CN114270208A

CN114270208A - Time-of-flight measurement circuit and related system, electronic device and method

Info

Publication number: CN114270208A
Application number: CN202080054073.2A
Authority: CN
Inventors: 范铨奇; 林奇青; 杨富强; 杨孟达
Original assignee: Shenzhen Goodix Technology Co Ltd
Current assignee: Shenzhen Goodix Technology Co Ltd
Priority date: 2020-11-13
Filing date: 2020-11-13
Publication date: 2022-04-01
Also published as: WO2022099594A1

Abstract

A time-of-flight measurement circuit, system, method and electronic device. The time-of-flight measurement circuit (100) includes a pixel array (102), a time-to-digital converter (104), and a controller (106). The pixel array (102) includes m rows by n columns of pixel cells (P11-Pmn). The time-to-digital converter (104) includes n time-to-digital conversion units (L1-Ln). The controller (106) is configured to control the a-th row of pixel cells (Pa 1-Pan) to be enabled to receive the first reflected light pulse during a first time window and to be enabled to receive the second reflected light pulse during a second time window, and the first time window have different time lengths.

Description

Time-of-flight measurement circuit and related system, electronic device and method

Technical Field

The present disclosure relates to a measurement circuit, and more particularly to a time-of-flight measurement circuit, a time-of-flight measurement system, an electronic device, and a time-of-flight measurement method.

Background

The time-of-flight measurement technique includes a direct time-of-flight measurement technique and an indirect time-of-flight measurement technique, wherein the direct time-of-flight measurement technique is to transmit a light pulse to a target object, measure a time interval between a reception time of a reflected light pulse reflected from the target object and a transmission time of the light pulse, obtain a time-of-flight of the light, and calculate depth information using the measured time-of-flight.

However, dust in the air reflects and scatters light pulses to cause interference, and the farther the object to be measured is, the more susceptible the interference is. Therefore, how to reduce interference and improve accuracy is one of the problems to be solved in the art.

Disclosure of Invention

An objective of the present application is to disclose a time-of-flight measurement circuit, a related time-of-flight measurement system, an electronic device, and a method for time-of-flight measurement, so as to solve the above problems.

An embodiment of the present application discloses a time-of-flight measurement circuit, which is used for measuring a time interval of a first optical pulse and a second optical pulse emitted by a pulse generation unit reflecting back to the time-of-flight measurement circuit after the first optical pulse and the second optical pulse start from a target object, and the time-of-flight measurement circuit includes: a pixel array comprising m rows by n columns of pixel units, wherein m and n are positive integers, and each pixel unit comprises: a light sensitive sensor for generating a first trigger signal upon receipt of a first reflected light pulse reflected by said first light pulse back to said time of flight circuitry and for generating a second trigger signal upon receipt of a second reflected light pulse reflected by said second light pulse back to said time of flight circuitry; a controller, coupled to the pixel array and the pulse generating unit, for controlling the pulse generating unit to emit the first light pulse and the second light pulse, and controlling the pixel units in the a-th row to be enabled to receive the first reflected light pulse in a first time window and the pixel units in the a-th row to be enabled to receive the second reflected light pulse in a second time window, and controlling each pixel unit in the a-th row to output the first trigger signal and the second trigger signal through the a-th row selection line of m-th row selection lines, wherein a is an integer from 1 to m, and the first trigger signal and the second trigger signal sequentially pass through the pixel units in the (a +1) th row to the m-th row from the output end of each pixel unit in the a-th row, the time lengths of the first time window and the first time window are different; and a time-to-digital converter comprising: n time-to-digital conversion units, including the 1 st to the nth time-to-digital conversion units, and coupled to the n output terminals of the 1 st to nth rows of the pixel units in the mth row, respectively, where the n first time-to-digital conversion units perform time-to-digital conversion based on the n first trigger signals and the n second trigger signals received from the output terminals of each of the pixel units in the mth row, so as to correspondingly obtain n first conversion results and n second conversion results.

An embodiment of the present application discloses an amount of time-of-flight measurement system, including: a pulse generating unit for emitting a plurality of light pulses to a target object; and the time of flight measurement circuit described above.

An embodiment of the present application discloses an electronic device, including the above time-of-flight measurement system.

