CN114829878A

CN114829878A - Ranging chip, device and method based on time of flight (ToF)

Info

Publication number: CN114829878A
Application number: CN202080087026.8A
Authority: CN
Inventors: 唐样洋; 罗鹏飞; 周鸿彬
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-02-28
Filing date: 2020-02-28
Publication date: 2022-07-29
Also published as: WO2021168847A1

Abstract

A distance measurement chip (201), a device and a method based on time-of-flight (ToF) relate to the technical field of chips, improve the accuracy of ToF distance measurement, and effectively improve the distance measurement distance of the ToF. The distance measurement chip (201) comprises: a first signal generator (301) for generating a first signal comprising a plurality of first pulses having a first width T for controlling the light emitting device to emit a light signal towards the target object; a second signal generator (302) for generating a second signal from the first signal, the second signal comprising a plurality of first pulses in the first signal and at least one second pulse delayed by a first width T from each of the plurality of first pulses; and the continuous wave processing circuit (303) is used for carrying out integration processing on the received optical signal reflected by the target object according to the second signal to obtain a plurality of exposure values, and the plurality of exposure values are used for calculating the phase delay corresponding to the flight time of the optical signal between the test chip (201) and the target object.

Description

Ranging chip, device and method based on time of flight (ToF)

Technical Field

The application relates to the technical field of chips, in particular to a distance measurement chip, a device and a method based on time of flight (ToF).

Background

At present, Time of Flight (ToF) ranging technology is widely applied to a plurality of fields, such as automatic driving, three-dimensional imaging, face recognition or intelligent robots. ToF ranging is the process of sending an optical signal through a transmitter to illuminate a target object, and receiving the signal reflected by the target object by a receiver. By measuring the round trip time (time of flight) between the target object and the receiver of the optical signal transmitted by the transmitter, distance information between the transmitter and the target object is calculated, and the distance information can be used for generating information such as a three-dimensional image of the target object.

The ToF ranging technique may employ a measurement method based on Continuous Wave (CW) ToF modulation, and a measurement method based on pulse wave (P) ToF modulation. The CW TOF measuring method calculates the distance of a target object from a phase difference by calculating the phase difference between a transmitted continuous optical signal and a received continuous optical signal. However, in the CW TOF measurement method, the exposure time is long, and a large amount of background light is easily received in the exposure process, so that the signal-to-noise ratio is low and the ranging error is large. In the TOF measurement method, the optical signal to be transmitted is a standard square wave signal, and the distance between the transmitter and the target object is calculated by measuring the phase delay of the received square wave signal. However, the P TOF measurement method has a high demand on the shape of the square waveform, and in practice, the waveform is largely imperfect, and distortion, burrs, and the like exist. The range error of the ptof measurement method is also large, and the effective test distance is shorter than that of the CW TOF.

Disclosure of Invention

The embodiment of the application provides a ranging chip, a ranging device and a ranging method based on time of flight (ToF), which are used for improving the accuracy of ToF ranging.

In a first aspect, a time-of-flight ToF based ranging chip is provided, which includes: a first signal generator for generating a first signal including a plurality of first pulses having a first width T, the first signal for controlling the light emitting device to emit a light signal to the target object; a second signal generator for generating a second signal from the first signal, the second signal comprising a plurality of first pulses in the first signal and at least one second pulse delayed by a first width T from each of the plurality of first pulses; and the continuous wave processing circuit is used for carrying out integration processing on the received optical signal reflected by the target object according to the second signal to obtain a plurality of exposure values, and the plurality of exposure values are used for calculating the phase delay corresponding to the flight time of the optical signal between the chip and the target object.

Among the above-mentioned technical scheme, through transmitting pulsed light signal for the received pulsed light signal can the short time exposure, has avoided in the CW ToF range finding because the noise signal that receives a large amount of background light and lead to, thereby can improve the SNR, improve the degree of accuracy of range finding. Meanwhile, the transmitted signal is not required to be a continuous wave, is not required to be a standard square wave, but is a discrete pulse wave, and the limitation of the P ToF ranging chip on the standard square wave waveform can be solved.

In one possible embodiment, each of the at least one second pulse has a width of the first width T. In the above possible implementation manner, the second pulse generated according to the first pulse is used to generate a demodulation signal for demodulating the received signal according to the second pulse, so that the received pulse signal can be demodulated according to a continuous wave ranging algorithm, the signal-to-noise ratio can be improved, and the ranging distance can be increased.

In one possible embodiment, the second pulse is a plurality of second pulses, and an interval between two adjacent second pulses in the plurality of second pulses is the first width T. In the above possible implementation manner, the plurality of second pulses generated according to the first pulse are used to generate the demodulation signal for demodulating the received signal according to the second pulse, so that the received pulse signal can be demodulated according to the continuous wave ranging algorithm, the signal-to-noise ratio can be improved, and the ranging distance can be increased.

In a possible implementation, the continuous wave processing circuit specifically includes: the first delayer is used for respectively carrying out delay operation on the second signals to obtain a plurality of third signals with different phases; the image sensor array is used for exposing the optical signal reflected by the target object received by the lens for multiple times according to a plurality of third signals with different phases to obtain a plurality of fourth signals; and the analog-to-digital converter is used for performing analog-to-digital conversion on the plurality of fourth signals to obtain a plurality of digital image arrays, and the plurality of digital image arrays comprise exposure values corresponding to the plurality of pixel points.

