WO2021077358A1

WO2021077358A1 - Ranging method, ranging device, and computer-readable storage medium

Info

Publication number: WO2021077358A1
Application number: PCT/CN2019/113038
Authority: WO
Inventors: 叶天翔; 罗鹏飞; 刘维辉; 唐样洋
Original assignee: 华为技术有限公司
Priority date: 2019-10-24
Filing date: 2019-10-24
Publication date: 2021-04-29
Also published as: CN114556048A; CN114556048B

Abstract

A ranging device and a ranging method applied to the ranging device. The ranging device comprises a transmitter and a receiver. The ranging method comprises: determining a high-frequency exposure time and a low-frequency exposure time; when determining the low-frequency exposure time, combining low-frequency pixels and determining the low-frequency exposure time according to the number of pixels of each combination (S11); carrying out high-frequency exposure according to the high-frequency exposure time so as to obtain a high-frequency exposure image, and carrying out low-frequency exposure according to the low-frequency exposure time so as to obtain a low-frequency exposure image (S12); and calculating the distance between a ranging device and a target object according to the high-frequency exposure image and the low-frequency exposure image (S13). The described method may reduce system power consumption while ensuring accuracy.

Description

Distance measuring method, distance measuring device and computer readable storage medium

Technical field

This application relates to the technical field of time-of-flight ranging, in particular to a ranging method, a ranging device, and a computer-readable storage medium.

Background technique

The basic principle of TOF (Time of Flight) is to continuously emit light pulses to the target object, and then use the sensor to receive the light signal returned from the target object, and obtain the target object distance by detecting the flight time of the light pulse.

As shown in FIG. 1, it is a basic principle diagram of time of flight (ToF) camera ranging. The ToF camera 100 includes an active light source emitter 101 and a ToF sensor 102. The active light source emitter 101 may be a light emitting diode (LED), a vertical cavity surface emitting laser (VCSEL), or the like. The active light source transmitter 101 emits a continuous sine wave laser signal to the target object (as shown by curve 1 in FIG. 1). After the laser signal reaches the target object and is reflected by the target object (as shown by curve 2 in Figure 1), it is received by the ToF sensor 102. By comparing the phase difference φ between the emitted laser signal and the received laser signal, the target can be calculated The distance of the object from the ToF camera and the intensity of the received laser signal.

In the existing TOF ranging technology, in order to extend the measurement distance without affecting the accuracy, a multi-frequency technology can be used to increase the measurement distance without reducing the modulation frequency. Multi-frequency technology is to add one or more frequency modulation waves to mix. Each modulation wave measurement has a different ambiguous distance. The true distance is the value measured by multiple frequency modulation waves. The corresponding frequency of this value is The greatest common divisor of multiple frequencies is called the hitting frequency. Among them, the lower the hit frequency, the longer the measurement distance.

In multi-frequency technology, dual-frequency ranging is often used. Dual-frequency ranging refers to the use of two modulated signals of different frequencies for ranging, and exposure of the modulated signals of each frequency for different times. For example, when a high-frequency modulation signal and a low-frequency modulation signal are used for ranging, the high-frequency modulation signal can be exposed separately (referred to as high-frequency exposure) to obtain a high-frequency exposure image, and the low-frequency modulation signal can be exposed (referred to as Low-frequency exposure) to obtain low-frequency exposure images. Among them, high frequency and low frequency are relative terms. In dual-frequency ranging, the higher frequency is called high frequency, and the lower frequency is called low frequency. In the existing TOF camera applications, the power consumption of the TOF camera is proportional to the exposure (working) time. At present, in order to ensure the accuracy of the ranging, more exposure time is allocated to the low-frequency modulation signal to ensure the signal-to-noise ratio of the low-frequency exposure image, thereby ensuring that the correct phase unwrapping frequency coefficient is obtained without affecting the ranging accuracy. Among them, the phase unwrapping coefficient is used to restore the true phase delay of each frequency, which can be obtained by the unwrapping algorithm. However, due to more time allocated for low frequency exposure, the power consumption of the system is higher.

Summary of the invention

The embodiments of the present application provide a ranging method and a ranging device, which can reduce power consumption while the ranging accuracy is unchanged.

In the first aspect, an embodiment of the present application discloses a ranging method, including:

Determine the high-frequency exposure time and the low-frequency exposure time; wherein, when determining the low-frequency exposure time, combine processing of low-frequency pixels, and determine the low-frequency exposure time according to the number of pixels in each combination;

Performing high-frequency exposure according to the high-frequency exposure time to obtain a high-frequency exposure image; and performing low-frequency exposure according to the low-frequency exposure time to obtain a low-frequency exposure image;

The distance between the distance measuring device and the target object is calculated according to the high-frequency exposure image and the low-frequency exposure image.

Among them, high frequency and low frequency refer to the frequency of the modulation signal emitted by the ranging device, which is relatively speaking. For example, in dual-frequency ranging technology, the higher frequency is called high frequency, and the lower frequency It is called low frequency.

In the distance measurement method in the embodiment of the present application, since the low-frequency pixels are combined when determining the low-frequency exposure time, the signal-to-noise ratio of the low-frequency exposure image can be improved. Therefore, even if less time is allocated to When the signal is modulated at low frequency, the correct phase unwrapping coefficient can also be ensured, thereby ensuring the accuracy of ranging. In this way, the purpose of reducing system power consumption is achieved under the premise of ensuring accuracy.