An embodiment of the present application discloses an above-mentioned time-of-flight measurement method, for measuring a time interval between a first light pulse and a second light pulse emitted by a pulse generation unit and reflected back to the time-of-flight measurement circuit after the first light pulse and the second light pulse start from a target object, the time-of-flight measurement method includes: controlling the pulse generating unit to emit the first light pulse; receiving a first reflected light pulse reflected back by the first light pulse in a first time window and generating a first trigger signal; generating a first conversion result based on the first trigger signal; controlling the pulse generating unit to emit the second light pulse; receiving a second reflected light pulse reflected back by the second light pulse in a second time window and generating a second trigger signal, wherein the time lengths of the first time window and the first time window are different; and generating a second conversion result based on the second trigger signal.

The time-of-flight measurement circuit of the present application utilizes different time windows to receive reflected light pulses to reduce the probability of interference.

Drawings

FIG. 1 is a schematic diagram of a first embodiment of an time-of-flight measurement circuit of the present application.

Fig. 2 is a circuit diagram of a pixel unit in a pixel array.

FIG. 3 is a first embodiment of a timing diagram for time-of-flight measurements performed by the time-of-flight measurement circuit of the present application.

FIG. 4 is a second embodiment of a timing diagram for time-of-flight measurements performed by the time-of-flight measurement circuit of the present application.

FIG. 5 is a third embodiment of a timing diagram for time-of-flight measurements performed by the time-of-flight measurement circuit of the present application.

FIG. 6 is a schematic diagram of a second embodiment of the time of flight measurement circuit of the present application.

Detailed Description

The following disclosure provides various embodiments or illustrations that can be used to implement various features of the disclosure. The embodiments of components and arrangements described below serve to simplify the present disclosure. It is to be understood that such descriptions are merely illustrative and are not intended to limit the present disclosure. For example, in the description that follows, forming a first feature on or over a second feature may include certain embodiments in which the first and second features are in direct contact with each other; and may also include embodiments in which additional elements are formed between the first and second features described above, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or characters in the various embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Moreover, spatially relative terms, such as "under," "below," "over," "above," and the like, may be used herein to facilitate describing a relationship between one element or feature relative to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass a variety of different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Although numerical ranges and parameters setting forth the broad scope of the application are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain standard deviations found in their respective testing measurements. As used herein, "about" generally refers to actual values within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range. Alternatively, the term "about" means that the actual value falls within the acceptable standard error of the mean, subject to consideration by those of ordinary skill in the art to which this application pertains. It is understood that all ranges, amounts, values and percentages used herein (e.g., to describe amounts of materials, length of time, temperature, operating conditions, quantitative ratios, and the like) are modified by the term "about" in addition to the experimental examples or unless otherwise expressly stated. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, these numerical parameters are to be understood as meaning the number of significant digits recited and the number resulting from applying ordinary carry notation. Herein, numerical ranges are expressed from one end to the other or between the two ends; unless otherwise indicated, all numerical ranges set forth herein are inclusive of the endpoints.

Fig. 1 is a schematic diagram of a time-of-flight measurement circuit 100 according to a first embodiment of the present invention, in which the time-of-flight measurement circuit 100 is used to measure a time interval after a plurality of light pulses emitted by a pulse generating unit (not shown) are reflected back to the time-of-flight measurement circuit 100 from a start to a target (not shown), and a direct time-of-flight measurement technique is used. For example, the pulse generating unit may include, but is not limited to, a driving circuit and a light emitting unit. The driving circuit is used for driving the light-emitting unit to enable the light-emitting unit to intermittently emit light pulses LT. The light emitting unit may be, but is not limited to, a semiconductor laser (which may also be called a Laser Diode (LD)), a Light Emitting Diode (LED), or other light emitting units capable of generating light pulses, wherein the light pulses generated by the semiconductor laser are coherent light (coherent light), and the light pulses generated by the light emitting diode are incoherent light (incoherent light).

