CN211086592U - Pixel circuit and time-of-flight sensor - Google Patents

Abstract

A pixel circuit and a time-of-flight sensor, the pixel circuit comprising: the photoelectric conversion module is used for receiving the optical signal and converting the optical signal into a certain amount of charges corresponding to the optical energy; the charge storage module is electrically connected with the photoelectric conversion module and used for responding to a first control signal and storing at least part of charges generated by the photoelectric conversion module; and one end of the bypass bleeder module is electrically connected to the photoelectric conversion module, the other end of the bypass bleeder module is grounded, and the bypass bleeder module is used for responding to a second control signal and discharging part of charges generated by the photoelectric conversion module while the charge storage module stores the charges. The detection accuracy of the pixel circuit is improved.

Description

Pixel circuit and time-of-flight sensor

Technical Field

The utility model relates to a sensing technology field especially relates to a pixel circuit and a time of flight sensor.

Background

The Time Of Flight (TOF) method measures the three-dimensional structure or three-dimensional profile Of an object to be measured by using the Time interval between transmission and reception Of a pulse signal from a measuring instrument or the phase generated when a laser beam travels back and forth to the object to be measured once. The TOF measuring instrument can simultaneously obtain a gray image and a distance image, and is widely applied to the fields of somatosensory control, behavior analysis, monitoring, automatic driving, artificial intelligence, machine vision, automatic 3D modeling and the like.

Time-of-flight (TOF) sensors generally include: the device comprises a light source module and a photosensitive module; the light source module is used for emitting pulse detection light with a specific waveband and a specific frequency, the detection light is reflected on the surface of a detected object, and the reflected light is received by the photosensitive module; and the photosensitive module calculates the distance information of the object to be measured according to the time difference or the phase difference between the transmitting light wave and the receiving light wave.

The photosensitive module comprises a pixel array consisting of a plurality of pixels, reflected light is received by pixel units in the pixel array, and each pixel unit converts an optical signal into an electric signal through a pixel circuit. Therefore, the conversion efficiency of the pixel circuit to convert the optical signal into the electric signal has an important influence on the accuracy of the distance detection.

When ambient light is too strong, the charge amount generated by photoelectric conversion in a single pixel exceeds the storage capacity of stored charges, so that pixel points are overexposed.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that a pixel circuit and a time of flight sensor are provided, time of flight sensor's performance is improved.

In order to solve the above problem, an embodiment of the present invention provides a pixel circuit including: the photoelectric conversion module is used for receiving the optical signal and converting the optical signal into a certain amount of charges corresponding to the optical energy; the charge storage module is electrically connected with the photoelectric conversion module and used for responding to a first control signal and storing at least part of charges generated by the photoelectric conversion module; and one end of the bypass bleeder module is electrically connected to the photoelectric conversion module, the other end of the bypass bleeder module is grounded, and the bypass bleeder module is used for responding to a second control signal and discharging part of charges generated by the photoelectric conversion module while the charge storage module stores the charges.

Optionally, the charge storage module includes at least three storage units, which are used for respectively storing at least part of charges generated by the photoelectric conversion module; each storage unit comprises a storage switch and a capacitor, the capacitor is electrically connected to the photoelectric conversion module through the storage switch, and the storage switch responds to a first control signal; and when the storage switch is turned on, the corresponding storage unit stores the charges.

Optionally, the bypass bleeder module includes a bleeder switch, and when the bleeder switch is turned on, the bypass bleeder module performs charge bleeding to bleed off a part of charges generated by the photoelectric conversion module.

Optionally, the bypass bleeding module is further configured to bleed off all invalid charges generated by the photoelectric conversion module when the charge storage module stops charge storage in response to a third control signal.

Optionally, the method further includes: and the invalid charge discharging module is used for responding to a third control signal and discharging invalid charges generated by the photoelectric conversion module when the charge storage module stops charge storage. (repeating with the previous)

Optionally, the bleed current of the bypass bleed-off module under the control of the second control signal is smaller than the bleed current when the invalid charge is bled off under the control of the third control signal.

The technical scheme of the utility model a time of flight sensor is still provided, include: the light source module is used for emitting detection light; a pixel array including a plurality of pixel circuits as described above; and the controller is connected with the pixel array and used for generating a control signal for controlling the pixel circuit.

