WO2022017366A1

WO2022017366A1 - Depth imaging method and depth imaging system

Info

Publication number: WO2022017366A1
Application number: PCT/CN2021/107301
Authority: WO
Inventors: 余恺; 俞锋; 贝努瓦菲利普; 屈丰广; 张朝龙; 曾佳
Original assignee: 华为技术有限公司
Priority date: 2020-07-23
Filing date: 2021-07-20
Publication date: 2022-01-27
Also published as: CN113970757A

Abstract

A depth imaging method and a depth imaging system, the method comprising: scanning a target object at different scanning angles, and emitting laser pulses in pulse emission cycles at each scanning angle (501); in each pulse emission cycle, polling and controlling the on or off of photodetection units on a photoelectric sensor (502), each photoelectric detection unit of the photoelectric sensor being divided into multiple super-division pixels according to the size of laser spots; obtaining depth information of laser spots at a current scanning angle according to electrical signals provided by the photoelectric detection units that are polled and turned on during the pulse emission cycle (503); and after the target object is scanned, splicing the depth information of the laser spots at respective scanning angles to obtain a super-resolution depth image of the target object (504). The cumulative exposure time of the photoelectric detection units on the photoelectric sensor is greatly shortened, thus reducing power consumption and increasing the frame rate and imaging speed, and converted signals have a high signal-to-noise ratio, thus facilitating improvement of the imaging quality of the depth image of the target object.

Description

Depth imaging method and depth imaging system

This application claims the priority of the Chinese patent application filed on July 23, 2020 with the State Intellectual Property Office of the People's Republic of China, the application number is 202010716865.3, and the invention name is "a depth imaging method and depth imaging system", the entire content of which is approved by Reference is incorporated in this application.

technical field

The present application relates to the field of imaging technologies, and in particular, to a depth imaging method and a depth imaging system.

Background technique

With the development of science and technology, computer vision has been widely used in people's daily life and all walks of life, such as geographic mapping and imaging, remote sensing, automotive autonomous driving, autonomous vehicles, collaborative robots, 3D depth measurement, and consumer electronics. Radar is an important technology for realizing computer vision. Radar includes but is not limited to lidar, millimeter-wave radar, and visible light radar. A 3D camera is an application example of a radar system. The example system consists of a laser pulse transmitter, a laser pulse receiver, a Time to Digital Converter (TDC), and a control system.

In the radar working scene, the laser pulse transmitter generates light pulses and transmits them into the environment. After the light pulses are reflected by the target objects in the environment, they are received by the receiver. The receiving end converts the received photons into electrical signals and then provides them to the TDC. The timing of the emission of the TDC reference pulse quantifies the delay of the returning photons and puts them into a time grid of a given width. When enough pulses are fired, the number of events in the time grid can form a histogram. The highest position in the histogram corresponds to the time of flight (TOF) of the pulse, through which the distance of the target object can be calculated.

Photoelectric sensors are usually used as receivers to detect light pulses. Depth imaging is widely used in fields such as computer vision. With the continuous enrichment of the application requirements of depth imaging, the demand for resolution of depth imaging is also getting higher and higher. However, due to the limitation of semiconductor technology and volume, the resolution of the photodetection unit on the photoelectric sensor is difficult to meet the actual demand.

At present, the contradiction between the high-resolution requirement of depth imaging and the low-resolution performance of the photoelectric sensor can be solved through the lattice super-resolution technology. On the basis of the original resolution of the photoelectric sensor, a virtual super-resolution pixel with smaller size can be constructed, so as to make the The resolution of photoelectric sensors has been improved to meet the high-resolution requirements of depth imaging. The transceiver module of the 3D camera used in depth imaging usually has a certain baseline distance, which leads to the mismatch of the transceiver position, and the mismatch offset is also called parallax. Parallax takes the number of photodetection units as a measurement unit, and the parallax changes with the target distance. Due to the existence of parallax, under the condition that the target distance is unknown, the photoelectric sensor cannot determine the position of the photoelectric detection unit where the laser spot is located. Therefore, it is often necessary to turn on all the surrounding photodetection units to detect the photodetector units that have received the pulse. However, the power consumption generated by fully opening the photodetector unit in the strong ambient light scene is unbearable for the chip. At the same time, due to the limitation of the number of TDCs, multiple photodetector units share one TDC. When the photodetector unit is fully opened, only one photodetector unit has a target signal, and the rest of the photodetector units detect noise, which seriously reduces the TDC receiving signal. signal-to-noise ratio, and it is difficult to determine the signal light from the histogram.

At present, the position of the light spot can be detected by turning on the photoelectric detection unit in a time-sharing manner. In the time-sharing open mode, each photoelectric detection unit is exposed for a certain period of time in turn, but this detection method requires many exposure times and long exposure time, resulting in very high system power consumption, lower frame rate, and slower depth imaging speed. In order to reduce the exposure times and exposure time, currently only a plurality of photodetection units can be fully turned on at the same time, which reduces the signal-to-noise ratio of the histogram and thus reduces the detection probability of signal light.

SUMMARY OF THE INVENTION

The present application provides a depth imaging method and a depth imaging system, so as to reduce system power consumption while ensuring a signal-to-noise ratio, achieve high frame rate lattice super-resolution, and improve the speed of depth imaging.

In a first aspect, the present application provides a depth imaging method, including:

Scan the target object at different scanning angles, and emit laser pulses with pulse emission cycles at each scanning angle;

In each pulse emission period, the photoelectric detection unit on the photoelectric sensor is polled to be turned on and off; the photoelectric sensor includes a plurality of photoelectric detection units, and each photoelectric detection unit is divided into a plurality of super-divided pixels according to the size of the laser spot;

Obtain the depth information of the laser spot at the current scanning angle according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period;

After the target object is scanned, the depth information of the laser spot at each scanning angle is spliced to obtain a super-resolution depth image of the target object.

Optionally, polling and controlling the photodetection unit on the photoelectric sensor to turn on and off in each pulse emission period specifically includes:

Determine the photodetector units to be polled in each pulse emission period;

determining a time window corresponding to each of the photodetection units to be polled;

Each of the photodetection units to be polled is polled and controlled to be turned on and off according to the time window.