The time of flight measurement circuit 100 includes a pixel array 102, a time-to-digital converter 104, and a controller 106. Specifically, the pixel array 102 includes m rows × n columns of pixel units, where m and n are positive integers, for example, the pixel unit P11 represents the 1 st row and 1 st column of pixel units in the pixel array 102, and the pixel unit Pmn represents the m th row and n th column of pixel units in the pixel array 102, where each pixel unit in the pixel array 102 is the same in the present embodiment. Each pixel cell in the pixel array 102 includes a photosensor for generating a trigger signal when a reflected light pulse LR is received, which is reflected back to the time-of-flight circuitry 100 by the light pulse LT. Generally, the photosensitive sensor can be implemented with a single photon avalanche diode, but the application is not limited thereto.

Referring to fig. 1 and 2 together, fig. 2 is a circuit diagram of the pixel units P22, P23, P32 and P33 in the pixel array 102. It should be noted that each pixel cell in the pixel array 102 is the same, and therefore the pixel cells P22, P23, P32 and P33 shown in fig. 2 can also be used to illustrate other pixel cells not shown. Taking the pixel cell P22 as an example, it can be seen that in addition to the avalanche diode D22, the avalanche diode D22 further includes a switch T22, a current source I22, a buffer B22 and an and gate a22, wherein an anode of the avalanche diode D22 is coupled to a reference voltage V1, the switch T22 is coupled between a cathode of the avalanche diode D22 and the reference voltage V2, and in this embodiment, the reference voltage V2 is a ground voltage. The current source I22 is coupled to the cathode of the avalanche diode implementation D22, the buffer B22 is coupled to the cathode of the avalanche diode D22 and a first input of the and gate a22, and a second input of the and gate a22 is coupled to the row select line to receive the signal RS 2. In fig. 2, the switch T22 is implemented by using an N-type transistor, and a gate of the N-type transistor receives a control signal E2 from the controller 106 to control the switch T22 to be selectively conductive or non-conductive. When the N-type transistor is turned on, the cathode of the avalanche diode D22 is limited to the reference voltage V2, i.e., the avalanche diode D22 is maintained in the reset state, so that the pixel cell P22 is disabled, and even if reflected light is irradiated to the pixel cell P22, the charges sensed by the avalanche diode D22 cannot be read out; conversely, when the N-type transistor is not turned on, the cathode of the avalanche diode implementation D22 is not limited to the reference voltage V2, i.e., the pixel unit P22 is enabled, and the charge sensed by the avalanche diode D22 can be output as a trigger signal.

The controller 106 is coupled to the pixel array 102 and the pulse generating unit for controlling the pulse generating unit to emit the light pulse LT. The controller 106 correspondingly enables or disables m rows of pixel unit selection through m row selection lines, for example, the controller 106 sets RSa in the control signals RS 1-RSm to high potential, and sets signals except RSa in the control signals RS 1-RSm to low potential, so as to realize selection of the a-th row of pixel units Pa 1-Pan, wherein a is any integer from 1 to m. At this time, the trigger signals of the pixel units Pa 1-Pan are respectively output from the output terminals of the pixel units Pa 1-Pan to the input terminals of the pixel units in the next row, that is, in the case of fig. 1, the trigger signals are transmitted in a downward longitudinal direction, that is, when a is smaller than m, the trigger signals are output from the output terminals of the pixel units Pa 1-Pan in the a-th row, and then sequentially pass through the (a +1) -th row to the pixel units in the m-th row and are output as the trigger signals TDCI 1-TDCIn; when a is equal to m, the trigger signals are directly output from the respective output terminals of the m-th row pixel units Pm1 to Pmn as trigger signals TDCI1 to TDCIn. The above is for illustrative purposes only, and more than one row of pixel cells may actually be selected at the same time.

In contrast to this, before the controller 106 outputs the trigger signals of the pixel units in the a-th row through the row selection line, it needs to control the enabled time windows of the pixel units in the a-th row, specifically, each of the pixel units in the a-th row is enabled only in the time window to receive the reflected light pulse LR to generate the trigger signal. Thus, for each light pulse LT, there is a corresponding time window for each of the pixel cells in row a to sense the reflected light pulse LR. The time windows for different light pulses LT may have different specifications, the variable specification comprising the time length of the time window, or the time length between the start of the time window and the corresponding emission time point of the light pulse LT, or the time length between the end of the time window and the corresponding emission time point of the light pulse LT. The details of which are described later.

