# US 2025/0097602 A1 · PhotoVoltaic Image Sensor

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- Number: US 2025/0097602 A1
- Document ID: US20250097602A1
- Status: Published application
- Kind: A1
- Application number: 18/463,560
- Filed: 2023-09-20
- Published: 2025-03-20
- Earliest claimed: 2023-09-20
- Assignees: OmniVision Technologies, Inc.
- Applicants: OmniVision Technologies, Inc.
- Inventors: Yoshiyuki Matsunaga; Mabuchi Keiji; Lindsay Grant
- Web page: https://patentgrep.com/patent/US20250097602A1

## CPC

- H04N 25/771: comprising storage means other than floating diffusion
- H04N 25/78: Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters
- H04N 25/53: Control of the integration time
- H04N 25/616: involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
- H04N 25/62: Detection or reduction of noise due to excess charges produced by the exposure, e.g. smear, blooming, ghost image, crosstalk or leakage between pixels
- H04N 25/65: applied to reset noise, e.g. KTC noise related to CMOS structures by techniques other than CDS
- H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An image sensor is an image sensor including a plurality of pixels. Each of the pixels includes a photodiode configured to generate charges based on a light incident amount, a reset transistor configured to reset the photodiode by supplying a reset voltage to the photodiode, a first capacitor configured to hold an output voltage of the photodiode immediately after the reset, and a second capacitor configured to hold the output voltage of the photodiode after a predetermined exposure period. An image signal is obtained from the voltage held by the first capacitor and the voltage held by the second capacitor.

## Claims

### Claim 1

An image sensor including a plurality of pixels, wherein
each of the pixels includes a photodiode configured to generate charges based on a light incident amount, a reset transistor configured to reset the photodiode by supplying a reset voltage to the photodiode, a first capacitor configured to hold an output voltage of the photodiode immediately after the reset, and a second capacitor configured to hold the output voltage of the photodiode after a predetermined exposure period, and
an image signal is obtained from the voltage held by the first capacitor and the voltage held by the second capacitor.

### Claim 2 (depends on 1)

The image sensor according to claim 1, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a first switch transistor connected to another end of the peak hold transistor and configured to control a current to the first capacitor, and a second switch transistor connected to the other end of the peak hold transistor and configured to control a current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first and second switch transistors are turned on to inject the charges to the first and second capacitors, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage corresponding to the output of the photodiode immediately after the reset, and
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 3 (depends on 2)

The image sensor according to claim 2, wherein each of the pixels further includes a first output transistor configured to output a signal corresponding to the voltage of the first capacitor, and a second output transistor configured to output a signal corresponding to the voltage of the second capacitor.

### Claim 4 (depends on 1)

The image sensor according to claim 1, wherein the image signal is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor.

### Claim 5 (depends on 1)

The image sensor according to claim 1, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a first switch transistor connected to another end of the peak hold transistor and configured to control a current to the first capacitor, and a second switch transistor connected to the other end of the peak hold transistor and configured to control a current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first switch transistor is turned on to inject the charges to the first capacitor, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage corresponding to the output of the photodiode immediately after the reset, and
in a state where the first switch transistor is turned off, the second switch transistor is turned on, and the injection voltage is supplied to the one end of the peak hold transistor to inject the charges to the second capacitor, and after supply of the injection voltage is stopped and the predetermined exposure period elapses in the state, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 6 (depends on 5)

The image sensor according to claim 5, wherein each of the pixels further includes a first output transistor configured to output a signal corresponding to the voltage of the first capacitor, and a second output transistor configured to output a signal corresponding to the voltage of the second capacitor.

### Claim 7 (depends on 1)

The image sensor according to claim 1, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a first switch transistor connected to another end of the peak hold transistor and configured to control a current to the first capacitor, and a second switch transistor connected to the other end of the peak hold transistor through the first switch transistor and configured to control a current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first and second switch transistors are turned on to inject the charges to the first and second capacitors, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage corresponding to the output of the photodiode immediately after the reset, and
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 8 (depends on 7)

The image sensor according to claim 7, wherein
each of the pixels further includes an output transistor including a control end connected to an output end of the first capacitor and an output end of the second capacitor and configured to output a signal corresponding to the control end, and a peak hold reset transistor connected to the control end of the output transistor and configured to supply a peak hold reset voltage,
after the exposure period ends and the peak hold reset transistor is turned on for a short period in a state where the first switch transistor and the second switch transistor are turned off, to reset the control end of the output transistor, the first switch transistor is turned on to output a signal corresponding to the voltage held by the first capacitor, from the output transistor, and
after the peak hold reset transistor is turned on for a short period in the state where the first switch transistor and the second switch transistor are turned off, to reset the control end of the output transistor, the second switch transistor is turned on to output a signal corresponding to the voltage held by the second capacitor, from the output transistor.