The utility model discloses a pixel circuit can be at the in-process that carries out the storage to the light charge, to some charges among them release, avoids producing the problem of overexposure among the storage process, improves the accuracy of the detected signal who acquires, and then improves the detection accuracy of the time of flight sensor who adopts this pixel circuit.

Drawings

Fig. 1 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a time-of-flight sensor according to an embodiment of the present invention;

fig. 4 is a schematic flow chart of a distance measuring method of a time-of-flight sensor according to an embodiment of the present invention;

FIG. 5a is a schematic diagram of a charge storage and emission timing sequence according to an embodiment of the present invention;

fig. 5b is a schematic diagram of a charge storage and light emission timing sequence according to an embodiment of the present invention.

Detailed Description

As described in the background art, when ambient light is too strong, the charge amount generated by photoelectric conversion in a single pixel exceeds the storage capacity of stored charges, thereby causing overexposure of a pixel.

The inventor researches and discovers that in the process of distance detection, the detection accuracy is related to the accuracy of the obtained effective electrical signals. By storing and accumulating the electric charges converted from the reflected light, an effective detection signal is obtained. Under the condition of weak ambient light, charges generated by optical signals received by the sensor can be stored and converted into effective detection signals; under the condition of strong ambient light, the charge quantity generated by the optical signal received by the sensor exceeds the storage capacity of the storage device, and the optical signal cannot be completely stored, so that the problem of overexposure is caused, and the detection accuracy is influenced.

Fig. 1 is a schematic diagram of a pixel circuit according to an embodiment of the present invention.

The pixel circuit includes: a photoelectric conversion module 110, a charge storage module 120, and a bypass bleed-off module 130.

The photoelectric conversion module 110 is configured to receive an optical signal and convert the optical signal into a certain amount of charges corresponding to optical energy. In the time-of-flight distance detection process, the optical signal received by the photoelectric conversion module 110 includes ambient light and pulse reflected light after the pulse detection light is reflected by an object.

The photoelectric conversion module 110 includes at least a photodiode, and other auxiliary circuits. The photodiode can convert an optical signal into an electrical signal, and specifically, generate a certain amount of charges corresponding to light energy, where the amount of charges is generally proportional to the light energy, and the conversion ratio is related to the conversion efficiency of the optoelectronic conversion module 110. In fig. 1, the photo-electric conversion module 110 is represented by the photodiode D1. The cathode of the photodiode D1 is connected to the power supply VDD.

The charge storage module 120 is electrically connected to the photoelectric conversion module 110, and is configured to store at least a portion of the charge generated by the photoelectric conversion module 110 in response to a first control signal. Specifically, the charge storage module 120 is electrically connected to the anode of the photodiode D1, and when the photoelectric conversion module 110 generates charges under illumination, the charges are transferred to the charge storage module 120 through a path between the charge storage module 120 and the photoelectric conversion module 110. The charge storage module 120 is configured to store charges, and a signal generated by the stored charge amount is used as a detection signal.

In this embodiment, the charge storage module 120 includes three storage units, namely a storage unit 121, a storage unit 122, and a storage unit 123. Each memory cell includes a memory switch and a capacitor, and the capacitor is electrically connected to the photoelectric conversion module 110 through the memory switch. The memory cell 121 includes a memory switch G1 and a capacitor C1, the memory cell 122 includes a memory switch G2 and a capacitor C2, and the memory cell 123 includes a memory switch G3 and a capacitor C3. In other embodiments, the charge storage module 120 and each memory cell may further include other auxiliary circuits. In other embodiments, the charge storage module 120 may further include more than three charge storage units.

The storage switch is responsive to a first control signal; and when the storage switch is turned on, the corresponding storage unit stores the charges. For example, when the storage switch G1 is controlled to be turned on by a first control signal, the capacitor C1 is connected to the photoelectric conversion module 110, the charges generated by the photoelectric conversion module 110 are transferred to the capacitor C1, and the capacitor C1 is charged, so that the storage of the charges by the storage unit 121 is realized. The on states of the storage switches G1, G2, and G3 are controlled by the first control signal, so that the timing and storage time of storing charges in the memory cells can be controlled. The storage switch at least comprises an element with a switching characteristic, such as a triode, a thyristor or a MOS tube, and can also comprise other auxiliary circuits.