In the present embodiment, the controller 106 controls the time window of each of the a-th row pixel cells Pa1 to Pan by the control signal Ea. For example, in the case of the embodiment shown in fig. 2, when Ea in the control signals E1 to Em is set to a low potential, the controller 106 enables the a-th row pixel cells Pa1 to Pan; when Ea in the control signals E1 to Em is set to a high potential, the controller 106 disables the a-th row pixel cells Pa1 to Pan. In the present embodiment, the a-th row pixel cells Pa 1-Pan are synchronously controlled to be enabled, i.e. the timing of the time window of the a-th row pixel cells Pa 1-Pan is the same. But may be separately controlled in some embodiments. It should be noted that the controller 106 controls the time window of only one row of pixel units at a time to perform sensing to generate the trigger signals of the plurality of pixel units in the row of pixel units, and outputs the trigger signals of the plurality of pixel units in the row of pixel units through the row selection line.

The time-to-digital converter 104 includes a counter 1040 and n registers L1-Ln. The counter 1040 counts according to the reference clock and the signal TX. The signal TX is used to indicate the point in time at which the light pulse LT is emitted. The n registers L1-Ln include registers L1 through Ln, wherein the registers L1-Ln are adjacent to each other on the layout diagram and are correspondingly coupled to the n outputs of the pixel units Pm 1-Pmn, and the registers L1-Ln temporarily store the count values TDCO 1-TDCOn of the counter 1040 to represent the measured flight time based on the trigger signals TDCI 1-TDCIn received from the n outputs of the pixel units Pm 1-Pmn, respectively. That is, when the pixel unit Pm1 outputs the trigger signal TDCI1 to the register L1, the register L1 will temporarily store the counting result of the counter 1040 as the counting value TDCO 1. In the present embodiment, the counter 1040 is coupled to the controller 106, and the controller 106 can transmit the signal TX to the counter 1040, and can reset the counter 1040 by other signals (not shown), i.e. clear the counter 1040.

Referring to fig. 1 and fig. 3, fig. 3 is a timing diagram of a time-of-flight measurement performed by the time-of-flight measurement circuit according to the first embodiment of the present invention. The controller 106 controls the pulse generating unit to emit light pulses LT1 and LT2 at time points T1 and T3, respectively, and simultaneously controls the counter 1040 to start counting from zero. The pixel units Pa1 to Pan in row a receive reflected light pulses LR1 and LR2 reflected by the light pulses LT1 and LT2 from the target at time points T2 and T4, respectively, where the difference between the time point T2 and the time point T1 is equal to the difference between the time point T4 and the time point T3, that is, the flight times of the reflected light pulses LR1 and LR2 reflected from the target are the same, that is, the row distances of the reflected light pulses LR1 and LR2 reflected from the target to the flight time measuring circuit 100 are the same at . Since each of the a-th row pixel cells Pa 1-Pan is disabled when the control signal Ea is 1; when the control signal Ea is 0, each of the a-th row pixel cells Pa 1-Pan is enabled, that is, when the control signal Ea is 0

At 1, each of the a-th row pixel cells Pa 1-Pan is enabled; when the control signal Ea is 0, each of the a-th row pixel cells Pa1 to Pan is disabled. FIG. 3 shows the inverse of the control signal Ea

So that the range of the time window (i.e. the inverted signal) can be more intuitively recognized by a person

A time period of 1). In fig. 3, the control signal Ea given by the controller 106 is different for the light pulses LT1 and LT2, and therefore the time window W1 for the light pulse LT1 and the time window W2 for the light pulse LT2 have different specifications.

Specifically, the time length TS1 of the time window W1 is greater than the time length TS2 of the time window W2. The length of time between the start of the time window W1 and the emission time point of the light pulse LT1 is 0; the length of time between the start of the time window W2 and the emission time point of the light pulse LT2 is TS 3. The length of time between the end of the time window W1 and the emission time point of the light pulse LT1 is TS 1; the end of the time window W2 is TS1 as long as the time length between the emission time points of the light pulse LT 2.

