CN114879167A

CN114879167A - Pixel circuit, photoelectric signal acquisition method and system and distance measuring sensor

Info

Publication number: CN114879167A
Application number: CN202210490309.8A
Authority: CN
Inventors: 不公告发明人
Original assignee: Sichuan Chuang'an Microelectronics Co ltd
Current assignee: Sichuan Chuang'an Microelectronics Co ltd
Priority date: 2022-05-07
Filing date: 2022-05-07
Publication date: 2022-08-09

Abstract

The invention discloses a pixel circuit, a photoelectric signal acquisition method and system and a ranging sensor, which comprise a global reset circuit and four pixel reading circuits with the same structure, wherein the four pixel reading circuits correspond to four phase intervals in a phase period of modulated infrared light one by one, and the pixel circuit is controlled to finish the simultaneous reading of the four phase signals by adjusting the on-off state of each MOS (metal oxide semiconductor) tube in each pixel reading circuit, so that the purpose that enough phase delay photoelectric signals can be obtained for calculating the distance by reading one frame of pixels is realized.

Description

Pixel circuit, photoelectric signal acquisition method and system and distance measuring sensor

Technical Field

The invention relates to the technical field of photoelectric signal acquisition, in particular to a pixel circuit, a photoelectric signal acquisition method and system and a distance measuring sensor.

Background

At present, the distance measurement sensors in the market mainly measure distance based on two types of methods, one type is dTOF (direct Time-of-Flight, which directly measures optical Flight Time), and the other type is ietf (indirect Time-of-Flight, which indirectly measures optical Flight Time).

Where iTOF is an indirect measure of the time of flight of light by measuring the phase shift. The core of the iTOF module comprises a transmitting end and a receiving end. The emitting end is usually a VCSEL laser, and is mainly responsible for emitting modulated infrared light of a specific frequency; the receiving end is usually an image sensor, receives the reflected light within the exposure time and performs photoelectric conversion, reads out data after the exposure is finished, transmits the data to the computing unit after analog-to-digital conversion, and calculates the phase offset of each pixel by the computing unit.

The calculation unit calculates a phase offset using the four phase-delayed sampling signals. The phases of the four sampling signals may be arranged in sequence, and the phase difference between adjacent phases is 90 °, for example, the phases of the four sampling signals may be 0 °, 90 °, 180 °, and 270 °.

For one frame of image, one or two of the four phase signals may typically be acquired. If only one of the four phase signals can be acquired from one frame of image, the four frames of image are required to be read to acquire enough information for calculating the distance; if two phase signals are acquired from one frame of image, two frames of images need to be read to obtain enough information for calculating the distance. Therefore, the following disadvantages exist in acquiring the phase signal for calculating the distance using the prior art:

firstly, the light source transmitting end needs to transmit modulated infrared light for multiple times, which can cause the power consumption of the transmitting end to increase;

secondly, for a moving object, signal distortion is easy to occur in a multi-frame reading signal, so that the precision of ranging is reduced.

In view of this, the present application is specifically made.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: collecting phase signals for calculating distance using the prior art not only increases the power consumption of the transmitting end, but also affects the ranging accuracy. The pixel circuit, the photoelectric signal acquisition method and system and the ranging sensor can acquire a plurality of phase-delayed photoelectric signals meeting the requirement of distance calculation only by reading one frame of pixels, so that the increase of power consumption of a transmitting end caused by reading operation of multi-frame pixels is avoided, the problem of signal distortion easily caused by reading multi-frame signals of a moving object is solved, and the ranging precision is improved.

The invention is realized by the following technical scheme:

on the one hand, the method comprises the following steps of,

the present invention provides a pixel circuit, including: the infrared light modulation infrared light phase modulation circuit comprises a global reset circuit and a plurality of pixel reading circuits with the same structure, wherein the pixel reading circuits correspond to a plurality of phase intervals in a phase period of modulated infrared light one by one;

the global reset circuit includes: a global reset MOS tube and a photodiode; the drain electrode of the global reset MOS tube is connected with a power supply, and the source electrode of the global reset MOS tube is connected with the cathode of the photodiode;

the pixel reading circuit includes: the device comprises a transmission control MOS tube, an FD reset MOS tube, a source electrode following MOS tube, a pixel selection MOS tube, a conversion gain control MOS tube, a gain conversion capacitor and a charge storage capacitor; the source electrode of the transmission control MOS tube is connected with the cathode of the photodiode and the source electrode of the global reset MOS tube, and the drain electrode of the transmission control MOS tube is respectively connected with one end of the charge storage capacitor, the source electrode of the FD reset MOS tube, the grid electrode of the source electrode following MOS tube and the drain electrode of the conversion gain control MOS tube; the other end of the charge storage capacitor is grounded; the drain electrode of the FD reset MOS tube is connected with the power supply; the source electrode of the conversion gain control MOS tube is connected with one end of the gain conversion capacitor; the other end of the gain conversion capacitor is grounded; the drain electrode of the source electrode following MOS tube is connected with the power supply, and the source electrode of the source electrode following MOS tube is connected with the drain electrode of the pixel selection MOS tube; the source electrode of the pixel selection MOS tube is connected with a pixel output signal line;

