Distance measurement method, distance measurement circuit and electronic equipment

Abstract

The invention discloses a distance measurement method, a distance measurement circuit and electronic equipment. The distance measurement method comprises the following steps: taking an optical pulse transmission signal in at least one measurement period as a reference pulse signal; determining a to-be-segmented phase section corresponding to the reference pulse signal in each measurement period, dividing each to-be-segmented phase section into a plurality of phase sections, and comparing the charge quantity corresponding to the reference pulse signal in each phase section to obtain a charge comparison result; determining the measurement precision of the measurement equipment according to the number of the measurement periods of the reference pulse signal, the number of phase segments in the to-be-segmented phase segments and the maximum measurement distance of the measurement equipment; and obtaining the distance to be measured based on the charge comparison result and the measurement precision corresponding to the at least one measurement period. According to the technical scheme, by changing the number of the measurement periods and the number of the phase segments in the to-be-segmented phase segments, the measurement precision can be improved, and the problem that the maximum measurement distance and the demodulation contrast ratio are reduced while the measurement precision is improved is solved.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a distance measurement method, a distance measurement circuit and an electronic device. Background Art

[0002] iTOF (indirect time of flight) 3D cameras have become a 3D distance measurement technology with development potential in short distances due to their low computing power consumption, high spatial resolution and relatively mature technical reserves. Improving the distance measurement accuracy has been a long-standing challenge for iTOF.

[0003] In the existing technology, if you want to improve the measurement accuracy, you can start from the four aspects of pixel area utilization (Fill Factor, FF), quantum efficiency (QE), demodulation contrast (Demodulation contrast, DC), and modulation frequency (f). Among them, the improvement of FF, QE, and DC is close to the limit. If you want to significantly improve the measurement accuracy, you need to increase the modulation frequency. According to the following formula:

[0004] Maximum measurement distance Max Range = c / 2f; measurement accuracy σ = k*c / DC*f; where f is the modulation frequency, c is the speed of light, and k is a constant; it can be seen that the measurement accuracy is inversely proportional to the modulation frequency. If the modulation frequency is increased by 10 times, the measurement accuracy can also be increased by 10 times under the premise that other conditions remain unchanged; however, the modulation frequency is inversely proportional to the maximum measurement distance. If the modulation frequency is increased by 10 times, under the premise that other conditions remain unchanged, the measurement distance decreases to 0.1 times the original.

[0005] Therefore, the method of improving measurement accuracy by modulating frequency cannot take into account both measurement distance and measurement accuracy. When the measurement accuracy is improved by increasing the modulation frequency, the maximum measurement distance will be reduced. Summary of the invention

[0006] The technical problem solved by the present invention is that the maximum measuring distance can be reduced while the measuring accuracy is improved.

[0007] To solve the above technical problems, an embodiment of the present invention provides a distance measurement method, including: taking a light pulse emission signal in at least one measurement cycle as a reference pulse signal; determining a phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, dividing each phase segment to be divided into multiple phase segments, and comparing the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result; determining the measurement accuracy of the measuring device according to the number of measurement cycles of the reference pulse signal, the number of phase segments in each phase segment to be divided, and the maximum measurement distance of the measuring device; and obtaining the distance to be measured based on the charge comparison result and measurement accuracy corresponding to at least one measurement cycle.

[0008] Optionally, determine the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, divide each phase segment to be divided into multiple phase segments, and compare the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result, including: taking the phase segment of the first measurement cycle as the first phase segment to be divided; dividing the first phase segment to be divided into multiple phase segments, and comparing the charge amount corresponding to the reference pulse signal in each phase segment to obtain a first charge comparison result; based on the first charge comparison result, determine the second phase segment to be divided corresponding to the second measurement cycle; divide the second phase segment to be divided into phase segments and compare the charge amount of the reference pulse signal in the corresponding phase segment; repeat the following for the measurement cycle after the second measurement cycle: determine the phase segment to be divided in the next measurement cycle based on the charge comparison result of the previous phase segment to be divided, divide the phase segment to be divided into phase segments, and compare the charge amount of the reference pulse signal in the corresponding phase segment, until the charge comparison results corresponding to all measurement cycles are obtained.

[0009] Optionally, the first phase segment to be divided is divided into multiple phase segments, and the charge amounts corresponding to the reference pulse signals in each phase segment are compared to obtain a first charge comparison result, including: dividing the first phase segment to be divided into a first phase segment and a second phase segment; determining a first charge amount corresponding to the internal reference pulse signal of the first phase segment and a second charge amount corresponding to the internal reference pulse signal of the second phase segment; comparing the first charge amount and the second charge amount to obtain a first charge comparison result.

[0010] Optionally, based on the first charge comparison result, the second phase segment to be divided corresponding to the second measurement cycle is determined, including: when the first charge amount is greater than the second charge amount, the first phase segment is used as the second phase segment to be divided; when the first charge amount is less than the second charge amount, the second phase segment is used as the second phase segment to be divided.

[0011] Optionally, the second phase segment to be divided is divided into phase segments, including: based on the first charge comparison result, determining the measurement phase corresponding to the second phase segment to be divided, the measurement phase being the phase point connecting two consecutive phase segments; according to the measurement phase and the second phase segment to be divided, dividing the second phase segment to be divided into multiple phase segments on average.

[0012] Optionally, determining the measurement phase corresponding to the second phase segment to be divided based on the first charge comparison result includes: determining the measurement phase corresponding to the second phase segment to be divided as t based on the first charge comparison result. 1 ±T / 4, where t 1 is the measurement phase corresponding to the first measurement cycle, T is the measurement cycle, t 1 The measured phase is always T / 2.

[0013] Optionally, based on the first charge comparison result, the measurement phase corresponding to the second phase segment to be divided is determined to be t 1 ±T / 4, including: when the first charge amount is greater than the second charge amount, determining that the measured phase corresponding to the second phase segment to be divided is t 1 -T / 4; when the first charge amount is less than or equal to the second charge amount, determine that the measured phase corresponding to the second phase segment to be divided is t 1 +T / 4.

