CN112805994A

CN112805994A - Image sensor and imaging device equipped with image sensor

Info

Publication number: CN112805994A
Application number: CN202080005237.2A
Authority: CN
Inventors: 徐泽; 肖�琳; 周雪梅
Original assignee: SZ DJI Technology Co Ltd
Current assignee: SZ DJI Technology Co Ltd
Priority date: 2020-04-16
Filing date: 2020-04-16
Publication date: 2021-05-14
Also published as: WO2021208043A1

Abstract

The present specification discloses an image sensor and an imaging device equipped with the same, wherein pixels of the image sensor include: the device comprises a photosensitive element, a storage capacitor, a floating diffusion region, a first transmission tube, a second transmission tube, a reset circuit and a voltage output circuit; the storage capacitor comprises a grid and a doped region, and the initial potential of the storage capacitor is pulled high when the grid of the storage capacitor is set to be at a high level.

Description

Image sensor and imaging device equipped with image sensor

Technical Field

The present disclosure relates to the field of image sensor technology, and more particularly, to an image sensor and an imaging device equipped with the same.

Background

The image sensor chip can be divided into a rolling shutter CIS (rolling shutter CIS) image sensor and a global shutter CIS (global shutter CIS) image sensor according to the exposure and corresponding reading mode. The global shutter image sensor includes a Photodiode (PD), a storage capacitor (MN), a Floating Diffusion (FD), and the like. Usually, the storage capacitor is an N-type diffusion region with a low doping concentration, and in the charge storage stage, the initial potential is not too high, and an excessively high initial potential can cause an excessively large dark current of the storage capacitor; meanwhile, in the subsequent signal reading process, the charges are difficult to transfer to the floating diffusion region; however, the low initial potential of the storage capacitor will cause the charges not completely transferred to cause the charges to remain in the photodiode when the charges in the photodiode are transferred to the storage capacitor through the transfer tube, which affects the final image quality.

Disclosure of Invention

In view of the foregoing, the present specification provides an image sensor and an imaging apparatus mounted with the image sensor.

In a first aspect, the present description provides an image sensor comprising a pixel array comprising a plurality of pixels, the pixels comprising:

a photosensor for receiving photons to generate photo-generated electrons;

a storage capacitor for storing the photo-generated electrons;

a floating diffusion region for receiving the photo-generated electrons to generate an exposure voltage signal;

the first transmission pipe can be controlled to be switched on or switched off to connect or disconnect the photosensitive element and the storage capacitor;

a second transfer tube capable of being controlled to be turned on or off to connect or disconnect the storage capacitance and the floating diffusion region;

a reset circuit for resetting the photosensitive element and the floating diffusion region;

the voltage output circuit is connected with the floating diffusion region and used for transmitting a voltage signal of the floating diffusion region to a peripheral circuit;

the storage capacitor comprises a grid electrode and a doped region, and the initial potential of the storage capacitor is pulled high when the grid electrode of the storage capacitor is set to be at a high level;

after the photosensitive element receives photons to generate photo-generated electrons, the first transmission tube is controlled to be conducted, the grid electrode of the storage capacitor is set to be at a high level, the photo-generated electrons are stored in the storage capacitor, and the second transmission tube is controlled to be conducted, so that the floating diffusion region receives the photo-generated electrons in the storage capacitor to generate an exposure voltage signal.

In a second aspect, the present specification provides an image sensor comprising a pixel array comprising a plurality of pixels, the pixels comprising:

a photosensor for receiving photons to generate photo-generated electrons;

a storage capacitor for storing the photo-generated electrons;

the storage capacitor comprises a grid electrode and a doped region, and the initial potential of the storage capacitor is pulled high when the grid electrode of the storage capacitor is set to be at a high level.

In a third aspect, the present specification provides an imaging apparatus carrying any one of the above-described image sensors.

Embodiments of the present disclosure provide an image sensor and an imaging device equipped with the image sensor, which can improve an imaging effect.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure as claimed.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a schematic diagram of an image sensor;

FIG. 2 is a schematic diagram of a current pixel unit;

fig. 3 is a schematic structural diagram of an image sensor pixel according to an embodiment of the present disclosure;

FIG. 4 is a timing diagram of an image sensor pixel during operation;

fig. 5 is a schematic structural diagram of an imaging device according to an embodiment of the present disclosure.

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present specification without any creative effort belong to the protection scope of the present specification.

The flow diagrams depicted in the figures are merely illustrative and do not necessarily include all of the elements and operations/steps, nor do they necessarily have to be performed in the order depicted. For example, some operations/steps may be decomposed, combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.

Some embodiments of the present description will be described in detail below with reference to the accompanying drawings. The embodiments described below and the features of the embodiments can be combined with each other without conflict.

Fig. 1 is a schematic structural diagram of an image sensor. The image sensor can be divided into a photosensitive circuit area and a peripheral circuit area according to functional components, the photosensitive circuit area is composed of tens of thousands to hundreds of millions of photosensitive units (pixels), and the peripheral circuit is responsible for converting signals induced by the photosensitive circuit into digital signals and reading the digital signals.