the grid of each FD reset MOS tube is connected with an Rx control line, the grid of each pixel selection MOS tube is connected with an Sx control line, and the grid of each conversion gain control MOS tube is connected with a DCG control line.

As a further description of the present invention,

the connection relation between the grid electrode of the FD reset MOS tube and the Rx control line comprises: the grid electrodes of the FD reset MOS tubes are connected with an Rx control line together, and the grid electrode of one FD reset MOS tube is connected with an Rx control line;

the connection relation between the grid electrode of the pixel selection MOS tube and the Sx control line comprises the following steps: the grid electrodes of the pixel selection MOS tubes are connected with an Sx control line, and the grid electrode of one pixel selection MOS tube is connected with an Sx control line;

the connection relation between the grid of the conversion gain control MOS tube and the DCG control line comprises the following steps: the grid electrodes of the conversion gain control MOS tubes are connected with a DCG control line together, and the grid electrode of one conversion gain control MOS tube is connected with a DCD control line.

As a further description of the invention, the pixel circuit supports high/low dual conversion gain.

On the other hand, in the case of a liquid,

the invention provides a photoelectric signal acquisition method, which is based on the pixel circuit of any one of claims 1-3 to execute the following steps:

s1: before exposure, the pixel circuit is globally reset by adopting a mode of adjusting the on-off state of each MOS tube;

s2: during exposure, the following steps are performed in each phase period of the modulated infrared light:

for each phase interval within the phase cycle, performing S21 and S22:

s21: adjusting the switching state of each transmission control MOS tube according to the current phase interval of the modulated infrared light, so that the global reset circuit is only conducted with the pixel reading circuit corresponding to the current phase interval;

s22: adjusting the on-off state of a conversion gain control MOS tube in a pixel reading circuit corresponding to the current phase interval according to the attribute of the conversion gain; controlling the on-off state of the MOS tube according to the adjusted conversion gain, and transmitting the charges in the photodiode to a corresponding capacitor;

s3: after exposure is finished, sequentially carrying out image signal sampling, FD resetting and reset signal sampling on each pixel in a frame of pixels, and reading out image signal acquisition voltage and reset voltage corresponding to each pixel reading circuit;

s4: and respectively making a difference between the reset voltage of each pixel reading circuit and the image signal acquisition voltage, and taking the difference value as the photoelectric signal of the corresponding phase interval.

As a further description of the present invention,

the S1 includes the steps of:

s11: setting the grid of the global reset MOS tube to be high level, setting the grid of each transmission control MOS tube to be low level, and clearing the electric charge in the photodiode;

s12: setting the grid of each FD reset MOS tube to be high level, setting the grid of each pixel selection MOS tube to be low level, setting the grid of each conversion gain control MOS tube to be high level, and clearing the charges in each charge storage capacitor and each gain conversion capacitor;

s13: and setting the grid electrode of the global reset MOS tube to be at a low level, and setting the grid electrode of each FD reset MOS tube to be at a low level.

As a further description of the present invention,

the S21 includes the steps of:

when the modulated infrared light is in a phase interval of 0-90 degrees, setting the grid of a transmission control MOS tube in the pixel reading circuit corresponding to the phase interval of 0-90 degrees to be at a high level, and setting the grids of the transmission control MOS tubes in the other pixel reading circuits to be at a low level;

when the modulated infrared light is in a phase interval of 90-180 degrees, setting the grid of a transmission control MOS tube in a pixel reading circuit corresponding to the phase interval of 90-180 degrees to be at a high level, and setting the grids of the transmission control MOS tubes in the other pixel reading circuits to be at a low level;

when the modulated infrared light is in a phase interval of 180 degrees to 270 degrees, setting the grid of a transmission control MOS tube in a pixel reading circuit corresponding to the phase interval of 180 degrees to 270 degrees to be at a high level, and setting the grids of the transmission control MOS tubes in the other pixel reading circuits to be at a low level;

when the modulated infrared light is in a 270-360 degree phase interval, setting the grid of the transmission control MOS tube in the pixel reading circuit corresponding to the 270-360 degree phase interval as a high level, and setting the grids of the transmission control MOS tubes in the other pixel reading circuits as a low level.