In one possible embodiment, two adjacent first pulses in the plurality of first pulses are spaced by (N +1) × T, where N is a preset positive integer or a random positive integer. In the possible implementation manner, when N is a random signal in the emitted laser signal, different pixel points of the image sensor array expose the reflected signal through different phase delays, so that modulation signals do not interfere with each other in the dimensions of code, time and frequency, and the anti-interference performance of the ranging result is improved.

In a possible implementation, the delay is specifically configured to: and performing m times of delay processing on the second signal to obtain m third signals, wherein the m times of delay processing comprise 0 phase delay processing, and the time difference of two adjacent delay processing in the m times of delay processing is 2T/m. In the above possible implementation manner, the second signal is subjected to the delay processing of different phases to generate different third signals, so that the received pulse signal can be demodulated by using the third signal according to the continuous wave ranging algorithm, and the ranging accuracy can be improved.

In one possible embodiment, the ranging chip further includes: a second delayer for generating a delayed signal of the first signal; and a light emitting device for emitting a light signal to the target object according to the delayed signal of the first signal. In the above possible implementation manner, the second delayer may enable the ToF ranging apparatus to obtain a plurality of accurate exposure values within a range from 0 meter of the target object from the ToF ranging apparatus to the fuzzy distance.

In a second aspect, there is provided a ranging apparatus comprising: the distance measuring chip, the light source driver, the light emitting device and the lens according to any one of the first aspect; the light source drive is used for driving the light-emitting device to emit a light signal according to the first signal generated by the distance measuring chip; a light emitting device for emitting a light signal to the target object based on the driving of the first signal; and the lens is used for receiving the optical signal reflected by the target object and transmitting the optical signal to the ranging chip. In one possible embodiment, the light emitting device is a straight cavity surface emitting laser VCSEL.

In a third aspect, an electronic device is provided, where the electronic device includes the ranging apparatus as defined in any one of the first aspect, and the electronic device further includes: and the calculating module is used for calculating the phase delay corresponding to the flight time of the optical signal between the distance measuring device and the target object according to the plurality of exposure values obtained by the distance measuring device.

In a fourth aspect, a time-of-flight ToF based ranging method is provided, the method comprising: generating a first signal, the first signal comprising a plurality of first pulses, the first pulses having a first width T, the first signal being for emitting an optical signal toward a target object; generating a second signal from the first signal, the second signal comprising a plurality of first pulses in the first signal and at least one second pulse delayed by a first width T from each of the plurality of first pulses; and carrying out integration processing on the received optical signal reflected by the target object according to the second signal to obtain a plurality of exposure values, wherein the exposure values are used for calculating the phase delay corresponding to the flight time of the optical signal between the ranging chip and the target object.

In one possible embodiment, each of the at least one second pulse has a width of the first width T.

In one possible embodiment, the second pulse is a plurality of second pulses, and an interval between two adjacent second pulses in the plurality of second pulses is the first width T.

In one possible embodiment, the integrating the received light signal reflected by the target object according to the second signal to obtain a plurality of exposure values comprises: respectively carrying out delay operation on the second signals to obtain a plurality of third signals with different phases; exposing the received optical signal reflected by the target object for multiple times according to a plurality of third signals with different phases to obtain a plurality of fourth signals; and performing analog-to-digital conversion on the plurality of fourth signals to obtain a plurality of digital image arrays, wherein the plurality of digital image arrays comprise exposure values corresponding to a plurality of pixel points.

In one possible embodiment, two adjacent first pulses in the plurality of first pulses are spaced by (N +1) × T, where N is a preset positive integer or a random positive integer.

In one possible implementation, the delaying the second signal to obtain a plurality of third signals with different phases specifically includes: and performing m times of delay processing on the second signal to obtain m third signals, wherein the m times of delay processing comprise 0 phase delay processing, and the time difference of two adjacent delay processing in the m times of delay processing is 2T/m.

In one possible implementation, after generating the first signal, the ranging method further includes: an optical signal is emitted to the target object in accordance with the first signal.

In one possible implementation, after generating the first signal, the ranging method further includes: generating a delayed signal of the first signal; emitting the optical signal to the target object according to the first signal specifically includes: and emitting the optical signal to the target object according to the delay signal of the first signal.

In a possible implementation manner, after the received light signal reflected by the target object is integrated according to the second signal to obtain a plurality of exposure values, the ranging method further includes: and calculating the phase delay corresponding to the flight time of the optical signal between the distance measuring device and the target object according to the exposure values.

In a fifth aspect, an electronic device is provided that includes a processor coupled with a memory; the memory is used for storing computer programs or instructions; the processor is adapted to execute the computer program or instructions stored in the memory to enable the electronic device to perform the method according to any of the fourth aspects above.

A sixth aspect provides a computer readable storage medium storing a program or instructions, which when executed by a processor of an electronic device, enables the electronic device to perform the method of any of the above fourth aspects.

In a seventh aspect, there is provided a computer program product comprising a program or instructions which, when run on a computer, causes the computer to perform the method according to any of the fourth aspects above.

