CN109005374A - Image sensor pixel circuit and its working method - Google Patents
Image sensor pixel circuit and its working method Download PDFInfo
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- CN109005374A CN109005374A CN201811066988.6A CN201811066988A CN109005374A CN 109005374 A CN109005374 A CN 109005374A CN 201811066988 A CN201811066988 A CN 201811066988A CN 109005374 A CN109005374 A CN 109005374A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/75—Circuitry for providing, modifying or processing image signals from the pixel array
Abstract
A kind of image sensor pixel circuit and its working method, image sensor pixel circuit include: pixel unit, and the pixel unit includes: column sense line；Detection unit, the detection unit include: capacitor, and the capacitor has opposite first capacitor end and the second capacitance terminal, and first capacitor end is connect with the column sense line；Comparator, the comparator have first compare input terminal, second compare input terminal and compare output end, and second compares input terminal connect with the second capacitance terminal, and first, which compares input terminal, compares clock signal suitable for inputting；Switch, input terminal output end compared with connects the switch compared with second respectively.The performance of described image sensor pixel circuit is improved.
Description
Technical field
The present invention relates to semiconductor detection field more particularly to a kind of image sensor pixel circuit and its working methods.
Background technique
Imaging sensor is a kind of semiconductor devices for converting optical signal into electric signal.
Imaging sensor is divided into complementary metal oxide (CMOS) imaging sensor and charge-coupled device (CCD) image passes
Sensor.Wherein cmos image sensor have simple process, be easy to integrated other devices, small in size, light-weight, small power consumption and at
This low advantage.Therefore, with the development of image sensing technology, cmos image sensor replaces ccd image to pass more and more
Sensor is applied in each electronic product.Currently, cmos image sensor has been widely used for static digital camera, number is taken the photograph
Camera, medical photographic device and automobile-used photographic device etc..
However, the performance of existing imaging sensor is to be improved.
Summary of the invention
Problems solved by the invention is to provide a kind of image sensor pixel circuit and forming method thereof, to improve image biography
The performance of sensor pixel circuit.
To solve the above problems, the present invention provides a kind of image sensor pixel circuit, comprising: pixel unit, the picture
Plain unit includes: column sense line；Detection unit, the detection unit include: capacitor, and the capacitor has opposite first capacitor
End and the second capacitance terminal, first capacitor end is connect with the column sense line；Comparator, the comparator have first to compare input
End, second compare input terminal and compare output end, and second compares input terminal connect with the second capacitance terminal, and first, which compares input terminal, fits
Compare clock signal in input；Switch, input terminal output end compared with connects the switch compared with second respectively.
Optionally, there is the column sense line opposite first to read end and the second reading end；The pixel unit also wraps
It includes: photodiode；Transmission transistor, the source level of the transmission transistor are connect with the photodiode；Floating spreads point,
The floating diffusion point is connected with the drain electrode of the transmission transistor；Reset transistor, the source electrode of the reset transistor and institute
Floating diffusion point connection is stated, the drain electrode of the reset transistor is connect with power supply line；Amplifying transistor, the amplifying transistor
Grid and floating diffusion point connection, the drain electrode of the amplifying transistor are connect with power supply line；Selection transistor, the selection crystal
The drain electrode of pipe is connect with the source level of the amplifying transistor；First reading end is connect with the source level of the selection transistor,
Second reading end is connect with first capacitor end.
Optionally, further includes: analog-to-digital conversion module, the analog-to-digital conversion module have the first image data input, the
Two image data inputs and image data output end, the first image data input are connect with the column sense line, and described
Two image data inputs output end compared with described connects, and described image data output end is suitable for output digital image signal,
The data and the second image data input that the data image signal is suitable for being inputted according to the first image data input input
Data acquisition.
Optionally, further includes: image processing module, described image processing module are connect with described image data output end,
Described image processing module is suitable for carrying out noise reduction process to the data image signal.
The present invention also provides a kind of working methods of image sensor pixel circuit, comprising: provides above-mentioned image sensing
Device pixel circuit；The detection unit carries out benchmark sampling to the voltage of the column sense line, is carrying out the benchmark sampling
In the process, the switch is in the conductive state；After carrying out the benchmark sampling, the switch is disconnected；After disconnecting the switch, drop
Big as low as the first level value of the low relatively clock signal；After reducing the relatively size of clock signal, it is compared and adopts
Sample step；The relatively sampling step includes: that second is sampled and be coupled to the signal of the column sense line to compare input
End makes second to compare input terminal with second electrical level value；The comparator is compared second electrical level value and the first level value
Afterwards, output detection signal.
