Distance measuring device

Abstract

The present application discloses a distance measuring apparatus, comprising: a detector array comprising a plurality of detector elements, each detector element for responding to photons and generating a detection signal; the logic circuit is respectively connected with the plurality of detector elements and is used for generating a trigger signal according to the detection signal; the time-to-digital conversion unit is used for generating a first counting signal with a timestamp according to the trigger signal; the accumulator is connected with each detector element in the detector array and is used for determining the number of the detection signals output by the detector array within the preset time and outputting a second counting signal with a timestamp; and the signal processing unit is used for acquiring a second counting signal according to the first counting signal and generating a statistical histogram according to the second counting signal to determine the distance to be measured. The counting of all response photons can be accurately recorded to improve the total number of photon events and the number of effective signals in histogram statistics, and the signal-to-noise ratio and the ranging accuracy are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of distance measurement, in particular to a distance measurement device. Background Art

[0002] Direct time of flight (dToF) technology is a distance measurement technology based on the principle of photon flight time measurement. The dToF distance measurement module includes at least a laser, a detector and a time digital converter (TDC). Its distance measurement principle is: the laser emits a laser pulse to illuminate the target to be measured, which is reflected by the target and sensed by the detector. The time digital converter records the time of transmitting and receiving light pulses to determine the flight time of the photon, and then determines the flight time t of the photon with the highest frequency through statistical methods, and then obtains the distance of the object s = c*t / 2, where c is the speed of light.

[0003] In some applications, the detector used in the dToF ranging module is a photodetector array including multiple single-photon detectors, such as a SPAD array including multiple SPAD pixels. Each single-photon detector is connected to a TDC, which is used to obtain the flight time of the corresponding photon on the single-photon detector and to count the corresponding photons with a counter. In this way, the SPAD array requires multiple TDCs, but the more TDCs there are, the more power is consumed. A large number of TDCs may also generate a relatively large amount of data, which has a high data rate requirement for the input / output bandwidth of the entire ranging device.

[0004] In order to reduce power consumption and cost, the prior art connects the SPAD array to a TDC through a combinational logic circuit, so that multiple SPAD pixels share a TDC through the OR gate logic of the combinational logic circuit. As long as one SPAD pixel is triggered by a photon to generate a pulse signal, the OR gate will output a high level to trigger the TDC to record the flight time and cooperate with the counter to count by 1 in the corresponding time bin. The photon flight time statistical histogram (referred to as the statistical histogram) is obtained by counting the flight time of a large number of photons. However, since the OR gate logic of the combinational logic circuit can only indicate whether a pulse signal is generated in the SPAD array by outputting "1" or "0", and cannot reflect the number of SPAD pixels triggered in the SPAD array at the same time, it cannot reflect the number of pulse signals output in the SPAD array at the same time, resulting in fewer times of obtaining valid signals in the statistical results of multiple measurements, and a lower signal-to-noise ratio. Summary of the invention

[0005] In view of the above problems, the purpose of the utility model is to provide a distance measuring device that can accurately record the counts of all response photons to increase the total number of photon events and the number of effective signals in the histogram statistics, thereby improving the signal-to-noise ratio and the accuracy of distance measurement.

[0006] According to a first aspect of the utility model, a distance measuring device is provided, comprising: a detector array, comprising a plurality of detector elements, each detector element being used to respond to photons and generate a detection signal; a logic circuit, respectively connected to the plurality of detector elements, and used to generate a trigger signal according to the detection signal; a time-to-number conversion unit, connected to the output end of the logic circuit, and used to generate a first counting signal with a timestamp according to the trigger signal; an accumulator, connected to each detector element in the detector array, and used to determine the number of detection signals output by the detector array within a preset time, and output a second counting signal with a timestamp; a signal processing unit, connected to the output end of the time-to-number conversion unit and the output end of the accumulator, and the signal processing unit is used to obtain the second counting signal according to the first counting signal, and generate a statistical histogram according to the second counting signal to determine the distance to be measured.