The technical problems and technical effects that are solved by the ranging chip, the ranging device, the electronic device, the computer-readable storage medium, and the computer program product based on the time-of-flight ToF according to the present application may refer to any of the contents described in the first aspect, and are not described herein any more.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

FIG. 1 is a schematic diagram of a transmitted signal and a reflected signal for ToF ranging;

fig. 2 is a first schematic structural diagram of a ToF ranging apparatus according to an embodiment of the present disclosure;

fig. 3 is a schematic structural diagram of a ToF ranging chip provided in an embodiment of the present application;

fig. 4(a) is a first schematic waveform diagram of a first signal provided in an embodiment of the present application;

fig. 4(b) is a waveform diagram of a first signal provided in the present embodiment;

fig. 5(a) is a first schematic waveform diagram of a second signal provided in the present embodiment;

fig. 5(b) is a waveform diagram of a second signal provided in the embodiment of the present application;

fig. 6 is a schematic structural diagram of a ToF ranging apparatus according to an embodiment of the present application;

fig. 7 is a schematic diagram of a modulation waveform of a ToF ranging apparatus according to an embodiment of the present disclosure;

fig. 8 is a schematic diagram illustrating a modulation method of a ToF ranging apparatus according to an embodiment of the present disclosure;

fig. 9 is a schematic structural diagram of a ToF ranging apparatus according to an embodiment of the present invention;

fig. 10 is a schematic diagram of a modulation waveform of another ToF ranging apparatus according to an embodiment of the present application;

fig. 11 is a schematic flowchart of a ToF ranging method according to an embodiment of the present disclosure;

fig. 12 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

Detailed Description

In the present application, the terms "first", "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present embodiment, "a plurality" means two or more, and "at least one" means one or more, unless otherwise specified.

It is noted that the words "exemplary" or "such as" are used herein to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "e.g.," is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.

The embodiment of the application provides a ranging method and a ranging device based on time-of-flight (ToF), and related technical terms and principles thereof are briefly described below.

A LiDAR (Light Detection and Ranging) is a radar system that detects characteristic quantities such as a position, a velocity, and the like of a target object by emitting a laser beam. The working principle of the method is that a laser detection signal is emitted to a target object, then the received signal reflected from the target object is compared with the emitted detection signal, and after signal processing is carried out according to the comparison result, relevant information of the target object is obtained, such as parameters of distance, direction, height, speed, attitude, even shape and the like between a laser radar and the target object. In addition, the laser radar has high measurement precision and fine time and space resolution, and can complete the functions of distance measurement (ranging), target detection, imaging, tracking, image identification and the like, wherein the ranging is the basic function of the laser radar.

Currently, lidar may use the principle of time-of-flight of light to measure the distance between the lidar and a target object, for example, by the formula: and calculating the distance between the laser radar and the target object by the aid of the R-c multiplied by t/(2 multiplied by n). Where n is the refractive index in the medium through which the light propagates and c is the speed of light, about 299792.458 km/s. The principle can realize the detection of several meters to several kilometers.

The basic principle of the CW ToF measuring method is shown in fig. 1, where a ToF ranging device irradiates a target object with a transmitting signal, and a phase difference related to a distance is generated when a modulating signal is reflected back to the surface of the ToF ranging device. The ToF ranging device receives the reflected signal of the modulation signal, demodulates the reflected signal to obtain the phase difference caused in the flying process, and then calculates the distance between the ToF ranging device and the target object according to the known quantity such as the optical flying speed, the frequency of the modulation signal and the like.

Further, in order to obtain three-dimensional coordinate information of the target object from the laser radar and reconstruct the shape of the surface of the target object in the scene where the target object is located through the two-dimensional ToF image sensor array, each pixel point in the ToF image sensor array is required to independently receive and demodulate the phase difference between the laser radar and each corresponding point on the surface of the target object, so that the distance information of each corresponding point on the surface of the target object is obtained. Finally, when each exposure is performed on the ToF imaging system, distance information with the same number as that of pixel points of the sensor image can be obtained, that is, a depth distance image of the target object can be obtained.

The ranging principle of CW ToF will be briefly described next. As shown in fig. 1, the transmission signal may be a cosine signal or a square wave signal, and the transmission signal s (t) may be represented as: s (t) cos (ω · t), where t denotes time and ω denotes the frequency of the transmission signal.

Transmitting signalA certain offset is generated in a reflected signal reflected from a target object after reaching the target object, and the reflected signal g (t) can be represented as:

wherein, a represents an amplitude value,

representing the phase difference of the reflected signal relative to the transmitted signal.

By modulating the transmitting signal, the ToF ranging device receives and demodulates a reflected signal with a phase difference reflected by the target object, and indirectly calculates the distance information between the ToF ranging device and the target object, wherein the calculation formula of the distance information D can be as follows:

where c denotes the speed of light and f denotes the frequency of the modulation signal.

The ToF ranging demodulation process can be implemented by using a correlation function method. The correlation function is a function describing the degree of correlation between the values of the reference signal at any two different times. By taking the transmitting signal as a reference signal, the correlation degree between the transmitting signal after frequency modulation and a reflected signal which generates a phase difference after irradiating the target object can be obtained through a correlation function. The correlation function is calculated as follows:

illustratively, 4 different values of delay τ may be chosen: tau is ₀ ＝0°、τ ₁ ＝90°、τ ₂ 180 ° and τ ₃ Substitution c (τ) was calculated for 270 °. Since the reflected signal may include a reflected signal generated by background light, the reflected signal may be generated by a backlightAn offset K is added to its correlation function. After the superposition treatment, the following value C (. tau.) was obtained ₀ )、C(τ ₁ )、C(τ ₂ ) And C (τ) ₃ )。

The phases can be respectively obtained by conversion of the above formulas

Offset K and amplitude value a. Phase delay

Representing the propagation delay of the light during flight, which is proportional to the distance to the target when the modulation frequency is set to a fixed value. The offset K may be used to provide a conventional 2D intensity image and to indicate the amount of charge in the image sensor pixel. Amplitude value a represents the depth resolution of a directly measurable pixel. Wherein:

by phase delay

Substituting into the above formula

The distance D between the ToF ranging device and the target object can be calculated.