Optionally, there is the column sense line opposite first to read end and the second reading end；The pixel unit also wraps
It includes: photodiode；Transmission transistor, the source level of the transmission transistor are connect with the photodiode；Floating spreads point,
The floating diffusion point is connected with the drain electrode of the transmission transistor；Reset transistor, the source electrode of the reset transistor and institute
Floating diffusion point connection is stated, the drain electrode of the reset transistor is connect with power supply line；Amplifying transistor, the amplifying transistor
Grid and floating diffusion point connection, the drain electrode of the amplifying transistor are connect with power supply line；Selection transistor, the selection crystal
The drain electrode of pipe is connect with the source level of the amplifying transistor；First reading end is connect with the source level of the selection transistor,
Second reading end is connect with first capacitor end；The working method of described image sensor pixel circuit further include: in the detection
Before unit carries out benchmark sampling to the voltage of the column sense line, reset operation is carried out；During reset operation,
The selection transistor is in the conductive state, and the transmission transistor is in an off state, and the reset transistor is on
State, the switch is in the conductive state, and the relatively clock signal has original levels value, and the original levels value is greater than institute
State the first level value；In benchmark sampling step, the selection transistor is in the conductive state, and the transmission transistor is in disconnected
Open state, the reset transistor are in an off state, and the switch is in the conductive state；The relatively clock signal has just
Beginning level value.
Optionally, threshold value compared with the original levels value is equal to the difference of first level value, the relatively threshold value
It is 90 millivolts~110 millivolts.
Optionally, after benchmark sampling, and before the relatively sampling step, the selection transistor is in
On state, the transmission transistor are in an off state, and the reset transistor is in an off state, and the switch is in disconnected
Open state.
Optionally, described relatively in sampling step, when second electrical level value is greater than the first level value, then the detection signal
For " 0 "；In the relatively sampling step, when second electrical level value is less than the first level value, then the detection signal is " 1 ".
Optionally, described image sensor pixel circuit further include: analog-to-digital conversion module, the analog-to-digital conversion module have
First image data input, the second image data input and image data output end, the first image data input and institute
The connection of column sense line is stated, second image data input output end compared with described connects, described image data output end
Suitable for output digital image signal, data and the second figure that the data image signal is inputted according to the first image data input
The data acquisition inputted as data input pin；If the detection signal is " 0 ", the signal of described image data output end output
The signal inputted by the first image data input pin is directly converted to；If the detection signal is " 1 ", described image
The signal of data output end output is set to the full scale data of analog-to-digital conversion module.
Compared with prior art, technical solution of the present invention has the advantage that
In the working method for the image sensor pixel circuit that technical solution of the present invention provides, in the mistake for carrying out benchmark sampling
Cheng Zhong, the switch is in the conductive state, and the such second current potential for comparing input terminal is equal to the first current potential for comparing input terminal, and
The current potential of column sense line and second are compared the Difference Storage of the current potential of input terminal by the capacitor.Carry out the benchmark sampling
Afterwards, the switch is disconnected, the current potential for making the second current potential for comparing input terminal not compared input terminal by first is influenced；Described in disconnection
After switch, big as low as the first level value for comparing clock signal is reduced；It is compared sampling step later, in relatively sampling step
In, the signal of the column sense line sample and compares input terminal by being capacitively coupled to second, makes second to compare input
End has second electrical level value.Since capacitor plays the Difference Storage for the current potential that the current potential of column sense line and second compare input terminal
Come, therefore, it is consistent that the amplitude of variation of the current potential in the column sense line with described second compares the potential change amplitude of input terminal.
After comparator is compared second electrical level value and the first level value, output detection signal, in this way the size characterization of detection signal
Second compares the amplitude of variation of input terminal potential, and the second amplitude of variation for comparing input terminal potential and the electricity in column sense line
The amplitude of variation of position is consistent, therefore the size for detecting signal also characterizes the amplitude of variation of the current potential in column sense line indirectly.This
Sample to detect signal not by transistor threshold deviation each in pixel circuit and the influence of pixel power voltage fluctuation, makes
It obtains and the accuracy of the testing result of pixel blooming is improved.This improves the property of image sensor pixel circuit
Energy.