[0014] Optionally, the first charge amount and the second charge amount are compared to obtain a first charge comparison result, including: when the first charge amount is greater than the second charge amount, obtaining a first charge comparison result "0"; when the first charge amount is greater than or equal to the second charge amount, obtaining a first charge comparison result "1".

[0015] Optionally, the measurement cycles after the second measurement cycle are repeated: determining the phase segment to be divided in the next measurement cycle based on the charge comparison result in the previous phase segment to be divided, dividing the phase segment to be divided into phase segments, and comparing the charge amounts of the reference pulse signals in the corresponding phase segments until the charge comparison results corresponding to all measurement cycles are obtained, including: determining the measurement phase corresponding to the next phase segment to be divided as t based on the charge comparison result in the previous phase segment to be divided N-1 ±T / X N , where N is the sequence number of the next measurement cycle in multiple measurement cycles, and N ≥ 2, t N-1 is the measurement phase corresponding to the previous measurement cycle, T is the measurement cycle, X is the number of phase segments in a measurement cycle, t 1 The measured phase is always T / X.

[0016] Optionally, before obtaining the distance to be measured based on the charge comparison result and measurement accuracy corresponding to at least one measurement cycle, the distance measurement method also includes: determining a charge difference based on the charge comparison result, wherein the charge difference is characterized by the absolute value of the difference between the charge amounts corresponding to the reference pulse signals in each phase segment; and determining whether to stop measuring the comparison result based on the charge comparison result and / or the charge difference.

[0017] Optionally, determining whether to stop measuring the comparison result is based on the charge comparison result and / or the charge difference, including: when the charge comparison results corresponding to all measurement cycles are obtained, or the charge difference in any measurement cycle is less than a preset threshold, determining to stop measuring the comparison result.

[0018] Optionally, after obtaining the charge comparison results corresponding to all measurement cycles, or the charge difference in any measurement cycle is less than a preset threshold value, and it is determined to stop measuring the comparison results, the method includes: obtaining the charge comparison result of at least one measurement cycle; converting the sum of the charge comparison results of multiple measurement cycles into a sum of decimal values; and obtaining the distance to be measured based on the sum of the decimal values ​​and the measurement accuracy.

[0019] An embodiment of the present invention also provides a distance measurement circuit, including: a cycle selection module, used to use the light pulse emission signal in at least one measurement cycle as a reference pulse signal; a comparison module, used to determine the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, divide each phase segment to be divided into multiple phase segments, and compare the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result; a measurement accuracy determination module, used to determine the measurement accuracy of the measuring device according to the number of measurement cycles of the reference pulse signal, the number of phase segments in each phase segment to be divided, and the maximum measurement distance of the measuring device; a distance determination module to be measured, used to obtain the distance to be measured based on the charge comparison result and measurement accuracy corresponding to at least one measurement cycle.

[0020] Optionally, the comparison module includes several storage units, photodiodes and a differential amplifier, and the period selection module includes an output end; the positive electrode of the photodiode is connected to the output end of the period selection module, and the negative electrode of the photodiode is suitable for converting the reference pulse signal into electric charge, and outputting the electric charge to the input ends of several storage units; the input ends of several storage units are also connected to the output end of the differential amplifier, and the output ends of several storage units are connected to the first input end and the second input end of the differential amplifier; the output end of the differential amplifier is also connected to the input end of the measurement accuracy determination module.

[0021] Optionally, several storage units include several transfer NMOS tubes, several capacitor units and floating gate nodes; in one storage unit, the gate of the transfer NMOS tube is connected to the output end of the differential amplifier, the drain of the transfer MOS tube is connected to the cathode of the photodiode, the source of the transfer NMOS tube is connected to the floating gate node and the first end of the capacitor unit, and the second end of the capacitor unit is grounded.

[0022] An embodiment of the present invention further provides an electronic device, comprising the above distance measurement circuit.

[0023] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0024] The technical solution of the present invention selects at least one measurement cycle, determines the phase segment to be divided in each measurement cycle, and divides the phase segment to be divided into multiple phase segments on average, and finally obtains the measurement accuracy based on the number of measurement cycles, the number of phase segments in each phase segment to be divided and the maximum measurement distance. It can be seen that the present invention only needs to change the number of measurement cycles and the number of phase segments in each phase segment to be divided to improve the measurement accuracy, avoiding the problem in the prior art that while improving the measurement accuracy, it will lead to a reduction in the maximum measurement distance and demodulation contrast, and can flexibly obtain the number of measurement cycles, thereby adjusting the measurement accuracy.

[0025] Furthermore, in an embodiment of the present invention, within any phase segment to be divided, the measurement is stopped when the difference between the charge amounts corresponding to the reference pulse signals in each phase segment is less than a preset threshold. At this time, the phase error of the corresponding measurement phase in the phase segment to be divided is controllable, thereby achieving improved accuracy of the distance to be measured.

[0026] Furthermore, the embodiment of the present invention stops measuring after obtaining the charge comparison results corresponding to all measurement cycles, thereby avoiding the existing method of stopping the measurement only after measuring all light pulse emission signals, and improving the flexibility of the measurement.

[0027] Furthermore, the distance determination module in the distance measurement circuit provided in the embodiment of the present invention can directly calculate the distance to be measured in a digital manner, without the need for digital-to-analog conversion and then calculating the distance to be measured, thereby avoiding the introduction of system errors and ensuring the measurement accuracy of the distance to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a working waveform of a distance measurement circuit. Figure 1 ;

[0029] Figure 2 It is a working waveform of a distance measurement circuit. Figure 2 ;

[0030] Figure 3 This is a schematic diagram of the structure of a distance measurement circuit. Figure 1 ;

[0031] Figure 4 This is a schematic diagram of the structure of a distance measurement circuit. Figure 2 ;

[0032] Figure 5 is a flow chart of a distance measurement method in one embodiment of the present invention;

[0033] Figure 6 is a working waveform diagram of a distance measurement circuit in one embodiment of the present invention;

[0034] Figure 7FIG. 1 is a schematic diagram of a distance measurement circuit according to an embodiment of the present invention. Figure 1 ;

[0035] Figure 8 FIG. 1 is a schematic diagram of a distance measurement circuit according to an embodiment of the present invention. Figure 2 . DETAILED DESCRIPTION

[0036] From the background technology, we can know that while improving the distance measurement accuracy, the maximum measurement distance will be reduced. Now, we analyze the reasons in combination with the performance characteristics of the existing distance measurement circuit:

[0037] Figure 1 It is a working waveform of a distance measurement circuit. Figure 1 .

