CN107613179B - A kind of imaging sensor and its output circuit - Google Patents
A kind of imaging sensor and its output circuit Download PDFInfo
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- CN107613179B CN107613179B CN201710998803.4A CN201710998803A CN107613179B CN 107613179 B CN107613179 B CN 107613179B CN 201710998803 A CN201710998803 A CN 201710998803A CN 107613179 B CN107613179 B CN 107613179B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/50—Constructional details
- H04N23/54—Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/741—Circuitry for compensating brightness variation in the scene by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
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Abstract
A kind of imaging sensor and its output circuit, the output circuit include: ramp signal generative circuit, are suitable for output ramp voltage, and the ramp voltage changes linearly over time；Analog to digital conversion circuit accesses pixel voltage and ramp voltage from pixel array, obtains the pixel digital signals of the pixel voltage at the time of suitable for according to the pixel voltage and ramp voltage corresponding when equal；Control module provides the ramp voltage with Different Slope for the pixel voltage of odd-numbered line and even number line suitable for controlling the ramp signal generative circuit.Using technical solution of the present invention while realizing imaging sensor wide dynamic range, the complexity of control sequential is simplified.
Description
Technical field
The present invention relates to image sensor technologies field, in particular to a kind of imaging sensor and its output circuit.
Background technique
Imaging sensor is the important component of camera.Imaging sensor is realized by film in traditional camera
, and in modern digital cameras, imaging sensor is by complementary metal oxide semiconductor (Complementary Metal
Oxide Semiconductor, abbreviation CMOS) or charge coupled cell (Charge-coupled Device, abbreviation CCD)
Imaging sensor is realized.Pixel circuit is that imaging sensor realizes photosensitive core devices, usually may include realizing light
The photodiode of electricity conversion.It can also be transmission including a series of effects in imaging sensor, signal is converted and is amplified, control
Circuit module.In order to can obtain outstanding picture quality under strong light and weak light, researcher uses all may
Technology improve the dynamic range of image sensor pixel.
Currently, high-end cameras and mobile phone can provide high dynamic range (High Dynamic Range, abbreviation HDR)
Screening-mode can provide more dynamic ranges and image detail.Specific method is first to be absorbed based on the different time for exposure
The image of low-dynamic range (Low Dynamic Range, abbreviation LDR), corresponding to the time for exposure for recycling each LDR image
Best details synthesized, finally generate a HDR image.The advantages of this method is can preferably to reflect people true
Visual effect in environment；The disadvantage is that need to shoot multiframe (usually 3) image to synthesize the image of a high dynamic range,
And when for dynamic image shooting, in fact it could happen that the time interval of smudgy problem, different images shooting is also not easy
Control.
In order to overcome the problems referred above, it is shooting further by the way of the frame image based on shooting in the prior art
When, by controlling shutter pointer (shutter pointer), odd-numbered line and idol of the control for pixel array in imaging sensor
It is utilized respectively the different time for exposure several rows, obtains two width sub-frame images, two width sub-frame images are then utilized suitable algorithm
Merge, to realize that wide dynamic range is imaged.The disadvantages of the method are as follows the timing control to different exposure time is more complicated, also together
When bring bigger circuit scale and area.
Summary of the invention
Present invention solves the technical problem that being how while realizing imaging sensor wide dynamic range, when simplified control
The complexity of sequence.
In order to solve the above technical problems, the embodiment of the present invention provides a kind of output circuit of imaging sensor, the output
Circuit includes: ramp signal generative circuit, is suitable for output ramp voltage, and the ramp voltage changes linearly over time；Modulus turns
Circuit is changed, pixel voltage and ramp voltage from pixel array are accessed, is suitable for according to the pixel voltage and ramp voltage phase
The pixel digital signals corresponding to the pixel voltage are obtained at the time of correspondence whens equal；Control module is suitable for controlling the slope
Signal generating circuit provides the slope with Different Slope for the pixel voltage of odd-numbered line and even number line in the pixel array
Voltage.
Optionally, the ramp signal generative circuit includes: ramp generator, is suitable for output initial ramp voltage, described
Initial ramp voltage changes linearly over time；Gain circuitry, suitable for being put according to gain coefficient to the initial ramp voltage
Greatly.
Optionally, the control module is suitable for controlling the ramp generator for odd-numbered line and idol in the pixel array
Several rows of pixel voltage generates the different initial ramp voltage of slope, and controls the gain circuitry in the pixel array
The pixel voltage of odd-numbered line and even number line provides identical gain coefficient, so that the ramp signal generative circuit is for described
The pixel voltage of odd-numbered line and even number line provides the ramp voltage with Different Slope in pixel array.
