CN204031312U - The image sensor pixel of variable conversion gain - Google Patents
The image sensor pixel of variable conversion gain Download PDFInfo
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- CN204031312U CN204031312U CN201420482170.3U CN201420482170U CN204031312U CN 204031312 U CN204031312 U CN 204031312U CN 201420482170 U CN201420482170 U CN 201420482170U CN 204031312 U CN204031312 U CN 204031312U
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Abstract
The utility model discloses a kind of image sensor pixel of variable conversion gain, comprise the first photodiode, charge pass transistor, the first reset transistor, the source that are placed in semiconductor substrate and follow transistor, select transistor, floating active area, the second photodiode, the second reset transistor, electric capacity, switching transistor; The drain electrode end of switching transistor is connected with described floating active area, and source terminal is extremely connected with one of described electric capacity, and gate terminal is connected with described second photodiode; Another of electric capacity is extremely connected with floating active area; The source terminal of the second reset transistor is connected with described second photodiode, and drain electrode end is connected with power supply.Adopt the opto-electronic conversion gain of sensor pixel when reducing high lighting environment to reach the object postponing pixel saturation time, solve the information in kind that prior art not easily gathers outdoor high lighting environment, thus the image quality that lifting imageing sensor exports.
Description
Technical field
The utility model relates to a kind of image sensor pixel, particularly relates to a kind of image sensor pixel of variable conversion gain.
Background technology
Imageing sensor has been widely used in digital camera, cell phone, medicine equipment, automobile and other application scenarios.Particularly manufacture the fast development of CMOS (CMOS (Complementary Metal Oxide Semiconductor)) image sensor technologies, make the output image quality of people to imageing sensor have higher requirement.
In the prior art, cmos image sensor generally adopts the dot structure of linear photoconductor response function.As shown in Figure 1, be cmos image sensor pixel, in the art also referred to as 4T (four transistors) active pixel.The components and parts of 4T active pixel comprise: photodiode 101, charge pass transistor 102, reset transistor 103, and transistor 104 and row selecting transistor 105 are followed in source, and row bit line 106; VTX is the gate terminal of transistor 102, and VRX is the gate terminal of transistor 103, and VSX is the gate terminal of transistor 105, and FD is floating active area, and Vdd is supply voltage.Photodiode 101 receives extraneous incident light, produces photosignal; Turn-on transistor 102, after the photosignal in photodiode is transferred to FD district, the FD potential well built-in potential variable signal detected by transistor 104 reads through 106 and preserves.Wherein, the photo-electric charge amount in FD district is directly proportional to incident illumination amount, and in FD potential well, the change of photo-electric charge amount is detected by transistor 104 and is converted to potential change, and the amount that photo-electric charge is converted to electromotive force is called opto-electronic conversion gain; During the change of photo-electric charge amount, conversion gain remains unchanged, then the electric potential signal that detects at FD place of transistor 104 is also proportional with the quantity of illumination.
The photoelectric respone of such imageing sensor is linear, in this area, be called as linear transducer.Out of doors in environment, linear transducer not easily collects the information in kind of high lighting environment, thus reduces the output image quality of transducer.
Utility model content
The purpose of this utility model is to provide the image sensor pixel that a kind of output image quality is high, be applicable to the variable conversion gain of outdoor high lighting environment.
The purpose of this utility model is achieved through the following technical solutions:
The image sensor pixel of variable conversion gain of the present utility model, comprise the first photodiode, charge pass transistor, the first reset transistor, the source that are placed in semiconductor substrate to follow transistor, select transistor, floating active area, it is characterized in that, also comprise the second photodiode, the second reset transistor, electric capacity, the switching transistor that are placed in semiconductor substrate;
The drain electrode end of described switching transistor is connected with described floating active area, and source terminal is extremely connected with one of described electric capacity, and gate terminal is connected with described second photodiode;
Another of described electric capacity is extremely connected with floating active area;
The source terminal of described second reset transistor is connected with described second photodiode, and drain electrode end is connected with power supply.
