CN117826126A - Time-of-flight ranging circuit, method and distance measuring system - Google Patents

Abstract

The application discloses time of flight ranging circuit, method and distance measurement system, this time of flight ranging circuit includes: the time-to-digital converter is used for receiving pulse electric signals of preset periods and converting the pulse electric signals of each period into corresponding time-to-digital signals; the histogram circuit is connected with the time-to-digital converter and comprises an energy storage array, and the histogram circuit is used for storing preset unit electric energy to corresponding energy storage devices in the energy storage array according to received time-to-digital signals so as to enable the corresponding energy storage devices in the energy storage devices to accumulate the electric energy and form a photon information histogram. The method and the device can effectively eliminate the interference of noise photons, obtain accurate time values by using accurate peak voltage, and are favorable for improving the reliability of distance measurement.

Description

Time-of-flight ranging circuit, method and distance measuring system

Technical Field

The present disclosure relates to the field of electronic circuits, and in particular, to a time-of-flight ranging circuit, a method, and a distance measuring system.

Background

In the time-of-flight ranging scheme, a distance measurement system based on the time-of-flight principle generally includes a transmitter and a collector, and the transmitter is used to transmit a pulse beam to illuminate an object to be measured and the collector is used to collect a reflected beam, and the time-of-flight of the beam from the transmission to the reflection is calculated to calculate the distance of the object to be measured. Compared with other indirect time-of-flight ranging methods, the high sensitivity of the photon time-of-flight ranging method enables the photon time-of-flight ranging method to have the advantage of long ranging distance. Because the laser receiver has very high sensitivity, the laser receiver is easily influenced by ambient background light noise, so that the ranging accuracy is influenced and the measuring result is easily interfered.

Content of the application

The main purpose of the application is to provide a flight time ranging circuit, a flight time ranging method and a flight time ranging system, and aims to improve the reliability of distance measurement.

To achieve the above object, the present application proposes a time-of-flight ranging circuit, including:

the time-to-digital converter is used for receiving pulse electric signals of preset periods and converting the pulse electric signals of each period into corresponding time-to-digital signals;

the histogram circuit is connected with the time-to-digital converter and comprises an energy storage array, and the histogram circuit is used for storing preset unit electric energy to corresponding energy storage devices in the energy storage array according to the received time-to-digital signal so as to enable the corresponding energy storage devices in the energy storage devices to accumulate the electric energy and form a photon information histogram.

Optionally, the histogram circuit further includes:

the charge injection circuit is connected with the time-to-digital converter, and is used for starting working when receiving the time-to-digital signal and outputting electric energy with preset charge quantity;

a switch array connected to the time-to-digital converter; the switch array is used for switching on a corresponding switch branch according to the time digital signal of each period so as to control an energy storage device connected with the switch branch to store the electric energy output by the charge injection circuit and accumulate the electric energy output by the charge injection circuit to form a photon information histogram.

Optionally, the switch array includes:

the control end of each switch branch is connected with the time-to-digital converter, the input end of each switch branch is connected with the output end of the charge injection circuit, and the output end of each switch branch is connected with a corresponding energy storage device in the energy storage array.

Optionally, each switch branch includes an electronic switch, the controlled end of the electronic switch is the controlled end of the switch energy storage branch, the input end of the electronic switch is the input end of the switch energy storage branch, the output end of the electronic switch is connected with the first end of the energy storage device, and the second end of the energy storage device is grounded.

Optionally, the time-of-flight ranging circuit further comprises:

the processor is connected in series between the time-digital converter and the switch array, and is used for controlling the conduction of a corresponding switch branch in the switch array according to the received time-digital signal so as to control a corresponding storage device to store the electric energy output by the charge injection circuit.

Optionally, the time-of-flight ranging circuit further comprises:

the photoelectric sensor is connected with the time-to-digital converter, and is used for receiving photons reflected by the measured object and generating corresponding pulse electric signals according to the received photon signals.

Optionally, the time-of-flight ranging circuit further comprises:

the histogram peak searching circuit is electrically connected with the energy storage array, and is used for searching the peak position in the photon information histogram according to the electric energy stored by each energy storage device in the energy storage array and determining the flight time of the photon signal according to the peak position.