[0007] Preferably, the logic circuit is a multi-input OR gate circuit, the input ends of the logic circuit are respectively connected to the output ends of a plurality of detector elements to receive detection signals, and the output end of the logic circuit is connected to the time-to-digital conversion unit.

[0008] Preferably, the timestamp refers to the flight time information of the photon related to the trigger signal and / or the detection signal; wherein the flight time information of the photon is acquired by the time-to-digital conversion unit.

[0009] Preferably, the first counting signal refers to a counting signal whose counting value generated by the time-to-number conversion unit is equal to 1 when the logic circuit outputs a trigger signal.

[0010] Preferably, the number of detection signals output by the detector array within a preset time refers to the sum of the numbers of detection signals output by each detector element in the detector array within the preset time.

[0011] Preferably, the second counting signal refers to a counting signal equal to the number of detection signals output by the detector array within a preset time.

[0012] Preferably, the duration of the preset time is greater than or equal to zero and less than or equal to a preset threshold.

[0013] Preferably, the statistical histogram includes a plurality of time bins with time widths, and the height of the time bins is determined according to the timestamps falling within the time bins and the values ​​of the second counting signals corresponding to the timestamps.

[0014] Beneficial Effects

[0015] According to the distance measuring device of the utility model, the present application sets a logic circuit to be connected to multiple detection elements of the detector array respectively, so that the multiple detector elements can share a time conversion unit through the logic circuit, thereby reducing energy consumption and saving storage space; moreover, when a detection signal is output in the detector array, the logic circuit outputs a trigger signal according to the detection signal, and the time conversion unit generates a first counting signal with a timestamp according to the trigger signal. At the same time, the accumulator obtains the number of detection signals output by the detector array within a preset time and outputs a second counting signal with a timestamp. The signal processing unit can judge whether there is a photon sensing event in the detector array at the current moment according to the first counting signal, and then obtain the second counting signal to determine the number of detection signals output in the detector array, and generate a statistical histogram according to the second counting signal, so that the counts of all response photons on the detector array during the ranging process can be accurately recorded to increase the total number of photon events and the number of valid signals in the histogram statistics, and improve the signal-to-noise ratio and the accuracy of ranging. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other purposes, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0017] Figure 1 The schematic diagram of the structure of the distance measuring device provided by the utility model is shown. DETAILED DESCRIPTION

[0018] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0019] The specific implementation of the utility model is further described in detail below in conjunction with the drawings and embodiments.

[0020] In the prior art, the SPAD array of the dToF ranging module shares the same TDC through the OR gate logic of the combinational logic circuit. The TDC records the emission time of the light pulse and the time when the SPAD pixel responds, thereby obtaining the photon flight time of the light pulse. At the same time, when a SPAD pixel in the SPAD array is triggered by a photon to generate a pulse signal, the OR gate will output a high level to trigger the TDC to cooperate with the counter to count by 1 in the corresponding time bin. However, since the OR gate logic of the combinational logic circuit can only indicate whether a pulse signal is generated in the SPAD array by outputting "1" or "0", and cannot reflect the number of SPAD pixels triggered in the SPAD array at the same time, it cannot reflect the number of pulse signals output from the SPAD array at the same time, resulting in fewer valid signals obtained in the statistical results of multiple measurements, and a lower signal-to-noise ratio.

[0021] Based on the above technical problems, this application provides the following technical solutions:

[0022] Figure 1 FIG. 2 is a schematic diagram showing the structure of the distance measuring device provided by the embodiment of the utility model. Figure 1 As shown, the distance measuring device includes a laser emitter 110 , a detector array 120 , a logic circuit 130 , a time conversion unit 140 , an accumulator 150 and a signal processing unit 160 .

