Time-of-flight sensor pixel circuit and method of configuring the same

Abstract

A time-of-flight sensor pixel circuit and a configuration method thereof belong to the field of sensors, and a photoelectric conversion element receives a modulated light wave to generate electric charges; the modulated light wave is sent by a light source emission circuit and reflected to the photoelectric conversion element by a target object; the modulated light wave is a pulse modulated light wave with a pulse length of T and a period of 3T; three charge storage and transfer circuits store background photoelectric charges, synchronous photoelectric charges and quadrature photoelectric charges respectively to generate three integrated charge signals; and a charge readout circuit outputs three photoelectric signals according to the three integrated charge signals. Therefore, the light source emission circuit only needs to emit the modulated light wave of the same frame once, and the time information can be calculated, so that the power consumption of the light source is low, and the three integrated charge signals are generated by the modulated light wave emitted once, so that the information distortion of the moving object is avoided, and the acquisition accuracy of the time information is improved.

Description

Technical Field

[0001] This application belongs to the field of sensors, and in particular relates to a time-of-flight sensor pixel circuit and its configuration method. Background Technology

[0002] A time-of-flight (TOF) sensor is an important component of ranging devices, capable of capturing three-dimensional (3D) distance information of a target object and obtaining a 3D image. It is widely used in behavior analysis, surveillance, autonomous driving, artificial intelligence, machine vision perception, and 3D image enhancement. TOF sensors use the time-of-flight method to measure the travel time of light from the light source's emission point to the target object's reflection and then to the sensor's receiving point, thereby determining the distance information of the target object. TOF sensors can obtain the light travel time directly or indirectly. The indirect method involves recording the phase difference of the light pulse from emission to reception, and then calculating the light travel time.

[0003] A time-of-flight sensor typically includes a light source emitting circuit and a light source sensing module. The light source emitting circuit emits a sine wave or a pulsed square wave of a specific frequency; the light source sensing module records the phase difference between the time interval from light emission to light reception, and then calculates the distance information of the object being measured. The aforementioned light source sensing module typically includes a photosensitive pixel circuit and a photoelectric signal processing circuit. The photosensitive pixel circuit obtains time data indirectly, and then deduces the time information.

[0004] The photosensitive pixel circuit uses a multi-microframe operation to obtain complete time information. This requires the light source emitting circuit to emit the same frame of modulated periodic light wave multiple times, resulting in high power consumption of the light source. Furthermore, multi-microframe operation can also cause information distortion of moving objects. Summary of the Invention

[0005] The purpose of this application is to provide a time-of-flight sensor pixel circuit and its configuration method, which aims to solve the defects of traditional time-of-flight sensors, such as high power consumption of light source and information distortion of moving objects.

[0006] This application provides a time-of-flight sensor pixel circuit, including:

[0007] A photoelectric conversion element is configured to receive modulated light waves to generate electric charge; the modulated light waves are emitted by a light source emitting circuit and reflected by a target object to the photoelectric conversion element; the modulated light waves are pulse-modulated light waves with a pulse duration of T and a period of 3T.

[0008] A first charge storage and transfer circuit, connected to the photoelectric conversion element, is configured to store background light photoelectric charge according to a first charge output signal to generate a first integrated charge signal, and output the first integrated charge signal according to a first control selection signal; the background light photoelectric charge is the charge generated by the photoelectric conversion element during a time period of duration T before and immediately adjacent to the pulse.

[0009] The second charge storage and transfer circuit, connected to the photoelectric conversion element, is configured to store synchronous photoelectric charge according to the second charge output signal to generate a second integrated charge signal, and output the second integrated charge signal according to the second control selection signal; the synchronous photoelectric charge is the charge generated by the photoelectric conversion element during a time period T synchronized with the pulse;

[0010] A third charge storage and transfer circuit, connected to the photoelectric conversion element, is configured to store orthogonal photoelectric charges according to the third charge output signal to generate a third integrated charge signal, and to output the third integrated charge signal according to a third control selection signal; the orthogonal photoelectric charges are the charges generated by the photoelectric conversion element during a time period of duration T immediately following and adjacent to the pulse.

[0011] A charge readout circuit is connected to the output terminals of the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit. It is configured to output a first photoelectric signal based on the first integrated charge signal to obtain a first calculation signal, output a second photoelectric signal based on the second integrated charge signal to obtain a second calculation signal, and output a third photoelectric signal based on the third integrated charge signal to obtain a third calculation signal.

[0012] The flight time is obtained based on the first calculation signal, the second calculation signal, and the third calculation signal.

[0013] This application embodiment also provides a method for configuring the above-mentioned time-of-flight sensor pixel circuit, including:

[0014] For each of the three time periods of each cycle of the modulated light wave, three charge output signals are input respectively, so that the three charge storage and conversion circuits store the background light photoelectric charge, the synchronization photoelectric charge, and the orthogonal photoelectric charge respectively to generate three integrated charge signals; wherein, the three time periods of each cycle of the modulated light wave are the time period of duration T before and immediately adjacent to the pulse, the time period of duration T synchronized with the pulse, and the time period of duration T after and immediately adjacent to the pulse;

[0015] After repeating at least one cycle, proceed to the next step;

[0016] Three control selection signals are input so that the three charge storage and transfer circuits output the three integrated charge signals according to the three control selection signals to obtain three calculation signals.