In one embodiment, the first storage unit 121 is used for storing charges generated by the photoelectric conversion module 110 only receiving ambient light; the second storage unit 122 is configured to store charges generated by pulse reflection light and ambient light of the object to be measured after the pulse reflection light is received by the photoelectric conversion module 110 at the first stage; the second storage unit 122 is configured to store charges generated by pulse reflection light and ambient light after the photoelectric conversion module 110 receives the detected object and reflects the detected light in the second stage.

The charge storage capacity of the charge storage module 120 is limited, and when the amount of charge generated by the photoelectric conversion module 110 is too large, the generated charge cannot be stored by the charge storage module 120, so that the generated detection signal cannot accurately reflect the light energy received by the photoelectric conversion module 110. For example, when the light energy is Q1, the amount of charge generated reaches the upper storage limit of the charge storage module 120; when the light energy exceeds Q1, the charge storage module 120 stores the same amount of charge as that generated when the light energy is Q1, and cannot reflect the change of light energy.

In particular, in the second memory cell 122 and the third memory cell 123, since the electric charges stored in the second memory cell 122 and the third memory cell 123 are generated by the ambient light and the pulse reflected light, when the ambient light does not change much, the light energy of the detection light is mainly reflected in the amount of electric charges stored in the second memory cell 122 and the third memory cell 123. When the distance is detected, the distance is measured mainly through the flight time of reflected light;

in one embodiment, the distance is calculated as follows,

wherein G3, G2, and G1 are the amounts of charge received by the third memory cell 123, the second memory cell 122, and the third memory cell 121, respectively.

In the case of a large ambient light intensity, the second storage unit 122 and the third storage unit 123 may not be able to store the charges generated by the pulse reflected light completely during the storage time, so that G2 and G3 are inaccurate, and thus, an overexposure problem is generated, and the detection signal is inaccurate.

In order to solve the problem of overexposure, the pixel circuit according to an embodiment of the present invention further includes the bypass bleeder module 130. The bypass bleeder module 130 is electrically connected to the photoelectric conversion module 110 at one end, and is grounded at the other end, and the bypass bleeder module 130 is configured to respond to a second control signal to discharge a part of the charges generated by the photoelectric conversion module 110 while the charge storage module 120 stores the charges.

When the second control signal S2 controls the bypass bleeding module 130 to establish a conductive path between the photoelectric conversion module 110 and the ground, when a part of the charges accumulated on the photoelectric conversion module 110 is transferred to the charge storage module 120 for storage, a part of the charges will be bled to the ground through the bypass bleeding module 130, so as to avoid an overexposure problem caused by an excessively large amount of charges transferred to the charge storage module 120.

After the part generated on the photoelectric conversion module 110 is discharged by the bypass discharging module 130, the amount of charge stored in the charge storage module 120 is reduced proportionally by the ambient light and the pulse reflected light, and therefore, according to the calculation formula of the detection distance, the calculation result is not affected. However, since the overexposure problem is avoided, the detection signal generated by the amount of charge stored in the charge storage module 120 can be more accurate, and thus, the detection accuracy can be improved.

In this embodiment, the bypass bleeder module 130 includes a bleeder switch GB, and when the bleeder switch GB is turned on, the bypass bleeder module 130 performs charge bleeding. The bleeder switch GB includes at least one of a triode, a thyristor, or a MOS transistor having a switching characteristic or a circuit composed of each element, and may further include other auxiliary circuits. In this embodiment, the bleeder switch GB is a MOS transistor.

The ratio of the amount of charge bled by the bypass bleed off module 130 to the amount of charge stored by the charge storage module 120 is determined by the on-state current of the bypass bleed off module 130 and the charge storage module 120. The current controlling the bleeding is less than the total photocurrent generated by the optical signal conversion. The adjustment of the bleed current can be realized by adjusting the size of the bleed switch GB, for example, the width-to-length ratio of the MOS transistor, or by adjusting the voltage of the second control signal S2 to adjust the on-current of the bleed light GB.

In one embodiment, the on-currents of the memory switches G1, G2, and G3 in each memory cell of the memory module 120 are the same.

The control signals to which the storage switches G1, G2 and G3 and the bleed-off switch GB respond may be generated by a controller of the sensor to control the storage switches G1, G2 and G3 and the bleed-off switch GB according to a certain clock sequence.