Further, since each pixel of the two-dimensional array image sensor can measure the distance information corresponding to the ToF ranging device and the surface of the target object, the CW ToF ranging device actually obtains a depth distance image of the surface of the target object relative to the ToF ranging device. The three-dimensional coordinate information of the surface of the target object can be obtained by further performing data processing on the depth distance image data. The specific algorithm is not described in detail in the present application.

According to the method, in the CW ToF measuring method, because the emission signal and the reflection signal are both continuous wave signals, the exposure time is long, a large amount of background light is easily received in the exposure process, the signal-to-noise ratio is low, and the ranging error is large. In the P ToF measurement method using a pulse wave, the transmitted signal is not a continuous wave but a pulse wave, and the optical signal to be transmitted is a standard square wave signal, and the distance between the transmitter and the target object is calculated by measuring the phase delay of the received square wave signal. However, the P ToF measurement method has a high requirement for the waveform shape of the square wave, and in practice, the waveform is largely imperfect, and distortion or burr occurs. Therefore, the range error of the P ToF measurement method is larger, and the effective test distance is shorter than that of the CW ToF.

The application provides a novel ToF distance measuring device and a distance measuring method by combining the distance measuring technologies of CW ToF and P ToF. When the transmitting end of the ToF distance measuring device transmits a transmitting signal, the transmitting end transmits pulse optical signals in a pulse mode, and during receiving, the transmitting end receives reflected pulse optical signals at intervals in a mode similar to a continuous wave CW ToF mode. The ranging algorithm also uses the ranging algorithm of CW ToF. By combining two ranging technologies, the problem of low signal-to-noise ratio caused by continuous reception of reflected light signals in CW ToF ranging is avoided, and the problem of high requirement of P ToF on standard square waves is avoided, and pulse wave signals are adopted. Therefore, the defects of the CW ToF ranging technology can be reduced, the ranging signal-to-noise ratio can be effectively improved, and the ToF ranging can be carried out under the condition that the waveform is not a standard square wave.

The embodiment of the application provides a range finding chip based on time of flight (ToF), and the range finding chip can be applied to three-dimensional (3D) cameras, intelligent vehicles or computers and other equipment. For example, as shown in fig. 2, the embodiment of the present application takes a distance measuring device of a 3D ToF camera as an example for description. The ToF ranging apparatus may include: the distance measuring device comprises a distance measuring chip 201, a lens 202, a light source driver 203 and a light emitting device 204.

The ranging chip 201 may be configured to generate a first signal, which may be used to control the light source driver 203 to enable the light emitting device 204 to emit a specified light signal, e.g., a pulsed light signal, to the target object. Where the optical signal is one of the above-mentioned emitted signals, the target object is an object that the emitted optical signal can reach and form a reflected optical signal. In addition, the distance measuring chip 201 may be further configured to receive an optical signal reflected by the target object transmitted by the lens 202, and perform signal processing according to the first signal and the optical signal reflected by the target object transmitted by the lens 202 to obtain a phase delay corresponding to a flight time of the optical signal between the ToF distance measuring device and the target object, so as to obtain a distance between the ToF distance measuring device and the target object through calculation.

The lens 202, which is an optical device composed of one or more optical lenses, may be configured to receive the optical signal reflected by the target object and transmit the optical signal reflected by the target object to the ranging chip 201.

And a light source driver 203 for driving the light emitting device 204 to emit a light signal according to the first signal generated by the ranging chip 201. For example, the light source drive 203 may be a laser drive.

And a light emitting device 204 for emitting a light signal to the target object according to the instruction signal of the light source drive 203. Such as a diode or a laser, is a device capable of emitting a visible light signal or emitting a laser signal. Specifically, the Light Emitting device may be a Vertical-Cavity Surface-Emitting Laser (VCSEL), a Light Emitting Diode (LED), or the like. The VCSEL is a special laser, the laser light of which is emitted perpendicularly to the top surface, the light emitting power of which is strongly related to the operating mode, and the VCSEL can stably emit high-power pulses under certain conditions.

With reference to fig. 2, as shown in fig. 3, the ranging chip 201 provided in the embodiment of the present application may specifically include: a first signal generator 301, a second signal generator 302 and a continuous wave processing circuit 303.

A signal generator is a device that can provide electrical signals of various frequencies, various waveforms, and output levels, and is also referred to as a signal source or an oscillator. The various wave curves are expressed by trigonometric functions. The signal generator can generate various waveforms such as triangular, saw tooth, rectangular, or sinusoidal, etc., including a sinusoidal signal generator, a low frequency signal generator, a high frequency signal generator, a pulse signal generator, or a pseudo-random signal generator, etc. The signal generator in the embodiment of the present application is used for generating a pulse signal, and thus may be a pulse signal generator or a pseudo-random signal generator that may generate a pulse signal.

The first signal generator 301 may be configured to generate a first signal, the first signal including a plurality of first pulses, and a pulse width of the first pulses may be a first width. The first signal may be used for the light source driver 203 to drive the light emitting device 204 to emit a light signal to the target object according to the first signal. Additionally, the first signal may also be used for the second signal generator 302 to generate a second signal from the first signal.