### Claim 9 (depends on 7)

The image sensor according to claim 7, wherein the image signal is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor.

### Claim 10 (depends on 1)

The image sensor according to claim 1, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a second switch transistor connected to another end of the peak hold transistor and configured to control a current to the second capacitor, and a first switch transistor connected to the other end of the peak hold transistor through the second switch transistor and configured to control the current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first and second switch transistors are turned on to inject the charges to the first and second capacitors, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage corresponding to the output of the photodiode immediately after the reset, and
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 11 (depends on 10)

The image sensor according to claim 10, wherein
each of the pixels further includes an output transistor including a control end connected to an output end of the first capacitor and configured to output a signal corresponding to the control end,
after the exposure period ends, in a state where the first switch transistor and the second switch transistor are turned off, a signal corresponding to the voltage held by the first capacitor is output from the output transistor, and
the first switch transistor is then turned on, and a signal corresponding to a sum of the voltage held by the first capacitor and the voltage held by the second capacitor is output from the output transistor.

### Claim 12 (depends on 10)

The image sensor according to claim 10, wherein the image signal is obtained by subtracting ½ of the voltage held by the first capacitor from the sum of the voltage held by the first capacitor and the voltage held by the second capacitor.

### Claim 13 (depends on 1)

The image sensor according to claim 1, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a second switch transistor including one end connected to another end of the peak hold transistor, a second capacitor connected to another end of the second switch transistor, a first capacitor including one end connected to the other end of the second switch transistor, an output transistor including a control end connected to another end of the first capacitor, and a first switch transistor configured to supply a predetermined voltage to the other end of the first capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first switch transistor is turned on to supply the predetermined voltage to the other end of the first capacitor and to inject the charges to the first capacitor and the second capacitor, and then, after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold a voltage that corresponds to the output of the photodiode immediately after the reset and is reversed in positive and negative, after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period, and
a voltage is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor on the other side of the second capacitor, and is applied to the control end of the output transistor to output the image signal from the output end.

### Claim 14 (depends on 1)

The image sensor according to claim 1, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow there through based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a second switch transistor including one end connected to another end of the peak hold transistor, a first capacitor including one end connected to another end of the second switch transistor, a second capacitor including one end connected to another end of the first capacitor, an output transistor including a control end connected to the other end of the first capacitor, and a first switch transistor configured to supply a predetermined voltage to the other end of the first capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first switch transistor is turned on to supply the predetermined voltage to the other end of the first capacitor and to inject the charges to the first capacitor and the second capacitor, and then, after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage that corresponds to the output of the photodiode immediately after the reset and is reversed in positive and negative,
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period, and
a voltage is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor on the other side of the second capacitor, and is applied to the control end of the output transistor to output the image signal from the output end.

### Claim 15 (depends on 1)

The image sensor according to claim 1, wherein, during a same signal integration period in one frame period, signals are accumulated in the first capacitors of the respective pixels, and are then output horizontal line by horizontal line.

### Claim 16 (depends on 15)

The image sensor according to claim 15, wherein the one frame period is divided into a signal integration period and a readout period after the signal integration period, and the signals accumulated in the first capacitors of the respective pixels during the integration period are sequentially output line by line.

### Claim 17 (depends on 15)

The image sensor according to claim 15, wherein
the pixels are divided into an odd-numbered row group and an even-numbered row group,
in an odd-numbered frame, the signals and the noise are accumulated in the pixels of the odd-numbered row group, and the signals and the noise accumulated in a previous frame are output from the pixels in the even-numbered row group, and
in an even-numbered frame, the signals and the noise are accumulated in the pixels of the even-numbered row group, and the signals and the noise are output from the pixels of the odd-numbered row group.

