Imaging device, endoscope, and imaging method
An imaging device includes two or more pixels and a voltage generation circuit. Each of the two or more pixels includes a photoelectric conversion element and a transistor. The photoelectric conversion element is configured to perform photoelectric conversion and generate an electric charge in accordance with an amount of received light. The transistor is driven by using a driving voltage. The voltage generation circuit is configured to generate the driving voltage that is lower than the power source voltage and gradually decreases.
1 . An imaging device configured to operate by using a power source voltage, the imaging device comprising:
two or more pixels, each of the pixels including:
a photoelectric conversion element configured to perform photoelectric conversion and generate an electric charge in accordance with an amount of received light; and
a transistor driven by using a driving voltage; and
a voltage generation circuit configured to generate the driving voltage that is lower than the power source voltage and gradually decreases,
wherein the voltage generation circuit includes:
a capacitor configured to hold a voltage; and
a voltage-current conversion circuit configured to convert the voltage held in the capacitor into a current,
wherein the voltage-current conversion circuit is configured to start conversion into the current after the power source voltage is held in the capacitor, and
wherein the voltage held in the capacitor gradually decreases and is output as the driving voltage while the voltage-current conversion circuit converts the voltage held in the capacitor into the current.
2 . The imaging device according to claim 1 ,
wherein the imaging device is driven by using a clock signal, and
wherein the voltage generation circuit is configured to generate the driving voltage included in a predetermined voltage range from a first timing synchronized with the clock signal to a second timing that is synchronized with the clock signal and is different from the first timing.
3 . The imaging device according to claim 1 ,
wherein each of the two or more pixels includes a floating diffusion configured to hold the electric charge generated by the photoelectric conversion element, and
wherein the transistor is configured to transfer the electric charge generated by the photoelectric conversion element to the floating diffusion.
4 . The imaging device according to claim 1 , comprising two or more of the voltage generation circuits,
wherein the two or more pixels are disposed in a matrix shape including two or more rows and two or more columns, and
wherein each of the two or more of the voltage generation circuits is disposed so as to correspond to any one of the two or more rows.
5 . The imaging device according to claim 4 , comprising a vertical selection circuit configured to output a signal for each row of the two or more rows,
wherein each of the two or more of the voltage generation circuits is configured to output the driving voltage to a pixel included in the two or more pixels when the signal output from the vertical selection circuit has been received.
6 . The imaging device according to claim 4 ,
wherein each of the two or more of the voltage generation circuits includes:
a capacitor configured to hold a voltage; and
a voltage-current conversion circuit configured to convert the voltage held in the capacitor into a current,
wherein the voltage-current conversion circuit is configured to start conversion into the current after the power source voltage is held in the capacitor, and
wherein the voltage held in the capacitor gradually decreases and is output as the driving voltage while the voltage-current conversion circuit converts the voltage held in the capacitor into the current.
7 . The imaging device according to claim 1 ,
wherein the imaging device operates by using a reference voltage lower than the power source voltage, and
wherein the driving voltage is lower than the power source voltage and is higher than the reference voltage.
8 . The imaging device according to claim 1 ,
wherein the imaging device operates by using a reference voltage lower than the power source voltage, and
wherein the driving voltage gradually decreases from a first voltage lower than the power source voltage to a second voltage that is lower than the first voltage and is higher than the reference voltage.
9 . An endoscope, comprising:
a scope to be inserted into a living body; and
the imaging device according to claim 1 ,
wherein the imaging device is disposed in a distal end of the scope.
10 . An imaging method using an imaging device that includes two or more pixels and operates by using a power source voltage, the imaging method comprising an imaging step,
wherein each of the two or more pixels includes:
a photoelectric conversion element configured to perform photoelectric conversion and generate an electric charge in accordance with an amount of received light; and
a transistor driven by using a driving voltage, and
wherein the imaging step includes:
generating, by using a voltage generation circuit, the driving voltage that is lower than the power source voltage and gradually decreases; and
outputting the driving voltage to the transistor,
wherein the voltage generation circuit includes:
a capacitor configured to hold a voltage; and
a voltage-current conversion circuit configured to convert the voltage held in the capacitor into a current,
wherein the voltage-current conversion circuit is configured to start conversion into the current after the power source voltage is held in the capacitor, and
wherein the voltage held in the capacitor gradually decreases and is output as the driving voltage while the voltage-current conversion circuit converts the voltage held in the capacitor into the current.
11 . An imaging device configured to operate by using a power source voltage, the imaging device comprising:
two or more pixels, each of the pixels including:
a photoelectric conversion element configured to perform photoelectric conversion and generate an electric charge in accordance with an amount of received light; and
a transistor driven by using a driving voltage; and
two or more voltage generation circuits, each of the voltage generation circuits being configured to generate the driving voltage that is lower than the power source voltage and gradually decreases,
wherein the two or more pixels are disposed in a matrix shape including two or more rows and two or more columns,
wherein each of the two or more voltage generation circuits is disposed so as to correspond to any one of the two or more rows,
wherein the imaging device comprises a vertical selection circuit configured to output a signal for each row of the two or more rows, and
wherein each of the two or more voltage generation circuits is configured to output the driving voltage to a pixel included in the two or more pixels when the signal output from the vertical selection circuit has been received.