[0017] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows: Since the three charge storage and transfer circuits store the background light photoelectric charge, the synchronous photoelectric charge and the orthogonal photoelectric charge respectively to generate three integrated charge signals, the data of a pixel contains the photoelectric signals of the three phases of the modulated light wave, so the time information can be calculated without multi-frame operation, which reduces the power consumption of the light source emission module, eliminates the problem of distortion of the perception information of moving objects, and improves the accuracy of time information acquisition. Attached Figure Description

[0018] To more clearly illustrate the technical inventions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of a time-of-flight sensor pixel circuit provided in an embodiment of this application;

[0020] Figure 2 This is a schematic diagram of another structure of the time-of-flight sensor pixel circuit provided in one embodiment of this application;

[0021] Figure 3 This is a schematic diagram of another structure of the time-of-flight sensor pixel circuit provided in one embodiment of this application;

[0022] Figure 4 An example circuit schematic diagram of a time-of-flight sensor pixel circuit provided in an embodiment of this application;

[0023] Figure 5 For the corresponding Figure 4 Key signal timing diagram of the pixel circuit of the time-of-flight sensor. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0025] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0026] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0028] Figure 1 A schematic diagram of the pixel circuit of the time-of-flight sensor provided in a preferred embodiment of this application is shown. For ease of explanation, only the parts relevant to this embodiment are shown, and are described in detail below:

[0029] The aforementioned time-of-flight sensor pixel circuit includes a photoelectric conversion element 11, a first charge storage and transfer circuit 12, a second charge storage and transfer circuit 13, a third charge storage and transfer circuit 14, and a charge readout circuit 15.

[0030] The photoelectric conversion element 11 is configured to receive modulated light waves to generate charges; the modulated light waves are emitted by the light source emitting circuit and reflected by the target object to the photoelectric conversion element 11; the modulated light waves are pulse modulated light waves with a pulse duration of T and a period of 3T; T is a positive number.

[0031] The first charge storage and transfer circuit 12 is connected to the photoelectric conversion element 11 and is configured to store the background light photoelectric charge according to the first charge output signal to generate a first integrated charge signal, and output the first integrated charge signal according to the first control selection signal; the background light photoelectric charge is the charge generated by the photoelectric conversion element 11 during the time period of T before and immediately after the pulse.

[0032] The second charge storage and transfer circuit 13 is connected to the photoelectric conversion element 11 and is configured to store synchronous photoelectric charge according to the second charge output signal to generate a second integrated charge signal, and output the second integrated charge signal according to the second control selection signal; the synchronous photoelectric charge is the charge generated by the photoelectric conversion element 11 during a time period T synchronized with the pulse.

[0033] The third charge storage and transfer circuit 14 is connected to the photoelectric conversion element 11 and is configured to store orthogonal photoelectric charges according to the third charge output signal to generate a third integrated charge signal, and output the third integrated charge signal according to the third control selection signal; the orthogonal photoelectric charges are the charges generated by the photoelectric conversion element 11 in the time period of T immediately following and adjacent to the pulse.

[0034] The charge readout circuit 15 is connected to the output terminals of the first charge storage and transfer circuit 12, the second charge storage and transfer circuit 13, and the third charge storage and transfer circuit 14. It is configured to output a first photoelectric signal based on the first integrated charge signal to obtain a first calculation signal, output a second photoelectric signal based on the second integrated charge signal to obtain a second calculation signal, and output a third photoelectric signal based on the third integrated charge signal to obtain a third calculation signal.

[0035] The time of flight is obtained based on a first calculation signal, a second calculation signal, and a third calculation signal. These three calculation signals are obtained based on a pixel-by-frame operation.

[0036] In one example, it is noteworthy that the input terminals of the first charge storage and transfer circuit 12, the second charge storage and transfer circuit 13, and the third charge storage and transfer circuit 14 are all connected to the output terminal of the photoelectric conversion element 11. Alternatively, the input terminal of the charge readout circuit can also be connected to this output terminal. The output terminal of the photoelectric conversion element 11 can be its negative terminal; for example, the photoelectric conversion element 11 can be selected as a photodiode. Thus, the charge generated by the photoelectric conversion element 11 receiving the modulated light wave is negative, improving charge mobility.

[0037] like Figure 2 As shown, in one example, the time-of-flight sensor pixel circuit also includes a first transmission switch circuit 16 and a second transmission switch circuit 17.

[0038] The first transmission switch circuit 16 is connected between the first charge storage and transfer circuit 12, the second charge storage and transfer circuit 13, the third charge storage and transfer circuit 14 and the photoelectric conversion element 11, and is configured to control the transfer of charge between the photoelectric conversion element 11 and the first charge storage and transfer circuit 12, the second charge storage and transfer circuit 13, and the third charge storage and transfer circuit 14.

[0039] The second transmission switch circuit 17 is connected between the first charge storage and transfer circuit 12, the second charge storage and transfer circuit 13, the third charge storage and transfer circuit 14, and the charge readout circuit 15, and is configured to control the transmission of integrated charge between the first charge storage and transfer circuit 12, the second charge storage and transfer circuit 13, the third charge storage and transfer circuit 14 and the charge readout circuit 15.

[0040] By setting the second transmission switch circuit 17, the background light photoelectric charge, synchronous photoelectric charge and orthogonal photoelectric charge are prevented from being directly output from the charge readout circuit 15, thereby improving the accuracy of the time-of-flight sensor pixel circuit.

[0041] like Figure 3 As shown, in one example, the time-of-flight sensor pixel circuitry also includes an anti-charge crosstalk circuit 18.

[0042] The anti-blooming circuit 18 is connected to the photoelectric conversion element 11, the first charge storage and transfer circuit 12, the second charge storage and transfer circuit 13, the third charge storage and transfer circuit 14, and the charge readout circuit 15, and is configured to clear the charge in the photoelectric conversion element 11 according to the anti-blooming control signal.

[0043] By using the anti-charge crosstalk circuit 18, the charge in the photoelectric conversion element 11 is cleared during each time information measurement, thereby improving the accuracy of time information acquisition.

[0044] By setting the first transmission switch circuit 16, interference from the anti-charge crosstalk circuit 18 to the charge storage and transfer circuit can also be prevented.

[0045] This invention also provides a method for configuring a pixel circuit of a time-of-flight sensor, including steps 101 and 102.

[0046] Step 101: For each of the three time periods corresponding to each cycle of the modulated light wave, input three charge output signals respectively, so that the three charge storage and conversion circuits store the background light photoelectric charge, the synchronous photoelectric charge, and the orthogonal photoelectric charge respectively to generate three integrated charge signals; after repeating at least one cycle, execute the next step.