Optionally, the time-of-flight ranging circuit further comprises:

and the laser emitter is used for sending laser photons with preset periods to the measured object.

The application also proposes a distance measurement system, a time-of-flight ranging circuit as described above.

The application also provides a time-of-flight ranging method, which uses the time-of-flight ranging circuit, wherein the time-of-flight ranging circuit comprises a charge injection circuit and a switch energy storage array consisting of a plurality of switch energy storage branches, and the time-of-flight ranging method comprises the following steps:

receiving pulse electric signals of preset periods, and converting the pulse electric signals of each period into corresponding time digital signals;

controlling the charge injection circuit to output electric energy with a preset charge amount when receiving the time digital signal; the method comprises the steps of,

and controlling the corresponding switch energy storage branch circuit in the switch energy storage array to work according to the time digital signal of each period so as to store the electric energy output by the charge injection circuit and form a photon information histogram.

The time-of-flight ranging circuit receives pulse electric signals corresponding to photon signals in a preset period through the time-to-digital converter, converts the pulse electric signals in each period into corresponding time-to-digital signals, outputs the corresponding time-to-digital signals to the histogram circuit, and enables the histogram circuit to store preset unit energy to corresponding energy storage devices in the energy storage array according to the received time-to-digital signals, so that each energy storage device in the energy storage device accumulates electric energy to form a photon information histogram, a peak searching circuit searches peaks according to the histogram to obtain signal peaks containing ranging information, the time-of-flight corresponding to photons is obtained according to the signal peaks, and then the distance of a measured object can be determined according to the time-of-flight. Compared with the traditional laser receiver circuit, the digital circuit is utilized to count photons in the time interval, so that a histogram of photon counts corresponding to the time signal is obtained through statistics, the pulse peak position in the histogram is determined, and the distance of the object is calculated according to the flight time corresponding to the pulse peak position. The time-of-flight ranging circuit is entirely composed of digital circuitry, thus occupying a large memory area and power consumption. In the scheme, the histogram circuit is constructed by adopting the analog circuit module, so that the storage area and the power consumption are saved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained from the structures shown in these drawings without inventive effort to a person of ordinary skill in the art.

FIG. 1 is a schematic diagram of a functional block diagram of an embodiment of a time-of-flight ranging circuit of the present application;

FIG. 2 is a schematic circuit diagram of an embodiment of a time-of-flight ranging circuit according to the present application;

FIG. 3 is a schematic diagram of histogram generation involved in the time-of-flight ranging circuit of the present application;

fig. 4 is a flowchart of an embodiment of a time-of-flight ranging method according to the present application.

Reference numerals illustrate:

reference numerals	Name of the name	Reference numerals	Name of the name
				10	Time-to-digital converter	23	Switch array
20	Histogram circuit	30	Laser transmitter
				21	Energy storage array	40	Photoelectric sensor
22	Charge injection circuit	50	Histogram peak finding circuit

The realization, functional characteristics and advantages of the present application will be further described with reference to the embodiments, referring to the attached drawings.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

It should be noted that, in the embodiment of the present application, directional indications (such as up, down, left, right, front, and rear … …) are referred to, and the directional indications are merely used to explain the relative positional relationship, movement conditions, and the like between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.

In addition, if there is a description of "first", "second", etc. in the embodiments of the present application, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be regarded as not exist and not within the protection scope of the present application.

The term "and/or" is herein merely an association relationship describing an associated object, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

The present application proposes a Time of Flight (TOF) ranging circuit.

The method and the device can be applied to the fields of consumer electronics, unmanned operation, AR/VR and the like, and the distance measurement can be carried out on the target by utilizing the flight time principle so as to acquire the depth image containing the depth value of the target.

Referring to fig. 1 and 2, in an embodiment of the present application, the time-of-flight ranging circuit includes:

a time-to-digital converter 10 (Time Digital Convertor, TDC) for receiving a pulse electrical signal of a preset period and converting the pulse electrical signal of each period into a corresponding time-to-digital signal;

the histogram circuit 20 is connected to the time-to-digital converter 10, the histogram circuit 20 includes an energy storage array 21, and the histogram circuit 20 is configured to store a preset unit of electric energy to a corresponding energy storage device in the energy storage array 21 according to the received time-to-digital signal, so that the corresponding energy storage device in the energy storage array 21 accumulates the electric energy to form a photon information histogram.