### Claim 18 (depends on 15)

The image sensor according to claim 15, wherein
in each frame,
in each of the pixels, the signal is accumulated in the first capacitor, and then, the signal accumulated in the first capacitor is transferred to a corresponding first transfer capacitor,
in each of the pixels, the noise is accumulated in the second capacitor, and then, the noise accumulated in the second capacitor is transferred to a corresponding second transfer capacitor, and
the signal and the noise transferred in the previous frame and held are output from the first and second transfer capacitors.

### Claim 19 (depends on 1)

The image sensor according to claim 1, wherein each of the photodiodes operates in a logarithmic region of a forward bias at incidence of high-illuminance light.

### Claim 20 (depends on 19)

The image sensor according to claim 19, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a first switch transistor connected to another end of the peak hold transistor and configured to control a current to the first capacitor, and a second switch transistor connected to the other end of the peak hold transistor and configured to control a current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first and second switch transistors are turned on to inject the charges to the first and second capacitors, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage corresponding to the output of the photodiode immediately after the reset, and
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 21 (depends on 20)

The image sensor according to claim 20, wherein each of the pixels further includes a first output transistor configured to output a signal corresponding to the voltage of the first capacitor, and a second output transistor configured to output a signal corresponding to the voltage of the second capacitor.

### Claim 22 (depends on 19)

The image sensor according to claim 19, wherein the image signal is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor.

### Claim 23 (depends on 19)

The image sensor according to claim 19, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a first switch transistor connected to another end of the peak hold transistor and configured to control a current to the first capacitor, and a second switch transistor connected to the other end of the peak hold transistor and configured to control a current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first switch transistor is turned on to inject the charges to the first capacitor, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage corresponding to the output of the photodiode immediately after the reset, and
in a state where the first switch transistor is turned off, the second switch transistor is turned on, and the injection voltage is supplied to the one end of the peak hold transistor to inject the charges to the second capacitor, and after supply of the injection voltage is stopped and the predetermined exposure period elapses in the state, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 24 (depends on 23)

The image sensor according to claim 23, wherein each of the pixels further includes a first output transistor configured to output a signal corresponding to the voltage of the first capacitor, and a second output transistor configured to output a signal corresponding to the voltage of the second capacitor.

### Claim 25 (depends on 19)

The image sensor according to claim 19, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a first switch transistor connected to another end of the peak hold transistor and configured to control a current to the first capacitor, and a second switch transistor connected to the other end of the peak hold transistor through the first switch transistor and configured to control a current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first and second switch transistors are turned on to inject the charges to the first and second capacitors, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage corresponding to the output of the photodiode immediately after the reset, and
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 26 (depends on 25)

The image sensor according to claim 25, wherein
each of the pixels further includes an output transistor including a control end connected to an output end of the first capacitor and an output end of the second capacitor and configured to output a signal corresponding to the control end, and a peak hold reset transistor connected to the control end of the output transistor and configured to supply a peak hold reset voltage,
after the exposure period ends and the peak hold reset transistor is turned on for a short period in a state where the first switch transistor and the second switch transistor are turned off, to reset the control end of the output transistor, the first switch transistor is turned on to output a signal corresponding to the voltage held by the first capacitor, from the output transistor, and
after the peak hold reset transistor is turned on for a short period in the state where the first switch transistor and the second switch transistor are turned off, to reset the control end of the output transistor, the second switch transistor is turned on to output a signal corresponding to the voltage held by the second capacitor, from the output transistor.

### Claim 27 (depends on 25)

The image sensor according to claim 25, wherein the image signal is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor.

### Claim 28 (depends on 19)

The image sensor according to claim 19, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a second switch transistor connected to another end of the peak hold transistor and configured to control a current to the second capacitor, and a first switch transistor connected to the other end of the peak hold transistor through the second switch transistor and configured to control the current to the second capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first and second switch transistors are turned on to inject the charges to the first and second capacitors, and after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold a voltage corresponding to the output of the photodiode immediately after the reset, and
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period.