The photosensitive unit of the image sensor, i.e. the pixel (pixel), is generally mainly composed of a photodiode, a transfer tube, a floating diffusion region, a reset tube, etc. which are composed of the following parts.

Fig. 2 is a schematic diagram of a pixel structure of a current charge-driven (charge domain) global shutter image sensor (GS-CIS). All pixels in the global shutter image sensor can be reset and exposed simultaneously, so that the jelly effect of a rolling shutter (rolling shutter CIS) image sensor when a moving object is shot is prevented, namely the moving object can be deformed to a certain degree, and the image is distorted. And the global shutter image sensor has the advantages of simple design and low noise.

As shown in fig. 2, the pixel unit of the image sensor is composed of a photodiode PD, a first transfer tube TX1, a storage capacitor MN, a second transfer tube TX2, a floating diffusion FD, and a reset circuit and a voltage output circuit. As shown in fig. 2, the reset circuit includes a first reset transistor GR and a second reset transistor RST; the voltage output circuit consists of a source follower SF and a row gate tube SEL.

Usually, the storage capacitor is an N-type diffusion region with a lower doping concentration, and in the charge storage stage, the initial potential is not too high, and the excessively high initial potential can cause an excessively large dark current of the storage capacitor, so that the charge is difficult to be transferred to the floating diffusion region; however, the low initial potential of the storage capacitor will cause the charges not completely transferred to cause the charges to remain in the photodiode when the charges in the photodiode are transferred to the storage capacitor through the transfer tube, which affects the final image quality.

In order to solve the above problems, according to an embodiment of the present invention, the structure and the corresponding control timing of the pixel of the image sensor are improved to realize that the storage capacitor can fully transfer the charges in the photodiode at a lower initial potential, thereby ensuring a better imaging effect.

An embodiment of the present specification provides an image sensor including a plurality of pixels.

Referring to fig. 3, fig. 3 is a schematic circuit diagram of a pixel in an image sensor according to an embodiment of the present disclosure.

Specifically, as shown in fig. 3, the pixel includes a photosensitive element PD, a storage capacitor MN, a floating diffusion FD, a first transfer tube TX1, a second transfer tube TX2, and a voltage output circuit 11 and a reset circuit 12.

Wherein the photo sensitive element PD is adapted to receive photons to generate photo-generated electrons.

Specifically, the photosensor PD may include a photoelectric conversion element such as a photodiode.

The floating diffusion FD is used to receive photo-generated electrons to generate an exposure voltage signal Vsig.

Specifically, the floating diffusion FD may include a PN junction, which is capable of storing charges. The voltage signal of the floating diffusion FD varies with the variation of the stored charge.

The storage capacitor MN is used for storing photo-generated electrons.

Specifically, the first transmission pipe TX1 can be controlled to be turned on or off to connect or disconnect the photosensor PD and the storage capacitor MN.

Specifically, the second transfer tube TX2 can be controlled to be turned on or off to connect or disconnect the storage capacitance MN and the floating diffusion FD;

illustratively, as shown in fig. 3, the first transmission tube TX1 is connected between the photosensitive element PD and the storage capacitor MN, for example, the source of the first transmission tube TX1 is connected to the photosensitive element PD, and the drain of the first transmission tube TX1 is connected to the storage capacitor MN.

Illustratively, the gate 22 of the first transmission pipe TX1 is connected to a first transmission control signal line of the image sensor.

For example, when the potential of the first transmission control signal line is at a high level, the gate 22 of the first transmission tube TX1 is set at a high level, so that the first transmission tube TX1 is turned on; when the potential of the first transmission control signal line is at a low level, the gate 22 of the first transmission tube TX1 is at a low level, so that the first transmission tube TX1 is turned off.

Specifically, when the first transmission tube TX1 is turned on, photo-generated electrons generated by the photo-sensitive element PD can be transferred to the storage capacitor MN.

Illustratively, as shown in fig. 3, the second transmission tube TX2 is connected between the storage capacitor MN and the floating diffusion FD, for example, the source of the first transmission tube TX1 is connected to the storage capacitor MN, and the drain of the first transmission tube TX1 is connected to the floating diffusion FD.

Illustratively, the gate 22 of the first transmission pipe TX1 is connected to the second transmission control signal line of the image sensor.

Illustratively, when the potential of the second transmission control signal line is at a high level, the gate 22 of the second transmission transistor TX2 is set at a high level, so that the second transmission transistor TX2 is turned on; when the potential of the second transmission control signal line is at a low level, the gate 22 of the second transmission transistor TX2 is set to a low level, so that the second transmission transistor TX2 is turned off.

Specifically, when the second transmission tube TX2 is turned on, photo-generated electrons stored in the storage capacitor MN can be transferred to the floating diffusion FD.

The voltage output circuit 11 is connected to the floating diffusion FD, and is configured to transmit the voltage of the floating diffusion FD to the peripheral circuit. As shown in fig. 3, the output terminal PXD of the voltage output circuit 11 is connected to a peripheral circuit.

The peripheral circuit may include, for example, an analog-to-digital conversion circuit, and the voltage change of the floating diffusion FD may be converted by quantization to obtain a corresponding digital image.