[0038] Please refer to Figure 1 , Figure 1 The light source in the image is an infrared laser light source, which, under the action of the drive, emits a continuous wave of a specific frequency (f) with modulated amplitude to illuminate the entire scene.

[0039] The following is an explanation of the principle of calculating the distance of the object to be measured by iTOF flight time.

[0040] The emitted light signal is reflected by the objects in the scene and received by the iTOF sensor after a period of time. The sensor calculates the phase difference Δφ between the emission and reception of the signal, and calculates the time difference between the signal transmission and reception through the phase difference Δφ, and then calculates the distance of the object to be measured Depth = c / 2f*φ / 2π through the time difference.

[0041] From the background technology, we know that if we want to improve the measurement accuracy, we can start from the four aspects of pixel area utilization (Fill Factor, FF), quantum efficiency (QE), demodulation contrast (Demodulation contrast, DC), and modulation frequency (f). Among them, the improvement of FF, QE, and DC is close to the limit. If we want to significantly improve the measurement accuracy, we need to increase the modulation frequency.

[0042] Figure 2 It is a working waveform of a distance measurement circuit. Figure 2 .

[0043] Please refer to Figure 2 , Figure 2 The two working waveforms are respectively the working waveforms at high frequency and low frequency. It can be seen from the figure that under the same phase difference Δφ, the measured distance Δd at high frequency 1 Smaller than the measured distance Δd at low frequencies 2 ,Therefore, the method of improving the ranging accuracy by increasing the ,frequency will lead to a decrease in the measured distance.

[0044] Figure 3 This is a schematic diagram of the structure of a distance measurement circuit. Figure 1 .

[0045] Please refer to Figure 3 , Figure 3 The circuit for collecting, transferring and storing charges in a modulation period taking a pixel as an example includes: a photodiode, a first switch tube NM1, a second switch tube NM2, a first storage node MN1 and a second storage node MN2.

[0046] The working process of the existing distance measurement circuit is described below.

[0047] After the photodiode collects the charges, the first switch tube NM1 is controlled to be turned on within the modulation period (0, π), and the second switch tube NM2 is controlled to be turned off within the modulation period (0, π), thereby storing the charges collected within the first half of the period (0, π) in MN1; the first switch tube NM1 is controlled to be turned on within the modulation period (π, 2π), and the second switch tube NM2 is controlled to be turned off within the modulation period (π, 2π), thereby storing the charges collected within the second half of the period (π, 2π) in MN2.

[0048] In addition, the increase in modulation frequency will also lead to a decrease in demodulation contrast DC, which offsets the improvement in measurement accuracy. Demodulation contrast DC can be understood as the transmission success rate of the signal from the photodiode to the storage node. Higher modulation frequencies will have higher requirements on the transmission speed of electrons in iTOF pixels.

[0049] Please continue to refer to Figure 3 Since the collected charges need to be transferred and stored in different MNs according to the time they are collected, if the modulation frequency increases and the charge transfer speed cannot keep up, the collected charges will not be stored immediately but will be stored in the wrong MN, resulting in a decrease in the demodulation contrast DC.

[0050] Figure 4 This is a schematic diagram of the structure of a distance measurement circuit. Figure 2 .

[0051] Below Figure 4 The working process of the distance measurement circuit shown is explained.

[0052] Please refer to Figure 4 The optical signal is converted into electric charge through the photoelectric conversion module and stored in several storage nodes. The floating gate amplifier converts the electric charge into a voltage signal. The voltage signal is recorded as V1, V2, V3, and V4 after analog-to-digital conversion. The phase difference Δφ and the voltage have the following relationship: Δφ=arctan(V1-V2) / (V3-V4).

[0053] It can be seen that the above measurement circuit needs to convert the analog signal into a digital signal before calculating the phase. Multiple calculations lead to the introduction of additional system errors, which in turn affects the measurement accuracy.

[0054] In order to make the above-mentioned objects, features and beneficial effects of the present invention more clearly understood, the following Figures 5 to 8 The specific embodiments of the present invention are described in detail.

[0055] refer to Figure 5 , Figure 5 It is a flow chart of a distance measurement method in one embodiment of the present invention.

[0056] The distance measurement method of the embodiment of the present invention includes:

[0057] S1: Using the optical pulse emission signal in at least one measurement cycle as a reference pulse signal.

[0058] In this embodiment, the optical pulse emission signal includes an infrared laser light source and visible light; the number of measurement cycles is equal to the number of optical pulse emission signals.

[0059] It should be noted that the duty cycle of the optical pulse transmission signal of this embodiment includes any value less than 25%, and the waveform of the optical pulse transmission signal includes a square wave, a triangle wave, a trapezoidal wave or a sine wave.

[0060] In other embodiments, the optical pulse emission signal has a modulation frequency, and the modulation frequency f ranges from 10 MHz to 100 MHz.

[0061] S2: Determine the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, divide each phase segment to be divided into multiple phase segments, and compare the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result.

[0062] In some embodiments, each phase segment to be divided is divided into X phase segments, and the X phase segments include: a first phase segment to an Xth phase segment, and the latter phase segment is a continuous phase segment later than the former phase segment.

[0063] The following is a detailed description of step S2, which determines the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, divides each phase segment to be divided into a plurality of phase segments, and compares the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result, including:

[0064] S21: taking the phase segment of the first measurement cycle as the first phase segment to be divided.

[0065] S22: Divide the first phase segment to be divided into a plurality of phase segments, and compare the charge amounts corresponding to the reference pulse signals in each phase segment to obtain a first charge comparison result.

