TWI711834B - Distance measuring device and method - Google Patents

Abstract

A distance measuring device includes a random pulse modulation generator, a laser diode, a photodetector, a time-to-digital converter, and a processing device. The random pulse modulation generator includes at least one single-photon avalanche diode (SPAD) configured to receive background photons and generate pulse to generate a random control signal when a background photon incident event or a dark count rate (DTR) event occurs. The laser diode is configured to receive a random control signal and generate a random pulsed laser therefrom and transmit toward a target. The photodetector is configured to receive a reflected random pulsed laser. The time digital converter receives the random control signal and records a first time during the random pulse laser transmission, and records a second time when the photodetector receives the reflected random pulse laser. The processing device is configured to calculate a distance of the target based on the first time and the second time.

Description

Ranging device and method

The present invention relates to a distance measuring device and method, in particular to a distance measuring device and method using a random pulse modulation generator to achieve an anti-interference effect.

In the application scenario of autopilot, it is inevitable for multiple systems to operate at the same time. How to avoid mutual interference between systems is a very important and must be solved. Among them, the direct time of flight ranging method is used. , D-ToF) is most susceptible to mutual interference between systems.

The direct time-of-flight ranging method measures the flight time of the laser from the launch to the photon received by the detector, and calculates the distance. Some of the detected incidents received the emitted laser, and some received the ambient light. In the existing ranging system, it is difficult to judge the type of the incident at the moment when the photon is received. However, after a period of statistics, it can be found that the time point of the background light reception is not related to the time point of the laser emission, and will be evenly distributed at each time point; while the events of receiving the rebound laser and the laser emission are highly time dependent The distribution of these events is very concentrated, so a peak can be found in the statistical distribution, and the location of the peak is the distance of the target.

However, when multiple sets of ranging systems emit lasers in the same mode, for example, they emit lasers at the same frequency, in addition to the high time dependence when receiving lasers from their own systems, when receiving lasers from other systems There will also be a high degree of time dependence. In the statistical results, there will be multiple peaks, so it is impossible to determine which is generated by the target and which is generated by other systems. Disturbance caused by shot lasers.

Therefore, there is an urgent need for a ranging device and method that can avoid interference caused by multiple systems during ranging.

The technical problem to be solved by the present invention is to provide a distance measuring device and method that utilizes a random pulse modulation generator to achieve an anti-interference effect in view of the shortcomings of the prior art.

In order to solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a distance measuring device, which includes a random pulse modulation generator, a laser diode, a light detector, a time-to-digital converter, and processing Device. The random pulse modulation generator includes at least one single-photon avalanche diode (SPAD), which is configured to receive background photons and occur during background photon incident events or dark count rate (DCR) events Generate pulses at time to generate random control signals. The laser diode is configured to receive the random control signal, and generate a random pulse laser based on it and launch it toward the target. The light detector is configured to receive the reflected random pulse laser. The time-to-digital converter receives the random control signal and records the first time when the random pulse laser is emitted, and records the second time when the light detector receives the reflected random pulse laser. The processing device is configured to calculate the distance of the target according to the first time and the second time.

In some embodiments, at least one SPAD generates multiple pulses with a desired number of events in a unit time, and the random control signal has a random characteristic following a Poisson random distribution.

In some embodiments, the number of at least one SPAD is plural, and the random pulse modulation generator further includes a first control circuit. The first control circuit includes a first signal combiner configured to The SPAD pulses are combined to generate the random control signal, and the expected number of events is proportional to the number of SPADs.

In some embodiments, the random pulse modulation generator further includes a second control circuit configured to determine whether the interval time between the pulses generated by the at least one SPAD is less than a minimum interval time, and if so, it will be less than the Pulse filtering with minimum interval time to generate the random control signal.

In some embodiments, the second control circuit includes a minimum interval time filter, which includes a first D-type flip-flop, an inverter, a first offset register counter, and a first AND gate. The input terminal of the first D-type flip-flop is connected to the at least one SPAD, and the clock terminal receives a first clock signal. The inverter has its first input terminal connected to the output terminal of the first D-type flip-flop, its second input terminal receives a first start signal, and its output terminal generates a first reset signal. The first offset register counter includes a plurality of second D-type flip-flops. The offset register counter receives the first reset signal and the first clock signal and is configured to generate the first start signal. The first and gate has a first input terminal connected to the random pulse modulation generator, and a second input terminal connected to the offset register counter, and outputs the random control signal at its output terminal.

In some embodiments, the random pulse modulation generator further includes a third control circuit configured to determine whether the interval between the pulses generated by the at least one SPAD is less than a minimum interval or greater than a maximum interval. . Wherein, if the third control circuit determines that the interval time between the pulses generated by the at least one SPAD is less than the minimum interval time, it filters the pulses that are less than the minimum interval time to generate the random control signal. Wherein, if the third control circuit determines that the interval time between the pulses generated by the at least one SPAD is greater than the maximum interval time, it is forced to insert a forced pulse signal into the random control signal.