In one embodiment, in order to determine the high-frequency exposure time and the low-frequency exposure time quickly, the determining the high-frequency exposure time and the low-frequency exposure time includes: performing a pre-exposure for a preset time to obtain the pre-exposure Image, and the high-frequency exposure time and the low-frequency exposure time are respectively determined according to the strength of the reference signal received by the pre-exposure image within the preset time.

In one embodiment, the determining the high-frequency exposure time and the low-frequency exposure time separately according to the signal intensity received by the pre-exposure image within the preset time includes: obtaining the pre-exposure The strength of the reference signal received by the image within the preset time; the strength of the high-frequency target signal and the strength of the low-frequency target signal are determined respectively according to the strength of the reference signal; the strength of the high-frequency target signal is determined according to the reference signal strength, the strength of the high-frequency target signal, and the The preset time is used to calculate the high-frequency exposure time; and the low-frequency exposure time is calculated according to the reference signal strength, the low-frequency target signal strength, the number of pixels in each combination, and the preset time; wherein, The low-frequency exposure time is inversely proportional to the number of pixels in each combination. In this way, the low-frequency exposure time can be quickly calculated according to the number of pixels in each combination, which further improves the calculation efficiency of the high-frequency exposure time and the low-frequency exposure time.

In a specific embodiment, the relationship between the variance or standard deviation of the measured distance noise at different frequencies and the received signal strength is combined to determine the high-frequency target signal strength and the low-frequency target signal strength. Specifically, when the distance noise variance corresponding to the reference signal strength is determined by the relationship curve between the distance noise variance or standard deviation and the received signal strength, the signal strength corresponding to the appropriate distance noise variance or standard deviation should be selected as the target Signal strength. Wherein, the appropriate distance noise variance or standard deviation means that the target signal strength corresponding to the distance noise variance meets the requirements of ranging accuracy and the correct phase unwrapping coefficient can be obtained.

In an embodiment, a specific formula for calculating the low-frequency exposure time is as follows:

Among them, A _2L represents the low-frequency target signal strength, A ₁ represents the reference signal strength, b is the number of pixels in each combination, and T ₁ is the preset time.

In an embodiment, the reference signal intensity is the average signal intensity of all pixels of the pre-exposure image; or, the reference signal intensity is the average signal intensity of the characteristic pixels of the pre-exposure image; wherein, The characteristic pixels represent pixels corresponding to the characteristic regions of the pre-exposure image. In this way, the calculation accuracy of the high-frequency exposure time and the low-frequency exposure time can be improved.

In one embodiment, the calculating the distance between the distance measuring device and the target object based on the high-frequency exposure image and the low-frequency exposure image includes: calculating the high-frequency value of each pixel in the high-frequency exposure image Phase delay information, and calculating the low-frequency phase delay information of each pixel combined in the low-frequency exposure image; up-sampling the low-frequency phase delay information of each pixel combined in the low-frequency exposure image to obtain The high-frequency exposure image is a low-frequency exposure image with the same resolution; the high-frequency unwrapping coefficient of each pixel is calculated according to the high-frequency phase delay information of each pixel and the low-frequency phase delay information of each pixel; according to the height of each pixel The frequency unwrapping coefficient and the high-frequency phase delay information of each pixel calculates the distance between each pixel and the subject that the pixel is exposed to.

In this embodiment, since the low-frequency phase delay information of each pixel combined in the low-frequency exposure image is up-sampled to obtain the low-frequency exposure image with the same resolution as the high-frequency exposure image, the combination can be processed Restore the subsequent images to improve the accuracy of subsequent ranging.

In one embodiment, when performing high-frequency exposure or low-frequency exposure, a continuous wave modulation mode or a pulse wave modulation mode is used, and different modulation modes can be used according to specific requirements, which improves the applicability of the ranging method.

In one embodiment, a continuous wave modulation mode and chopping technique are used when performing high-frequency exposure. In this way, the mismatch caused by the capacitance, the set voltage, and the background light at the charge collection site during high-frequency modulation can be eliminated, and the accuracy of the depth information can be improved.

In one embodiment, the continuous wave modulation mode is used for high frequency exposure, and the continuous wave modulation mode or pulse wave modulation mode is used for low frequency exposure. In this way, the power consumption of the system can be further reduced.

In one embodiment, during high-frequency exposure or low-frequency exposure, adjacent pixels are exposed in different phases to further reduce system power consumption.

In the second aspect, an embodiment of the present application discloses a distance measuring device, which includes a determination module, an exposure module, and a calculation module. The determining module is used to determine the high-frequency exposure time and the low-frequency exposure time, perform combination processing on low-frequency pixels when determining the low-frequency exposure time, and determine the low-frequency exposure time according to the number of combinations. The exposure module is configured to perform high-frequency exposure according to the high-frequency exposure time to obtain a high-frequency exposure image, and perform low-frequency exposure according to the low-frequency exposure time to obtain a low-frequency exposure image. The calculation module is used to calculate the distance between the distance measuring device and the target object according to the high-frequency exposure image and the low-frequency exposure image.