[0066] S23: Determine a second phase segment to be divided corresponding to a second measurement cycle based on the first charge comparison result.

[0067] S24: Divide the second phase segment to be divided into phase segments and compare the charge amounts of the reference pulse signals in the corresponding phase segments.

[0068] S25: Repeat the measurement cycle after the second measurement cycle: determine the phase segment to be divided in the next measurement cycle based on the charge comparison result of the previous phase segment to be divided, divide the phase segment to be divided into phase segments, and compare the charge amount of the reference pulse signal in the corresponding phase segment, until the charge comparison results corresponding to all measurement cycles are obtained.

[0069] In the above scheme, in the first measurement cycle, the length of the phase segment to be divided is the length of the first measurement cycle, and the measurement phase in the first measurement cycle is fixed to T / X, where X is the number of multiple phase segments in the phase segment to be divided; thereafter, the length of the phase segment to be divided and the measurement phase of the next measurement cycle are obtained by the charge comparison result in the previous measurement cycle.

[0070] In a specific embodiment, the phase segment of the first measurement cycle is taken as the first phase segment to be divided, which is characterized by the phase length of the first measurement cycle being equal to the phase length of the first phase segment to be divided.

[0071] The following takes dividing the first phase segment to be divided into two phase segments as an example to describe step S22 in detail. Step S22 includes:

[0072] S221: Divide the first phase segment to be divided into a first phase segment and a second phase segment.

[0073] S222: Determine a first charge amount corresponding to the internal reference pulse signal of the first phase segment and a second charge amount corresponding to the internal reference pulse signal of the second phase segment.

[0074] S223: Compare the first charge amount and the second charge amount to obtain a first charge comparison result.

[0075] In this embodiment, in step S23, determining the second phase segment to be divided corresponding to the second measurement cycle based on the first charge comparison result includes:

[0076] The phase length of the first phase segment is compared with the pulse width of the reference pulse signal: when the phase length of the first phase segment is not equal to the pulse width of the reference pulse signal, the second phase segment to be divided corresponding to the second measurement cycle is determined based on the first charge comparison result; when the phase length of the first phase segment is equal to the pulse width of the reference pulse signal, the phase length of the first phase segment to be divided is used as the phase length of the second phase segment to be divided.

[0077] In the above scheme, the purpose of comparing the phase length of the first phase segment with the pulse width of the reference pulse signal is to achieve that the phase length of the phase segment is equal to the pulse width of the reference pulse signal. When the phase length of the phase segment is equal to the pulse width of the reference pulse signal, the distance measurement method of the embodiment of the present invention does not change the frequency response accuracy of the system and does not cause noise.

[0078] In this embodiment, the first charge amount and the second charge amount are compared to obtain a first charge comparison result, including: when the first charge amount is greater than the second charge amount, a first charge comparison result of "0" is obtained; when the first charge amount is greater than or equal to the second charge amount, a first charge comparison result of "1" is obtained.

[0079] In this embodiment, in step S23, based on the first charge comparison result, the second phase segment to be divided corresponding to the second measurement cycle is determined, and it also includes: when the first charge amount is greater than the second charge amount, the first phase segment is used as the second phase segment to be divided; when the first charge amount is less than or equal to the second charge amount, the second phase segment is used as the second phase segment to be divided.

[0080] Among them, taking the first phase segment as the second phase segment to be divided means that the length of the first phase segment is equal to that of the second phase segment to be divided; taking the second phase segment as the second phase segment to be divided means that the second phase segment is equal to the second phase segment to be divided.

[0081] In the preferred embodiment, please refer to Figure 6 , the pulse width of the optical pulse emission signal is T / 4, where T is the length of the measurement cycle; in the first cycle, the length of the first phase segment is T / 2; in the second cycle, the length of each phase segment in the second phase segment to be divided is T / 4.

[0082] In one embodiment, the length of the phase segment and the pulse width of the reference pulse signal are both characterized as the phase.

[0083] The technical solution of the present invention does not limit the pulse width of the optical pulse emission signal and the phase segments in the second phase segment to be divided. The pulse width of the optical pulse emission signal and other lengths of the phase segments in the second phase segment to be divided are within the protection scope of the present invention. It should be noted that the pulse width of the optical pulse emission signal is less than the length T of the measurement period, and each phase segment in the second phase segment to be divided is less than or equal to T / 4.

[0084] In the above scheme, when the phase length of the phase segment is equal to the pulse width of the reference pulse signal, the distance measurement method of the embodiment of the present invention does not change the frequency response accuracy of the system and does not cause noise.

[0085] In other embodiments, when the first charge amount is equal to the second charge amount, the first phase segment is used as the second phase segment to be divided.

[0086] In this embodiment, the step S24 of dividing the second phase segment to be divided into phase segments includes:

[0087] S241: Based on the first charge comparison result, determine a measurement phase corresponding to a second phase segment to be divided, where the measurement phase is a phase point connected between two consecutive phase segments.

[0088] S242: Divide the second phase segment to be divided into a plurality of phase segments on an even basis according to the measured phase and the second phase segment to be divided.

[0089] In this embodiment, determining the measurement phase corresponding to the second phase segment to be divided based on the first charge comparison result in step S241 includes:

[0090] Based on the first charge comparison result, the measurement phase corresponding to the second phase segment to be divided is determined to be t 1 ±T / 4, where t 1 is the measurement phase corresponding to the first measurement cycle, T is the measurement cycle, t 1 The measured phase is always T / 2.

[0091] In a specific embodiment, determining the measurement phase corresponding to the second phase segment to be divided includes: when the first charge amount is greater than the second charge amount, determining the measurement phase corresponding to the second phase segment to be divided as t 1 -T / 4; when the first charge amount is less than or equal to the second charge amount, determine that the measured phase corresponding to the second phase segment to be divided is t 1 +T / 4.