Further, described image sensor pixel circuit further include: analog-to-digital conversion module.If the detection signal is " 0 ",
Then the signal of described image data output end output is consistent with the signal that the first image data input pin inputs；If the inspection
Surveying signal is " 1 ", and the signal inputted by the first image data input pin is directly converted to；If the detection signal is
" 1 ", then the signal of described image data output end output is set to the full scale data of analog-to-digital conversion module.Modulus turns in this way
Root tuber is changed the mold according to the logarithmic output signal word picture signal of detection signal and column sense line, the data image signal is to column sense line
The phenomenon that signal has carried out certain modulation, avoids " solar spot ".
Detailed description of the invention
Fig. 1 is a kind of schematic diagram of image sensor pixel circuit；
Fig. 2 is the schematic diagram of solar spot in image sensor pixel circuit；
Fig. 3 is the schematic diagram of image sensor pixel circuit in one embodiment of the invention；
Fig. 4 is the flow chart of the image sensor pixel circuit course of work in another embodiment of the present invention；
Fig. 5 is the timing diagram of the image sensor of that present invention pixel circuit.
Specific embodiment
As described in background, the performance for the image sensor pixel circuit that the prior art is formed is poor.
A kind of image sensor pixel circuit, referring to FIG. 1, including: photodiode；Transmission transistor TG, the biography
The source level of defeated transistor TG is connect with the photodiode；Floating spreads point FD node, and the floating spreads point FD node
It is connected with the drain electrode of the transmission transistor TG；Reset transistor PGRST, the reset transistor PGRSTSource electrode and described floating
Sky diffusion point FD node connection, the reset transistor PGRSTDrain electrode connect with power supply line VDDPIX；Selection transistor PGSF,
The selection transistor PGSFGrid and floating diffusion point FD node connect, the selection transistor PGSFDrain electrode and power supply
Line VDDPIX connection；Amplifying transistor PGRSEL, the amplifying transistor PGRSELDrain electrode and the selection transistor PGSFSource
Grade connection；Column sense line BL, the column sense line BL and the amplifying transistor PGRSELSource level connection.
When image sensor pixel circuit works when illumination is stronger, excessive photogenerated charge, corresponding pixel can be generated
Photoelectron spilling can occur, be spilled over to floating diffusion point FD node.When being spilled over to floating diffusion point FD node, picture can be reduced
The resetting voltage of element.When photoelectron spilling degree is larger, resetting voltage can reduce a lot or even be reduced to 0 level, to lead
The signal of addressed pixel output is " 0 ".
Original spill point should be the overexposure point of incandescent, and since electronics spilling becomes stain instead, this phenomenon is claimed
For " solar spot " (such as Fig. 2).Due to the generation of above-mentioned " solar spot ", the quality of image is seriously reduced, figure is caused
As the performance of sensor pixel circuits is poor.Based on this, need accurately to detect whether image sensor pixel circuit has occurred
Lead to the blooming phenomenon of " solar spot ".
It is a kind of detect blooming phenomenon method include: setting comparing voltage value, directly read the electricity of column sense line BL
Signal is pressed, the voltage signal of the BL of reading is compared with the comparing voltage value, if the voltage signal of the BL read is greater than
The comparing voltage value, then be judged as and blooming do not occur, if the voltage signal of the BL read is less than the comparing voltage value,
Then it is judged as generation blooming.
The method of above-mentioned detection blooming phenomenon has the disadvantage in that due to by transistor threshold each in pixel circuit
It is worth the influence of deviation and pixel power voltage fluctuation, therefore for different pixel units, identical photoelectron overflows degree pair
The voltage signal of the BL answered is different, then may obtain difference when using comparing voltage value compared with the voltage signal of BL
Testing result.Therefore cause the accuracy detected to blooming poor.
On this basis, the present invention provides a kind of image sensor pixel circuit, comprising: pixel unit, the pixel list
Member includes: column sense line；Detection unit, the detection unit include: capacitor, the capacitor have opposite first capacitor end and
Second capacitance terminal, first capacitor end are connect with the column sense line；Comparator, the comparator have first compare input terminal,
Second compares input terminal and compares output end, and second compares input terminal connect with the second capacitance terminal, and first, which compares input terminal, is suitable for
Clock signal is compared in input；Switch, input terminal output end compared with connects the switch compared with second respectively.The method mentions
The high performance of image sensor pixel circuit.