In the present embodiment, the time window W1 has a larger detection range than the time window W2, the time window W1 has a larger detection range, because the time window W1 starts at the emission time point of the optical pulse LT1, and the reflected optical pulses reflected by the short-distance and long-distance targets can be detected, as shown in fig. 3, no matter the LR1 appears at any time in the TS1 interval, and the closer the LR1 is to the start point of the LT1, the closer the LR1 is reflected from the target. The time window W2 starts at TS3 after the emission time point of the light pulse LT2, that is, the difference between the time window W1 and the time window W2 is that the time window W2 cannot detect any signal reflected back within the time when the emission time point of the light pulse LT2 starts at TS3, that is, the time window W2 cannot detect the reflected light pulse reflected back by the object at a short distance. Therefore, the time window W1 can be said to be the time window for the far-near global detection; the time window W2 is a time window for remote detection. In fig. 3, the distance between the target object and the time-of-flight circuit 100 is relatively long, the reflected light pulses LR1 and LR2 for the light pulse LT1 and the light pulse LT2 both fall within the range of the time windows W1 and W2, and the count values TDCO1 obtained by the register L1 are D1 and D2, respectively, and since the times of flight of the reflected light pulses LR1 and LR2 are the same, D1 and D2 are also the same.

Because the time-of-flight measurement is full of many possible errors and interferences, in the time-of-flight measurement system, a plurality of reflected light pulses are continuously received by the same row of pixel units, and a plurality of results are counted to obtain a statistical result. For example, the a-th row of pixel cells Pa 1-Pan receives one hundred reflected light pulses of one hundred light pulses reflected back from the target. The controller 106 may adjust the ratio of the corresponding time window W1 and the time window W2 for the one hundred reflected light pulses, for example, if the distance of the target object is set to be long, 80 of the one hundred reflected light pulses may be allocated as the corresponding time window W2, and the remaining 20 may be allocated as the corresponding time window W1.

Referring to fig. 1 and 4, fig. 4 is a timing diagram of a time-of-flight measurement performed by the time-of-flight measurement circuit according to a second embodiment of the present invention. The controller 106 controls the pulse generating unit to emit light pulses LT1 and LT2 at time points T1 and T3, respectively, and simultaneously controls the counter 1040 to start counting from zero. The pixel units Pa1 to Pan in row a receive reflected light pulses LR1 and LR2 reflected by the light pulses LT1 and LT2 from the target at time points T2 and T4, respectively, where the difference between the time point T2 and the time point T1 is equal to the difference between the time point T4 and the time point T3, that is, the flight times of the reflected light pulses LR1 and LR2 reflected from the target are the same, that is, the row distances of the reflected light pulses LR1 and LR2 reflected from the target to the flight time measuring circuit 100 are the same at . The specification of the time windows W1 and W2 used in fig. 4 is the same as the specification of the time windows W1 and W2 used in fig. 3, but the distance between the target object and the time-of-flight measurement circuit 100 in fig. 4 is shorter than the distance between the target object and the time-of-flight measurement circuit 100 in fig. 3, so that it can be seen that the time of the reflected light pulse LR2 caused by the light pulse LT2 in fig. 4 reaching the a row a pixel cells Pa1 to Pan is earlier than the start time of the time window W2, so that no trigger signal TDC1 to the register L1 exists within the range of the time window W2, in this application, if the trigger signal is not received at the end of the time window, the controller 106 may control the register to temporarily store a preset count value (the control circuit is not shown in fig. 1), for example, the preset count value DM may be stored in the register, so that in fig. 4, the TDCO1 for LT2 is the preset count value DM, so that the subsequent calculation circuit (not shown in the figures) finds that the register generates a count value larger than a reasonable value, the object to be measured is known to be in close range.

