Image sensor and imaging apparatus

There is provided an imaging device that includes a pixel, the pixel comprising: a photodetector; a control transistor; a capacitor coupled to the photodetector; a reset transistor coupled between the control transistor and the capacitor; an amplifier transistor having a gate terminal coupled to the capacitor; and a select transistor coupled to the amplifier transistor; a first signal line coupled to the select transistor; and a first amplifying circuit including a first input terminal coupled to the first signal line and a second input terminal configured to receive a first reference signal and an output terminal coupled to the control transistor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 371 as a U.S. National Stage Entry of International Application No. PCT/JP2017/036666, filed in the Japanese Patent Office as a Receiving Office on Oct. 10, 2017, which claims priority to Japanese Patent Application Number JP2016-201652, filed in the Japanese Patent Office on Oct. 13, 2016, each of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present technology relates to an image sensor and an imaging apparatus. Specifically, the present technology relates to an image sensor and an imaging apparatus that reduce noise unique to the image sensor.

BACKGROUND ART

Conventionally, an image sensor employing a CMOS (Complementary Metal Oxide Semiconductor) structure is used as an image sensor. This image sensor includes pixels arranged in a two-dimensional array. When picking up an image, this image sensor causes a charge holding unit in the pixel to hold a charge generated by a photoelectric conversion element disposed in the pixel. Typically, as the charge holding unit, a floating diffusion formed in a diffusion layer of a semiconductor chip is used. This floating diffusion is connected to a charge conversion amplifier via a charge detection node. This charge conversion amplifier outputs, as an image signal in the pixel, a signal corresponding to the charge held in the floating diffusion.

It is necessary to perform resetting before this charge holding in the floating diffusion. Note that resetting is processing of discharging the charge held in the floating diffusion, and making an image signal output from the pixel equal to predetermined reference voltage, for example, voltage corresponding to a black level. The resetting can be performed by disposing a reset transistor and applying reset voltage to the floating diffusion. However, there is a problem that noise occurs when the reset transistor operates, and a part of this noise remains in the floating diffusion, causing an error in the image signal.

In this regard, a system in which an amplifier for amplifying a difference between the above-mentioned reference voltage and the image signal is disposed and the output of this amplifier is fed back to the floating diffusion via a coupling capacitor to perform resetting has been proposed (see, for example, Patent Literature 1).

CITATION LIST

Patent Literature

SUMMARY

Some embodiments relate to an imaging device that includes a pixel, the pixel comprising: a photodetector; a control transistor; a capacitor coupled to the photodetector; a reset transistor coupled between the control transistor and the capacitor; an amplifier transistor having a gate terminal coupled to the capacitor; and a select transistor coupled to the amplifier transistor; a first signal line coupled to the select transistor; and a first amplifying circuit including a first input terminal coupled to the first signal line and a second input terminal configured to receive a first reference signal and an output terminal coupled to the control transistor.

Some embodiments relate to an electronic apparatus comprising an imaging device that includes a pixel, the pixel comprising: a photodetector; a control transistor; a capacitor coupled to the photodetector; a reset transistor coupled between the control transistor and the capacitor; an amplifier transistor having a gate terminal coupled to the capacitor; and a select transistor coupled to the amplifier transistor; a first signal line coupled to the select transistor; and a first amplifying circuit including a first input terminal coupled to the first signal line and a second input terminal configured to receive a first reference signal and an output terminal coupled to the control transistor.

Technical Problem

In the related art described above, there is a problem that since the output of the amplifier is connected via the coupling capacitor, relatively high voltage is applied to the coupling capacitor after the resetting, dark current increases, and the image quality is deteriorated.

In view of the above, it is desirable to suppress the increase in dark current to prevent the image quality from being deteriorated.

Solution to Problem

According to a first aspect of the present technology, there is provided an image sensor, including: a charge holding unit that holds a charge corresponding to irradiation light, the charge holding unit being connected to a charge detection node for detecting voltage corresponding to the held charge as an image signal; an amplification unit that outputs, as reset voltage of the charge holding unit, voltage corresponding to a difference between a standard signal serving as a reference of the image signal and the detected image signal; a reset unit that resets the charge holding unit by making the charge detection node and an output of the amplification unit conductive; a coupling capacitor that transmits the output reset voltage to the charge holding unit, the coupling capacitor being disposed between the charge detection node and the output of the amplification unit; and a standard signal supply unit that supplies the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are conductive, and supplies a standard signal different from the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are non-conductive. With this, an effect that voltage different from the reset voltage is output from the amplification unit in the case where the charge detection node and the output of the amplification unit are non-conductive is achieved.

Further, in this first aspect, the standard signal supply unit may supply a standard signal having voltage lower than that of the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are non-conductive. With this, an effect that voltage lower than the reset voltage is output from the amplifying unit in the case where the charge detection node and the output of the amplification unit are non-conductive is achieved.

Further, in this first aspect, the image sensor may further include: a reset voltage control unit that controls transfer of the output reset voltage to the coupling capacitor, the reset voltage control unit being disposed between the output of the amplification unit and the coupling capacitor; and a reset voltage holding unit that holds the controlled reset voltage, the reset voltage holding unit being connected to the output of reset voltage control unit. With this, an effect that the transfer of the reset voltage to the coupling capacitor is controlled is achieved.

Further, in this first aspect, the amplification unit may further amplify the voltage corresponding to the difference, and change a bandwidth in the amplification unit depending on whether or not the charge detection node and the output of the amplification unit are conductive. With this, an effect that the bandwidth at the time of amplification is changed by the amplification unit depending on whether or not the charge detection node and the output of the amplification unit are conductive.

Further, in this first aspect, the image sensor may further include an image signal output unit that outputs the detected image signal, the image signal output unit being connected to the charge detection node. With this, an effect that an image signal is output by the image signal output unit is achieved.

Further, in this first aspect, the image sensor may further include: a reference signal generation unit that generates a reference signal serving as a reference for performing analog/digital conversion of the output image signal; and a holding unit that holds a digital signal corresponding to the reference signal on the basis of a result of comparing the output image signal and the generated reference signal, and outputs the held digital signal as a result of analog/digital conversion of the image signal, in which the amplification unit may further output voltage corresponding to a difference between the output image signal and the generated reference signal to the holding unit as a result of the comparison. With this, an effect that the voltage corresponding to the difference between the image signal and the standard signal and the voltage corresponding to the difference between the image signal and the reference signal are output by the amplification unit is achieved.

Further, in this first aspect, the amplification unit may amplify voltage corresponding to a difference between the output image signal and the supplied standard signal, and amplify, with a gain that is different from that in the amplification, voltage corresponding to a difference between the output image signal and the generated reference signal. With this, an effect that when amplifying the voltage corresponding to the difference between the image signal and the reference signal, the amplification is performed with a gain different from that when amplifying the voltage corresponding to the difference between the image signal and the standard signal is achieved.

According to a second aspect of the present technology, there is provided an imaging apparatus, including: a charge holding unit that holds a charge corresponding to irradiation light, the charge holding unit being connected to a charge detection node for detecting voltage corresponding to the held charge as an image signal; an amplification unit that outputs, as reset voltage of the charge holding unit, voltage corresponding to a difference between a standard signal serving as a reference of the image signal and the detected image signal; a reset unit that resets the charge holding unit by making the charge detection node and an output of the amplification unit conductive; a coupling capacitor that transmits the output reset voltage to the charge holding unit, the coupling capacitor being disposed between the charge detection node and the output of the amplification unit; a standard signal supply unit that supplies the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are conductive, and supplies a standard signal different from the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are non-conductive; and a processing circuit that processes the detected image signal. With this, an effect that voltage different from the reset voltage is output from the amplification unit in the case where the charge detection node and the output of the amplification unit are non-conductive.