Optionally, the laser pulses are emitted with a pulse emission period at each scanning angle, which specifically includes:

The laser pulses are emitted to the target object in a dot matrix projection manner for a plurality of the pulse emission periods at each scanning angle, so as to simultaneously form a plurality of laser light spots on the photoelectric sensor;

The determining of the photoelectric detection units to be polled in each pulse emission period specifically includes:

Obtain the minimum interval between two adjacent laser spots in the field of view of the laser;

According to the photodetection unit without parallax and the minimum interval, the photodetection unit to be polled corresponding to each laser spot in each pulse emission period is determined.

Optionally, obtain the minimum interval between two adjacent laser spots in the field of view of the laser, specifically including:

According to the baseline distance between the laser and the photoelectric sensor, the minimum detection distance of the photoelectric sensor, the lateral field angle and lateral resolution of the photoelectric detection unit, two adjacent lasers in the field of view of the laser are obtained Minimum spacing of the spots.

Optionally, determining the time window corresponding to each photoelectric detection unit to be polled specifically includes:

determining the offset range of each of the photodetection units to be polled relative to the photodetection units without parallax;

According to the offset range and the corresponding relationship between the offset and the distance, determine the corresponding distance range when the laser spot falls on each of the photoelectric detection units to be polled;

According to the distance range and the corresponding relationship between the distance and the time delay, determine the time-of-flight range in which each photoelectric detection unit to be polled can receive the laser spot; the time-of-flight range is used as the time window.

Optionally, according to the electrical signal provided by each photoelectric detection unit turned on by polling in the pulse emission period, obtain the depth information of the laser spot under the current scanning angle, specifically including:

Generate a direct flight time histogram corresponding to the current scanning angle according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period under the current scanning angle;

Find peaks in the direct flight time histogram, and determine the flight time corresponding to the laser spot at the current scanning angle;

According to the flight time and the corresponding relationship between the flight time and the distance, the distance information of the laser spot at the current scanning angle is obtained as the depth information of the laser spot.

Optionally, after obtaining the distance information of the laser spot at the current scanning angle as the depth information of the laser spot, the method further includes:

The offset corresponding to the distance information is obtained according to the correspondence between the offset and the distance; the integer part of the offset indicates the number of photodetection units offset by the target photodetection unit relative to the photodetection unit without parallax, The target photoelectric detection unit is the photoelectric detection unit where the laser spot is located, and the fractional part of the offset indicates the super-divided position where the laser spot is received in the target photoelectric detection unit;

According to the offset and the superdivision multiple of the photoelectric sensor, determine the superdivision pixel at which the laser spot is detected in the target photoelectric detection unit under the current scanning angle, so as to construct the relationship between the depth information and the superdivision pixel. Correspondence;

After the scanning of the target object is completed, the depth information of the laser spot at each scanning angle is spliced, which specifically includes:

After the target object is scanned, the depth information of the laser spot at each scanning angle is stitched together by using the corresponding relationship between the depth information and the super-divided pixels.

Optionally, scan the target object at different scanning angles, including:

The laser light path is adjusted before scanning the target object at the next scanning angle to form the next scanning angle.

In a second aspect, the present application provides a depth imaging system, including: a laser, a controller, a gating element, a photoelectric sensor, a time-to-digital converter, and a processor; the controller is connected to the laser; the photoelectric sensor includes multiple photoelectric detection units, each photoelectric detection unit is divided into a plurality of super-divided pixels according to the size of the laser spot; the gating switch is connected to all the photoelectric detection units of the photoelectric sensor; the controller and the processor The time-to-digital converters are respectively connected; the time-to-digital converters are also connected to the photodetection unit through the gate switch;

The controller is used to control the laser to scan the target object with different scanning angles, and emit laser pulses with a pulse emission period under each scanning angle;

The gate switch is used to poll and control the photodetection unit on the photoelectric sensor to turn on and off in each pulse emission period; the turned-on photodetection unit is used to receive the light signal reflected by the target object, and to converting the optical signal into an electrical signal;

The time-to-digital converter is used to obtain the flight time according to the electrical signals provided by each photoelectric detection unit that is turned on by polling in the pulse emission period and the emission time of each pulse under the current scanning angle, and convert the flight time into counts value;

The processor is configured to form a direct time-of-flight histogram corresponding to the current scanning angle according to the count value converted by the time-to-digital converter and the electrical signal; Depth information of the laser spot; after the laser scans the target object, the depth information of the laser spot at each scanning angle is spliced to obtain a super-resolution depth image of the target object.

Optionally, the laser includes: a laser light source, a collimating lens, a deflecting mirror, a light splitting element and a driving device;

The laser light source is used to emit a laser beam, and the laser beam includes laser pulses emitted according to a pulse emission period;

the collimating lens is used for collimating and sending the laser beam to the deflecting mirror;

The deflecting mirror is connected with the driving device, and is used for reflecting the laser beam from the collimating lens to the beam splitting element; during the period, the deflecting mirror is periodically deflected by the driving device;

The beam splitting element is used for splitting the received laser beam into multiple beams, and then projecting the multiple laser beams to the target object.

As can be seen from the above technical solutions, the embodiments of the present application at least have the following advantages:

In the depth imaging method provided by the present application, the target object is scanned at different scanning angles, and laser pulses are emitted in a pulse emission period under each scanning angle; in each pulse emission period, the photoelectric detection unit on the photoelectric sensor is polled and controlled to be turned on The photoelectric sensor includes a plurality of photoelectric detection units, and each photoelectric detection unit is divided into a plurality of super-divided pixels according to the size of the laser spot; according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period, the current After scanning the target object, the depth information of the laser spot at each scanning angle is spliced to obtain the super-resolution depth image of the target object. Since the photoelectric detection unit is turned on by polling in each pulse emission period, the cumulative exposure time of the photoelectric detection unit on the photoelectric sensor is greatly shortened compared with the time-sharing opening of the photoelectric detection unit, which in turn can reduce power consumption and improve frame rate. and depth imaging speed. In addition, compared with the method of fully turning on the photodetector units at the same time, the polling-on method ensures that the photodetector units that are turned on at a certain time will not be interfered by other adjacent photodetector units, and the converted signal has a higher signal-to-noise ratio. Furthermore, ensuring a high effective signal detection probability is beneficial to improve the imaging quality of the depth image of the target object.