[0047] The three time periods of each cycle of the modulated light wave are the time period of duration T before and immediately after the pulse, the time period of duration T synchronized with the pulse, and the time period of duration T after and immediately after the pulse.

[0048] In specific implementation, step 101 may include steps A1 to A3.

[0049] Step A1: During the time period of T before and immediately after the pulse, the first charge output signal is input, and the first charge storage and transfer circuit stores the background light photoelectric charge according to the first charge output signal to generate the first integrated charge signal.

[0050] Step A2: During the time period T synchronized with the pulse, the second charge output signal is input, and the second charge storage and transfer circuit stores the synchronous photoelectric charge according to the second charge output signal to generate the second integrated charge signal.

[0051] Step A3: During the time period of T immediately following and adjacent to the pulse, the third charge output signal is input. The third charge storage and transfer circuit stores the orthogonal photoelectric charge according to the third charge output signal to generate the third integrated charge signal.

[0052] Step 102: Input three control selection signals so that the three charge storage and transfer circuits output three integrated charge signals according to the three control selection signals to obtain three calculation signals.

[0053] In a specific implementation, step 102 may include steps A4 to A9.

[0054] Step A4: Input the first control selection signal, and the first charge storage and transfer circuit outputs the first integrated charge signal according to the first control selection signal.

[0055] Step A5: The charge readout circuit outputs the first photoelectric signal based on the first integrated charge signal.

[0056] Step A6: Input the second control selection signal, and the second charge storage and transfer circuit outputs the second integrated charge signal according to the second control selection signal.

[0057] Step A7: The charge readout circuit outputs a second photoelectric signal based on the second integrated charge signal.

[0058] Step A8: Input the third control selection signal, and the third charge storage and transfer circuit outputs the third integrated charge signal according to the third control selection signal.

[0059] Step A9: The charge readout circuit outputs the third photoelectric signal based on the third integrated charge signal.

[0060] In practice, the output order of the first integrated charge signal, the second integrated charge signal, and the third integrated charge signal can be adjusted adaptively according to actual needs.

[0061] As an example and not a limitation, step A4 is preceded by steps A3-4, step A6 is preceded by steps A5-2, and step A8 is preceded by steps A7-2.

[0062] Step A3-4: Input the first reset control signal, and the charge readout circuit outputs the first reset signal according to the first reset control signal.

[0063] Step A5-2: Input the second reset control signal, and the charge readout circuit outputs the second reset signal according to the second reset control signal.

[0064] Step A7-2: Input the third reset control signal, and the charge readout circuit outputs the third reset signal according to the third reset control signal.

[0065] It is worth noting that steps 99a and 100a may be included before step 101, and steps 101-2a and 101-3a may be included before step 102.

[0066] Step 99a: Input the first transmission control signal. The first transmission switch circuit controls the transmission of charge between the photoelectric conversion element and the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit according to the first transmission control signal.

[0067] Step 100a: Stop inputting the second transmission control signal; the second transmission switch circuit stops the transmission of integrated charge between the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit and the charge readout circuit.

[0068] Step 101-2a: Stop inputting the first transmission control signal; the first transmission switch circuit stops the transmission of charge between the photoelectric conversion element and the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit.

[0069] Step 101-3a: Input the second transmission control signal, and the second transmission switch circuit controls the transmission of integrated charge between the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit to the charge readout circuit.

[0070] When transferring charge, the input of the second transmission control signal is stopped to turn off the second transmission switch circuit; this prevents the background light photoelectric charge, synchronous photoelectric charge, and orthogonal photoelectric charge from being directly output from the charge readout circuit and thus forming leakage current, thereby improving the accuracy of the time-of-flight sensor pixel circuit.

[0071] As an example and not a limitation, step 100b precedes step 101; and step 101-2b precedes step 102.

[0072] Step 100b: Before starting exposure, input the anti-charge crosstalk control signal. The anti-charge crosstalk circuit clears the charge in the photoelectric conversion element according to the anti-charge crosstalk control signal. Stop inputting the anti-charge crosstalk control signal and exposure begins.

[0073] Step 101-2b: Stop exposure, input anti-charge crosstalk control signal, and the anti-charge crosstalk circuit clears the charge in the photoelectric conversion element according to the anti-charge crosstalk control signal.

[0074] By removing the charge from the photoelectric conversion element before and after exposure, the accuracy of time information acquisition is improved.

[0075] In specific implementation, the first reset control signal, the second reset control signal, the third reset control signal, the anti-charge crosstalk control signal, the first charge output signal, the second charge output signal, the third charge output signal, the first control selection signal, the second control selection signal, and the third control selection signal can be output by control logic.

[0076] Figure 4 An example circuit structure of a time-of-flight sensor pixel circuit provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below:

[0077] The first transmission switch circuit 16 includes a first charge transfer transistor 103; the second transmission switch circuit 17 includes a second charge transfer transistor 104. The anti-charge crosstalk circuit 18 includes an anti-charge crosstalk transistor 102. The drain of the first charge transfer transistor 103 is connected to a photoelectric conversion element, and the source of the first charge transfer transistor 103 is connected to a first charge storage and transfer circuit, a second charge storage and transfer circuit, and a third charge storage and transfer circuit. The drain of the second charge transfer transistor 104 is connected to the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit, and the source of the second charge transfer transistor 104 is connected to a charge readout circuit.

[0078] The charge readout circuit 15 includes a charge storage device 108 and a signal output circuit. The signal output circuit outputs a first photoelectric signal, a second photoelectric signal, and a third photoelectric signal based on the charge storage device 108.

[0079] The charge readout circuit 15 includes a reset transistor 105, a source follower transistor 106, and a pixel selection transistor 107.

