KR20140055797A

KR20140055797A - X-ray detector and method for driving the same

Info

Publication number: KR20140055797A
Application number: KR1020120123114A
Authority: KR
Inventors: 임조성
Original assignee: 주식회사 레이언스; (주)바텍이우홀딩스
Priority date: 2012-11-01
Filing date: 2012-11-01
Publication date: 2014-05-09

Abstract

The present invention relates to a driving method for an X-ray detector which defines X-ray detection pixels in a matrix shape having a light detecting capacitor and a light detecting element connected with a first bias terminal. The driving method comprises as follows: (a) a step of generating current from a light detecting element by visible rays converted from X-rays; (b) a step of charging the current generated from the light detecting element into a light detecting capacitor; (c) a step of outputting an image signal from the voltage charged into the light detecting capacitor; and (d) a step of removing the remaining charge of the light detecting element through a second bias terminal. At this time, to the bias terminal for removing the remaining charge, applied is higher voltage than the voltage applied to the other end of each of the light detecting elements which are not connected with a switch for removing the remaining charge. As a result, the driving method can prevent the ghost phenomenon where a previous image remains in the next image due to the remaining charge in the light detecting element.

Description

[0001] X-RAY DETECTOR AND METHOD FOR DRIVING THE SAME [0002]

The present invention relates to an X-ray detector and a driving method thereof, and more particularly, to an X-ray detector capable of suppressing a ghost phenomenon caused by a residual charge existing in a photodetector and a driving method thereof.

Medical diagnostic imaging techniques using X-rays, magnetic resonance imaging (MRI), x-ray computed tomography (CT), or similar techniques are rapidly improving with advances in computer technology. Generally, x-ray films or image intensifiers (I.I.) are used in X-ray diagnostic equipment. In the case of using an image amplifier, the x-ray irradiated to the patient is converted into an optical signal by an image amplifier, and the optical signal is converted into an electric signal by a TV camera. The electrical signal is converted from an analog signal to a digital signal and displayed on a TV monitor as an x-ray image.

The real-time image of the patient could not be seen by the method using the x-ray film, but the real image of the patient could be seen by the image amplifier as described above. Furthermore, since real-time images of such patients are collected as digital signals in an image amplifier, various kinds of image processing techniques can be applied to analyze the images more finely and accurately.

With advances in technology, traditional video amplifiers have been replaced by x-ray detectors. The X-ray detector is usually constituted by a two-dimensional X-ray detecting element having a matrix arrangement of M (M is a positive integer) × N (N is a positive integer), and the X- Compared with diagnostic equipment using amplifiers, it has been widely used because it has improved image quality and superior stability.

Hereinafter, a configuration of a general X-ray detector and a driving method thereof will be briefly described with reference to FIGS. 1 to 3 attached hereto.

FIG. 1 is a block diagram schematically showing a general X-ray detector. FIG. 2 is a schematic block diagram showing details of one X-ray detecting element among a plurality of X-ray detecting elements arranged in an M.times.N matrix in the X- FIG. 3 is a waveform diagram for explaining a driving method of a conventional X-ray detector.

1, a typical X-ray detector 10 includes an X-ray detecting panel 100, a bias driving unit 200, a gate driving unit 300, and a signal processing unit 400.

First, the X-ray detecting panel 100 includes a plurality of M (M is a positive integer, only four are shown for simplicity in the drawing) formed along the first direction D1 from the bias driver 200, N lines (N is a positive integer, in this embodiment, only four are shown for the sake of simplicity in the drawing) formed by intersecting the line BL and the bias line BL along the second direction D2 from the gate driver 300 The first switch Q1 is an X-ray detecting switch used for detecting an X-ray, and the M × N (first switch) Q1 is a PD capacitor The x-ray detection pixels 100 'are arranged in a matrix form.

3, the X-ray emitted from the X-ray generator (not shown) passes through the subject and is incident on the X-ray detector 10 during a period during which the integration signal is turned on. At this time, the X-ray passes through a scintillator layer (not shown) disposed on the X-ray detecting panel 100 of the X-ray detector 10 and is converted into visible light. The converted visible light is detected by the X- Is incident on the photodetector element PD of the X-ray detecting pixel 100 'arranged in a matrix form on the panel 100. At this time, the scintillator layer may be composed of gadolinium oxysulfide (GOS) or the like.

The photodetecting device PD generates a current corresponding to the light quantity of the incident visible light.

In such a state, when the first reset signal Reset is applied to the gate ends of all the reset switches Q2 corresponding to each of the M X-ray detecting pixels 100 'arranged in the first gate line GL1, All of the reset switches Q2 corresponding to each of the X-ray detecting pixels 100 'disposed in the first gate line GL1 are turned on.