Description of drawings

Fig. 1 is a kind of lattice super-resolution schematic diagram;

FIG. 2 is a schematic diagram of the relationship between a transmitting field of view and a receiving field of view;

Fig. 3 is a kind of schematic diagram of the relationship between offset and distance;

4 is a schematic diagram of the actual size of the field of view of a single photoelectric detection unit in the RX field of view under various different distances;

5 is a flowchart of a depth imaging method provided by an embodiment of the present application;

Fig. 6 is a kind of laser dot matrix projection schematic diagram;

7 is a schematic diagram of the positional change of a plurality of laser light spots in the super-divided pixel when the scanning angle changes according to an embodiment of the present application;

FIG. 8 is a schematic diagram of the offset range of other photodetection units in the lateral direction relative to the photodetection unit without parallax according to an embodiment of the present application;

9 is a schematic diagram of the polling sequence of each photoelectric detection unit SPAD0 to SPAD4 to be polled in one pulse emission period provided by the embodiment of the present application;

10 is a schematic diagram of a direct flight time histogram provided by an embodiment of the present application;

11 is a schematic diagram of a lattice emission parallax provided by an embodiment of the present application;

12 is a flowchart of another depth imaging method provided by an embodiment of the present application;

13 is a schematic structural diagram of a depth imaging system according to an embodiment of the present application;

FIG. 14 is a schematic structural diagram of a laser according to an embodiment of the present application.

detailed description

When performing depth imaging, if the resolution of the photoelectric sensor cannot meet the imaging requirements, the dot matrix super-resolution technique can be used to improve the resolution. The following briefly introduces the lattice super-separation technology with reference to the accompanying drawings.

Figure 1 is a schematic diagram of lattice super-resolution. As shown in Figure 1, the size of one photodetection unit corresponds to 4×4 super-divided pixels, and 4×4 photodetection units share one TDC. The size of the super-divided pixels in the photodetection unit matches the size of the laser spot. For example, the diameter of the laser spot is K, and the photodetection unit is divided into a plurality of super-divided pixels of K×K size. In addition, the diameter of the laser spot can also be slightly smaller than the size of the super-pixel.

FIG. 2 is a schematic diagram showing the relationship between the transmitting field of view and the receiving field of view. In Fig. 2, TX represents a laser, and RX represents a photoelectric sensor. The dashed line through TX represents the baseline of the laser and the dashed line through RX represents the baseline of the photosensor. As shown in Figure 2, there is a certain distance between the baselines of TX and RX. In Figure 2, the horizontal direction represents the offset, and the vertical direction represents the distance. Due to the existence of the baseline distance, the sending and receiving positions of light are mismatched, and the offset of the mismatch (also called parallax) is inversely proportional to the distance.

FIG. 3 is a schematic diagram of the relationship between the offset and the distance. In this embodiment of the present application, the offset is measured by the number of photodetection units, for example, 3 photodetector units are offset. Taking the lateral shift as an example, the actual meaning is to laterally shift the size of 3 photodetection units. As shown in Figure 3, the farther the distance, the smaller the offset; the closer the distance, the greater the offset.

Formula (1) shows how the offset is calculated:

In formula (1), σ represents the offset, d _baseline represents the baseline distance, and d _spad represents the size of the field of view of a single photoelectric detection unit corresponding to the actual field of view at a given distance. As shown in formula (1), in the case of a certain distance from the baseline, the size of the field of view of a single photodetector unit corresponds to the size in the actual field of view and is inversely proportional to the offset. Combining the relationship between the offset and the distance, it can be known that the field of view of a single photoelectric detection unit corresponds to the size in the actual field of view and is proportional to the distance.

Figure 4 shows the actual size of the field of view of a single photodetector unit in the RX field of view at various distances. As shown in Figure 3, at a distance closer to RX, a single photodetector unit corresponds to a smaller size in the RX field of view; at a farther distance from RX, a single photodetector unit corresponds to a larger size in the RX field of view.

Formula (2) shows the calculation method of the field of view of a single photoelectric detection unit corresponding to the size in the actual field of view:

In formula (2), d _spad represents the size of the field of view of a single photodetector unit corresponding to the actual field of view, Dist represents the distance, FOV _h represents the lateral field of _{view of the photodetector unit, and N h} represents the lateral resolution of the photodetector unit .

Combining formula (1) and formula (2), the relationship between offset and distance is obtained:

The premise of lattice super-resolution is to know the specific position of the light spot in the photoelectric detection unit to be super-separated in advance, and does not depend on the output of the photoelectric sensor. That is, the precise position of the light spot formed by the emitted laser pulse on the photosensor is predicted. At present, the time-sharing method of turning on the photodetector units requires sequentially turning on the photodetector units that may detect the light spot, and detecting whether there is a laser pulse in the histogram formed by the converted signals of these photodetector units to determine the position of the light spot. However, the time-sharing opening means multiple exposure times and exposure times, resulting in a doubled increase in system power consumption and a doubled drop in frame rate. Another method of fully opening the photoelectric detection unit at the same time is easy to detect a large amount of ambient light, which reduces the signal-to-noise ratio of the histogram, and the effective signal is easily covered by noise, which makes it difficult to detect the light pulse, and thus it is difficult to determine the spot position.

It can be seen from the above description that it is difficult to take into account the requirements of high imaging signal-to-noise ratio and low system power consumption when applying the lattice super-resolution technology for depth imaging at present.

Based on the above problems, the present application provides a depth imaging method and a depth imaging system. In the technical solution of the present application, the photoelectric detection unit on the photoelectric sensor is polled and controlled to be turned on and off in each pulse emission period, which shortens the exposure time of the photoelectric detection unit and reduces the number of exposures, thus saving system power consumption and improving the frame rate. Improve depth imaging speed. In addition, the signal-to-noise ratio of the histogram is enhanced, and the detection rate of valid signals is improved. In order to facilitate understanding of the technical solutions of the present application, the following detailed description is given in conjunction with the embodiments and the accompanying drawings.

Method example:

Referring to FIG. 5 , which is a flowchart of a depth imaging method provided by an embodiment of the present application. As shown in Figure 5, the depth imaging method includes:

Step 501 : Scan the target object with different scanning angles, and emit laser pulses with a pulse emission period at each scanning angle.

The target object refers to the object that depth imaging needs to present. According to the actual needs of the depth image, the target object may be a person, an animal, a building, etc. The type of the target object is not limited here. In the embodiment of the present application, a laser is used to transmit light pulses to the target object, and then the photoelectric sensor receives the light pulses reflected from the target object. The collimation of the laser is good, and a light spot is formed when it is projected on the target object, and the photoelectric sensor detects the light spot on the target object specifically.