In one embodiment, the pulse width of the first pulse is the first width Tp, and the pulse interval may be N +1 times the first width. The pulse intervals of adjacent first pulses may be the same or different. That is, the interval between two adjacent first pulses in the first signal may be (N +1) × Tp, where N may be a preset positive integer or a random positive integer.

In the above embodiments, the signal generator may operate in a random state or a non-random state. If N is a random positive integer, pulse signals with different pulse intervals can be generated through different random positive integers, so that interference generated among various pulse signals at the same moment can be avoided, and the anti-interference performance of the ranging result is improved.

For example, the waveform diagram of the first signal may be as shown in fig. 4(a) or fig. 4 (b). As shown in fig. 4(b), N may be a random positive integer. When the ToF ranging device operates in a random state, the pseudo-random positive integer range may be set to (N1-N2), and the first signal generator generates the first pulse signal according to the received Tp and the random positive integer range. The pulse width of the first pulse signal is Tp, and the interval between pulses is (N +1) × Tp, where N is a random positive integer generated by a pseudo-random number generator inside the first signal generator, and N may be randomly 1, 2, or 3, for example.

For example, the waveform of the first signal may also be as shown in fig. 4(a), and N may be a preset positive integer. When the ToF ranging device works in a non-random state, the first signal generator generates a first pulse signal, the pulse width of the first pulse signal is Tp, the interval between adjacent first pulses is (n +1) × Tp, wherein n is a preset positive integer, and the pulse intervals of the adjacent pulses are the same.

A second signal generator 302 for generating a second signal from the first signal, the second signal comprising a first pulse in the first signal; the second signal further comprises at least one second pulse spaced from each first pulse by a first width Tp.

In one possible embodiment, the pulse width of the second pulse may be a first width Tp; if there are at least two second pulses, the pulse interval of the at least two adjacent second pulses may be the same as the first width Tp. The number of the second pulses may be multiple, for example, 2 or 3, and the second pulses do not overlap with any of the first pulses.

Illustratively, when the waveform of the first signal is as shown in fig. 4(a), the waveform of the second signal may be as shown in fig. 5(a), and the second signal includes first pulses with a pulse width Tp and a plurality of second pulses with a pulse width Tp separated from each of the first pulses, wherein the pulse width of the second pulses is also Tp.

When the waveform of the first signal is as shown in fig. 4(b) and the pulse intervals are random, the waveform of the second signal may be as shown in fig. 5(b) and the pulse intervals of the second signal may also be random.

The continuous wave processing circuit 303 may be configured to perform integration processing on the received optical signal reflected by the target object according to the input second signal to obtain a plurality of exposure values, where the plurality of exposure values are used to calculate a phase delay corresponding to the flight time of the optical signal between the ranging chip 201 and the target object according to a ToF ranging algorithm of the continuous wave CW.

In the embodiments of the present application, the first signal generator generates a first signal, the second signal is generated according to the first signal, the second signal includes at least two pulse signals, and the second signal and a reflected signal of the first signal are subjected to a cross-correlation operation. Therefore, the received reflection signal of the target object is demodulated through the second signal, and the farthest testable distance of the ToF ranging chip is positively correlated with the period of the modulation signal, so that the period of the modulation signal is increased, and the farthest testable distance is increased. In addition, compared with the existing CW ToF ranging technology, the pulse light signal is transmitted, so that the received pulse light signal can be exposed in a short time, noise signals caused by receiving a large amount of background light are avoided, the signal-to-noise ratio is improved, and the limitation of a P ToF ranging chip on standard square wave waveforms is solved.

In one embodiment, as shown in fig. 6, the continuous wave processing circuit 303 may specifically include a delayer 601, an image sensor array 602, and an analog-to-digital converter 603.

The delayer 601 is configured to perform a time delay operation on the input second signal to obtain a plurality of third signals with different phases, and the plurality of third signals with different phases are input to the image sensor array 602, and are configured to perform multiple exposures on an optical signal reflected by the target object received by the lens. The DLL delay values may be different for different ToF ranging devices.

In one embodiment, the Delay 601 may be a Delay-locked Loop (DLL), also called a Delay line, which is a component or device that precisely delays a signal for a certain period of time. For example, the DLL delay device may include N delay modules, and output signals of 0 to N delay modules are controlled by a command, so that there is an accurate time delay between an output signal and an input signal. The delay value may be preset by the delay device, or may be input externally through the delay device.

For example, as shown in fig. 7, the second signal may be delayed by 0 phase to obtain signal 1; 1/2 phase delay is carried out on the second signal to obtain a signal 2; 1/4 phase delay is carried out on the second signal to obtain a signal 3; the second signal is delayed 3/4 in phase to obtain signal 4.

The image sensor array 602 is configured to perform multiple exposures on signals reflected by the target object received by the lens according to the input multiple third signals with different phases, that is, the reflected signals are superimposed with the multiple third signals with different phases, that is, an integration operation is performed to obtain multiple fourth signals. And each pixel point of the image sensor array corresponds to a plurality of fourth signals obtained by carrying out multiple exposures. The image sensor array 602 inputs the plurality of fourth signals to an analog-to-digital converter for generating a digital image array.

It should be noted that, in practical applications, the exposure modulation process may set the exposure modulation to 1 time, 2 times, 3 times, 4 times or more (here, 1 time refers to a set of continuous waveforms, not to a periodic waveform) according to the actual pixels, the accuracy of the ToF ranging chip and the requirements of the application.