By way of example, the floating diffusion FD may be understood as a capacitor, and the introduction of the charge induces a corresponding potential difference av, which may be converted into a corresponding digital image by subsequent quantization of the peripheral circuitry.

In some embodiments, the image sensor may include a peripheral circuit, or certainly may not include a peripheral circuit, for example, functions such as analog-to-digital conversion may be implemented by an additionally mounted peripheral circuit.

Specifically, as shown in fig. 3, the storage capacitor MN includes a doped region 21 and a gate 22, and the gate 22 of the storage capacitor MN is set to a high level to pull up the initial potential of the storage capacitor MN.

Illustratively, the gate 22 of the storage capacitor MN is connected to a storage capacitor control signal line, which is set to a high level to raise the initial potential of the storage capacitor MN.

It is understood that the storage capacitor MN includes a capacitor formed by the gate 22 and the doped region 21.

Specifically, when the gate 22 of the storage capacitor MN is set to a high level, due to the coupling effect of the gate 22 on the doped region 21, the initial potential of the storage capacitor MN can be significantly raised, so as to improve the extraction capability of the storage capacitor MN on photo-generated electrons of the photosensitive element PD, and thus, charges in the photosensitive element PD can be completely transferred.

Specifically, when the gate 22 of the storage capacitor MN is set to a low level, the initial potential of the storage capacitor MN is low, and the photo-generated electrons stored in the storage capacitor MN can be smoothly transferred to the floating diffusion FD.

Therefore, the initial potential of the storage capacitor MN can be lower, and photo-generated electrons of the photosensitive element PD can be fully transferred to the storage capacitor MN, so that the imaging effect can be improved.

In some embodiments, an insulating layer is disposed between the gate 22 and the doped region 21. The insulating layer, for example comprising a silicon dioxide insulating layer, may be formed on the doped region 21 by an oxidation process. The insulating layer may enable the coupling of the gate 22 to the doped region 21.

In some embodiments, the gate 22 includes at least one of a polysilicon gate, a metal gate. For example, a layer of Metal (Metal) or Polysilicon (Polysilicon) may be plated on the surface of the insulating layer, and electrodes may be pulled out to form the Gate 22 (Gate).

In some embodiments, the doped region 21 comprises a doped silicon region, such as an N-type doped silicon region, which is more suitable for storing electrons.

Specifically, the reset circuit 12 is used to reset the photosensitive element PD and the floating diffusion FD.

In some embodiments, as shown in fig. 3, the reset circuit 12 includes a first reset tube GR connected to the photosensitive element PD, the first reset tube GR being capable of being controlled to be turned on or off, and connecting the photosensitive element PD to the reset high level VDD when turned on.

When the first reset tube GR is controlled to be turned on, the photosensitive element PD clears the residual charge in the photosensitive element PD by the reset high level VDD.

When the first reset tube GR is controlled to be turned off, photo-generated electrons can be generated and maintained by the photo-sensitive element PD during exposure.

Illustratively, the first reset tubes GR of all pixels in the image sensor are all connected to a first reset signal line, and when the first reset signal line is set to the high level VDD, the first reset tubes GR of all pixels are controlled to be turned on, so as to implement Global reset (Global reset) of the photosensitive elements PD of the image sensor, and facilitate that each pixel of the image sensor can be exposed at the same time.

Illustratively, one end of the photosensitive element PD is connected to the first reset tube GR, and the other end is connected to an end of the first transmission tube TX1 away from the storage capacitor MN. The interference can be reduced and the arrangement of pixels in the image sensor is facilitated, for example, the first reset tubes GR of adjacent pixels can be closely arranged.

In some embodiments, as shown in fig. 3, the reset circuit 12 includes a second reset transistor RST connected to the floating diffusion FD, which can be controlled to turn on or off and connects the floating diffusion FD to a reset high level VDD when turned on. When the second reset transistor RST is controlled to be turned on, the floating diffusion FD is subjected to a reset high level VDD via the turned-on second reset transistor RST, and reset and cleared.

Illustratively, the second reset tube RST is connected to the second reset signal line, and when the second reset signal line is set to the high level VDD, the second reset tube RST is controlled to be turned on, so as to reset the floating diffusion FD (Global reset) of the pixel.

When the second reset signal line is set to a low level, the second reset transistor RST is controlled to be turned off, and at this time, the floating diffusion FD may receive the photo-generated electrons stored in the storage capacitor MN when the second transmission transistor TX2 is turned on.

For example, the second reset transistors RST of all the pixels of the image sensor may be connected to the same second reset signal line, and the pixels of the image sensor may be synchronously controlled by the second reset signal line, for example, the signal voltages of all the pixels of the image sensor may be read at one time.

For example, the second reset transistors RST of the pixels of the image sensor may be connected to different second reset signal lines, for example, the same row or rows of pixels of the image sensor are connected to one second reset signal line, and the different row or rows of pixels are connected to another second reset signal line. In this case, the signal voltages of one or more rows of pixels of the image sensor can be read at a time, and resources of peripheral circuits can be saved.

