KR102124629B1 - X-ray detector with liquid crystal and driving method of the same - Google Patents

Abstract

The present invention relates to a liquid-crystal X-ray detector and a driving method thereof. According to the present invention, the liquid-crystal X-ray detector comprises a photographing unit, a read beam output unit, and an X-ray sensing liquid crystal panel including a photoconductive layer made of amorphous selenium. A ground voltage is applied to the X-ray sensing liquid crystal panel at least while the read beam is turned on. According to the present invention, the liquid-crystal X-ray detector turns on the read beam while the ground voltage is applied to the X-ray sensing liquid crystal panel to prevent electrons and holes created in amorphous selenium by emission of the read beam from affecting transmittance.

Description

Liquid crystal X-ray detector and its driving method{X-RAY DETECTOR WITH LIQUID CRYSTAL AND DRIVING METHOD OF THE SAME}

The present invention relates to a liquid crystal X-ray detector and a driving method thereof, and more specifically, a liquid crystal capable of removing errors due to the bias voltage and the measured voltage applied in the previous step even when the bias voltage and the measured voltage are continuously applied. It relates to an X-ray detector and a driving method thereof.

In general, the X-ray imaging apparatus is a device that converts the electric charge distribution of the X-ray absorbing layer that has passed through the subject into a digital signal and images the inside of the subject, and is widely used in medical fields for patient diagnosis or non-destructive inspection of buildings.

Recently, X-ray detectors are trying to improve the technology by introducing digital technology or by introducing liquid crystal elements. As a typical example, there is an X-ray detector incorporating a liquid crystal device, which is commonly referred to as a liquid crystal X-ray detector or an X-ray sensing liquid crystal detector. The liquid crystal X-ray detector is largely composed of a photoconductive element, a liquid crystal element, a light source, and a photodetector.

The liquid crystal X-ray detector radiates X-rays to the photoconductive layer, and when voltage is applied to both electrodes, the X-rays passing through the subject pass through the photoconductive layer and cause polarization in the photoconductive layer. Then, this polarization phenomenon changes the arrangement state of the liquid crystal by affecting the liquid crystal layer. Then, the lead beam from the light source passes through the liquid crystal layer and is formed by the imaging lens, so that an X-ray image of the subject can be captured.

The liquid crystal X-ray detector uses a photoconductive layer composed of amorphous selenium. According to the inventors of the present application, measurement errors caused by a lead beam occur when measuring the transmittance of a pixel according to X-rays after measuring a reference transmittance or applying a measurement voltage. Came to know.

Patent Document 1: U.S. Registered Patent No. 7,687,792 (registered on March 30, 2010)

The present invention is intended to solve the above problems, when measuring the transmittance of a pixel according to the X-ray after measuring the reference transmittance or applying a measurement voltage, the error caused by electrons and holes generated by the lead beam It is an object of the present invention to provide a liquid crystal X-ray detector and a method for driving the same.

The object of the present invention is an X-ray sensing liquid crystal panel including a photoconductive layer made of amorphous selenium, a liquid crystal X-ray detector including a lead beam output unit and an imaging unit, wherein the X-ray sensing liquid crystal for at least some period of turning on the lead beam It can be achieved by a liquid crystal X-ray detector characterized in that the ground voltage is applied to the panel.

It is preferable to apply a ground voltage to the X-ray sensing liquid crystal panel for a period of τ1 including a period for turning on the lead beam. Even after the lead beam is switched from the on state to the off state, it is preferable to further maintain the X-ray sensing liquid crystal panel as a ground voltage for a period of τ2. The τ2 section is preferably 0.5 ms or more, and the τ2 section is more preferably 1.0 ms or more.