As a further description of the present invention,

the S22 includes the steps of:

when the conversion gain is low, the following steps are executed to the pixel reading circuit corresponding to the current phase interval:

keeping the grid of the conversion gain control MOS tube at a high level, and simultaneously transmitting the charges generated in the photodiode to the charge storage capacitor and the gain conversion capacitor;

when the conversion gain is high, the following steps are executed to the pixel reading circuit corresponding to the current phase interval:

and setting the grid of the conversion gain control MOS tube to be at low level, and only transmitting the charges generated in the photodiode to the charge storage capacitor.

As a further description of the present invention,

the image signal sampling comprises the steps of:

setting the grid of each pixel selection MOS tube to be high level, setting the grid of each FD reset MOS tube to be low level, and respectively reading out corresponding image signal acquisition voltage from the output of each pixel reading circuit;

the reset of the FD comprises the steps of:

setting the grid of each FD reset MOS tube to be high level;

when the conversion gain is low, setting the grid electrode of each conversion gain control MOS tube to be high level, clearing the charges in each charge storage capacitor and each gain conversion capacitor, and then setting the grid electrode of each FD reset MOS tube to be low level;

when the conversion gain is high, setting the grid electrode of each conversion gain control MOS tube to be at a low level, clearing the charges in each charge storage capacitor and each gain conversion capacitor, and then setting the grid electrode of each FD reset MOS tube to be at a low level;

the reset signal sampling comprises the following steps:

the corresponding reset signal is read out from the output of each pixel reading circuit, and then the grid of each pixel selection MOS tube is set to be low level.

In yet another aspect of the present invention,

the invention provides a photoelectric signal acquisition system, comprising:

a pixel circuit module for integrating the pixel circuit of any one of claims 1-3;

the global reset module is used for adjusting the switching state of each MOS tube in the pixel circuit before exposure and carrying out global reset on the pixel circuit;

the circuit adjusting module is used for adjusting the switching state of each transmission control MOS tube according to the current phase interval of the modulated infrared light in each phase interval of each phase period of the modulated infrared light during exposure, so that the global reset circuit is only conducted with the pixel reading circuit corresponding to the current phase interval; the switching state of a conversion gain control MOS tube in the pixel reading circuit corresponding to the current phase interval is adjusted according to the attribute of the conversion gain, the switching state of the MOS tube is controlled according to the adjusted conversion gain, and the charge in the photodiode is transmitted to a corresponding capacitor;

the signal reading module is used for sequentially carrying out image signal sampling, FD resetting and reset signal sampling on each pixel in a frame of pixels after exposure is finished, and reading out image signal acquisition voltage and reset voltage corresponding to each pixel reading circuit;

and the numerical value calculation module is used for respectively making a difference between the reset voltage of each pixel reading circuit and the image signal acquisition voltage, and taking the difference value as the photoelectric signal of the corresponding phase interval.

As a further description of the present invention,

the global reset module comprises:

the first reset unit is used for setting the grid electrode of the global reset MOS tube to be at a high level, setting the grid electrode of each transmission control MOS tube to be at a low level and clearing electric charges in the photodiode;

the second reset unit is used for setting the grid of each FD reset MOS tube to be at a high level, setting the grid of each pixel selection MOS tube to be at a low level, setting the grid of each conversion gain control MOS tube to be at a high level, and clearing the charges in each charge storage capacitor and each gain conversion capacitor;

and the third reset unit is used for setting the grid electrode of the global reset MOS tube to be at a low level and setting the grid electrode of each FD reset MOS tube to be at a low level.

As a further description of the present invention,

the circuit adjustment module includes:

the phase interval detection unit is used for detecting the current phase interval where the modulated infrared light is located and sending the detection result to the pixel reading circuit regulation unit; the detection result comprises: the modulated infrared light is in a phase interval of 0-90 degrees, the modulated infrared light is in a phase interval of 90-180 degrees, the modulated infrared light is in a phase interval of 180-270 degrees, and the modulated infrared light is in a phase interval of 270-360 degrees;

the pixel reading circuit adjusting unit is used for setting the grid electrode of the transmission control MOS tube in the corresponding pixel reading circuit to be high level and setting the grid electrodes of the transmission control MOS tubes in the other pixel reading circuits to be low level according to the detection result;

the conversion gain attribute judging unit is used for judging the conversion gain attribute of the current pixel circuit and sending the judgment result to the charge transmission control unit; the judgment result comprises: low conversion gain and high conversion gain;

the charge transfer control unit is used for keeping the grid electrode of the conversion gain control MOS tube at a high level when the conversion gain is low, and simultaneously transferring the charges generated in the photodiode to the charge storage capacitor and the gain conversion capacitor; the grid electrode of the conversion gain control MOS tube is set to be low level when the conversion gain is high, and the electric charge generated in the photodiode is only transmitted to the electric charge storage capacitor.