In some embodiments, after the photo-sensitive element PD receives photons to generate photo-generated electrons, the first transmission tube TX1 is controlled to be turned on and the gate 22 of the storage capacitor MN is set to a high level to store the photo-generated electrons in the storage capacitor MN, and the second transmission tube TX2 is controlled to be turned on to enable the floating diffusion FD to receive the photo-generated electrons in the storage capacitor MN to generate the exposure voltage signal Vsig.

Illustratively, fig. 4 is a timing diagram illustrating the operation of the pixel of the image sensor.

As shown in fig. 4, the imaging of the image sensor includes stages S1 to S6, which are a Reset stage (Globle Reset), an Exposure stage (Exposure time), a Charge storage stage (Charge store), a floating diffusion Reset and reference voltage readout stage (Reset & SHR), a Charge transfer stage (Charge transfer), and a signal voltage readout stage (SHS), respectively.

In some embodiments, as shown in fig. 4, the reset phase includes a time period between time T1 and time T2, the exposure phase starts after time T2 and ends at time T3, the charge storage phase includes a time period between time T3 and time T7, the set diffusion reset and reference voltage readout phase includes a time period between time T7 and time T11, the charge transfer phase includes a time period between time T11 and time T13, and the signal voltage readout phase includes a time period between time T13 and time T14.

In some embodiments, after the first reset tube GR is controlled to be turned on to reset the light sensitive element PD, the first reset tube GR is controlled to be turned off to make the light sensitive element PD receive photons to generate photo-generated electrons.

As shown in fig. 4, the potential of the first reset control signal line is set to a high level at time T1, the first reset transistor GR is controlled to be turned on, and the photosensitive element PD is reset and cleared by the reset high level VDD via the turned-on first reset transistor GR.

Then, at time T2, the potential of the first reset control signal line is set to a low level, and the first reset tube GR is controlled to be turned off, so that the photo-generated electrons can be generated and maintained by the photo-sensitive element PD during exposure.

Illustratively, the first transmission tube TX1 is controlled to be turned off when the first reset tube GR is controlled to be turned off so that the photosensitive element PD receives photons to generate photo-generated electrons.

Specifically, during the exposure phase, the first reset tube GR and the first transmission tube TX1 are controlled to be turned off, so that the photosensitive element PD receives photons to generate photo-generated electrons and maintains the photo-generated electrons in the photosensitive element PD.

Illustratively, during a charge storage period after the exposure period ends, such as at times T3-T5, the first transfer control signal line is set high, the second transfer control signal line is set low, and the storage capacitor control signal line is set high.

Specifically, the first transmission tube TX1 is controlled to be turned on, the gate 22 of the storage capacitor MN is set to a high level, the photo-generated electrons of the photo-sensitive element PD can be transferred to the storage capacitor MN through the turned-on first transmission tube TX1, and due to the coupling effect of the gate 22 on the doped region 21, the extraction capability of the storage capacitor MN on the photo-generated electrons of the photo-sensitive element PD is improved, so that the charges in the photo-sensitive element PD can be completely transferred.

Illustratively, the second transmission tube TX2 is controlled to be turned off when the first transmission tube TX1 is controlled to be turned on and the gate 22 of the storage capacitor MN is set to a high level so that photo-generated electrons are stored in the storage capacitor MN.

For example, at the time T3-T5, the first transmission tube TX1 is controlled to be turned on, the second transmission tube TX2 is controlled to be turned off, the gate 22 of the storage capacitor MN is set to a high level, photo-generated electrons of the photosensitive element PD can be transferred to the storage capacitor MN through the turned-on first transmission tube TX1, and the turned-off second transmission tube TX2 can confine the photo-generated electrons in the storage capacitor MN and prevent the photo-generated electrons from leaking to the floating diffusion region FD.

For example, the second transmission tube TX2 may be turned off first, and then the first transmission tube TX1 may be turned on, as shown in fig. 4, the second transmission tube TX2 may be turned off at time T3, and the first transmission tube TX1 may be turned on at time T4 after time T3.

For example, after the first transmission tube TX1 is controlled to be turned on and the gate 22 of the storage capacitor MN is set to a high level so that photo-generated electrons are stored in the storage capacitor MN, the first transmission tube TX1 is controlled to be turned off first, and then the gate 22 of the storage capacitor MN is set to a low level.

As shown in fig. 4, the first transmission pipe TX1 is turned off at time T5, and the gate 22 of the storage capacitor MN is set to a low level at time T6 after time T5. To maintain the photo-generated electrons in the storage capacitor MN before the first transmission tube TX1 is turned off, and to prevent the photo-generated electrons in the storage capacitor MN from being transferred to the photo-sensitive element PD through the first transmission tube TX1 when the gate 22 of the storage capacitor MN is set to a low level.

Specifically, at time T11 to time T12 after time T6, the second transfer control signal line is set to high level, and the second transfer transistor TX2 is controlled to conduct to make the floating diffusion FD receive the photo-generated electrons in the storage capacitor MN to generate the exposure voltage signal Vsig.