Optionally, the control module is suitable for controlling the ramp generator for odd-numbered line and idol in the pixel array
Several rows of pixel voltage generates the identical initial ramp voltage of slope, and controls the gain circuitry in the pixel array
The pixel voltage of odd-numbered line and even number line provides different gain coefficients, so that the ramp signal generative circuit is for described
The pixel voltage of odd-numbered line and even number line provides the ramp voltage with Different Slope in pixel array.
Optionally, the gain circuitry includes: operational amplification circuit, feedback branch include the first sub- branch in parallel and
Second sub- branch, the first sub- branch include concatenated first switch and the first impedance, and the second sub- branch includes series connection
Second switch and the second impedance；Wherein, the switch shape that the control module passes through the control first switch and the second switch
State provides different gains to control the gain circuitry for the pixel voltage of odd-numbered line and even number line in the pixel array
Coefficient.
Optionally, odd-numbered line is identical with the time for exposure of even number line in the pixel array.
Optionally, the quantity of analog-digital conversion circuit as described is equal to the columns of the pixel array, each analog to digital conversion circuit
Distinguish at the time of corresponding when concurrently according to each pixel voltage and the equal ramp voltage in the every row of the pixel array
Obtain the pixel digital signals corresponding to each pixel voltage.
Optionally, the ramp voltage linear increment variation；Analog-digital conversion circuit as described includes: comparator, is suitable for institute
It states pixel voltage and ramp voltage is compared, to obtain comparison result；Counter accesses the comparison result, is suitable in institute
When stating the logic level overturning of comparison result, the count value output it is believed as the pixel number for corresponding to the pixel voltage
Number.
Optionally, the output circuit further include: digital processing module is suitable for respectively according to odd number in the pixel array
Row pixel digital signals corresponding with the pixel voltage of even number line obtain different sub-frame images information, and utilize described different
Sub-frame images information composograph information.
In order to solve the above technical problems, the embodiment of the present invention also provides a kind of imaging sensor, described image sensor packet
It includes: the output circuit of described image sensor；Pixel array, including the multiple pixel circuits being arranged in array, each pixel electricity
The output end on road exports corresponding pixel voltage.
Compared with prior art, the technical solution of the embodiment of the present invention has the advantages that
The output circuit of the imaging sensor of the embodiment of the present invention may include:
The embodiment of the present invention is by control ramp signal generative circuit for odd-numbered line and idol in the pixel array
The slope difference namely the voltage change amplitude of unit time of the ramp voltage of several rows of pixel voltage are different, to the picture
When the pixel voltage of odd-numbered line identical voltage value with even number line carries out analog-to-digital conversion in pixel array, different pixel numbers can be obtained
Signal therefore, can be corresponding according to the pixel voltage of odd-numbered line and even number line in the pixel array respectively in image procossing
Pixel digital signals obtain different sub-frame images information, and believed using the different sub-frame images information composograph
Breath, to realize that wide dynamic range is imaged.Due to corresponding only for the pixel voltage of odd-numbered line and even number line in the pixel array
The slope of ramp voltage controlled, thus, it is only required to for analog-digital conversion circuit as described to the picture of the odd-numbered line and even number
It when the conversion of plain voltage, is switched in two different control signals, is realizing imaging sensor wide dynamic range
While, enormously simplify the complexity of control sequential.
Furthermore, the pixel voltage of the odd-numbered line and even number line is by pixel array using the identical time for exposure
Time for exposure generate namely the photosensitive element in described image sensor in each pixel circuit is identical.Due in camera
In, the control for the above-mentioned time for exposure needs to realize that control strategy is complicated by control shutter pointer, therefore, in comparison,
The control sequential of this embodiment scheme is more succinct.
Furthermore, the quantity of analog-digital conversion circuit as described is equal to the columns of the pixel array, each analog-to-digital conversion
Circuit parallel according to each pixel voltage and the equal ramp voltage in the every row of the pixel array when it is corresponding at the time of
Respectively obtain the pixel digital signals of each pixel voltage.Compared to the fill factor that will affect pixel using Pixel-level ADC, make
The chip area for obtaining pixel array increases and chip-scale ADC need to carry out serial analog-to-digital conversion process, will affect analog-to-digital conversion
Speed, the column Parallel ADC structure that this embodiment scheme is formed, can fill factor to image sensor pixel and modulus turn
The processing speed changed is taken into account, to obtain more preferably image sensor performance.
Detailed description of the invention
Fig. 1 is that pixel voltage and noise are illustrated with the waveform that illuminance changes in a kind of imaging sensor in the prior art
Figure.
Fig. 2 is a kind of electrical block diagram of the output circuit of imaging sensor of the embodiment of the present invention.
Fig. 3 is the electrical block diagram of the output circuit of another imaging sensor of the embodiment of the present invention.
Fig. 4 is the circuit diagram of one of embodiment of the present invention gain circuitry.