In some embodiments, the third control circuit includes a time boundary controller. The time boundary controller includes a third D-type flip-flop, a second AND gate, a reverse OR gate, a second offset temporary storage counter, a third AND gate, a monostable trigger circuit and an OR gate. The input terminal of the third D-type flip-flop is connected to the at least one SPAD, and the clock terminal receives a second clock signal. The second and gate, its first input is connected to the The output terminal of the third D-type flip-flop, the second input terminal of which receives a second start signal, and the output terminal of which generates a second reset signal. Inverted OR gate, its first input terminal receives the second reset signal, its second input terminal receives an insert signal, and its output terminal outputs a third reset signal. The second offset temporary storage counter includes a plurality of fourth D-type flip-flops, the second offset temporary storage counter receives the third reset signal and the second clock signal, and is configured to generate the second activation Signal and the inserted signal. The third and gate has its first input terminal connected to the random pulse modulation generator, its second input terminal receives the second start signal, and its output terminal outputs a fourth reset signal. The monostable trigger circuit is connected to the second offset temporary storage counter, is controlled by the insertion signal, and outputs the forced pulse signal. Or gate, its first input terminal receives the fourth reset signal, its second input terminal receives the forced pulse signal, and its output terminal outputs the random control signal.

In some embodiments, the number of the at least one SPAD is plural, and the random pulse modulation generator includes a signal combiner configured to combine the pulses of the SPAD to generate the random pulse when a dark counting event occurs. Control signal. Among them, the SPADs generate a plurality of pulses by occurrence of dark counting events with a desired number of first events in a unit time.

In some embodiments, the number of the at least one SPAD is one, and the SPAD is configured to generate a number of dark count events with a second event expected number within a unit time to generate multiple pulses.

In some embodiments, the time-to-digital converter calculates the distance of the target according to the time difference between the first time and the second time.

In order to solve the above technical problem, another technical solution adopted by the present invention is to provide a ranging method, which includes: configuring a random pulse modulation generator to generate a random control signal, wherein the random pulse modulation generator includes At least one single-photon avalanche diode (SPAD) is configured to receive background photons and generate pulses when a background photon incident event or dark count rate (DCR) event occurs, to generate the Follow Machine control signal; configure a laser diode to receive the random control signal, and generate a random pulse laser and launch it toward a target; configure a light detector to receive the reflected random pulse laser; configure a time digit When the random pulse laser is emitted, the converter receives the random control signal and records a first time, and records a second time when the light detector receives the reflected random pulse laser; and configures the time The digital converter calculates the distance of the target according to the first time and the second time.

In some embodiments, the at least one SPAD generates multiple pulses with a desired number of events in a unit time, and the random control signal has a random characteristic following a Poisson random distribution.

In some embodiments, the number of at least one SPAD is plural, and the ranging method further includes: configuring a first signal combiner of the random pulse modulation generator to combine the pulses of the SPADs to generate the Random control signal, in which the expected number of events is proportional to the number of SPADs.

In some embodiments, the ranging method further includes configuring a second control circuit to determine whether the interval time between the pulses generated by the at least one SPAD is less than a minimum interval time, and if so, filtering pulses less than the minimum interval time To generate the random control signal.

In some embodiments, the second control circuit includes a minimum interval time filter, which includes a first D-type flip-flop, an inverter, a first offset register counter, and a first AND gate. The input terminal of the first D-type flip-flop is connected to the at least one SPAD, and the clock terminal receives a first clock signal. The inverter has its first input terminal connected to the output terminal of the first D-type flip-flop, its second input terminal receives a first start signal, and its output terminal generates a first reset signal. The first offset register counter includes a plurality of second D-type flip-flops. The offset register counter receives the first reset signal and the first clock signal and is configured to generate the first start signal. The first and gate, its first input terminal is connected to the random pulse modulation generator, and its second input terminal is connected to the offset register counter, and is output at its output terminal Out the random control signal.

In some embodiments, the ranging method further includes configuring a third control circuit to determine whether the interval time between the pulses generated by the at least one SPAD is less than a minimum interval time or greater than a maximum interval time. Wherein, if the third control circuit determines that the interval time between the pulses generated by the at least one SPAD is less than the minimum interval time, it filters the pulses that are less than the minimum interval time to generate the random control signal. If the third control circuit determines that the interval time between the pulses generated by the at least one SPAD is greater than the maximum interval time, it is forced to insert a forced pulse signal into the random control signal.