To make the above purposes, features and advantages of the invention more obvious and understandable, with reference to the accompanying drawing to the present invention
Specific embodiment be described in detail.
The present embodiment provides a kind of image sensor pixel circuits, referring to FIG. 2, including:
Pixel unit 10, the pixel unit 10 include: column sense line BL；
Detection unit 20, the detection unit 20 include: capacitor C, and the capacitor C has opposite first capacitor end and the
Two capacitance terminals, first capacitor end and the column sense line BL；Comparator 201, the comparator 201 have first to compare input terminal
VREF_BL, second compare input terminal VN node and compare output end, and second compares input terminal VN node and the second capacitance terminal company
It connects, first, which compares input terminal VREF_BL, compares clock signal suitable for input；Switch CMPRST, the switch CMPRSTRespectively with
Two, which compare input terminal VN node output end compared with, connects.
The switch CMPRSTCompare input terminal VN node output end compared with suitable for being electrically connected or disconnecting second.Specifically
, as the switch CMPRSTWhen in the conductive state, the switch CMPRSTIt is defeated compared with to compare input terminal VN node for second
Outlet is electrically connected；As the switch CMPRSTWhen being in an off state, the switch CMPRSTCompare input terminal VN for second
Node output end electricity compared with disconnects.
The switch CMPRSTCompare input terminal VN node output end compared with for second to be electrically connected, such second compares
The current potential of current potential input terminal VREF_BL compared with first of input terminal VN node is equal.
The switch CMPRSTCompare input terminal VN node output end electricity compared with for second to disconnect, make first more defeated
The current potential for entering to hold the current potential of VREF_BL not compared input terminal VREF_BL by first is influenced, and first compares input terminal VREF_BL
Current potential by the current potential on column sense line BL be coupled to first by capacitor C and compare input terminal VREF_BL and obtain.
There is the column sense line BL opposite first to read end and the second reading end.
The pixel unit 10 further include: photodiode 101；Transmission transistor TG, the source of the transmission transistor TG
Grade is connect with the photodiode 101；Floating spreads point FD node, and the floating diffusion point FD node and the transmission are brilliant
The drain electrode of body pipe TG connects；Reset transistor PGRST, the reset transistor PGRSTSource electrode and the floating spread point FD
Node connection, the reset transistor PGRSTDrain electrode connect with power supply line VDDPIX；Amplifying transistor PGSF, the amplification crystalline substance
Body pipe PGSFGrid and floating diffusion point FD node connect, the amplifying transistor PGSFDrain electrode and power supply line VDDPIX connect
It connects；Selection transistor PGRSEL, the selection transistor PGRSELDrain electrode and the amplifying transistor PGSFSource level connection；Institute
State the first reading end and the selection transistor PGRSELSource level connection, second reading end is connect with first capacitor end.
Described image sensor pixel circuit further include: analog-to-digital conversion module 30 (ADC module), the analog-to-digital conversion module
30 have the first image data input, the second image data input and image data output end, the input of the first image data
End is connect with the column sense line BL, and second image data input output end compared with described connects, described image number
It is suitable for output digital image signal according to output end, what the data image signal was suitable for being inputted according to the first image data input
The data acquisition of data and the input of the second image data input.
The analog-to-digital conversion module 30 includes: analog-digital converter and logic unit, and the first image data input is described
The input terminal of analog-digital converter, the logic unit have the first logic input terminal and the second logic input terminal and logic output
End, first logic input terminal are the second image data input, and the second logic input terminal is defeated with the analog-digital converter
Outlet connection, the logic output terminal are image data output end.
The logic unit is or door, the logic unit are suitable for defeated to the first logic input terminal and the second logic input terminal
The signal entered carries out or logical process.The analog-digital converter is suitable for converting analog signals into digital signal.
Described image sensor pixel circuit further include: image processing module 40, described image processing module 40 with it is described
The connection of image data output end, described image processing module 40 are suitable for carrying out noise reduction process to the data image signal.