In this embodiment, the time-of-flight ranging circuit is further provided with a laser emitter 30 and a laser receiver, the laser emitter 30 emits laser, and the laser is reflected after being irradiated onto the detected object and received by the laser receiver; the TDC can measure the time of the process of laser emission, reflection and reception, namely the flight time T of the laser; and then according to the light speed C, the distance D between the detected object and the ranging system can be calculated as follows: d=ct/2. In photon time-of-flight ranging, the sensitivity of the laser receiver is extremely high, and even a single reflected photon can be received, and the TDC measures the time-of-flight of the laser photon. Therefore, the high sensitivity of photon time-of-flight ranging methods gives it the advantage of a far ranging distance compared to other indirect time-of-flight ranging methods. Since the laser receiver has a high sensitivity, it is susceptible to ambient background light noise, thereby affecting the ranging accuracy. To this end, during a measurement, the laser transmitter 30 may periodically transmit laser photons to the object under test, and obtain a plurality of time-of-flight information from the received photons reflected back from the object under test, thereby reaching the time-of-flight of photons associated with the object under test. For example, the laser emitter 30 sequentially emits laser photons to the object to be measured at a predetermined emission period (frequency), and the laser emitter 30 can emit a plurality of laser photons (e.g., M in the present embodiment) to the object to be measured at the time of one measurement being completed.

After the laser transmitter 30 transmits laser photons, the photoelectric sensor 40 can receive the photons and measure their photon flight time, specifically, after the photoelectric sensor 40 receives the photons, a corresponding pulse electric signal is generated and output to a time digital sensor, and the time digital sensor measures the arrival time of the pulse electric signal, so that the flight time information of the reflected photons can be obtained. Specifically, after the laser receiver receives the reflected photons and converts them to pulsed electrical signals for output, the TDC measures the time of flight of each reflected photon based on the arrival time of the pulsed electrical signals. Each time the TDC measures a time of flight, a time digital signal corresponding to the value of the time of flight is output according to the value tk of the measured time of flight, and the time digital signal can control the start-up and energy storage of the corresponding energy storage devices in the energy storage array 21. After the laser transmitter 30 periodically emits photons during one measurement, the number of photons received by the photosensor 40 is N. It will be appreciated that after the laser transmitter 30 emits laser photons, some of the laser photons may not be received by the photosensor 40, or the photosensor 40 may receive other noise photons, so that the number of N photons actually received by the photosensor 40 may not be equal to the number of M lasers, i.e., more than one photon may be received by the laser receiver per cycle, so that one measurement is completed, and the total number of reflected photons may be unequal to the total number of emitted photons.

The energy storage array 21 is provided with a plurality of energy storage devices, the plurality of energy storage devices are respectively marked as C1, C2 … and Cn, electric energy stored by each energy storage device can be accumulated, the number of the energy storage devices can be set according to the numerical intervals of two flight times, for example, the numerical intervals of the flight times can be set as unit moments, one energy storage device is arranged at each 1 moment in interval, each energy storage device Ck corresponds to the numerical tk of the flight time one by one, and the energy storage device has specific codes, namely the energy storage device C1 corresponds to the numerical t1 of the flight time, the energy storage device C2 corresponds to the numerical t of the flight time, and so on, and the energy storage device Cn corresponds to the numerical tn of the flight time. The energy storage devices start energy storage according to the time digital signals, only one energy storage device stores energy at the same time, and the states of the other energy storage devices are kept unchanged. Whether the energy storage device stores energy or not is determined based on a value tk of the flight time, for example, the laser receiver receives photons at the kth moment, and after TDC measurement, the flight time tk of the photons is obtained. In a measurement period, the TDC obtains one or more values tk of the time of flight, and controls the corresponding energy storage devices in the energy storage array 21 to store energy according to the measured value tk of the time of flight, that is, to inject a fixed charge quantity Qu into the energy storage device Ck corresponding to the value tk of the time of flight, at this time, the voltage of UCk rises Qu/C, and the electric quantity of the energy storage device which does not receive photons remains unchanged and does not increase. And after enough photons are measured in a preset period, the electric quantity on each energy storage device is accumulated to form a histogram represented by different voltage values, and the statistics of all photon flight time received in a plurality of periods is realized in a charge quantity accumulation storage mode.