Illustratively, at time T13 after the second pass tube TX2 is controlled to conduct such that the floating diffusion region FD receives the photo-generated electrons in the storage capacitor MN to generate the exposure voltage signal Vsig, the voltage output circuit 11 outputs the exposure voltage signal Vsig to the peripheral circuit, which can be read by the peripheral circuit 11.

For example, the voltage output circuit 11 may output the voltage of the floating diffusion FD to a peripheral circuit, so that the peripheral circuit processes a corresponding digital image.

Specifically, the second pass transistor TX2 is controlled to turn off before the voltage output circuit 11 outputs the exposure voltage signal Vsig to the peripheral circuit. The second pass transistor TX2 is controlled to be turned off, for example, at a time T12 before a time T13 to keep the voltage of the floating diffusion FD stable.

In some embodiments, as shown in fig. 3, the voltage output circuit 11 includes a row gate line SEL.

Specifically, the row gate SEL can be controlled to be turned on or off, one end of the row gate SEL is connected to the peripheral circuit, and the other end of the row gate SEL is connected to the floating diffusion FD.

Illustratively, the source of the row gate line SEL may be connected to a peripheral circuit through the output terminal PXD, the drain of the row gate line SEL is connected to the floating diffusion FD, and the gate 22 of the row gate line SEL is connected to a row selection signal line.

Illustratively, when the potential of the row selection signal line is at a high level, the gate 22 of the row gate line SEL is at a high level, so that the row gate line SEL is turned on; when the potential of the row selection signal line is at a low level, the gate 22 of the row gate line SEL is at a low level, so that the row gate line SEL is turned off.

Specifically, when the row gate line SEL is controlled to be turned on, the voltage output circuit 11 transmits the voltage signal of the floating diffusion FD to the peripheral circuit.

Illustratively, as shown in fig. 4, at time T7 to time T14 after the charge storage period, the potential of the row selection signal line is set to a high level, the row selection pipe SEL is controlled to be turned on, and the exposure voltage signal Vsig of the floating diffusion FD can be transmitted to the peripheral circuit through the turned-on row selection pipe SEL.

In some embodiments, before the second pass transistor TX2 is controlled to be turned on to make the floating diffusion region FD receive the photo-generated electrons in the storage capacitor MN to generate the exposure voltage signal Vsig, the row gate transistor SEL is turned on to make the voltage output circuit 11 output the reference voltage Vref to the peripheral circuits.

Illustratively, as shown in fig. 4, at time T7 to time T11, the potential of the second transfer control signal line is set to a low level, the second transfer transistor TX2 is turned off, and the floating diffusion FD does not receive the photo-generated electron generation exposure voltage signal Vsig.

The row gate line SEL is controlled to be turned on at time T7, and the peripheral circuit may detect the voltage of the floating diffusion FD, which has not been affected by photo-generated electrons and may be used as the reference voltage Vref, via the turned-on row gate line SEL.

Illustratively, the peripheral circuit determines the induced voltage of the pixel from the difference between the exposure voltage signal Vsig and the reference voltage Vref.

As can be appreciated, the exposure voltage signal Vsig is the voltage of the reference voltage Vref after being affected by the photo-generated electrons. The difference Δ V between the exposure voltage signal Vsig and the reference voltage Vref may represent the strength of the influence of photo-generated electrons generated when the photo-sensitive element PD is exposed on the voltage of the floating diffusion FD. For example, the stronger the exposure, the larger the difference Δ V. The peripheral circuit determines the induced voltage of the pixel according to the difference between the exposure voltage signal Vsig and the reference voltage Vref, and determines the photosensitive quantity of the pixel exposed at this time according to the corresponding relation between the induced voltage and the photosensitive quantity.

Specifically, the electric charges are transferred to the floating diffusion FD, and the peripheral circuit can read out the signal voltage at the output terminal PXD of the voltage output circuit 11. By calculating the Δ V-Vref-Vsig, a voltage signal positively correlated to the incident light signal can be obtained, and the signal can be converted into a corresponding digital image signal after being processed by subsequent circuits.

In some embodiments, as shown in fig. 3, the voltage output circuit 11 further includes a source follower SF. Specifically, the drain of the row gate line SEL is connected to the floating diffusion FD via the source follower SF.

Illustratively, the source follower SF has a high input resistance and a low output resistance, and is equivalent to an open circuit for a front-stage circuit and a constant voltage source for a rear-stage circuit, and the output voltage is not affected by the impedance of the rear-stage circuit.

For example, the source follower SF may be used to amplify and output the electric signal of the floating diffusion FD.

Illustratively, the source follower SF is turned on to enable the exposure voltage signal Vsig of the floating diffusion FD to be transmitted to the peripheral circuits via the source follower SF and the row gate SEL.

Illustratively, the source of the source follower SF is connected to the drain of the row gate SEL, the gate 22 of the source follower SF is connected to the floating diffusion FD, and the drain of the source follower SF is connected to the high level VDD.

Illustratively, the drain of the source follower SF is connected to a row input signal line of the image sensor. When the potential of the row input signal line is high, the drain of the source follower SF is high, and the exposure voltage signal Vsig of the floating diffusion FD can be transmitted to the drain of the row gate SEL via the source follower SF.