Advantageous Effects of Invention

In accordance with the present technology, it is possible to achieve an excellent effect of suppressing the increase in dark current to prevent the image quality from being deteriorated. It should be noted that the effect described here is not necessarily limitative and may be any effect described in the present disclosure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for implementing the present technology (hereinafter, referred to as embodiment) will be described. Note that descriptions will be made in the following order. 1. First Embodiment (example in case of performing imaging by rolling shutter system)

2. Second Embodiment (example in case of changing gain of amplification unit)

3. Third Embodiment (example in case where reference voltage is changed depending on dynamic range)

4. Fourth Embodiment (example in case where amplification unit and comparing unit of analog/digital conversion unit are used in combination)

5. Fifth Embodiment (example in case of changing waveform of control signal)

6. Sixth Embodiment (example in case of imaging by global shutter system)

7. Seventh Embodiment (example in case of including two semiconductor chips)

1. First Embodiment

FIG. 1is a diagram showing a configuration example of an imaging apparatus1according to a first embodiment of the present technology. This imaging apparatus1includes a pixel array unit10, a vertical drive unit20, a column signal processing unit30, a standard signal supply unit40, and a reference signal generation unit50.

The pixel array unit10generates an image signal corresponding to incident light. This pixel array unit10is configured by arranging pixels100having photoelectric conversion units in a two-dimensional matrix. Further, in the pixel array unit10, signal lines11for transmitting a control signal to the pixel100, signal lines13for supplying reset voltage to the pixel100, signal lines12for transmitting an image signal generated by the pixel100are wired in an X-Y matrix. Note that the reset voltage is voltage input to the pixel100when resetting the pixel100. The signal line11is wired for each row of the plurality of pixels100. Further, the signal line11is wired in common to the pixels100arranged in one row. That is, control signals different for each row are input to the pixels100, and a common control signal is input to the pixels100arranged in one row. Meanwhile, the signal lines12and13are wired for each column of the plurality of pixels100. Further, the signal lines12and13are wired in common to the pixels100arranged in one column. That is, the image signal of the pixels100arranged in one column is transmitted via the common signal line12, and the reset voltage is supplied to the pixels100arranged in one column via the common signal line13. Details of the configuration of the pixel100will be described later.

The vertical drive unit20generates a control signal. This vertical drive unit20outputs a control signal to the pixel array unit10via the signal line11.

The column signal processing unit30processes the image signal output from the pixel array unit10. This image signal processed by the column signal processing unit30corresponds to the output signal of the imaging apparatus1, and is output to the outside of the imaging apparatus1. Further, this column signal processing unit generates reset voltage and outputs the reset voltage to the pixel array unit10.

The standard signal supply unit40generates a standard signal. Note that the standard signal is a signal serving as a reference of the image signal generated by the pixel100, and is, for example, a signal of voltage corresponding to a black level image signal. The generated standard signal is supplied to the column signal processing unit30via a signal line41. Further, the standard signal supply unit40is capable of generating a plurality of different standard signals. For example, the standard signal supply unit40is capable of generating and supplying a first standard signal and a second standard signal having voltage of an absolute value lower than that of the first standard signal. Then, the standard signal supply unit40is capable of generating the first standard signal in the case where the pixel100is reset, and the second standard signal in other cases. Details of the configuration of the standard signal supply unit40will be described later.

The reference signal generation unit50generates a reference signal. Note that the reference signal is a signal serving as a reference when performing analog/digital conversion on the image signal generated by the pixel100. As this reference signal, for example, a signal whose voltage drops in a ramp shape can be employed. The reference signal generation unit50generates a reference signal in synchronization with the start of analog/digital conversion in an analog/digital conversion unit330to be described later. The reference signal generation unit50outputs the generated reference signal to the column signal processing unit30via a signal line51.

FIG. 2is a diagram showing a configuration example of the pixel100according to the first embodiment of the present technology. This pixel100includes a photoelectric conversion unit105, a charge holding unit106, an image signal detection unit107, an image signal selection unit108, a coupling capacitor104, a reset voltage holding unit103, a reset unit102, and a reset voltage control unit101.

A MOS transistor can be used for the image signal detection unit107, the image signal selection unit108, the reset unit102, and the reset voltage control unit101. Further, the above-mentioned signal lines11to13are wired to the pixel100. Among them, the signal line11includes a feedback signal line FB (feedback), a reset signal line RST (Reset), and a selection signal line SEL (Select). These signal lines are connected to the gates of the MOS transistors, and the control signals described with reference toFIG. 1are transmitted through the signal lines. In the case where voltage equal to or higher than threshold voltage between the gate and the source of the MOS transistor (hereinafter, referred to as on-signal) is input to these signal lines, the corresponding MOS transistor is made conductive. The feedback signal line FB is a signal line for transmitting a signal for controlling supply of the reset voltage. The reset signal line RST is a signal line for transmitting a signal for controlling reset of the charge holding unit106. The selection signal line SEL is a signal line for transmitting a signal for selecting the pixel100. In addition to these, a power source line Vdd is wired to the pixel100. This power source line Vdd supplies positive polarity power.

The anode of the photoelectric conversion unit105is grounded. The cathode of the photoelectric conversion unit105is connected to the gate of the image signal detection unit107, the source of the reset unit102, one end of the charge holding unit106, and one end of the coupling capacitor104. The other end of the charge holding unit106is grounded. The other end of the coupling capacitor104is connected to the drain of the reset unit102, the source of the reset voltage control unit101, and one end of the reset voltage holding unit103. The other end of the reset voltage holding unit103is grounded. The gate of the reset unit102is connected to the reset signal line RST. The drain of the reset voltage control unit101is connected to the signal line13, and the gate thereof is connected to the feedback signal line FB. The drain of the image signal detection unit107is connected to the power source line Vdd, and the source thereof is connected to the drain of the image signal selection unit108. The gate of the image signal selection unit108is connected to the selection signal line SEL, and the source thereof is connected to the signal line12.

The photoelectric conversion unit105generates and holds charges corresponding to irradiation light. For this photoelectric conversion unit105, a photodiode can be used.

The charge holding unit106holds the charges generated by the photoelectric conversion unit105. A floating diffusion formed in the diffusion layer of the semiconductor chip can be used for this charge holding unit106. In the pixel100shown inFIG. 1, the charges generated by the photoelectric conversion unit105are held in the photoelectric conversion unit105and the charge holding unit106.

The image signal detection unit107detects a signal corresponding to the charges held in the charge holding unit106as a pixel signal.

The image signal selection unit108outputs the image signal detected by the image signal detection unit107. The image signal selection unit108outputs the image signal by making the image signal detection unit107and the signal line12conductive.

The reset voltage control unit101causes the reset voltage holding unit103to hold the reset voltage output from the column signal processing unit30. This reset voltage control unit101causes the reset voltage holding unit103to hold the reset voltage by making the signal line13and the reset voltage holding unit103conductive.

The reset voltage holding unit103holds the reset voltage output from the reset voltage control unit101. For example, a capacitor can be used for this reset voltage holding unit103.

The reset unit102resets the charge holding unit106. This reset unit102applies the reset voltage to the charge holding unit106by making the reset voltage holding unit103and the charge holding unit106conductive, thereby to perform resetting.