Fig. 5 is the signal of one of embodiment of the present invention ramp voltage and the corresponding pixel digital signals of pixel voltage
Figure.
Fig. 6 is a kind of schematic diagram of the corresponding pixel digital signals of ramp voltage and pixel voltage in the prior art.
Fig. 7 is the electrical block diagram of the output circuit of another imaging sensor of the embodiment of the present invention.
Specific embodiment
As described in the background section, currently, using the frame image based on shooting, control is for picture in imaging sensor
The odd-numbered line and even number line of pixel array utilize the different time for exposure, obtain the method that two width sub-frame images merge again, In
While realizing the range of wide dynamic range imaging, timing control is excessively complicated.
Present inventor is studied and has been divided to the wide dynamic range realization for being directed to imaging sensor in the prior art
Analysis.
Firstly, imaging sensor need to be exposed when shooting image.So-called exposure is exactly that light is allowed to be radiated at photosensitive member
On part, it is set to generate a series of physicochemical change, to obtain a frame image.Specifically, it is passed when light is irradiated to image
When some pixel (namely photosensitive element in pixel circuit) on sensor, charge will be generated, charge number and the pixel
Received light is directly proportional.When end exposure, the charge of all pixels will be read on whole image sensor
It takes, is in general that pixel voltage is converted the charge to by capacitive device, use this by being converted into digital signal
The information of a little voltages generates image data.
In specific implementation, each pixel is corresponding for generating the image data voltage of image data in imaging sensor
Vsig_actualIt can be calculated using formula (1):
Wherein, tintIndicate time for exposure, IphotoIndicate the photoelectric current generated on photosensitive element in each pixel, CeffIt indicates
The capacitance of conversion capacitor for charge-voltage conversion, A indicates the gain of the gain adjusting circuit in imaging sensor, described
Gain adjusting circuit is suitable for carrying out gain adjustment by A to obtain described image data voltage V to the pixel voltagesig_actual。
Secondly, dynamic range (DynamicRange, abbreviation DR) is to characterize an important indicator of image sensor performance.
In general, the size of dynamic range is related to the ratio between saturation signal amount and noise.It is shown in the prior art referring to Fig. 1, Fig. 1
A kind of imaging sensor dynamic range and illuminance between relationship.In general, pixel voltage with illuminance increasing
Add and increases.However, when illuminance is lower and is maintained within a certain range, corresponding to the dark noise area in Fig. 1, noise size
It is constant, so that the dynamic range of imaging sensor is poor；And it is up to saturation when illuminance increases to a certain extent, correspond to
Saturation region in Fig. 1, at this point, the size of the pixel voltage no longer linearly increases, image sensing with the increase of illuminance
The dynamic range of device is also restricted.Based on above-mentioned analysis, two kinds are existed in the prior art based on the picture to imaging sensor
Plain circuit is improved to enhance the scheme of its dynamic range.
One of which be by pixel circuit with the concatenated transistor biasing of photosensitive element in subthreshold region so that described
The photoelectric current of photosensitive element output and the relationship exponent function relation of illuminance change.When the higher saturation into Fig. 1 of illuminance
Qu Shi, due to the index variation trend instead of conventional photoelectric current and illuminance at duplicate ratio variation tendency so that full
In the case where increasing unit illuminance in area, the variable quantity of photoelectric current increases, so that the pixel of pixel circuit output
Voltage increases, and can improve the dynamic range of imaging sensor to a certain extent.However in the pixel circuit in the program
The threshold voltage of transfer tube can drag down the pixel voltage, furthermore also suffer from the puzzlement of circuit non-linearity.
Wherein another is dual conversion gain (Dual Conversion Gain, abbreviation DCG) pixel circuit.Specifically,
Photosensitive element in the DCG pixel circuit generates charge, the quantity of the charge and the light when receiving light irradiation
Illuminance it is directly proportional, the charge via a DCG switch be coupled to conversion capacitor, thus output pixel voltage.Work as exterior light
When the illuminance of line is higher, the DCG switch conduction is controlled, so that the charge exports the picture according to the conversion capacitor
Plain voltage corresponds to the low conversion gain in DCG pixel circuit at this time；And when the illuminance of extraneous light is lower, control institute
DCG switch OFF is stated, so that the charge switchs the output of the parasitic capacitance in (specially transistor) institute according only to the DCG
Pixel voltage is stated, since the parasitic capacitance is much smaller than the conversion capacitor, therefore, is corresponded in DCG pixel circuit at this time
High-conversion-gain, to realize low circuit noise.Wherein, it can be recorded well by the pixel voltage data that high-gain is converted
Scene dark portion details, but be easy to reach saturation；And the pixel voltage data for passing through low gain conversion is not readily reachable by saturation, it can be with
Scene highlights details is recorded, preferably to improve the dynamic range of imaging sensor.However program pixel circuit needs additionally
DCG is arranged to switch, increases circuit area, influences the fill factor (fill factor) of imaging sensor；In addition, the circuit
Driver' s timing is sufficiently complex.