As a further description of the present invention,

the signal reading module includes:

the image signal sampling unit is used for setting the grid of each pixel selection MOS tube to be at a high level, setting the grid of each FD reset MOS tube to be at a low level, and respectively reading out corresponding image signal acquisition voltage from the output of each pixel reading circuit;

the FD reset unit is used for setting the grid of each FD reset MOS tube to be a high level; when the conversion gain is low, setting the grid electrode of each conversion gain control MOS tube to be high level, clearing the charges in each charge storage capacitor and each gain conversion capacitor, and setting the grid electrode of each FD reset MOS tube to be low level; when the conversion gain is high, setting the grid electrode of each conversion gain control MOS tube to be at a low level, clearing the charges in each charge storage capacitor and each gain conversion capacitor, and setting the grid electrode of each FD reset MOS tube to be at a low level;

and the reset signal sampling unit is used for respectively reading out corresponding reset signals from the output of each pixel reading circuit and setting the grid of each pixel selection MOS tube to be at a low level.

In yet another aspect of the present invention,

the present invention provides a ranging sensor, comprising: modulating an infrared light transmitting end and a reflected light receiving end;

the reflected light receiving end includes: the photoelectric signal collector, the analog-to-digital converter and the calculator are connected in sequence;

the photoelectric collector comprises: the circuit module and the data reading module;

the circuit module is integrated with a pixel circuit as claimed in any one of claims 1 to 3;

the data reading module is used for reading out the photoelectric signals output by the pixel circuits.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. according to the pixel circuit provided by the embodiment of the invention, a plurality of parallel pixel reading circuit structures are designed, and are respectively in one-to-one correspondence with a plurality of phase intervals for modulating infrared light, a plurality of phase signals can be simultaneously read and stored from one frame of image, so that enough phase delay photoelectric signals can be obtained for calculating the distance by reading one frame of pixel, and compared with the prior art, the power consumption increase caused by the fact that a transmitting end needs to transmit modulated infrared light for multiple times due to reading of multiple frames of pixels can be avoided;

2. according to the pixel circuit provided by the embodiment of the invention, as the pixel circuit can read and store a plurality of phase signals simultaneously, reading for a plurality of frames of signals of a moving object is not required, the continuity of signal reading can be ensured, the signal distortion problem is avoided, and the distance measurement precision is further improved;

3. the method and the system for acquiring the photoelectric signals are based on the pixel circuit, so that a plurality of phase signals can be read and read simultaneously, and the reading speed is obviously improved;

4. according to the ranging sensor provided by the embodiment of the invention, the pixel circuit is arranged in the receiving end of the ranging sensor, so that the ranging sensor has the advantages of low power consumption, high precision and high speed.

Drawings

In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort.

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

fig. 2 is a timing diagram for reading out a frame of pixels based on the pixel circuit structure of fig. 1 according to embodiment 2 of the present invention;

fig. 3 is a schematic structural diagram of a photoelectric acquisition system provided in embodiment 3 of the present invention;

fig. 4 is a schematic diagram of a ranging sensor structure and a working principle provided in embodiment 4 of the present invention.

Reference numbers and corresponding part names in the drawings:

1-a global reset circuit, 2-a first pixel reading circuit, 3-a second pixel reading circuit, 4-a third pixel reading circuit, 5-a fourth pixel reading circuit, 6-a modulated infrared light emitting end, 7-a reflected light receiving end, 71-a photoelectric signal collector, 72-an analog-to-digital converter, 73-a calculator, 711-a circuit module and 712-a data reading module.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.

Example 1

The method aims at the problems that an existing iTOF ranging sensor can only acquire one or two phase signals from one frame of image generally, and further cannot meet the requirement of the iTOF ranging sensor on the phase signals when phase deviation is calculated, and a plurality of frames of images are required to be read to acquire enough information for calculating distance, so that power consumption of a transmitting end is increased and ranging accuracy is reduced. The embodiment provides a pixel circuit aiming at the problems, and aims to realize simultaneous reading and storage of a plurality of phase-delayed photoelectric signals, so that the increase of power consumption caused by the fact that a transmitting end needs to transmit modulated infrared light for a plurality of times due to the fact that reading is carried out for a plurality of times is avoided, and the problem that signal distortion is easy to occur to a moving object due to multi-frame reading is solved.