The coupling capacitor104transmits the reset voltage held in the reset voltage holding unit103to the charge holding unit106.

Note that the image signal detection unit107and the image signal selection unit108constitute an image signal output unit.

“Configuration of Column Signal Processing Unit”

FIG. 3is a diagram showing a configuration example of the column signal processing unit30according to the first embodiment of the present technology. This column signal processing unit30includes a constant current power supply310, an amplification unit320, the analog/digital conversion unit330, and an image signal transfer unit340. Note that the constant current power supply310, the amplification unit320, and the analog/digital conversion unit330are arranged for each column of the pixels100in the pixel array unit10.

The constant current power supply310operates as a load of the image signal detection unit107described with reference toFIG. 2. The constant current power supply310is connected between the signal line12and the ground, and constitutes a source follower circuit together with the image signal detection unit107.

The amplification unit320outputs the voltage corresponding to the difference between the image signal output from the pixel100and the standard signal output from the standard signal supply unit40as the reset voltage described above. This amplification unit320includes an inverting input terminal and a non-inverting input terminal. The signal line12and the signal line41are respectively connected to the inverting input terminal and the non-inverting input terminal. That is, the image signal and the standard signal are respectively input to the inverting input terminal and the non-inverting input terminal. Further, the amplification unit320outputs the reset voltage via the signal line13. Note that the signal line41is wired in common to the non-inverting input terminals of all the amplification units320arranged in the column signal processing unit30. As will be described later, the amplification unit320is capable of amplifying the voltage corresponding to the difference between the image signal and the standard signal with a predetermined gain, and outputting it as the reset voltage.

The analog/digital (AD) conversion unit330performs analog/digital conversion. This analog/digital conversion unit330converts an analog image signal into a digital image signal. The signal line12and the signal line51are wired to the analog/digital conversion unit330, and the image signal generated by the pixel100and the reference signal generated by the reference signal generation unit50are input to the analog/digital conversion unit330. The image signal generated by the pixel100is an analog signal, and is converted into a digital image signal by the analog/digital conversion unit330. This analog/digital conversion is performed with the reference signal as a reference. The converted digital image signal is output to the image signal transfer unit340via the signal line32. Note that the signal line51is wired in common to all the analog/digital conversion units330arranged in the column signal processing unit30. Details of the configuration of the analog/digital conversion unit330will be described later.

The image signal transfer unit340transfers the digital image signal output by the analog/digital conversion unit330. This image signal transfer unit340sequentially outputs the digital image signals output by the analog/digital conversion unit330to perform transfer. For example, this transfer can be performed in order from the digital image signal output by the analog/digital conversion unit330arranged at the left end inFIG. 2. The digital image signal after the transfer is output via the signal line31. Note that the image signal transfer unit340is an example of a processing circuit described in the scope of claims.

FIG. 4is a diagram showing a configuration example of the analog/digital conversion unit330according to the first embodiment of the present technology. This analog/digital conversion unit330includes a comparing unit331, a counting unit332, and a holding unit333.

The comparing unit331compares the analog image signal with the reference signal, and outputs the comparison result to the counting unit332. For example, the comparing unit331is capable of outputting a value “1” in the case where the voltage of the reference signal is higher than the voltage of the analog image signal, and a value “0” in the case where the voltage of the reference signal is lower than the voltage of the analog image signal.

The counting unit332measures the time from the start of analog/digital conversion in the analog/digital conversion unit330. This measurement can be performed by counting clock signals (not shown). This counting is started together with the start of analog/digital conversion, and is stopped on the basis of the comparison result from the comparing unit331. Specifically, in the case where the output of the comparing unit331transits from the value “1” to “0”, the counting unit332is capable of stopping counting. In this case, the counting unit332stops the counting when the analog image signal and the reference signal are substantially equal. As described above, since the reference signal is generated in synchronization with the start of analog/digital conversion, the count value of the counting unit332is a digital value corresponding to the voltage of the reference signal. The counting unit332outputs the count value when the counting is stopped to the holding unit333.

The holding unit333holds the count value output from the counting unit332as a digital image signal generated as a result of analog/digital conversion. This holding unit333outputs the held digital image signal to the image signal transfer unit340.

“Configuration of Standard Signal Supply Unit”

FIG. 5is a diagram showing a configuration example of the standard signal supply unit40according to the first embodiment of the present technology. This standard signal supply unit40includes voltage sources42and43and a selection unit44.

The voltage sources42and43respectively generate the first standard signal and the second standard signal. As described above, the second standard signal is a signal having voltage of an absolute value lower than that of the first standard signal.

The selection unit44selects either the first standard signal generated by the voltage source42or the second standard signal generated by the voltage source43, and outputs the selected signal to the signal line41. This selection unit44selects the first standard signal in the case where the output of the reset voltage control unit101and the charge holding unit106are made conductive by the reset unit102described with reference toFIG. 2. In other cases, the second standard signal is selected.

FIG. 6is a diagram showing an example of a pixel circuit according to the first embodiment of the present technology.FIG. 6describes a reset operation in a circuit including the pixel100, the amplification unit320, and the standard signal supply unit40.

InFIG. 6, a node to which a terminal that is not grounded among two terminals of the charge holding unit106is connected is referred to as charge detection node109. This charge detection node109corresponds to a node for detecting voltage corresponding to the charge held in the charge holding unit106. The gate of the image signal detection unit107is connected to the charge detection node109, and detects voltage corresponding to the charge held in the charge holding unit106as an image signal. Specifically, when the voltage of the charge detection node109is equal to or higher than a threshold value Vth between the gate and the source of the image signal detection unit107, the image signal detection unit107is turned on, and voltage obtained by subtracting the threshold value Vth from the voltage of the charge detection node is output to the source terminal as an image signal. This image signal is output via the signal line12by the image signal selection unit108. InFIG. 6, the threshold value Vth is represented by a potential difference191. Even at the time of resetting, a difference corresponding to the threshold value Vth is generated between the voltage of the charge detection node109and the image signal. Since this threshold value Vth changes under the influence of the ambient temperature or the like, the image signal at the time of resetting includes an error.

In this regard, by placing the amplification unit320and feeding back the difference between the image signal output from the pixel100and the standard signal supplied from the standard signal supply unit40to the charge detection node109, an error due to the threshold value Vth can be reduced. InFIG. 6, a feedback path is formed by making the reset voltage control unit101and the reset unit102conductive, and the voltage corresponding to the difference between the image signal and the standard signal is fed back to the charge detection node109as the reset voltage. At this time, the amplification unit320amplifies the voltage corresponding to the difference between the image signal and the standard signal with a predetermined gain, and outputs it as the reset voltage, thereby making it possible to increase the gain (loop gain) circulating the feedback path. As a result, it is possible to improve the effect of reducing the error due to the threshold value Vth.

Further, at the time of resetting, noise called kTC noise remains in the charge holding unit106. This noise is noise caused by the operation of the reset unit102and occurs when the state of the reset unit102shifts from the conduction state to the non-conduction state. Then, a part thereof remains in the charge holding unit106. InFIG. 6, this noise is represented by the signal source192. Noise remaining in the charge holding unit106can be expressed by the following formula.
Qn{circumflex over ( )}2=kTC

Note that Qn represents a noise charge. k represents the Boltzmann constant. T represents temperature. C represents the electrostatic capacity of the charge holding unit106. As described above, by reducing an electrostatic capacity C of the charge holding unit106, kTC noise charges can be reduced. However, since the electrostatic capacity C depends on the parasitic capacity of the node, it is difficult to change it. Further, in the case where the electrostatic capacity C is reduced, the charge holding capacity is reduced, and the dynamic range of the pixel100is reduced.