[0080] The first terminal of the charge storage device 108, the source of the reset transistor 105, and the gate of the source follower transistor 106 are all connected to the input terminal of the charge readout circuit, which serves as the first integrated charge signal input terminal, the second integrated charge signal input terminal, and the third integrated charge signal input terminal. The gate of the reset transistor 105 is connected to the reset signal control line, serving as the first reset control signal input terminal, the second reset control signal input terminal, and the third reset control signal input terminal of the charge readout circuit 15. The drain of the reset transistor 105 and the source follower transistor 106 are connected to the first terminal of the charge readout circuit 108, the second terminal of the reset transistor 105, and the third terminal of the source follower transistor 106. The drain of transistor 106 is connected to the first power supply Vdd. The source of source follower transistor 106 is connected to the drain of pixel selection transistor 107. The source of pixel selection transistor 107 is connected to the output terminal of charge readout circuit 15. The output terminal of charge readout circuit 15 serves as the first photoelectric signal output terminal, the second photoelectric signal output terminal of charge readout circuit 15, the first reset signal output terminal of charge readout circuit 15, the second reset signal output terminal of charge readout circuit 15, and the third reset signal output terminal of charge readout circuit 15. The second terminal of charge storage device 108 is connected to a first voltage. The first voltage can be any value specified according to actual needs, or it can represent that the second terminal of charge storage device 108 is grounded.

[0081] The first charge storage and transfer circuit 12 includes a first switching transistor 109 and a first MOS transistor capacitor 112.

[0082] The drain of the first switching transistor 109 is connected to the output terminal of the photoelectric conversion element to receive the background light photoelectric charge input terminal of the first charge storage and transfer circuit 12 and to serve as the first integrated charge signal output terminal. The gate of the first switching transistor 109 is connected to the first charge storage and transfer control line to serve as the first charge output signal input terminal and the first control selection signal input terminal. The source of the first switching transistor 109 is connected to the active region of the first MOS transistor capacitor 112, and the gate of the first MOS transistor capacitor 112 is connected to the first control signal.

[0083] The second charge storage and transfer circuit 13 includes a second switching transistor 110 and a second MOS transistor capacitor 113.

[0084] The drain of the second switching transistor 110 is connected to the output terminal of the photoelectric conversion element to receive synchronous photoelectric charge and serve as the output terminal of the second integrated charge signal. The gate of the second switching transistor 110 is connected to the second charge storage and transfer control line to serve as the input terminal of the second charge output signal and the input terminal of the second control selection signal. The source of the second switching transistor 110 is connected to the active region of the second MOS transistor capacitor 113. The gate of the second MOS transistor capacitor 113 is connected to the second control signal.

[0085] The third charge storage and transfer circuit 14 includes a third switching transistor 111 and a third MOS transistor capacitor 114.

[0086] The drain of the third switching transistor 111 is connected to the output terminal of the photoelectric conversion element to receive orthogonal photoelectric charge and serve as the third integrated charge signal output terminal. The gate of the third switching transistor 111 is connected to the third charge storage and transfer control line to serve as the third charge output signal input terminal and the third control selection signal input terminal. The source of the third switching transistor 111 is connected to the active region of the third MOS transistor capacitor 114. The gate of the third MOS transistor capacitor 114 is connected to the third control signal.

[0087] The anti-charge crosstalk circuit 18 includes an anti-charge crosstalk transistor 102.

[0088] The photoelectric conversion element 11 includes, but is not limited to, a pinned photodiode, a polysilicon gate photodiode, and a current-assisted photodiode; the charge storage device includes, but is not limited to, a MOS transistor capacitor, a polysilicon gate-insulator-polysilicon gate capacitor, and a metal-insulator-metal capacitor.

[0089] The following is based on the working principle. Figure 4 Further explanation is provided below:

[0090] The pixel-by-frame operation comprises three stages: a pixel reset stage, a photoelectric signal demodulation stage, and a photoelectric signal output stage. The pixel reset stage, located at the beginning of the pixel-by-frame operation, aims to clear the charge from the photoelectric conversion element 11, as well as from the first MOS transistor capacitor 112, the second MOS transistor capacitor 113, and the third MOS transistor capacitor 114, preparing for the photoelectric signal demodulation stage. Upon completion of the pixel reset stage, the light source emitting circuit begins operation, continuously emitting periodic square modulated light waves, thus entering the second stage, the photoelectric signal demodulation stage.

[0091] In the photoelectric signal demodulation stage, located in the middle of a pixel-by-frame operation, the photoelectric conversion element 11 receives the background light and the modulated light wave, converts the background light and the modulated light wave into charges, and collects the background light photoelectric charge, the synchronization photoelectric charge, and the quadrature photoelectric charge into the first MOS transistor capacitor 112, the second MOS transistor capacitor 113, and the third MOS transistor capacitor 114, respectively. When the second stage of photoelectric signal demodulation is completed, the light source emission circuit is turned off, and the third stage of photoelectric signal output begins.

[0092] The third stage, the photoelectric signal output stage, follows the photoelectric signal demodulation stage. This stage involves clearing the charge from the charge storage device 108, outputting a reset signal using the signal output line (output terminal of the charge readout circuit), and transferring the charges from the first MOS transistor capacitor 112, the second MOS transistor capacitor 113, and the third MOS transistor capacitor 114 to the charge storage device 108, respectively, and then outputting the corresponding first, second, and third photoelectric signals using the signal output line. After the photoelectric signal output stage is completed, the pixel one-frame cycle operation is finished.

[0093] A schematic diagram illustrating the specific timing configuration method for the pixel circuit of the time-of-flight sensor to acquire photoelectric signals, as shown below. Figure 5 As shown, where, Figure 5 for Figure 4 The timing diagram shown corresponds to the pixel circuit of the time-of-flight sensor. It is understood that this timing diagram is an example, and those skilled in the art can make corresponding adjustments based on common knowledge in the art to obtain other example timing diagrams.