Correspondingly, the present embodiment also provides a kind of working method of image sensor pixel circuit, referring to FIG. 4, including
Following steps:
S01: above-mentioned image sensor pixel circuit is provided；
S02: the detection unit 20 carries out benchmark sampling to the voltage of the column sense line BL, adopts carrying out the benchmark
During sample, the switch CMPRSTIt is in the conductive state；
S03: after carrying out the benchmark sampling, the switch CMP is disconnectedRST；
S04: the switch CMP is disconnectedRSTAfterwards, big as low as the first level value of the relatively clock signal is reduced；
S05: after reducing the relatively size of clock signal, it is compared sampling step；The relatively sampling step packet
It includes: the signal of the column sense line BL is sampled and be coupled to second and compare input terminal VN node, make second to compare input
Hold VN node that there is second electrical level value；After the comparator 201 is compared second electrical level value and the first level value, output
Detect signal.
Fig. 5 is the timing diagram of the image sensor of that present invention pixel circuit.V(PGRSEL) it is the selection transistor PGRSEL's
The clock signal of grid, as V (PGRSEL) be high level when, the selection transistor PGRSELConducting, as V (PGRSEL) it is low level
When, the selection transistor PGRSELIt disconnects.
V(PGRST) it is the reset transistor PGRSTGrid clock signal, as V (PGRST) be high level when, it is described
Reset transistor PGRSTConducting, as V (PGRST) be low level when, the reset transistor PGRSTIt disconnects.
V(CMPRST) it is the switch CMPRSTClock signal, as V (CMPRST) be high level when, the switch CMPRST
Conducting, as V (CMPRST) be low level when, the switch CMPRSTIt disconnects.
V (TG) is the clock signal of the grid of the transmission transistor TG, and when V (TG) is high level, the transmission is brilliant
Body pipe TG conducting, when V (TG) is low level, the transmission transistor TG is disconnected.
V (ADC_SMP) is the clock signal of analog-to-digital conversion module 30, when V (ADC_SMP) is high level, analog-to-digital conversion
Module 30 works, and analog-digital converter and logic unit work, when V (ADC_SMP) is low level, analog-to-digital conversion
Module 30 is without work, analog-digital converter and the equal break-off of logic unit.
V (VN node) is the second clock signal for comparing input terminal VN node, and wherein there is no blooms to overflow for L1 representative
Second clock signal for comparing input terminal VN node when out, L2 represent when blooming occurs second and compare input terminal VN node
Clock signal.
V (VREF_BL) is the first clock signal for comparing input terminal VREF_BL.
The working method of described image sensor pixel circuit further include: in the detection unit 20 to the column sense line
Before the voltage of BL carries out benchmark sampling, reset operation is carried out.
During reset operation, the selection transistor PGRSELIt is in the conductive state, the transmission transistor
TG is in an off state, the reset transistor PGRSTIt is in the conductive state, the switch CMPRSTIt is in the conductive state, it is described
Compare clock signal with original levels value, the original levels value is greater than first level value.
During reset operation, the current potential of floating diffusion point FD node is set to the electricity of power supply line VDDPIX
Position VDD, the current potential of column sense line is VDD-Vm at this time, and Vm is by selection transistor PGRSELWith amplifying transistor PGSFEquivalent electricity
Potential difference caused by hindering.
In benchmark sampling step, the selection transistor PGRSELIn the conductive state, the transmission transistor TG is in
Off-state, the reset transistor PGRSTIt is in an off state, the switch CMPRSTIt is in the conductive state；When the comparison
Sequential signal has original levels value.
The initial time for resetting operation is T0, and the end time for resetting operation is T01.The benchmark sampling step
Rapid initial time is T01, and the end time of the benchmark sampling step is T1.
In the benchmark sampling process, the switch CMPRSTIn the conductive state, such second compares input terminal VN
The current potential of node is equal to the first current potential for comparing input terminal VREF_BL, that is, is equal to original levels value.The benchmark sampling process
In, the capacitor C by column sense line BL current potential and second compare input terminal VN node current potential Difference Storage,
The potential difference at the both ends capacitor C is the difference of (VDD-Vm) and original levels value.
After carrying out the benchmark sampling, the switch CMP is disconnectedRST, make second to compare the current potential of input terminal VN node not
The current potential for being compared input terminal VREF_BL by first is influenced, and the switch CMP is disconnectedRSTThe step of it is complete to the T2 period in T1
At.
Disconnect the switch CMPRSTAfterwards, big as low as the first level value of the relatively clock signal is reduced.Reduce the ratio
Compared with clock signal big as low as the first level value the step of complete in T2 to T23 period.