In this regard, the coupling capacitor104and the reset voltage holding unit103connected in series are connected in parallel with the charge holding unit106. As a result, the charge generated by the photoelectric conversion unit105is held in the capacitor obtained by combining these three capacitors, and the kTC noise can be reduced. For example, the reset voltage holding unit103can have the same electrostatic capacity as that of the charge holding unit106. Further, the coupling capacitor104can have a smaller electrostatic capacity than the charge holding unit106, for example.

In the pixel circuit having such a configuration, the reset operation can be performed as follows. First, the image signal selection unit108is made conductive. Next, the reset voltage control unit101and the reset unit102are made conductive, and the standard signal supply unit40is caused to supply the first standard signal (Vb1). As a result, the reset voltage based on the first standard signal Vb1is applied to the charge holding unit106and, the charge holding unit106is reset. After that, the reset unit102is made non-conductive. Noise (the signal source192) remains in the charge holding unit106, the reset voltage holding unit103, and the coupling capacitor104. However, since the feedback path is maintained via the coupling capacitor104, noise remaining in the charge holding unit106is removed. After that, by making the reset voltage control unit101non-conductive, the feedback path is released, and exposure and generation of an image signal can be performed.

When making the reset voltage control unit101non-conductive, noise caused by the operation of the reset voltage control unit101occurs. InFIG. 6, this noise is represented by a signal source193. Noise (signal source193) also remains in the charge holding unit106, the reset voltage holding unit103, and the coupling capacitor104. However, by reducing the electrostatic capacity of the coupling capacitor104than that of the charge holding unit106, noise divided into the charge holding unit106can be reduced. As described above, in the pixel circuit shown inFIG. 6, the influence of the error caused by Vth and the kTC noise can be reduced.

By reducing the electrostatic capacity of the coupling capacitor104than the electrostatic capacity of the charge holding unit106as described above, noise remaining in the charge holding unit106can be reduced. However, when the electrostatic capacity of the coupling capacitor104is smaller than the electrostatic capacity of the charge holding unit106, it is necessary to increase the output voltage of the amplification unit320. This is because the voltage applied to the coupling capacitor104among the output voltage of the amplification unit320is increased. Therefore, it is necessary to increase the dynamic range of the amplification unit320. In this regard, when the state of the reset unit102shifts from the conduction state to the non-conduction state, the standard signal supply unit40is caused to supply the second standard signal Vb2having voltage of an absolute value lower than that of the above-mentioned first standard signal Vb1, and voltage based on the second standard signal Vb2is fed back to the charge detection node109.

That is, when the reset voltage based on the first standard signal Vb1is output from the amplification unit320, the coupling capacitor104is short-circuited by the reset unit102. When the reset unit102enters the non-conduction state, voltage based on the second standard signal Vb2, which is lower than the first standard signal Vb1, is output from the amplification unit320. As a result, it is possible to prevent the increase in the dynamic range required for the amplification unit320.

Further, in addition to the charge generated by photoelectric conversion, a charge generated due to factors other than photoelectric conversion flows into the charge holding unit106. This charge inflow is called dark current, becomes an error, and is superimposed on the image signal. This dark current is proportional to the voltage applied inside the pixel100. By holding the voltage based on the second standard signal in the reset voltage holding unit103and the coupling capacitor104as described above, the voltage of the reset voltage holding unit103and the like can be lowered, and the influence of the dark current can be reduced.

FIG. 7is a diagram showing an example of the reset operation in the first embodiment of the present technology. InFIG. 7, FB and RST represent control signals input to the pixel100through the feedback signal line FB and the reset signal line RST, respectively. Of these binarized waveforms, the value “1” represents input of the on-signal. Further, the standard signal represents the standard signal supplied from the standard signal supply unit40. In this standard signal, broken lines represent the level of 0 V in the standard signal. Further, the amplification unit output represents the output voltage waveform of the amplification unit320. The reset voltage holding unit and the charge holding unit represent voltage waveforms applied to the reset voltage holding unit103and the charge holding unit106, respectively. Note that inFIG. 7, it is assumed that the image signal selection unit108is conductive.

First, the on-signal is input from the feedback signal line FB and the reset signal line RST, and the reset voltage control unit101and the reset unit102are made conductive. At the same time, the first standard signal Vb1is supplied from the standard signal supply unit40. As a result, the amplification unit320outputs the reset voltage based on the first standard signal Vb1. Since the reset unit102is conductive, voltage (Vb1′) substantially the same as the reset voltage holding unit103is applied to the charge holding unit106. This voltage corresponds to the reset voltage, and has a value substantially equal to the voltage obtained by superimposing the threshold value Vth on the first standard signal Vb1.

Next, the input of the on-signal from the reset signal line RST is stopped, and the second standard signal Vb2is supplied from the standard signal supply unit40. At this time, noise caused by the operation of the reset unit102occurs. InFIG. 7, an example where the voltage of the charge holding unit106is reduced by ΔVb1due to the influence of this noise is shown. However, since the reset voltage control unit101is conductive, Vb2′, which is voltage based on the second standard signal Vb2, is applied to the charge holding unit106via the coupling capacitor104. Voltage lower than this Vb2′ is applied to the reset voltage holding unit103. Next, the input of the on-signal from the feedback signal line FB is stopped, and the reset voltage control unit101is made non-conductive. At this time, due to the influence of noise caused by the operation of the reset voltage control unit101, the voltage of the charge holding unit106is reduced by ΔVb2. Due to the effect of the coupling capacitor104, this ΔVb2becomes lower than ΔVb1.

In this way, the reset operation in the first embodiment of the present technology can be performed. By making the reset unit102non-conductive and supplying the second standard signal Vb2to the amplification unit320, the voltage of the charge holding unit106after resetting changes to Vb2′. In this case, the second standard signal is made to be an image signal corresponding to the black level in the pixel100. That is, at the time of resetting, the resetting is performed by reset voltage higher than the voltage corresponding to the black level in the pixel100.

FIG. 8is a diagram showing an example of image signal generation processing in the first embodiment of the present technology.FIG. 8shows the image signal generation processing of the pixels100arranged in the first row and the second row in the pixel array unit10. InFIG. 8, the standard signal represents the standard signal supplied from the standard signal supply unit40. In this standard signal, broken lines represent the potential of 0 V of the standard signal. The reference signal represents the reference signal generated by the reference signal generation unit50described with reference toFIG. 1. The comparing unit output represents the output of the comparing unit331described with reference toFIG. 4. SEL, FB, and RST represent control signals input through the selection signal line SEL, the feedback signal line FB, and the reset signal line RST, respectively. Since different control signals are input for each row, they are distinguished by adding line numbers. For example, SEL1and SEL2represent control signals input by the selection signal line SEL wired to the pixels100of the first row and the second row, respectively. Further, similarly toFIG. 7, the value “1” represents input of the on-signal. The image signals each represent the waveform of the image signal output from the pixel100. These image signals are also distinguished by adding line numbers.

In the period from T0to T1, the standard signal supply unit40supplies the second standard signal Vb2. The supply of the second standard signal Vb2continues until T5. This period corresponds to the initial state, and the input of the on-signal to all the signal lines is stopped. Further, in this period, the charge generated by the photoelectric conversion unit105is held in the charge holding unit106.