The pixel circuit provided by the embodiment is mainly used for meeting the requirement of the ietf ranging sensor on the number of phase-delayed sampling signals, that is, the calculating unit of the ietf ranging sensor usually calculates the phase offset by using four phase-delayed sampling signals. The phases of the four sampling signals are arranged in sequence, and the phase difference between adjacent phases is 90 °, for example, the phases of the four sampling signals are 0 °, 90 °, 180 °, and 270 °, respectively, the four phases are located at the start positions (0 ° -90 °, 90 ° -180 °, 180 ° -270 °, and 270 ° -360 °) of four phase intervals having the same size, and the four phase intervals constitute one phase cycle.

In contrast, the pixel circuit provided in this embodiment is composed of a global reset circuit 1, a first pixel reading circuit 2, a second pixel reading circuit 3, a third pixel reading circuit 4, and a fourth pixel reading circuit 5, and the first pixel reading circuit 2, the second pixel reading circuit 3, the third pixel reading circuit 4, and the fourth pixel reading circuit 5 have the same circuit structure. The first pixel reading circuit 2 corresponds to a phase interval of 0-90 °, the second pixel reading circuit 3 corresponds to a phase interval of 90-180 °, the third pixel reading circuit 4 corresponds to a phase interval of 180-270 °, and the fourth pixel reading circuit 5 corresponds to a phase interval of 270-360 °.

With reference to fig. 1, a specific circuit configuration of each part of the pixel circuit will be described in detail below:

global reset circuit 1:

the infrared modulation infrared light source comprises a photodiode PD and a global reset MOS tube MN00, wherein the photodiode PD is used for receiving modulated infrared light emitted by an emitting end and generating electric charges after the modulated infrared light passes through reflected light of a target object, the drain electrode of the global reset MOS tube MN00 is connected with a power supply VDD, and the source electrode of the global reset MOS tube MN00 is connected with the cathode of the photodiode PD.

First pixel read current 2:

the pixel selection MOS transistor comprises a transmission control MOS transistor MN10, an FD reset MOS transistor MN11, a source electrode following MOS transistor MN12, a pixel selection MOS transistor MN13, a conversion gain control MOS transistor MN14, a capacitance C11 for conversion gain and a charge storage capacitance C10.

The source electrode of the transmission control MOS tube MN10 is connected with the cathode of the photodiode PD and the source electrode of the global reset MOS tube MN 00; the drain of the transmission control MOS tube MN10 is connected with one end of a charge storage capacitor C10, the source of an FD reset MOS tube MN11, the gate of a source following MOS tube MN12 and the drain of a conversion gain control MOS tube MN 14; the other end of the charge storage capacitor C10 is grounded; the drain electrode of the FD reset MOS tube MN11 is connected with a power supply VDD; the source electrode of the conversion gain control MOS tube MN14 is connected with the corresponding gain conversion capacitor C11, and the other end of the gain conversion capacitor C11 is grounded; the drain electrode of the source electrode following MOS tube MN12 is connected with a power supply VDD; the source electrode of the source electrode following MOS tube MN12 is connected with the drain electrode of the pixel selection MOS tube MN 13; the source of the pixel selection MOS transistor MN13 is connected to the pixel output signal line VpixA for outputting the pixel signal of the first pixel reading circuit 2.

Since the circuit structures of the first pixel reading circuit 2, the second pixel reading circuit 3, the third pixel reading circuit 4 and the fourth pixel reading circuit 5 are the same, details are not repeated here, and only the labels of the MOS transistors, the charge storage capacitors and the gain conversion capacitors in the pixel reading circuits are described as follows:

of the second pixel reading circuit 3, the third pixel reading circuit 4 and the fourth pixel reading circuit 5,

the transmission control MOS tubes are respectively marked as: MN20, MN30 and MN 40;

the FD reset MOS tubes are respectively marked as: MN21, MN31 and MN 41;

the source-level following MOS tubes are respectively marked as: MN22, MN32 and MN 42;

the pixel selection MOS tubes are respectively marked as: MN23, MN33, and MN 43;

the conversion gain control MOS tubes are respectively marked as: MN24, MN34 and MN 44;

the charge storage capacitors are labeled: c20, C30, and C40;

the gain conversion capacitances are labeled: c21, C31, and C41.

It is further to be noted that,

(1) in the first pixel reading circuit 2, the second pixel reading circuit 3, the third pixel reading circuit 4 and the fourth pixel reading circuit 5, each FD reset MOS transistor MN11, MN21, MN31 and MN41 may be connected together and controlled by one control signal line Rx, or may be controlled by four different control signal lines Rx respectively according to the driving capability; the grids of the pixel selection MOS tubes MN13, MN23, MN33 and MN43 are also the same, and can be connected together and controlled by one control signal line Sx or respectively controlled by four different control signal lines Sx; the gates of the conversion gain control MOS transistors MN14, MN24, MN34, and MN44 are also the same, and may be connected together and controlled by one control signal line DCG, or may be controlled by four different control signal lines DCG.