Therefore, the improvement abandoned to image element circuit structure is continued to bring out out in the prior art, but such as background technology part
It is described, it is synthesized using by multiple images or multiframe subgraph using algorithm appropriate, finally generates the image of a HDR,
However it is sufficiently complex on control strategy.
The embodiment of the present invention proposes a kind of output circuit of imaging sensor, is directed to by controlling ramp signal generative circuit
The pixel voltage of odd-numbered line and even number line provides the ramp voltage with Different Slope, so that in subsequent Digital Image Processing
Cheng Zhong can be obtained according to for the pixel digital signals corresponding to pixel voltage of odd-numbered line and even number line in pixel array respectively
Different sub-frame images information, and different sub-frame images information composograph information is utilized, image sensing not only can be improved
The dynamic range of device can also simplify the complexity of control sequential in imaging sensor.
It is understandable to enable above-mentioned purpose of the invention, feature and beneficial effect to become apparent, with reference to the accompanying drawing to this
The specific embodiment of invention is described in detail.
Fig. 2 is a kind of electrical block diagram of the output circuit of imaging sensor of the embodiment of the present invention.Fig. 2 shows
Output circuit 100 can be applied in imaging sensor (not shown).Specifically, the output circuit 100 of described image sensor
It may include ramp signal generative circuit 10, analog to digital conversion circuit 20 and control module 30.
In the present embodiment, the ramp signal generative circuit 10 is suitable for output ramp voltage VRamp, the ramp voltage
VRamp changes linearly over time.For example, the ramp voltage VRamp can become according to linear increment or the trend of linear decrease
Change.By taking linear increment changes as an example, it is assumed that ramp voltage VRamp linear change between 0~5V, namely with time shaft
Increase unit time length, the voltage value of the ramp voltage VRamp is consequently increased corresponding stepping, and the unit time is long
It spends corresponding stepping and indicates the slope that the ramp voltage VRamp changes linearly over time.Electricity is generated with the ramp signal
The system clock frequency used in road 10 is 100kHz (namely the time interval between every two timeticks is 10 μ s), described
Stepping be 19.5mV for, then the ramp voltage VRamp from 0 be changed to 5V needed for the time be about 2.56ms.
Analog-digital conversion circuit as described (or be analog-digital converter (Analog-to-Digital Converter, abbreviation
ADC)) 20 pixel voltage Pixout (i, k) and the ramp voltage VRamp of the access from pixel array 40.Art technology
Personnel understand, include the pixel circuit (not shown) being arranged in array in the pixel array 40 in imaging sensor, often
It include photosensitive element (being signal with the diode in scheming) in one pixel circuit.Assuming that the pixel array 40 is arranged with M row N
Pixel circuit, N are positive integer, and accordingly, each photosensitive element on the pixel array 40, will when receiving light irradiation
Photoelectric current (not shown) is generated, the photoelectric current will be converted into pixel voltage Pixout (i, k) inside the pixel circuit,
Wherein, 0≤i≤M, 0≤k≤N.
In the present embodiment, analog-digital conversion circuit as described 20 is suitable for according to the pixel voltage Pixout (i, k) and slope
Voltage VRamp obtains the pixel digital signals corresponding to the pixel voltage Pixout (i, k) at the time of correspondence when equal
ADCout (i, k), i and k are positive integer.For example, the pixel voltage Pixout (i, k) is 2.5V, the ramp voltage VRamp
Linear increment variation, when the two is equal, the ramp voltage VRamp can correspond to a moment on a timeline, also be
1.28ms after time beginning；For analog-digital conversion circuit as described 20, modulus is carried out to the pixel voltage Pixout (i, k)
It is a digital code that its corresponding pixel digital signals ADCout (i, k) is obtained after conversion, then under system clock effect, institute
Morning and evening at the time of stating corresponding when ramp voltage VRamp and the equal pixel voltage Pixout (i, k) corresponds to the pixel
The size of voltage Pixout (i, k), for example, can only be needed by the corresponding time interval of the system clock at the time of correspondence
Conversion obtains the digital code, for continuation is 2.5V with the pixel voltage Pixout (i, k), when itself and the ramp voltage
When VRamp is equal, it is the 1.28ms after initial time at the time of corresponding, is by the 1.28ms digital code obtained by weight of 10 μ s
128 namely binary one 0000000.
