Radiation imaging apparatus and control method of the same

Patent metadata

Field	Value
Publication number	US-2016366351-A1
Application number	US-201615181721-A
Country	US
Kind code	A1
Filing date	Jun 14, 2016
Priority date	Jun 15, 2015
Publication date	Dec 15, 2016
Grant date	—

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 configured to detect radiation; a readout unit configured to read out image data from the sensor array, and 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; 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, as offset data for the second mode, image data read out in the second mode by the readout unit from the sensor array while the sensor array is not irradiated, and performs, after the first control, second control which causes the holding unit to hold, as offset data for the first mode, image data read out in the first mode by the readout unit from the sensor array while the sensor array is not irradiated.

2 . The apparatus according to claim 1 , wherein
the first control includes: first sub control which, after irradiation to the sensor array is complete, causes the readout unit 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 second sub control which causes the holding unit 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 the second control includes: third sub control which, after the first control, causes the readout unit 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 fourth sub control which causes the holding unit 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 apparatus according to claim 2 , further comprising a processing unit configured to perform a correction process on image data read out in one of the first mode and the second mode by the readout unit 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 holding unit.

4 . The apparatus according to claim 2 , wherein
the sensor array includes a 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 controlling unit accumulates electric charge in the detecting element by turning off the transistor, and outputs the accumulated electric charge by turning on the transistor thereafter, and the readout unit 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 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 controlling unit performs a first operation of reading out image data by the readout unit from the sensor array while the sensor array is not irradiated, and employs the image data obtained by the first operation as offset data if each signal value forming the image data satisfies a predetermined reference, and performs the first operation again if each signal value forming the image data does not satisfy the predetermined reference.

6 . The apparatus according to claim 1 , wherein the control of holding offset data in the holding unit includes updating offset data already held in the holding unit by using the former offset data.

7 . The apparatus according to claim 6 , wherein the controlling unit updates offset data held in the holding unit if a predetermined condition is satisfied.

8 . The apparatus according to claim 7 , wherein the predetermined condition includes a condition that a predetermined time elapses since offset data is held in the holding unit or offset data in the holding unit is lastly updated.

9 . The apparatus according to claim 7 , further comprising a temperature measuring unit,
wherein the predetermined condition includes a condition that a change amount of a measurement value of the temperature measuring unit obtained since offset data is held in the holding unit or offset data in the holding unit is lastly updated is larger than a predetermined value.

10 . The apparatus according to claim 9 , wherein the temperature measuring unit is arranged in the sensor array and/or a vicinity thereof.

11 . The apparatus according to claim 1 , wherein
the readout unit includes, as operation modes, not less than three modes including the first mode, the second mode, and another mode different therefrom, and the controlling unit causes the readout unit 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.

12 . The apparatus according to claim 11 , wherein
the sensor array includes a plurality of sensors arranged on a substrate, and 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, the controlling unit determines for which one of the not less than two modes offset data is to be read out first, based on the binning number.

13 . The apparatus according to claim 11 , wherein 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 unit, the controlling unit determines for which one of the not less than two modes offset data is to be read out first, based on the signal amplification factor.

14 . The apparatus according to claim 11 , wherein
the sensor array includes a plurality of sensors arranged on a substrate, and 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 the plurality of sensors, the controlling unit determines for which one of the not less than two modes offset data is to be read out first, based on the number of sensors as the signal readout targets.

15 . The apparatus according to claim 11 , wherein
the sensor array includes a plurality of sensors arranged on a substrate, and if there are not less than two modes equal in period required to read out image data of one frame, the controlling unit determines for which one of the not less than two modes offset data is to be read out first, based on a binning number of a signal from each sensor if the not less than two modes are different in binning number, a signal amplification factor of the readout unit if the not less than two modes are equal in binning number and different in signal amplification factor of the readout unit, and a number of sensors as signal readout targets of the plurality of sensors if the not less than two modes are equal in both binning number and signal amplification factor and different in number of sensors.

16 . A control method of a radiation imaging apparatus including a sensor array configured to detect radiation, a readout unit configured to read out image

Assignees

• Canon Kk

Inventors

• Ryu Takuya
• Yagi Tomoyuki

Classifications

• H04N25/76

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

• H04N25/626 Primary

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

• H04N25/78

  Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters · CPC title

• H04N23/30

  for generating image signals from X-rays · CPC title

• H04N5/23245

  Electricity · mapped topic