first emission energy, by varying the acoustic power applied on at least one of the acousto-optic deflection modules 124. Alternatively, the second emission energy may be equal to or greater than a highest emission energy required for sensing a furthest value of the distance that the beam pulse is required to meet along the current scan angle; alternatively, the second emission energy may be smaller than the highest emission energy, and the appropriate emission energy is determined from object distance information obtained from an analysis of the first sensing beam pulse echo. After emitting the second sensing beam pulse, the processing module 15 obtains a sensing result of the current partition detection period according to an analysis of the second sensing beam pulse echo, such as: distance information and reflectivity of the object, etc.
It is understood that the absence of an object within a preset maximum safe distance may mean that the analysis result of the first sensing beam pulse echo is that the first sensing beam pulse echo is not sensed or that object distance information obtained from the sensed first sensing beam pulse echo is greater than the maximum safe distance.
It should be understood that the predetermined maximum safe distance may be defined as the nearest distance that still satisfies the relevant safety standard when the sensing beam is emitted at the highest emission energy, that is, if the distance between the person and the emission module 12 is equal to or greater than the maximum safe distance, even if the emission module 12 emits the sensing beam at the highest emission energy for scanning sensing, the relevant safety standard is met for the person without injury.
In some embodiments, if the analysis of the first sensing beam pulse echo shows that there is an object within a preset maximum safe distance, the emission energy adjustment unit 189 may maintain the acoustic power applied on the acousto-optic deflection module 124 such that the plurality of second sensing beam pulses emitted after the same zone detection period still have the lower first emission energy. After emitting the second sensing beam pulse, the processing module 15 obtains a sensing result of the current partition detection period according to the analysis of the first sensing beam pulse echo and the second sensing beam pulse echo, such as: distance information and reflectivity of the object, etc. By integrating the echo generated by the second sensing beam pulse emitted later with the first sensing beam pulse emitted earlier, the detection performance of the photodetection device 10 in close proximity can be improved, for example: improving dynamic range, improving accuracy, etc., while maintaining a lower first emission energy also meets relevant safety standards.
In some embodiments, if the analysis of the first sensing beam pulse echoes shows that there is an object within a preset maximum safe distance, the emission energy adjustment unit 189 may adjust the plurality of second sensing beam pulses emitted after the same segment detection period to have a third emission energy that is in positive correlation with the object distance obtained by the processing module 15 for the first sensing beam pulse echo analysis, by varying the acoustic power applied on at least one of the acousto-optic deflection modules 124, up to a maximum of the relevant safe criteria that should be met at that object distance. It will be appreciated that since the object distance is less than the maximum safe distance, the third emission energy also corresponds to less than the highest emission energy required to meet the distance detection furthest value of the current scan angle, but may be greater than the first emission energy. After emitting the second sensing beam pulse, the processing module 15 may obtain a sensing result of the current partition detection period according to an analysis of an echo of the second sensing beam pulse; alternatively, the processing module 15 may obtain the sensing result of the current partition detection period according to the analysis of the second sensing beam pulse echo and the first sensing beam pulse echo. Therefore, even if an object exists in the maximum safety distance, the emission energy emitted by the rear section of the partition detection period can be reasonably adjusted according to the actual distance of the object, and the sensing quality is improved as much as possible on the premise of meeting the relevant safety standard.
In some embodiments, the photo detection device 10 or the electronic apparatus 1 equipped with the photo detection device 10 may further include at least one speed sensor to sense a moving speed of the electronic apparatus 1 or the photo detection device 10. The emission energy adjustment unit 189 is configured to detect the second sensing beam pulse having a higher second emission energy by changing the acoustic wave power applied to at least one of the acousto-optic deflection modules 124 without first emitting the first sensing beam pulse having a lower energy for a segment detection period, if the moving speed of the photo-detecting device 10 exceeds a preset speed threshold, the second emission energy may be equal to or greater than the highest emission energy required for detecting the farthest value of the sensing beam pulse along the distance to be satisfied by the current scanning angle. Since the photo detection device 10 is in a fast moving condition, the duration of the emitted sensing beam pulse impinging on a person is greatly reduced even if the person is within a maximum safe distance, the sensing beam pulse may meet the relevant safety standards even if emitted with the highest emission energy, which is advantageous for improving the quality of sensing.
It should be understood that, if the moving speed of the photo-detecting device 10 is less than or equal to the preset speed threshold, the emission energy adjustment unit 189 may adjust the first sensing beam pulse with lower energy during one zone detection period according to the technical scheme described in the foregoing embodiment, and then change the acoustic wave power applied to at least one of the acousto-optic deflection modules 124 according to the analysis of the first sensing beam pulse echo by the processing module 15, so as to adjust the emission energy of the second sensing beam pulses emitted after the same zone detection period.