In practical applications, various types of lasers can be used, such as lasers operating in the infrared band or lasers operating in the visible light band. The detection band of the photoelectric sensor should match the working band of the laser, so as to realize the effective detection of the formed light spot.

In order to comprehensively scan the target object for subsequent depth imaging, a two-dimensional line scan of the target object can be performed. Since the two-dimensional line scan can be divided into several independent one-dimensional line scans, in the following description, the horizontal one-dimensional line scan is taken as an example for description.

In the embodiment of the present application, the scanning angle of the laser to the target object changes constantly. The scanning angle can be changed by adjusting the laser light path inside the laser, or the scanning angle can be changed by adjusting the position of the laser as a whole without changing the laser light path inside the laser. After the laser optical path is adjusted, the next scanning angle is formed, and then the scanning is performed at the next scanning angle until the super-division scanning covering the entire receiving field of view is completed. In order to improve the scanning efficiency, the laser can be made to emit a laser lattice, and then multiple laser spots can be formed on the surface of the target object when the laser pulse is emitted. FIG. 6 is a schematic diagram of a laser dot matrix projection.

In the embodiment of the present application, the photoelectric sensor includes a plurality of photoelectric detection units. The photoelectric detection units on the photoelectric sensor are arranged according to the horizontal and vertical rules. The lateral dimension of each photodetector unit may be the same as the longitudinal dimension, or may be different from the longitudinal dimension. As an example, the photodetection unit may be a single photon avalanche diode (Single Photon Avalanche Diode, SPAD) or an avalanche photodiode (Avalanche Photon Diode, APD). The specific type of the photodetection unit is not limited here.

Each photodetection unit is divided into a plurality of super-divided pixels according to the size of the laser spot. For example, if the diameter of the laser spot is D, and the lateral and vertical dimensions of the photodetection unit are both 4D, each photodetector unit can be divided into 4*4 super-divided pixels. The photodetection unit is divided into a plurality of super-resolution pixels according to the size of the laser spot, in order to perform depth imaging with the depth information recorded when the light spot is detected by each super-resolution pixel, so as to meet the high resolution requirements for depth imaging.

For ease of understanding, the embodiment of the present application provides a schematic diagram of the position change of multiple laser light spots in the super-divided pixel when the scanning angle changes, as shown in FIG. 7 . The left side and the right side of FIG. 7 respectively show the position changes of the laser spots 001 to 002 in the photoelectric conversion unit of the photoelectric sensor under two scanning angles. It can be seen from FIG. 7 that when the scanning angle changes once, each laser spot 001 to 002 is laterally shifted by one super-divided pixel on the photoelectric sensor as a whole.

When scanning the target object at different scanning angles, laser pulses are emitted with a preset pulse emission period at each scanning angle, in order to accumulate enough photons to obtain the depth information of the laser spot subsequently. The pulse emission period can be set according to actual requirements, for example, the pulse emission period is set to 100ns.

Step 502 : polling and controlling the photodetection unit on the photoelectric sensor to turn on and off in each pulse emission period.

Under the condition that the scanning angle is unchanged, the photoelectric sensor detects that the position of the super-divided pixel of the light spot formed by the laser pulses emitted by the laser in different pulse emission periods is unchanged. However, in the detection stage, the specific photodetection unit that receives the light signal reflected from the laser spot, and the specific super-divided pixel on the photodetector unit that receives the light signal reflected from the laser spot are unknown.

In the embodiments of the present application, in order to save power consumption and improve the frame rate and depth imaging speed, an implementation scheme of controlling the opening and closing of the photoelectric detection unit by means of round-robin training is proposed. Specifically, as described in this step, in each pulse emission period, the photodetection unit on the photoelectric sensor is controlled to be turned on and off by polling.

In the above introduction to Figure 3, the farther the target object is, the smaller the offset of the TX field of view and the RX field of view. In the embodiment of the present application, the photodetection unit when the target distance is infinite and the TX and RX do not have parallax can be pre-calibrated as the photodetection unit without parallax. The position of the photodetection unit without parallax is used as a reference position to measure the offset of each other photodetection unit. Referring to FIG. 8 , it is a schematic diagram of the offset range of other photodetection units relative to the photodetection unit without parallax in the lateral direction. As shown in FIG. 8 , the offset range of the photodetection unit Spad i is [σ _i-1 , σ _i ].

According to formula (3), the relationship between the offset of the photoelectric detection unit and the distance of the target object can be known. Thus binding equation (3) to give dispersion range _{_{[σ i-1, σ i}} ] corresponding to the distance [d _imin, d _imax], d _imax upper and lower limits of the range of distance d _imin expression is as follows:

When performing depth imaging, the distance of the target object can be obtained by the time of flight of the light pulse emitted by the laser. The relationship between distance and flight time is as follows:

In formula (6), Δt represents the flight time, and c represents the speed of light. Therefore, according to formulas (4) to (6), the range of flight time [t _{init_i} , t _{end_i} _{] corresponding to the distance range [d i-1} _{, d i} ] of the target object detected by the photoelectric detection unit can be obtained, and the range of flight time [t The expressions for the lower and upper bounds of _{init_i} , t _{end_i ] are as follows:}

Before the polling controls the photodetection units to be turned on during the pulse emission period, the photodetection units to be polled may be determined first based on the determination. Then, the offset range of each photoelectric detection unit to be polled relative to the photodetection unit without parallax, combined with the relationship between the offset and the distance, obtain the corresponding distance range when the laser spot falls on each photoelectric detection unit to be polled, The time-of-flight range in which each photoelectric detection unit to be polled can receive the laser spot is determined based on the correspondence between distance and time delay, and the time-of-flight range is used as the time window for polling the photoelectric detection unit. In this way, the time window corresponding to each photoelectric detection unit to be polled is determined. Next, each photodetection unit to be polled is controlled to be turned on and off according to the time window polling.