In the period from T1to T5, the on-signal is input from a selection signal line SEL1, the image signal selection units108of the pixels100arranged in the first row are made conductive, and an image signal corresponding to the charge held in the charge holding unit106is output (T1). Note that the input of the on-signal to the selection signal line SEL1continues until T8. Next, the reference signal generation unit50starts generation of the reference signal (T2). Next, when the voltage of the reference signal becomes lower than the voltage of the image signal, the output of the comparing unit331transits from the value “1” to “0” (T3). Next, the reference signal generation unit50stops the generation of the reference signal (T4). After that, the digital image signal is held in the holding unit333described with reference toFIG. 4.

In the period from T5to T6, the on-signal is input from a feedback signal line FB1and a reset signal line RST1, and the reset voltage control unit101and the reset unit102are made conductive. At the same time, the standard signal supply unit40supplies the first standard signal Vb1. As a result, resetting is performed in the pixels100arranged in the first row, and the voltage of the image signal increase. Note that the input of the on-signal to the feedback signal line FB1continues until T7.

In the period from T6to T7, the input of the on-signal to the reset signal line RST1is stopped. At the same time, the standard signal supply unit40supplies the second standard signal Vb2. As a result, the image signal changes to voltage based on the second standard signal Vb2. Note that the supply of the second standard signal Vb2of the standard signal supply unit40continues until T12.

In the period from T7to T8, the input of the on-signal to the feedback signal line FB1is stopped. As a result, new exposure is started in the pixels100arranged in the first row, and the charge generated by the photoelectric conversion unit105is held in the charge holding unit106.

In the period from T8to T15, the input of the on-signal to the selection signal line SEL1is stopped, and the on-signal is input to a selection signal line SEL2(T8). After that, the same processing as the processing in the period from T1to T8is performed in the pixels100arranged in the second row.

By performing the processing on the pixels100arranged in all the rows of the pixel array unit10, a frame, which is an image signal corresponding to one screen, can be generated. As described above, an imaging method in which exposure, resetting, and output of the image signal are sequentially performed for each row is referred to as a rolling shutter system.

As described above, in the first embodiment of the present technology, by outputting voltage lower than the reset voltage to the pixel100from the amplification unit320after resetting the pixel100, voltage applied to the reset voltage holding unit103and the coupling capacitor104is reduced. As a result, it is possible to suppress the increase in dark current to prevent the image quality from being deteriorated.

Modified Example

In the first embodiment described above, the reset voltage is supplied via the reset voltage control unit101and the reset unit102. Meanwhile, a modified example of the first embodiment of the present technology is different from the first embodiment in that the reset voltage is directly supplied to the reset unit102.

FIG. 9is a diagram showing a configuration example of the pixel100according to the modified example of the first embodiment of the present technology. The pixel100inFIG. 9is different from the pixel100described with reference toFIG. 2in that the drain of the reset unit102is connected to the signal line13. Since the reset voltage is supplied to the reset unit102without passing through the reset voltage control unit101, the equivalent resistance of a path transmitting the reset voltage can be reduced, and the time required for resetting can be reduced.

As described above, in accordance with the modified example of the first embodiment of the present technology, since the reset voltage is directly applied to the drain of the reset unit102, the time required for resetting can be reduced.

2. Second Embodiment

In the first embodiment described above, the reset voltage or the like is output to the pixel100by using the single amplification unit320. Meanwhile, resetting or the like may be performed by using a plurality of amplifiers having different bandwidths. The second embodiment of the present technology is different from the first embodiment in that two amplifiers are used.

FIG. 10is a diagram showing an example of a pixel circuit according to the second embodiment of the present technology. The pixel circuit shown inFIG. 10is different from the pixel circuit described with reference toFIG. 6in the following points. The column signal processing unit30shown inFIG. 10further includes an amplification unit350and a selection unit360. The amplification unit350amplifies the difference between the image signal and the standard signal in a bandwidth different from that of the amplification unit320. Further, the selection unit360selects one of the amplification units320and350, and transmits the output of the selected amplification unit to the signal line13. Further, the standard signal supply unit40shown inFIG. 10supplies the first standard signal Vb1to the non-inverting input terminal of the amplification unit320and the second standard signal Vb2to the non-inverting input terminal of the amplification unit350.

The reset operation in the pixel circuit shown inFIG. 10can be performed as follows. First, the reset voltage control unit101and the reset unit102are made conductive. At the same time, the selection unit360transmits the output of the amplification unit320to the signal line13. As a result, the reset voltage based on the first standard signal Vb1is output from the amplification unit320and applied to the charge holding unit106. After that, the reset unit102is made non-conductive. At the same time, the selection unit360transmits the output of the amplification unit350to the signal line13. As a result, voltage based on the second standard signal Vb2is output from the amplification unit350and applied to the charge holding unit106via the coupling capacitor104.

When the reset voltage based on the first standard signal Vb1is applied to the charge holding unit106, the reset unit102is made conductive to short-circuit the coupling capacitor104, so that the gain (loop gain) of the feedback path increases. Therefore, when the reset voltage based on the first standard signal Vb1is applied to the charge holding unit106, by narrowing the bandwidth of the amplification unit, the operation of the amplification unit can be stabilized. Meanwhile, when voltage based on the second standard signal Vb2is applied to the charge holding unit106, the reset unit102enters the non-conduction state, so that the output voltage of the amplification unit is divided by the coupling capacitor104and the charge holding unit106. For this reason, the loop gain is reduced and the settling time increases. In this regard, when voltage based on the second standard signal Vb2is applied to the charge holding unit106, the settling time can be reduced by widening the bandwidth of the amplification unit.

In the second embodiment of the present technology, the two amplification units320and350having different bandwidths are arranged, and one of them is selected and used. Then, the bandwidth of the amplification unit320is narrowed, and the bandwidth of the amplification unit350is widened. As a result, when applying the reset voltage, the stability of the amplification unit can be improved. Further, when applying voltage based on the second standard signal Vb2, the settling time can be reduced.

Since the configuration of the imaging apparatus1other than this is similar to that of the imaging apparatus1described in the first embodiment of the present technology, the description thereof will be omitted.

As described above, in the second embodiment of the present technology, two amplification units having different bandwidths are selected and the reset voltage or the like is applied to the charge holding unit106. As a result, it is possible to improve the stability at the time of resetting, reduce the settling time, and reduce the time required for imaging.

In the second embodiment described above, the selection unit360selects the outputs of the amplification unit320and350. Meanwhile, in a modified example of the second embodiment of the present technology, the outputs of the amplification unit320and350are individually wired to the pixels100. It is different from the second embodiment in that the selection unit360is not required.

FIG. 11is a diagram showing an example of a pixel circuit according to the modified example of the second embodiment of the present technology. As compared with the pixel circuit described with reference toFIG. 10, the pixel circuit shown inFIG. 10does not need to include the selection unit360. Further, the output of the amplification unit320shown inFIG. 10is connected to the drain of the reset unit102via a signal line14, and the output of the amplification unit350is connected to the drain of the reset voltage control unit101via the signal line13.

As described above, in accordance with the modified example of the second embodiment of the present technology, it is possible to supply the outputs of the amplification units320and350to the pixels100without providing the selection unit360, and simplify the configuration of the imaging apparatus1.

In the first embodiment described above, the reset voltage or the like based on the first reference voltage and the second reference voltage is applied to the charge holding unit106. Meanwhile, the reference voltage may be changed depending on the dynamic range required for the pixel100, and the reset voltage or the like may be changed. A third embodiment of the present technology is different from the first embodiment in that the reset voltage is changed depending on the dynamic range.