In the distance measuring device in the embodiment of the present application, since the determining module performs a combination process on the low-frequency pixels when determining the low-frequency exposure time, the signal-to-noise ratio of the low-frequency exposure image can be improved. Therefore, even when less time is allocated When giving low-frequency modulation signals, it can also ensure that the correct phase unwrapping coefficient is obtained, thereby ensuring the accuracy of ranging. In this way, the purpose of reducing system power consumption is achieved under the premise of ensuring accuracy.

In one embodiment, the determining module is specifically configured to perform pre-exposure according to a preset time to obtain a pre-exposed image, and according to the reference signal received by each pixel of the pre-exposed image within the preset time The intensity determines the high-frequency exposure time and the low-frequency exposure time respectively.

In an embodiment, the determining module includes an acquiring unit and a determining unit. The acquiring unit is configured to acquire the reference signal intensity received by the pre-exposure image at the preset time. The determining unit is used to determine the high-frequency target signal strength and the low-frequency target signal strength respectively according to the reference signal strength. The determining unit is further configured to calculate the high-frequency exposure time according to the reference signal strength, the high-frequency target signal strength, and the preset time; and, according to the reference signal strength and the low-frequency target signal strength Calculating the low-frequency exposure time based on the determined number of combinations and the preset time; wherein the low-frequency exposure time is inversely proportional to the number of pixels in each combination.

In a specific implementation, the determining unit is specifically configured to determine the high-frequency target signal strength and the low-frequency target signal strength in combination with the relationship curve of the measured distance noise variance or standard deviation of different frequencies and the received signal strength. Specifically, when the distance noise variance corresponding to the reference signal strength is determined by the relationship curve between the distance noise variance or standard deviation and the received signal strength, the signal strength corresponding to the appropriate distance noise variance or standard deviation should be selected as the target Signal strength. Wherein, the appropriate distance noise variance or standard deviation means that the target signal strength corresponding to the distance noise variance meets the requirements of ranging accuracy and the correct phase unwrapping coefficient can be obtained.

In an implementation manner, a specific formula used by the determining unit to calculate the low-frequency exposure time is as follows:

Among them, A2L represents the low-frequency target signal strength, A1 represents the reference signal strength, b is the number of pixels in each combination, and T1 is the preset time.

In an embodiment, the reference signal intensity is the average signal intensity of all pixels of the pre-exposure image; or, the reference signal intensity is the average signal intensity of the characteristic pixels of the pre-exposure image; wherein, The characteristic pixels represent pixels corresponding to the characteristic regions of the pre-exposure image.

In an embodiment, the calculation module includes a calculation unit and a sampling unit. The calculation unit is configured to calculate the high-frequency phase delay information of each pixel in the high-frequency exposure image, and calculate the low-frequency phase delay information of each pixel combined in the low-frequency exposure image. The sampling unit is used for up-sampling the low-frequency phase delay information of each pixel combined in the low-frequency exposure image to obtain a low-frequency exposure image with the same resolution as the high-frequency exposure image. The calculation unit is also used to calculate the high-frequency unwrapping coefficient of each pixel according to the high-frequency phase delay information of each pixel and the low-frequency phase delay information of each pixel; and according to the high-frequency unwrapping coefficient of each pixel Calculate the distance between each pixel and the subject when the pixel is exposed by using the high-frequency phase delay information of each pixel.

In a third aspect, the present application provides a distance measuring device, including a transmitter, a receiving sensor, and a processor. The processor is respectively coupled with the transmitter and the receiver. The processor is configured to execute the method described in the first aspect and any possible implementation manner in the first aspect.

In a fourth aspect, the present application provides a computer-readable storage medium, the computer-readable storage medium stores a computer program, the computer program includes at least one piece of code, the at least one piece of code can be executed by a computer, to control the computer to execute such as the first One aspect and the method described in any possible implementation of the first aspect.

In a fifth aspect, the present application provides a computer program product containing instructions. When the computer program product is run on an electronic device, the electronic device is caused to perform the operations described in the first aspect and any one of the possible implementation manners in the first aspect. method.

Description of the drawings

Fig. 1 is a schematic diagram of the ranging principle of a TOF camera in the background art.

FIG. 2 is a schematic structural diagram of a distance measuring device in an embodiment of the application.

FIG. 3 is a schematic structural diagram of a distance measuring device in another embodiment of the application

FIG. 4 is a flowchart of a distance measurement method in an embodiment of this application.

Fig. 5 is a detailed flowchart of step S11.

Fig. 6 is a detailed flowchart of step S13.

Fig. 7 is a functional block diagram of a distance measuring device in an embodiment of the application.

Figure 8 is a diagram of the sub-function modules of the determining module.

Figure 9 is a diagram of the sub-function modules of the computing module.

Detailed ways

The embodiments of the present application provide a ranging device and a ranging method applied to the ranging device. The ranging method can reduce power consumption while the ranging accuracy is unchanged. Specifically, the distance measurement method achieves the above-mentioned functions by adjusting the proportion of the time of high-frequency exposure and low-frequency exposure, such as reducing the low-frequency exposure time by combining low-frequency pixels, thereby solving the problem of low-frequency signal-to-noise ratio. Causes the problem of phase unwrapping failure. The embodiments of the present application will be described below in conjunction with the drawings.