Another object of the present invention is an X-ray sensing liquid crystal panel including a photoconductive layer made of amorphous selenium, a bias applied to the X-ray sensing liquid crystal panel without applying X-rays in a liquid crystal X-ray detector including a lead beam output unit and an imaging unit. A method of driving a liquid crystal X-ray detector for measuring a reference transmittance according to a voltage, the method comprising: a first step of applying a first bias voltage consisting of a square wave of + polarity having a first magnitude to an X-ray sensing liquid crystal panel; and the X-ray during a τ1 period The second step of applying the ground voltage (0V) to the sensing liquid crystal panel, and the third step of turning the lead beam on and off for at least a portion of τ1 section of the second step, and the X-ray sensing liquid crystal panel- And a fourth step of applying a square wave of polarity and a fifth step of applying a second bias voltage made of a square wave of + polarity having a second size (second size> first size) to the X-ray sensing liquid crystal panel. It can be achieved by a liquid crystal X-ray detector driving method.

In this case, it is preferable that the τ1 section of the second step includes a τ2 (τ1> τ2) section for applying the ground voltage even after the lead beam is switched from the on state to the off state.

Another object of the present invention is an X-ray sensing liquid crystal panel including a photoconductive layer made of amorphous selenium, a liquid crystal X-ray detector including a lead beam output unit and an imaging unit, and measuring transmittance of an imaging unit pixel according to X-rays through a subject A method of driving a liquid crystal X-ray detector, comprising: a first step of applying a first measurement voltage made of a square wave of + polarity to the X-ray sensing liquid crystal panel; and applying a ground voltage (0V) to the X-ray sensing liquid crystal panel during the τ1 period. The third step of turning on and off the lead beam for a certain period of time between step 2 and at least a portion of the τ1 section of the second step, and a fourth step of applying a second measurement voltage made of a square wave of + polarity to the X-ray sensing liquid crystal panel. It is also possible to achieve by a liquid crystal X-ray detector driving method characterized in that it comprises a step.

In this case, it is preferable that the τ1 section of the second step includes a τ2 (τ1> τ2) section for applying the ground voltage even after the lead beam is switched from the on state to the off state.

The liquid crystal X-ray detector according to the present invention prevents electrons and holes generated in amorphous selenium from being irradiated by lead beam irradiation from affecting transmittance by turning on the lead beam in a state in which a ground voltage is applied to the X-ray sensing liquid crystal panel. In addition, by keeping the X-ray-sensing liquid crystal panel in a ground state for a certain period of time even after the completion of the lead beam irradiation, the electrons and holes generated by the lead beam are not polarized by the bias voltage or the measurement voltage applied in the next step. It can be erased.

In addition, according to the method for driving a liquid crystal X-ray detector according to the present invention, electrons and holes generated in amorphous selenium by lead beam irradiation do not affect transmittance by turning on a lead beam in a state in which a ground voltage is applied to the X-ray sensing liquid crystal panel. Not allowed. In addition, by keeping the X-ray-sensing liquid crystal panel in a ground state for a certain period of time even after the completion of the lead beam irradiation, the electrons and holes generated by the lead beam are not polarized by the bias voltage or the measurement voltage applied in the next step. It can be erased.

By the liquid crystal X-ray detector according to the present invention and a driving method thereof, it is possible to increase the measurement accuracy of the transmittance of the liquid crystal X-ray detector.

1 is an overall configuration diagram of a liquid crystal X-ray detector according to the present invention.
Figure 2 is a cross-sectional view of the X-ray sensing liquid crystal panel according to the present invention.
3 is a flowchart of a method for determining an X-ray image of the liquid crystal X-ray detector shown in FIGS. 1 and 2.
4 is a timing diagram of ON/OFF of a bias voltage, an imaging unit, and a lead beam applied to the first transparent conductive film and the second transparent conductive film through the driving units of the liquid crystal X-ray detectors shown in FIGS. 1 and 2 in the reference transmittance measurement step.
5 is a reference transmittance graph measuring the case where + polarity is applied as a bias voltage and-polarity is applied to the liquid crystal X-ray detector shown in FIGS. 1 and 2, similarly to the waveform and timing shown in FIG. 4.
6 is a timing diagram of ON/OFF of a bias voltage, an imaging unit, and a lead beam applied to the first transparent conductive film and the second transparent conductive film from the driving unit in the reference transmittance measurement step in the liquid crystal X-ray detector according to the present invention.
7 is a timing diagram of ON/OFF of a bias voltage, an imaging unit, and a lead beam applied to a first transparent conductive film and a second transparent conductive film from a driving unit in a reference transmittance measurement step in a liquid crystal X-ray detector according to the present invention.
FIG. 8 is a graph of reference transmittance measured at bias voltages of + polarity and − polarity while turning on a lead beam while maintaining a bias voltage as a ground voltage as illustrated in FIG. 6.
9 is a timing diagram of a measurement voltage waveform and an imaging device and a lead beam including an error in transmittance measured by electrons and holes generated by the lead beam.
10 is a timing diagram of a measurement voltage waveform and an imaging device and a lead beam that are not affected by electrons and holes generated by the lead beam.

The terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms “include” or “have” are intended to indicate that a feature, number, step, action, component, part, or combination thereof, described on the specification exists, and that one or more other features are present. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

In addition, in the present specification, “to or above” means to be positioned above or below the target part, which does not necessarily mean to be located above the gravity direction. That is, the term "on or above" referred to in this specification includes not only the case where the object part is located above or below, but also when it is located before or after the object part.

Also, when a portion of an area, plate, or the like is said to be "on or above" another portion, it is not only when the other portion is in contact or spaced "on or above" another portion, but also another portion in the middle. Also included.

In addition, in this specification, when one component is referred to as "connected" or "connected" with another component, the one component may be directly connected to the other component, or may be directly connected, but in particular It should be understood that, as long as there is no objection to the contrary, it may or may be connected via another component in the middle.

Also, in this specification, terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components.

Hereinafter, preferred embodiments, advantages, and features of the present invention will be described in detail with reference to the accompanying drawings.

1 is an overall configuration diagram of a liquid crystal X-ray detector according to the present invention, and FIG. 2 is a cross-sectional view of the X-ray sensing liquid crystal panel according to the present invention.

1 and 2, the liquid crystal X-ray detector according to the present invention includes an X-ray output unit 50, an X-ray sensing liquid crystal panel 100, a lead beam output unit 60, a driving unit 70, and a polarizing plate 30. It includes an inspection plate 40, an imaging lens 80, and an imaging unit 85.

The X-ray output unit 50 is a device that generates X-rays and outputs them to the outside, and the X-rays output therefrom pass through the subject 90 and then in the photoconductive layer 17 of the X-ray sensing liquid crystal panel 100 Absorbed.

The X-ray sensing liquid crystal panel 100 has a structure in which the photoconductive part 10 and the liquid crystal part 20 are bonded.

The photoconductive part 10 is a configuration in which the distribution of electrons and holes changes when X-ray irradiation and an electric field are applied, and in detail, the substrate 11, the transparent conductive film 13, the insulating film 15, the photoconductive layer 17 and the alignment film (19).

The substrate of the photoconductive part 10 (hereinafter referred to as'first substrate 11') is a substrate for forming the transparent conductive film 13, the insulating film 15, the photoconductive layer 17 and the alignment film 19 , It may be formed of a transparent glass material or a resin material.

The transparent conductive film (hereinafter referred to as'first transparent conductive film 13') of the photoconductive part 10 is a configuration for applying a voltage to the side of the photoconductive part 10, on the one side of the first substrate 11 It is formed on and is electrically connected to the driving unit 70 to be described later.

When a voltage is applied to the transparent conductive film of the photoconductive part 10 and the transparent conductive film of the liquid crystal part 20 by the driving part 70 to be described later, an electric field is formed between them, whereby electrons and holes in the photoconductive layer 17 are formed. The movement of electrons, that is, the electron-hole distribution change occurs.

The insulating film 15 of the photoconductive part 10 is interposed between the first transparent conductive film 13 and the photoconductive layer 17 to prevent charge transfer between the first transparent conductive film 13 and the photoconductive layer 17. It is a composition.

The photoconductive layer 17 of the photoconductive part 10 is a structure for making electric charges. When X-rays are irradiated to the photoconductive layer 17, a large number of electrons-holes are formed inside the photoconductive layer 17. A pair is created and exposing it to an electric field causes the movement of electrons and holes, that is, changes in charge distribution.