[0094] Figure 5 In the diagram, 301 represents the pixel reset stage, 302 represents the photoelectric charge demodulation stage, and 303 represents the photoelectric signal output stage. The light wave emitted by the light source emitting circuit is a modulated light wave (pulse-period square wave) with a pulse duration of T and a period of 3T. A high level at the gate terminal of each transistor indicates that the transistor is in the on state, and a low level at the gate terminal of each transistor indicates that the transistor is in the off state. The read timing shown is the timing sequence for reading the signal from the pixel circuit in the photoelectric signal processing circuit. A high level indicates reading the signal output from the pixel circuit.

[0095] Pixel reset stage 301 is described as follows.

[0096] The light source emitting circuit does not emit modulated light waves. The gate Anti of the anti-charge crosstalk transistor 102 is set to a high level (input anti-charge crosstalk control signal), the gate RST of the reset transistor 105 is set to a high level, the gate TX of the first charge transfer transistor 103 and the gate TXb of the second charge transfer transistor 104 are set to a high level, the gate OG1 of the first switching transistor 109, the gate OG2 of the second switching transistor 110 and the gate OG3 of the third switching transistor 111 are set to a high level, the gate SG1 of the first MOS transistor capacitor 112, the gate SG2 of the second MOS transistor capacitor 113 and the gate SG3 of the third MOS transistor capacitor 114 are kept at a low level, the gate RS of the pixel selection transistor 107 is kept at a low level, the charge in the photoelectric conversion element 11101 is cleared, and the charge in the first MOS transistor capacitor 112, the second MOS transistor capacitor 113 and the third MOS transistor capacitor 114 is cleared at the same time.

[0097] After the charges in the aforementioned devices are cleared, the pixel reset phase 301 ends. The gate Anti of the anti-charge crosstalk transistor 102 is set to low (stopping the input of the anti-charge crosstalk control signal), the gate RST of the reset transistor 105 is set to low, the gate TXb of the second charge transfer transistor 104 is set to low, the gate OG2 of the second switching transistor 110 and the gate OG3 of the third switching transistor 111 are set to low, the gate SG1 of the first MOS transistor capacitor 112, the gate SG2 of the second MOS transistor capacitor 113, and the gate SG3 of the third MOS transistor capacitor 114 are set to high, the gate OG1 of the first switching transistor 109 remains high, and the gate RS of the pixel selection transistor 107 remains low. The pixel reset phase 301 ends, and the photoelectric charge demodulation phase 302 begins, at which point the light source emitting circuit starts emitting modulated light waves.

[0098] The photoelectric charge demodulation stage 302 is described as follows.

[0099] The light source emitting circuit continuously emits pulse-modulated light waves with a pulse duration of T and a period of 3T; the gate Anti of the anti-charge crosstalk transistor 102 remains at a low level, the gate RST of the reset transistor 105 remains at a low level, the gate TX of the first charge transfer transistor 103 remains at a high level (inputting the first charge output signal), the gate TXb of the second charge transfer transistor 104 remains at a low level (stopping the input of the second transmission control signal), the gate SG1 of the first MOS transistor capacitor 112, the gate SG2 of the second MOS transistor capacitor 113, and the gate SG3 of the third MOS transistor capacitor 114 remain at a high level, and the gate RS of the pixel selection transistor 107 remains at a low level.

[0100] During the period of T before and immediately after the pulse, the gate OG1 of the first switching transistor 109 is in a high-level state, the gate OG2 of the second switching transistor 110 and the gate OG3 of the third switching transistor 111 are in a low-level state, and the charge generated in the photoelectric conversion element 11101 is transferred to the first MOS transistor capacitor 112. This charge is the background light photoelectric charge.

[0101] During a time period of T synchronized with the modulated light pulse, the gate OG2 of the second switching transistor 110 is in a high-level state (inputting the second charge output signal), while the gate OG1 of the first switching transistor 109 and the gate OG3 of the third switching transistor 111 are in a low-level state (inputting the third charge output signal). The photoelectric charge generated in the photoelectric conversion element 11 is transferred to 113, and this charge is the synchronous photoelectric charge.

[0102] During the period of T immediately following and immediately adjacent to the pulse, the gate OG3 of the third switching transistor 111 is at a high level, while the gate OG1 of the first switching transistor 109 and the gate OG2 of the second switching transistor 110 are at a low level. The photoelectric charge generated in the photoelectric conversion element 11 is transferred to 114, and this charge is an orthogonal photoelectric charge.

[0103] When the photoelectric signal demodulation stage 302 is completed, the light source emitting circuit stops emitting modulated light waves, the gate terminal Anti of the anti-charge crosstalk transistor 102 is set to a high level, the gate TX of the first charge transfer transistor 103 is set to a low level, the gate terminal TXb of the second charge transfer transistor 104 is set to a high level, and the gate terminal RS of 107 is set to a high level, thus entering the third stage, the photoelectric signal output stage 303.

[0104] The photoelectric signal output stage 303 is described as follows.

[0105] The light source emitting module remains in a stopped emitting modulated light wave state, the gate Anti of the anti-charge crosstalk transistor 102 remains in a high level state (input anti-charge crosstalk control signal), the gate TX of the first charge transfer transistor 103 remains in a low level state, the gate TXb of the second charge transfer transistor 104 remains in a high level state, and the gate RS of the pixel selection transistor 107 remains in a high level state.

[0106] First, a high-level pulse (first reset control signal) is applied to the gate RST of the reset transistor 105 to clear the charge in the charge storage device 108. The high-level pulse SHR1 in the subsequent read timing indicates that the pixel outputs the first reset signal through the signal line output, denoted as R1.

[0107] After the first reset signal R1 is output, the gate terminal OG1 of the first switching transistor 109 is set to a high level (inputting the first control selection signal), and immediately thereafter the gate terminal SG1 of the first MOS transistor capacitor 112 is set to a low level (inputting the first control signal). The photoelectric charge in the first MOS transistor capacitor 112 is transferred to the charge storage device 108. After the charge transfer is completed, the gate terminal OG1 of the first switching transistor 109 is set to a low level. The high-level pulse SHS1 in the subsequent read timing indicates that the pixel outputs the first photoelectric signal through the signal line output, which is called the background light initial photoelectric signal, denoted as S1.