In some embodiments, the third control circuit includes a time boundary controller. The time boundary controller includes a third D-type flip-flop, a second AND gate, a reverse OR gate, a second offset temporary storage counter, a third AND gate, a monostable trigger circuit and an OR gate. The input terminal of the third D-type flip-flop is connected to the at least one SPAD, and the clock terminal receives a second clock signal. For the second and gate, the first input terminal is connected to the output terminal of the third D-type flip-flop, the second input terminal receives a second start signal, and the output terminal generates a second reset signal. Inverted OR gate, its first input terminal receives the second reset signal, its second input terminal receives an insert signal, and its output terminal outputs a third reset signal. The second offset temporary storage counter includes a plurality of fourth D-type flip-flops, the second offset temporary storage counter receives the third reset signal and the second clock signal, and is configured to generate the second activation Signal and the inserted signal. The third and gate has its first input terminal connected to the random pulse modulation generator, its second input terminal receives the second start signal, and its output terminal outputs a fourth reset signal. The monostable trigger circuit is connected to the second offset temporary storage counter, is controlled by the insertion signal, and outputs the forced pulse signal. Or gate, its first input terminal receives the fourth reset signal, its second input terminal receives the forced pulse signal, and its output terminal outputs the random control signal.

In some embodiments, the number of at least one SPAD is plural, and the ranging method further includes configuring a second signal combiner of the random pulse modulation generator, configured to count in the dark When an event occurs, the SPAD pulses are combined to generate the random control signal. Among them, the SPADs generate a plurality of pulses by occurrence of dark counting events with the expected number of first events in a unit time.

In some embodiments, the number of at least one SPAD is one, and the SPAD has a dark count event with a desired number of second events in a unit time to generate multiple pulses.

In some embodiments, the ranging method further includes configuring the time-to-digital converter to calculate the distance of the target according to the time difference between the first time and the second time.

One of the beneficial effects of the present invention is that the ranging device and method provided by the present invention can use SPAD as a random signal generation source to implement the SPPM anti-interference method, thereby avoiding interference between multiple ranging systems.

In order to further understand the features and technical content of the present invention, please refer to the following detailed description and drawings about the present invention. However, the provided drawings are only for reference and description, and are not used to limit the present invention.

1: Ranging device

100: Random pulse modulation generator

102: Laser diode

104: light detector

106: Time to Digital converter (TDC)

108: processing device

SPAD1, SPAD2,..., SPADN: Single photon collapse diode

SR: Random control signal

RPL, RPL’: Random pulse laser

OBJ: target

HTG: Statistics

T1: the first time

T2: second time

CT1: The first control circuit

SMG: Signal Combiner

CT2: second control circuit

Trej: minimum interval time

DFF1: The first D-type flip-flop

NAND: reverse and gate

SRC1: First offset temporary storage counter

AG1: First and gate

clk1: the first clock signal

D: Input

Q: output

act1: the first activation signal

rst1: The first reset signal

DFF21, DFF22, DFF23,..., DFF2i: the second D-type flip-flop

INV1: the first inverter

AG, AG’: and gate

CT3: The third control circuit

DFF3: The third D-type flip-flop

AG2: Second and gate

NOR: reverse or gate

SRC2: Second offset temporary storage counter

AG3: Third and gate

MC: Monostable trigger circuit

OG: Or gate

clk2: second clock signal

act2: second activation signal

rst2: second reset signal

ins: insert signal

rst3: The third reset signal

DFF41, DFF42, DFF43,..., DFF4i,..., DFF4j: Fourth D-type flip-flop

INV2: second inverter

insp: forced start pulse

rst4: The fourth reset signal

INP: the first input

t: time

FIG. 1 is a block diagram of a distance measuring device according to an embodiment of the present invention.

2A and 2B are block diagrams and signal timing diagrams of a random pulse modulation generator according to an embodiment of the invention.

3A and 3B are another block diagrams of a random pulse modulation generator according to an embodiment of the present invention and a plot of probability density after adjusting the minimum interval time against the event interval time.

4A and 4B are another block diagrams of the random pulse modulation generator according to an embodiment of the present invention and another plot of probability density after adjusting the minimum interval time against the event interval time.

FIG. 5 is a graph of the distance measurement result of the distance measurement device according to the embodiment of the present invention.

Fig. 6 is a flowchart of a ranging method according to an embodiment of the present invention.

FIG. 7 is another flowchart of the ranging method according to the embodiment of the present invention.

FIG. 8 is another flowchart of the ranging method according to the embodiment of the present invention.

The following is a specific specific embodiment to illustrate the implementation of the "ranging device and method" disclosed in the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are merely schematic illustrations, and are not drawn according to actual dimensions, and are stated in advance. The following embodiments will further describe the related technical content of the present invention in detail, but the disclosed content is not intended to limit the protection scope of the present invention.

It should be understood that although terms such as “first”, “second”, and “third” may be used herein to describe various elements or signals, these elements or signals should not be limited by these terms. These terms are mainly used to distinguish one element from another, or one signal from another signal. In addition, the term "or" used in this document may include any one or a combination of more of the associated listed items depending on the actual situation.

Please refer to FIG. 1, which is a block diagram of a distance measuring device according to an embodiment of the present invention. As shown in FIG. 1, the first embodiment of the present invention provides a distance measuring device 1, which includes a random pulse modulation generator 100, a laser diode 102, a light detector 104, and a time to digital converter (Time to Digital). converter, TDC) 106 and processing device 108.