The original levels value and the difference of first level value be equal to it is described compared with threshold value.
The relatively threshold value is 90 millivolts~110 millivolts, such as 100 millivolts, if the relatively threshold value is excessive, causes to detect
Sensitivity it is lower, if it is described relatively threshold value it is too small, blooming phenomenon may be judged by accident.
The relatively sampling step is completed in T23 to T3 period.
After benchmark sampling, and before the relatively sampling step, the selection transistor PGRSELIn leading
Logical state, the transmission transistor PGRSELIt is in an off state, the reset transistor PGRSTIt is in an off state, it is described to open
Close CMPRSTIt is in an off state.
In relatively sampling step, the signal of the column sense line BL sample and is coupled to second by capacitor C
Compare input terminal VN node, makes second to compare input terminal VN node with second electrical level value.Since capacitor C is by column sense line BL
Current potential and second compare input terminal VN node current potential Difference Storage, therefore, the current potential on the column sense line BL
Amplitude of variation with described second to compare the potential change amplitude of input terminal VN node consistent.Comparator 201 is to second electrical level value
After being compared with the first level value, output detection signal, the size of detection signal in this way characterizes second and compares input terminal VN
The amplitude of variation of node current potential, and the second amplitude of variation for comparing input terminal VN node current potential and the current potential on column sense line BL
Amplitude of variation it is consistent, therefore the size for detecting signal also characterizes the amplitude of variation of the current potential on column sense line BL indirectly.This
Sample to detect signal not by transistor threshold deviation each in pixel circuit and the influence of pixel power voltage fluctuation, makes
It obtains and the accuracy of the testing result of pixel blooming is improved.This improves the property of image sensor pixel circuit
Energy.
In the relatively sampling step, when second electrical level value is greater than the first level value, then the detection signal is " 0 ",
Blooming does not occur for expression；In the relatively sampling step, when second electrical level value is less than the first level value, the then detection
Signal is " 1 ", indicates that blooming occurs.
If the detection signal is " 0 ", the signal of described image data output end output is by the first image data
The signal of input terminal input is directly converted to, i.e., the signal of described image data output end output is directly by column sense line BL
Signal from analog signal be converted into digital signal and obtain；If the detection signal is " 1 ", described image data output end
The signal of output is set to the full scale data of analog-to-digital conversion module.
It is described when the signal of described image data output end output is set to the full scale data of analog-to-digital conversion module
The corresponding image of signal of image data output end output is shown as light tone.
By in Fig. 5 it is known that analog-to-digital conversion module 30 is respectively before transmission transistor TG conducting and transmission is brilliant
The step of data image signal acquisition twice has been carried out after body pipe TG conducting, second of data image signal and first obtained
The difference of the data image signal of secondary acquisition is the effective digital picture signal of respective pixel.
Although present disclosure is as above, present invention is not limited to this.Anyone skilled in the art are not departing from this
It in the spirit and scope of invention, can make various changes or modifications, therefore protection scope of the present invention should be with claim institute
Subject to the range of restriction.
Claims (10)
1. a kind of image sensor pixel circuit characterized by comprising
Pixel unit, the pixel unit include: column sense line；
Detection unit, the detection unit include: capacitor, and the capacitor has opposite first capacitor end and the second capacitance terminal,
First capacitor end is connect with the column sense line；Comparator, the comparator have first compare input terminal, second compare input
Output end is held and compares, second compares input terminal connect with the second capacitance terminal, and first, which compares input terminal, compares timing suitable for input
Signal；Switch, input terminal output end compared with connects the switch compared with second respectively.
2. image sensor pixel circuit according to claim 1, which is characterized in that the column sense line has opposite
First, which reads end and second, reads end；
The pixel unit further include: photodiode；Transmission transistor, the source level of the transmission transistor and the photoelectricity two
Pole pipe connection；Floating spreads point, and the floating diffusion point is connected with the drain electrode of the transmission transistor；Reset transistor, it is described
The source electrode of reset transistor and floating diffusion point connection, the drain electrode of the reset transistor are connect with power supply line；Amplification is brilliant
Body pipe, grid and floating the diffusion point connection of the amplifying transistor, the drain electrode of the amplifying transistor are connect with power supply line；Choosing
Transistor is selected, the drain electrode of the selection transistor is connect with the source level of the amplifying transistor；It is described first read end with it is described
The source level of selection transistor connects, and the second reading end is connect with first capacitor end.