Referring to fig. 1 and 5, fig. 5 is a third embodiment of a timing chart of the time-of-flight measurement performed by the time-of-flight measurement circuit according to the present application. The controller 106 controls the pulse generating unit to emit light pulses LT1 and LT2 at time points T1 and T3, respectively, and simultaneously controls the counter 1040 to start counting from zero. The pixel units Pa1 to Pan in row a receive reflected light pulses LR1 and LR2 reflected by the light pulses LT1 and LT2 from the target at time points T2 and T4, respectively, where the difference between the time point T2 and the time point T1 is equal to the difference between the time point T4 and the time point T3, that is, the flight times of the reflected light pulses LR1 and LR2 reflected from the target are the same, that is, the row distances of the reflected light pulses LR1 and LR2 reflected from the target to the flight time measuring circuit 100 are the same at . The specification of the time windows W1 and W2 used in fig. 5 is the same as the specification of the time windows W1 and W2 used in fig. 3 and 4, and the distance between the object of fig. 5 and the time-of-flight circuit 100 is as close as the distance between the object of fig. 3 and the time-of-flight circuit 100, with the difference that the object of fig. 5 and the time-of-flight circuit 100 are dust-disturbed, so that the optical pulse LT1 generates a disturbing optical pulse LR1 'and reaches the a-th row of pixel cells Pa1 to Pan at a time point T2' before the time point T2; and causing the light pulse LT2 to generate the disturbance light pulse LR2 'and reach the a-th row pixel cells Pa1 to Pan at a time point T4' before the time point T4. The interference light pulse LR1 'falls within the range of the time window W1, thereby causing the trigger signal TDC1 to be generated to the register L1, so that the register L1 is temporarily stored to the wrong count value D1' instead of the value D1 corresponding to the reflected light pulse LR 1. However, the interference light pulse LR2' falls outside the range of the time window W2, so the count value D2 registered in the register L1 correctly corresponds to the reflected light pulse LR2, avoiding interference.

In this embodiment, in order to improve the accuracy of the distance detection and the contrast of the distance information, for the consecutive light pulses LT, the controller 106 may use a time window for the distance detection, such as the time window W2; and for a few of them, a time window for far and near global detection, such as time window W1, is used. In certain embodiments, the controller 106 dynamically adjusts the ratio of the two time windows. In some embodiments, the controller 106 further uses a time window for proximity detection.

In some embodiments, the time-to-digital converter 104 may be implemented using a delay line, such as in fig. 6. FIG. 6 is a schematic diagram of a second embodiment of the time of flight measurement circuit of the present application. The difference between the time of flight measurement circuit 600 of FIG. 6 and the time of flight measurement circuit 100 of FIG. 1 is that the time-to-digital converter 604 of the time of flight measurement circuit 600 of FIG. 6 includes n time-to-digital conversion units 1041-104 n adjacent to the m-th rows of pixel cells Pm 1-Pmn, and more specifically, the n time-to-digital conversion units 1041-104 n are adjacent and correspondingly coupled to n outputs of the m-th rows of pixel cells Pm 1-Pmn. The n time-to-digital conversion units 1041 to 104n perform time-to-digital conversion based on the signal TX obtained from the controller 106 and the trigger signals TDCI1 to TDCIn received from the output terminals of the m-th row pixel units Pm1 to Pmn, respectively, to correspondingly obtain n conversion results TDCO1A to tdclona. The remainder of the time of flight measurement circuit 600 is identical to the time of flight measurement circuit 100.

Compared to the embodiment of FIG. 1 using the counter 1040, the implementation using the delay line as shown in FIG. 6 can obtain a resolution higher than that of the counter 1040, but the delay lines in the n time-to-digital conversion units 1041-104 n may have the problems of mismatch and signal coupling with each other.

The present application also provides a time-of-flight measurement system that includes the pulse generation unit and a time-of-flight measurement circuit 100/600. The present application also provides a chip that includes time of flight circuitry 100/600. The application also provides an electronic device which comprises the chip or the flight time measuring system. The electronic device may be any electronic device such as a smart phone, a personal digital assistant, a handheld computer system, a tablet computer, or a digital camera, among others.

The time-of-flight circuit 100/600 of the present application utilizes the variation of the time window to adjust the range of the desired range, and generally speaking, the interference of the long-range measurement is more, so the interference signal before the actual reflected light pulse arrives can be eliminated by adjusting the time window, and the accuracy of the long-range measurement can be enhanced. Since the accuracy of short-range distance measurement is originally much higher than that of long-range distance measurement, the proportion of the time window of short-range distance measurement or global distance measurement is reduced in real time, and the influence is not too large.