Please refer to FIG. 2, which is a schematic structural diagram of a distance measuring device in an embodiment of the application. The distance measuring device 100 includes a transmitter 10, a receiver 20 and a processor 30. The transmitter 10 is used to transmit optical signals. The transmitter 10 may be a light emitting diode (Light Emitting Diode, LED) or a laser diode (Laser Diode, LD). Among them, the laser has good collimation and high energy. Compared with the same number of LED lights, the laser emitter has a larger detection range and is more suitable for long-distance detection.

The receiver 20 is used to receive the light signal reflected by the target object 200. Specifically, the receiver 20 is composed of a plurality of pixels (not shown) arranged in two dimensions. The receiver 20 is used to perform a receiving operation of reflected light at each pixel, and to generate an electric charge corresponding to the light amount of the reflected light (received light amount) obtained by the light receiving operation. Wherein, the receiver 20 may include a photosensitive element, and the photosensitive element includes at least one of the following: a photodiode, an avalanche photodiode, and a charge-coupled element.

The processor 30 is configured to determine the distance between the target object 200 and the distance measuring device 100 according to the optical signal emitted by the transmitting unit 10 and the optical signal reflected by the target object 200 received by the receiving unit 20. Specifically, the processor 30 is configured to determine the phase difference between the optical signal emitted by the transmitting unit 10 and the optical signal reflected by the target object 200 received by the receiving unit 20, and determine the target object according to the phase difference The distance between 200 and the distance measuring device 100.

The processor 30 may be a central processing unit (Central Processing Unit, CPU), other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), Field-Programmable Gate Array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The processor is the control center of the distance measuring device 100, and various interfaces and lines are used to connect the entire distance measuring device. 100 parts.

The process in which the processor 30 controls the transmitter 10 to emit light signals to the target object 200, and the light signal reflected by the target object 200 is received by the receiver 20 and forms an image is called exposure.

In actual operation, the processor 30 controls the transmitter 10 to transmit an _{optical signal of a certain frequency f L} for distance detection, and allows the receiver 20 to perform the same frequency four-phase delay (0 degrees, 90 degrees, 180 degrees, 270 degrees, ) Exposure for a period of time (t _L ). After the exposure, the exposure value of the receiver 20 _{_{(DCS0 L, DCS1 L, DCS2}} L, DCS3 L) to the processor 30. Next, the processor 30 controls the transmitter 11 to transmit another _{optical signal of frequency f H} for distance detection, and allows the receiver 20 to perform the same frequency four-phase delay (0 degree, 90 degree, 180 degree, 270 degree,) exposure for a period of time. (t _H ). After the exposure, the exposure value _{_{(DCS0 H, DCS1 H, DCS2}} H, DCS3 H) receiver 20 is also transmitted to the processor 30. The processor 30 outputs a measured distance for each pixel after receiving the data of multiple exposures.

Please refer to FIG. 3, which is a schematic structural diagram of a distance measuring device 100 in another embodiment of the application. In the embodiment of the present application, different from the distance measuring device shown in FIG. 2, the distance measuring device 100 further includes a driving unit 40, a lens 50 and an A/D conversion unit 60. The driving unit 12 is connected between the processor 30 and the transmitter 10 for driving the transmitter 10 to emit light signals. The lens 50 is used to converge the light signal reflected by the target object 200. The A/D conversion unit 60 is connected between the receiver 20 and the processor 30, and is configured to perform A/D conversion on the pixel signal from the receiver 20 and output the converted pixel signal To processor 30.

The distance measurement device 100 in the embodiment of the present application uses a dual-frequency distance measurement technology to perform distance measurement. The principle of dual-frequency ranging technology is described in detail below.

The dual-frequency ranging in the embodiments of the present application refers to using a low-frequency modulation signal and a high-frequency modulation signal to respectively perform exposure to detect the distance. Among them, high frequency and low frequency are relative terms. For example, the two-frequency modulation signal used in dual-frequency ranging technology, of which the higher frequency is called high frequency, and the lower frequency is called For low frequency. In actual use, the frequency of the high frequency and the low frequency can be different by about 2 times, for example, the low frequency is 100 MHz, and the high frequency is 250 MHz, but it is not limited to this, and can be specifically set according to actual ranging requirements.

Since the ambiguity distance of the high-frequency signal during ranging is relatively small, for example, the ambiguity distance corresponding to 250MHz is 0.6m, so when the object exceeds 0.6m, when only the 250MHz waveform is used to detect it, the distance measurement is not accurate. The fuzzy distance corresponding to 100MHz is 1.5m, so when the object beyond 1.5m is detected using only 100MHz waveform, the distance cannot be measured accurately. But the minimum working distance when working with 100MHz+250MHz signals becomes 3m. Therefore, when measuring any pixel at a certain frequency within 3m, the tested distances d _L and d _H are determined by two variables, one is the unwrapping coefficient n _L , n _H , and the other is the phase delay Φ _H , Φ _L. The specific formula is as follows:

Among them, c is the speed of light (3*10 ⁸ m/s); two unwrapping coefficients are used to restore the true phase delay of each frequency, which can be calculated by the unwrapping algorithm; and the phase delay is the exposure of the receiver 20 The values (DCS0, DCS1, DCS2, DCS3) are calculated; D is the fuzzy distance.

