Solid-state imaging device and method of driving solid-state imaging device

1. A method of driving a solid-state imaging device including a photoelectric conversion unit that generates charges by photoelectric conversion and an amplifier unit that comprises an input node, the method comprising:

setting a voltage of the input node to a first voltage by using logarithmic compression to convert a current generated by charges overflowing from the photoelectric conversion unit to the input node into a voltage corresponding to the current;

transferring charges from the photoelectric conversion unit to the input node;

setting a voltage of the input node to a second voltage by converting the charges transferred to the input node into a voltage corresponding to the charges;

at the amplifier unit, outputting a first signal based on the first voltage and a second signal based on the second voltage;

performing the logarithmic compression by using a diode having a first node connected to the input node and a second node supplied with a first power supply voltage that is different from a second power supply voltage to be supplied to the photoelectric conversion unit; and

acquiring, as a reference signal for the first signal, an output of the amplifier unit when the input node is set to a third voltage defined in accordance with a threshold voltage of the diode.

2. The method of driving the solid-state imaging device according to claim 1 further comprising setting the input node to the third voltage by draining charges of the input node and turning off the diode after setting the input node to a fourth voltage used for setting the diode to an operational point that is higher than the threshold voltage.

3. The method of driving the solid-state imaging device according to claim 1 further comprising acquiring, as a reference signal for the second signal, an output of the amplifier unit when the input node is set to a predetermined reset voltage.

4. A method of driving a solid-state imaging device having a photoelectric conversion unit that generates charges by photoelectric conversion and an amplifier unit that comprises an input node, the method comprising:

setting a voltage of the input node to a first voltage by using logarithmic compression to convert a current generated by charges overflowing from the photoelectric conversion unit to the input node into a voltage corresponding to the current;

transferring charges from the photoelectric conversion unit to the input node;

setting a voltage of the input node to a second voltage by converting the charges transferred to the input node into a voltage corresponding to the charges;

at the amplifier unit, outputting a first signal based on the first voltage and a second signal based on the second voltage;

performing the logarithmic compression by using a MOS transistor connected to the input node, the MOS transistor including a source connected to the input node, a drain to which a predetermined voltage is supplied, and a gate to which a control signal that controls an operation is supplied;

acquiring, as a reference signal for the first signal, an output of the amplifier unit when the input node is set to a third voltage defined in accordance with a threshold voltage of the MOS transistor when the MOS transistor operates in a sub-threshold region; and

setting the input node to the third voltage by, after setting the input node to a fourth voltage with the fourth voltage being supplied to the drain and the MOS transistor being turned on, switching a voltage supplied to the drain from the fourth voltage to a fifth voltage that is higher than the fourth voltage to drain charges of the input node with a control signal being supplied to the gate that causes the MOS transistor to operate in the sub-threshold region and turning off the MOS transistor.

5. A solid-state imaging device comprising: a photoelectric conversion unit that generates charges by photoelectric conversion; a transfer unit connected to the photoelectric conversion unit; an amplifier unit having an input node connected to the transfer unit; a logarithmic compression conversion unit connected to the input node; and a charge-to-voltage conversion unit connected to the input node,

wherein when a current generated by charges overflowing from the photoelectric conversion unit to the input node with the transfer unit being not conductive is converted into a voltage corresponding to the current by logarithmic compression performed by the logarithmic compression conversion unit, a voltage of the input node is a first voltage,

wherein when charges transferred from the photoelectric conversion unit to the input node in response to conduction of the transfer unit are converted into a voltage corresponding to the charges by the charge-to-voltage conversion unit, a voltage of the input node is a second voltage,

wherein the amplifier unit outputs a first signal based on the first voltage and a second signal based on the second voltage,

wherein the logarithmic compression conversion unit includes a diode having a first node connected to the input node and a second node supplied with a first power supply voltage that is different from a second power supply voltage to be supplied to the photoelectric conversion unit, and

wherein the first voltage is a voltage corresponding to a voltage of the input node that changes due to the current flowing to the diode whose operational point is set in a sub-threshold region.

6. The solid-state imaging device according to claim 5 , wherein the diode is a p-n junction diode.

7. The solid-state imaging device according to claim 5 , wherein the diode is a MOS diode in which a gate and a drain of a MOS transistor are short-circuited.

8. The solid-state imaging device according to claim 5 , wherein the logarithmic compression conversion unit further includes a switch provided between the diode and the input node.