The photoconductive layer 17 may be formed on the insulating film 15 in a thin film form, and its material may be made of selenium. The photoconductive layer 17 is particularly preferably made of amorphous selenium (a-Se), which can be coated by vacuum deposition or coating at low temperature.

The alignment film (hereinafter referred to as'first alignment film 19') of the photoconductive part 10 corresponds to a configuration for uniformly aligning liquid crystal molecules together with the alignment film 25 of the liquid crystal part 20.

The liquid crystal unit 20 is provided in a structure bonded to the photoconductor unit 10 to function to change the polarization transmission characteristics of the read beam. The liquid crystal part 20 includes a substrate 21, a transparent conductive film 23, an alignment film 25 and a liquid crystal layer 27.

The substrate of the liquid crystal unit 20 (hereinafter referred to as'second substrate 21') is a base material for forming the transparent conductive film 23, the alignment film 25 and the liquid crystal layer 27, a transparent glass material or a polymer It may be formed of a material.

The transparent conductive film (hereinafter referred to as'second transparent conductive film 23') of the liquid crystal part 20 is a configuration for applying a voltage to the photoconductive part 10 side, on one surface of the second substrate 21 It is formed and is electrically connected to the driving unit 70 to be described later.

When a voltage is applied to the first and second transparent conductive films 13 and 23 by the driving unit 70, an electric field is formed between them, whereby the movement of electrons and holes in the photoconductive layer 17, that is, electron-hole distribution changes Is generated.

The liquid crystal layer 27 of the liquid crystal unit 20 changes polarization transmission characteristics of a read beam by changing the liquid crystal arrangement in conjunction with this when the charge distribution of the photoconductor unit 10 changes according to X-ray irradiation and voltage application. As a configuration that acts to change, it includes a plurality of liquid crystal molecules injected into the first alignment layer 19 and the second alignment layer 25.

The alignment layer (hereinafter referred to as'second alignment layer 25') of the liquid crystal unit 20 is formed on the second transparent conductive layer 23, and when the liquid crystal unit 20 is bonded to the photoconductive unit 10, the first It is provided with a structure facing the alignment layer 19, and functions to uniformly align the liquid crystal molecules together with the first alignment layer 19.

The lead beam output unit 60 is a device that emits the lead beam 61 traveling toward the liquid crystal unit 20, and may be configured of, for example, an LED (LED) element that outputs light in a visible wavelength band.

On the other hand, when the photoconductive layer 17 is formed of amorphous selenium, the lead beam 61 must transmit amorphous selenium, and polarization characteristics of the polarizing plate and the spectroscopic plate must be maintained. Therefore, the lead beam 61 should be light in a wavelength range of 680 to 900 nm, preferably light in a wavelength range of 700 to 800 nm, and more preferably, a 780 nm LED (Light Emit Diode).

Half-transmission mirror (Half Mirror, 65) is disposed on the optical path in front of the lead beam output unit 60, the lead beam 61 emitted from the lead beam output unit 60 is reflected toward the X-ray sensing liquid crystal panel 100 The X-ray output from the X-ray output unit 50 is an optical element that passes through and passes straight.

The driving unit 70 is configured to separate electrons and holes by applying a predetermined bias voltage Vb to the first and second transparent conductive films 13 and 23.

The polarizing plate 30 is disposed on the optical path between the photoconductor portion 10 and the lead beam exit portion 60, and the detection plate 40 is disposed on the optical path in front of the liquid crystal portion 20 to form a liquid crystal layer ( 27) Blocks or transmits the lead beam according to the change in polarization transmission characteristics. In the present invention, the polarization directions of the polarizing plate 30 and the spectroscopic plate 40 are designed to be different from each other, and preferably, are designed to be orthogonal to each other.

The imaging lens 80 is disposed on an optical path in front of the inspection plate 40 to form a lead beam transmitted through the inspection plate 40 to function to form an image on the imaging unit 85.

The imaging unit 85 is a device that detects the lead beam 61 formed by the imaging lens 80 and analyzes its characteristics to diagnose the state of the subject. The imaging unit 85 may be, for example, a CCD camera or a CMOS camera.