In the ranging example with the cycle number of 4, counting the number of times of energy storage of each time of flight of the energy storage device, wherein the number of times of energy storage of each time of flight of the energy storage device is counted, the energy storage device C1 corresponding to the 1 st moment stores 1 time of unit quantity of electric charge, the energy storage device C2 corresponding to the 3 rd moment stores 1 time of unit quantity of electric charge, the energy storage device C7 corresponding to the 7 th moment stores 4 times of unit quantity of electric charge, the energy storage device C9 corresponding to the 9 th moment stores 1 time of unit quantity of electric charge, the energy storage device C11 corresponding to the 11 th moment stores 1 time of unit quantity of electric charge, and the energy storage device C14 corresponding to the 14 th moment stores 1 time of unit quantity of electric charge. The histogram peak searching circuit 50 following the histogram circuit 20 searches for the highest voltage in UC1, UC2 … … UCn and outputs the peak searching result. From this, the number of times corresponding to the electric quantity stored in the storage device C7 at the time 7 th time of flight is 4, the electric quantity stored in the storage device C7 is the largest, the voltage is the highest, and the time of flight t7 corresponding to the highest is the time of flight with the largest occurrence.

Because of the randomness of the noise photons, the noise photons only appear once or sporadically at the same moment, the distribution of the time values generated by the interference photons is equivalent to a random distribution, the accumulation of charges is less, and the true reflected photon signals are accumulated in the histogram. For example, when there are multiple noise photons, such as multiple measurement devices measuring interference, then the time of flight of each reflected photon measured may be different, and thus multiple peaks may be present. In this embodiment, the time of flight with the highest peak value may be selected and determined as the time of flight of the photon reflected by the object to be measured, for example, the time of flight 7 corresponds to 4 times of charging of the energy storage device, and is the time of flight with the highest occurrence number, and is in the peak position in the histogram, so the time 7 is the time of flight associated with the object to be measured, and the distance between the objects to be measured can be obtained according to the flight speed.

The time-of-flight ranging circuit receives pulse electric signals corresponding to photon signals in a preset period through the time-to-digital converter 10, converts the pulse electric signals in each period into corresponding time-to-digital signals, and outputs the corresponding time-to-digital signals to the histogram circuit 20, so that the histogram circuit 20 stores preset unit electric energy to corresponding energy storage devices in the energy storage array 21 according to the received time-to-digital signals, each energy storage device in the energy storage devices accumulates the electric energy to form a photon information histogram, so that the histogram peak searching circuit 50 can search peaks according to the histogram to obtain signal peaks containing ranging information, the flight time corresponding to photons is obtained according to the signal peaks, the distance of a measured object can be determined according to the flight time, interference of noise photons can be effectively eliminated, accurate time values can be obtained by using correct peak voltage, and the reliability of distance measurement is improved. Compared with the traditional laser receiver circuit, the digital circuit is utilized to count photons in the time interval, so that a histogram of photon counts corresponding to the time signal is obtained through statistics, the pulse peak position in the histogram is determined, and the distance of the object is calculated according to the flight time corresponding to the pulse peak position. The time-of-flight ranging circuit is entirely composed of digital circuitry, thus occupying a large memory area and power consumption. In this application, the histogram circuit 20 is constructed by using an analog circuit module, so that the memory area and the power consumption are saved.

Referring to fig. 1 and 2, in an embodiment, the histogram circuit 20 further includes:

a charge injection circuit 22 connected to the time-to-digital converter 10, the charge injection circuit 22 being configured to start operation when the time-to-digital signal is received, and output electric energy of a preset charge amount;

a switch array 23 connected to the time-to-digital converter 10; the switch array 23 is configured to turn on a corresponding switch branch according to the time digital signal of each period, so as to control an energy storage device connected to the switch branch to store the electric energy output by the charge injection circuit 22, and accumulate the electric energy output by the charge injection circuit 22 to form a photon information histogram.