The pixel circuit further includes a detection signal obtaining module 140, and the detection signal obtaining module 140 is configured to obtain an electrical signal generated by the charge stored in the charge storage module 120. In this embodiment, the detection signal obtaining module 140 is electrically connected to the charge storage module 120 and is connected to one end of each storage switch G1, G2, G3, which is electrically connected to one end of the photoelectric conversion module 110, and is used for obtaining a voltage signal generated by the charges stored on the capacitor when each storage unit is turned on, and obtaining a detection signal through certain circuit processing. In this embodiment, the detection signal obtaining module 140 includes a MOS transistor M1 and a MOS transistor M2, a gate of the MOS transistor M1 is connected to the charge storage module 120, and a source thereof is connected to a power supply VDD; the source of the MOS transistor M2 is connected to the drain of the MOS transistor M1, the source is used for outputting a detection signal, and the gate is used for being connected to a control signal RD.

Since ambient light is always present, the photoelectric conversion module 110 always generates electric charges, during which invalid electric charges that are not useful for measurement are generated. When the charge storage module 120 does not store the charges, the invalid charges generated by the photoelectric conversion module 110 are accumulated, and once the storage switch of the charge storage module 120 is turned on, the charges accumulated in the photoelectric conversion module 110 generate a transient current, which affects the accuracy of the charge storage module 120 in storing the charges.

In this embodiment, the bypass bleed module 130 of the pixel circuit is further responsive to a third control signal S3 to bleed off invalid charges generated by the photoelectric conversion module 110 when the charge storage module 120 stops charge storage. When the charge storage module 120 stops storing charge, the bleed-off switch GB can be controlled to be turned on by the third control signal S3, so that invalid charge is bled off from the bypass bleed-off module 130. Preferably, the bypass bleeder module 130 of the pixel circuit bleeds off all the invalid charges generated by the photoelectric conversion module 110 when the charge storage module 120 stops the charge storage.

The bleed current of the bypass bleed module 130 under the control of the second control signal S2 may be controlled to be less than the bleed current when the third control signal S3 controls to bleed the reactive charge such that the reactive charge is fully bled off. Specifically, the voltage of the third control signal S3 may be made greater than the voltage of the second control signal S2.

Fig. 2 is a schematic structural diagram of a pixel circuit according to another embodiment of the present invention.

The pixel circuit further includes: an invalid charge draining module 200, having one end electrically connected to the photoelectric conversion module 110 and the other end grounded, for draining the invalid charge generated by the photoelectric conversion module 110 when the charge storage module 120 stops charge storage in response to a third control signal S3'.

Therefore, when the charge storage module 120 stops the charge storage, the invalid charge generated by the photoelectric conversion module 110 can be completely discharged by turning on the invalid charge discharging module 200. In order to improve the charge leakage efficiency of the inactive charge leakage module 200, the inactive charge leakage module 200 may be configured to have a high on-current. In this specific embodiment, the invalid charge draining module 200 includes a draining switch GD, where the draining switch GD at least includes a switching characteristic element such as an MOS transistor, a thyristor, or a triode, and may further include other auxiliary circuits.

In a specific embodiment, the size of the bleed-off switch GD is smaller than that of the bleed-off switch GB, so that the on-current of the bleed-off switch GD is larger than that of the bleed-off switch GB under the same size of control signal; alternatively, the voltage of the third control signal S3' may be made greater than the second control signal S2, so that the on-current of the bleed switch GD is greater than the on-current of the bleed switch GB to ensure that the ineffective charge is fully bled off.

In other specific embodiments, when the bypass bleeder module 130 stops storing the charge in the charge storage module 120, the second control signal S2 may control the charge generated by the photoelectric conversion module 110 to bleed off, but since the on-current of the bypass bleeder module 130 is small, the current may not be fully bled off.

In other embodiments, the inactive charge may be drained simultaneously by the bypass drain module 130 and the inactive charge drain module 200.

The pixel current can discharge part of the charges in the process of storing the photo charges, so that the problem of overexposure in the storage process is avoided, and the accuracy of the obtained detection signal is improved.

Particular embodiments of the present invention also provide a time of flight sensor.

Please refer to fig. 3, which is a schematic structural diagram of a time-of-flight sensor according to an embodiment of the present invention.