[0023] The laser transmitter 110 transmits a laser pulse to the target to be measured, and the laser pulse reaches the detector array 120 after being reflected by the target to be measured; the detector array 120 includes a plurality of detector elements 121, each of which receives the laser pulse reflected by the target to be measured and generates a detection signal; the logic circuit 130 generates a trigger signal according to the detection signal; the time conversion unit 140 generates a first counting signal with a timestamp according to the trigger signal; the accumulator 150 is connected to each detector element 121 in the detector array 120, and is used to determine the number of detection signals output by the detector array 121 within a preset time, and output a second counting signal with a timestamp. The signal processing unit 160 is connected to the output end of the time conversion unit 140 and the output end of the accumulator 150, and the signal processing unit 160 is used to obtain the second counting signal according to the first counting signal, and generate a statistical histogram according to the second counting signal to determine the distance to be measured.

[0024] In the present application, when the time conversion unit 140 generates a first counting signal with a timestamp according to a trigger signal, the accumulator 150 obtains the number of detection signals output by the detector array 120 within a preset time and outputs a second counting signal with a timestamp. The signal processing unit 160 can determine whether there is a photon sensing event in the detector array 120 at the current moment according to the first counting signal, and then obtain the second counting signal to determine the number of detection signals output from the detector array 120, and generate a statistical histogram according to the second counting signal, so as to accurately record the counts of all response photons on the detector array during the ranging process, so as to improve the total number of photon events and the number of valid signals in the histogram statistics, and improve the signal-to-noise ratio and the accuracy of ranging.

[0025] The detector array 120 includes a plurality of detector elements 121 , each of which is used to respond to a photon and generate a detection signal.

[0026] In this embodiment, the detector array 120 is, for example, a SPAD array including a plurality of SPAD pixels. The detector element 121 is, for example, a SPAD pixel. The detector element 121 can respond to a single photon of a light pulse reflected back from the target to be detected and generate a detection signal Sd, where the detection signal Sd is, for example, a pulse signal. When at least one detector element 121 detects a photon, the SPAD array outputs at least one detection signal Sd.

[0027] The logic circuit 130 is respectively connected to a plurality of detector elements for generating a trigger signal according to the detection signal.

[0028] In this embodiment, the logic circuit 130 is a multi-input OR gate circuit, the input end of the logic circuit 130 is respectively connected to the output end of the plurality of detector elements 121 to receive the detection signal Sd output by the plurality of detector elements 11, and the output end of the logic circuit 130 is connected to the time-to-digital conversion unit 140. When the logic circuit 130 receives the detection signal Sd, it generates a trigger signal St. It should be noted that, since the logic circuit 130 is an OR gate circuit, as long as there is a detector element 121 in the detector array 120 that detects a photon and outputs a detection signal Sd, regardless of the number of the detection signals Sd, the logic circuit 130 will output a trigger signal St.

[0029] The time conversion unit 140 is connected to the output end of the logic circuit 130 and is used to generate a first counting signal with a time stamp according to the trigger signal.

[0030] In this embodiment, the timestamp refers to the flight time information of the photon associated with the trigger signal St or / and the detection signal Sd; wherein the flight time of the photon refers to the time difference from the emission of the light pulse to the induction by the detection element; the photon associated with the trigger signal St or / and the detection signal Sd refers to the photon that causes the detection element 121 to generate the detection signal Sd and then causes the logic circuit 130 to output the trigger signal St. The flight time information of the photon is obtained by the time conversion unit 140. Specifically, the laser transmitter 110 emits a laser pulse to the target to be measured, and the time conversion unit 140 records the emission time of the laser pulse. The laser pulse reaches the detector array 120 after being reflected by the target to be measured, and the time conversion unit 140 records the receiving time of the detector array 120 receiving the laser pulse (i.e., the photon of the detection element responding to the laser pulse). The time difference between the receiving time and the emission time is the photon flight time information of the laser pulse.

[0031] In this embodiment, the first counting signal refers to a counting signal whose counting value is equal to 1 generated by the time-to-number conversion unit 140 when the logic circuit 130 outputs the trigger signal St.