The technical scheme provided as can be seen from above-mentioned the utility model, the image sensor pixel of the variable conversion gain that the utility model embodiment provides, owing to being connected to the second photodiode, the second reset transistor, electric capacity, switching transistor in floating active area, the opto-electronic conversion gain of sensor pixel when reducing high lighting environment is adopted to reach the object postponing pixel saturation time, solve the information in kind that prior art not easily gathers outdoor high lighting environment, thus promote the image quality of imageing sensor output.Be particularly suitable for outdoor high lighting environment.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of the cmos image sensor pixel of prior art.
Fig. 2 is the circuit diagram of the image sensor pixel of the variable conversion gain that the utility model embodiment provides.
Fig. 3 is the sequencing control schematic diagram of the image sensor pixel work of the variable conversion gain that the utility model embodiment provides.
Fig. 4 is the image sensor pixel of the variable conversion gain that the utility model embodiment provides circuit diagram when being operated in low light environment.
Fig. 5 is the image sensor pixel of the variable conversion gain that the utility model embodiment provides circuit diagram when being operated in strong light environment.
Fig. 6 is the potential well schematic diagram of the image sensor pixel work of the variable conversion gain that the utility model embodiment provides.
Embodiment
To be described in further detail the utility model embodiment below.
The image sensor pixel of variable conversion gain of the present utility model, its preferably embodiment be:
Comprise the first photodiode, charge pass transistor, the first reset transistor, the source that are placed in semiconductor substrate to follow transistor, select transistor, floating active area, also comprise the second photodiode, the second reset transistor, electric capacity, the switching transistor that are placed in semiconductor substrate;
The drain electrode end of described switching transistor is connected with described floating active area, and source terminal is extremely connected with one of described electric capacity, and gate terminal is connected with described second photodiode;
Another of described electric capacity is extremely connected with floating active area;
The source terminal of described second reset transistor is connected with described second photodiode, and drain electrode end is connected with power supply.
Described first photodiode is N-type photodiode, and described second photodiode is N-type photodiode.
Described charge pass transistor, the first reset transistor, the second reset transistor, switching transistor, source are followed transistor and are selected transistor to be N-type transistor.
Described electric capacity is metal electric perhaps transistor capacitance.
The threshold voltage of described second reset transistor is-0.2V ~ 0.3V.
The threshold voltage of described switching transistor is 0V ~ 0.5V.
Described second photodiode can not be completely depleted.
The capacitance of described electric capacity is 0.5fF ~ 8fF.
The method of work of the image sensor pixel of variable conversion gain of the present utility model, comprises step:
A, pixel-reset operate, and do the operation of unlatching first reset transistor, charge pass transistor, the second reset transistor, are removed by the electric charge in the first photodiode, the second photodiode;
Before b, pixel exposure terminate, do the operation of a floating active area of reset, namely do the operation of unlatching first reset transistor, the electric charge of floating active area is removed, is set to high potential;
After c, floating active area reset operation complete, do the reset signal operation of read pixel;
After the reset signal end of operation of d, read pixel, do the operation of opening charge pass transistor, the photo-electric charge in the first photodiode is transferred to floating active area.
After photo-electric charge in e, the first photodiode transfers to floating active area, do the photosignal operation of read pixel.
The image sensor pixel of variable conversion gain of the present utility model, the opto-electronic conversion gain of sensor pixel when reducing high lighting environment is adopted to reach the object postponing pixel saturation time, solve the information in kind that prior art not easily gathers outdoor high lighting environment, thus promote the image quality of imageing sensor output.Be particularly suitable for outdoor high lighting environment.
The utility model is started with from the photoelectric respone character improving 4T pixel, reduce luminous sensitivity during high lighting environment, postpone the saturation time of pixel, to reach the object of the detailed information in kind of the how high illumination of transducer collection, thus promote the image quality of transducer output.During low light irradiation, switching transistor conducting, described electric capacity can not join floating active area, and the opto-electronic conversion gain of pixel is high; During strong illumination, switching transistor cuts out, and described electric capacity joins floating active area, and the opto-electronic conversion gain of pixel is low.The saturation time of effective imageing sensor when having postponed high illumination, more detailed information in kind when transducer collects high illumination, effectively improves the image quality that imageing sensor exports.