(2) The pixel circuit structure proposed in this embodiment supports high/low dual conversion gain. When the conversion gain is high, the grid DCG of each conversion gain control MOS tube MN14, MN24, MN34 and MN44 is set to be at low level; at the time of low conversion gain, the gates DCG of the conversion gain control MOS transistors MN14, MN24, MN34, and MN44 are kept at a high level.

Fig. 1 is a schematic circuit diagram of the pixel circuit.

Because the first photoelectric reading circuit, the second photoelectric reading circuit, the third photoelectric reading circuit and the fourth photoelectric reading circuit respectively correspond to the four phase intervals for modulating infrared light one by one, four phase signals can be simultaneously read and stored from a frame of image, so that enough phase delay photoelectric signals can be obtained for calculating the distance by only reading one frame of pixel, and compared with the prior art, the power consumption increase of a transmitting end caused by reading operation of multiple frames of pixels can be avoided; and because the pixel circuit can realize the simultaneous reading and storage of four phase signals, reading of multi-frame signals of a moving object is not required to be divided into a plurality of times, the continuity of signal reading can be ensured, the problem of signal distortion is avoided, and the ranging precision and the data reading speed are further improved.

Example 2

This embodiment provides a method for acquiring a photo signal, which reads out a photo signal of a frame of pixels by performing timing control on a pixel circuit based on the pixel circuit of embodiment 1, and further describes an operating principle and a process of the pixel circuit of embodiment 1.

In this embodiment, a readout timing of pixels of one frame is proposed based on the pixel circuit described in embodiment 1, and as shown in fig. 2, the readout timing is divided into a global reset period, an exposure period, and a signal readout period. The light wave emitted by the emitting end is sine modulated infrared light (periodic continuous wave); the grid end of the MOS tube is at high level, which indicates that the MOS tube is in an opening state; the grid end of the MOS tube is at low level, which indicates that the MOS tube is in a closed state.

Corresponding to the readout timing sequence of fig. 2, the photoelectric signal acquisition method includes the steps of:

and step 1, in the global reset period (before exposure), the pixel circuit is reset globally by adjusting the on-off state of each MOS tube. The method is realized by the following steps:

(1) setting the grid Ox of the global reset MOS tube MN00 to be high level, setting the grids TxA, TxB, TxC and TxD of each transmission control MOS tube MN10, MN20, MN30 and MN40 to be low level, and clearing the electric charge in the photodiode PD;

(2) the gate Rx of each FD reset MOS transistor MN11, MN21, MN31, and MN41 is set to high, the gate Sx of each pixel selection MOS transistor MN13, MN23, MN33, and MN43 is set to low, the gate DCG of each conversion gain control MOS transistor MN14, MN24, MN34, and MN44 is set to high, and the charges in each charge storage capacitor C10, C20, C30, and C40, and each conversion gain capacitor C11, C21, C31, and C41 are erased.

(3) After the charge removal is completed, the gate Ox of the global reset MOS transistor MN00 is set to a low level, and the gates Rx of the FD reset MOS transistors MN11, MN21, MN31, and MN41 are set to a low level.

And step 2, entering a pixel exposure period. During the pixel exposure period, the emitting terminal starts to continuously emit modulated infrared light (periodic continuous wave), and the gate terminals of all the MOS transistors except the respective transfer control MOS transistors MN10, MN20, MN30, and 40 are kept in the state at the end of the global reset period.

During the exposure period, the following steps are executed in each phase period of the modulated infrared light:

for each phase interval within the phase cycle, performing S21 and S22:

s22: adjusting the on-off state of a conversion gain control MOS tube in a pixel reading circuit corresponding to the current phase interval according to the attribute of the conversion gain; and controlling the switching state of the MOS tube according to the adjusted conversion gain, and transmitting the charges in the photodiode to a corresponding capacitor.