Taking the photoelectric detection unit Spad i shown in Fig. 8 as an example, the flight time range [t _{init_i} , t _{end_i} ] obtained by combining formula (7) and formula (8), in each pulse emission period, take t _{init_i} as the ON At the moment of Spad i, set t _{end_i} as the moment of closing Spad i. For ease of understanding, FIG. 9 exemplarily shows the polling sequence of each of the photodetection units SPAD0 to SPAD4 to be polled in one pulse emission period. As shown in Figure 9, in the pulse emission period, according to the corresponding time window polling in turn, control SPAD0 to turn on, control SPAD0 to turn off (control SPAD1 to turn on), control SPAD1 to turn off (control SPAD2 to turn on), control SPAD2 to turn off (control SPAD3 to turn on) , control SPAD3 off (control SPAD4 on), control SPAD4 off.

Through the above method, in each pulse emission period, each photoelectric detection unit to be polled is only enabled within the time window in which the photoelectric detection unit may detect the laser spot of the corresponding distance, so as to avoid wasting exposure time and reduce the The chance of detecting ambient light.

Step 503: Obtain the depth information of the laser spot at the current scanning angle according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period.

Combined with the foregoing step 502, when the photodetection unit is turned on, it is possible to collect signal light or ambient light. In practical applications, among the multiple photodetection units that are turned on by polling in a pulse emission period for detecting a certain laser spot, only one photoelectric detection unit detects the laser spot, and the photoelectric detection unit is hereinafter referred to as Target photodetector unit. It can be understood that, as the scanning angle changes, the target photodetection unit also changes. The target photodetection unit detects signal light (or signal light + ambient light), and the remaining photodetection units detect ambient light.

In order to obtain the depth image of the target object, the specific depth information of the laser spot detected by the target photoelectric detection unit. The implementation process is described below:

The direct flight time histogram corresponding to the current scanning angle is generated according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period under the current scanning angle. The horizontal axis of the direct flight time histogram represents time, and the vertical axis represents the count value. Figure 10 is a schematic diagram of a direct flight time histogram. The time corresponding to the column with the highest count value can be obtained by finding the peak in the histogram, and this time is taken as the flight time corresponding to the laser spot at the current scanning angle. According to the flight time and the corresponding relationship between flight time and distance, such as formula (6), the flight time obtained from the histogram in the previous step is substituted into formula (6), and the distance information of the laser spot at the current scanning angle can be obtained. The distance information represents the depth information of the laser spot detected by the target photoelectric detection unit.

It should be noted that, steps 501 to 503 are all executed cyclically.

Step 504: After the target object is scanned, the depth information of the laser spot at each scanning angle is spliced to obtain a super-resolution depth image of the target object.

Taking one-dimensional line scanning as an example, every time the scanning angle is changed, the scanning position of the target object changes, that is, the position where the same laser beam transmits to the target object changes. In addition, the position of the superdivision pixel receiving the same laser spot on the photoelectric sensor changes laterally, and the change scale is one superdivision pixel.

As described in step 503, the depth information of the laser spot is obtained at each scanning angle, so the complete super-resolution of the target object can be obtained by splicing according to the positional relationship between the super-resolution pixels receiving the laser spot at each scanning angle rate depth image.

The above is the depth imaging method provided by the embodiment of the present application. In the method, the target object is scanned at different scanning angles, and laser pulses are emitted at each scanning angle with a pulse emission period; in each pulse emission period, the photoelectric detection unit on the photoelectric sensor is polled and controlled to be turned on and off; the photoelectric sensor includes: A plurality of photoelectric detection units, each photoelectric detection unit is divided into a plurality of super-divided pixels according to the size of the laser spot; according to the electrical signals provided by each photoelectric detection unit that is turned on by polling in the pulse emission period, the laser spot at the current scanning angle is obtained. After scanning the target object, the depth information of the laser spot at each scanning angle is spliced to obtain the super-resolution depth image of the target object.

Since the photoelectric detection unit is turned on by polling in each pulse emission period, the cumulative exposure time of the photoelectric detection unit on the photoelectric sensor is greatly shortened compared with the time-sharing opening of the photoelectric detection unit, which in turn can reduce power consumption and improve frame rate. and depth imaging speed. In addition, compared with the method of fully turning on the photodetector units at the same time, the polling-on method ensures that the photodetector units that are turned on at a certain time will not be interfered by other adjacent photodetector units, and the converted signal has a higher signal-to-noise ratio. Furthermore, ensuring a high effective signal detection probability is beneficial to improve the imaging quality of the depth image of the target object.

In the polling on mode, the time window that each photoelectric detection unit is enabled in a pulse emission period is precisely controlled, and the photons that may be returned at each distance are accurately received, and the interference of ambient light is reduced as much as possible. In one pulse emission period, the number of ambient light photons collected during the time when multiple photodetector units are turned on is equivalent to the number of ambient light photons collected during the time when a single photodetector unit is always turned on in the prior art , and the detection of signal light is equivalent to fully opening all photoelectric detection units, so the signal quantity will not be lost, and the system power consumption will be greatly saved.

When using a laser to scan a target object, in order to improve the scanning efficiency, multiple laser beams can be projected to the target object at the same time. These laser beams may be parallel or non-parallel. In the following description, parallel output is taken as an example for description.

Referring to FIG. 11 , the figure is a schematic diagram of dot matrix emission parallax. The solid circles in Figure 11 represent different laser spots in the TX field of view, and the open circles represent different laser spots in the RX field of view. With reference to Fig. 11, it is not difficult to see that if there are too many photodetector units involved in a single polling control, it is possible to obtain optical signals of two or more valid laser spots after polling. At this time, it is easy to mistake the weak optical signal as a noise signal of ambient light and ignore it. To avoid this problem, the photodetector units to be polled based on a single laser spot can be determined first before polling.

Another depth imaging method provided by the embodiments of the present application will be described below with reference to the embodiments and the accompanying drawings.

Referring to FIG. 12 , which is a flowchart of another depth imaging method provided by an embodiment of the present application. As shown in Figure 12, the depth imaging method includes:

Step 1201 : Scan the target object at different scanning angles, and emit laser pulses to the target object in a dot matrix projection manner for multiple pulse emission cycles at each scanning angle, so as to form multiple laser spots on the photoelectric sensor at the same time.

The multiple laser spots formed at different scanning angles are shown on the left side of FIG. 7 and the right side of FIG. 7 , respectively.

Step 1202 : Obtain the minimum interval between two adjacent laser spots in the field of view of the laser according to the baseline distance between the laser and the photoelectric sensor, the minimum detection distance of the photoelectric sensor, the lateral field angle and lateral resolution of the photoelectric detection unit.

