Radiation imaging apparatus and control method of the same

Patent metadata

Field	Value
Publication number	US-10129493-B2
Application number	US-201615181721-A
Country	US
Kind code	B2
Filing date	Jun 14, 2016
Priority date	Jun 15, 2015
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

Abstract

A radiation imaging apparatus, comprising a sensor array, a readout unit, for reading out image data from the sensor array, which includes a first mode of reading out image data in a first period and a second mode of reading out image data in a second period shorter than the first period, a holding unit and a controlling unit, wherein, after irradiation to the sensor array is complete, the controlling unit performs first control which causes the holding unit to hold image data read out in the second mode while the sensor array is not irradiated, as offset data for the second mode, and then, performs second control which causes the holding unit to hold image data read out in the first mode while the sensor array is not irradiated, as offset data for the first mode.

First claim

What is claimed is:

1. A radiation imaging apparatus comprising:
a sensor array, on which a plurality of sensors are arrayed, configured to detect radiation;
readout circuitry configured to read out image data, based on signals from the plurality of sensors, from the sensor array, the readout circuitry including, as operation modes, a first mode of reading out image data of one frame in a first period, and a second mode of reading out image data of one frame in a second period shorter than the first period;
one or more processors; and
one or more memories configured to hold image data and storing instructions that, when executed by the one or more processors, cause the radiation imaging apparatus to:
perform, after irradiation to the sensor array is complete, first control which causes the readout circuitry in the second mode to read out image data while the sensor array is not irradiated, to update image data already held by the one or more memories as offset data for the second mode by using the former offset data, and
perform, after the first control is performed, second control which causes the readout circuitry in the first mode to read out image data while the sensor array is not irradiated, to update image data already held by the one or more memories as offset data for the first mode by using the former offset data.

2. The radiation imaging apparatus according to claim 1 , wherein the instructions, when executed by the one or more processors, cause the radiation imaging apparatus to:
in performing the first control:
perform first sub control which, after irradiation to the sensor array is complete, causes the readout circuitry to read out image data in the second mode from the sensor array while the sensor array is not irradiated, and simultaneously monitors whether an image lag in the readout image data falls within an allowable range; and
perform second sub control which causes the one or more memories to hold, as offset data for the second mode, image data found by the first sub control to have an image lag falling within the allowable range, and

in performing the second control:
perform third sub control which, after the first control, causes the readout circuitry to read out image data in the first mode from the sensor array while the sensor array is not irradiated, and simultaneously monitors whether an image lag in the readout image data falls within the allowable range; and
perform fourth sub control which causes the one or more memories to hold, as offset data for the first mode, image data found by the third sub control to have an image lag falling within the allowable range.

3. The radiation imaging apparatus according to claim 2 , wherein the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus to perform a correction process on image data read out in one of the first mode and the second mode by the readout circuitry from the irradiated sensor array, by using offset data for the one of the first mode and the second mode from the offset data held in the one or more memories.

4. The radiation imaging apparatus according to claim 2 , wherein:
the sensor array includes the plurality of sensors arranged on a substrate and each including a detecting element configured to detect radiation and a transistor connected to the detecting element,
the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus to accumulate electric charge in the detecting element by turning off the transistor, and output the accumulated electric charge by turning on the transistor thereafter,
the readout circuitry reads out image data corresponding to an amount of the output electric charge, and
a charge accumulation time in the second mode is shorter than that in the first mode.

5. The radiation imaging apparatus according to claim 2 , wherein in each of an operation from the first sub control to the second sub control and an operation from the third sub control to the fourth sub control,
the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus to:
perform a first operation which causes the readout circuitry to read out image data from the sensor array while the sensor array is not irradiated, and
employ the image data obtained by the first operation as offset data if each signal value forming the image data satisfies a predetermined reference, and perform the first operation again if each signal value forming the image data does not satisfy the predetermined reference.

6. The radiation imaging apparatus according to claim 1 , wherein the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus to update offset data held in the one or more memories if a predetermined condition is satisfied.

7. The radiation imaging apparatus according to claim 6 , wherein the predetermined condition includes a condition that a predetermined time elapses since offset data is held in the one or more memories or offset data in the one or more memories is lastly updated.

8. The radiation imaging apparatus according to claim 6 , further comprising a temperature sensor,
wherein the predetermined condition includes a condition that a change amount of a measurement value of the temperature sensor obtained since offset data is held in the one or more memories or offset data in the one or more memories is lastly updated is larger than a predetermined value.

9. The radiation imaging apparatus according to claim 8 , wherein the temperature sensor is arranged in the sensor array or a vicinity thereof.

10. The radiation imaging apparatus according to claim 1 , wherein
the readout circuitry includes, as operation modes, not less than three modes including the first mode, the second mode, and another mode different therefrom, and
the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus to cause the readout circuitry to read out offset data in each operation mode in order from one corresponding to a mode in which a period required to read out image data of one frame is shortest of the not less than three modes.

11. The radiation imaging apparatus according to claim 10 , wherein
the sensor array includes a plurality of sensors arranged on a substrate, and
the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus, if there are not less than two modes equal in period required to read out image data of one frame and different in binning number of a signal from each sensor, to determine for which one of the not less than two modes offset data is to be read out first, based on the binning number.

12. The radiation imaging apparatus according to claim 10 , wherein the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus, if there are not less than two modes equal in period required to read out image data of one frame and different in signal amplification factor of the readout circuitry, to determine for which one of the not less than two modes offset data is to be read out first, based on the signal amplification factor.

13. The radiation imaging apparatus according to claim 10 , wherein
the sensor array includes a plurality of sensors arranged on a substrate, and
the instructions, when executed by the one or more processors, further cause the radiation imaging apparatus, if there are not less than two modes equal in period required to read out image data of one frame and different in number of sensors as signal readout targets of

Assignees

• Canon Kk

Inventors

• Ryu Takuya
• Yagi Tomoyuki

Classifications

• H04N25/626 Primary

  Reduction of noise due to residual charges remaining after image readout, e.g. to remove ghost images or afterimages · CPC title

• H04N25/76

  Addressed sensors, e.g. MOS or CMOS sensors · CPC title

• H04N5/378

  Electricity · mapped topic

• H04N5/32

  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

• H04N5/3597 Primary

  Electricity · mapped topic