It should be noted that pixel digital signals ADCout (i, the k) s can convert to obtain in the manner described above, but
It is without being limited thereto, such as different conversion scales can also be used, the 1.28ms after the initial time is scaled other numbers
Code.What it is due to corresponding pixel digital signals ADCout (i, the k) carrying of each pixel voltage Pixout (i, k) is on a frame picture
Pixel Information, therefore, as long as above-mentioned pixel digital signals ADCout (i, k) and the pixel voltage Pixout (i, k) are in line
Sexual intercourse.
In one change case of the present embodiment, the ramp voltage VRamp can be according to the Long-term change trend of linear decrease, example
It such as, is 0V from 5V variation.In specific implementation, it can convert to obtain the pixel voltage Pixout first, in accordance with aforesaid way
Corresponding digital code at the time of corresponding when (i, k) and ramp voltage VRamp equal, then using the complement code of the digital code as the picture
Plain digital signal ADCout (i, k).
In another change case of the present embodiment, the ramp voltage VRamp can according to the Long-term change trend of linear increment, but
Do not change since 0V, for example, changing from 1V is 6V.In specific implementation, it can convert to obtain institute first, in accordance with aforesaid way
Corresponding digital code at the time of stating corresponding when pixel voltage Pixout (i, k) and ramp voltage VRamp equal, then described in the utilization
When pixel digital signals ADCout (i, k) carries out the processing of image composition algorithm, which is cut into biasing code corresponding with 1V.
In the present embodiment, the control module 30 is suitable for controlling the ramp signal generative circuit 10 for the pixel
(accordingly, k takes odd and even number to the pixel voltage Pixout (i, k) of odd-numbered line and even number line respectively, hereinafter no longer in array 40
Repeat) the ramp voltage VRamp with Different Slope is provided.
Furthermore, due in this embodiment scheme, controlling the ramp signal generative circuit 10 for the pixel
The slope difference namely unit of the ramp voltage VRamp of the pixel voltage Pixout (i, k) of odd-numbered line and even number line in array 40
The voltage change amplitude of time is different, the pixel voltage of odd-numbered line identical voltage value with even number line in the pixel array 40
When Pixout (i, k) carries out analog-to-digital conversion, different pixel digital signals ADCout (i, k) can be obtained.It, can in image procossing
To be believed respectively according to the corresponding pixel number of the pixel voltage Pixout (i, k) of odd-numbered line and even number line in the pixel array 40
Number ADCout (i, k) obtains different sub-frame images information, and utilizes the different sub-frame images information composograph information,
To realize that wide dynamic range is imaged.Due to the pixel voltage Pixout only for odd-numbered line and even number line in the pixel array 40
The slope of (i, k) corresponding ramp voltage VRamp is controlled, thus, it is only required to for analog-digital conversion circuit as described 20 to described
The conversion of the pixel voltage Pixout (i, k) of odd-numbered line and even number switches in two different control signals, In
While realizing imaging sensor wide dynamic range, the complexity of control sequential is enormously simplified.
Referring to Fig. 3, in the present embodiment, the ramp signal generative circuit 10 may include ramp generator 101 and increase
Beneficial circuit 102.
Wherein, the ramp generator 101 is suitable for output initial ramp voltage VRampRaw, the initial ramp voltage
VRampRaw changes linearly over time.The gain circuitry 102 is suitable for according to gain coefficient (being set as G) to the initial ramp electricity
Pressure amplifies, to obtain the ramp voltage VRamp namely ramp voltage VRamp equal to the initial ramp voltage
The product of VRampRaw and the gain coefficient G.
In the present embodiment, the control module 30 is suitable for controlling the ramp generator 101 for the pixel array
The pixel voltage Pixout (i, k) of odd-numbered line and even number line generates the different initial ramp voltage VRampRaw of slope in 40, and
The gain circuitry 102 is controlled to mention for the pixel voltage Pixout (i, k) of odd-numbered line and even number line in the pixel array 40
For identical gain coefficient G, so that the ramp signal generative circuit 10 is for odd-numbered line and idol in the pixel array 40
Several rows of pixel voltage Pixout (i, k) provides the ramp voltage VRamp with Different Slope.
In one change case of the present embodiment, the control module 30 is suitable for controlling the ramp generator 101 for described
The pixel voltage Pixout (i, k) of odd-numbered line and even number line generates the identical initial ramp voltage of slope in pixel array 40
VRampRaw, and the gain circuitry 102 is controlled for the pixel voltage of odd-numbered line and even number line in the pixel array 40
Pixout (i, k) provides different gain coefficient G, so that the ramp signal generative circuit 10 is directed to the pixel array 40
The pixel voltage Pixout (i, k) of middle odd-numbered line and even number line provides the ramp voltage VRamp with Different Slope.
