IMAGING APPARATUS, IMAGING SYSTEM, AND METHOD FOR CONTROLLING IMAGING APPARATUS

• US 20130082166A1
• Filed: 09/20/2012
• Published: 04/04/2013
• Est. Priority Date: 09/29/2011
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kameshima, Toshio, Yagi, Tomoyuki, Takenaka, Katsuro, Sato, Sho, Iwashita, Atsushi, Okada, Hideyuki, Sugawara, Eriko
• Granted Patent: US 8,847,138 B2
• Time in Patent Office: Days
• US Class Current: 250/208.1
• CPC Class Codes: A61B 6/00 Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment instruments measuring radiation intensity for application in the field of nuclear medicine, e.g. in vivo counting, G01T1/161; apparatus for taking X-ray photographs G03B42/02
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/487 involving fluoroscopy
• CPC Class Codes: G01T 1/247 Detector read-out circuitry for processing gain or off-set correction H04N
• CPC Class Codes: H04N 25/62 Detection or reduction of noise due to excess charges produced by the exposure, e.g. smear, blooming, ghost image, crosstalk or leakage between pixels
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 5/32 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 Class Codes: H04N 5/3205 using subtraction imaging techniques
• CPC Class Codes: H04N 5/321 with video transmission of fluoroscopic images

Abstract

An imaging apparatus includes a detector having a plurality of conversion elements for converting radiation or light into an electric charge, a power supply unit that supplies a first voltage to the conversion element in a first imaging operation, and a control unit that controls the detector and the power supply unit. During a period between the first imaging operation and a second imaging operation, the control unit controls to perform a first inter-imaging operation in which a second voltage different from the first voltage is supplied to the conversion element, and, subsequently to the first inter-imaging operation, a second inter-imaging operation in which a third voltage different from the first and the second voltages is supplied to the conversion element. The absolute value of the difference between the third and the first voltages is smaller than the absolute value of the difference between the second and the first voltages.

Claims

1. An imaging apparatus comprising:

a detector including a plurality of conversion elements each having a first electrode, a second electrode, and a semiconductor layer disposed between the first electrode and the second electrode and converting radiation or light into charge, the detector performing an imaging operation of outputting an electrical signal based on the charge;

a power supply unit that supplies a first voltage to the conversion elements for enabling the conversion elements to convert the radiation or light into the electric charge in the imaging operation to the conversion elements; and

a control unit that controls the detector and the power supply unit,

wherein the control unit controls the detector and the power supply unit to perform a first inter-imaging operation in which a second voltage different from the first voltage is supplied to the conversion elements, during a period between, in the imaging operation which is performed a plurality of times, a first imaging operation and a second imaging operation subsequent to the first imaging operation, and a second inter-imaging operation in which a third voltage different from the first voltage and the second voltage is supplied, during the period, subsequently to the first inter-imaging operation, and

wherein the absolute value of the difference between the third voltage and the first voltage is smaller than the absolute value of the difference between the second voltage and the first voltage.

2. The imaging apparatus according to claim 1, wherein each of the conversion elements includes a photodiode, and

wherein the first voltage is a reverse voltage.

3. The imaging apparatus according to claim 2, wherein the second voltage is a reverse voltage larger than the first voltage, and

wherein the third voltage is a reverse voltage smaller than the first voltage or a reverse voltage larger than the first voltage and smaller than the second voltage.

4. The imaging apparatus according to claim 2, wherein the second voltage is a reverse voltage smaller than the first voltage, and

wherein the third voltage is a reverse voltage smaller than the first voltage or a reverse voltage larger than the first voltage.

5. The imaging apparatus according to claim 2, wherein the second voltage is a forward voltage, and

wherein the third voltage is a reverse voltage smaller than the first voltage or a reverse voltage larger than the first voltage.

6. The imaging apparatus according to claim 2, wherein the detector includes a detection unit having a plurality of pixels arranged in a matrix, each pixel including the conversion element and a switching element connected to the first electrode, a drive circuit that brings the switching element into a conductive state to output the electrical signal from the detection unit, a signal line that transmits the electrical signal, and a read circuit that reads the electrical signal via the signal line,

wherein the power supply unit includes a first power supply connected to the second electrode, and a second power supply connected to the signal line via the read circuit,

wherein the second power supply supplies a reference potential to the signal line, and

wherein the first power supply supplies a first potential to the second electrode in the imaging operation, supplies a second potential different from the first potential to the second electrode in the first inter-imaging operation, and supplies a third potential different from the first potential and the second potential in the second inter-imaging operation.