The baseline distance between the laser and the photoelectric sensor can be determined by pre-calibration. The detection capability of each photoelectric sensor includes the maximum detection distance and the minimum detection distance. The minimum detection distance can be obtained from the factory parameters of the photoelectric sensor, or obtained through multiple tests. The lateral field of view and lateral resolution of the photodetection unit can also be obtained from the factory parameters.

In the embodiment of the present application, in order to determine the photoelectric detection unit to be polled corresponding to each laser spot in each pulse emission period and prevent more than one laser spot from being detected by one round of polling, first calculate the field of view of the laser (TX field of view). ) is the minimum interval between two adjacent laser spots. For each laser spot, the photodetection units to be polled are determined with a minimum interval.

The formula for calculating the minimum interval between two adjacent laser spots in the field of view of the laser is as follows:

In formula (9), N _spot represents the minimum interval between two adjacent laser spots in the TX field of view, d _baseline represents the baseline distance between the laser and the photoelectric sensor, Dist _min represents the minimum detection distance of the photoelectric sensor, and FOV _h represents the photoelectric detection unit The lateral field of view, N _h represents the lateral resolution of the photodetection unit.

is the round-up symbol, and in the round-up symbol is the maximum offset corresponding to the minimum detection distance. In the embodiment of the present application, 1 is added to the result of rounding up the maximum offset, and the final value obtained by this is used as the minimum interval between two adjacent laser spots in the laser field of view. The minimum interval is represented by the number of photodetector units.

Step 1203: Determine the photodetection unit to be polled corresponding to each laser spot in each pulse emission period according to the photodetection unit without parallax and the minimum interval.

For example, N _spot = 4 means that four consecutive photodetector units are used as the photodetector units to be polled corresponding to a certain laser spot, and the following four photodetector units are to be used as the photodetector units corresponding to adjacent laser spots. Polled photodetector unit. Taking FIG. 7 as an example, the minimum interval is 4. In the figure, the photoelectric detection units 701 to 704 are the photoelectric detection units to be polled corresponding to the laser spot 001, and the photoelectric detection units 705 to 708 are the photoelectric detection units to be polled corresponding to the laser spot 002. detection unit.

_{According to the minimum interval N spot} calculated by formula (9), it _{is determined that the N spot} photoelectric detection units to be polled corresponding to a certain laser spot will not detect more than one laser spot accumulated in one pulse emission period. In this way, the difficulty of determining the signal light is reduced, the missed detection of the signal light is avoided, and the pertinence and accuracy of the signal light detection are enhanced.

Step 1204: Determine the time window corresponding to each photoelectric detection unit to be polled.

For the implementation of this step, refer to formulas (7) to (8) and FIG. 8 .

Step 1205: Control each photoelectric detection unit to be polled on and off according to the time window polling.

To facilitate understanding of the implementation of this step, please refer to FIG. 9 .

Step 1206: Generate a direct flight time histogram corresponding to the current scanning angle according to the electrical signals provided by each photoelectric detection unit that is turned on by polling in the pulse emission period under the current scanning angle.

When the target object is projected by S laser beams in the current pulse emission period (S is an integer greater than 1), then S direct flight time histograms can be generated. The time corresponding to the maximum count value of each direct flight histogram is the flight time of the corresponding laser spot. An example of a histogram can be found in FIG. 10 .

Step 1207 : find a peak in the direct flight time histogram, and determine the flight time corresponding to the laser spot at the current scanning angle.

Step 1208: According to the flight time and the corresponding relationship between the flight time and the distance, obtain the distance information of the laser spot at the current scanning angle as the depth information of the laser spot.

The implementation manners of the above steps 1207 to 1208 have been described in the foregoing embodiments, and will not be repeated here. See formula (6) for the calculation method of obtaining laser spot depth information through time-of-flight.

In order to successfully stitch the depth information of the laser spot at each scanning angle to form a complete super-resolution depth image including the target object, the following steps can be used to determine the target photoelectric detection unit where the super-resolution pixel that receives the laser beam reflected from the laser spot is located. and the position of the super-divided pixel in the target photodetection unit (ie, the super-divided position).

Step 1209: Obtain the offset corresponding to the distance information according to the correspondence between the offset and the distance.

Based on formula (3), the offset expression corresponding to the distance information of the laser spot at the current scanning angle can be obtained:

In formula (10), d _obj represents the distance information of a certain laser spot under the current scanning angle, and σ _obj represents the offset corresponding to the distance information.

The offset calculated according to formula (10) usually includes an integer part and a fractional part. Wherein, the integer part indicates the number of photodetection units offset by the target photodetector unit relative to the photodetector unit without parallax, and the target photodetector unit is the photodetector unit where the laser spot is located. The fractional part of the offset indicates the super-resolution position of the received laser spot in the target photodetector unit.

Taking σ _obj =3.25 as an example, it means that the target photodetection unit is shifted by 3 photodetection units relative to the photodetection unit without parallax. In order to accurately determine the super-divided pixel on the target photodetection unit that receives the laser spot, the following step 1210 needs to be performed.

Step 1210: According to the offset and the superdivision multiple of the photoelectric sensor, determine the superdivision pixel of the laser spot detected in the target photoelectric detection unit under the current scanning angle, so as to construct the corresponding relationship between the depth information and the superdivision pixel.

The following formula expresses how to determine the super-resolution pixel that receives the laser spot:

In formula (11), l _rx represents the ordinal number of the super-resolution pixels in the target photodetection unit that detect the laser spot, N _supres represents the super-resolution multiple of the photoelectric sensor, and σ _obj represents the offset corresponding to the distance information of the laser spot.

to round down notation,

is the round-up symbol. As shown in FIG. 7 , one photodetection unit includes 4 superdivision pixels laterally, so the superdivision multiple is 4. l The value of _rx is an integer between _{1 and N supres.} When N _supres =4, then l _rx =1,2,3,4. Taking σ _obj =3.25 as an example, according to formula (11), the ordinal number of the super-divided pixel that detects the laser spot is calculated to be 1, which means that the super-divided pixel that receives the laser spot is the No. 1 pixel of the target photodetection unit along the moving direction of the laser spot. 1 superpixel.