Specific embodiment:
The basis of the image sensor pixel of prior art introduces special device architecture to floating active area, and as shown in Figure 2,101 ~ 106 is the image sensor pixel device of prior art, and VTX, VRX, VSX are respectively the gate terminal of 102,103,105; 201 is the second photodiode, and 202 is switching transistor, and 203 is electric capacity, and 204 is the second reset transistor, and PD is the gate terminal of 202, CD be 203 one extreme, Vdd is power supply, and Vct is the gate terminal of 204.As shown in Figure 2, the charge-trapping end of 201 is connected with PD, and the source terminal of 204 is connected with PD, and the drain electrode end of 204 is connected with Vdd; The drain electrode end of 202 is connected with FD, and the source terminal of 202 is connected with CD; Another of 203 is extremely connected with FD.Wherein, 101 and 201 is N-type photodiode, and 102 ~ 105,202,204 is N-type transistor; 202 and 204 is Low threshold transistor, the threshold voltage 0V ~ 0.5V of 202, and the threshold voltage of 204 is-0.2V ~ 0.3V; Photodiode 101 can exhaust completely, but photodiode 201 can not be completely depleted, and namely the electromotive force of charge collection region of 201 can reach 204 drain electrode end electromotive forces.Described electric capacity 203 can be transistor capacitance, also can be metal capacitance, and the scope of 203 capacitances is 0.5fF ~ 8fF.
The sequencing control schematic diagram of cmos image sensor pixel operation of the present utility model, as shown in Figure 3.In Fig. 3, respectively illustrate 102,103,204 transistor gate voltage VTX, VRX, Vct sequencing control figure, SH sequential characterizes the operation of reading signal.When described VRX, VTX, Vct are high level, represent the operation of opening respective transistor, during low level, represent closedown respective transistor; SH represents the operation of reading signal when being high level pulse.In order to clearly state feature of the present utility model, other sequential, as not shown in VSX sequential.
The method of work of the utility model pixel is expressed as follows:
First, carry out pixel-reset operation, do the operation 204 of unlatching first reset transistor 103, charge pass transistor 102, second reset transistor, the electric charge in the first photodiode 101, second photodiode 201 is removed; As shown in Figure 3,301 operate for VRX is set to high level, namely open the operation of 103; 302 operate for VTX is set to high level, namely open the operation of 102; 303 operate for Vct is set to high level, namely open the operation of 204.
Further, before pixel exposure terminates, do the operation of a floating active area of reset, namely do the operation of unlatching first reset transistor 103, the electric charge of floating active area is removed, is set to high potential; As shown in Figure 3,304 operate for VRX is set to high level, namely open the operation of 103.
Further, after floating active area reset operation completes, do the reset signal operation of read pixel; As shown in Figure 3,305 high level pulses represent the operation of read reset signal shr.
Further, after the reset signal end of operation of read pixel, do the operation of opening charge pass transistor 102, the photo-electric charge in the first photodiode 101 is transferred to floating active area.As shown in Figure 3,306 operate for VTX is set to high level, namely open the operation of 102.
Further, after the photo-electric charge in the first photodiode 101 transfers to floating active area, do the photosignal operation of read pixel; As shown in Figure 3,307 high level pulses represent the operation of reading photosignal shs.
The actual image signal of described image sensor pixel is the difference signal of shs and shr signal.
In order to more clearly state feature of the present utility model, set forth the operation principle of the utility model pixel below in conjunction with the utility model embodiment.Pixel characteristic of the present utility model is, reduces the opto-electronic conversion gain under strong light environment, is realized by the total capacitance value adjusting floating active area, illustrates below for floating active area electric capacity situation when reading photosignal shs.Pixel operation of the present utility model is under low light environment, and the electric charge that photodiode 201 is collected when end exposure is few, and connected 202 gate terminal electromotive forces are high, then 202 be in opening, as shown in Figure 4.In Fig. 4,402 expressions 202 are in the state of unlatching, then CD and FD is communicated with, electric capacity 203 actual effect.Namely when pixel is subject to low light irradiation, the two poles of the earth of electric capacity 203 are all connected with FD, and now electric capacity 203 can not join the total capacitance of FD.
Pixel operation of the present utility model is under strong light environment, and the electric charge that photodiode 201 is collected when end exposure is many, and connected 202 gate terminal electromotive forces are low, then 202 be in closed condition, as shown in Figure 5.In Fig. 5,502 expressions 202 are in the state of closedown, then CD and FD is not communicated with, and electric capacity 203 is effective.Namely when pixel is subject to strong illumination, one of electric capacity 203 is extremely connected with FD, and another extreme CD is independent, and also maintenance and FD disconnect.Now, electric capacity 203 joins the total capacitance of FD.