For example, the source follower SF is activated by setting the row input signal line to a high level before the second transfer transistor TX2 is controlled to be turned on so that the floating diffusion FD receives the photo-generated electron to generate the exposure voltage signal Vsig, or before the row gate transistor SEL is turned on so that the voltage output circuit 11 outputs the reference voltage Vref to the peripheral circuits.

The peripheral circuit reads the reference voltage Vref from the turned-on row gate transistor SEL from time T9 to time T10, and controls the second transfer transistor TX2 to be turned on at time T11 after time T10, so that the floating diffusion FD receives the photo-generated electrons transferred by the turned-on second transfer transistor TX 2.

Illustratively, at a time T12 after the time T11, the second transmission pipe TX2 is controlled to be turned off; at a time T13 after the time T12, the peripheral circuit reads the exposure voltage signal Vsig of the floating diffusion FD from the turned-on row gate line SEL.

Specifically, after the exposure voltage signal Vsig of the floating diffusion FD is transmitted to the peripheral circuit, for example, at time T14, the potential of the row selection signal line may be set to a low level, the row selection transistor SEL is controlled to be turned off, and preparation may be made for the next imaging process.

Illustratively, after the voltage output circuit 11 transmits the exposure voltage signal Vsig of the floating diffusion FD to the peripheral circuit, the source follower SF may be turned off by setting the drain of the source follower SF to a low level.

In some embodiments, the reset circuit 12 resets the floating diffusion FD before the second transfer tube TX2 is controlled to conduct such that the floating diffusion FD receives the photo-generated electron generation exposure voltage signal Vsig in the storage capacitor MN. To clear the influence of the residual electrons on the exposure voltage signal Vsig of the storage capacitor MN.

Illustratively, the reset circuit 12 resets the floating diffusion FD before the row gate SEL is turned on to cause the voltage output circuit 11 to output the reference voltage Vref to the peripheral circuit. To make the reference voltage Vref more accurate.

Specifically, after the reset circuit 12 resets the floating diffusion FD, and before the second transfer transistor TX2 is controlled to be turned on so that the floating diffusion FD receives the photo-generated electrons in the storage capacitor MN to generate the exposure voltage signal Vsig, the voltage output circuit 11 outputs the reference voltage Vref to the peripheral circuit. It is therefore possible to read the reference voltage Vref of the voltage output circuit 11 after resetting the floating diffusion FD, and then to make the floating diffusion FD receive the photo-generated electrons in the storage capacitance MN to generate the exposure voltage signal Vsig. The accuracy of the reference voltage Vref can be improved, and the accuracy of the exposure voltage signal Vsig can also be improved.

As shown in fig. 4, before time T8, the second reset signal line is set to a high level, and the second reset transistor RST is controlled to be turned on, thereby resetting the floating diffusion FD of the pixel.

Specifically, when the second reset signal line is set to a low level at time T8, the second reset transistor RST is controlled to be turned off; and at time T9 after time T8, the peripheral circuit reads the reference voltage Vref from the voltage output circuit 11. Since the floating diffusion FD connected to the voltage output circuit 11 is reset, the resultant reference voltage Vref can be more accurate.

Illustratively, the second transfer tube TX2 is controlled to conduct to reset the storage capacitor MN at least part of the time that the reset circuit 12 resets the floating diffusion FD.

For example, the second reset signal line is continuously set to the high level from time T1 to time T8 to keep the floating diffusion FD reset. At the time T1 to the time T3, the second pass transistor TX2 is controlled to be turned on, and the storage capacitor MN may be reset under the action of the reset floating diffusion FD; therefore, in the charge storage stage, the storage capacitor MN can store photo-generated electrons more accurately, and the influence of residual electrons is prevented.

Illustratively, the second reset transistor RST is switched from a controlled on state to a controlled off state before the second pass transistor TX2 is controlled on state so that the floating diffusion region FD receives the photo-generated electron generation exposure voltage signal Vsig from the storage capacitor MN.

For example, at time T8, the second reset tube RST transitions from a controlled on to a controlled off. So that the peripheral circuit reads the reference voltage Vref, the floating diffusion FD receives photo-generated electrons in the storage capacitor MN to generate an exposure voltage signal Vsig, and the peripheral circuit reads the exposure voltage signal Vsig.

Illustratively, the second pass transistor TX2 is controlled to be turned off before the voltage output circuit 11 outputs the reference voltage Vref to the peripheral circuit.

As shown in fig. 4, at the time T3 to T9 before the time T9, the second pass transistor TX2 is controlled to turn off to stabilize the voltage of the floating diffusion FD, so that the reference voltage Vref read by the peripheral circuit is more accurate.

In some embodiments, as shown in fig. 4, the imaging process of the image sensor pixel may include:

reset phase S1: controlling the first reset tube GR to be turned on at time T1, and resetting and clearing the photosensitive element PD by the reset high level VDD through the turned-on first reset tube GR; the first reset tube GR is controlled to be turned off at time T2 to prepare the photosensitive element PD for generating and maintaining photo-generated electrons during exposure.

