Solid-state imaging device, signal processing method for the same, and imaging apparatus

1. A solid-state imaging device, comprising:

a pixel array unit constituted by arranging unit pixels in matrix, each of said unit pixels including a photoelectric conversion unit configured to convert an optical signal into signal charges, a transfer element configured to transfer the signal charges obtained through photoelectric conversion in said photoelectric conversion unit, and output means configured to output the signal charges transferred by said transfer element;

driving means configured to read out the signal charges accumulated in said photoelectric conversion unit for an accumulation period of time of one unit and transferred at least in two batches by said transfer element through said output means;

signal processing means configured to execute addition processing for a plurality of output signals read out on a partition basis from said unit pixel;

level determining means configured to compare each of signal levels of the plurality of output signals with a reference level; and

control means configured to instruct said signal processing means to execute the addition processing for the output signals, having the signal levels each being equal to or higher than the reference level, of the plurality of output signals in accordance with a determination result obtained from said level determining means.

2. The solid-state imaging device according to claim 1 , wherein when each of the signal levels of the plurality of output signals is lower than the reference level, said control means instructs said signal processing means to stop the addition processing.

3. The solid-state imaging device according to claim 2 , wherein when each of the signal levels of the plurality of output signals is lower than the reference level, said control means instructs said signal processing means to stop the addition processing for the subsequent output signals in and after that time transferred on the partition transfer basis in said output means.

4. The solid-state imaging device according to claim 1 , wherein when each of the signal levels of the plurality of output signals is equal to or higher than the reference level, said control means instructs said signal processing means to start the addition processing.

5. The solid-state imaging device according to claim 4 , wherein when each of the signal levels of the plurality of output signals is equal to or higher than the reference level, said control means resets the output signals read out in and before that time or an addition result thereof.

6. The solid-state imaging device according to claim 1 , wherein said signal processing means includes analog-to-digital conversion means for executing analog-to-digital conversion processing for the plurality of output signals.

7. The solid-state imaging device according to claim 6 , wherein when each of the signal levels of the plurality of output signals is lower than the reference level, said control means instructs said signal processing means to stop the analog-to-digital conversion processing.

8. The solid-state imaging device according to claim 6 , wherein when each of the signal levels of the plurality of output signals is equal to or higher than the reference level, said control means instructs said signal processing means to start the analog-to-digital conversion processing.

9. The solid-state imaging device according to claim 6 , wherein said analog-to-digital conversion means includes:

comparing means configured to compare each of the plurality of signals with a reference signal; and

counting means configured to carry out an operation for performing counting by a count value corresponding to a comparison result obtained from said comparing means.

10. The solid-state imaging device according to claim 9 , wherein said analog-to-digital conversion means executes the analog-to-digital conversion processing and the addition processing in parallel in accordance with the counting operation by said counting means.

11. The solid-state imaging device according to claim 9 , wherein said counting means carries out up-count or down-count by the count value corresponding to the comparison result obtained from said comparing means.

12. The solid-state imaging device according to claim 11 , wherein said analog-to-digital conversion means obtains a difference between a reset level and the signal level obtained from said unit pixel in accordance with the up-count or the down-count by said counting means.

13. The solid-state imaging device according to claim 1 , wherein said output means includes a charge-to-voltage conversion unit configured to convert the signal charges transferred by said transfer element into a voltage, and a parasitic capacitance is set as being small so that a maximum quantity of charges transferred by said charge-to-voltage conversion unit is less than a maximum quantity of charges accumulable in said photoelectric conversion unit.

14. A signal processing method for a solid-state imaging device comprising:

a pixel array unit constituted by arranging unit pixels in matrix, each of said unit pixels including a photoelectric conversion unit configured to convert an optical signal into signal charges, a transfer element configured to transfer the signal charges obtained through photoelectric conversion in said photoelectric conversion unit, and an output section configured to output the signal charges transferred by said transfer element;

driving means configured to read out the signal charges accumulated in said photoelectric conversion unit for an accumulation period of time of one unit and transferred at least in two batches by said transfer element through said output section;

said solid-state imaging device executing addition processing for a plurality of output signals read out on a partition basis from said unit pixel;

said signal processing method including the steps of:

comparing each of the signal levels of the plurality of output signals with a reference level; and

executing the addition processing for the output signals, having the signal levels each being equal or higher than the reference level, of the plurality of output signals in accordance with a comparison result.

15. The signal processing method for a solid-state imaging device according to claim 14 , wherein when each of the signal levels of the plurality of output signals is lower than the reference level, the addition processing is stopped.

16. The signal processing method for a solid-state imaging device according to claim 14 , wherein when each of the signal levels of the plurality of output signals is equal to or higher than the reference level, the addition processing is started.

17. An imaging apparatus, comprising:

a solid-state imaging device constituted by arranging unit pixels in matrix, each of said unit pixels including a photoelectric conversion unit configured to convert an optical signal into signal charges, a transfer element configured to transfer the signal charges obtained through photoelectric conversion in said photoelectric conversion unit, and output means configured to output the signal charges transferred by said transfer element; and

an optical system configured to focus an incident light onto an imaging area of said solid-state imaging device;

wherein said solid-state imaging device includes:

driving means configured to read out the signal charges accumulated in said photoelectric conversion unit for an accumulation period of time of one unit and transferred at least in two batches by said transfer element through said output means;

signal processing means configured to execute addition processing for a plurality of output signals read out on a partition basis from said unit pixel;

level determining means configured to compare each of signal levels of the plurality of output signals with a reference level; and

control means configured to instruct said signal processing means to execute the addition processing for the output signals, having the signal levels each being equal to or higher than the reference level, of the plurality of output signals in accordance with a determination result obtained from said level determining means.