As such, when the second reset signal RST is turned on with all of the reset switches Q2 corresponding to each of the M X-ray detecting pixels 100 'disposed in the first gate line GL1 turned on, (Hereinafter referred to as an offset voltage) corresponding to the inherent offset value in the analog circuit is supplied to the capacitor Crst provided at the reset output terminal RST of the video signal output unit 420 through the data line DL Is charged.

The second reset signal RST is turned off while the M reset switches Q2 arranged in the first gate line GL1 are all kept turned on and the gate driver 300 is turned off, When the gate signal Vgate is applied to the line GL1, the M first switches Q1 whose gate terminals are connected to the first gate line GL1 are turned on so that the currents Is charged into the PD capacitor Cp. That is, the photodetector element PD generates a current corresponding to the amount of visible light, and the PD capacitor Cp is charged to a high voltage according to the generated amount of current

Then, when the gate signal Vgate is turned off and the video signal SIG is turned on while the M reset switches Q2 arranged in the first gate line GL1 are all kept turned on, The combined voltage of the data voltage charged in the capacitor Cp and the inherent offset value in the analog circuit is charged to the capacitor Csig provided at the video signal output terminal SIG of the video signal output unit 420 through the data line DL do.

Thereafter, an offset value generated in the analog circuit is removed by a post-processing circuit (not shown) to detect a compensation data signal corresponding only to the current generated in the photodetecting device PD, and is supplied to the first gate line GL1 Corresponding compensation data signals are stored in a memory (not shown).

Thereafter, the second gate line GL2, the third gate line GL3, ... The process of making the N-th gate line GLN constant is repeated, and a display device of not shown displays one frame of x-ray image.

That is, the gate driver 300 sequentially turns on the N gate lines, and collects the video signals corresponding to the gate lines on a line-by-line basis, thereby completing one image data.

In the above-described conventional driving method of the X-ray detector, after the charges in the photodetecting element formed with the image information of the object by the X-ray are all removed after the data is read out, no residual image of the previous image is left in the next X- There is a problem that a charge generated in the photodetecting device by the X-ray is present as charges remaining in a plurality of portions of the photodetecting device, resulting in a ghost in which a residual image of the previous image is left in the next image. It is an object of the present invention to solve the problem.

Therefore, it is an object of the present invention to provide an X-ray detector and a driving method thereof that can suppress a ghost phenomenon caused by residual electrons present in a photodetector.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

The present invention relates to an X-ray detector in which an X-ray detection pixel is defined in a matrix form, and which is provided in the X-ray detection pixel and connected to a first bias terminal to generate a current corresponding to the light amount of the visible light converted from the X- ; A photodetecting capacitor provided in the x-ray detecting pixel, the photodetecting capacitor being charged with a current generated in the photodetecting device; An x-ray detecting switch provided on the x-ray detecting pixel, for turning on and off energization of the photodetecting device and the photodetecting capacitor; And a residual charge removing switch provided on the x-ray detecting pixel for turning on and off the power supply of the photodetecting element and the second bias terminal.

In the above-described X-ray detector, the X-ray detecting switch and the residual charge removing switch are sequentially turned on and off for each frame.

In the above-described X-ray detector, the second bias terminal exhibits a higher level than the first bias terminal.

According to another aspect of the present invention, there is provided a method of driving an X-ray detector having a matrix-shaped x-ray detection pixel having a photodetector capacitor and a photodetecting element connected to a first bias terminal, the method comprising the steps of: (a) Generating a current in the photodetector; (b) charging the photodetector capacitor with a current generated in the photodetector; (c) outputting a video signal from a voltage charged in the photodetector capacitor; And (d) removing residual charge of the photodetecting device through the second bias terminal.

In the driving method of the above-described X-ray detector, in the step (b), the photodetecting element and the photodetecting capacitor are energized by an x-ray detecting switch provided in the x- (C), the photodetecting element and the second bias terminal are energized by a residual charge removing switch provided in the x-ray detecting pixel, so that the photodetecting element Is removed through the second bias terminal.

In the driving method of the above-described X-ray detector, the second bias terminal exhibits a higher level than the first bias terminal.

According to the present invention, it is possible to prevent a ghost phenomenon that a residual image of a previous image is left on a next image due to charges remaining in the photodetector.