The random pulse modulation generator 100 includes a SPAD1 (Single-photon avalanche diode, SPAD), which is configured to receive background photons and occur during background photon incident events or dark count rate (DCR) events Generate a pulse at time to generate a random control signal SR.

The laser diode 102 is used to receive the random control signal SR, and generate a random pulse based on it Shoot the laser RPL and launch towards the target OBJ. The light detector 104 is used to receive the reflected random pulse laser RPL', and the TDC 106 receives the random control signal SR and records the first time T1 when the random pulse laser RPL is emitted, and the laser diode receives it The reflected random pulse laser RPL' records the second time T2. After multiple cycles, the TDC 106 can further generate statistical data HTG and output it to the processing device 106, and the processing device 108 further depends on the recorded first time T1 and The second time T2 calculates the distance of the target OBJ.

In detail, Single-Photon Avalanche Diode (SPAD) has been widely used in recent years due to its advantages of high sensitivity, high time accuracy, compatibility with CMOS standard manufacturing process and output as a digital signal. Among them, when the single photon breakdown diode SPAD1 detects a photon, it will output a pulse signal, and there will be a dead time that cannot detect the photon after each detection.

Among them, when SPAD is working, its active area operates on the reverse-biased p-n junction, and when the p-n junction collapses, it means that an event is detected. However, when the photon is not absorbed, there are still many mechanisms that will cause the probability of collapse, and most of the events generated by the mechanisms are independent of each other.

In addition, when the SPAD is not illuminated, the average crash count (Count Rate) of the component per second is called the Dark Count Rate (DCR). In this embodiment, the random characteristic of the dark counting event is used, so that SPAD can be applied to the random pulse modulation generator 100.

Specifically, the present invention utilizes the randomness of SPAD background photon receiving events and dark counting events, and uses SPAD as a natural random signal generation source (Random Pattern Generator). Such random signals are the product of the laws of nature and cannot be predicted or copied. In the present invention, this modulation is called Stochastic Pulse Position Modulation (SPPM), which includes the use of SPAD as a signal generation source and a control circuit at the back end. The present invention further provides a plurality of circuit structures, so that the random signal generation source can be adjusted and applied to different systems while maintaining its randomness.

The random control signal generated by SPAD1 has a random characteristic following the random distribution of Poisson. The following describes the characteristic of Poisson distribution. Two parameters can be used to describe the random events generated by SPAD1, one is the expected number of events λ, and the other is the dead time τ. The expected number of events λ is the expected value of photon receiving events that occur in a unit time. When a photon receiving event occurs, SPAD1 generates pulses, and the unit time can be an average time. The more average time, the more events will be generated, and vice versa. less. The dead time τ represents the minimum time between two events. When the dead time τ is not 0, the distribution probability p _λ,τ (t) can be obtained as shown in the following formula (1):

The random signal generated by SPAD1 will be affected by ambient light and the dark count (DCR) of the component itself. The stronger the ambient background light, the greater the expected number λ of events that generate random signals. The larger the case count of the component itself, the larger the expected number λ of events that generate random signals. By controlling the expected number of events λ and the dead time τ, the requirements of different systems can be met.

Please refer to FIG. 2A and FIG. 2B, which are a block diagram and a signal timing diagram of a random pulse modulation generator according to an embodiment of the present invention. As shown in the figure, the random pulse modulation generator 100 may include a plurality of SPADs, such as SPAD1, SPAD2,..., SPAD, and the random pulse modulation generator 100 further includes a first control circuit CT1, which includes a first signal The combiner SMG1 is configured to combine the pulses of SPAD1, SPAD2,..., SPADN to generate a random control signal SR, and the expected number of events λ is proportional to the number of SPAD1, SPAD2,..., SPADN.

In this embodiment, the first signal combiner SMG1 is used to add the pulse signals of multiple SPADs to solve the problem that the expected number of events λ of a single element is not large enough. As shown in Figure 2B, the horizontal axis is time t, and the signal generated by the addition of multiple sets of random signals is equivalent to a Poisson process with a large expected number of events λ. In some embodiments, when the pulse signals of multiple SPADs are combined, the signal width can be reduced first to avoid coincidence of events.

As shown in the embodiment of FIG. 2A, the number of SPADs can be plural, and random pulses The modulation generator 100 includes a first control circuit CT1, which includes a signal combiner SMG, configured to combine the SPAD pulses to generate a random control signal SR when a dark count event occurs. Here, when multiple SPADs have dark count events with the expected number of first events occurring within a unit time, the generated multiple pulse signals can be combined by the signal combiner SMG, so as to randomly control the expected events of the signal SR The number is rising. It should be noted that the expected number of first events refers to a situation in which SPAD has a low incidence of dark count events per unit time, for example, within the range of... On the other hand, if the SPAD has a dark count event with the expected number of second events occurring within a unit time, the number of SPAD can be one, and the signal combiner SMG can be omitted. The expected number of second events refers to a situation in which SPAD has a high occurrence rate of dark count events per unit time, and is, for example, within the range of. In addition, one or more SPADs can be set to receive the background light, and the number of SPADs can be adjusted according to the needs of the system, and it is also possible to decide whether to set up a signal combiner.