The pixel operative status of above-mentioned Fig. 4 and Fig. 5, the electric capacity potential well situation of FD as shown in Figure 6.In Fig. 6,601 is the potential well of photodiode 101, and 602 is FD parasitic capacitance potential well, and 603 is the electric capacity potential well of electric capacity 203, and 102 are in closed condition, and Vreset is the reset potential of FD.The FD electric capacity of the pixel operative status shown in Fig. 4 is only 602 parts, and this electric capacity is Cfd, and now FD electric capacity is low, and the opto-electronic conversion gain of pixel is high, and luminous sensitivity is high; The FD electric capacity of the pixel operative status shown in Fig. 5 be the Ccap of the Cfd and 603 of 602 two-part and, FD electric capacity is now high, and the opto-electronic conversion gain of pixel is low, and luminous sensitivity is low.The photosensitive pixel signal that the utility model pixel is expanded is 603 parts, and the semaphore of expansion is directly proportional to Ccap value, and this part signal has expanded the photosensitive dynamic range of pixel, and transducer acquires the detailed information in kind of how high illumination.Therefore, the utility model pixel effectively improves the image quality that transducer exports.
The above; be only the utility model preferably embodiment; but protection range of the present utility model is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the utility model discloses; the change that can expect easily or replacement, all should be encompassed within protection range of the present utility model.Therefore, protection range of the present utility model should be as the criterion with the protection range of claims.
Claims (4)
1. the image sensor pixel of a variable conversion gain, it is characterized in that, comprise the first photodiode, charge pass transistor, the first reset transistor, the source that are placed in semiconductor substrate to follow transistor, select transistor, floating active area, it is characterized in that, also comprise the second photodiode, the second reset transistor, electric capacity, the switching transistor that are placed in semiconductor substrate;
The drain electrode end of described switching transistor is connected with described floating active area, and source terminal is extremely connected with one of described electric capacity, and gate terminal is connected with described second photodiode;
Another of described electric capacity is extremely connected with floating active area;
The source terminal of described second reset transistor is connected with described second photodiode, and drain electrode end is connected with power supply.
2. the image sensor pixel of variable conversion gain according to claim 1, is characterized in that, described first photodiode is N-type photodiode, and described second photodiode is N-type photodiode.
3. the image sensor pixel of variable conversion gain according to claim 1, it is characterized in that, described charge pass transistor, the first reset transistor, the second reset transistor, switching transistor, source are followed transistor and are selected transistor to be N-type transistor.
4. the image sensor pixel of variable conversion gain according to claim 1, is characterized in that, described electric capacity is metal electric perhaps transistor capacitance.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420482170.3U CN204031312U (en) | 2014-08-25 | 2014-08-25 | The image sensor pixel of variable conversion gain |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201420482170.3U CN204031312U (en) | 2014-08-25 | 2014-08-25 | The image sensor pixel of variable conversion gain |
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| CN204031312U true CN204031312U (en) | 2014-12-17 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104135633A (en) * | 2014-08-25 | 2014-11-05 | 北京思比科微电子技术股份有限公司 | Image sensor pixel with changeable conversion gain and working method thereof |
| CN110072069A (en) * | 2018-01-23 | 2019-07-30 | 三星电子株式会社 | Imaging sensor |
| US11658193B2 (en) | 2018-01-23 | 2023-05-23 | Samsung Electronics Co., Ltd. | Image sensor |
-
2014
- 2014-08-25 CN CN201420482170.3U patent/CN204031312U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104135633A (en) * | 2014-08-25 | 2014-11-05 | 北京思比科微电子技术股份有限公司 | Image sensor pixel with changeable conversion gain and working method thereof |
| CN110072069A (en) * | 2018-01-23 | 2019-07-30 | 三星电子株式会社 | Imaging sensor |
| US11658193B2 (en) | 2018-01-23 | 2023-05-23 | Samsung Electronics Co., Ltd. | Image sensor |
| CN110072069B (en) * | 2018-01-23 | 2023-06-20 | 三星电子株式会社 | Image sensor |
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| C14 | Grant of patent or utility model | ||
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| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20141217 Termination date: 20180825 |