Illustratively, in the embodiments of the present application described above, the continuous wave exposure is modulated 4 times; alternatively, continuous wave exposure modulation may be set to 2 times. Other exposure modulation times of similar principles are also included in the scope of the present application. Meanwhile, the pixels may be spatially separated, that is, adjacent pixels may be exposed to different delay values, and the principle of exposure modulation is the same as that of the present application and is also included in the protection scope of the present application.

For example, adjacent pixels A and B are exposed to different delay values, and pixel A is exposed to 0 phase, denoted as A ₀ (ii) a Pixel B is exposed to 1/2 phases, denoted as B ₁₈₀ . The image sensor array of the ToF ranging device may sequentially perform continuous wave a as shown in fig. 8 ₀ B ₁₈₀ ，A ₉₀ B ₂₇₀ ，A ₁₈₀ B ₀ ，A ₂₇₀ B ₉₀ Four exposures. Or low-frequency continuous wave A ₀ B ₁₈₀ ，A ₉₀ B ₂₇₀ In practical operation, the above exposure sequence may be exchanged.

The analog-to-digital converter 603 is configured to perform digital processing on the input multiple fourth signals according to an algorithm for converting an analog signal into a digital signal, so as to obtain multiple digital image arrays.

In one embodiment, as shown in fig. 9, the ToF ranging apparatus may further include: the distance measurement module 901 is configured to calculate a distance between the ToF ranging apparatus and the target object according to the plurality of digital image arrays obtained by the ToF ranging chip. The distance measuring module 901 may be implemented in a hardware manner, or may be implemented in a software manner, which is not specifically limited in this application.

In the embodiment of the present application, by combining two ranging technologies, namely CW ToF and P ToF, the transmit signal adopts a P ToF ranging technology to intermittently transmit a pulse signal (first signal); when the image sensor array performs exposure reception, the received reflected light is exposed in accordance with the second signal, and exposure is performed in a four-phase delay manner (two or four exposures) of the CW ToF ranging algorithm. Compared with the prior art, can effectual promotion range finding SNR to can carry out the TOF range finding under the wave form is not the condition of standard square wave, in addition, effectively increase furthest measurable distance in addition, promote holistic range finding performance. Meanwhile, when the emitted laser signals are random signals, different pixel points of the image sensor array expose the reflected signals through different phase delays, so that modulation signals are not interfered with each other in the dimensionality of code words, the dimensionality of time and the dimensionality of frequency, and the accuracy of distance measurement is improved.

In another possible embodiment, a delay device, for example, a second delay device, may be added between the first signal generator 301 and the light source driver 203 for performing a delay process on the first signal, so that the light source driver 203 may drive the light emitting device to emit the pulse light signal according to the signal generated after performing the delay process on the first signal.

For example, the waveform diagram of the first signal may be as shown in fig. 10, and the emission signal may be emitted pulsed light after being subjected to 1/2-phase delay processing according to the first signal. And the plurality of third signals are generated by different time delay processing according to the first signals and are used for respectively carrying out exposure modulation on the pulse signals reflected by the target object for four times, and the distance information between the ToF ranging device and the target object is obtained by calculating the phase difference between the transmitting signals and the receiving signals. This embodiment enables the ToF ranging device to obtain a plurality of accurate exposure values within a range of 0 meters from the target object to the ToF ranging device to the ambiguity distance.

Next, a description is given of a workflow of the ToF ranging apparatus according to an embodiment of the present application. As can be seen from fig. 6 or fig. 7, the specific process of transmitting signals by the ToF ranging apparatus according to the embodiment of the present application may be S01-S03 as shown in fig. 11.

S01: the pulse duration is set to Tp and input to the first signal generator.

In one possible embodiment, when the distance measuring device is operated in the random mode, it is also necessary to set a random number range and generate a random positive integer, which is input to the first signal generator.

S02: the first signal generator generates a first signal.

Wherein the first signal generator may generate the first signal from the received pulse width Tp, or the pulse width Tp and the random positive integer N. The first signal may include a plurality of first pulse signals, the first pulse signals may have a pulse width Tp, and a pulse interval between the plurality of first pulses may be (N +1) × Tp.

S03: and sending out a pulse signal according to the first signal.

The laser drive drives the light emitting device according to the first signal or the delay signal of the first signal, so that the light emitting device emits pulse light signals corresponding to brightness information.

As can be seen from the foregoing, a specific flow of the ToF ranging apparatus receiving the reflected signal and performing the modulation process may be S04-S08 as shown in fig. 11.

S04: the second signal generator generates a second signal according to the first signal.

The second signal includes all the first pulse signals in the first signal, and one or more second pulse signals are further transmitted after the first pulse of the first signal and after an interval of Tp, wherein the pulse width of the second pulse signals may be Tp.

S05: and performing time delay operation according to the second signal, and outputting a delayed third signal.

The delay outputs a plurality of third signals P1 by performing a time delay operation on the input second signals, for example, the first exposure is not delayed, the second exposure is delayed by 1/4 cycles, the third exposure is delayed by 1/2 cycles, and the fourth exposure is delayed by 3/4 cycles.

S06: and exposing the reflected signals collected by the lens according to the third signals to obtain a plurality of fourth signals.

The image sensor array exposes the reflected signal P collected by the lens according to the third signals P1, and a fourth signal P2 array is obtained. Wherein each pixel of the image sensor array outputs a different exposure value.

S07: and performing analog-to-digital conversion according to the plurality of fourth signals to obtain a plurality of digital image arrays.

The analog-to-digital converter performs analog-to-digital conversion on the P2 array signal to obtain a P3 array, and transmits the P3 array to the ranging module.