[0092] In this embodiment, step S25: repeating the measurement cycles after the second measurement cycle: determining the phase segment to be divided in the next measurement cycle based on the charge comparison result of the previous phase segment to be divided, dividing the phase segment to be divided, and comparing the charge amount of the reference pulse signal in the corresponding phase segment, until the charge comparison results corresponding to all measurement cycles are obtained, including:

[0093] Based on the charge comparison result in the previous phase segment to be divided, the measurement phase corresponding to the next phase segment to be divided is determined to be t N-1 ±T / X N , where N is the sequence number of the next measurement cycle in multiple measurement cycles, and N ≥ 2, t N-1 is the measurement phase corresponding to the previous measurement cycle, T is the measurement cycle, X is the number of phase segments in a measurement cycle, t 1 The measured phase is always T / X.

[0094] Specifically, when the first charge amount is greater than the second charge amount, the measurement phase corresponding to the next measurement cycle is determined to be t N-1 -T / X N ; When the first charge amount is less than or equal to the second charge amount, the measurement phase corresponding to the next measurement cycle is determined to be t N-1 +T / X N .

[0095] Please continue to refer to Figure 5 Step S3 includes: determining the measurement accuracy of the measuring device according to the number of measurement cycles of the reference pulse signal, the number of phase segments in each phase segment to be divided, and the maximum measurement distance of the measuring device.

[0096] In this embodiment, the number of phase segments in each phase segment to be divided is X; the number of measurement cycles is M; thus, the formula for the measurement accuracy σ is represented by σ=Range / X M , Range is the maximum measurement distance.

[0097] In a specific embodiment, Range=c / 2f, where c is the speed of light and f is the modulation frequency.

[0098] Please continue to refer to Figure 5 , step S4: obtaining the distance to be measured based on the charge comparison result and the measurement accuracy corresponding to at least one measurement cycle.

[0099] In this embodiment, before step S4, the following steps are included:

[0100] S40: Determine a charge difference based on the charge comparison result, wherein the charge difference is characterized by an absolute value of a difference between charge amounts corresponding to reference pulse signals in each phase segment.

[0101] S41: Determine whether to stop measuring the comparison result according to the charge comparison result and / or the charge difference.

[0102] In this embodiment, step S41 includes: when the charge comparison results corresponding to all measurement cycles are obtained, or the charge difference in any measurement cycle is less than a preset threshold, determining to stop measuring the comparison results.

[0103] In a specific embodiment, the preset threshold is 5, but the present invention is not limited thereto, and other values ​​of the preset threshold are within the protection scope of the present invention.

[0104] After obtaining the charge comparison results corresponding to all measurement cycles, or the charge difference in any measurement cycle is less than a preset threshold, it is determined to stop measuring the comparison results, including:

[0105] S42: Obtaining a charge comparison result of at least one measurement cycle; converting a sum of the charge comparison results of multiple measurement cycles into a sum of decimal values;

[0106] S43: Based on the sum of the decimal values ​​and the measurement accuracy, the distance to be measured is obtained.

[0107] Let's take X=2 as an example. Figure 6 , the conceptual working process of the distance measurement method of this embodiment is explained.

[0108] It should be noted that the embodiments of the present invention do not limit the number of phase segments, and other numbers of phase segments are within the protection scope of the present invention.

[0109] When X=2, the multiple phase segments in the first phase to be divided include: a first phase segment and a second phase segment; in the first measurement cycle T1, the first charge amount in the first phase segment and the second charge amount in the second phase segment are compared to obtain a first charge comparison result, and based on the first charge comparison result, the measurement phase or the phase segment to be divided corresponding to the second measurement cycle T2 is determined.

[0110] In the second measurement cycle T2, the second phase segment to be divided is divided into phase segments, and the multiple phase segments in the second phase to be divided include: a third phase segment and a fourth phase segment. The third charge amount in the third phase segment and the second charge amount in the second phase segment are compared to obtain a second charge comparison result, and based on the second charge comparison result, the measurement phase or the phase segment to be divided corresponding to the third measurement cycle T3 is determined.

[0111] In the third measurement cycle T3, the third phase segment to be divided is divided into phase segments, and the multiple phase segments in the third phase to be divided include: a fifth phase segment and a sixth phase segment. The fifth charge amount in the fifth phase segment and the sixth charge amount in the sixth phase segment are compared to obtain a third charge comparison result, and based on the third charge comparison result, the measurement phase or the phase segment to be divided corresponding to the fourth measurement cycle T4 is determined.

[0112] In the fourth measurement cycle T4, the fourth phase segment to be divided is divided into phase segments, and the multiple phase segments in the fourth phase to be divided include: the seventh phase segment and the eighth phase segment. The seventh charge amount in the seventh phase segment and the eighth charge amount in the eighth phase segment are compared to obtain a fourth charge comparison result.

[0113] In the fourth measurement cycle T4, the seventh charge amount in the seventh phase segment is equal to the eighth charge amount in the eighth phase segment, that is, the charge difference is less than the preset threshold, so the measurement is stopped.

[0114] The sum of the first charge comparison result to the fourth charge comparison result is converted into a sum of decimal values; based on the sum of the decimal values ​​and the measurement accuracy, the distance to be measured is obtained.

[0115] The embodiment of the present invention divides the phase segment to be divided into two phase segments on average, and compares the charge amounts corresponding to the reference pulse signals in the two phase segments to obtain a charge comparison result. When the charge amounts corresponding to the reference pulse signals in the two phase segments are equal, the measurement is stopped. At this time, the difference between the measured phase corresponding to the phase segment to be divided and the middle pulse of the reference pulse signal is the phase difference corresponding to the distance to be measured. Therefore, the accuracy of the distance to be measured obtained based on the charge comparison result at this time is improved.

[0116] Figure 7 Schematic diagram of the distance measurement circuit in one embodiment of the present invention Figure 1 .

[0117] Please refer to Figure 7 , a distance measurement circuit, comprising:

[0118] A cycle selection module 1, used to use the optical pulse emission signal in at least one measurement cycle as a reference pulse signal;

[0119] Comparison module 2, used to determine the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, divide each phase segment to be divided into multiple phase segments, and compare the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result;

[0120] The measurement accuracy determination module 3 is used to determine the measurement accuracy of the measuring device according to the number of measurement cycles of the reference pulse signal, the number of phase segments in each phase segment to be divided, and the maximum measurement distance of the measuring device;

[0121] The distance-to-be-measured determining module 4 is used to obtain the distance to be measured based on the charge comparison result and the measurement accuracy corresponding to at least one measurement cycle.