7. The imaging apparatus according to claim 1 wherein the conversion element is an MIS conversion element having the first electrode, the second electrode, the semiconductor layer, an insulating layer disposed between the first electrode and the semiconductor layer, and an impurity semiconductor layer disposed between the semiconductor layer and the second electrode, and

wherein the power supply unit supplies the second voltage or the third voltage between the first electrode and the second electrode in order to allow the detector to perform a refresh operation of causing electrons or holes in electron-hole pairs accumulated between the semiconductor layer and the insulating layer within charge generated in the semiconductor layer due to the first voltage being supplied to the conversion element to move towards the second electrode and annihilate.

8. The imaging apparatus according to claim 7, wherein the detector includes a detection unit having a plurality of pixels arranged in a matrix, each pixel including the conversion element and a switching element connected to the first electrode, a drive circuit that brings the switching element into a conductive state to output the electrical signal from the detection unit, a signal line that transmits the electrical signal, and a read circuit that reads the electrical signal via the signal line,

wherein the power supply unit includes a first power supply connected to the second electrode, and a second power supply connected to the signal line via the read circuit,

wherein the second power supply supplies a reference potential to the signal line, and

wherein the first power supply supplies a first potential to the second electrode in the imaging operation, supplies a second potential different from the first potential to the second electrode in the first inter-imaging operation, and supplies a third potential different from the first potential and the second potential in the second inter-imaging operation.

9. The imaging apparatus according to claim 8, wherein the impurity semiconductor layer is an n-type impurity semiconductor layer, and

wherein if the first potential is denoted by Vs, the second potential is denoted by Vr2, the third potential is denoted by Vr1, and the potential to be supplied from the second power supply to the signal line is denoted by Vref, the following relationships are satisfied:

Vs-Vref>

0

Vr1-Vref>

0

Vr2-Vref 0

Vs>

Vr1>

Vref>

Vr2.

10. The imaging apparatus according to claim 8, wherein the impurity semiconductor layer is an n-type impurity semiconductor layer, and

if the first potential is denoted by Vs, the second potential is denoted by Vr2, the third potential is denoted by Vr1, and the potential to be supplied from the second power supply to the signal line is denoted by Vref, the following relationships are satisfied:

Vs-Vref>

0

Vr1-Vref>

0

Vr2-Vref>

0

Vs>

Vr1>

Vr2>

Vref

0.8×

|Vs-Vref|≦

|Vr2-Vs|<

|Vs-Vref|

|Vr1-Vs|<

0.5×

|Vs-Vref|.

11. An imaging system comprising:

the imaging apparatus according to claim 1; and

a control computer that sends a control signal to the control unit.

12. A method for controlling an imaging apparatus which includes a detector including a plurality of conversion elements each having a first electrode, a second electrode, and a semiconductor layer disposed between the first electrode and the second electrode and converting radiation or light into an electric charge, the method comprising:

performing a first imaging operation for allowing the detector to output an electrical signal based on the charge converted from the radiation or light by the conversion element to which a first voltage for allowing the conversion element to convert radiation or light into charge has been supplied;

performing subsequently to the first imaging operation a first inter-imaging operation in which a second voltage different from the first voltage is supplied to the conversion element;

performing subsequently to the first inter-imaging operation a second inter-imaging operation in which a third voltage different from the first voltage and the second voltage is supplied to the conversion element; and

performing subsequently to the second inter-imaging operation a second imaging operation for allowing the detector to output an electrical signal based on the charge converted from radiation or light by the conversion element to which the first voltage has been supplied,

wherein the absolute value of the difference between the third voltage and the first voltage is smaller than the absolute value of the difference between the second voltage and the first voltage.

13. A method for controlling an imaging apparatus which includes a detector including a plurality of conversion elements for converting radiation or light into an electric charge and a power supply unit for supplying voltage to the conversion elements, the method comprising:

supplying a first voltage to the conversion elements for enabling the conversion elements to convert the radiation or light into the electric charge in a first imaging operation of outputting an electrical signal based on the electric charge; and

controlling the detector and the power supply unit to perform a first inter-imaging operation in which a second voltage different from the first voltage is supplied to the conversion elements, during a period between the first imaging operation and a second imaging operation subsequent to the first imaging operation, and a second inter-imaging operation in which a third voltage different from the first voltage and the second voltage is supplied, during the period, subsequently to the first inter-imaging operation,

wherein the absolute value of the difference between the third voltage and the first voltage is smaller than the absolute value of the difference between the second voltage and the first voltage.