In this embodiment, the charge injection circuit 22 may be implemented by a constant current source, and the charge injection circuit 22 may be further provided with a switch, and each time the charge injection circuit 22 receives a time digital signal, the operation is started, and a fixed charge amount Qu is output. The switch array 23 may be provided with a plurality of switch branches arranged in parallel, wherein a controlled end of each switch branch is connected to the time-to-digital converter 10, an input end of each switch branch is connected to an output end of the charge injection circuit 22, and an output end of each switch branch is connected to a corresponding one of the energy storage devices in the energy storage array 21. Based on the control of the time digital signal, when the photon flight time tk receives the time digital signal, the switch array 23 turns on the corresponding switch branch, and other switch branches maintain the off state to control the corresponding energy storage device to be connected with the charge injection circuit 22, so that the charge injection circuit 22 injects a fixed charge quantity Qu into the energy storage device Ck, and the voltage value UCk at two ends of the energy storage device rises Qu/C.

Each switch branch comprises an electronic switch, the controlled end of the electronic switch is the controlled end of the switch energy storage branch, the input end of the electronic switch is the input end of the switch energy storage branch, the output end of the electronic switch is connected with the first end of the energy storage device, and the second end of the energy storage device is grounded.

In this embodiment, the number of the electronic switches is plural, the plural electronic switches are respectively labeled as S1, S2 …, sn, each electronic switch is normally in an open state, and is closed when receiving the time digital signal, so that the charge injection circuit 22 injects charges into the corresponding energy storage device through the closed electronic switch. The energy storage devices in the energy storage array 21 may be capacitors, each of which has an equal capacitance value, and the electric quantity stored in a single time is equal, and is a fixed electric quantity injected by the electric charge injection circuit 22. It will be appreciated that when the corresponding electronic switch branch in the switch array 23 is turned on, the capacitor stores the amount of electricity of the fixed charge amount injected by the charge injection circuit 22, the on time of the electronic switch may be the time when the fixed charge amount injected by the charge injection circuit 22 is completed, and thereafter the electronic switch is turned off, since the capacitor has no discharging circuit, the charge can be stored in the capacitor, and each time the electronic switch is turned on, the capacitor stores the amount of electricity once, so that the amount of electricity stored by the capacitor of the fixed charge amount injected can be accumulated. For example, in the first period, when a photon is received at the kth moment, the kth electronic switch Sk is turned on at the kth moment to charge the capacitor Ck corresponding to the kth electronic switch Sk, and when a photon is received, the electronic switch corresponding to the kth electronic switch Sk is turned on at the corresponding moment until one period is finished, the next period is entered, and the cycle is performed in such a way, so that the storage of the charge quantity corresponding to each flight time in all periods is completed. After the measurement process is completed, the electric quantity stored by each capacitor is different in height due to different opening times of the switch branch, the voltages at two ends of the capacitor are different according to the different electric quantities stored by the capacitor, and the histogram peak searching circuit 50 can obtain the flight time corresponding to photons by acquiring the capacitor with the highest voltage, so that the distance of the measured object can be determined according to the flight time.

Referring to fig. 1 and 2, in an embodiment, the time-of-flight ranging circuit further comprises:

a processor (not shown) is disposed in series between the time-to-digital converter 10 and the switch array 23, and the processor is configured to control the corresponding switch branch in the switch array 23 to be turned on according to the received time-to-digital signal, so as to control the corresponding storage device to store the electric energy output by the charge injection circuit 22.