The control unit 110 generates control signals for controlling the imaging unit 85, the driving unit 70, and the lead beam output unit 60.

The operation principle of the liquid crystal X-ray detector is as follows. The liquid crystal X-ray detector of the present invention is configured as a structure in which the photoconductive part 10 and the liquid crystal part 20 come into contact with each other as shown in FIGS. 1 and 2. When X-rays are applied to the photoconductive part 10, electrons and holes are made inside the photoconductive layer 17. In such a state, when an electric field is applied between the first transparent conductive film 13 and the second transparent conductive film 23, a polarization phenomenon in which electrons and holes move to the opposite side of the transparent conductive film occurs.

Such a polarization phenomenon changes the state of the liquid crystal by affecting the liquid crystal layer 27. That is, when the charge distribution changes as shown in FIG. 2, the liquid crystal arrangement in the liquid crystal layer 27 is changed.

More specifically, in the region of the photoconductive layer 17 irradiated with X-rays, electrons and holes are separated to shield the electric field inside the photoconductive layer 17, and in response, a voltage applied to the liquid crystal layer 27 is increased. do.

In the case of FIG. 2, the case where the region (A) through which the X-rays are not transmitted and the region (B) through which the X-rays 5 are transmitted are generated by the subject 90 will be described. In the (B) region, polarization occurs in the photoconductive layer 17 by X-rays 5, and + charges (holes) are accumulated in the region close to the alignment layer 19. The liquid crystal of the liquid crystal layer 27 is vertically rearranged according to the electric field direction by the electric field due to the voltage difference applied to the second transparent conductive film 23 of the liquid crystal unit 20 and the voltage due to the holes. Therefore, the lead beam incident on the (B) region transmits the liquid crystal layer 27 as it is, and maintains a state in which the polarization direction remains unchanged, and is thus blocked by the inspection plate 40.

On the other hand, in the region (A), since polarization does not occur in the photoconductor layer, an electric field sufficient to rearrange the liquid crystal of the liquid crystal layer 27 is not formed, thereby maintaining the initial alignment state, and the leads transmitted to the region (A) As the beam passes through the liquid crystal layer 20, the polarization direction is changed, and the light is transmitted through the inspection plate 61.

By changing the polarization transmission characteristics of the liquid crystal layer 27 differently depending on whether X-rays are transmitted by the subject 90 or not, the lead beam reaching the inspection plate 40 through the polarizing plate 30 is only light that matches the polarization direction. It is transmitted and selectively enters the imaging lens 80. The imaging unit 85 detects the light formed by the imaging lens 80, so that an X-ray image of the subject can be obtained.

3 is a flowchart of a method for determining an X-ray image of the liquid crystal X-ray detector shown in FIGS. 1 and 2. 3, the X-ray image determination method of the liquid crystal X-ray detector according to the present invention includes a lead beam output step (S10), a reference transmittance measurement step (S20), an electron-hole separation step (S30), and a detection transmittance measurement step (S40). ), a bias voltage deriving step (S50), a correction value calculating step (S60), an X-ray image determination step (S70), and a charge erasing step (S80).

The lead beam output step S10 is a step of inputting power to the liquid crystal X-ray detector (S10a) and driving the lead beam output unit 60 to emit the lead beam. Preferably, the lead beam output step (S10) is configured to wait until the intensity of the lead beam is stabilized (S10b), and then perform a reference transmittance measurement step when the output of the lead beam light source is stable.

The reference transmittance measurement step (S20) changes the bias voltage (Vb) applied to the X-ray sensing liquid crystal panel 100 while X-rays are not irradiated to the X-ray sensing liquid crystal panel, and the transmittance of the pixel [T(x,y, V(i))]. Here, the'bias voltage Vb' is applied to the first and second transparent conductive films 13 and 23 of the X-ray sensing liquid crystal panel 100 by the driving unit 70. 'Pixel' refers to the pixel of the imaging unit 85 camera, and'pixel' transmittance refers to the transmittance of the lead beam with respect to the liquid crystal viewing angle corresponding to the pixel. In the transmittance [T(x,y,V(i))] of step S20,'x,y' means the pixel coordinates of the imaging unit 85, and'V(i)' changes the bias voltage Vb. It means measuring multiple times on the way.