In another change case of the present embodiment, the control module 30 can also control the ramp generator 101 and be directed to
The pixel voltage Pixout (i, k) of odd-numbered line and even number line generates the different initial ramp voltage of slope in the pixel array 40
VRampRaw, and the gain circuitry 102 is controlled for the pixel voltage of odd-numbered line and even number line in the pixel array 40
Pixout (i, k) provides different gain coefficient G, so that the ramp signal generative circuit 10 is directed to the pixel array 40
The pixel voltage Pixout (i, k) (hereinafter referred odd-numbered line and even number line) of middle odd-numbered line and even number line, which is provided, has Different Slope
Ramp voltage VRamp.
In the present embodiment, the variation tendency of the initial ramp voltage VRampRaw and with the pixel voltage
The acquisition modes of the corresponding pixel digital signals ADCout (i, k) of Pixout (i, k) refer to above to the ramp voltage
The associated description of VRamp, it will not go into details herein.
Together referring to Fig. 3 and Fig. 4, in specific implementation, the gain circuitry 102 may include operational amplification circuit (figure
In do not indicate).The operational amplification circuit can be realized using operational amplifier (abbreviation amplifier) and peripheral circuit.This field skill
Art personnel understand that the operational amplification circuit includes to input branch and feedback branch, described in the input branch access
Initial ramp voltage VRampRaw；One of input terminal of the amplifier accesses reference voltage VREF, the reference voltage
VREF is used to adjust the bias voltage of the ramp voltage VRamp；The gain coefficient G of the gain circuitry 102 depends on described
The impedance magnitude of feedback branch and input branch.
In the present embodiment, the feedback branch (not indicating in figure) of the operational amplification circuit includes the first sub- branch in parallel
(not indicating in figure) and the second sub- branch (not indicating in figure), the first sub- branch include concatenated first switch S1 and first
Impedance Z fb1, the second sub- branch include concatenated second switch S2 and the second impedance Z fb2.Wherein, the control module 30
The gain circuitry 102 is controlled for the pixel by controlling the switch state of the first switch S1 and second switch S2
The pixel voltage Pixout (i, k) of odd-numbered line and even number line provides different gain coefficient G in array 40.Specifically, Ke Yishe
The of different sizes of the first impedance Z fb1 and the second impedance Z fb2 is set, for the odd-numbered line and even number line, corresponds to first
A conducting in switch S1 and second switch S2；Also it is identical that two impedance magnitudes can be set, for the odd-numbered line and even number
Row is both turned on corresponding to a conducting and two；It can also adopt and be realized with other appropriate means, it will not go into details herein.
It is understood to one skilled in the art that in specific implementation, the first switch S1 and second switch S2 can be
The semiconductor switch devices such as metal-oxide-semiconductor or triode, the control module 30 can be by opening the first switch S1 and second
It closes S2 and applies logic high or logic low to control their switch state, but not limited to this, two switches are also possible to
The switch element of routine or the integrated switch for being packaged in chip.
It should be noted that " logic high " and " logic low " herein is opposite logic level.Wherein,
" logic high " refers to can be identified as that the level range of digital signal " 1 ", " logic low " refer to be identified
For the level range of digital signal " 0 ", specific level range is simultaneously not particularly limited.
In specific implementation, the first impedance Z fb1 and the second impedance Z fb2 can be the impedance example of any appropriate form
Capacitor as illustrated in the diagram perhaps for resistance or can also can also be the combination of other capacitors, inductance, resistance, herein not
An another citing.
In specific implementation, it can also be adjusted by the impedance magnitude to the input branch, or colleague is to institute
The mode that is adjusted of impedance magnitude for stating input branch and feedback branch adjusts the odd-numbered line and even number line is corresponding described
The gain coefficient G of gain circuitry 102.
It should be noted that the gain circuitry 102 is not limited to above-mentioned operational amplification circuit, can also be by working in
The passive element (such as the semiconductor switch devices such as metal-oxide-semiconductor or triode) and switch of magnifying state are realized.
It should also be noted that, the ramp signal generative circuit 10 is not limited to above-mentioned include 101 He of ramp generator
The scheme of gain circuitry 102, can also comprise only ramp generator 101, and the control module 30 is directed to the odd-numbered line
The ramp generator 101, which is controlled, with even number line exports the initial ramp voltage VRampRaw, described ramp voltage VRamp etc.
In the initial ramp voltage VRampRaw.
In this embodiment, it is preferred that odd-numbered line is identical with the time for exposure of even number line in the pixel array 40.
That is, the time for exposure that the photosensitive element in described image sensor in each pixel circuit receives is identical.Due in the camera, needle
The control of above-mentioned time for exposure is needed to realize by control shutter pointer (shutter pointer), control strategy is complicated, because
This, for this embodiment scheme while realizing imaging sensor wide dynamic range, control sequential is succinct.