On the other hand, in addition to adjusting the expected number of events λ, the minimum interval between two events can also be adjusted. Please refer to FIGS. 3A and 3B, which are another block diagram of the random pulse modulation generator according to an embodiment of the present invention and the probability density after adjusting the minimum interval time is plotted against the event interval time.

For example, if there is a minimum inter-arrival time or rejection time Trej limitation (such as a limitation on a laser or a limitation on a ranging method) on the system, the embodiment of the present invention further provides a limitation As shown in the figure, the random pulse modulation generator 100 further includes a second control circuit CT2, which is configured to determine whether the interval between the pulses generated by SPAD1 is less than the minimum interval Trej, and if so, Filter pulses less than the minimum interval time Trej to generate a random control signal SR.

In this embodiment, the second control circuit CT2 may include a minimum interval time filter, which includes a first D-type flip-flop DFF1, an inverter NAND, a first offset register counter SRC1, and a first AND gate AG1.

As shown in the figure, the input terminal D of the first D-type flip-flop DFF1 is connected to SPAD1, and its clock terminal receives the first clock signal clk1. The first input terminal of the NAND gate is connected to the output terminal Q of the first D-type flip-flop, the second input terminal receives the first activation signal act1, and the output terminal generates the first reset signal rst1.

Furthermore, the first offset temporary storage counter SRC1 includes a plurality of second D-type flip-flops DFF21, DFF22, DFF23,..., DFF2i, a first inverter INV1 and a plurality of AND gates AG, and the first offset The shift register counter SRC1 receives the first reset signal rst and the first clock signal clk1, and is configured to generate the first start signal act1. Among them, the first inverter INV1 receives the first reset signal rst, and inputs the second flip-flop DFF21 after inversion processing. The clock end of the second flip-flop DFF21 also receives the first clock signal clk1, and its output The terminal Q is connected to the input terminal of the gate AG, and the other input terminal of the gate AG receives the first reset signal rst1, and the above configuration is repeated. Among them, by controlling the number of the second D-type flip-flops DFF21, DFF22, DFF23,..., DFF2i, different minimum interval times Trej can be adjusted and obtained.

The first input terminal INP of the first and gate AG1 is connected to SPAD1, and the second input terminal is connected to the first offset register counter SRC1, and the random control signal SR is output at its output terminal. Through the above minimum interval filter configuration, events that are too close can be filtered out.

As shown in FIG. 3B, when the minimum interval time Trej is adjusted to 200 ns and 1 μs, no events will begin to occur until the event interval time reaches 200 ns and 1 μs, and the probability density remains basically unchanged. Moreover, by adjusting the minimum interval time Trej, it can be equivalent to prolonging the dead time of the system, which can be adapted to different system requirements.

On the other hand, the system may need to control the maximum spacing of random signals to avoid low system efficiency. Please refer to FIG. 4A and FIG. 4B, which are another block diagram of the random pulse modulation generator according to the embodiment of the present invention and another plot of probability density after adjusting the minimum interval time against the event interval time. As shown in the figure, the random pulse modulation generator 100 further includes a third control circuit CT3 configured to Determine whether the interval between multiple pulses generated by SPAD is less than the minimum interval or greater than the maximum interval.

Wherein, if the third control circuit CT3 determines that the interval time between the multiple pulses generated by SPAD is less than the minimum interval time, it will filter the pulses less than the minimum interval time to generate the random control signal SR, and if the third control circuit It is determined that the interval time between the multiple pulses generated by the SPAD is greater than the maximum interval time, and the forced pulse signal INS is forced to be inserted into the random control signal SR.

In detail, if no event is generated after reaching the set maximum interval, the third control circuit CT3 will add an event. In this embodiment, two timer circuits can be set to control the maximum time interval and the minimum time interval respectively. In addition to filtering events that are too close, events can be inserted when there is no event for too long.

As shown in FIG. 4A, the third control circuit CT3 can be used as a time boundary controller, which includes a third D-type flip-flop DFF3, a second AND gate AG2, a reverse OR gate NOR, a second offset temporary storage counter SRC2, The third and gate AG3, the monostable trigger circuit MC and the OR gate OG.

The input terminal D of the third D-type flip-flop DFF3 is connected to SPAD1, and its clock terminal receives the second clock signal clk2. The first input terminal of the second and gate AG2 is connected to the output terminal Q of the third D-type flip-flop DFF3, the second input terminal receives the second activation signal act2, and the output terminal generates the second reset signal rst2.

The first input terminal of the NOR gate receives the second reset signal rst2, the second input terminal receives the insert signal ins, and the output terminal outputs the third reset signal rst3.