### Claim 29 (depends on 28)

The image sensor according to claim 28, wherein
each of the pixels further includes an output transistor including a control end connected to an output end of the first capacitor and configured to output a signal corresponding to the control end,
after the exposure period ends, in a state where the first switch transistor and the second switch transistor are turned off, a signal corresponding to the voltage held by the first capacitor is output from the output transistor, and
the first switch transistor is then turned on, and a signal corresponding to a sum of the voltage held by the first capacitor and the voltage held by the second capacitor is output from the output transistor.

### Claim 30 (depends on 28)

The image sensor according to claim 28, wherein the image signal is obtained by subtracting ½ of the voltage held by the first capacitor from the sum of the voltage held by the first capacitor and the voltage held by the second capacitor.

### Claim 31 (depends on 19)

The image sensor according to claim 19, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow therethrough based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a second switch transistor including one end connected to another end of the peak hold transistor, a second capacitor connected to another end of the second switch transistor, a first capacitor including one end connected to the other end of the second switch transistor, an output transistor including a control end connected to another end of the first capacitor, and a first switch transistor configured to supply a predetermined voltage to the other end of the first capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first switch transistor is turned on to supply the predetermined voltage to the other end of the first capacitor and to inject the charges to the first capacitor and the second capacitor, and then, after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage that corresponds to the output of the photodiode immediately after the reset and is reversed in positive and negative,
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period, and
a voltage is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor on the other side of the second capacitor, and is applied to the control end of the output transistor to output the image signal from the output end.

### Claim 32 (depends on 19)

The image sensor according to claim 19, wherein
each of the pixels further includes a peak hold transistor configured to allow a current to flow there through based on the output voltage of the photodiode, an injection power supply connected to one end of the peak hold transistor and configured to supply an injection voltage, a second switch transistor including one end connected to another end of the peak hold transistor, a first capacitor including one end connected to another end of the second switch transistor, a second capacitor including one end connected to another end of the first capacitor, an output transistor including a control end connected to the other end of the first capacitor, and a first switch transistor configured to supply a predetermined voltage to the other end of the first capacitor,
at the reset of the photodiode, the injection voltage is supplied to the one end of the peak hold transistor, and the first switch transistor is turned on to supply the predetermined voltage to the other end of the first capacitor and to inject the charges to the first capacitor and the second capacitor, and then, after supply of the reset voltage and the injection voltage is stopped, the first switch transistor is turned off to cause the first capacitor to hold the voltage that corresponds to the output of the photodiode immediately after the reset and is reversed in positive and negative,
after the predetermined exposure period elapses in a state where the second switch transistor is turned on, the second switch transistor is turned off to cause the second capacitor to hold the voltage corresponding to the light incident amount in the exposure period, and
a voltage is obtained by subtracting the voltage held by the first capacitor from the voltage held by the second capacitor on the other side of the second capacitor, and is applied to the control end of the output transistor to output the image signal from the output end.

### Claim 33 (depends on 19)

The image sensor according to claim 19, wherein, during a same signal integration period in one frame period, signals are accumulated in the first capacitors of the respective pixels, and are then output horizontal line by horizontal line.

### Claim 34 (depends on 33)

The image sensor according to claim 33, wherein the one frame period is divided into a signal integration period and a readout period after the signal integration period, and the signals accumulated in the first capacitors of the respective pixels during the integration period are sequentially output line by line.

### Claim 35 (depends on 33)

The image sensor according to claim 33, wherein
the pixels are divided into an odd-numbered row group and an even-numbered row group,
in an odd-numbered frame, the signals and the noise are accumulated in the pixels of the odd-numbered row group, and the signals and the noise accumulated in a previous frame are output from the pixels of the even-numbered row group, and
in an even-numbered frame, the signals and the noise are accumulated in the pixels of the even-numbered row group, and the signals and the noise are output from the pixels of the odd-numbered row group.

### Claim 36 (depends on 33)

The image sensor according to claim 33, wherein
in each frame,
in each of the pixels, the signal is accumulated in the first capacitor, and then, the signal accumulated in the first capacitor is transferred to a corresponding first transfer capacitor,
in each of the pixels, the noise is accumulated in the second capacitor, and then, the noise accumulated in the second capacitor is transferred to a corresponding second transfer capacitor, and
the signal and the noise transferred in the previous frame and held are output from the first and second transfer capacitors.