Method for controlling radiation image pickup apparatus, radiation image pickup apparatus, and radiation image pickup system

Patent metadata

Field	Value
Publication number	US-9329280-B2
Application number	US-201313934430-A
Country	US
Kind code	B2
Filing date	Jul 3, 2013
Priority date	Jul 6, 2012
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

A radiation image pickup apparatus includes a pixel array having pixels each including a conversion element and a switch element, a drive circuit for controlling the switch element between a conducting state and a non-conducting state, a detection unit for outputting a detection signal varying with the intensity of irradiation of the pixel array, and an arithmetic unit for calculating a start threshold value used to detect start of irradiation based on the signal output from the detection unit during a period when radiation is not emitted onto the pixel array in which the switch elements are sequentially set in a conducting state on a row-by-row basis by the drive circuit and the signal output from the detection unit during a period when radiation is emitted onto the pixel array in which the switch elements are sequentially set in a conducting state on a row-by-row basis by the drive circuit.

First claim

What is claimed is:

1. A method for controlling a radiation image pickup apparatus, the radiation image pickup apparatus including a pixel array having a plurality of pixels arranged in a matrix, a drive circuit, and a detection unit, each of the pixels including a conversion element and a switch element and converting radiation into an electric signal, the drive circuit controlling the switch element between a conducting state and a non-conducting state, the detection unit outputting a signal varying with an intensity of irradiation of the pixel array, the method comprising:
switching the radiation image pickup apparatus between a first mode and a second mode,
wherein in the first mode, a start threshold value used for detecting start of irradiation of the pixel array is calculated on the basis of the signal output from the detection unit during a period of time during which irradiation is not applied to the pixel array in which the switch elements of the plurality of pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit and the signal output from the detection unit during a period of time during which irradiation is applied to the pixel array in which the switch elements of the plurality of pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit, and
wherein in the second mode, the switch elements of the plurality of pixels are set in the non-conducting state by the drive circuit if a value of the signal output from the detection unit exceeds the start threshold value during a period of time during which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit after the first mode occurs.

2. The method for controlling a radiation image pickup apparatus according to claim 1 , wherein
the radiation image pickup apparatus further includes a storage unit for storing the start threshold value and a comparator for comparing the start threshold value stored in the storage unit with the value of the detection signal,
wherein the first mode involves a first step of storing the start threshold value in the storage unit, and
the second mode involves a second step of generating a signal used for controlling the start of irradiation using the comparator if, as a result of comparison performed by the comparator, the value of the signal output from the detection unit exceeds the start threshold value during a period of time during which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit after the first mode occurs.

3. The method for controlling a radiation image pickup apparatus according to claim 2 , wherein
the start threshold value is in a range between the highest value of the signal output from the detection unit during a period of time during which irradiation is not applied to the pixel array in which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit and the lowest value of the signal output from the detection unit during a period of time during which irradiation is applied to the pixel array in which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit.

4. The method for controlling a radiation image pickup apparatus according to claim 2 , wherein
the start threshold value is in a range between one of the highest value and an inflection point of a signal obtained by aligning a phase of a signal output from the detection unit during a period of time during which irradiation is not applied to the pixel array in which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit with a phase of a signal output from the detection unit during a period of time during which irradiation is applied to the pixel array in which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit and performing a differential process and the highest value of a signal output from the detection unit during a period of time during which irradiation is not applied to the pixel array in which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit.

5. The method for controlling a radiation image pickup apparatus according to claim 2 , further comprising:
calculating an end threshold value used for detecting end of irradiation of the pixel array on the basis of a signal output from the detection unit during a period of time during which irradiation is applied to the pixel array in which the switch elements of the pixels are set in the non-conducting state by the drive circuit;
storing the end threshold value in the storage unit; and
generating, in the second step, a signal used by the comparator for determining end of the irradiation when the comparator compares the value of the detection signal output from the detection unit during a period of time during which irradiation is applied to the pixel array in which the switch elements of the pixels are sequentially set in the conducting state on a row-by-row basis by the drive circuit with the end threshold value stored in the storage unit and if the value of the detection signal is lower than the end threshold value,
wherein the end threshold value is lower than the start threshold value.

6. The method for controlling a radiation image pickup apparatus according to claim 5 , wherein
after a predetermined period of time has elapsed since determination of end of irradiation in the second step, the drive circuit sequentially sets the switch elements of the plurality of pixels in the conducting state on a row-by-row basis, and
wherein the predetermined period of time is calculated in the first mode.

7. The method for controlling a radiation image pickup apparatus according to claim 2 , wherein
the radiation generating apparatus configured to emit radiation to the pixel array emits radiation under a plurality of irradiation conditions in the first mode,
wherein the first step involves storing a plurality of the start threshold values calculated for the plurality of irradiation conditions in the storage unit in association with the irradiation conditions, and
wherein the second step involves selecting, from among the plurality of the start threshold values, the start threshold value corresponding to the irradiation condition for irradiation of the pixel array in the second mode and generating a signal that determines start of irradiation on the basis of the selected start threshold value by using the comparator.

8. The method for controlling a radiation image pickup apparatus according to claim 2 , wherein
a plurality of radiation generating apparatuses each configured to emit radiation to the pixel array are provided,
wherein the first step involves storing a plurality of start threshold values calculated for the radiation generating apparatuses in the storage unit in association with the radiation generating apparatuses, and
wherein the second step involves selecting, from among the plurality of the start threshold values, the start threshold value corresponding to the radiation generating apparatus used in the second mode and generating a signal for determining start of irradiation on the basis of the selected start threshold value by using the comparator.

9. A method for controlling a radiation image pickup apparatus, the radiation image pickup apparatus controlling an operation performed by a pixel array having a plurality of pixels arranged in a matrix on the basis of a de

Assignees

• Canon Kk

Inventors

• Kameshima Toshio
• Yagi Tomoyuki
• Takenaka Katsuro
• Sato Sho
• Iwashita Atsushi
• Sugawara Eriko
• Okada Hideyuki

Classifications

• H04N25/63

  applied to dark current · CPC title

• H04N25/779

  Circuitry for scanning or addressing the pixel array · CPC title

• H04N5/32 Primary

  Transforming X-rays (cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30) · CPC title

• H10F39/803

  Pixels having integrated switching, control, storage or amplification elements · CPC title

• G01T1/17 Primary

  Circuit arrangements not adapted to a particular type of detector {(pulse-selection circuits H03K, G01R)} · CPC title