[0108] Secondly, a high-level pulse (input second reset control signal) is given to the gate RST of the reset transistor 105 to clear the charge in the charge storage device 108. The high-level pulse SHR2 in the subsequent read timing indicates that the pixel outputs the second reset signal through the signal line output, denoted as R2.

[0109] After the second reset signal R2 is output, the gate OG2 of the second switching transistor 110 is set to a high level, and immediately thereafter the gate SG2 of the second MOS transistor capacitor 113 is set to a low level (input second control signal). The photoelectric charge in the second MOS transistor capacitor 113 is transferred to the charge storage device 108. After the charge transfer is completed, the gate OG2 of the second switching transistor 110 is set to a low level. The high-level pulse SHS2 in the subsequent read timing indicates that the pixel outputs the second photoelectric signal through the signal line output, which is called the initial photoelectric signal of the modulation light wave synchronization window, denoted as S2.

[0110] Finally, a high-level pulse (input third reset control signal) is given to the gate RST of the reset transistor 105 to clear the charge in the charge storage device 108. The high-level pulse SHR3 in the subsequent read timing indicates that the pixel outputs the third reset signal through the signal line output, denoted as R3.

[0111] After the third reset signal R3 is output, the gate OG3 of the third switching transistor 111 is set to a high level, and immediately thereafter the gate SG3 of the third MOS transistor capacitor 114 is set to a low level (inputting the third control signal). The charge in the third MOS transistor capacitor 114 is transferred to the charge storage device 108. After the charge transfer is completed, the gate OG3 of the third switching transistor 111 is set to a low level. The high-level pulse SHS3 in the subsequent read timing indicates that the pixel outputs the third photoelectric signal through the signal line output, which is called the initial photoelectric signal of the modulated light wave quadrature window, denoted as S3.

[0112] The photoelectric signal output stage 303 is complete, and the one-frame cycle operation of the pixel is finished.

[0113] It should be noted that the first target photoelectric signal PE1 of the background light phase is equal to the first reset signal R1 minus the first photoelectric signal S1; the second target photoelectric signal PE2 of the modulated light wave synchronization window phase is equal to the second reset signal R2 minus the second photoelectric signal S2; and the third target photoelectric signal PE3 of the modulated light wave orthogonal window phase is equal to the third reset signal R3 minus the third photoelectric signal S3. Therefore, the time it takes for the modulated light to travel from the light source emitting module to the light source sensing module is:

[0114]

[0115] Therefore, based on the speed of light c in air, the distance d of the object being measured can be calculated:

[0116]

[0117] In this embodiment of the invention, a photoelectric conversion element receives a modulated light wave to generate a charge. The modulated light wave is emitted by a light source emitting circuit and reflected by a target object to the photoelectric conversion element. The modulated light wave is a pulsed modulated light wave with a pulse duration of T and a period of 3T. A first charge storage and transfer circuit stores the background light photoelectric charge according to a first charge output signal to generate a first integrated charge signal, and outputs the first integrated charge signal according to a first control selection signal. The background light photoelectric charge is the charge generated by the photoelectric conversion element during a time period of T before and immediately after the pulse. A second charge storage and transfer circuit stores the synchronous photoelectric charge according to a second charge output signal to generate a second integrated charge signal. The first integrated charge signal is generated by the photoelectric conversion element during a time period of duration T synchronized with the pulse. The second integrated charge signal is generated by the second integrated charge signal and the second integrated charge signal is generated by the third integrated charge signal. The third charge storage and transfer circuit stores the orthogonal photoelectric charge according to the third charge output signal to generate the third integrated charge signal, and outputs the third integrated charge signal according to the third control selection signal. The orthogonal photoelectric charge is generated by the photoelectric conversion element during a time period of duration T following and immediately adjacent to the pulse. The charge readout circuit outputs the first photoelectric signal according to the first integrated charge signal, the second photoelectric signal according to the second integrated charge signal, and the third photoelectric signal according to the third integrated charge signal. Since the three charge storage and transfer circuits store the background light photoelectric charge, the synchronization photoelectric charge, and the orthogonal photoelectric charge respectively to generate three integrated charge signals, a frame of data of a pixel contains photoelectric signals of the three phases of the modulated light wave: background light photoelectric signal, modulation light wave synchronization window photoelectric signal, and modulation light wave orthogonal window photoelectric signal. Time information can be directly obtained, and then the distance information of the measured object can be calculated. The pixel circuit and configuration method of the time-of-flight sensor of the present invention do not require multi-frame operation, thus effectively reducing the light emission power consumption of the light source emission module, eliminating the problem of distortion of the perception information of moving objects, and improving the accuracy of time information acquisition.