3. image sensor pixel circuit according to claim 1, which is characterized in that further include: analog-to-digital conversion module, institute
Analog-to-digital conversion module is stated with the first image data input, the second image data input and image data output end, first
Image data input is connect with the column sense line, and second image data input output end compared with described connects,
Described image data output end is suitable for output digital image signal, and the data image signal is suitable for defeated according to the first image data
Enter the data of end input and the data acquisition of the second image data input input.
4. image sensor pixel circuit according to claim 3, which is characterized in that further include: image processing module, institute
It states image processing module to connect with described image data output end, described image processing module is suitable for the data image signal
Carry out noise reduction process.
5. a kind of working method of image sensor pixel circuit, which is characterized in that
Image sensor pixel circuit as described in claim 1 is provided；
The detection unit carries out benchmark sampling to the voltage of the column sense line, during carrying out the benchmark sampling,
The switch is in the conductive state；
After carrying out the benchmark sampling, the switch is disconnected；
After disconnecting the switch, big as low as the first level value of the relatively clock signal is reduced；
After reducing the relatively size of clock signal, it is compared sampling step；
The relatively sampling step includes: that second is sampled and be coupled to the signal of the column sense line to compare input terminal,
Second is set to compare input terminal with second electrical level value；After the comparator is compared second electrical level value and the first level value,
Output detection signal.
6. the working method of image sensor pixel circuit according to claim 5, which is characterized in that the column sense line
End and second, which is read, with opposite first reads end；The pixel unit further include: photodiode；Transmission transistor, institute
The source level for stating transmission transistor is connect with the photodiode；Floating spreads point, and the floating diffusion point and the transmission are brilliant
The drain electrode of body pipe connects；Reset transistor, the source electrode of the reset transistor and floating diffusion point connection, the reset are brilliant
The drain electrode of body pipe is connect with power supply line；Amplifying transistor, grid and floating the diffusion point connection of the amplifying transistor are described to put
The drain electrode of big transistor is connect with power supply line；Selection transistor, drain electrode and the amplifying transistor of the selection transistor
Source level connection；First reading end is connect with the source level of the selection transistor, and the second reading end is connect with first capacitor end；
The working method of described image sensor pixel circuit further include: in the detection unit to the voltage of the column sense line
Before carrying out benchmark sampling, reset operation is carried out；During reset operation, the selection transistor is on shape
State, the transmission transistor are in an off state, and the reset transistor is in the conductive state, and the switch is on shape
State, the relatively clock signal have original levels value, and the original levels value is greater than first level value；
In benchmark sampling step, the selection transistor is in the conductive state, and the transmission transistor is in an off state, institute
It states reset transistor to be in an off state, the switch is in the conductive state；The relatively clock signal has original levels value.
7. the working method of image sensor pixel circuit according to claim 6, which is characterized in that the original levels
Threshold value compared with value is equal to the difference of first level value, the relatively threshold value is 90 millivolts~110 millivolts.
8. the working method of image sensor pixel circuit according to claim 6, which is characterized in that adopted in the benchmark
After sample, and before the relatively sampling step, the selection transistor is in the conductive state, and the transmission transistor is in
Off-state, the reset transistor are in an off state, and the switch is in an off state.
9. the working method of image sensor pixel circuit according to claim 5, which is characterized in that adopted in the comparison
In sample step, when second electrical level value is greater than the first level value, then the detection signal is " 0 "；In the relatively sampling step,
When second electrical level value is less than the first level value, then the detection signal is " 1 ".
10. the working method of image sensor pixel circuit according to claim 9, which is characterized in that described image passes
Sensor pixel circuit further include: analog-to-digital conversion module, the analog-to-digital conversion module have the first image data input, the second figure
As data input pin and image data output end, the first image data input is connect with the column sense line, second figure
As data input pin output end connection compared with described, described image data output end is suitable for output digital image signal, described
The data of data and the input of the second image data input that data image signal is inputted according to the first image data input obtain
It takes；
If the detection signal is " 0 ", the signal of described image data output end output is inputted by the first image data
The signal of end input is directly converted to；If the detection signal is " 1 ", the signal quilt of described image data output end output
It is set to the full scale data of analog-to-digital conversion module.
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