In this way, the correspondence between the first super-divided pixel of the target photodetection unit along the moving direction of the laser spot and the depth information of the laser spot is constructed. In the scenario of emitting laser pulses to the target object in the form of dot matrix projection, the correspondence between multiple super-divided pixels and the depth information of the laser spot can be obtained for each scanning angle. It should be noted that, steps 1201 to 1210 are performed cyclically. Therefore, by cyclically executing steps 1201 to 1210, the corresponding relationship of the laser spot depth information of each super-divided pixel that has received the laser spot can be constructed.

Step 1211 : After the target object is scanned, the depth information of the laser spot at each scanning angle is stitched together by using the corresponding relationship between the depth information and the super-divided pixels.

Taking FIG. 7 as an example, the depth information of the laser spot 001 in the first super-divided pixel of the photodetection unit 701 is associated with the depth information of the second super-divided pixel in the photodetection unit 701 according to the positions of the two super-divided pixels. stitched together, and so on.

In the above embodiment, the minimum interval is obtained in step 1202, and then the photoelectric detection unit to be polled corresponding to each laser spot in each pulse emission period is determined based on the minimum interval in step 1203, which reduces the difficulty of determining the signal light , to avoid missed detection of signal light, and enhance the pertinence and accuracy of signal light detection. Through step 1210, the corresponding relationship between the depth information and the super-divided pixels is constructed, so as to improve the splicing efficiency of the depth information of each position of each target object, and improve the speed of depth imaging.

Based on the depth imaging method provided by the foregoing embodiments, correspondingly, the present application also provides a depth imaging system. The system is described below with reference to the embodiments and the accompanying drawings.

System example:

Referring to FIG. 13 , this figure is a schematic structural diagram of a depth imaging system provided by an embodiment of the present application. As shown in Figure 13, the depth imaging system includes:

Laser 1301, controller 1302, gating element 1303, photoelectric sensor 1304, time-to-digital converter TDC and processor 1305;

The controller 1302 is connected to the laser 1301 . The controller 1302 is used to control the laser 1301 to scan the target object at different scanning angles, and emit laser pulses with a pulse emission period under each scanning angle.

In a possible implementation manner, the controller 1302 sets the pulse emission period of the laser 1301, and the laser 1301 emits laser pulses in the above pulse emission period according to the pulse control signal provided by the controller 1302.

In another possible implementation, the controller 1302 may control the scanning angle of the laser 1301 . When the controller 1302 transmits a scan angle adjustment signal to the laser 1301, the laser 1301 adjusts the scan angle according to the scan angle adjustment signal.

The photosensor 1304 includes a plurality of photodetection units, and each photodetector unit is divided into a plurality of super-divided pixels according to the size of the laser spot. The photodetection unit can be SPAD or APD. The specific type of the photodetection unit is not limited here. In Fig. 13, only SPAD 1, SPAD 2, SPAD 3...SPADN are used as examples to represent different photoelectric detection units.

The gate switch 1303 connects all photodetection units of the photoelectric sensor 1304 . The gate switch 1303 is used to poll and control the photodetection unit on the photoelectric sensor 1304 to turn on and off in each pulse emission period. The turned-on photodetection unit is used to receive the light signal reflected by the target object (ie, the reflected laser beam), and convert the light signal into an electrical signal.

The controller 1302 and the processor 1305 are respectively connected to the time-to-digital converter TDC.

The time-to-digital converter TDC is also connected to each photodetection unit of the photoelectric sensor 1304 through the gate switch 1303 . The time-to-digital converter TDC is used to obtain the flight according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period (also provides the time when the optical signal is detected) and the emission time of each pulse under the current scanning angle. time, and convert the flight time into a count value.

The processor 1305 is used to form the direct flight time histogram corresponding to the current scanning angle according to the count value converted by the time-to-digital converter TDC and the electrical signal; obtain the depth information of the laser spot under the current scanning angle according to the direct flight time histogram; After the laser 1301 scans the target object, the depth information of the laser spot at each scanning angle is spliced to obtain a super-resolution depth image of the target object.

The above is the depth imaging system provided by the embodiment of the present application. Since the photoelectric detection unit is turned on by polling in each pulse emission period, the cumulative exposure time of the photoelectric detection unit on the photoelectric sensor is greatly shortened compared with the time-sharing opening of the photoelectric detection unit, which in turn can reduce power consumption and improve frame rate. and depth imaging speed. In addition, compared with the method of fully turning on the photodetector units at the same time, the polling-on method ensures that the photodetector units that are turned on at a certain time will not be interfered by other adjacent photodetector units, and the converted signal has a higher signal-to-noise ratio. Furthermore, a higher probability of effective signal detection is ensured, which is beneficial to improve the imaging quality of the depth image of the target object.

Optionally, the depth imaging system may further include a memory connected to the processor for storing the direct time-of-flight histogram.

The embodiments of the present application provide an example implementation of the above laser. Referring to Figure 14, the figure illustrates the structure of a laser. As shown in FIG. 14 , the laser includes: a laser light source 13011 , a collimating lens 13012 , a deflection mirror 13013 , a beam splitting element 13014 and a driving device 13015 .

Wherein, the laser light source 13011 is used to emit a laser beam, and the laser beam includes laser pulses emitted according to the pulse emission period;

The collimating lens 13012 is used to collimate the laser beam and send it to the deflection mirror;

The deflection mirror 13013 is connected to the driving device 13015 for reflecting the laser beam from the collimating lens 13012 to the beam splitting element 13014; during the period, the deflection mirror 13013 is periodically deflected by the driving device 13015. The deflection mirror 13013 is mechanically and/or electrically connected to the driving device 13015 .

The beam splitting element 13014 is used to split the received laser beam into multiple beams, and then project the multiple laser beams to the target object. According to the design of the light splitting element 13014, the projected multiple laser beams may be parallel to each other, or may form an included angle.

When the controller 1302 controls the laser shown in FIG. 14 to adjust the scanning angle, it may specifically send the scanning angle adjustment signal to the driving device 13015, and then the driving device 13015 drives the deflection mirror 13013 to rotate according to the scanning angle adjustment signal.

It should be understood that, in this application, "at least one (item)" refers to one or more, and "a plurality" refers to two or more. "And/or" is used to describe the relationship between related objects, indicating that there can be three kinds of relationships, for example, "A and/or B" can mean: only A exists, only B exists, and both A and B exist at the same time. , where A and B can be singular or plural. The character "/" generally indicates that the associated objects are an "or" relationship. "At least one item(s) below" or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (a) of a, b or c, can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c" ", where a, b, c can be single or multiple.