With continued reference to Fig. 3, it is further preferred that the quantity of analog-digital conversion circuit as described 20 is equal to described in the present embodiment
The columns N of pixel array 40, each analog to digital conversion circuit 20 is concurrently according to each pixel in the every row of the pixel array 40
It respectively obtains at the time of corresponding when voltage Pixout (i, k) and the ramp voltage VRamp equal corresponding to each pixel voltage
The pixel digital signals ADCout (i, k) of Pixout (i, k).
Furthermore, it is all made of compared to using Pixel-level ADC, namely for each pixel voltage Pixout (i, k)
One ADC will affect the fill factor of pixel, and the chip area of pixel array 40 increases and chip-scale ADC, namely all
Pixel voltage Pixout (i, k) shares an ADC, and carrying out serial analog-to-digital conversion process will affect the speed of analog-to-digital conversion, this reality
The quantity for applying the analog to digital conversion circuit 20 in example is equal to the columns N of the pixel array 40 (namely forming column Parallel ADC structure),
Can the processing speed of fill factor and analog-to-digital conversion to image sensor pixel take into account, to obtain more preferably image
Sensor performance.
As a unrestricted example, the ramp voltage VRamp in the present embodiment can linear increment variation；Institute
Stating analog to digital conversion circuit 20 may include comparator 201 and counter 202.
Specifically, the comparator 201 be suitable for the pixel voltage Pixout (i, k) and ramp voltage VRamp into
Row compares, to obtain comparison result (not indicating in figure)；The counter 202 accesses the comparison result, is suitable in the ratio
Relatively result logic level overturning (such as from logic high overturning be logic low, or vice versa) when, the meter that outputs it
Numerical value is used as the pixel digital signals ADCout (i, k) corresponding to the pixel voltage Pixout (i, k).
Since the logic level overturning of the comparison result means the pixel voltage Pixout (i, k) and ramp voltage
VRamp is equal or close to equal, and therefore, when not overturning, the pixel voltage Pixout (i, k) is less than the ramp voltage
VRamp, and when overturning, the pixel voltage Pixout (i, k) is more than or equal to the ramp voltage VRamp.Due to identical
Under system clock effect, while the ramp voltage VRamp linear increment, the counter 202 is counted, therefore, described
Count value when the logic level overturning of comparison result can characterize the size of the pixel voltage Pixout (i, k).
The above-mentioned course of work may refer to Fig. 5.Fig. 5 shows the slope electricity of the Different Slope for odd-numbered line and even number line
VRamp is pressed, is indicated respectively with odd-numbered line VRamp and even number line VRamp in figure；And show to the odd-numbered line of same magnitude and
The pixel voltage Pixout (i, k) of even number line carries out the processing result of analog-to-digital conversion.It can be seen from the figure that turning in above-mentioned modulus
It changes under the action of circuit 20 (referring to Fig. 3), obtained odd-line pixels digital signal ADCout (i, k) and even rows number
Signal ADCout (i, k) (being indicated in figure with odd-numbered line ADCout (i, k) and even number line ADCout (i, k)) is different.
Contrastingly, Fig. 6 is a kind of corresponding pixel digital signals of ramp voltage and pixel voltage in the prior art
Schematic diagram.Prior art can also be using the analog to digital conversion circuit 20 (referring to Fig. 3) in this embodiment scheme, from Fig. 6
As can be seen that using the different time for exposure to the odd-numbered line and even number line when using identical ramp voltage VRamp
When, for example, odd-numbered line is longer, the pixel voltage Pixout (i, k) of odd-numbered line and even number line under the same terms is (in figure respectively
Indicated with odd-numbered line VRamp and even number line VRamp) it is different, and available odd-line pixels digital signal ADCout (i,
K) and even rows digital signal ADCout (i, k) (in figure with odd-numbered line ADCout (i, k) and even number line ADCout (i,
K) indicate) it is different.However, the program when controlling the time for exposure difference of the odd-numbered line and even number line, control strategy is multiple
It is miscellaneous.
Fig. 7 is the electrical block diagram of the output circuit of another imaging sensor of the embodiment of the present invention.
Output circuit 200 and the structure and working principle of previously described output circuit 100 shown in Fig. 7 is almost the same,
Its main distinction is that the output circuit 200 can further include digital processing module 50.Wherein, at the number
Module 50 is managed suitable for corresponding according to the pixel voltage Pixout (i, k) of odd-numbered line and even number line in the pixel array 40 respectively
Pixel digital signals ADCout (i, k) obtains different sub-frame images information, and is closed using the different sub-frame images information
At image information.