On the other hand, the second offset temporary storage counter SRC2 includes a plurality of fourth D-type flip-flops DFF41, DFF42, DFF43,..., DFF4i,..., DFF4j, a second inverter INV2, a plurality of and Gate AG', the second offset register counter SRC2 receives the third reset signal rst3 and the second clock signal clk2, and is configured to generate the second start signal act2 and the insert signal ins. Among them, the second inverter INV2 receives the third reset signal rst3, and inputs the fourth flip-flop DFF41 after the inversion process, and the fourth flip-flop The clock terminal of DFF41 simultaneously receives the second clock signal clk2, its output terminal Q is connected to the input terminal of the gate AG', and the other input terminal of the gate AG' receives the third reset signal rst3, and the above configuration is repeated . Among them, by controlling the number of the fourth D-type flip-flops DFF41, DFF42, DFF43,..., DFF4i,..., DFF4j, different minimum and maximum intervals can be adjusted and obtained. Further, the output terminal Q of the fourth D-type flip-flop DFF4j inputs the insertion signal ins to the input terminal of the OR gate OG and the monostable trigger circuit MC, the first input terminal of the third and gate AG3 is connected to SPAD, and its second input The terminal receives the second activation signal act2, and its output terminal outputs the fourth reset signal rst4.

The monostable trigger circuit MC is connected to the second offset temporary storage counter SRC2, which is controlled by the insert signal ins and outputs a forced start pulse insp, or the first input terminal of the gate OG receives the fourth reset signal rst4, and its second input terminal Receive the forced start pulse insp, and its output terminal outputs the random control signal SR4.

As shown in Figure 4B, when the minimum interval time and the maximum interval time are limited by the above configuration, compared with the experimental data that only limits the minimum interval time, when the maximum interval time is limited to about 1500ns, an event will be forced to be generated and forced by output The pulse insp is started to generate an event at an interval of about 1500 ns, where the probability density of events is increased.

Further refer to FIG. 5, which is a graph of the distance measurement result of the distance measurement device according to the embodiment of the present invention. As shown in the figure, in addition to the laser used for distance measurement using the TDC 106 in the foregoing embodiment, different interference sources are additionally added. Among them, it can be seen from Figure 5 that when the interference source increases, the peak position of the ranging will not change. The difference is that the incident count of photons generated by the background light is changed. Therefore, it can be proved that since the interference laser signal has no specific time relationship with the SPPM random laser used for ranging, the ranging device provided by the present invention clearly has Anti-jamming characteristics.

In the above embodiment, the processing device 108 may adopt a time-of-flight ranging method to calculate the distance of the target OBJ according to the time difference between the first time T1 and the second time T2. However, the interval between laser shots using this method must be greater than the max time of flight, in other words, It needs to be achieved by limiting the minimum interval time between two events in the foregoing embodiment. On this basis, the present invention provides another way to record all events within the maximum flight time after the laser is launched, that is, after the first time T1, through the TDC 106, and configure the processing device 108 to calculate the distance of the target OBJ accordingly . Therefore, it is not necessary to limit the minimum interval time. Compared with the time-of-flight ranging method, its advantage is that it can control the laser irradiation more intensively, and can accumulate more measurement results in the same time. Therefore, the ranging integration time can be shortened.

Refer to FIG. 6, which is a flowchart of a ranging method according to an embodiment of the present invention. Among them, the embodiment of the present invention additionally provides a distance measurement method, which is applicable to the distance measurement device provided in the aforementioned embodiment of FIG. 1 to FIG. 5, and includes at least the following steps:

S100: Configure a random pulse modulation generator to generate random control signals. The random pulse modulation generator includes at least one SPAD configured to receive background photons and generate pulses when a background photon incident event or a dark count rate (DCR) event occurs to generate the random control signal.

S101: Configure laser diodes to receive random control signals, and generate random pulse lasers and launch them toward the target;

S102: Configure a light detector to receive the reflected random pulse laser;

S103: Configure the time-digital converter to receive the random control signal and record the first time when the random pulse laser is emitted, and record the second time when the light detector receives the reflected random pulse laser.

S104: The configuration processing device calculates the distance of the target according to the first time and the second time.

Refer to FIG. 7, which is another flowchart of the ranging method according to the embodiment of the present invention. In this embodiment, the ranging method further includes the following steps: Step S200 is performed after step S100: the second control circuit is configured to determine whether the interval time between the pulses generated by SPAD is less than the minimum interval time, and if so, proceed Step S201, filter pulses less than the minimum interval time to generate a random control signal, and proceed to step S101.

Refer to FIG. 8, which is another flowchart of the ranging method according to the embodiment of the present invention. In this embodiment, the ranging method further includes the following steps: Step S300 is executed after step S100: the third control circuit is configured to determine whether the interval between the pulses generated by the SPAD is less than the minimum interval or greater than the maximum interval.

If the third control circuit determines that the interval time between the pulses is less than the minimum interval time, step S301 is performed to filter the pulses that are less than the minimum interval time to generate a random control signal.