The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

A depth imaging method, comprising:

Scan the target object at different scanning angles, and emit laser pulses with pulse emission cycles at each scanning angle;

In each pulse emission period, the photoelectric detection unit on the photoelectric sensor is polled to be turned on and off; the photoelectric sensor includes a plurality of photoelectric detection units, and each photoelectric detection unit is divided into a plurality of super-divided pixels according to the size of the laser spot;

Obtain the depth information of the laser spot at the current scanning angle according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period;

After the target object is scanned, the depth information of the laser spot at each scanning angle is spliced to obtain a super-resolution depth image of the target object.
The depth imaging method according to claim 1, wherein the polling and controlling the photodetection unit on the photoelectric sensor to be turned on and off in each pulse emission period specifically includes:

Determine the photodetector units to be polled in each pulse emission period;

determining a time window corresponding to each of the photodetection units to be polled;

Each of the photodetection units to be polled is polled and controlled to be turned on and off according to the time window.
The depth imaging method according to claim 2, wherein the transmitting laser pulses at each scanning angle with a pulse emission period, specifically comprising:

The laser pulses are emitted to the target object in a dot matrix projection manner for a plurality of the pulse emission periods at each scanning angle, so as to simultaneously form a plurality of laser light spots on the photoelectric sensor;

The determining of the photoelectric detection units to be polled in each pulse emission period specifically includes:

Obtain the minimum interval between two adjacent laser spots in the field of view of the laser;

According to the photodetection unit without parallax and the minimum interval, the photodetection unit to be polled corresponding to each laser spot in each pulse emission period is determined.
The depth imaging method according to claim 3, wherein the obtaining the minimum interval between two adjacent laser spots in the field of view of the laser specifically comprises:

According to the baseline distance between the laser and the photoelectric sensor, the minimum detection distance of the photoelectric sensor, the lateral field angle and lateral resolution of the photoelectric detection unit, two adjacent lasers in the field of view of the laser are obtained Minimum spacing of the spots.
The depth imaging method according to claim 2, wherein the determining a time window corresponding to each photoelectric detection unit to be polled specifically includes:

determining the offset range of each of the photodetection units to be polled relative to the photodetection units without parallax;

According to the offset range and the corresponding relationship between the offset and the distance, determine the corresponding distance range when the laser spot falls on each of the photoelectric detection units to be polled;

According to the distance range and the corresponding relationship between the distance and the time delay, determine the time-of-flight range in which each photoelectric detection unit to be polled can receive the laser spot; the time-of-flight range is used as the time window.
Depth imaging method according to claim 1, is characterized in that, described according to the electric signal that each photoelectric detection unit that turns on polling in the pulse emission period provides, obtains the depth information of the laser spot under the current scanning angle, specifically includes:

Generate a direct flight time histogram corresponding to the current scanning angle according to the electrical signal provided by each photoelectric detection unit that is turned on by polling in the pulse emission period under the current scanning angle;

Find peaks in the direct flight time histogram, and determine the flight time corresponding to the laser spot at the current scanning angle;

According to the flight time and the corresponding relationship between the flight time and the distance, the distance information of the laser spot at the current scanning angle is obtained as the depth information of the laser spot.
The depth imaging method according to claim 6, wherein after obtaining the distance information of the laser spot at the current scanning angle as the depth information of the laser spot, the method further comprises:

The offset corresponding to the distance information is obtained according to the correspondence between the offset and the distance; the integer part of the offset indicates the number of photodetection units offset by the target photodetection unit relative to the photodetection unit without parallax, The target photoelectric detection unit is the photoelectric detection unit where the laser spot is located, and the fractional part of the offset indicates the super-divided position where the laser spot is received in the target photoelectric detection unit;

According to the offset and the superdivision multiple of the photoelectric sensor, determine the superdivision pixel at which the laser spot is detected in the target photoelectric detection unit under the current scanning angle, so as to construct the relationship between the depth information and the superdivision pixel. Correspondence;

After the scanning of the target object is completed, the depth information of the laser spot at each scanning angle is spliced, which specifically includes:

After the target object is scanned, the depth information of the laser spot at each scanning angle is stitched together by using the corresponding relationship between the depth information and the super-divided pixels.
The depth imaging method according to claim 1, wherein the scanning the target object with different scanning angles specifically includes:

The laser light path is adjusted before scanning the target object at the next scanning angle to form the next scanning angle.
A depth imaging system, comprising: a laser, a controller, a gating element, a photoelectric sensor, a time-to-digital converter and a processor; the controller is connected to the laser; the photoelectric sensor includes a plurality of photodetectors Each photoelectric detection unit is divided into a plurality of super-divided pixels according to the size of the laser spot; the gating switch is connected to all the photoelectric detection units of the photoelectric sensor; the controller and the processor are respectively connected to the the time-to-digital converter; the time-to-digital converter is also connected to the photodetection unit through the gate switch;

The controller is used to control the laser to scan the target object with different scanning angles, and emit laser pulses with a pulse emission period under each scanning angle;

The gate switch is used to poll and control the photodetection unit on the photoelectric sensor to turn on and off in each pulse emission period; the turned-on photodetection unit is used to receive the light signal reflected by the target object, and to converting the optical signal into an electrical signal;

The time-to-digital converter is used to obtain the flight time according to the electrical signals provided by each photoelectric detection unit that is turned on by polling in the pulse emission period and the emission time of each pulse under the current scanning angle, and convert the flight time into counts value;

The processor is configured to form a direct time-of-flight histogram corresponding to the current scanning angle according to the count value converted by the time-to-digital converter and the electrical signal; Depth information of the laser spot; after the laser scans the target object, the depth information of the laser spot at each scanning angle is spliced to obtain a super-resolution depth image of the target object.
The depth imaging system according to claim 9, wherein the laser comprises: a laser light source, a collimating lens, a deflection mirror, a beam splitting element and a driving device;

The laser light source is used to emit a laser beam, and the laser beam includes laser pulses emitted according to a pulse emission period;

the collimating lens is used for collimating and sending the laser beam to the deflecting mirror;

The deflecting mirror is connected with the driving device, and is used for reflecting the laser beam from the collimating lens to the beam splitting element; during the period, the deflecting mirror is periodically deflected by the driving device;

The beam splitting element is used for splitting the received laser beam into multiple beams, and then projecting the multiple laser beams to the target object.