[0118] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0119] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A pixel circuit for a time-of-flight sensor, characterized in that, include: A photoelectric conversion element configured to receive modulated light waves to generate electric charge; The modulated light wave is emitted by the light source emitting circuit and reflected by the target object to the photoelectric conversion element; The modulated light wave is a pulse modulated light wave with a pulse duration of T and a period of 3T; A first charge storage and transfer circuit is connected to the photoelectric conversion element and configured to store background light photoelectric charge according to a first charge output signal to generate a first integrated charge signal, and output the first integrated charge signal according to a first control selection signal. The background light photoelectric charge is the charge generated by the photoelectric conversion element during a time period of duration T before and immediately adjacent to the pulse; The second charge storage and transfer circuit is connected to the photoelectric conversion element and is configured to store synchronous photoelectric charge according to the second charge output signal to generate a second integrated charge signal, and output the second integrated charge signal according to the second control selection signal. The synchronous photoelectric charge is the charge generated by the photoelectric conversion element during a time period T synchronized with the pulse; A third charge storage and transfer circuit, connected to the photoelectric conversion element, is configured to store orthogonal photoelectric charges according to the third charge output signal to generate a third integrated charge signal, and to output the third integrated charge signal according to a third control selection signal; the orthogonal photoelectric charges are the charges generated by the photoelectric conversion element during a time period of duration T immediately following and adjacent to the pulse. A charge readout circuit is connected to the output terminals of the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit. It is configured to output a first photoelectric signal based on the first integrated charge signal to obtain a first calculation signal, output a second photoelectric signal based on the second integrated charge signal to obtain a second calculation signal, and output a third photoelectric signal based on the third integrated charge signal to obtain a third calculation signal. The flight time is obtained based on the first calculation signal, the second calculation signal, and the third calculation signal. The time-of-flight sensor pixel circuit further includes: a first transmission switch circuit, a second transmission switch circuit, and an anti-charge crosstalk circuit; and the charge readout circuit includes a charge storage device and a signal output circuit, wherein: An anti-charge crosstalk circuit is connected to the photoelectric conversion element and the first transmission switch circuit; the first transmission switch circuit is connected between each charge storage and transfer circuit and the photoelectric conversion element; and the first transmission switch circuit is disposed between the anti-charge crosstalk circuit and each charge storage and transfer circuit; and the second transmission switch circuit is connected between each charge storage and transfer circuit and the charge readout circuit. The first charge storage and transfer circuit includes a first switching transistor and a first MOS transistor capacitor; The drain of the first switching transistor is connected to the output terminal of the photoelectric conversion element, the source of the first switching transistor is connected to the active region of the first MOS transistor capacitor, and the gate of the first MOS transistor capacitor is connected to the first control signal. The second charge storage and transfer circuit includes a second switching transistor and a second MOS transistor capacitor; The drain of the second switching transistor is connected to the output terminal of the photoelectric conversion element, the source of the second switching transistor is connected to the active region of the second MOS transistor capacitor, and the gate of the second MOS transistor capacitor is connected to the second control signal. The third charge storage and transfer circuit includes a third switching transistor and a third MOS transistor capacitor; The drain of the third switching transistor is connected to the output terminal of the photoelectric conversion element, the source of the third switching transistor is connected to the active region of the third MOS transistor capacitor, and the gate of the third MOS transistor capacitor is connected to the third control signal. During the photoelectric charge demodulation stage, the gate SG1 of the first MOS transistor capacitor, the gate SG2 of the second MOS transistor capacitor, and the gate SG3 of the third MOS transistor capacitor remain at a high level. The first transfer switch circuit includes a first charge transfer transistor, and the second transfer switch circuit includes a second charge transfer transistor; During the photoelectric signal output stage, the gate of the anti-charge crosstalk transistor is input with an anti-charge crosstalk control signal, the gate of the first charge transfer transistor is kept at a low level, and the gate of the second charge transfer transistor is kept at a high level. During the photoelectric charge demodulation stage, the gate of the first charge transport transistor remains at a high level, while the gate of the second charge transport transistor remains at a low level. In the photoelectric signal output stage, the gates SG1, SG2, and SG3 of the first MOS transistor capacitor, the second MOS transistor capacitor, and the third MOS transistor capacitor are sequentially set to low level in a time-division manner.

2. The time-of-flight sensor pixel circuit as described in claim 1, characterized in that, The input terminals of the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit are all connected to the output terminal of the photoelectric conversion element.

3. The time-of-flight sensor pixel circuit as described in claim 1, characterized in that, Also includes: A first transmission switch circuit is connected between the first charge storage and transfer circuit, the second charge storage and transfer circuit, the third charge storage and transfer circuit, and the photoelectric conversion element, and is configured to control the transmission of charge from the photoelectric conversion element to the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit; A second transmission switch circuit is connected between the first charge storage and transfer circuit, the second charge storage and transfer circuit, the third charge storage and transfer circuit, and the charge readout circuit, and is configured to control the transmission of integrated charge between the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit and the charge readout circuit.

4. The time-of-flight sensor pixel circuit as described in claim 1, characterized in that, The charge readout circuit includes a charge storage device and a signal output circuit. The signal output circuit outputs the first photoelectric signal, the second photoelectric signal, and the third photoelectric signal based on the charge storage device.

5. The time-of-flight sensor pixel circuit as described in claim 4, characterized in that, The signal output circuit includes a reset transistor, a source follower transistor, and a pixel selection transistor; The first terminal of the charge storage device, the source of the reset transistor, and the gate of the source follower transistor are all connected to the input terminal of the charge readout circuit, which serves as the first integrated charge signal input terminal, the second integrated charge signal input terminal, and the third integrated charge signal input terminal. The gate of the reset transistor is connected to the reset signal control line to serve as the first reset control signal input terminal, the second reset control signal input terminal, and the third reset control signal input terminal of the charge readout circuit. The drain of the reset transistor and the drain of the source follower transistor are both connected to the first power supply; The source of the source follower transistor is connected to the drain of the pixel select transistor, and the source of the pixel select transistor is connected to the output terminal of the charge readout circuit. The output terminal of the charge readout circuit serves as the first photoelectric signal output terminal, the second photoelectric signal output terminal, the third photoelectric signal output terminal, the first reset signal output terminal, the second reset signal output terminal, and the third reset signal output terminal. The second terminal of the charge storage device is connected to a first voltage.

6. The time-of-flight sensor pixel circuit as described in claim 1, characterized in that, The drain of the first switching transistor is connected to the output terminal of the photoelectric conversion element to receive the background light photoelectric charge and serve as the first integrated charge signal output terminal. The gate of the first switching transistor is connected to the first charge storage and transfer control line to serve as the first charge output signal input terminal and the first control selection signal input terminal. The drain of the second switching transistor is connected to the output terminal of the photoelectric conversion element to receive the synchronous photoelectric charge and serve as the output terminal of the second integrated charge signal. The gate of the second switching transistor is connected to the second charge storage and transfer control line to serve as the input terminal of the second charge output signal and the input terminal of the second control selection signal. The drain of the third switching transistor is connected to the output terminal of the photoelectric conversion element to receive the orthogonal photoelectric charge and serve as the output terminal of the third integrated charge signal. The gate of the third switching transistor is connected to the third charge storage and transfer control line to serve as the input terminal of the third charge output signal and the input terminal of the third control selection signal.