If the third control circuit determines that the interval time between the pulses is greater than the maximum interval time, step S302 is performed to force a forced pulse signal to be inserted into the random control signal.

It should be noted that the specific implementations of the second control circuit and the third control circuit have been described in the foregoing embodiments, so the repeated description is omitted.

[Beneficial effects of the embodiment]

One of the beneficial effects of the present invention is that the ranging device and method provided by the present invention can use SPAD as a random signal generation source to implement the SPPM anti-interference method, thereby avoiding interference between multiple ranging systems.

The content disclosed above is only a preferred and feasible embodiment of the present invention, and does not limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the description and schematic content of the present invention are included in the application of the present invention. Within the scope of the patent.

1: Ranging device

100: Random pulse modulation generator

102: Laser diode

104: light detector

106: Time to Digital converter (TDC)

108: processing device

SPAD1: Single photon collapse diode

SR: Random control signal

RPL, RPL’: Random pulse laser

OBJ: target

HTG: Statistics

T1: the first time

T2: second time

Claims (20)

A distance measuring device, which includes: a random pulse modulation generator, which includes at least one single-photon avalanche diode (SPAD), configured to receive background photons, and the background photon incident event or When a dark count rate (DCR) event occurs, pulses are generated to generate a random control signal; a laser diode is configured to receive the random control signal, and generate a random pulse laser based on it and directed toward one Target emission; a light detector configured to receive the reflected random pulse laser; a time-to-digital converter, when the random pulse laser is emitted, receive the random control signal and record a first time, and The light detector records a second time when the reflected random pulse laser is received; and a processing device is configured to calculate the distance of the target according to the first time and the second time. The distance measuring device according to claim 1, wherein the at least one SPAD generates a plurality of pulses with a desired number of an event in a unit time, and the random control signal has a random characteristic following a Poisson random distribution . The distance measuring device described in item 2 of the scope of patent application, wherein the number of the at least one SPAD is plural, and the random pulse modulation generator further includes a first control circuit, and the first control circuit includes a first The signal combiner is configured to combine the pulses of the SPADs to generate the random control signal, and the expected number of events is proportional to the number of the SPADs. As described in the first item of the scope of patent application, the random pulse modulation generator further includes a second control circuit configured to determine whether the interval time between the pulses generated by the at least one SPAD is less than A minimum interval time, if yes, filter pulses less than the minimum interval time to generate the random control signal. The distance measuring device according to item 4 of the scope of patent application, wherein the second control circuit includes a minimum interval time filter, which includes: a first D-type flip-flop, the input terminal of which is connected to the at least one SPAD, Its clock terminal receives a first clock signal; a flip and gate, its first input terminal is connected to the output terminal of the first D-type flip-flop, and its second input terminal receives a first start signal, and its output Terminal generates a first reset signal; a first offset temporary storage counter, including a plurality of second D-type flip-flops, the first offset temporary storage counter receives the first reset signal and the first clock A signal configured to generate the first start signal; and a first and gate, the first input of which is connected to the random pulse modulation generator, and the second input of which is connected to the first offset temporary storage counter, And output the random control signal at its output terminal. As described in the first item of the scope of patent application, the random pulse modulation generator further includes a third control circuit configured to determine whether the interval between the pulses generated by the at least one SPAD is less than A minimum interval time or greater than a maximum interval time, wherein if the third control circuit determines that the interval time between the pulses generated by the at least one SPAD is less than the minimum interval time, it will filter the pulses less than the minimum interval time, To generate the random control signal; wherein if the third control circuit determines that the interval time between the pulses generated by the at least one SPAD is greater than the maximum interval time, it is forced to insert a forced pulse signal into the random control signal. The distance measuring device according to item 6 of the scope of patent application, wherein the third control circuit includes: a time boundary controller, which includes: a third D-type flip-flop, the input terminal of which is connected to the at least one SPAD, Its clock Terminal receives a second clock signal; a second and gate, its first input terminal is connected to the output terminal of the third D-type flip-flop, its second input terminal receives a second start signal, and its output terminal generates A second reset signal; a reverse OR gate, its first input terminal receives the second reset signal, its second input terminal receives an insertion signal, and its output terminal outputs a third reset signal; a second bias The shift register counter includes a plurality of fourth D-type flip-flops. The second shift register counter receives the third reset signal and the second clock signal, and is configured to generate the second start signal and the second clock signal. Insert signal; a third and gate, the first input of which is connected to the random pulse modulation generator, the second input of which receives the second start signal, and the output of which outputs a fourth reset signal; a monostable A trigger circuit connected to the second offset temporary storage counter, controlled by the insertion signal, and output a forced start pulse; and an OR gate, the first input terminal of which receives the fourth reset signal, and the second input terminal of which receives The output end of the forced start pulse outputs the random control signal. As described in the first item of the scope of patent application, the number of the at least one SPAD is plural, and the random pulse modulation generator includes a signal combiner configured to combine when a dark counting event occurs The pulses of the SPADs are used to generate the random control signal, and