The time-of-flight sensor includes: a light source module 310, a pixel array 320, and a controller 330.

The light source module 310 includes a light emitting element, such as a light emitting diode, L ED laser, etc., for emitting detection light, which is modulated pulsed light.

The pixel array 320 includes a plurality of pixel circuits 321, where the pixel circuits 321 include a photoelectric conversion module, a charge storage module, a bypass bleeder module, and the like, and a specific structure of the pixel circuits 321 may refer to the description in the foregoing specific embodiment, which is not repeated herein.

The controller 330 is connected to the pixel array 320, and is configured to generate a control signal for controlling the pixel circuit 321. The controller 330 is further connected to the light source module 310, and is configured to control parameters of the light source module 310, such as a light emitting period and power.

The controller 330 is configured to send the first control signal, the second control signal, and the third control signal to each pixel circuit 321, and the first control signal, the second control signal, and the third control signal received by each pixel circuit 321 are all synchronized, so that the states of charge storage and charge draining of each pixel circuit 321 are all synchronized.

The specific embodiment of the utility model also provides a time of flight range finding method.

Please refer to fig. 4, which is a flowchart illustrating a time-of-flight ranging method according to an embodiment of the present invention.

The time-of-flight ranging method comprises the following steps:

s401: the detection light is emitted toward the object of interest. The detection light is modulated pulsed light.

S402: and receiving a reflected light signal reflected by the object to be measured. The reflected light signal received here includes not only the pulse reflected light generated by the reflection of the detection light by the object to be measured but also the ambient light.

S403: the reflected light signal is converted to a quantity of electrical charges corresponding to the light energy. The optical signal may be converted by a photoelectric conversion element, which may be a photodiode.

S404: storing at least a portion of the charge. By storing the electric charge, a detection signal corresponding to the light energy is generated. In one embodiment, the charges may be stored for three consecutive storage times, respectively, the charges generated by the ambient light and the pulse reflection light in the first stage, and the charges generated by the ambient light and the pulse reflection light in the second stage, so as to generate the detection signals generated by the charges stored for the respective storage times.

S405: when a set bleeding condition is reached, the charge is stored while part of the charge is bled off.

Due to the limited storage capacity of the charge storage process, when the amount of charge generated by photoelectric conversion is too large, the generated charge cannot be stored completely, and therefore, the generated detection signal cannot accurately reflect the received reflected light energy.

The utility model discloses an among the embodiment, in order to avoid above-mentioned problem, can set for a preset condition, when reacing this preset condition, it is right when the electric charge carries out the storage, release partial electric charge wherein, in the reduction storage process of equal proportion, the produced electric charge amount of ambient light, pulse reflection light avoid the storage process, the problem that the electric charge amount overexposed.

The preset conditions comprise that the ambient light intensity is greater than a preset value or the current detection frame is a set frame number. When the ambient light intensity is greater than the preset value, overexposure is easily generated in the storage process, so that partial charges are discharged while the charges are stored. In another embodiment, during the detection process of a specific detection frame, the charge is stored and part of the charge is drained, so that the detection signal with the charge drained can be compared with the detection signal without the charge drained, and the detection signal without the overexposure can be selected as the effective detection signal.

S506: and taking an electric signal generated by the stored charges as an effective detection signal to obtain a detection distance.

In other embodiments, the method further comprises: when the storage of the charge is stopped, the charge is drained. Due to the presence of ambient light, when charge storage is not performed, ineffective charge generated by ambient light conversion is accumulated, and once charge storage is started, the charge previously generated due to ambient light may also be stored, affecting the accuracy of the amount of stored charge. Therefore, when the charge storage is stopped, the ineffective charge due to the ambient light can be entirely discharged.

The bleed-off current for the ineffective charge may be made larger than the current at which the partial charge is bled off in step S405 to ensure that the ineffective charge is fully bled off.

Please refer to fig. 5a and fig. 5b, which are schematic diagrams of charge storage and light emitting timings under two conditions, respectively.