1 is a block diagram schematically showing a general X-ray detector.
FIG. 2 is a detailed circuit diagram of one of the plurality of X-ray detecting elements arranged in an M × N matrix in the X-ray detector shown in FIG.
3 is a waveform diagram for explaining a driving method of a conventional X-ray detector.
4 is a block diagram schematically showing an X-ray detector according to an embodiment of the present invention.
FIG. 5 is a detailed circuit diagram of one of the plurality of X-ray detecting elements arranged in an M × N matrix in an X-ray detector according to an embodiment of the present invention.
6 is a waveform diagram for explaining a driving method of an X-ray detector according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to specific embodiments of the present invention. However, since the present invention can be variously modified and applied in various forms within the scope of the claims, It is to be understood that the invention is not limited thereto but includes all changes, equivalents, and alternatives falling within the spirit and scope of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, terms such as 'first', 'second', etc. are used to distinguish one component from another, but it is used merely to distinguish between components, Are not limited.

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and, although the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

Also, in this application, the terms " comprises, " or " having ", or the like, indicate that there is a feature, number, step, operation, component, But does not preclude the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, the present invention will be described in detail with reference to an embodiment of the present invention with reference to FIGS. 4 to 6 attached hereto. Wherein like reference numerals designate like or functionally similar elements.

FIG. 4 is a block diagram schematically illustrating an X-ray detector according to an embodiment of the present invention. FIG. 5 is a block diagram of a plurality of X-ray detectors arranged in an M × N matrix in an X- FIG. 6 is a waveform diagram for explaining a method of driving an X-ray detector according to an embodiment of the present invention.

4 and 5, the X-ray detector 10 according to the present invention includes an X-ray detecting panel 100, a bias driving unit 200, a gate driving unit 300, and a signal processing unit 400, (110).

First, the X-ray detecting panel 100 includes a plurality of M (M is a positive integer, only four are shown for simplicity in the drawing) formed along the first direction D1 from the bias driver 200, N lines (N is a positive integer, in this embodiment, only four are shown for the sake of simplicity in the drawing) formed by intersecting the line BL and the bias line BL along the second direction D2 from the gate driver 300 And M × N x-ray detecting pixels 100 ', each including a photodetecting element PD, a first switch Q1 and a PD capacitor Cp, .

The photodetecting device PD includes a scintillator layer (not shown) for converting an x-ray into visible light, which is composed of a hydrogenated amorphous silicon (a-Si: H) To generate a current corresponding to the amount of visible light incident thereon. At this time, the anode electrode of the photodiode is connected to a bias terminal for generating a photodetection current to which a bias voltage for generating a current corresponding to the light quantity of the incident visible light is applied, and the cathode electrode of the photodiode is connected to the first switch Q1 And a second switch (AT) which is a residual charge removing switch for removing the residual charge.

The other end of the second switch (AT) is electrically connected to a residual charge removing bias terminal to which a residual charge removing bias voltage is applied. At this time, the bias voltage for removing the residual charge may be applied or separately applied to the bias driver 200 described later, and the residual charge removing bias voltage may be higher than the bias voltage applied to the bias terminal for generating the photodetection current Do. That is, after the x-ray image is emitted to the photodetector element PD of the X-ray detection panel 100, the second switch AT is turned on to remove the residual charge remaining in the photodetector element PD. The bias voltage for removing the residual charges is higher than the bias voltage for generating the photodetecting current so that a current flows from the residual charge removing bias terminal to the photodetecting current generating bias terminal and the charge is discharged in the opposite direction. That is, if the bias voltage for removing the residual charge is higher than the bias voltage applied to the bias terminal for generating the photodetection current, the residual charge remaining in the photodetector element PD is removed and the previous image is affected by the next image. This is because the ghost phenomenon is suppressed.

The first switch Q1 may be a low temperature poly-Si (LTPS) TFT. The LTPS TFT has a lower turn-on resistance than the amorphous silicon (a-Si) TFT and has a smaller time required for turn-on, so that a time margin can be obtained. Each of the thin film transistors TFT is electrically connected to one of the gate lines GL and one of the data lines DL. The gate electrode of the thin film transistor TFT is electrically connected to the gate line GL and the source electrode of the thin film transistor TFT is electrically connected to the data line DL.

The PD capacitor Cp charges the current applied from the photodetector element PD when the first switch Q1 is turned on.

Meanwhile, the bias driver 200 is electrically connected to the bias lines BL and applies a driving voltage to the bias lines BL. The bias driver 200 may selectively apply a reverse bias and a forward bias to the photodetector PD.

The gate driver 300 is electrically connected to the gate lines GL to apply gate signals to the gate lines GL.

The signal processing unit 400 includes an optical detection signal output unit 410 and a video signal output unit 420. The signal processing unit 400 is electrically connected to the data lines DL and outputs a video signal and an offset signal The composite value and the offset signal can be separately output. As a result, the photodetection voltage with the offset voltage removed can be generated, and the video signal VOUT can be output in response to the photodetection voltage.

Hereinafter, a driving method of the X-ray detecting apparatus according to an embodiment of the present invention will be described with reference to FIG.