7. The time-of-flight sensor pixel circuit as described in any one of claims 1 to 6, characterized in that, Also includes: An anti-charge crosstalk circuit is connected to the photoelectric conversion element, the first charge storage and transfer circuit, the second charge storage and transfer circuit, the third charge storage and transfer circuit, and the charge readout circuit, and is configured to clear the charge in the photoelectric conversion element according to the anti-charge crosstalk control signal.

8. The time-of-flight sensor pixel circuit as described in any one of claims 1 to 6, characterized in that, The first calculation signal, the second calculation signal, and the third calculation signal are obtained based on pixel-by-frame operation.

9. A method for configuring a time-of-flight sensor pixel circuit as described in any one of claims 1-6, characterized in that, include: For each of the three time periods of each cycle of the modulated light wave, three charge output signals are input respectively, so that the three charge storage and conversion circuits store the background light photoelectric charge, the synchronization photoelectric charge, and the orthogonal photoelectric charge respectively to generate three integrated charge signals; wherein, the three time periods of each cycle of the modulated light wave are the time period of duration T before and immediately adjacent to the pulse, the time period of duration T synchronized with the pulse, and the time period of duration T after and immediately adjacent to the pulse; After repeating at least one cycle, proceed to the next step; Three control selection signals are input so that the three charge storage and transfer circuits output the three integrated charge signals according to the three control selection signals to obtain three calculation signals.

10. The method for configuring the pixel circuit of the time-of-flight sensor as described in claim 9, characterized in that, The methods for generating three integrated charge signals include: During a time period of duration T before and immediately adjacent to the pulse, a first charge output signal is input, and the first charge storage and transfer circuit stores the background light photoelectric charge according to the first charge output signal to generate a first integrated charge signal; During a time period T synchronized with the pulse, a second charge output signal is input, and the second charge storage and transfer circuit stores the synchronous photoelectric charge according to the second charge output signal to generate a second integrated charge signal; During a time period of duration T following and immediately adjacent to the pulse, a third charge output signal is input. The third charge storage and transfer circuit stores orthogonal photoelectric charges according to the third charge output signal to generate a third integrated charge signal.

11. The method for configuring the pixel circuit of the time-of-flight sensor as described in claim 9, characterized in that, The method for obtaining the three calculated signals by inputting the three control selection signals includes: When a first control selection signal is input, the first charge storage and transfer circuit outputs the first integrated charge signal according to the first control selection signal. The charge readout circuit outputs a first photoelectric signal based on the first integrated charge signal; When a second control selection signal is input, the second charge storage and transfer circuit outputs the second integrated charge signal according to the second control selection signal. The charge readout circuit outputs a second photoelectric signal based on the second integrated charge signal; When a third control selection signal is input, the third charge storage and transfer circuit outputs the third integrated charge signal according to the third control selection signal; The charge readout circuit outputs a third photoelectric signal based on the third integrated charge signal.

12. The method for configuring the pixel circuit of the time-of-flight sensor as described in claim 11, characterized in that, Before the first charge storage and transfer circuit outputs the first integrated charge signal and after generating the first integrated charge signal, the second integrated charge signal, and the third integrated charge signal, the following is also included: When a first reset control signal is input, the charge readout circuit outputs a first reset signal based on the first reset control signal. The method further includes the following steps before the second charge storage and transfer circuit outputs the second integrated charge signal and after outputting the first integrated charge signal: A second reset control signal is input, and the charge readout circuit outputs a second reset signal according to the second reset control signal; Before the third charge storage and transfer circuit outputs the third integrated charge signal and after outputting the second integrated charge signal, the following method is also included: A third reset control signal is input, and the charge readout circuit outputs a third reset signal according to the third reset control signal.

13. The method for configuring the pixel circuit of the time-of-flight sensor as described in claim 9, characterized in that, Before the three charge storage and conversion circuits store the background light photoelectric charge, the synchronous photoelectric charge, and the orthogonal photoelectric charge to generate three integrated charge signals, the following steps are also included: A first transmission control signal is input, and the first transmission switch circuit controls the transmission of charge between the photoelectric conversion element and the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit according to the first transmission control signal; Stop inputting the second transmission control signal; the second transmission switch circuit stops the transmission of the integrated charge between the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit to the charge readout circuit; The process of inputting three control selection signals to output the three integrated charge signals, both before and after generating the three integrated charge signals, further includes: Stop inputting the first transmission control signal; the first transmission switch circuit stops the transmission of charge between the photoelectric conversion element and the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit; The second transmission control signal is input, and the second transmission switch circuit controls the transmission of the integrated charge between the first charge storage and transfer circuit, the second charge storage and transfer circuit, and the third charge storage and transfer circuit to the charge readout circuit.

14. The method for configuring the pixel circuit of the time-of-flight sensor as described in claim 9, characterized in that, Before the three charge storage and conversion circuits store the background light photoelectric charge, the synchronous photoelectric charge, and the orthogonal photoelectric charge to generate three integrated charge signals, the following steps are also included: Before exposure begins, an anti-charge crosstalk control signal is input, and the anti-charge crosstalk circuit clears the charge in the photoelectric conversion element according to the anti-charge crosstalk control signal; when the anti-charge crosstalk control signal is stopped, exposure begins. Before the three input control selection signals are used to cause the three charge storage and transfer circuits to output the three integrated charge signals, and after the exposure is completed, the following is also included: Stop exposure, input the anti-charge crosstalk control signal, and the anti-charge crosstalk circuit outputs the charge removal function based on the anti-charge crosstalk control signal to clear the charge in the photoelectric conversion element; wherein, the anti-charge crosstalk control signal is input while the three integrated charge signals are output.

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