Referring to fig. 5a, in the case of weak background light, no bypass current is discharged. Referring to fig. 2, in a detection frame, the drain switch GD of the invalid charge draining module 200 remains off (corresponding to the low level of the control signal) in the pixel circuit, and is turned on (corresponding to the high level of the control signal) at other times; the bleed switch of the bypass bleed module 130 remains closed (corresponding to a low level of the control signal); the storage switches 120 of the charge storage module 120 are sequentially turned on (corresponding to high levels of the G1, G2, and G3 signals, respectively), and when the storage switch G1 is turned on, the charges generated by the ambient light are stored; when the storage switch G2 is turned on, the charges generated by the ambient light and the pulsed reflected light are stored; when the storage switch G3 is turned on, the charge generated by the ambient light and the pulsed reflected light is stored. Since the ambient light energy is weak at this time, the amount of charge stored in each memory cell does not exceed its storage capacity (corresponding to the area of the signal high-level pulse). All the charges generated by the pulse reflected light can be stored to generate a detection signal, so that the sensitivity of distance detection can be improved.

Referring to fig. 5b, in the case of a large ambient light intensity, the bypass current is discharged. Referring to fig. 2, in a detection frame, the drain switch GD of the invalid charge draining module 200 remains off (corresponding to the low level of the control signal) in the pixel circuit, and is turned on (corresponding to the high level of the control signal) at other times; the bleeder switch of the bypass bleeder module 130 remains open (corresponding to a high level of the control signal) during the charge storage time and remains closed (corresponding to a low level of the control signal) during other times; the storage switches 120 of the charge storage module 120 are sequentially turned on (corresponding to high levels of the G1, G2, and G3 signals, respectively), and when the storage switch G1 is turned on, the charges generated by the ambient light are stored; when the storage switch G2 is turned on, the charges generated by the ambient light and the pulsed reflected light are stored; when the storage switch G3 is turned on, the charge generated by the ambient light and the pulsed reflected light is stored. When the bypass bleeder switch GB is open, part of the ambient light and part of the charge generated by the pulse reflected light will be bled off. Therefore, even when the ambient light energy is strong, the amount of charge stored in each memory cell does not exceed its storage capacity (corresponding to the area of the signal high level pulse). Because the charges generated by the pulse reflected light and the ambient light are discharged in equal proportion, the signal-to-noise ratio of the detection signal is not influenced, and enough charge can be stored and stored, so that the accuracy of distance measurement can be improved on the premise of not reducing the sensitivity of the distance measurement.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims (7)

1. A pixel circuit, comprising:

the photoelectric conversion module is used for receiving the optical signal and converting the optical signal into a certain amount of charges corresponding to the optical energy;

the charge storage module is electrically connected with the photoelectric conversion module and used for responding to a first control signal and storing at least part of charges generated by the photoelectric conversion module;

and one end of the bypass bleeder module is electrically connected to the photoelectric conversion module, the other end of the bypass bleeder module is grounded, and the bypass bleeder module is used for responding to a second control signal and discharging part of charges generated by the photoelectric conversion module while the charge storage module stores the charges.

2. The pixel circuit according to claim 1, wherein the charge storage module comprises at least three storage units for respectively storing at least part of the charges generated by the photoelectric conversion module; each storage unit comprises a storage switch and a capacitor, the capacitor is electrically connected to the photoelectric conversion module through the storage switch, and the storage switch responds to a first control signal; and when the storage switch is turned on, the corresponding storage unit stores the charges.

3. The pixel circuit according to claim 2, wherein the bypass bleeder module comprises a bleeder switch, and when the bleeder switch is turned on, the bypass bleeder module performs charge bleeding to bleed off a part of the charge generated by the photoelectric conversion module.

4. The pixel circuit of claim 1, wherein the bypass bleed module is further configured to bleed an invalid charge generated by the photoelectric conversion module when the charge storage module stops charge storage in response to a third control signal.

5. The pixel circuit according to claim 1, further comprising: and the invalid charge discharging module is used for responding to a third control signal and discharging invalid charges generated by the photoelectric conversion module when the charge storage module stops charge storage.

6. The pixel circuit according to claim 4 or 5, wherein the bleed current of the bypass bleed module under control of the second control signal is smaller than the bleed current when the invalid charge is bled under control of the third control signal.

7. A time-of-flight sensor, comprising:

the light source module is used for emitting detection light;

a pixel array comprising a number of pixel circuits as claimed in any one of claims 1 to 6;

and the controller is connected with the pixel array and used for generating a control signal for controlling the pixel circuit.

Images