Wherein the content of the first and second substances,

s21 specifically includes:

when the modulated infrared light is in a phase interval of 0-90 degrees, setting the grid terminal TxA of a transmission control MOS tube MN10 in the first pixel reading circuit to be at a high level; when the modulated infrared light is out of the phase interval of 0-90 degrees, setting the grid terminal TxA of a transmission control MOS tube MN10 in the first pixel reading circuit to be at a low level;

when the modulated infrared light is in a phase interval of 90-180 degrees, setting the grid terminal TxB of a transmission control MOS tube MN20 in the second pixel reading circuit to be at a high level; when the modulated infrared light is out of the phase interval of 90-180 degrees, setting the grid terminal TxB of a transmission control MOS tube MN20 in the second pixel reading circuit to be at a low level;

when the modulated infrared light is in a phase interval of 180-270 degrees, setting the grid terminal TxC of a transmission control MOS tube MN30 in the third pixel reading circuit to be at a high level; when the modulated infrared light is out of the phase interval of 180 degrees to 270 degrees, setting the grid terminal TxC of a transmission control MOS tube MN30 in the third pixel reading circuit to be at a low level;

when the modulated infrared light is in a phase interval of 270-360 degrees, setting the grid terminal TxD of a transmission control MOS tube MN40 in the fourth pixel reading circuit to be at a high level; when the modulated infrared light is out of the 270-360 ° phase interval, the gate terminal TxD of the transmission control MOS transistor MN40 in the fourth pixel reading circuit is set to a low level.

S22 includes the steps of:

(1) when the conversion gain is low, the following steps are executed to the pixel reading circuit corresponding to the current phase interval:

and setting the grid of the conversion gain control MOS tube to be at low level, and only transmitting the charges generated in the photodiode to the charge storage capacitor. Namely: at the time of low conversion gain, the gain of the converter,

if the modulated infrared light is in a phase interval of 0-90 degrees, the charges generated in the photodiode PD are transmitted to the charge storage capacitor C10 and the gain conversion capacitor C11 in the first pixel reading circuit;

if the modulated infrared light is in a phase interval of 90-180 degrees, the charges generated in the photodiode PD are transmitted to the charge storage capacitor C20 and the gain conversion capacitor C21 in the second pixel reading circuit;

if the modulated infrared light is in a phase interval of 180-270 °, the charges generated in the photodiode PD are transferred to the charge storage capacitor C30 and the gain conversion capacitor C31 in the third pixel reading circuit;

if the modulated infrared light is in the phase interval of 270 ° to 360 °, the charges generated in the photodiode PD are transferred to the charge storage capacitor C40 and the gain conversion capacitor C41 in the fourth pixel reading circuit.

(2) When the conversion gain is high, the following steps are executed to the pixel reading circuit corresponding to the current phase interval:

and setting the grid of the conversion gain control MOS tube to be at low level, and only transmitting the charges generated in the photodiode to the charge storage capacitor. Namely: at the time of a high conversion gain, the gain is high,

if the modulated infrared light is in a phase interval of 0-90 degrees, the charge generated in the photodiode PD is transferred to a charge storage capacitor C10 in the first pixel reading circuit;

if the modulated infrared light is in a phase interval of 90-180 degrees, the charge generated in the photodiode PD is transferred to a charge storage capacitor C20 in the second pixel reading circuit;

if the modulated infrared light is in the 180-270 ° phase interval, the charge generated in the photodiode PD is transferred to the charge storage capacitor C30 in the third pixel reading circuit;

if the modulated infrared light is in the phase interval of 270 ° to 360 °, the charge generated in the photodiode PD is transferred to the charge storage capacitor C40 in the fourth pixel reading circuit.

In the above, in one phase period of one frame of pixels, the switching state of each transmission control MOS transistor is adjusted according to the current phase interval in which the modulated infrared light is located, so that the global reset circuit is only turned on with the pixel reading circuit corresponding to the current phase interval. And in the whole process of reading the signals of one frame of pixels, the grid terminals TxA, TxB, TxC and TxD of the transmission control MOS tubes MN10, MN20, MN30 and MN40 are circularly put at high level timing.

And 3, after exposure is finished, sequentially carrying out image signal sampling, FD resetting and reset signal sampling on each pixel in a frame of pixels, and reading out image signal acquisition voltage and reset voltage corresponding to each pixel reading circuit.

First, in the image signal sampling, the gate Sx of each of the pixel selection MOS transistors MN13, MN23, MN33, and MN43 is set to a high level, and the gate Rx of each of the FD reset MOS transistors MN11, MN21, MN31, and MN41 is set to a low level. At this time, the first pixel reading circuit, the second pixel reading circuit, the third pixel reading circuit, and the fourth pixel reading circuit output signals VpixA, VpixB, VpixC, and VpixD, respectively; thereby, the image signal collection voltage values Ss1, Ss2, Ss3, and Ss4 of the respective pixel reading circuits can be read out, respectively;

then, in the FD reset stage, the gates Rx of the FD reset MOS transistors MN11, MN21, MN31, and MN41 are set to high level; when the conversion gain is high, the gates DCG of the conversion gain control MOS transistors MN14, MN24, MN34, and MN44 are set to a high level. The charges stored in the charge storage capacitances C10, C20, C30, and C40 in the first pixel reading circuit, the second pixel reading circuit, the third pixel reading circuit, and the fourth pixel reading circuit, and the gain conversion capacitances C11, C21, C31, and C41 are cleared. After the charge is cleared, the gates Rx of the FD reset MOS transistors MN11, MN21, MN31, and 41 are set to low, and when the conversion gain is high, the gates DCG of the conversion gain control MOS transistors MN14, 24, 34, and 44 need to be set to low.