The accuracy of the dual-frequency ranging method is analyzed below. Among them, the dual-frequency ranging error formula is as follows:

Among them, A _pix is the pixel area, too large pixels will reduce the resolution, large size and high cost; RE is quantum efficiency, also known as QE, which directly affects system performance; FF is the fill rate; φ _active is the light source received by the pixel Luminous power, an efficient light source will bring benefits to the system power consumption; _φambient is the ambient light power received by the pixel, which is determined by the user's environment, light source, and bandpass filter; t _int is the exposure time, and the time should not be too long ; N _system is the system noise, which is determined by the readout circuit; F _mod is the modulation frequency. Adjusting this parameter will improve the accuracy, but will reduce the measurable distance; C _mod is the modulation contrast, also known as MC, and is designed with the internal electric field of the pixel Related, q is a constant.

It can be known from the above formula that increasing the modulation frequency can effectively improve the test accuracy and reduce the test error, while the adjustment of other parameters has limited influence on the ranging error, or it is difficult to adjust.

For the distance measuring device 100 with dual-frequency ranging technology, if the two frequency values are similar (such as plus or minus 10%), and the exposure time of the two frequencies is equal (such as plus or minus 10%), the final output distance can be calculated twice The average of the measured distance is obtained. If the two frequencies are quite different (for example, the difference is about 50%), there are two ways to obtain the test distance, one way is through averaging, the other way is to use the high frequency range measurement result as the final output, low frequency Although it also participates in the exposure, it is mainly to solve the unwrapping coefficient of the high-frequency component and does not participate in other calculations. Therefore, the distance measuring device 100 can be used to increase the high-frequency exposure time and reduce the low-frequency exposure time as long as the unwrapping coefficient is calculated correctly. , Then the accuracy of ranging can be improved.

Based on the foregoing analysis of the dual-frequency ranging principle and error, the embodiments of the present application will focus on how to reduce the power consumption of the system while ensuring the accuracy of the ranging. Specifically, please refer to FIG. 4, which is a flowchart of a ranging method in an embodiment of this application. The distance measurement method is applied to the distance measurement device 100 in FIG. 1 or FIG. 2. The ranging method includes the following steps.

Step S11: Determine a high-frequency exposure time t _H and a low-frequency exposure time t _L , perform combination processing on low-frequency pixels when determining the low-frequency exposure time, and determine the low-frequency exposure time t _L according to the number of combinations.

In the embodiments of the present application, performing combination processing on low-frequency pixels refers to performing binning processing on low-frequency pixels. Among them, binning is an image readout mode in which the charges induced in adjacent pixels are added together and read out in a pixel mode. Binning is divided into horizontal direction binning and vertical direction binning. The horizontal direction binning is to add the charges of adjacent rows and read out, while the vertical direction binning is to add the charges of adjacent columns to read out. This technology is binning. The advantage is that several pixels can be combined as one pixel to increase sensitivity, output speed, and reduce resolution. When row and column binning is used at the same time, the aspect ratio of the image does not change, for example, when using 2*2 binning, The image resolution will be reduced by 75%. Specifically, a combination of 1*1, 1*2, 2*1, 1*3, 3*1, or 2*2 can be performed according to actual needs, which is not limited here.

In one embodiment, in order to quickly determine the high-frequency exposure time and the low-frequency exposure time, pre-exposure may be performed according to a preset time T1 to obtain a pre-exposed image, and according to each pixel of the pre-exposed image The strength of the reference signal received within the preset time T1 determines the high-frequency exposure time and the low-frequency exposure time respectively. Among them, the pre-exposure can be performed using a modulation signal with a higher frequency, or a modulation signal with a lower frequency, which is not limited here.

Step S12, performing high-frequency exposure according to the high-frequency exposure time to obtain a high-frequency exposure image, and performing low-frequency exposure according to the low-frequency exposure time to obtain a low-frequency exposure image.

Among them, the sequence of high-frequency exposure and low-frequency exposure is not limited. For example, high-frequency exposure may be performed first, or low-frequency exposure may be performed first.

Step S13: Calculate the distance between the distance measuring device and the target object according to the high-frequency exposure image and the low-frequency exposure image.

Referring to FIG. 5, in an embodiment _{, the high-frequency exposure time t H} and the low-frequency exposure time are respectively determined according to the signal strength of _{the pre-exposure image received within the preset time T 1} t _L specifically includes the following steps.

Step S111, the pre-exposure image acquired at the predetermined time T ₁ of the received reference signal strength A _1.

In one embodiment, the reference signal intensity A ₁ is the average signal intensity of all pixels of the pre-exposure image; or, the reference signal intensity is the average signal intensity of the characteristic pixels of the pre-exposure image; wherein, The characteristic pixels represent pixels corresponding to the characteristic regions of the pre-exposure image. For example, when the exposed subject is a human face, the characteristic area may be the area corresponding to the nose, eyes, and mouth, and the specific characteristic area may be determined according to the actual exposed subject.

Step S112: Determine the high-frequency target signal strength A _2H and the low-frequency target signal strength A _2L respectively according to the reference signal strength A ₁ .