“Configuration of Standard Signal Supply Unit”

FIG. 12is a diagram showing a configuration example of the standard signal supply unit40according to the third embodiment of the present technology. The standard signal supply unit40shown inFIG. 12is different from the standard signal supply unit40described with reference toFIG. 5in the following points. The standard signal supply unit40shown inFIG. 12includes a selection unit47instead of the selection unit44. Further, the standard signal supply unit40shown inFIG. 12further includes voltage sources45and46.

The voltage sources45and46generate a third reference signal and a fourth reference signal, respectively. The third standard signal and the fourth standard signal are signals corresponding to the first standard signal and the second standard signal, respectively. That is, the fourth standard signal is a signal having voltage of an absolute value lower than that of the third standard signal. Meanwhile, the third standard signal and the fourth standard signal are signals having voltage of absolute values lower than those of the first standard signal and the second standard signal, respectively.

The selection unit47selects one of standard signals generated by the voltage sources42,43,45, and46, and outputs the selected signal to the signal line41. This selection unit47operates as follows. The selection unit47selects the first standard signal and the second standard signal and supplies the selected signals to the amplification unit320in the case where a wide dynamic range is required for the imaging apparatus1. As a result, relatively high reset voltage is applied, and it is possible to suppress saturation of the pixel and achieve a wide dynamic range. Meanwhile, in the case where a wide dynamic range is not required, the selection unit47selects the third standard signal and the fourth standard signal and supplies the selected signals to the amplification unit320. As a result, relatively low reset voltage can be applied, and the dark current can be reduced. Therefore, in the case where imaging is performed in a low illuminance environment, the image quality can be improved.

Since the configuration of the imaging apparatus1other than this is similar to that of the imaging apparatus1described in the first embodiment of the present technology, the description thereof will be omitted.

As described above, in accordance with the third embodiment of the present technology, by selecting the standard signal and supplying the selected signal to the amplification unit320to change the reset voltage, it is possible to achieve the characteristics corresponding to the required dynamic range and improve the user's convenience.

In the first embodiment described above, the comparing unit331compares the image signal and the reference signal in the analog/digital conversion unit330. However, this comparison may be performed by the amplification unit320. A fourth embodiment of the present technology is different from the first embodiment in that the amplification unit320further compares the image signal and the reference signal in the analog/digital conversion.

“Configuration of Column Signal Processing Unit”

FIG. 13is a diagram showing a configuration example of the column signal processing unit30according to the fourth embodiment of the present technology. The column signal processing unit30shown inFIG. 13is different from the column signal processing unit30described with reference toFIG. 3in the following points. The column signal processing unit30inFIG. 13includes an analog/digital conversion unit390instead of the analog/digital conversion unit330. Further, the column signal processing unit30shown inFIG. 13further includes selection units370and380.

The analog/digital conversion unit390includes a counting unit392and a holding unit393. The configurations of these units can be similar to those of the counting unit332and the holding unit333described with reference toFIG. 4. Note that the counting unit392is connected to the selection unit380via a signal line33.

The selection unit370selects either the standard signal output from the standard signal supply unit40or the reference signal output from the reference signal generation unit50, and inputs the selected signal to the non-inverting input terminal of the amplification unit320. This selection unit370selects the standard signal when performing the reset operation in the pixel100and selects the reference signal when performing analog/digital conversion of the image signal.

The selection unit380selects either the signal line13or the signal line33, and outputs the output of the amplification unit320to the selected signal line. This selection unit380selects the signal line13when performing the reset operation in the pixel100and selects the signal line33when performing analog/digital conversion of the image signal.

When performing analog/digital conversion of the image signal, the amplification unit320shown inFIG. 13amplifies the voltage corresponding to the difference between the image signal and the reference signal. The amplification unit320outputs the difference voltage after the amplification to the counting unit392as a result of comparing the image signal and the reference signal. At this time, by setting the gain of the amplification unit320to a higher gain than in the case of performing the reset operation in the pixel100, it is possible to make the output transition steep, and reduce the error of analog/digital conversion.

Since the configuration of the imaging apparatus1other than this is similar to that of the imaging apparatus1described with reference to the first embodiment of the present technology, the description thereof will be omitted.

As described above, in accordance with the fourth embodiment of the present technology, it is possible to perform analog/digital conversion without providing the comparing unit331in the column signal processing unit30, and simplify the configuration of the imaging apparatus1.

In the first embodiment described above, noise caused when the state of the reset voltage control unit101shifts to the non-conduction state is divided by the coupling capacitor104and the charge holding unit106, thereby reducing the influence of the above-mentioned noise. However, the transition of the state of the reset voltage control unit101to the non-conduction state may be made slow to reduce the noise. The fifth embodiment of the present technology is different from the first embodiment in that the transition speed of the state of the reset voltage control unit101to the non-conduction state is changed.

FIG. 14is a diagram showing an example of a control signal in the fifth embodiment of the present technology.FIG. 14shows the waveform of the control signal transmitted through the feedback signal line FB and the reset signal line RST.

As described above, the control signal (on-signal) of the reset voltage control unit101is transmitted through the feedback signal line FB, and the control signal (on-signal) of the reset unit102is transmitted through the reset signal line RST. By increasing the fall time of these on-signals, the transition speed of the states of the reset voltage control unit101and the reset unit102from the conduction state to the non-conduction state is reduced. As a result, so-called switching noise can be reduced, and the noise remaining in the charge holding unit106can be further reduced. Further, by employing such a waveform, it is also possible to reduce the influence of the propagation delay caused by the signal line11arranged in the row of the pixel array unit10.

Since the configuration of the imaging apparatus1other than this is similar to that of the imaging apparatus1described in the first embodiment of the present technology, the description thereof will be omitted.

As described above, in accordance with the fifth embodiment of the present technology, by changing the waveform of the control signal, it is possible to reduce noise generated on the basis of the operation of the reset voltage control unit101or the like.

In the first embodiment described above, imaging using a rolling shutter system is performed. However, imaging using a global shutter system may be performed. A sixth embodiment of the present technology is different from the first embodiment in that a global shutter system is employed.

FIG. 15is a diagram showing a configuration example of the pixel100in the sixth embodiment of the present technology. The pixel100shown inFIG. 15is different from the pixel100described with reference toFIG. 2in the following points. The pixel100inFIG. 15further includes an overflow gate111and a charge transfer section112. Further, an overflow signal line OFG (Overflow) and a transfer signal line TRG (Transfer Gate) are further wired to the pixel100inFIG. 15. The overflow signal line OFG is a signal line for transmitting the on-signal to the overflow gate111. The transfer signal line TRG is a signal line for transmitting the on-signal to the charge transfer unit112.

The gate of the overflow gate111is connected to the overflow signal line OFG, and the drain of the overflow gate111is connected to the power source line Vdd. The cathode of the photoelectric conversion unit105is commonly connected to the source of the overflow gate111and the source of the charge transfer unit112. The gate of the charge transfer unit112is connected to the transfer signal line TRG, and the drain of the charge transfer unit112is connected to the gate of the image signal detection unit107, the source of the reset unit102, one end of the charge holding unit106, and one end of the coupling capacitor104. Note that a MOS transistor can be used for the overflow gate111and the charge transfer unit112. Since the configuration of the pixel100other than this is similar to that of the pixel100described with reference toFIG. 2, the description thereof will be omitted.

The overflow gate111resets the photoelectric conversion unit105. The overflow gate111performs this resetting by making the photoelectric conversion unit105and the power source line Vdd conductive. Further, the overflow gate111further discharges the excessively generated charge in the photoelectric conversion unit105.