After the FD reset is finished, the reset signal is sampled. The readout service voltage values Rs1, Rs2, Rs3, and Rs4 may correspond to signals VpixA, VpixB, VpixC, and VpixD output from the first pixel reading circuit, the second pixel reading circuit, the third pixel reading circuit, and the fourth pixel reading circuit, respectively.

After the reset signal sampling is finished, the gates Sx of the pixel selection MOS transistors MN13, MN23, MN33, and MN43 are set to a low level.

And 4, step 4: and respectively making a difference between the reset voltage of each pixel reading circuit and the image signal acquisition voltage, and taking the difference value as the photoelectric signal of the corresponding phase interval. In the finally read four phases, the photoelectric signal with the phase interval of 0-90 degrees is Rs1-Ss 1; the photoelectric signal with the phase interval of 90-180 degrees is Rs2-Ss 2; the photoelectric signal with the phase interval of 180-270 degrees is Rs3-Ss 3; the photoelectric signal with the phase interval of 270-360 degrees is Rs4-Ss 4.

After the above steps are performed, the pixel data read out in one frame includes four sampling signals with phase delay, and the phase shift of each pixel can be directly calculated, so that the distance of the target object can be calculated. Compared with the prior art, the method has the advantage that the reading speed is obviously increased.

Example 3

This embodiment proposes a photoelectric acquisition system corresponding to the photoelectric acquisition method of embodiment 2, for performing the photoelectric acquisition method given in embodiment 2. The system is also based on the pixel circuit of embodiment 1, and its structure is shown in fig. 3, including:

a pixel circuit module for integrating the pixel circuit described in embodiment 1;

Wherein the content of the first and second substances,

the global reset module comprises:

The circuit adjustment module includes:

the phase interval detection unit is used for detecting the current phase interval where the modulated infrared light is located and sending the detection result to the pixel reading circuit adjusting unit; the detection result comprises: the modulated infrared light is in a phase interval of 0-90 degrees, the modulated infrared light is in a phase interval of 90-180 degrees, the modulated infrared light is in a phase interval of 180-270 degrees, and the modulated infrared light is in a phase interval of 270-360 degrees;

The signal reading module comprises:

Example 4

The present embodiment provides a ranging sensor, including: modulating an infrared light transmitting end 6 and a reflected light receiving end 7;

the reflected light receiving end 7 includes: a photoelectric signal collector 71, an analog-to-digital converter 72 and a calculator 73 which are connected in sequence;

the photoelectric collector comprises: a circuit module 711 and a data reading module 712;

the circuit module 711 integrates the pixel circuit according to any of claims 1 to 3;

the data reading module 712 is used for reading out the photoelectric signal output by the pixel circuit.

The receiving end of the ranging sensor is internally provided with the pixel circuit described in embodiment 1, so that the ranging sensor has the advantages of low power consumption, high precision and high speed compared with the conventional ranging sensor.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A pixel circuit, comprising: the infrared light modulation infrared light phase modulation circuit comprises a global reset circuit and a plurality of pixel reading circuits with the same structure, wherein the pixel reading circuits correspond to a plurality of phase intervals in a phase period of modulated infrared light one by one;

2. A pixel circuit according to claim 1,

3. The pixel circuit according to claim 1, wherein the pixel circuit supports high/low dual conversion gain.

4. A method for collecting an optoelectronic signal, wherein the following steps are performed based on the pixel circuit of any one of claims 1 to 3:

for each phase interval within the phase cycle, performing S21 and S22:

5. An optoelectronic signal collecting method as claimed in claim 4, wherein said S1 includes the following steps:

6. An optoelectronic signal collecting method as claimed in claim 4, wherein said S21 includes the following steps:

7. An optoelectronic signal collecting method as claimed in claim 4, wherein said S22 includes the following steps:

8. An optoelectronic signal collection method as claimed in claim 4,

the image signal sampling comprises the steps of:

the reset of the FD comprises the steps of:

setting the grid of each FD reset MOS tube to be high level;

the reset signal sampling comprises the following steps:

9. An optoelectronic signal acquisition system, comprising:

10. A ranging sensor, comprising: modulating an infrared light transmitting end and a reflected light receiving end;