In this embodiment, the processor may be implemented by a gate single-chip microcomputer, an FPGA, a DSP, or other microprocessors, and the processor may also be implemented by a MUX, where the processor may be integrated with the time-to-digital converter 10, and the time-to-digital converter 10 may implement conversion from an amount of time to a digital amount according to an arrival time of a pulse electric signal, and output a digital code representing a flight time of a reflected photon, and also may implement a real-time digital signal, and the processor may control the switch branch of the corresponding code in the switch array 23 to be turned on according to the digital code, so that the corresponding coded energy storage device may receive and charge a fixed charge amount output by the charge injection circuit 22, and charge the corresponding coded energy storage device, so that a voltage across the energy storage device is increased. For example, when the photoelectric sensor 40 receives a photon at the kth moment, a time digital signal representing the flight time tk of the photon is output to the processor, and the processor controls the kth switching branch to be turned on, so as to control the charge injection circuit 22 to charge the kth capacitor, i.e. the energy storage device, and complete the electric energy accumulation at the kth moment. Thus, each time the processor receives a time digital signal, the switch branch of the corresponding path is controlled to be conducted, electric energy storage of the capacitor corresponding to the photon flight time is completed, the next period is started until one period is finished, and the cycle is performed, so that electric charge quantity storage corresponding to each flight time in all periods is completed.

Referring to fig. 1, in an embodiment, the time-of-flight ranging circuit further comprises:

the laser emitter 30 is used for sending laser photons with preset period to the measured object.

In this embodiment, when the distance of the measured object needs to be measured, the laser emitter 30 emits a laser beam to the surface of the measured object, so that the measured object reflects the laser beam, and the distance of the measured object is determined according to the flight time of the received reflected photon. The laser transmitter 30 may be provided with a light source, a transmitting optical element, a driver, etc. The light source can emit light beams with a preset period of laser outwards at a certain frequency (pulse) under the control of the flight time ranging circuit, the pulse light beams are projected onto the surface of a measured object through the emission optical element, the frequency is set according to measurement precision, distance and the like, the power and the period number of the laser light beams emitted by the laser emitter 30 can be set to be different, for example, the higher the precision is, the more the period number emitted by the laser emitter 30 is, the more the number of photons received by the photoelectric sensor 40 is, the higher the peak value in the photon information histogram is, and the interference of noise photons on measurement can be reduced. The farther the distance is, the larger the laser power can be set to reduce the interference caused by signal attenuation caused by the electric energy loss of the reflected photons.

The present application uses the laser transmitter 30 to periodically emit laser light to the object to be measured, and the time-to-digital converter 10 measures the time of flight of each reflected photon after the reflected photon reflected by the object to be measured is received by the photosensor 40. When the TDC measures a time of flight, according to the measured value tk of the time of flight, the corresponding switch Sk in the switched capacitor array is controlled to be closed, and other switches are controlled to maintain an open state, and at the same time, the charge injection circuit 22 injects a unit charge Qu into the capacitor in the switched capacitor branch; the analog voltage value on the corresponding capacitor Ck increases Qu/C. After a certain period of circulation is performed, when enough photons are measured, the peak searching circuit in the histogram circuit 20 searches the highest voltage in UC1 and UC2 … … UCn, and outputs a peak searching result.

Referring to fig. 1 and 2, in an embodiment, the time-of-flight ranging circuit further comprises:

and the photoelectric sensor 40 is connected with the time-to-digital converter 10, and the photoelectric sensor 40 is used for receiving photons reflected by the measured object and generating corresponding pulse electric signals according to the received photon signals.

In this embodiment, the photoelectric sensor 40 may be implemented by using sensors such as an APD avalanche photodiode, a SPAD single photon avalanche photodiode, or a CCD detector, where the photoelectric sensor 40 collects photons in a pulse periodic beam reflected by a measured object, generates a pulse electric signal, and outputs the pulse electric signal to the time-to-digital converter 10, so that the time-to-digital converter 10 determines a photon flight time according to the pulse electric signal, and converts the received pulse electric signal into a corresponding time-to-digital signal, thereby completing photon time measurement. In some embodiments, the time-of-flight ranging circuit may also include a signal amplifier or the like to which the photosensor 40 is connected.

Referring to fig. 1 and 2, in an embodiment, the time-of-flight ranging circuit further comprises:

the histogram peak searching circuit 50 is electrically connected with the energy storage array 21, and the histogram peak searching circuit 50 is configured to search a peak position in a photon information histogram according to the electric energy stored by each energy storage device in the energy storage array 21, and determine a flight time of the photon signal according to the peak position.