In some embodiments, all or a portion of the functional elements in the control module 18 and/or processing module 15 may include firmware solidified within the storage medium 30 or computer software code stored within the storage medium 30 and executed by the corresponding one or more processors 40 to control the relevant components to implement the corresponding functions. Such as, but not limited to, an application processor (Application Processor, AP), a central processor (Central Processing Unit, CPU), a microcontroller (Micro Controller Unit, MCU), etc. The storage medium 30 includes, but is not limited to, flash Memory (Flash Memory), charged erasable programmable read-only storage medium (ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY, EEPROM), programmable read-only storage medium (Programmable read only Memory, PROM), hard disk, and the like.
In some embodiments, the processor 40 and/or storage medium 30 may be disposed within the photodetection device 10, such as: is integrated on the same circuit board as the transmitting module 12 or the receiving module 14. Alternatively, in other embodiments, the processor 40 and/or the storage medium 30 may be located elsewhere in the electronic device 1, such as: on the main circuit board of the electronic device 1.
In some embodiments, some or all of the functional units of the control module 18 and/or the processing module 15 may also include hardware, such as implemented by any one or combination of the following technologies: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), driver circuits for specific objects, and the like.
It will be appreciated that the different functional units of the control module 18 and/or the processing module 15 may each comprise the same hardware, for example: the acousto-optic deflection control unit 184 and the emission energy adjustment unit 189 may each include a driving circuit of an acoustic wave generator 1242.
It will be appreciated that the hardware described above for implementing the functions of the control module 18 and/or the processing module 15 may be provided within the photo detection means 10. The hardware described above for implementing the functions of the control module 18 and/or the processing module 15 may also be provided in other locations of the electronic device 1, such as: is provided on a main circuit board of the electronic device 1.
As shown in fig. 8, in some embodiments, the photodetection device 10 is, for example, a lidar, and the electronic device 1 is, for example, an automobile. The laser radar can be arranged at a plurality of different positions on the automobile to detect the distance information of objects in the peripheral range of the automobile and realize driving control according to the distance information.
Compared with the laser radar which adopts a mechanical rotation mode and a mixed solid state mode to realize the scanning of the sensing light beam, the laser radar provided by the application adopts the acousto-optic deflection module 124 and the secondary deflection module 126 which are all solid states to realize the deflection scanning of the sensing light beam, has higher reliability and more compact structure because no rotation or vibration component is needed, is easier to pass strict vehicle specification requirements, and has less influence on the appearance of an automobile.
It should be noted that, the technical solution to be protected by the present application may only satisfy one of the embodiments described above or simultaneously satisfy the embodiments described above, that is, the embodiment formed by combining one or more embodiments described above also belongs to the protection scope of the present application.
In the description of the present specification, reference to the terms "one embodiment," "certain embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
It is to be understood that portions of embodiments of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the plurality of functional units may be implemented in software or firmware stored in a storage medium and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application.
Claims (16)
1. An acoustic-optical effect based emission module configured to emit a sensing beam for three-dimensional information detection based on a time-of-flight principle toward a detection range, comprising:
A light source module configured to emit a light beam;
At least one acousto-optic deflection module comprising an acousto-optic interaction medium and an acoustic wave generator configured to generate an acoustic wave propagating in a preset direction within the acousto-optic interaction medium; and
A control module including an acousto-optic deflection control unit configured to deflect a light beam passing through the acousto-optic interaction medium within a preset deflection angle range by controlling an acoustic wave frequency applied by the acoustic wave generator as a sensing light beam scanning the detection range by a plurality of different preset deflection angles, and an emission energy adjustment unit configured to correspondingly adjust an energy of the sensing light beam by changing an acoustic wave power applied by the acoustic wave generator.
2. The emitter module of claim 1, wherein the sensing beam is first order diffracted light of a beam diffracted by the acousto-optic interaction medium.
3. The transmitting module of claim 1, wherein the energy value of the sensing beam is a periodic function of the corresponding acoustic power value.
4. The emission module of claim 1, wherein the emission energy adjustment unit is configured to correspondingly adjust the emission energy of the sensing beam by simultaneously changing the light emitting power of the light source module.
5. The transmitting module according to claim 1, comprising two separate acousto-optic deflection modules, namely a first acousto-optic deflection module and a second acousto-optic deflection module, wherein the first acousto-optic deflection module is configured to deflect the passing light beam in a first direction by a plurality of different preset deflection angles within a preset deflection angle range, the second acousto-optic deflection module is configured to deflect the passing light beam in a second direction different from the first direction by a plurality of different preset deflection angles within the preset deflection angle range, the light beams emitted by the light source module are respectively deflected by the first acousto-optic deflection module and the second acousto-optic deflection module to form sensing light beams which two-dimensionally scan a detection range, and the transmitting energy adjusting unit adjusts energy of the sensing light beams by controlling acoustic wave power applied to at least one of the acousto-optic deflection modules.