Specifically, the relationship curve between the variance or standard deviation of the measured distance noise at different frequencies and the received signal strength can be combined to determine the high-frequency target signal strength A _2H and the low-frequency target signal strength A _2L . For example, when the distance noise variance corresponding to the reference signal strength is determined by the relationship curve of the distance noise variance or standard deviation and the received signal strength, the signal strength corresponding to the appropriate distance noise variance or standard deviation should be selected as the target signal strength. Wherein, the appropriate distance noise variance or standard deviation means that the target signal strength corresponding to the distance noise variance meets the requirements of ranging accuracy and the correct phase unwrapping coefficient can be obtained.

Step S113: Calculate the high-frequency exposure time t _H according to the reference signal strength A ₁ , the high-frequency target signal strength A _2H, and the preset time T ₁ ; and, according to the reference signal strength A ₁ , The low-frequency target signal intensity A _2L , the number of pixels b of each combination, and the preset time T _{1 are} used to calculate the low-frequency exposure time t _L ; wherein the low-frequency exposure time t _L and the number of pixels of each combination b It is inversely proportional.

Wherein, a formula for specifically calculating the high-frequency exposure time t _H and the low-frequency exposure time t _L is as follows:

Referring to FIG. 6, in an embodiment, step S13 specifically includes the following steps:

Step S131: Calculate the high-frequency phase delay information of each pixel in the high-frequency exposure image, and calculate the low-frequency phase delay information of each pixel in the low-frequency exposure image.

Step S132: Up-sampling the low-frequency phase delay information of each pixel combined in the low-frequency exposure image to obtain a low-frequency exposure image with the same resolution as the high-frequency exposure image.

For example, after performing 2*2 binning processing on low-frequency pixels, the phase delay information of each pixel of the low-frequency exposure image with a resolution of 160*120 is obtained after the combination of the low-frequency phase delay information of each pixel. After sampling, the phase delay information of each pixel of the low-frequency exposure image with a resolution of 320*240 is obtained.

In step S133, the high-frequency unwrapping coefficient of each pixel is calculated according to the high-frequency phase delay information of each pixel and the low-frequency phase delay information of each pixel.

Step S134: Calculate the distance between each pixel and the object photographed when the pixel is exposed according to the high-frequency unwrapping coefficient of each pixel and the high-frequency phase delay information of each pixel.

In one embodiment, when performing high-frequency exposure or low-frequency exposure, a continuous wave modulation mode or a pulse wave modulation mode is used. That is, high-frequency exposure can be switched between continuous wave modulation mode and pulse wave to mode; low-frequency exposure can also be switched between continuous wave modulation mode and pulse wave to mode. Among them, the continuous wave modulation mode can be used by default, or it can be switched according to the use environment of the distance measuring device 100. For example, the continuous wave modulation mode is used when the distance measuring device 100 is applied to an indoor environment, and the continuous wave modulation mode is used when the distance measuring device 100 is applied to an indoor environment. The pulse wave modulation mode is used in the outdoor environment, and different modulation modes can be adopted according to specific needs, which improves the applicability of the ranging method.

Specifically, in the exposure modulation process, according to actual pixel, system, and application requirements, in order to obtain depth information, dual-frequency mid-high/low-frequency exposure modulation can be divided into 1, 2, 3, 4 or more times. Among them, once in the embodiment of the present application refers to a group of continuous waveforms, rather than a periodic waveform. The number of high and low frequency exposures will be described in detail below with a specific embodiment.

Example 1: Continuous wave exposure modulation is used for high frequency exposure 4 times, and continuous wave exposure modulation is used for low frequency exposure 2 times. Refer to the table below for details.

In the embodiment of the present application, high-frequency exposure modulation is performed first, and then low-frequency exposure modulation is performed. In actual operation, the sequence of high-frequency exposure modulation and low-frequency exposure modulation can be exchanged. As shown in the above table, f _H represents high-frequency exposure modulation, and f _L represents low-frequency exposure modulation. A ₀ represents an exposure with a phase of 0°, A ₁₈₀ represents an exposure with a phase of 180°, similarly, A ₉₀ represents an exposure with a phase of 90°, and A ₂₇₀ represents an exposure with a phase of 270°. A ₀ A ₁₈₀ indicates that the phase window A and the phase window B perform phase 0° and 180° exposure respectively, and A ₁₈₀ A ₀ indicates that the phase window A and the phase window B perform phase 180° and 0° exposure respectively. In the above table, the high-frequency continuous wave A ₀ A ₁₈₀ , A ₉₀ A ₂₇₀ , A ₁₈₀ A ₀ , A ₂₇₀ A ₉₀ and the low-frequency continuous wave A ₀ A ₁₈₀ , A ₉₀ A ₂₇₀ are exposed in sequence. In actual operation, the order can be exchange. In the embodiments of this application, since high-frequency modulation determines the accuracy of the system, the use of chopping technology (that is _{, exposure of A 0} A ₁₈₀ and A ₁₈₀ A ₀ ) during high-frequency modulation can eliminate charge collection during high-frequency modulation. The mismatch caused by factors such as capacitance (gain error), set voltage, and background light can improve the accuracy of depth information. Among them, the chopping technology is also called the mismatch elimination technology of stored charge components.

Embodiment 2: High-frequency exposure uses continuous wave exposure modulation 4 times, and low-frequency exposure uses pulse wave exposure modulation once. See the table below for details.