[0032] Specifically, when the logic circuit 130 outputs the trigger signal St, the time conversion unit 140 records the flight time information of the photon as a timestamp, and counts by 1 in the time bin corresponding to the flight time information, that is, generates a counting signal with a count value equal to 1, so the time conversion unit 140 outputs a counting signal with the photon flight time information and a count value equal to 1. In a traditional ToF ranging device, the signal processing unit counts by 1 in the time bin corresponding to the photon flight time according to the counting signal with the photon flight time information and a count value equal to 1 output by the time conversion unit, thereby generating a photon flight time statistical histogram. Because the count value of the counting signal output by the time conversion unit is always 1, it may not match the number of photons actually responded to by the detector array, so the traditional ToF ranging device will have a loss of effective signal, resulting in a reduced signal-to-noise ratio and reduced ranging accuracy.

[0033] In order to overcome the problem of reduced signal-to-noise ratio caused by effective signal loss in traditional ToF ranging devices, an accumulator 150 is added to the ToF ranging device of this embodiment. The accumulator 150 records the number of detection signals output from the detector array 120 in real time and outputs a related second counting signal. The signal processing unit accumulates and counts the number of detection signals actually output from the detector array 120 according to the second counting signal to generate a statistical histogram, thereby increasing the number of photon events and the number of effective signals, improving the signal-to-noise ratio, and further improving the ranging accuracy.

[0034] Specifically, the input end of the accumulator 150 is connected to each detector element 121 in the detector array 120, and the output end of the accumulator 150 is connected to the signal processing unit 160. The accumulator 150 is used to obtain the detection signal Sd output by each detector element 121, and accumulate the number of detection signals Sd output by the detector array 120, and output a second counting signal with a timestamp. The second counting signal refers to a counting signal equal to the number of detection signals output by the detector array within a preset time, and the value of the second counting signal is the number of detection signals Sd output by the detector array within the preset time.

[0035] In this embodiment, the laser emitter 110 emits a laser pulse which is reflected by the target to be measured to the detector array. The emission time of the laser pulse and the time when the detector array detects the photon can reflect the flight time information of the photon. When at least one detector element 121 in the detector array 120 detects a photon, a detection signal Sd is generated. When the logic circuit 130 receives the detection signal Sd, a trigger signal St is generated. The time conversion unit 140 obtains the flight time information of the detected photon and generates a count signal with a count value of 1. At the same time, the accumulator 150 obtains the detection signal Sd output by each detection element 121 in the detector array 120 within a preset time. The accumulator 150 accumulates the count every time it receives a detection signal Sd, so as to determine the number of detection signals output by the detector array 120 within the preset time.

[0036] In this embodiment, the number of detection signals output by the detector array 120 within the preset time refers to the sum of the number of detection signals output by each detector element in the detector array within the preset time. The time length of the preset time is greater than or equal to zero and less than or equal to the preset threshold. The preset time represents a time interval with a very small time interval or a certain time point. When there are two or more detector elements 121 in the detector array 120 that sense photons and output detection signals at the same time at a certain moment, then the preset time is the time point, that is, the time length of the preset time is equal to 0, and the accumulator 150 records the number of detection signals output at the moment when the detector array 120 detects photons. If the detector array 120 detects photons at different time points, and the time interval between detecting photons is less than or equal to the preset threshold, that is, the time length of the preset time is greater than zero and less than the preset threshold, the accumulator 150 will record the number of detection signals output within the preset time. It should be noted that the size of the preset threshold is related to the time resolution capability of the ToF ranging device, that is, it is related to the time width represented by the time bin in the statistical histogram. The smaller the width of the time bin, the smaller the preset threshold, and the preset threshold is less than or equal to the width of the time bin, so that the count value of a second counting signal can be accumulated in a time bin, avoiding the situation where the photon count within the preset time crosses the time bin, thereby causing the problem of ranging error.