6. The transmitting module of claim 1, further comprising an electro-optical deflection module configured to deflect the passing light beam in a first direction by a plurality of different preset deflection angles within a preset deflection angle range, the electro-optical deflection module configured to deflect the passing light beam in a second direction different from the first direction by a plurality of different preset deflection angles within the preset deflection angle range according to the intensity of an electric field applied by the electro-optical deflection module, the light beam emitted by the light source module being deflected by the acousto-optical deflection module and the electro-optical deflection module respectively to form a sensing light beam which performs two-dimensional scanning on a detection range, and the control module adjusting the energy of the sensing light beam by controlling the power of an acoustic wave applied to the acousto-optical deflection module.
7. The transmitting module of claim 5 or 6, wherein the first direction is a horizontal direction and the second direction is a vertical direction; or alternatively
The first direction is a vertical direction, and the second direction is a horizontal direction.
8. A photo-detection device configured to perform distance detection on an object located within a preset detection range, the photo-detection device comprising a transmitting module according to any one of claims 1-7, the photo-detection device further comprising a receiving module configured to sense an optical signal from the detection range and output a corresponding photo-induced signal, and a processing module configured to analyze and process the photo-induced signal to perform distance detection within the detection range.
9. The photodetection device according to claim 8, wherein the emission energy adjustment unit adjusts the emission energy of the plurality of first sensing beam pulses emitted first in the divisional detection period to have lower first emission energy by controlling the acoustic power applied to at least one of the acousto-optic deflection modules during the same divisional detection period in which distance detection is performed along a corresponding divisional of a preset scanning angle in the detection range, and then controls the acoustic power applied to at least one of the acousto-optic deflection modules according to analysis of the echoes of the sensed first sensing beam pulses by the processing module to adjust the emission energy of the plurality of second sensing beam pulses emitted after the divisional detection period.
10. The photodetection device according to claim 9, wherein the emission energy adjustment unit adjusts a plurality of second sensing beam pulses emitted later in the divisional detection period to have a higher second emission energy by changing the acoustic wave power applied to at least one of the acousto-optic deflection modules to obtain the sensing result of the current divisional detection period according to the analysis of the second sensing beam pulse echoes, if the analysis of the first sensing beam pulse echoes shows that no object exists within a preset maximum safe distance.
11. The photodetection device according to claim 10, wherein the second emission energy is equal to or greater than a highest emission energy required for detecting a farthest value of the sensing beam pulse along a distance to be satisfied by a current scanning angle; or alternatively
The second emission energy is less than the highest emission energy, and a suitable emission energy is determined from object distance information obtained from an analysis of the first sensing beam pulse echo.
12. The photodetection device according to claim 9, wherein the transmission module stops transmitting the sensing beam pulse if the analysis of the first sensing beam pulse echo shows that an object exists within a preset maximum safe distance, and the processing module directly outputs the analysis result of the first sensing beam pulse echo as the sensing result of the current zone detection period.
13. The photo detection apparatus as claimed in claim 9, wherein if the analysis of the first sensing beam pulse echo shows that there is an object within a preset maximum safe distance, the emission energy adjustment unit maintains the acoustic power applied on the acousto-optic deflection module so that the plurality of second sensing beam pulses emitted after the zone detection period still have the first emission energy lower, and the processing module obtains the sensing result of the current zone detection period according to the analysis of the first sensing beam pulse echo and the second sensing beam pulse echo.
14. The photodetection device according to claim 9, wherein if the analysis of the first sensing beam pulse echo shows that there is an object within a preset maximum safe distance, the emission energy adjustment unit adjusts the plurality of second sensing beam pulses emitted later within the same segment detection period to have a third emission energy in positive correlation with the object distance obtained by the processing module for the first sensing beam pulse echo analysis by varying the acoustic wave power applied to at least one of the acousto-optic deflection modules, up to a maximum exceeding a relevant safe criterion that should be satisfied at that object distance.
15. The photo detection apparatus as claimed in claim 8, wherein the emission energy adjustment unit is configured to emit a plurality of second sensing beam pulses having a second emission energy equal to or greater than a highest emission energy required for sensing a farthest value of the distance to be satisfied by the sensing beam pulses along the current scan angle by varying the acoustic wave power applied on at least one of the acousto-optic deflection modules if the moving speed of the photo detection apparatus exceeds a preset speed threshold.
16. An electronic device comprising the photodetection means according to claims 8-15, the electronic device further comprising an application module configured to implement a corresponding function according to the detection result of the photodetection means.
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