The charge transfer unit112transfers the charge generated in the photoelectric conversion unit105to the charge holding unit106. This charge transfer unit112transfers the charge by making the photoelectric conversion unit105and the charge holding unit106conductive.

FIG. 16is a diagram showing an example of image signal generation processing in the sixth embodiment of the present technology.FIG. 16shows the image signal generation processing of the pixels100arranged in the first row to the third row in the pixel array unit10. Since the description inFIG. 16is similar to that inFIG. 8, the description thereof is omitted.

In the period from T0to T2, the standard signal supply unit40supplies the second standard signal Vb2. This supply of the second standard signal Vb2continues until T6. Further, an on-signal is input from overflow signal lines OFG1to OFG3, the overflow gate111of the pixel100arranged in the pixel array unit10is made conductive, and the photoelectric conversion unit105is reset (T0). Next, the input of the on-signal to the overflow signal lines OFG1to OFG3is stopped (T1). As a result, exposure is started. That is, the photoelectric conversion unit105starts holding of the generated charge.

In the period from T2to T3, an on-signal is input from transfer signal lines TRG1to TRG3, and the charge transfer units112of all the pixels100arranged in the pixel array unit10are made conductive. As a result, the charge held in the photoelectric conversion unit105is transferred to the charge holding unit106.

In the period from T3to T6, the input of the on-signal to the transfer signal lines TRG1to TRG3is stopped. At the same time, the-on signal is input from the overflow signal lines OFG1to OFG3to the overflow gates111of all the pixels100. As a result, exposure is stopped. Note that the input of the on-signal to the overflow signal lines OFG1to OFG3continues until T22. Further, the-on signal is input from the selection signal line SEL1, and the image signal selection unit108of the pixel100in the first row is made conductive. Note that the input of the on-signal to the selection signal line SEL1continues until T9. Next, the reference signal generation unit50generates a reference signal (T4to T5), and analog/digital conversion of the image signal is performed.

In the period from T6to T9, an on-signal is input from the feedback signal line FB1and the reset signal line RST1, and the reset voltage control unit101and the reset unit102are made conductive. At the same time, the standard signal supply unit40supplies the first standard signal Vb1. As a result, resetting is performed in the pixel100arranged in the first row. Next, the input of the on-signal to the reset signal line RST1is stopped (T7). At the same time, the standard signal supply unit40starts supply of the second standard signal Vb2. Note that the supply of the second standard signal Vb2by the standard signal supply unit40continues until T12. After that, the input of the on-signal to the feedback signal line FB1is stopped (T8). As a result, the analog/digital conversion and reset processing of the image signal in the pixel100arranged in the first row is completed.

In the period from T9to T15, the input of the on-signal to the selection signal line SEL1is stopped, and the on-signal is input to the selection signal line SEL2(T9). After that, processing similar to that in T3to T9is performed in the pixel100arranged in the second row.

In the period from T15to T21, the input of the on-signal to the selection signal line SEL2is stopped, and the on-signal is input to a selection signal line SEL3(T15). After that, processing similar to that described above is performed in the pixel100arranged in the third row.

In the period from T21to T23, processing similar to that in T3to T9is performed for the pixels100arranged in all rows, an image signal corresponding to one screen is acquired from the pixel array unit10, and resetting of all the pixels100arranged in the pixel array unit10is completed. Further, the input of the on-signal to the overflow signal lines OFG1to OFG3is stopped, and new exposure is started (T22).

In the period from T23to T24, processing similar to that in T2to T3is performed, exposure is stopped, and the charge is transferred from the photoelectric conversion unit105.

Note that the input of the on-signal to the overflow signal line OFG and stopping of the input are each simultaneously performed for the pixels100arranged in all the rows of the pixel array unit10. Similarly, the input of the on-signal to the transfer signal line TRG and stopping of the input are each simultaneously performed for the pixels100arranged in all the rows of the pixel array unit10. As a result, it is possible to simultaneously start or finish exposure in all the pixels100arranged in the pixel array unit10.

As described above, since the exposure is simultaneously started or finished in all the pixels100arranged in the pixel array unit10, an image signal with less distortion than that in a rolling shutter system can be obtained.

Since the configuration of the imaging apparatus1other than this is similar to that of the imaging apparatus1described in the first embodiment of the present technology, the description thereof will be omitted.

As described above, in the sixth embodiment of the present technology, the overflow gate111and the charge transfer unit112are arranged in the pixel100, resetting of the photoelectric conversion unit105and transfer of charges from the photoelectric conversion unit105are performed simultaneously for all pixels. As a result, it is possible to employ a global shutter system and improve the image quality.

In the first embodiment described above, the pixel array unit10and the column signal processing unit30are formed on the same semiconductor chip. However, these units may be formed on different semiconductor chips. A seventh embodiment of the present technology is different from the first embodiment in that the imaging apparatus1includes two semiconductor chips.

FIG. 17is a diagram showing a configuration example of the imaging apparatus1according to the seventh embodiment of the present technology. The imaging apparatus1shown inFIG. 17includes a pixel chip2and a circuit chip3.

The pixel chip2is a semiconductor chip on which the pixel array unit10is formed. The vertical drive unit20(not shown) can be further formed on this pixel chip2.

The circuit chip3is a semiconductor chip on which the column signal processing unit30is formed. The standard signal supply unit40(not shown) and the reference signal generation unit50(not shown) can be further formed in this circuit chip3.

The imaging apparatus1shown inFIG. 17is configured by bonding the pixel chip2and the circuit chip3. InFIG. 17, the signal line12for transmitting an image signal from the pixel100includes pads122and123and wirings121and124. The pads122and123are formed on the bonding faces of the pixel chip2and the circuit chip3, respectively, and transmit signals. When the pixel chip2and the circuit chip3are bonded to each other, the pads122and123are aligned and bonded so that these pads are in contact with each other. As a result, these pads are electrically connected to each other, and signals can be transmitted. The wiring121is formed in the pixel chip2and connects the pixel100and the pad122. Further, the wiring124is formed in the circuit chip3and connects the amplification unit320and the pad123. Similarly to the signal line12, the signal line13includes pads132and133and wirings131and134.

Further, by bonding the pixel chip2and the circuit chip3and connecting the signal lines with the pads122,123, and the like, the amplification unit320can be arranged in the vicinity of, e.g., immediately below, the pixel100. As a result, the wiring distance of the signal line13can be reduced, and the parasitic capacitance of the signal line13can be reduced. Since this parasitic capacitance is to be connected to the output of the amplification unit320, by decreasing this parasitic capacitance, the settling time is reduced and the time required for resetting can be reduced.

Since the configuration of the imaging apparatus1other than this is similar to that of the imaging apparatus1described in the first embodiment of the present technology, the description thereof will be omitted.

As described above, in accordance with the seventh embodiment of the present technology, by configuring the imaging apparatus1by bonding the pixel chip2and the circuit chip3, the time required for resetting can be reduced.

As described above, in accordance with the embodiment of the present technology, by applying voltage lower than the reset voltage to the reset voltage holding unit103and the coupling capacitor104arranged in the pixel100after resetting, it is possible to suppress the dark current to prevent the image quality from being deteriorated.

Note that the above-mentioned embodiments provide examples for embodying the present technology and the matters in the embodiments and the specifying matters in the scope of claims are associated. Similarly, the specifying matters in the scope of claims and the matters in the embodiments of the present technology, which are denoted by the identical names, have correspondence. It should be noted that the present technology is not limited to the embodiments and can be embodied by making various modifications to the embodiments without departing from its essence.

