Radiation image capturing apparatus, radiation image capturing system, and method of controlling radiation image capturing apparatus

1. A radiation image capturing apparatus, comprising:

an image capturing unit comprising a plurality of pixels and configured to capture a radiation image, a part of the plurality of the pixels which is used as a detection element configured to detect radiation for obtaining an accumulated value of irradiated radiation incident on the radiation image capturing apparatus separately from obtaining the radiation image, and

a processor configured to calculate the accumulated value of irradiated radiation based on a signal from the part of the plurality of the pixels, wherein the processor is configured to:

perform an operation of repeatedly resetting the plurality of the pixels before receiving an exposure request from a user;

perform a reset operation of resetting the part of the plurality of pixels in accordance with the exposure request, where pixels, of the plurality of the pixels, other than the part of the plurality of the pixels are not reset; and

calculate the accumulated value of irradiated radiation based on the signal from the part of the plurality of the pixels after the reset operation of resetting the part of the plurality of the pixels.

2. The radiation image capturing apparatus according to claim 1 , wherein the image capturing unit comprises a pixel array where the plurality of pixels are arranged.

3. The radiation image capturing apparatus according to claim 1 , wherein the radiation image capturing apparatus is configured to perform a first readout operation for calculating the accumulated value of irradiated radiation by repeatedly reading out the signal from the part of the plurality of the pixels, and

a time from a start of resetting in the reset operation to a start of a first signal readout in the first readout operation is the same as a time in the first readout operation from a start of a signal readout to a start of a next readout from the detection element.

4. The radiation image capturing apparatus according to claim 3 , wherein a time in the operation of repeatedly resetting the plurality of the pixels from a start of resetting to a start of next resetting is not shorter than the time in the first readout operation from the start of the signal readout to the start of the next readout.

5. The radiation image capturing apparatus according to claim 4 , wherein

(i) the radiation image capturing apparatus is configured to output an irradiation stop signal for causing radiation irradiation to stop based on the accumulated value of irradiation radiation, and after causing the first readout operation to stop,

the radiation image capturing apparatus is configured to perform a third readout operation of reading out a signal from the image capturing unit,

the radiation image capturing apparatus is configured to perform a reset operation of resetting the image capturing unit after the third readout operation, and

the radiation image capturing apparatus is configured to perform a fourth readout operation of reading out a signal from the image capturing unit after the reset operation of resetting the image capturing unit,

(ii) the radiation image is obtained based on the signal obtained by the third readout operation and the signal obtained by the fourth readout operation, and

(iii) a time from a start of last resetting in the reset operation of repeatedly resetting the image capturing unit to a start of a signal readout in the third readout operation is the same as a time from a start of resetting in the reset operation of resetting the image capturing unit to a start of a signal readout in the fourth readout operation.

6. The radiation image capturing apparatus according to claim 1 , wherein the radiation image capturing apparatus is configured to perform a second readout operation of reading out the signal from the part of the plurality of the pixels at a time after the reset operation, and between the exposure request and radiation irradiation,

the radiation image capturing apparatus is configured to perform a first readout operation of detecting the amount of irradiated radiation by reading out the signal from the part of the plurality of the pixels repeatedly after the second readout operation, and

the radiation image capturing apparatus is configured to detect the amount of irradiated radiation based on the signal obtained by the first readout operation and the signal obtained by the second readout operation.

7. The radiation image capturing apparatus according to claim 6 , wherein a time from a start of resetting in the reset operation to a start of a signal readout in the second readout operation, a time from the start of the signal readout in the second readout operation to a start of a first signal readout in the first readout operation, and a time from a start of a signal readout to a start of a next readout from the part of the plurality of the pixels in the first readout operation are equal to each other.

8. The radiation image capturing apparatus according to claim 6 , wherein after the signal is read out from the part of the plurality of the pixels and before a next signal is read out in the first readout operation, the radiation image capturing apparatus is configured to:

perform a third readout operation of reading out a noise component of a signal line that transmits the signal output from the part of the plurality of the pixels, and

detect the amount of irradiated radiation based on the signal obtained by the first readout operation, the signal obtained by the second readout operation, and the noise component.

9. The radiation image capturing apparatus according to claim 1 , wherein an irradiation stop signal for causing radiation irradiation to stop is output based on a detected amount of irradiated radiation.

10. A radiation image capturing system, comprising:

a radiation image capturing apparatus according to claim 9 ;

a radiation source configured to perform radiation irradiation; and

an irradiation controller configured to control radiation irradiation, wherein

the irradiation controller is configured to cause the radiation source to perform radiation irradiation to the radiation image capturing apparatus in accordance with a start of detection of an amount of irradiation of radiation, and

the irradiation controller is configured to cause radiation irradiation from the radiation source to the radiation image capturing apparatus to stop in accordance with the irradiation stop signal.

11. A radiation image capturing system, comprising:

a radiation image capturing apparatus according to claim 1 ;

a radiation source configured to perform radiation irradiation; and

an irradiation controller configured to control radiation irradiation, wherein

the irradiation controller causes the radiation source to perform radiation irradiation to the radiation image capturing apparatus in accordance with a start of detection of an amount of irradiation of radiation.

12. The radiation image capturing apparatus according to claim 1 , wherein an irradiation stop signal for causing radiation to stop is output for an operation of automatic exposure control based on the accumulated value of irradiated radiation.

13. A method for controlling a radiation image capturing apparatus including an image capturing unit comprising a plurality of pixels and configured to capture a radiation image, a part of the plurality of the pixels which is used as a detection element configured to detect radiation for obtaining an accumulated value of irradiated radiation incident on the radiation image capturing apparatus separately from obtaining the radiation image, the method comprising the steps of:

repeatedly resetting the plurality of the pixels before receiving an exposure request from a user;

resetting the part of the plurality of the pixels in accordance with the exposure request where pixels, of the plurality of the pixels, other than the part of the plurality of the pixels are not reset; and

calculating the accumulated value of radiation incident on the radiation image capturing apparatus based on a signal from the part of the plurality of the pixels after the resetting the part of the plurality of the pixels.