S08: and obtaining the phase delay of the digital image array according to a ranging algorithm, and calculating the distance of the target object according to the frequency of the modulation signal.

After the ranging module respectively receives the P3 arrays obtained by exposing different delay signals, phase delay is obtained through calculation according to the formula of the CW ToF ranging algorithm, and then distance information or image information of corresponding pixel points of the target object is obtained through calculation.

According to the embodiment of the application, by combining two ranging technologies of CW ToF and P ToF, the ranging signal-to-noise ratio can be effectively improved, and the ToF ranging can be carried out under the condition that the waveform is not a perfect square wave.

An electronic device 1200 may include at least one processor 1201, a communication line 1202, and a memory 1203, as shown in fig. 12.

The processor 1201 may be a general-purpose Central Processing Unit (CPU), microprocessor, application-specific integrated circuit (ASIC), or one or more ics for controlling the execution of programs in accordance with the present disclosure.

The communication link 1202 may include a path for communicating information between the aforementioned components, such as a bus.

The memory 1203 may be a read-only memory (ROM) or other type of static storage device that may store static information and instructions, a Random Access Memory (RAM) or other type of dynamic storage device that may store information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disk storage, optical disk storage (including compact disc, laser disc, optical disc, digital versatile disc, blu-ray disc, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to these. The memory may be separate and coupled to the processor 1201 via the communication link 1202. The memory 1203 may also be integrated with the processor 1201. The memory provided by the disclosed embodiments may generally be non-volatile. The memory 1203 is used for storing computer-executable instructions for executing the present disclosure, and is controlled by the processor 1201 to execute the instructions. The processor 1201 is configured to execute computer-executable instructions stored in the memory 1203 to implement the methods provided by the embodiments of the present disclosure.

Optionally, the computer executed instructions in the embodiments of the present disclosure may also be referred to as application program codes, which are not specifically limited in the embodiments of the present disclosure.

In particular implementations, processor 1201 may include one or more CPUs such as CPU0 and CPU1 in fig. 12 as one embodiment.

In particular implementations, electronic device 1200 may include multiple processors, such as processor 1201 and processor 1207 in fig. 12, for example, as an example. Each processor may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. A processor herein may refer to one or more devices, circuits, and/or processing cores for processing data (e.g., computer program instructions).

In particular implementations, electronic device 1200 may also include a communication interface 1204, as one embodiment. The communication interface 1204, which may be any transceiver or other communication network, may be used for communicating with other devices or communication networks, such as an ethernet interface, a Radio Access Network (RAN), a Wireless Local Area Network (WLAN), etc.

In particular implementations, electronic device 1200 may also include an output device 1205 and an input device 1206, as one embodiment. An output device 1205, in communication with the processor 1201, may display information in a variety of ways. For example, the output device 1205 may be a Liquid Crystal Display (LCD), a Light Emitting Diode (LED) display device, a Cathode Ray Tube (CRT) display device, a projector (projector), or the like. The input device 1206 is in communication with the processor 1201 and may receive user input in a variety of ways. For example, the input device 1206 may be a mouse, keyboard, touch screen device, or sensing device, among others.

In a specific implementation, the electronic device 1200 may be a desktop, a laptop, a web server, a Personal Digital Assistant (PDA), a mobile phone, a tablet, a wireless terminal device, an embedded device, or a device with a similar structure as in fig. 12. The disclosed embodiments do not limit the type of the electronic device 1200.

In some embodiments, processor 1201 in fig. 12 may execute the instructions by calling a computer stored in memory 1203 to cause apparatus 1200 to perform the ToF ranging method in the above-described method embodiments.

In an exemplary embodiment, there is also provided a storage medium comprising instructions, for example, the memory 1203 comprising instructions, which are executable by the processor 1201 of the electronic device 1200 to perform the ToF ranging method described above.

Through the description of the above embodiments, it is clear to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional modules is merely used as an example, and in practical applications, the above function distribution may be completed by different functional modules according to needs, that is, the internal structure of the device may be divided into different functional modules to complete all or part of the above described functions.

In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described embodiments of the apparatus are merely illustrative, and for example, the division of the circuit or the unit is only one type of division of logic functions, and there may be other divisions when actually implementing, for example, a plurality of units or components may be combined or integrated into another apparatus, or some features may be omitted or not implemented. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may be one physical unit or a plurality of physical units, that is, may be located in one place, or may be distributed in a plurality of different places. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a readable storage medium. Based on such understanding, the technical solutions of the embodiments of the present application may be essentially or partially contributed to by the prior art, or all or part of the technical solutions may be embodied in the form of a software product, where the software product is stored in a storage medium and includes several instructions to enable a device (which may be a single chip, a chip, or the like) or a processor (processor) to execute all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

Finally, it should be noted that: the above description is only an embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions within the technical scope of the present disclosure should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

