Radiation imaging apparatus and radiation imaging system

Patent metadata

Field	Value
Publication number	US-9470800-B2
Application number	US-201414189229-A
Country	US
Kind code	B2
Filing date	Feb 25, 2014
Priority date	Feb 28, 2013
Publication date	Oct 18, 2016
Grant date	Oct 18, 2016

Abstract

A radiation imaging apparatus includes a pixel array having pixels including conversion elements and switching elements, a bias line for supplying a bias potential to the conversion elements; driving lines for supplying a signal to control the switching elements, a driving unit for performing an initialization operation of supplying a driving signal to each driving line group, switching each driving signal from an OFF voltage to an ON voltage, and then returning the driving signal to the OFF voltage; an acquisition unit configured to acquire a plurality of times in each driving cycle a signal value representing a current flowing through the bias line; a calculation unit configured to calculate radiation information based on the signal values; and a determination unit configured to determine whether irradiation of the pixel array with radiation is present based on the radiation information.

First claim

What is claimed is:

1. A radiation imaging apparatus comprising:
a pixel array having a plurality of pixels arranged in a plurality of rows and a plurality of columns, each pixel including a conversion element for accumulating charge in accordance with radiation and a switching element for connecting the conversion element to a signal line;
a bias line for supplying a bias potential to the conversion elements of the plurality of pixels;
a plurality of driving lines for supplying a driving signal to control the switching elements of the plurality of pixels;
a driving unit configured to supply a driving signal to the plurality of driving lines in units of one or more driving lines and repeat an initialization operation comprising switching each driving signal from an OFF voltage at which the switching element is turned off, to an ON voltage at which the switching element is turned on, and then returning the driving signal to the OFF voltage;
an acquisition unit configured to acquire an effective value and a noise value in each driving cycle, the driving cycle being a time duration from the time when a driving signal to particular one or more driving lines is switched to the ON voltage to the time when a driving signal to a next one or more driving lines is switched to the ON voltage, the effective value representing a current flowing through the bias line upon supply of the ON voltage to at least one of the plurality of driving lines, and the noise value representing a current flowing through the bias line upon supply of the OFF voltage to each of the plurality of driving lines;
a calculation unit configured to calculate radiation information based on the effective value and the noise value; and
a determination unit configured to determine whether irradiation of said pixel array with radiation is present based on the calculated radiation information.

2. The apparatus according to claim 1 , wherein said driving unit is configured to return the driving signal supplied to the particular one or more driving lines to the OFF voltage a time interval before switching the driving signal to the next one or more driving lines to the ON voltage.

3. The apparatus according to claim 1 , wherein said calculation unit is configured to calculate the radiation information based on the effective value acquired in a particular driving cycle and at least one of the noise value acquired in the particular driving cycle and the noise value acquired in a driving cycle immediately preceding the particular driving cycle.

4. The apparatus according to claim 1 , wherein said calculation unit is configured to calculate the radiation information based on a difference between a value calculated from at least one effective value and a value calculated from at least one noise value, and
said determination unit is configured to make the determination by comparing the radiation information with a threshold.

5. The apparatus according to claim 4 , wherein said acquisition unit is configured to acquire the noise value a plurality of times in each driving cycle, and
said calculation unit is configured to calculate the value calculated from the at least one noise value, by weighting the plurality of noise values and adding the weighted noise values.

6. The apparatus according to claim 5 , wherein weights for the plurality of noise values become smaller as the time when a noise value is acquired becomes farther in time from the time when the effective value is acquired.

7. The apparatus according to claim 4 , wherein said acquisition unit is configured to acquire the effective value a plurality of times in each driving cycle, and
said calculation unit is configured to calculate the value calculated from the at least one effective value, by weighting the plurality of effective values and adding the weighted effective values.

8. The apparatus according to claim 1 , wherein said calculation unit is configured to calculate the radiation information based on the effective value and a noise value acquired a time interval after or before acquisition of the effective value.

9. The apparatus according to claim 1 , wherein said driving unit is configured to switch, to the OFF voltage, the driving signal to the particular one or more driving lines, and at the same time switch, to the ON voltage, the driving signal to the next one or more driving lines, and
said calculation unit is configured to calculate the radiation information based on the effective value acquired in a particular driving cycle and the effective value acquired in a driving cycle different from the particular driving cycle.

10. The apparatus according to claim 9 , wherein said calculation unit is configured to calculate the radiation information based on the effective value acquired in a particular driving cycle and at least one of the effective value acquired in a driving cycle immediately after the particular driving cycle and the effective value acquired in a driving cycle immediately before the particular driving cycle.

11. The apparatus according to claim 1 , wherein said calculation unit is configured to calculate the radiation information based on at least one signal value acquired by said acquisition unit upon lapse of a predetermined delay time after said driving unit switches, to the ON voltage, the driving signal to one or more driving lines and at least one signal value acquired after the acquisition of the at least one signal value.

12. The apparatus according to claim 11 , wherein the predetermined delay time is determined based on at least one of a time constant of said one or more driving lines and a time constant of said bias line.

13. The apparatus according to claim 12 , wherein the apparatus comprises a plurality of said bias lines and a plurality of said acquisition units arranged for said respective bias lines, and
the predetermined delay time is determined for each acquisition unit.

14. The apparatus according to claim 1 , further comprising a memory for storing the radiation information, wherein said determination unit is configured to determine whether irradiation of said pixel array with radiation is present based on a difference between the radiation information calculated in a particular driving cycle and radiation information which has been calculated in a driving cycle preceding the particular driving cycle for one or more driving lines to which the ON voltage has been supplied in the particular driving cycle and which has been stored in said memory.

15. The apparatus according to claim 1 , wherein said acquisition unit includes an A/D converter, and
the effective value includes a digital effective value obtained by sampling, by the A/D converter, an analog signal value representing a current flowing through said bias line.

16. The apparatus according to claim 1 , wherein said driving unit is configured to supply the driving signal so that at least one driving line to which the ON voltage is supplied in a particular driving cycle and at least one driving line to which the ON voltage is supplied in a next driving cycle are not adjacent to each other.

17. The apparatus according to claim 1 , wherein said driving unit sequentially switches, to the ON voltage, driving signals to odd-numbered driving lines as counted from one side of said pixel array, and then sequentially switches, to the ON voltage, driving signals to even-numbered driving lines as counted from the one side of said pixel array.

18. The apparatus according to claim 1 , wherein said driving unit is configured to supply driving signal to the plur

Assignees

• Canon Kk

Inventors

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

Classifications

• H04N5/3205

  using subtraction imaging techniques · CPC title

• G01T1/16 Primary

  Measuring radiation intensity (G01T1/29 takes precedence {; self-powered detectors G01T3/006; using an ionisation chamber filled with a liquid or solid, e.g. frozen liquid, dielectric G01T3/008}) · CPC title

• H04N25/30

  for transforming X-rays into image signals · CPC title

• H04N23/30

  for generating image signals from X-rays · 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