Further, the processing procedures described in the above embodiments may be construed as methods including those series of procedures, a program for causing a computer to execute those series of procedures, or a recording medium storing that program. As this recording medium, a CD (Compact Disc), an MD (Mini Disc), a DVD (Digital Versatile Disc), a memory card, and a Blu-ray (registered trademark) disc can be used, for example.

It should be noted that the effects described herein are merely examples and not limitative. Further, other effects may be provided.

It should be noted that the present technology may take the following configurations.

(1) An image sensor, including:a charge holding unit that holds a charge corresponding to irradiation light, the charge holding unit being connected to a charge detection node for detecting voltage corresponding to the held charge as an image signal;an amplification unit that outputs, as reset voltage of the charge holding unit, voltage corresponding to a difference between a standard signal serving as a reference of the image signal and the detected image signal;a reset unit that resets the charge holding unit by making the charge detection node and an output of the amplification unit conductive;a coupling capacitor that transmits the output reset voltage to the charge holding unit, the coupling capacitor being disposed between the charge detection node and the output of the amplification unit; anda standard signal supply unit thatsupplies the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are conductive, andsupplies a standard signal different from the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are non-conductive.

(2) The image sensor according to (1) above, in whichthe standard signal supply unit supplies a standard signal having voltage lower than that of the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are non-conductive.

(3) The image sensor according to (1) or (2) above, further including:a reset voltage control unit that controls transfer of the output reset voltage to the coupling capacitor, the reset voltage control unit being disposed between the output of the amplification unit and the coupling capacitor; anda reset voltage holding unit that holds the controlled reset voltage, the reset voltage holding unit being connected to the output of reset voltage control unit.

(4) The image sensor according to any one of (1) to (3) above, in whichthe amplification unit further amplifies the voltage corresponding to the difference, and changes a bandwidth in the amplification unit depending on whether or not the charge detection node and the output of the amplification unit are conductive.

(5) The image sensor according to any one of (1) to (4) above, further including an image signal output unit that outputs the detected image signal, the image signal output unit being connected to the charge detection node.

(6) The image sensor according to any one of (1) to (5) above, further including:a reference signal generation unit that generates a reference signal serving as a reference for performing analog/digital conversion of the output image signal; anda holding unit thatholds a digital signal corresponding to the reference signal on the basis of a result of comparing the output image signal and the generated reference signal, andoutputs the held digital signal as a result of analog/digital conversion of the image signal, in whichthe amplification unit further outputs voltage corresponding to a difference between the output image signal and the generated reference signal to the holding unit as a result of the comparison.

(7) The image sensor according to (6) above, in whichthe amplification unit amplifies voltage corresponding to a difference between the output image signal and the supplied standard signal, and amplifies, with a gain that is different from that in the amplification, voltage corresponding to a difference between the output image signal and the generated reference signal.

(8) An imaging apparatus, including:a charge holding unit that holds a charge corresponding to irradiation light, the charge holding unit being connected to a charge detection node for detecting voltage corresponding to the held charge as an image signal;an amplification unit that outputs, as reset voltage of the charge holding unit, voltage corresponding to a difference between a standard signal serving as a reference of the image signal and the detected image signal;a reset unit that resets the charge holding unit by making the charge detection node and an output of the amplification unit conductive;a coupling capacitor that transmits the output reset voltage to the charge holding unit, the coupling capacitor being disposed between the charge detection node and the output of the amplification unit;a standard signal supply unit thatsupplies the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are conductive, andsupplies a standard signal different from the standard signal to the amplification unit where the charge detection node and the output of the amplification unit are non-conductive; anda processing circuit that processes the detected image signal.

(9) An imaging device that includes a pixel, the pixel comprising:a photodetector;a control transistor;a capacitor coupled to the photodetector;a reset transistor coupled between the control transistor and the capacitor;an amplifier transistor having a gate terminal coupled to the capacitor; anda select transistor coupled to the amplifier transistor;a first signal line coupled to the select transistor; anda first amplifying circuit including a first input terminal coupled to the first signal line and a second input terminal configured to receive a first reference signal and an output terminal coupled to the control transistor.

(10) The imaging device according to (9), further comprising a switch circuit coupled to the second input terminal of the first amplifying circuit, wherein the switch circuit is configured to couple the second input terminal of the first amplifying circuit to the first reference signal or a second reference signal.

(11) The imaging device according to (10), further comprising a reference signal generation circuit coupled to the switch circuit.

(12) The imaging device according to (11), wherein the reference signal generation circuit is configured to provide the first reference signal and the second reference signal.

(13) The imaging device according to any one of (9) through (12), further comprising a second amplifying circuit, wherein a first input terminal of the second amplifying circuit is coupled to the select transistor.

(14) The imaging device according to (13), wherein a second input terminal of the second amplifying circuit is configured to receive a second reference signal different from the first reference signal.

(15) The imaging device according to (13) or (14), further comprising a switch circuit configured to selectively couple an output of the first amplifying circuit or an output of the second amplifying circuit to the control transistor.

(16) The imaging device according to (14) or (15), further comprising a reference signal generation circuit configured to provide the first reference signal and the second reference signal.

(17) The imaging device according to any one of (14) through (16), wherein a first output of the reference signal generation circuit is coupled to the second input terminal of the first amplifying circuit and a second output of the reference signal generation circuit is coupled to the second input terminal of the second amplifying circuit.

(18) The imaging device according to any one of (13) through (17), wherein the first input terminal of the second amplifying circuit is coupled to the select transistor via a second signal line.

(19) An electronic apparatus comprising an imaging device that includes a pixel, the pixel comprising:a photodetector;a control transistor;a capacitor coupled to the photodetector;a reset transistor coupled between the control transistor and the capacitor;an amplifier transistor having a gate terminal coupled to the capacitor; anda select transistor coupled to the amplifier transistor;a first signal line coupled to the select transistor; anda first amplifying circuit including a first input terminal coupled to the first signal line and a second input terminal configured to receive a first reference signal and an output terminal coupled to the control transistor

(20) The electronic apparatus according to (19), further comprising a switch circuit coupled to the second input terminal of the first amplifying circuit, wherein the switch circuit is configured to couple the second input terminal of the first amplifying circuit to the first reference signal or a second reference signal.

(21) The electronic apparatus according to (20), further comprising a reference signal generation circuit coupled to the switch circuit.

(22) The electronic apparatus according to (21), wherein the reference signal generation circuit is configured to provide the first reference signal and the second reference signal.

(23) The electronic apparatus according to any one of (19) through (22), further comprising a second amplifying circuit, wherein a first input terminal of the second amplifying circuit is coupled to the select transistor.

(24) The electronic apparatus according to (23), wherein a second input terminal of the second amplifying circuit is configured to receive a second reference signal different from the first reference signal.

(25) The electronic apparatus according to (23) or (24), further comprising a switch circuit configured to selectively couple an output of the first amplifying circuit or an output of the second amplifying circuit to the control transistor.

(26) The electronic apparatus according to (24) or (25), further comprising a reference signal generation circuit configured to provide the first reference signal and the second reference signal.

(27) The electronic apparatus according to any one of (24) through (26), wherein a first output of the reference signal generation circuit is coupled to the second input terminal of the first amplifying circuit and a second output of the reference signal generation circuit is coupled to the second input terminal of the second amplifying circuit.

(28) The electronic apparatus according to any one of (23) through (27), wherein the first input terminal of the second amplifying circuit is coupled to the select transistor via a second signal line.

REFERENCE SIGNS LIST