[0122] Figure 8 FIG. 1 is a schematic diagram of a distance measurement circuit according to an embodiment of the present invention. Figure 2 .

[0123] Please refer to Figure 8 In some embodiments, the comparison module 2 includes a plurality of storage units 201, a photodiode D1 and a differential amplifier 202, and the cycle selection module 1 includes an output terminal.

[0124] The anode of the photodiode D1 is connected to the output end of the period selection module 1 , and the cathode of the photodiode D1 is suitable for converting the reference pulse signal into charges and outputting the charges to the input ends of the plurality of storage units 201 .

[0125] The input ends of the plurality of storage units 201 are also connected to the output end of the differential amplifier 202, and the output ends of the plurality of storage units 201 are connected to the first input end and the second input end of the differential amplifier 202;

[0126] The output terminal of the differential amplifier 202 is also connected to the input terminal of the measurement accuracy determination module 3 .

[0127] The plurality of storage units 201 include a plurality of transfer NMOS transistors NM, a plurality of capacitor units C and a floating gate node;

[0128] In a storage unit, the gate of the transfer NMOS tube NM is connected to the output end of the differential amplifier 202, the drain of the transfer MOS tube NM is connected to the cathode of the photodiode D1, the source of the transfer NMOS tube NM is connected to the floating gate node and the first end of the capacitor unit C, and the second end of the capacitor unit C is grounded.

[0129] In this embodiment, the transfer MOS transistor NM is an NMOS transistor, but the present invention is not limited thereto, and other types of MOS transistors are within the protection scope of the present invention.

[0130] In other embodiments, the comparison module further includes a phase control unit (not shown in the figure), and the phase control unit is suitable for controlling the length of the phase segment in each measurement cycle.

[0131] In one example, the phase control unit includes a delay phase-locked loop or a ring oscillator, and other circuits are within the protection scope of the present invention.

[0132] Specifically, the phase control unit can provide a delayed phase signal with a modulation frequency f that is 10 times or more than 10 times the modulation frequency f.

[0133] Let's take X=2 as an example. Figure 6 , Figure 8 The operation process of the distance measurement circuit of this embodiment is described.

[0134] Figure 6 is the working waveform of the distance measurement circuit in one embodiment of the present invention Figure 3 , that is, the waveform diagram when X=2, the shaded part in the figure represents the charge amount corresponding to the light pulse emission signal or the charge amount corresponding to the reference pulse signal.

[0135] Among them, when measuring the split phase segment, Figure 6 The X-axis in represents the phase length. When comparing the charge results, Figure 6 The X-axis represents the charge amount, and the Y-axis represents the signal strength.

[0136] In this embodiment, the pulse width of the optical pulse transmission signal is equal to the pulse width of the reception signal.

[0137] It should be noted that, in this embodiment, the duty cycle of the optical pulse emission signal is 25%, the waveform of the optical pulse emission signal is a square wave, the phase delay of the received signal is any value within [0, 2π], that is, the measurement period is [0, 2π], the plurality of transfer NMOS tubes include a first transfer NMOS tube and a second transfer NMOS tube, and the plurality of storage units include a first capacitor unit and a second capacitor unit.

[0138] The embodiment of the present invention does not limit the phase length of the measurement period, and other phase lengths of the measurement period are within the protection scope of the present invention.

[0139] In this embodiment, the condition for stopping the measurement is that the charge difference in any measurement cycle is less than a preset threshold.

[0140] The photodiode D1 is used to convert the pulse width of the reference pulse signal into electric charge.

[0141] In the first measurement cycle T1, the length of the phase segment to be divided is equal to the length of the first measurement cycle T1, and the phase segment to be divided is evenly divided into 2 phase segments, the first phase segment is [0,π], and the second phase segment is [π,2π].

[0142] In the first phase segment [0,π], a high level is applied to the gate of the first transfer NMOS transistor to turn on the first transfer NMOS transistor, thereby storing the first charge in the first phase segment [0,π] in the first capacitor unit.

[0143] In the second phase segment [π, 2π], a high level is applied to the gate of the second transfer NMOS transistor to turn on the second transfer NMOS transistor, thereby storing the second charge in the second phase segment [π, 2π] in the second capacitor unit.

[0144] The first charge amount is compared with the second charge amount through the differential amplifier 202. In the first measurement cycle, the first charge amount is greater than the second charge amount, that is, the comparison result output is 0.

[0145] Furthermore, the length of the first phase segment is not equal to the pulse width of the reference pulse signal, so in the second measurement cycle T2, the initial phase of the phase segment to be divided is the same as the initial phase of the first phase segment.

[0146] In the second measurement cycle T2, the phase segment to be divided is evenly divided into 2 phase segments, the third phase segment is [0,π / 2], and the fourth phase segment is [π / 2,π].

[0147] In the third phase segment [0,π / 2], a high level is applied to the gate of the first transfer NMOS transistor to turn on the first transfer NMOS transistor, thereby storing the third charge in the third phase segment [0,π / 2] in the first capacitor unit.

[0148] In the fourth phase segment [π / 2,π], a high level is applied to the gate of the second transfer NMOS transistor to turn on the second transfer NMOS transistor, thereby storing the fourth charge in the fourth phase segment [π / 2,π] in the second capacitor unit.

[0149] The third charge amount is compared with the fourth charge amount through the differential amplifier 202. In the second measurement cycle, the third charge amount is smaller than the fourth charge amount, that is, the comparison result output is 1.

[0150] The length of the third phase segment is equal to the pulse width of the reference pulse signal. Therefore, in the third measurement cycle T3, the measured phase is π / 2+2π / 2 3 , that is, the measured phase is 3π / 4.

[0151] In the third measurement cycle T3, the phase segment to be divided is evenly divided into 2 phase segments, the fifth phase segment is [π / 4, 3π / 4], and the sixth phase segment is [3π / 4, 5π / 4].