The embodiment of the invention also discloses a kind of imaging sensor, which may include above-mentioned Fig. 2, Fig. 3, figure
The output circuit 100 of imaging sensor shown in any of 3 and 4 or the output circuit of imaging sensor shown in Fig. 7
200 and pixel array 40.More information about the pixel array 40 refers to the description of embodiment above, herein not
It repeats again.
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 (6)
1. a kind of output circuit of imaging sensor characterized by comprising
Ramp signal generative circuit, is suitable for output ramp voltage, and the ramp voltage changes linearly over time；
Analog to digital conversion circuit, access pixel voltage and ramp voltage from pixel array, be suitable for according to the pixel voltage with
The pixel digital signals corresponding to the pixel voltage are obtained at the time of correspondence when ramp voltage is equal；
Control module, suitable for controlling the ramp signal generative circuit for the picture of odd-numbered line and even number line in the pixel array
Plain voltage provides the ramp voltage with Different Slope；
Wherein, the ramp signal generative circuit includes:
Ramp generator, is suitable for output initial ramp voltage, and the initial ramp voltage changes linearly over time；
Gain circuitry, suitable for being amplified according to gain coefficient to the initial ramp voltage；
Wherein, the control module is suitable for controlling the ramp generator for odd-numbered line in the pixel array and even number line
Pixel voltage generates the different initial ramp voltage of slope, and controls the gain circuitry for odd-numbered line in the pixel array
Identical gain coefficient is provided with the pixel voltage of even number line, so that the ramp signal generative circuit is directed to the pixel battle array
The pixel voltage of odd-numbered line and even number line provides the ramp voltage with Different Slope in column.
2. output circuit according to claim 1, which is characterized in that the exposure of odd-numbered line and even number line in the pixel array
It is identical between light time.
3. output circuit according to claim 2, which is characterized in that the quantity of analog-digital conversion circuit as described is equal to the picture
The columns of pixel array, each analog to digital conversion circuit concurrently according in the every row of the pixel array each pixel voltage with it is described
The pixel digital signals corresponding to each pixel voltage are respectively obtained at the time of correspondence when ramp voltage is equal.
4. output circuit according to claim 1, which is characterized in that the ramp voltage linear increment variation；The mould
Counting conversion circuit includes:
Comparator, suitable for being compared to the pixel voltage and ramp voltage, to obtain comparison result；
Counter accesses the comparison result, suitable for the counting in the logic level overturning of the comparison result, output it
It is worth as the pixel digital signals for corresponding to the pixel voltage.
5. output circuit according to any one of claim 1 to 4, which is characterized in that further include:
Digital processing module, suitable for respectively according to the corresponding pixel of the pixel voltage of odd-numbered line and even number line in the pixel array
Digital signal obtains different sub-frame images information, and utilizes the different sub-frame images information composograph information.
6. a kind of imaging sensor characterized by comprising
The output circuit of imaging sensor described in any one of claims 1 to 5；
Pixel array, including the multiple pixel circuits being arranged in array, the output end of each pixel circuit exports corresponding pixel
Voltage.
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| KR102469071B1 (en) * | 2018-02-06 | 2022-11-23 | 에스케이하이닉스 주식회사 | Comparator, and cmos image sensor thereof |
| CN109040608B (en) * | 2018-08-20 | 2020-07-03 | 昆山晔芯电子科技有限公司 | Single-frame high-dynamic-range imaging method and system |
| CN109886260B (en) * | 2019-02-27 | 2024-02-02 | 上海千映智能科技有限公司 | Intelligent code reader |
| WO2020252754A1 (en) | 2019-06-20 | 2020-12-24 | 深圳市汇顶科技股份有限公司 | Readout circuit, image sensor and electronic device |
| CN110390317B (en) * | 2019-07-30 | 2024-06-25 | 上海思立微电子科技有限公司 | Pixel circuit, pixel array and optical fingerprint sensor |
| CN112511772B (en) * | 2020-10-28 | 2024-06-04 | 深圳奥辰光电科技有限公司 | Image sensor, method for enhancing linearity of image sensor and depth camera |
| CN113382175B (en) * | 2021-06-09 | 2022-12-27 | 上海矽印科技有限公司 | High-gain pixel design method |
| CN113709333B (en) * | 2021-07-21 | 2023-07-11 | 维沃移动通信有限公司 | Image sensor |
| CN114173070A (en) * | 2021-11-23 | 2022-03-11 | 深圳锐视智芯科技有限公司 | Difference image sensor with digital pixel storage |
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| CN1770831A (en) * | 2004-07-16 | 2006-05-10 | 索尼株式会社 | Data processing method, data processing apparatus, semiconductor device for detecting physical quantity distribution, and electronic equipment |
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| CN1770831A (en) * | 2004-07-16 | 2006-05-10 | 索尼株式会社 | Data processing method, data processing apparatus, semiconductor device for detecting physical quantity distribution, and electronic equipment |
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