6, the X-rays emitted from the X-ray generator (not shown) pass through the subject and are incident on the X-ray detector 10. At this time, the X-ray passes through a scintillator layer (not shown) and is converted into visible light, and the converted visible light passes through the X-ray detecting pixel 100 'arranged in a matrix on the X-ray detecting panel 100 of the X- ) Of the photodetector element PD.

The second reset signal RST is turned off while the M reset switches Q2 arranged in the first gate line GL1 are all kept turned on and the gate driver 300 is turned off, When the gate signal Vgate is applied to the line GL1, the M first switches Q1 whose gate terminals are connected to the first gate line GL1 are turned on so that the currents Is charged into the PD capacitor Cp. That is, the photodetector PD generates a current corresponding to the amount of visible light, and the PD capacitor Cp is charged to a high voltage according to the amount of the generated current.

Thereafter, the second gate line GL2, the third gate line GL3, ... The above process is repeated until the N-th gate line GLN, and a display unit of not shown displays one frame of x-ray image.

Then, a driving signal is applied to the gate terminal of the second switch AT provided in the entire M x N x-ray detecting pixels 100 '. At this time, the driving signal may be applied by the gate driver 300 or may be separately applied (e.g., from a separate controller). Therefore, the second switch AT is turned on, and the residual charge removing bias terminal V and the photodetector element PD are electrically connected. At this time, a voltage higher than the bias voltage for generating the photodetection current, which is electrically connected to the anode electrode of the photodetector element PD, is applied to the residual charge removing bias terminal V. As a result, a current flows from the residual charge removing bias terminal V toward the photodetector element PD. That is, the charge remaining in the photodetector element PD is discharged through the residual charge removing bias terminal (V).

Therefore, since no residual charge remains in the photodetecting device PD, a ghost phenomenon in which a previous image remains in an image generated next time does not occur.

Thereafter, during the period in which the next integration signal is turned on, the X-rays emitted from the X-ray generator (not shown) pass through the subject and are incident on the X-ray detector 10, and the above-described process is repeated.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Various permutations, modifications and variations are possible without departing from the spirit of the invention.

Therefore, the scope of the present invention should not be construed as being limited to the embodiments described, but should be determined by the scope of the appended claims, as well as the appended claims.

10: X-ray detector 100: X-ray detecting panel
100 ': X-ray detection pixel 200: Bias driver
300: Gate driver 400: Signal processor
410: optical detection signal output section 420: video signal output section
PD: photodetecting device Cp: PD capacitor
Q2: Reset switch OP: OP amp
RST: Reset output stage SIG: Video signal output stage
Csig: Capacitor Crst: Capacitor
BL: bias line GL, GL1 to GL4: gate line
DL: Data line 110: Residual charge removal Q1: First switch (X-ray detection switch)
AT: Second switch (residual charge removal switch)

Claims

An x-ray detector in which x-ray detection pixels are defined in a matrix form,
A photodetector element provided in the x-ray detection pixel and connected to the first bias terminal to generate a current corresponding to a light amount of the visible light converted from the x-ray;
A photodetecting capacitor provided in the x-ray detecting pixel, the photodetecting capacitor being charged with a current generated in the photodetecting device;
An x-ray detecting switch provided on the x-ray detecting pixel, for turning on and off energization of the photodetecting device and the photodetecting capacitor; And
A residual charge removing switch provided on the x-ray detecting pixel for turning on and off the power supply of the photodetecting element and the second bias terminal,
Ray detector.

The method according to claim 1,
And the X-ray detecting switch and the residual charge removing switch are sequentially turned on and off for each frame.

The method according to claim 1,
And the second bias terminal indicates a voltage higher than the first bias terminal.

A method of driving an X-ray detector in which a matrix-shaped x-ray detection pixel is defined, which includes a photodetector capacitor and a photodetecting element connected to a first bias terminal,
(a) generating a current in the photodetector by visible light converted from an x-ray;
(b) charging the photodetector capacitor with a current generated in the photodetector;
(c) outputting a video signal from a voltage charged in the photodetector capacitor; And
(d) the residual charge of the photodetecting device is removed through the second bias terminal
Ray detector.

5. The method of claim 4,
In the step (b), the photodetecting element and the photodetecting capacitor are energized by an x-ray detecting switch provided in the x-ray detecting pixel, the current generated in the photodetecting element is charged in the photodetecting capacitor,
In the step (c), the photodetecting element and the second bias terminal are energized by a residual charge removing switch provided in the x-ray detecting pixel so that the residual charge of the photodetecting element is removed through the second bias terminal Ray detector.

5. The method of claim 4,
And the second bias terminal indicates a voltage of a higher level than the first bias terminal.