Exposure stage S2: some time after time T2, the photosensitive element PD may be exposed to produce photo-generated electrons by, for example, controlling the shutter to open.

Charge storage phase S3: the second transmission tube TX2 is turned off at the time T3, the first transmission tube TX1 is turned on at the time T4, and the gate 22 of the storage capacitor MN is set to be at a high level, so that the photo-generated electrons of the photosensitive element PD can be transferred to the storage capacitor MN through the turned-on first transmission tube TX1, and the turned-off second transmission tube TX2 can confine the photo-generated electrons in the storage capacitor MN; at this time, due to the coupling effect of the gate 22 to the doped region 21, the extraction capability of the storage capacitor MN to the photo-generated electrons of the photosensitive element PD is improved, so that the charges in the photosensitive element PD can be completely transferred.

The first transmission tube TX1 is turned off at time T5, and the gate 22 of the storage capacitor MN is set to a low level at time T6 to latch charges in the storage capacitor MN, which is at a lower potential.

Floating diffusion reset and reference voltage sensing phase S4: the row gate line SEL is controlled to be turned on at time T7, and the peripheral circuit may detect the voltage of the floating diffusion FD via the turned-on row gate line SEL. Before the time T8, the second reset transistor RST is turned on to reset the floating diffusion FD of the pixel; the second reset transistor RST is turned off at time T8 to stop resetting the floating diffusion FD. Thereafter, at time T9 to time T10, the peripheral circuit floats the reference voltage Vref of the diffusion FD by the voltage output circuit 11.

Charge transfer phase S5: the second pass transistor TX2 is turned on from time T11 to time T12, so that the floating diffusion FD receives the photo-generated electrons in the storage capacitor MN, and the potential of the floating diffusion FD changes under the action of the photo-generated electrons. Specifically, the gate 22 of the storage capacitor MN is set to a low level at this stage, and the photo-generated electrons stored in the storage capacitor MN can be smoothly transferred to the floating diffusion FD.

Signal voltage sensing stage S6: at times T13 to T14, the peripheral circuit floats the exposure voltage signal Vsig of the diffusion FD by the voltage output circuit 11.

The peripheral circuit can determine the induced voltage of the pixel according to the difference between the exposure voltage signal Vsig and the reference voltage Vref, and determine the photosensitive quantity of the pixel exposed at this time according to the corresponding relation between the induced voltage and the photosensitive quantity, so that a corresponding digital image signal can be obtained.

For example, the high level and the reset high level VDD of the storage capacitor control signal line, the first transmission control signal line, the second transmission control signal line, the first reset signal line, the second reset signal line, and the row selection signal line may be the same or different, and the low level may be the same or different. It is understood that the structure of the image sensor can be simplified when the high and low levels of the respective signal lines are identical, and the accuracy of control can be improved when the high and low levels of the signal lines are not identical.

For example, the voltage range of the storage capacitor control signal line may be 0V to 4V, for example, 2V to 4V, which may be determined by debugging.

Illustratively, the voltage of the first reset signal line may range from-1V to 4V, which may be determined by debugging.

It is understood that the timings of the pixels in the image sensor may or may not be synchronized, for example, the timings of the pixels in different rows may not be synchronized, or the timings of the pixels in the image sensor in the reset phase S1, the exposure phase S2, and the charge storage phase S3 may be synchronized, and the timings of the reset phase S4, the charge transfer phase S5, and the signal voltage readout phase S6 may not be synchronized, in which case, the reference voltage and the exposure voltage signals of one or more rows of pixels in the image sensor may be read and analog-to-digital converted at a time, so that the resources of the peripheral circuit may be saved.

The image sensor provided by the embodiment of the present specification, by constructing a gate on a storage capacitor of a pixel of the image sensor, an initial potential of the storage capacitor can be pulled up by applying a high level to the gate in a charge storage stage, so as to improve an extraction capability of the storage capacitor to photo-generated electrons, and thus charges in a photosensitive element can be completely transferred; and the grid can be set to be at a low level in the charge transfer stage, so that the photogenerated electrons stored by the storage capacitor can be smoothly transferred to the floating diffusion region, and the imaging effect is favorably improved.

Referring to fig. 5 in conjunction with the above embodiments, fig. 5 is a schematic block diagram of an imaging device 600 according to an embodiment of the present disclosure. The imaging device 600 is equipped with the image sensor 601 described above.

In some embodiments, the imaging device 600 may further include a lens module 602.

The specific principle and implementation of the imaging device provided in the embodiments of the present disclosure are similar to those of the image sensor of the foregoing embodiments, and are not described herein again.

It is to be understood that the terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the description.

It should also be understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the present disclosure, and these modifications or substitutions should be covered within the scope of the present disclosure. Therefore, the protection scope of the present specification shall be subject to the protection scope of the claims.

Claims

1. An image sensor comprising a pixel array comprising a plurality of pixels, wherein the pixels comprise:

a photosensor for receiving photons to generate photo-generated electrons;

a storage capacitor for storing the photo-generated electrons;

2. The image sensor of claim 1, wherein the reset circuit comprises a first reset transistor coupled to the photosensitive element, the first reset transistor being controllable to turn on or off and, when on, coupling the photosensitive element to a reset high level.