A time-of-flight (ToF) -based ranging chip, comprising:

a first signal generator for generating a first signal, the first signal comprising a plurality of first pulses, the first pulses having a first width T, the first signal for controlling the light emitting device to emit a light signal to the target object;

a second signal generator for generating a second signal from the first signal, the second signal comprising the plurality of first pulses in the first signal and at least one second pulse delayed by the first width T from each of the plurality of first pulses;

and the continuous wave processing circuit is used for carrying out integration processing on the received optical signal reflected by the target object according to the second signal to obtain a plurality of exposure values, and the plurality of exposure values are used for calculating the phase delay corresponding to the flight time of the optical signal between the chip and the target object.
The ranging chip of claim 1, wherein a width of each of the at least one second pulse is the first width T.
The ranging chip as claimed in claim 2, wherein the second pulse is a plurality of second pulses, and an interval between two adjacent second pulses of the plurality of second pulses is the first width T.
The ranging chip according to any of claims 1 to 3, wherein the continuous wave processing circuit comprises:

the first delayer is used for respectively carrying out delay operation on the second signals to obtain a plurality of third signals with different phases;

the image sensor array is used for exposing the optical signal received by the lens and reflected by the target object for multiple times according to the plurality of third signals with different phases to obtain a plurality of fourth signals;

and the analog-to-digital converter is used for performing analog-to-digital conversion on the plurality of fourth signals to obtain a plurality of digital image arrays, and the plurality of digital image arrays comprise exposure values corresponding to a plurality of pixel points.
The ranging chip according to any one of claims 1 to 4, wherein two adjacent first pulses of the plurality of first pulses are spaced apart by (N +1) × T, wherein N is a preset positive integer or a random positive integer.
The ranging chip according to claim 4 or 5, wherein the first delay is specifically configured to:

and performing m times of delay processing on the second signal to obtain m third signals, wherein the m times of delay processing comprise 0 phase delay processing, and the time difference of two adjacent delay processing in the m times of delay processing is 2T/m.
The ranging chip according to any one of claims 1 to 6, wherein the ranging chip further comprises:

a second delay for generating a delayed signal of the first signal;

the light emitting device is used for emitting a light signal to the target object according to the time delay signal of the first signal.
A time-of-flight (ToF) -based ranging device, comprising: the ranging chip, the light source driver, the light emitting device, and the lens of any one of claims 1 to 7;

the light source driver is used for driving the light-emitting device to emit a light signal according to the first signal generated by the distance measuring chip;

the light emitting device is used for emitting a light signal to a target object based on the driving of the first signal;

the lens is used for receiving the optical signal reflected by the target object and transmitting the optical signal to the ranging chip.
The range finder device of claim 8, wherein the light emitting device is a straight cavity surface emitting laser (VCSEL).
An electronic device, characterized in that the electronic device comprises a ranging apparatus according to claim 8 or 9, the electronic device further comprising:

and the calculating module is used for calculating the phase delay corresponding to the flight time of the optical signal between the distance measuring device and the target object according to the plurality of exposure values obtained by the distance measuring device.
A time-of-flight, ToF, based ranging method, comprising:

generating a first signal, the first signal comprising a plurality of first pulses, the first pulses having a first width T, the first signal being for emitting an optical signal towards a target object;

generating a second signal from the first signal, the second signal comprising the plurality of first pulses in the first signal and at least one second pulse delayed by the first width T from each of the plurality of first pulses;

and carrying out integration processing on the received optical signal reflected by the target object according to the second signal to obtain a plurality of exposure values, wherein the exposure values are used for calculating the phase delay corresponding to the flight time of the optical signal between the ranging chip and the target object.
The method of ranging of claim 11, wherein each of the at least one second pulse has a width of the first width T.
The ranging method according to claim 12, wherein the second pulse is a plurality of second pulses, and an interval between two adjacent second pulses of the plurality of second pulses is the first width T.
A ranging method as claimed in any of claims 11-13 wherein the integrating the received light signal reflected by the target object based on the second signal to obtain a plurality of exposure values comprises:

respectively carrying out delay operation on the second signals to obtain a plurality of third signals with different phases;

exposing the received optical signal reflected by the target object for multiple times according to the plurality of third signals with different phases to obtain a plurality of fourth signals;

and performing analog-digital conversion on the plurality of fourth signals to obtain a plurality of digital image arrays, wherein the plurality of digital image arrays comprise exposure values corresponding to a plurality of pixel points.
A ranging method as claimed in any of claims 11-14, wherein two adjacent first pulses of the plurality of first pulses are spaced apart by (N +1) × T, wherein N is a predetermined positive integer or a random positive integer.
The method according to any one of claims 11 to 15, wherein the delaying the second signal to obtain a plurality of third signals with different phases specifically comprises:

and performing m times of delay processing on the second signal to obtain m third signals, wherein the m times of delay processing comprise 0 phase delay processing, and the time difference of two adjacent delay processing in the m times of delay processing is 2T/m.
The ranging method according to any one of claims 11 to 16, wherein after the generating the first signal, the ranging method further comprises:

emitting an optical signal to the target object according to the first signal.
The ranging method of claim 17, wherein after the generating the first signal, the ranging method further comprises:

generating a delayed signal of the first signal;

the emitting the optical signal to the target object according to the first signal specifically includes: and transmitting the optical signal to the target object according to the delay signal of the first signal.
A ranging method as claimed in any of claims 11-18, wherein after integrating the received light signal reflected by the target object according to the second signal to obtain a plurality of exposure values, the ranging method further comprises:

and calculating the phase delay corresponding to the flight time of the optical signal between the distance measuring device and the target object according to the exposure values.
An electronic device comprising a processor, the processor coupled with a memory;

a memory for storing computer programs or instructions;

a processor for executing computer programs or instructions stored in the memory to enable an electronic device to perform the method of any of claims 11 to 19.
A computer readable storage medium storing a program or instructions, which when executed by a processor of an electronic device, enables the electronic device to perform the method of any one of claims 11 to 19.
A computer program product comprising a program or instructions which, when run on a computer, causes the computer to perform the method of any one of claims 11 to 19.