The difference between Embodiment 2 and Embodiment 1 is that the low frequency adopts A ₀ A ₁₈₀ pulse wave exposure, and the exposure is performed once. Since the distance information obtained by low-frequency modulation is mainly phase unwrapping, pulse modulation is used, and 0° and 180° pulse modulation is used. The depth information for phase unwrapping can be obtained through only one exposure, which can further reduce the system Power consumption. It should be noted that in actual operation, the pulse modulation phases of the phase window A and the phase window B can be exchanged.

Embodiment 3: High-frequency exposure uses continuous wave exposure modulation twice, and low-frequency exposure uses continuous wave exposure modulation twice. See the table below for details.

In the embodiment of the present application, the high-frequency continuous wave A ₀ A ₁₈₀ , A ₉₀ A ₂₇₀ and the low-frequency continuous wave A ₀ A ₁₈₀ , A ₉₀ A ₂₇₀ are sequentially exposed. In actual operation, the sequence of high-frequency exposure and low-frequency exposure Can be exchanged. In this example, the high-frequency modulation does not use chopping technology to eliminate the offset caused by process, device and environmental factors. The accuracy of the depth information will be relatively reduced, but the power consumption will be reduced accordingly.

Embodiment 4: High-frequency exposure uses continuous wave exposure modulation twice, and low-frequency exposure uses pulse wave exposure modulation once. See the table below for details.

In the embodiment of the present application, the exposure of the _{high-frequency continuous wave A 0} A ₁₈₀ , A ₉₀ A ₂₇₀ and the low-frequency pulse wave A ₀ A _{180 are sequentially performed.} In actual operation, the sequence of high-frequency exposure and low-frequency exposure can be exchanged. In the embodiments of the present application, the high-frequency modulation does not use the chopping technology to eliminate the misalignment caused by the process, the device, and the environmental factors. The accuracy of the depth information will be relatively reduced, but the power consumption will be reduced accordingly. Low-frequency exposure modulation can obtain depth information for phase unwrapping with only one exposure, further reducing overall power consumption. It should be noted that in actual operation, the pulse modulation phases of the phase window A and the phase window B can be exchanged.

It should be noted that the above exposure combinations are only examples, and other exposure modulation times combinations with similar principles are also included in the protection scope of the present application. In addition, the pixels are spatially separated during exposure, that is, adjacent pixels are exposed to different phases, which can further reduce power consumption. As long as the principle is the same, it is also included in the scope of protection of the present application.

In the embodiment of the present application, the processor 30 is configured to execute the ranging method in any of the foregoing implementation manners.

Please refer to FIG. 7, which is a functional block diagram of the distance measuring device 100 in an embodiment of the application. In the embodiment of the present application, the distance measuring device 100 includes a determination module 110, an exposure module 120, and a calculation module 130. Wherein, the determination module 110 may be used to implement the method shown in step S11 in the foregoing method embodiment; the exposure module 120 may be used to implement the method shown in step S12 in the foregoing method embodiment; the calculation module 130 may It is used to implement the method shown in step S13 in the foregoing method embodiment.

Referring to FIG. 8, in an embodiment, the determining module 110 includes an acquiring unit 111 and a determining unit 112. The acquiring unit 111 may be used to implement the method shown in step S111 in the foregoing method embodiment; the determining unit may be respectively used to implement the method shown in step S112 and step S113 in the foregoing method embodiment.

Please refer to FIG. 9. In an embodiment, the calculation module 130 includes a calculation unit 131 and a sampling unit 132. The calculation unit 131 may be used to implement the method shown in step S131 in the foregoing method embodiment. The sampling unit 132 may be used to implement the method shown in step S132 in the foregoing method embodiment. The calculation unit 131 may also be used to implement the methods shown in step S133 and step S134 in the foregoing method embodiment.

The various embodiments of the present application can be combined arbitrarily to achieve different technical effects.

In the above-mentioned embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented by software, it can be implemented in the form of a computer program product in whole or in part. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on the computer, all or part of the processes or functions described in this application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center. Transmission to another website, computer, server or data center via wired (such as coaxial cable, optical fiber, digital subscriber line) or wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server or a data center integrated with one or more available media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, and a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium (for example, a solid state disk).

In short, the above descriptions are only examples of the technical solutions of the present invention, and are not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made according to the disclosure of the present invention shall be included in the protection scope of the present invention.

Claims

A ranging method, characterized in that it comprises:

Determine the high-frequency exposure time and the low-frequency exposure time; wherein, when determining the low-frequency exposure time, combine processing of low-frequency pixels, and determine the low-frequency exposure time according to the number of pixels in each combination;

Performing high-frequency exposure according to the high-frequency exposure time to obtain a high-frequency exposure image, and performing low-frequency exposure according to the low-frequency exposure time to obtain a low-frequency exposure image;

The distance between the distance measuring device and the target object is calculated according to the high-frequency exposure image and the low-frequency exposure image.
The distance measuring method according to claim 1, wherein the determining the high-frequency exposure time and the low-frequency exposure time comprises:

A pre-exposure for a preset time is performed to obtain a pre-exposed image, and the high-frequency exposure time and the low-frequency exposure time are respectively determined according to the strength of the reference signal received by the pre-exposure image within the preset time.
The distance measuring method according to claim 2, wherein the high-frequency exposure time and the low-frequency exposure time are respectively determined according to the signal intensity received by the pre-exposure image within the preset time ,include:

Acquiring the reference signal strength of the pre-exposure image received within the preset time;