In this embodiment, in order to reduce the influence of noise, the present embodiment calculates the time of flight of the received reflected photons to obtain a histogram, and then, the histogram peak-searching circuit 50 searches the histogram for a peak value, and the time of flight of the received reflected photons is obtained according to the position of the peak value of the histogram. The histogram peak searching circuit 50 can be implemented by using a plurality of comparators, and the comparators can sequentially compare the voltage amplitudes in the histogram to obtain the peak position in the photon information histogram, so as to find the energy storage device with the highest voltage amplitude, obtain the flight time corresponding to the photons according to the codes of the energy storage device, and further determine the distance of the measured object according to the flight time.

The application also proposes a distance measurement system, a time-of-flight ranging circuit as described above.

The detailed structure of the time-of-flight ranging circuit can refer to the above embodiments, and will not be described herein; it can be understood that, because the time-of-flight ranging circuit is used in the time-of-flight ranging circuit control system, the embodiments of the time-of-flight ranging circuit control system include all the technical schemes of all the embodiments of the time-of-flight ranging circuit, and the achieved technical effects are identical, and are not repeated herein.

The application also provides a time-of-flight ranging method, which uses the time-of-flight ranging circuit, wherein the time-of-flight ranging circuit comprises a charge injection circuit and a switch energy storage array consisting of a plurality of switch energy storage branches. Referring to fig. 4, the time-of-flight ranging method includes:

step S100, receiving pulse electric signals of preset periods, and converting the pulse electric signals of each period into corresponding time digital signals;

in this embodiment, in a measurement process, the laser emitter periodically emits laser, that is, the laser emitter sequentially emits M emission pulses according to a predetermined emission period, where the emission period may be adjusted according to measurement accuracy, and M is an integer greater than 1. The laser receiver, namely the photoelectric sensor receives N reflected photons in a measurement process, N is an integer larger than 1, the photoelectric sensor converts the reflected photons into corresponding pulse electric signals, the time-to-digital converter can measure the arrival time of the pulse electric signals, the flight time of the reflected photons is determined according to the arrival time of the pulse signals, and the corresponding time-to-digital signals are converted.

Step 200, controlling the charge injection circuit to output electric energy with a preset charge amount when receiving one time digital signal;

and controlling the charge injection circuit to work according to the acquired flight time information corresponding to the N reflected photons, and controlling the charge injection circuit to start to work once when receiving a time digital signal, and outputting electric energy with fixed electric charge quantity.

And step S300, controlling the corresponding switch energy storage branch in the switch energy storage array to work according to the time digital signal of each period so as to store the electric energy output by the charge injection circuit and form a photon information histogram.

In this embodiment, the switch energy storage array includes a switch array formed by a plurality of electronic switches and a plurality of energy storage devices to form an energy storage array, when a corresponding electronic switch branch in the switch energy storage array is turned on, the capacitor starts to store the electric quantity of the fixed electric quantity injected by the electric charge injection circuit, the on time of the electronic switch can be the time when the fixed electric quantity injected by the electric charge injection circuit is finished, and after that, the electronic switch is turned off, because the capacitor has no discharging circuit, the electric charges can be stored in the capacitor, in each period, the electronic switch in the switch energy storage array is turned on every time, the turned-on capacitor stores the electric quantity once, so that the electric quantity stored by the capacitor injected with the fixed electric quantity can be accumulated. For example, in the first period, when a photon is received at the kth time, the kth electronic switch Sk is turned on at the kth time, so that the unit charge injection circuit injects a fixed charge quantity Qu into the capacitor Ck, and charges the capacitor Ck corresponding to the kth electronic switch Sk, so that the voltage value UCk across the capacitor Ck increases Qu/C. And sequentially carrying out, namely, turning on an electronic switch corresponding to each photon at the corresponding moment when each photon is received, until one period is ended, entering the next period, repeating the cycle, and repeating the preset period to finish the storage of the charge quantity corresponding to each flight time of all the periods. After the one-time measurement process is finished, the electric quantity stored by each capacitor is different in height due to different opening times of the switch branch, the voltages at two ends of the capacitor are different according to the different electric quantities stored by the capacitor, and the histogram peak searching circuit can obtain the flight time corresponding to photons by acquiring the capacitor with the highest voltage, so that the distance of the measured object can be determined according to the flight time. The time-of-flight ranging circuit can receive photons reflected by the measured object, namely reflected photons, and measure the photon time of flight of the photons by utilizing each laser emission. All photon flight times received in a plurality of periods are counted to obtain a histogram. Thus, a histogram peak is obtained according to the flight time information corresponding to the N reflected photons, and the distance of the measured object is obtained according to the histogram peak.