the SPADs generate a number of dark count events with a first event expected number in a unit time to generate multiple pulses. The distance measuring device according to claim 1, wherein the number of the at least one SPAD is one, and the SPAD is configured to generate a dark count event with a desired number of a second event in a unit time to generate Multiple pulses. The distance measuring device described in item 1 of the scope of patent application, wherein the processing device calculates the distance of the target according to the time difference between the first time and the second time. A ranging method, which includes: configuring a random pulse modulation generator to generate a random control signal, wherein the random pulse modulation generator includes at least one single-photon avalanche diode (SPAD), Configured to receive background photons, and generate pulses when background photon incident events or dark count rate (DCR) events occur to generate the random control signal; configure a laser diode to receive the random control signal, and Generate a random pulse laser and emit it towards a target; configure a light detector to receive the reflected random pulse laser; configure a time-to-digital converter to receive the random control signal when the random pulse laser is emitted and record a A first time, and a second time is recorded when the light detector receives the reflected random pulse laser; and a processing device is configured to calculate the distance of the target according to the first time and the second time. The distance measurement method described in claim 11, wherein the at least one SPAD generates a plurality of pulses with a desired number of events in a unit time, and the random control signal has a random characteristic following a Poisson random distribution. The ranging method according to item 12 of the scope of patent application, wherein the number of the at least one SPAD is plural, and the ranging method further includes: configuring a first signal combiner of the random pulse modulation generator to The pulses of the SPADs are combined to generate the random control signal, wherein the expected number of events is proportional to the number of SPADs. For example, the distance measurement method described in item 11 of the scope of patent application further includes configuring a second control circuit to determine whether the interval time between the pulses generated by the at least one SPAD is less than a minimum interval time, and if so, it will be less than the Pulse filtering with minimum interval time to generate the random control signal. The distance measurement method described in item 14 of the scope of the patent application, wherein the second control circuit It includes a minimum interval time filter, which includes: a first D-type flip-flop, the input end of which is connected to the random pulse modulation generator, the clock end of which receives a first clock signal; a reverse and gate, The first input terminal is connected to the output terminal of the first D-type flip-flop, the second input terminal receives a first start signal, and the output terminal generates a first reset signal; a first offset temporary storage counter , Including a plurality of second D-type flip-flops, the first offset register counter receives the first reset signal and the first clock signal, and is configured to generate the first start signal; and a first and The gate has a first input terminal connected to the random pulse modulation generator, and a second input terminal connected to the first offset temporary storage counter, and outputs the random control signal at its output terminal. For example, the ranging method described in item 11 of the scope of patent application further includes configuring a third control circuit to determine whether the interval time between the pulses generated by the at least one SPAD is less than a minimum interval time or greater than a maximum interval time, Wherein if the third control circuit determines that the interval time between the pulses generated by the at least one SPAD is less than the minimum interval time, it will filter the pulses less than the minimum interval time to generate the random control signal; and if the The third control circuit determines that the interval time between the pulses generated by the at least one SPAD is greater than the maximum interval time, and then forcibly inserts a mandatory pulse signal into the random control signal. The distance measurement method according to item 16 of the scope of patent application, wherein the third control circuit includes: a time boundary controller, which includes: a third D-type flip-flop, the input terminal of which is connected to the random pulse modulation A generator, the clock terminal of which receives a second clock signal; a second and gate, the first input terminal of which is connected to the output terminal of the third D-type flip-flop, Its second input terminal receives a second start signal, and its output terminal generates a second reset signal; an inverted OR gate, its first input terminal receives the second reset signal, and its second input terminal receives an insert signal , Its output terminal outputs a third reset signal; a second offset temporary storage counter includes a plurality of fourth D-type flip-flops, the second offset temporary storage counter receives the third reset signal and the first Two clock signals, configured to generate the second start signal and the insertion signal; a third sum gate, the first input of which is connected to the random pulse modulation generator, and the second input of which receives the second start signal , Its output terminal outputs a fourth reset signal; a monostable trigger circuit connected to the second offset temporary storage counter, controlled by the insertion signal, and outputs a forced start pulse; and an OR gate, the first The input terminal receives the fourth reset signal, the second input terminal receives the forced start pulse, and the output terminal outputs the random control signal. The distance measurement method according to item 11 of the scope of patent application, wherein the number of the at least one SPAD is plural, and the distance measurement method further includes a second signal combiner configured with the random pulse modulation generator, configured When a dark counting event occurs, the pulses of the SPADs are combined to generate the random control signal, wherein the SPADs generate dark counting events with a desired number of first events in a unit time to generate multiple pulses. The distance measurement method described in claim 11, wherein the number of the at least one SPAD is one, and the SPAD has a dark count event with a second event expected number in a unit time to generate multiple pulses . The distance measurement method described in item 11 of the scope of the patent application further includes configuring the processing device to calculate the distance of the target according to the time difference between the first time and the second time.

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