Respectively determine the high-frequency target signal strength and the low-frequency target signal strength according to the reference signal strength;

Calculate the high-frequency exposure time according to the reference signal strength, the high-frequency target signal strength, and the preset time; and, according to the reference signal strength, the low-frequency target signal strength, and the number of pixels in each combination And the preset time is used to calculate the low-frequency exposure time; wherein the low-frequency exposure time is inversely proportional to the number of pixels in each combination.
The distance measurement method according to claim 3, wherein the reference signal intensity is the average signal intensity of all pixels of the pre-exposure image; or, the reference signal intensity is the characteristic pixel of the pre-exposure image The average signal intensity of the; wherein, the characteristic pixel characterizes the pixel corresponding to the characteristic area of the pre-exposure image.
The distance measuring method according to any one of claims 1 to 4, wherein the calculating the distance between the distance measuring device and the target object according to the high-frequency exposure image and the low-frequency exposure image comprises:

Calculating the high-frequency phase delay information of each pixel in the high-frequency exposure image, and calculating the low-frequency phase delay information of each pixel after the combination in the low-frequency exposure image;

Up-sampling the low-frequency phase delay information of each pixel combined in the low-frequency exposure image to obtain a low-frequency exposure image with the same resolution as the high-frequency exposure image;

Calculate the high-frequency unwrapping coefficient of each pixel according to the high-frequency phase delay information of each pixel and the low-frequency phase delay information of each pixel;

According to the high-frequency unwrapping coefficient of each pixel and the high-frequency phase delay information of each pixel, the distance between each pixel and the subject that the pixel is exposed to is calculated.
The distance measurement method according to claim 1, wherein the continuous wave modulation mode or the pulse wave modulation mode is used when performing low-frequency exposure.
The distance measuring method according to claim 1, wherein when performing high-frequency exposure or low-frequency exposure, adjacent pixels are exposed in different phases.
A distance measuring device, characterized in that it comprises:

A determining module, configured to determine high-frequency exposure time and low-frequency exposure time, perform combination processing on low-frequency pixels when determining the low-frequency exposure time, and determine the low-frequency exposure time according to the number of combinations;

An exposure module for performing high-frequency exposure according to the high-frequency exposure time to obtain a high-frequency exposure image, and performing low-frequency exposure according to the low-frequency exposure time to obtain a low-frequency exposure image; and

The calculation module is used to calculate the distance between the distance measuring device and the target object according to the high-frequency exposure image and the low-frequency exposure image.
The distance measuring device according to claim 8, wherein the determining module is specifically configured to perform pre-exposure according to a preset time to obtain a pre-exposure image, and according to each pixel of the pre-exposure image in the pre-exposure It is assumed that the intensity of the reference signal received within the time period respectively determines the high-frequency exposure time and the low-frequency exposure time.
The distance measuring device according to claim 9, wherein the determining module comprises:

An obtaining unit, configured to obtain the reference signal strength of the pre-exposure image received at the preset time; and

The determining unit is configured to determine the high-frequency target signal strength and the low-frequency target signal strength respectively according to the reference signal strength;

The determining unit is further configured to calculate the high-frequency exposure time according to the reference signal strength, the high-frequency target signal strength, and the preset time; and, according to the reference signal strength and the low-frequency target signal strength Calculating the low-frequency exposure time based on the determined number of combinations and the preset time; wherein the low-frequency exposure time is inversely proportional to the number of pixels in each combination.
The distance measuring device according to claim 10, wherein the reference signal intensity is an average signal intensity of all pixels of the pre-exposure image; or, the reference signal intensity is a characteristic pixel of the pre-exposure image The average signal intensity of the; wherein, the characteristic pixel characterizes the pixel corresponding to the characteristic area of the pre-exposure image.
The distance measuring device according to any one of claims 8-11, wherein the calculation module comprises:

A calculation unit for calculating the high-frequency phase delay information of each pixel in the high-frequency exposure image, and calculating the low-frequency phase delay information of each pixel combined in the low-frequency exposure image; and

A sampling unit, configured to up-sample the low-frequency phase delay information of each pixel combined in the low-frequency exposure image to obtain a low-frequency exposure image with the same resolution as the high-frequency exposure image;

The calculation unit is further configured to calculate the high-frequency unwrapping coefficient of each pixel according to the high-frequency phase delay information of each pixel and the low-frequency phase delay information of each pixel; and

According to the high-frequency unwrapping coefficient of each pixel and the high-frequency phase delay information of each pixel, the distance between each pixel and the subject that the pixel is exposed to is calculated.
8. The distance measuring device according to claim 8, wherein the continuous wave modulation mode or the pulse wave modulation mode is used when performing low-frequency exposure.
8. The distance measuring device according to claim 8, wherein when performing high-frequency exposure or low-frequency exposure, adjacent pixels are exposed to different phases.
A distance measuring device, characterized in that it comprises a transmitter, a receiving sensor and a processor; the processor is respectively coupled with the transmitter and the receiver; the processor is used to execute any of claims 1-7 The ranging method described in one item.
A computer-readable storage medium, the computer-readable storage medium stores a computer program, the computer program contains at least one piece of code, the at least one piece of code can be executed by a computer to control the computer to execute any one of claims 1-7 The described distance measurement method.