Method for removing of residual charge, X-ray imaging method and apparatus using the method

Patent metadata

Field	Value
Publication number	US-9961754-B2
Application number	US-201414476069-A
Country	US
Kind code	B2
Filing date	Sep 3, 2014
Priority date	Sep 4, 2013
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

A method of removing residual charge from a photoconductive material includes applying a first voltage to the photoconductive material to form an electrostatic field during a collection operation in which x-rays are irradiated onto the photoconductive material; and applying a second voltage to the photoconductor to reduce an amount of residual charge therein during a removal operation, the second voltage being different from the first voltage. In one or more example embodiments, the photoconductive material may include Mercury Iodine (Hgl 2 ).

First claim

What is claimed is:

1. A method of removing residual charges from a photoconductive material, the method comprising:
applying a first voltage between two electrodes to form an electrostatic field during a collection operation in which x-rays are irradiated onto the photoconductive material, wherein a first electrode directly contacts a first end of the photoconductive material and a second electrode directly contacts a second end of the photoconductive material, the second end being opposite to the first end; and
applying a second voltage between the two electrodes to reduce an amount of a residual charge in the photoconductive material during a removal operation,
wherein applying the second voltage includes applying the second voltage with a polarity that is opposite to a polarity of the first voltage and an absolute value of a magnitude of the second voltage smaller than a magnitude of the first voltage.

2. The method of claim 1 , wherein the first voltage has a magnitude of less than 300 volts (V) and the photoconductive material is a material configured to operate at the first voltage.

3. The method of claim 1 , wherein the photoconductive material includes Mercury Iodide HgI 2 .

4. The method of claim 1 , wherein applying the second voltage to the photoconductive material to reduce the amount of the residual charge comprises applying the second voltage to the photoconductive material in a form of a plurality of pulses.

5. The method of claim 1 , further comprising:
applying visible light to the photoconductive material during the removal operation.

6. The method of claim 5 , wherein applying visible light to the photoconductive material includes applying the visible light to the photoconductive material while the second voltage is applied.

7. The method of claim 1 , further comprising:
storing at least a portion of charges generated in the photoconductive material during the collection operation; and
reading the stored charges to form a first frame image prior to the removal operation.

8. A method of forming an x-ray image, the method comprising:
irradiating a target object with x-rays during a collection operation, at least a portion of the irradiated x-rays being transmitted through the target object onto a photoconductive material;
applying a first voltage between two electrodes to form an electrostatic field during the collection operation, wherein a first electrode directly contacts a first end of the photoconductive material and a second electrode directly contacts a second end of the photoconductive material, the second end being opposite to the first end; and
applying a second voltage between the two electrodes to reduce an amount of a residual charge in the photoconductive material therein during a removal operation, wherein applying the second voltage includes applying the second voltage with a polarity that is opposite to a polarity of the first voltage and an absolute value of a magnitude of the second voltage smaller than a magnitude of the first voltage.

9. The method of claim 8 , wherein the photoconductive material includes Mercury Iodide HgI 2 and a magnitude of the first voltage is less than 300 volts (V).

10. The method of claim 8 , further comprising:
storing at least a portion of charges generated in the photoconductive material during the collection operation; and
reading the stored charges to form a first frame image before the removal operation.

11. The method of claim 10 , wherein the residual charge is removed such that residual charges from the first frame image are not present in the photoconductive material during the forming of a second x-ray image such that the second x-ray image can be formed after the removal operation without effects of the residual charges from the first frame image and without an afterimage or an image distortion.

12. An x-ray detector comprising:
a photoconductor having a first surface and a second surface facing each other;
a common electrode directly contacting the first surface of the photoconductor;
at least one pixel electrode directly contacting the second surface of the photoconductor; and
a control unit configured to:
apply a first voltage to the photoconductor to form an electrostatic field during a collection operation in which x-rays are irradiated onto the photoconductor,
determine, as a function of a residual charge resulting from the collection operation, at least one of magnitude or polarity of a second voltage for reducing an amount of the residual charge, the second voltage being different from the first voltage, and
apply the second voltage to the photoconductor to reduce an amount of residual charge therein during a removal operation, the second voltage being different from the first voltage, wherein the control unit applies the second voltage with a polarity that is opposite to a polarity of the first voltage and an absolute value of a magnitude of the second voltage smaller than a magnitude of the first voltage.

13. The x-ray detector of claim 12 , wherein the first voltage has a magnitude of less than 300 volts (V) and the photoconductor is configured to operate at the first voltage.

14. The x-ray detector of claim 12 , wherein the photoconductor includes Mercury Iodide HgI 2 .

15. The x-ray detector of claim 12 , further comprising:
a bias voltage source connected between the common electrode and the at least one pixel electrode, the bias voltage source configured to generate the first voltage and the second voltage based on a control signal from the control unit.

16. The x-ray detector of claim 15 , further comprising:
a charging capacitor configured to store charges received from the pixel electrodes; and
a switch configured to provide the stored charges to a read-out circuit based on a gate voltage applied to the switch.

17. The x-ray detector of claim 15 , wherein the control unit is configured to instruct the bias voltage source to generate the second voltage such that the second voltage is applied to the photoconductor as a plurality of pulses.

18. The x-ray detector of claim 15 , wherein the control unit is configured to apply visible light to the photoconductor during the removal operation.

Assignees

• Samsung Electronics Co Ltd

Inventors

• Kim Young
• Kim Sunil
• Park Jaechul
• Lee Kangho

Classifications

• G01N23/04 Primary

  and forming images of the material · CPC title

• G03G15/222

  Machines for handling xeroradiographic images, e.g. xeroradiographic processors · CPC title

• H05G1/30 Primary

  Controlling · CPC title

• G01T1/24

  with semiconductor detectors · CPC title

• H01L27/14676

  Electricity · mapped topic