3. The image sensor as claimed in claim 2, wherein one end of the photosensitive element is connected to the first reset tube, and the other end is connected to an end of the first transmission tube away from the storage capacitor.

4. The image sensor of claim 2, wherein after the first reset tube is controlled to be on to reset the photosensitive element, the first reset tube is controlled to be off to allow the photosensitive element to receive photons to generate photo-generated electrons.

5. The image sensor as in claim 4, wherein the first transmission tube is controlled to turn off when the first reset tube is controlled to turn off so that the photosensitive element receives photons to generate photo-generated electrons.

6. The image sensor as in any of claims 1-5, wherein after the first transmission tube is controlled to turn on and the gate of the storage capacitor is set high to store the photo-generated electrons in the storage capacitor, the first transmission tube is controlled to turn off first, and then the gate of the storage capacitor is set low.

7. The image sensor as in claim 6, wherein the second transmission tube is controlled to be turned off when the first transmission tube is controlled to be turned on and the gate of the storage capacitor is set high to store the photo-generated electrons in the storage capacitor.

8. The image sensor of claim 7, wherein the reset circuit resets the floating diffusion region before the second transfer transistor is controlled to conduct such that the floating diffusion region receives photo-generated electrons in the storage capacitor to generate an exposure voltage signal.

9. The image sensor of claim 8, wherein the second pass transistor is controlled to conduct to reset the reservoir capacitance at least a portion of the time that the reset circuit resets the floating diffusion region.

10. The image sensor of claim 8, wherein the reset circuit includes a second reset transistor connected to the floating diffusion, the second reset transistor being controllable to turn on or off and connecting the floating diffusion to a reset high when on.

11. The image sensor as claimed in claim 10, wherein the second reset transistor is switched from the controlled on state to the controlled off state before the second transfer transistor is controlled on state to make the floating diffusion region receive the photo-generated electrons in the storage capacitor to generate the exposure voltage signal.

12. The image sensor of claim 8, wherein the voltage output circuit outputs the exposure voltage signal to the peripheral circuit after the second transfer transistor is controlled to conduct such that the floating diffusion receives photo-generated electrons in the storage capacitor to generate the exposure voltage signal.

13. The image sensor of claim 12, wherein a second pass transistor is controlled to be turned off before the voltage output circuit outputs the exposure voltage signal to the peripheral circuit.

14. The image sensor of claim 13, wherein the voltage output circuit outputs a reference voltage to the peripheral circuit after the reset circuit resets the floating diffusion region and before the second pass transistor is controlled to conduct to cause the floating diffusion region to receive photo-generated electrons in the storage capacitor to generate an exposure voltage signal.

15. The image sensor of claim 14, wherein the second pass transistor is controlled to be turned off before the voltage output circuit outputs the reference voltage to the peripheral circuit.

16. The image sensor of claim 14, wherein the peripheral circuit determines the induced voltage of the pixel based on a difference between the exposure voltage signal and the reference voltage.

17. The image sensor of any of claims 1-16, wherein the voltage output circuit comprises:

the row gate tube can be controlled to be switched on or switched off, one end of the row gate tube is connected with the peripheral circuit, and the other end of the row gate tube is connected with the floating diffusion region;

when the row gate tube is controlled to be conducted, the voltage output circuit transmits the voltage signal of the floating diffusion region to a peripheral circuit.

18. The image sensor of claim 17, wherein the voltage output circuit further comprises a source follower;

the other end of the row gate tube is connected with the floating diffusion region through the source follower.

19. The image sensor as in any of claims 1-16, wherein an insulating layer is disposed between the gate and the doped region.

20. The image sensor of claim 19, wherein the gate comprises at least one of a polysilicon gate, a metal gate, and the doped region comprises a doped region of silicon.

21. An image sensor comprising a pixel array comprising a plurality of pixels, wherein the pixels comprise:

a photosensor for receiving photons to generate photo-generated electrons;

a storage capacitor for storing the photo-generated electrons;

22. The image sensor of claim 21, wherein the reset circuit comprises a first reset transistor coupled to the photosensitive element, the first reset transistor being controllable to turn on or off and, when on, coupling the photosensitive element to a reset high level.

23. The image sensor as claimed in claim 22, wherein one end of the photosensitive element is connected to the first reset tube, and the other end is connected to an end of the first transmission tube away from the storage capacitor.

24. The image sensor of claim 22, wherein the reset circuit comprises a second reset transistor coupled to the floating diffusion, the second reset transistor being controllable to turn on or off and coupling the floating diffusion to a reset high when on.

25. The image sensor of any of claims 21-24, wherein the voltage output circuit comprises:

26. The image sensor of claim 25, wherein the voltage output circuit further comprises a source follower;

27. The image sensor as in any of claims 21-26, wherein an insulating layer is disposed between the gate and the doped region.

28. The image sensor of claim 27, wherein the gate comprises at least one of a polysilicon gate, a metal gate, and the doped region comprises a doped region of silicon.

29. An imaging apparatus carrying the image sensor according to any one of claims 1 to 28.