The foregoing description has set forth briefly the features of certain embodiments of the present application so that those skilled in the art may more fully appreciate the various aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should understand that they can still make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

1. A time-of-flight circuit for measuring a time interval during which a first optical pulse and a second optical pulse emitted by a pulse generating unit are reflected back to the time-of-flight circuit from a start to an object, the time-of-flight circuit comprising: a pixel array comprising m rows by n columns of pixel units, wherein m and n are positive integers, and each pixel unit comprises:

a light sensitive sensor for generating a first trigger signal upon receipt of a first reflected light pulse reflected by said first light pulse back to said time of flight circuitry and for generating a second trigger signal upon receipt of a second reflected light pulse reflected by said second light pulse back to said time of flight circuitry;

a controller, coupled to the pixel array and the pulse generating unit, for controlling the pulse generating unit to emit the first light pulse and the second light pulse, and controlling the pixel units in the a-th row to be enabled to receive the first reflected light pulse in a first time window and the pixel units in the a-th row to be enabled to receive the second reflected light pulse in a second time window, and controlling each pixel unit in the a-th row to output the first trigger signal and the second trigger signal through the a-th row selection line of m-th row selection lines, wherein a is an integer from 1 to m, and the first trigger signal and the second trigger signal sequentially pass through the pixel units in the (a +1) th row to the m-th row from the output end of each pixel unit in the a-th row, the time lengths of the first time window and the first time window are different; and

a time-to-digital converter comprising:

n time-to-digital conversion units, including the 1 st to the nth time-to-digital conversion units, and coupled to the n output terminals of the 1 st to nth rows of the pixel units in the mth row, respectively, where the n first time-to-digital conversion units perform time-to-digital conversion based on the n first trigger signals and the n second trigger signals received from the output terminals of each of the pixel units in the mth row, so as to correspondingly obtain n first conversion results and n second conversion results.

2. The time-of-flight measurement circuit of claim 1, wherein the first time window has a first length of time between the start of the first time window and the point in time of transmission of the first optical pulse and the second time window has a second length of time between the start of the second time window and the point in time of transmission of the second optical pulse, wherein the first length of time is less than the second length of time.

3. The time-of-flight measurement circuit of claim 2, wherein the first time window has a first third length of time between its end and the point in time of transmission of the first light pulse, and the second time window has a fourth length of time between its end and the point in time of transmission of the second light pulse, wherein the third length of time is equal to the fourth length of time.

4. The time-of-flight measurement circuit of claim 1, wherein each of the pixel cells further comprises:

a switch coupled between one end of the photosensor and a first reference voltage, the switch being controlled by the controller to be turned on to disable the pixel unit or to be turned off to enable the pixel unit.

5. The time-of-flight measurement circuit of claim 4, wherein each of the pixel cells further comprises:

and an and gate having a first input terminal coupled to the one end of the photosensor and a second input terminal coupled to one of the m row select lines, an output terminal of the and gate generating an output result and outputting from the output terminal of the pixel unit.

6. The time of flight measurement circuit of claim 5, in which the first reference voltage is a ground voltage, and the first input of the AND gate is the ground voltage when the switch is turned on.

7. An amount of time-of-flight measurement system, comprising:

a pulse generating unit for emitting a plurality of light pulses to a target object; and

the time of flight measurement circuit of any one of claims 1 to 6.

8. An electronic device, comprising:

the system for measuring amount of time of flight of claim 7.

9. A time-of-flight measurement method for measuring a time interval during which a first optical pulse and a second optical pulse emitted from a pulse generating unit are reflected back to a time-of-flight measurement circuit after the first optical pulse and the second optical pulse start from a target object, the time-of-flight measurement method comprising: controlling the pulse generating unit to emit the first light pulse;

receiving a first reflected light pulse reflected back by the first light pulse in a first time window and generating a first trigger signal;

generating a first conversion result based on the first trigger signal;

controlling the pulse generating unit to emit the second light pulse;

receiving a second reflected light pulse reflected back by the second light pulse in a second time window and generating a second trigger signal, wherein the time lengths of the first time window and the first time window are different; and

a second conversion result is generated based on the second trigger signal.

10. The method of claim 9, wherein the first time window has a first length of time between the start of the first time window and the point in time of the emission of the first light pulse, and wherein the second time window has a second length of time between the start of the second time window and the point in time of the emission of the second light pulse, wherein the first length of time is less than the second length of time.

11. The method of claim 10, wherein a first third length of time is between an end of the first time window and a point in time of emission of the first light pulse, and a fourth length of time is between an end of the second time window and a point in time of emission of the second light pulse, wherein the third length of time is equal to the fourth length of time.