[0037] The signal processing unit 160 is connected to the output end of the hour-to-number conversion unit 140 and the output end of the accumulator 150, and the signal processing unit 160 is used to obtain the second counting signal according to the first counting signal, and generate a statistical histogram according to the second counting signal to determine the distance to be measured.

[0038] In this embodiment, the statistical histogram includes a plurality of time bins with time widths, and the height of the time bins is determined according to the timestamps falling into the time bins and the values ​​of the second counting signals corresponding to the timestamps. The average value of the photon flight time is determined by finding the peak value in the histogram, and then the distance to be measured is calculated according to the speed of light.

[0039] According to the distance measuring device of the embodiment of the utility model, a logic circuit is set to be connected to the multiple detection elements of the detector array respectively, so that the multiple detector elements can share a time conversion unit through the logic circuit, thereby reducing energy consumption and saving storage space; moreover, when a detection signal is output in the detector array, the logic circuit outputs a trigger signal according to the detection signal, and the time conversion unit generates a first counting signal with a timestamp according to the trigger signal. At the same time, the accumulator obtains the number of detection signals output by the detector array within a preset time and outputs a second counting signal with a timestamp. The signal processing unit can judge whether there is a photon sensing event in the detector array at the current moment according to the first counting signal, and then obtain the second counting signal to determine the number of detection signals output from the detector array, and generate a statistical histogram according to the second counting signal, so that the counts of all response photons on the detector array during the ranging process can be accurately recorded to increase the total number of photon events and the number of valid signals in the histogram statistics, and improve the signal-to-noise ratio and the accuracy of ranging.

[0040] The embodiments of the present invention are described above, and these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modifications based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A distance measuring device, characterized in that: include: a detector array, comprising a plurality of detector elements, each detector element being configured to respond to a photon and generate a detection signal; A logic circuit is connected to the plurality of detector elements respectively and is used to generate a trigger signal according to the detection signal; A time conversion unit, connected to the output end of the logic circuit, and used to generate a first counting signal with a time stamp according to the trigger signal; an accumulator, connected to each detector element in the detector array, for determining the number of detection signals output by the detector array within a preset time, and outputting a second counting signal with a timestamp; A signal processing unit is connected to the output end of the time-to-number conversion unit and the output end of the accumulator, and the signal processing unit is used to obtain the second counting signal according to the first counting signal, and generate a statistical histogram according to the second counting signal to determine the distance to be measured.

2. The distance measuring device according to claim 1, characterized in that: The logic circuit is a multi-input OR gate circuit, the input ends of the logic circuit are respectively connected to the output ends of a plurality of detector elements to receive detection signals, and the output end of the logic circuit is connected to the time-to-digital conversion unit.

3. The distance measuring device according to claim 1, characterized in that: The timestamp refers to the flight time information of the photon related to the trigger signal and / or the detection signal; wherein the flight time information of the photon is acquired by the time-to-digital conversion unit.

4. The distance measuring device according to claim 1, characterized in that: The first counting signal refers to a counting signal whose counting value is equal to 1 and which is generated by the time-to-number conversion unit when the logic circuit outputs a trigger signal.

5. The distance measuring device according to claim 1, characterized in that: The number of detection signals output by the detector array within a preset time refers to the sum of the number of detection signals output by each detector element in the detector array within the preset time.

6. The distance measuring device according to claim 5, characterized in that: The second counting signal refers to a counting signal whose counting value is equal to the number of detection signals output by the detector array within a preset time.

7. The distance measuring device according to claim 1, 5 or 6, characterized in that: The duration of the preset time is greater than or equal to zero and less than or equal to a preset threshold.

8. The distance measuring device according to claim 1, characterized in that: The statistical histogram includes a plurality of time bins with time widths, and the height of the time bins is determined according to the timestamps falling within the time bins and the values ​​of the second counting signals corresponding to the timestamps.

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