[0152] In the fifth phase segment [π / 4, 3π / 4], a high level is applied to the gate of the first transfer NMOS transistor to turn on the first transfer NMOS transistor, thereby storing the fifth charge in the fifth phase segment [π / 4, 3π / 4] in the first capacitor unit.

[0153] In the sixth phase segment [3π / 4, 5π / 4], a high level is applied to the gate of the second transfer NMOS transistor to turn on the second transfer NMOS transistor, thereby storing the sixth charge in the sixth phase segment [3π / 4, 5π / 4] in the second capacitor unit.

[0154] The fifth charge amount is compared with the sixth charge amount through the differential amplifier 202. In the third measurement cycle, the fifth charge amount is greater than the sixth charge amount, that is, the comparison result outputs 0. In the third measurement cycle T4, the measurement phase is 3π / 4-2π / 2 4 , that is, the measured phase is 5π / 8.

[0155] In the fourth measurement cycle T4, the phase segment to be divided is evenly divided into 2 phase segments, the seventh phase segment is [π / 8, 5π / 8], and the eighth phase segment is [5π / 8, 9π / 8].

[0156] In the seventh phase segment [π / 8, 5π / 8], a high level is applied to the gate of the first transfer NMOS transistor to turn on the first transfer NMOS transistor, thereby storing the seventh charge in the seventh phase segment [π / 8, 5π / 8] in the first capacitor unit.

[0157] In the eighth phase segment [5π / 8, 9π / 8], a high level is applied to the gate of the second transfer NMOS transistor to turn on the second transfer NMOS transistor, thereby storing the eighth charge in the eighth phase segment [5π / 8, 9π / 8] in the second capacitor unit.

[0158] The seventh charge amount is compared with the eighth charge amount through the differential amplifier 202 . In the fourth measurement cycle, the seventh charge amount is equal to the eighth charge amount, that is, the comparison result output is 1.

[0159] At this time, the charge difference between the seventh charge amount and the eighth charge amount is less than the preset threshold, and the measurement is stopped.

[0160] Finally, the comparison results 0, 1, 0, 1 are obtained, and the binary comparison results are converted into a decimal sum, i.e. 5, through the distance calculation module, and the distance to be measured is calculated as 5*Range / 2 4 =5*Range / 16.

[0161] In some embodiments, when X=4, the plurality of transfer NMOS transistors include first to fourth transfer NMOS transistors, the plurality of storage units include first to fourth capacitor units, and in one example, the charge comparison results include 00, 01, 10, 11.

[0162] In other embodiments, Figure 6For example, if the number of measurement cycles is 3, that is, the measurement is stopped after the comparison result is output in the third measurement cycle. In the third measurement cycle, the fifth charge quantity is greater than the sixth charge quantity. Therefore, the middle phase of the shaded part (that is, the charge quantity) in the fifth phase segment is taken as the received signal phase. At this time, the phase difference between the middle phase corresponding to the pulse width of the light pulse emission signal and the received signal phase is determined to be the phase difference Δφ between the signal emission and reception. However, since the charge difference between the fifth charge quantity and the sixth charge quantity is not less than the preset threshold, the phase difference Δφ at this time has an error.

[0163] In the above scheme, when the number of measurement cycles increases, the measurement accuracy also increases accordingly, but the time used for charge transfer is not shortened. Therefore, the situation where the ranging accuracy is affected by insufficient charge transfer speed will not occur, that is, the problem of reduced modulation contrast is solved.

[0164] In addition, the distance measurement module in the distance measurement circuit provided in the embodiment of the present invention can directly calculate the distance to be measured in a digital manner, without the need for digital-to-analog conversion and then calculating the distance to be measured, thereby avoiding the introduction of system errors and ensuring the measurement accuracy of the distance to be measured.

[0165] The measurement result of this embodiment satisfies a linear relationship with the distance to be measured, which further simplifies the process of data processing and error analysis. In addition, the differential amplifier has low power consumption and high precision, which further ensures work efficiency and measurement accuracy.

[0166] An embodiment of the present invention further provides an electronic device, comprising the above-mentioned distance measurement circuit.

[0167] In a specific embodiment, the electronic device includes a camera.

[0168] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A distance measurement method, characterized in that: include: using the optical pulse emission signal in at least one measurement cycle as a reference pulse signal; Determine the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, divide each phase segment to be divided into a plurality of phase segments, and compare the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result; Determining the measurement accuracy of the measuring device according to the number of measurement cycles of the reference pulse signal, the number of phase segments in each phase segment to be divided, and the maximum measurement distance of the measuring device; The distance to be measured is obtained based on the charge comparison result corresponding to the at least one measurement period and the measurement accuracy.

2. The distance measurement method according to claim 1, characterized in that: The step of determining the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, dividing each phase segment to be divided into a plurality of phase segments, and comparing the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result includes: The phase segment of the first measurement cycle is used as the first phase segment to be divided; Dividing the first phase segment to be divided into a plurality of phase segments, and comparing the charge amounts corresponding to the reference pulse signals in each phase segment to obtain a first charge comparison result; Based on the first charge comparison result, determine the second phase segment to be divided corresponding to the second measurement cycle; divide the second phase segment to be divided into phase segments and compare the charge amounts of the reference pulse signals in the corresponding phase segments; Repeat the following steps for the measurement cycles after the second measurement cycle: determine the phase segment to be divided in the next measurement cycle based on the charge comparison result of the previous phase segment to be divided, divide the phase segment to be divided into phase segments, and compare the charge amounts of the reference pulse signals in the corresponding phase segments, until the charge comparison results corresponding to all measurement cycles are obtained.

3. The distance measurement method according to claim 2, characterized in that: The step of dividing the first phase segment to be divided into a plurality of phase segments, and comparing the charge amounts corresponding to the reference pulse signals in each phase segment to obtain a first charge comparison result includes: dividing the first phase segment to be divided into a first phase segment and a second phase segment; Determine a first charge amount corresponding to the internal reference pulse signal corresponding to the first phase segment and a second charge amount corresponding to the internal reference pulse signal corresponding to the second phase segment; The first charge amount and the second charge amount are compared to obtain a first charge comparison result.