The foregoing description is only of the optional embodiments of the present application, and is not intended to limit the scope of the patent application, and all equivalent structural changes made by the specification and drawings of the present application or direct/indirect application in other related technical fields are included in the scope of the patent protection of the present application.

Claims (10)

1. A time-of-flight ranging circuit, the time-of-flight ranging circuit comprising:

the time-to-digital converter is used for receiving pulse electric signals of preset periods and converting the pulse electric signals of each period into corresponding time-to-digital signals;

the histogram circuit is connected with the time-to-digital converter and comprises an energy storage array, and the histogram circuit is used for storing preset unit electric energy to corresponding energy storage devices in the energy storage array according to the received time-to-digital signal so as to enable the corresponding energy storage devices in the energy storage devices to accumulate the electric energy and form a photon information histogram.

2. The time-of-flight ranging circuit of claim 1, wherein the histogram circuit further comprises:

the charge injection circuit is connected with the time-to-digital converter, and is used for starting working when receiving the time-to-digital signal and outputting electric energy with preset charge quantity;

a switch array connected to the time-to-digital converter; the switch array is used for switching on a corresponding switch branch according to the time digital signal of each period so as to control an energy storage device connected with the switch branch to store the electric energy output by the charge injection circuit and accumulate the electric energy output by the charge injection circuit to form a photon information histogram.

3. The time-of-flight ranging circuit of claim 2, wherein the switch array comprises:

the control end of each switch branch is connected with the time-to-digital converter, the input end of each switch branch is connected with the output end of the charge injection circuit, and the output end of each switch branch is connected with a corresponding energy storage device in the energy storage array.

4. A time-of-flight ranging circuit as claimed in claim 3, wherein each of the switch branches comprises an electronic switch, the controlled end of the electronic switch being the controlled end of the switch energy storage branch, the input end of the electronic switch being the input end of the switch energy storage branch, the output end of the electronic switch being connected to the first end of the energy storage device, the second end of the energy storage device being grounded.

5. The time-of-flight ranging circuit of any of claims 2-4, further comprising:

the processor is connected in series between the time-digital converter and the switch array, and is used for controlling the conduction of a corresponding switch branch in the switch array according to the received time-digital signal so as to control a corresponding storage device to store the electric energy output by the charge injection circuit.

6. The time-of-flight ranging circuit of any of claims 1-4, further comprising:

the photoelectric sensor is connected with the time-to-digital converter, and is used for receiving photons reflected by the measured object and generating corresponding pulse electric signals according to the received photon signals.

7. The time-of-flight ranging circuit of any of claims 1-4, further comprising:

the histogram peak searching circuit is electrically connected with the energy storage array, and is used for searching the peak position in the photon information histogram according to the electric energy stored by each energy storage device in the energy storage array and determining the flight time of the photon signal according to the peak position.

8. The time-of-flight ranging circuit of any of claims 1-4, further comprising:

and the laser emitter is used for sending laser photons with preset periods to the measured object.

9. A distance measurement system, characterized by a time-of-flight ranging circuit as claimed in any one of claims 1 to 8.

10. A time-of-flight ranging method using the time-of-flight ranging circuit of any one of claims 1 to 8, the time-of-flight ranging circuit comprising a charge injection circuit and a switched energy storage array comprised of a plurality of switched energy storage branches, the time-of-flight ranging method comprising:

receiving pulse electric signals of preset periods, and converting the pulse electric signals of each period into corresponding time digital signals;

controlling the charge injection circuit to output electric energy with a preset charge amount when receiving the time digital signal; the method comprises the steps of,

and controlling the corresponding switch energy storage branch circuit in the switch energy storage array to work according to the time digital signal of each period so as to store the electric energy output by the charge injection circuit and form a photon information histogram.