9. The solid-state imaging device according to claim 5 ,

wherein the logarithmic compression conversion unit includes a MOS transistor connected to the input node, and

wherein the first voltage corresponds to a voltage of the input node that charges in response to the current flowing to the MOS transistor whose operational point is set in a sub-threshold region.

10. The solid-state imaging device according to claim 9 , wherein the MOS transistor is a reset transistor configured to reset the input node.

11. The solid-state imaging device according to claim 5 , wherein the charge-to-voltage conversion unit is a capacitance component coupled to the input node.

12. The solid-state imaging device according to claim 5 further comprising a signal processing unit that performs predetermined signal processing on each of the first signal and the second signal.

13. The solid-state imaging device according to claim 12 , wherein the signal processing unit is configured to

output the second signal when the second voltage does not exceed a predetermined value in accordance with a predetermined charge amount, and

combine and outputs the first signal and the second signal when the second voltage exceeds the predetermined value.

14. An imaging system comprising:

the solid-state imaging device according to claim 5 ; and

a signal processing unit that processes signals output from the solid-state imaging device.

15. The imaging system according to claim 14 , wherein the signal processing unit is configured to

output the second signal when the second voltage does not exceed a predetermined value in accordance with a predetermined charge amount, and

combine and outputs the first signal and the second signal when the second signal exceeds the predetermined value.

16. A movable object comprising:

the solid-state imaging device according to claim 5 ;

a distance information acquisition unit that acquires distance information on a distance to an object, from a parallax image based on signals output from the solid-state imaging device; and

a control unit that controls the movable object based on the distance information.

17. A solid-state imaging device comprising:

a photoelectric conversion unit supplied with a first power supply voltage that generates charges by photoelectric conversion;

a transfer unit connected to the photoelectric conversion unit;

an amplifier unit having an input node connected to the transfer unit;

a diode having a first node connected to the input node and a second node supplied with a second power supply voltage different from the first power supply voltage; and

a charge-to-voltage conversion unit connected to the input node,

wherein when a current generated by charges overflowing from the photoelectric conversion unit to the input node with the transfer unit being not conductive is converted into a voltage corresponding to the current flowing via the diode, a voltage of the input node is a first voltage,

wherein when charges transferred from the photoelectric conversion unit to the input node in response to conduction of the transfer unit are converted into a voltage corresponding to the charges by the charge-to-voltage conversion unit, a voltage of the input node is a second voltage, and

wherein the amplifier unit outputs a first signal based on the first voltage and a second signal based on the second voltage.

18. The solid-state imaging device according to claim 17 , wherein the first voltage is a voltage corresponding to a voltage of the input node that changes due to the current flowing to the diode whose operational point is set in a sub-threshold region.

19. An imaging system comprising:

the solid-state imaging device according to claim 17 ; and

a signal processing unit that processes signals output from the solid-state imaging device.

20. A movable object comprising:

the solid-state imaging device according to claim 17 ;

a distance information acquisition unit that acquires distance information on a distance to an object, from a parallax image based on signals output from the solid-state imaging device; and

a control unit that controls the movable object based on the distance information.

21. A solid-state imaging device comprising:

a photoelectric conversion unit supplied with a first power supply voltage that generates charges by photoelectric conversion;

a transfer unit connected to the photoelectric conversion unit;

an amplifier unit having an input node connected to the transfer unit;

a transistor having a first node connected to the input node and a second node supplied with a second power supply voltage different from the first power supply voltage; and

a charge-to-voltage conversion unit connected to the input node,

wherein when a current generated by charges overflowing from the photoelectric conversion unit to the input node with the transfer unit being not conductive is converted into a voltage corresponding to the current flowing via the transistor in a sub-threshold region, a voltage of the input node is a first voltage,

wherein when charges transferred from the photoelectric conversion unit to the input node in response to conduction of the transfer unit are converted into a voltage corresponding to the charges by the charge-to-voltage conversion unit, a voltage of the input node is a second voltage, and

wherein the amplifier unit outputs a first signal based on the first voltage and then outputs a second signal based on the second voltage.

22. The solid-state imaging device according to claim 21 , wherein the transistor further performs a reset operation of the input node.

23. An imaging system comprising:

the solid-state imaging device according to claim 21 ; and

a signal processing unit that processes signals output from the solid-state imaging device.

24. A movable object comprising:

the solid-state imaging device according to claim 21 ;

a distance information acquisition unit that acquires distance information on a distance to an object, from a parallax image based on signals output from the solid-state imaging device; and

a control unit that controls the movable object based on the distance information.