4. The distance measurement method according to claim 3, characterized in that: The determining, based on the first charge comparison result, a second phase segment to be divided corresponding to the second measurement cycle includes: When the first charge amount is greater than the second charge amount, the first phase segment is used as the second phase segment to be divided; When the first charge amount is less than or equal to the second charge amount, the second phase segment is used as the second phase segment to be divided.

5. The distance measurement method according to claim 4, characterized in that: The step of dividing the second phase segment to be divided into phase segments comprises: Based on the first charge comparison result, determining a measurement phase corresponding to the second phase segment to be divided, wherein the measurement phase is a phase point connected between two consecutive phase segments; According to the measured phase and the second phase segment to be divided, the second phase segment to be divided is evenly divided into a plurality of phase segments.

6. The distance measurement method according to claim 5, characterized in that: The step of determining the measurement phase corresponding to the second phase segment to be divided based on the first charge comparison result includes: Based on the first charge comparison result, the measurement phase corresponding to the second phase segment to be divided is determined to be t1±T / 4, where t1 is the measurement phase corresponding to the first measurement cycle, T is the measurement cycle, and the measurement phase of t1 is always T / 2.

7. The distance measurement method according to claim 6, characterized in that: The step of determining, based on the first charge comparison result, that the measurement phase corresponding to the second phase segment to be divided is t1±T / 4 comprises: When the first charge amount is greater than the second charge amount, determining that the measurement phase corresponding to the second phase segment to be divided is t1-T / 4; When the first charge amount is less than or equal to the second charge amount, it is determined that the measurement phase corresponding to the second phase segment to be divided is t1+T / 4.

8. The distance measurement method according to claim 3, characterized in that: The comparing the first charge amount and the second charge amount to obtain a first charge comparison result includes: When the first charge amount is greater than the second charge amount, a first charge comparison result of "0" is obtained; when the first charge amount is greater than or equal to the second charge amount, a first charge comparison result of "1" is obtained.

9. The distance measurement method according to claim 2, characterized in that: The measurement cycle after the second measurement cycle is repeated: determining the phase segment to be divided in the next measurement cycle based on the charge comparison result in the previous phase segment to be divided, dividing the phase segment to be divided into phase segments, and comparing the charge amounts of the reference pulse signals in the corresponding phase segments until the charge comparison results corresponding to all measurement cycles are obtained, including: Based on the charge comparison result in the previous phase segment to be divided, the measurement phase corresponding to the next phase segment to be divided is determined to be t N-1 ±T / X N , where N is the sequence number of the next measurement cycle in the multiple measurement cycles, and N ≥ 2, t N-1 is the measurement phase corresponding to the previous measurement cycle, T is the measurement cycle, X is the number of phase segments in one measurement cycle, and the measurement phase of t1 is always T / X.

10. The distance measurement method according to claim 1, characterized in that: Before obtaining the distance to be measured based on the charge comparison result corresponding to the at least one measurement period and the measurement accuracy, the distance measurement method further includes: Based on the charge comparison result, a charge difference is determined, wherein the charge difference is characterized by an absolute value of a difference between charge amounts corresponding to the reference pulse signal in each phase segment; Determine whether to stop measuring the comparison result according to the charge comparison result and / or the charge difference.

11. The distance measurement method according to claim 10, characterized in that: The step of determining whether to stop measuring the comparison result according to the charge comparison result and / or the charge difference includes: When the charge comparison results corresponding to all the measurement cycles are obtained, or the charge difference in any measurement cycle is less than a preset threshold, it is determined to stop measuring the comparison result.

12. The distance measurement method according to claim 11, characterized in that: After obtaining the charge comparison results corresponding to all the measurement cycles, or the charge difference in any measurement cycle is less than a preset threshold, and determining to stop measuring the comparison result, the method includes: Obtaining a charge comparison result of the at least one measurement cycle; Converting the sum of the charge comparison results of the plurality of measurement cycles into a sum of decimal values; Based on the sum of the decimal values ​​and the measurement accuracy, the distance to be measured is obtained.

13. A distance measurement circuit, characterized in that: include: A cycle selection module, used to use the optical pulse emission signal in at least one measurement cycle as a reference pulse signal; A comparison module is used to determine the phase segment to be divided corresponding to the reference pulse signal in each measurement cycle, divide each phase segment to be divided into multiple phase segments, and compare the charge amount corresponding to the reference pulse signal in each phase segment to obtain a charge comparison result; A measurement accuracy determination module, used to determine the measurement accuracy of the measurement device according to the number of measurement cycles of the reference pulse signal, the number of phase segments in each phase segment to be divided, and the maximum measurement distance of the measurement device; The module for determining the distance to be measured is used to obtain the distance to be measured based on the charge comparison result corresponding to the at least one measurement cycle and the measurement accuracy.

14. The distance measurement circuit according to claim 13, characterized in that: The comparison module includes a plurality of storage units, a photodiode and a differential amplifier, and the cycle selection module includes an output end; the anode of the photodiode is connected to the output end of the cycle selection module, and the cathode of the photodiode is suitable for converting the reference pulse signal into electric charge and outputting the electric charge to the input ends of the plurality of storage units; The input ends of the plurality of storage units are also connected to the output end of the differential amplifier, and the output ends of the plurality of storage units are connected to the first input end and the second input end of the differential amplifier; The output end of the differential amplifier is also connected to the input end of the measurement accuracy determination module.

15. The distance measurement circuit according to claim 14, characterized in that: The plurality of storage units include a plurality of transfer NMOS tubes, a plurality of capacitor units and a floating gate node; In one of the storage units, the gate of the transfer NMOS tube is connected to the output end of the differential amplifier, the drain of the transfer MOS tube is connected to the cathode of the photodiode, the source of the transfer NMOS tube is connected to the floating gate node and the first end of the capacitor unit, and the second end of the capacitor unit is grounded.

16. An electronic device, characterized in that: The distance measurement circuit comprises the distance measurement circuit as claimed in any one of claims 13 to 15.

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