Hereinafter, the transmittance of the pixel measured according to step S20 will be referred to as'reference transmittance [T(x,y,V(i))]'.

The electron-hole separation step (S30) is a step of separating electrons and holes from the photoconductor by applying a separation voltage Vs to the X-ray sensing liquid crystal panel (S30a) and irradiating X-rays (S30b).

When X-rays are applied to the photoconductive part 10, electrons and holes are made inside the photoconductive layer 17. In this state, when a DC electric field is applied between the first transparent conductive film 13 and the second transparent conductive film 23, a polarization phenomenon in which electrons and electrons move toward the transparent conductive films of opposite polarities occurs, respectively. Referring to FIG. 2, since the (+) voltage is applied to the first transparent conductive film 13, holes are distributed in the lower region (ie, the adjacent region of the liquid crystal layer 27) inside the photoconductive layer 17. , The electrons are distributed in the upper region inside the photoconductive layer 17 (ie, the region adjacent to the first transparent conductive film 13 ).

The detection transmittance measurement step (S40) measures the transmittance [T(x,y,i)] of the pixels of the imaging unit 85 by applying a measurement voltage (Vm) to the X-ray sensing liquid crystal panel 100 (S40b). It is a step. In the transmittance [T(x,y,i)] of step S40,'x,y' denotes pixel coordinates of the imaging unit 85, and'i' denotes a corresponding pixel while the liquid crystal layer 27 maintains a voltage. It means to measure the transmittance of multiple times.

The measurement voltage Vm applied in the detection transmittance measurement step S40 may be configured to measure the detection transmittance while maintaining the same voltage constant, or may be configured to measure the detection transmittance while changing the measurement voltage to two or more voltage values. .

The bias voltage derivation step S50 finds a reference transmittance value having the same value as the detected transmittance [T(x,y,i)] in step S40, from which the bias voltage corresponding to the reference transmittance [V(x,y) ,i)].

The correction value calculation step S60 is a step of performing an operation of subtracting the measured voltage Vm applied in step S40 from the bias voltage [V(x,y,i)] derived in step S50.

The X-ray image determination step S70 is a step of determining an X-ray image based on the value calculated in step S60. That is, when the X-ray image of the pixel is determined (that is, the X-ray intensity is determined) using the value obtained by subtracting the measurement voltage of Step S40 from the bias voltage of Step S50, the transmittance caused by a difference in viewing angle of the liquid crystal corresponding to the corresponding pixel Distortion can be corrected.

Then, when the above-described steps S20 to S70 are applied to all the pixels of the imaging unit 85, X-ray images of all the pixels (that is, the entire diagnostic area of the subject) can be determined, and output accordingly. The X-ray image can provide an image in which distortion of a lead beam intensity for each pixel, which was generated during X-ray image shooting using a conventional liquid crystal, is removed.

The charge erasing step (S80) is a step of removing the charge accumulated in the photoconductive layer 17. According to one embodiment, the charge erasing step (S80) is a separated electron of the photoconductive layer 17 by irradiating UV to the photoconductive layer 17 in a state in which the bias voltage is grounded to 0 V or a square wave of less than 5 Hz is applied. And holes can be configured to recombine.

When the charge erasing step S80 is completed, it is possible to perform X-ray imaging of the subject again by repeating steps S10 to S80.

4 is a timing diagram of on/off of a bias voltage, an imaging unit, and a lead beam applied to the first transparent conductive film and the second transparent conductive film through the driving units of the liquid crystal X-ray detectors shown in FIGS. 1 and 2 in the reference transmittance measurement step. Specifically, Figure 4 (a) shows a bias voltage waveform diagram, it can be seen that the bias voltage is made of a square wave that increases with time. 4(b) is an on/off timing diagram of the imaging unit and the lead beam. According to FIG. 4, before the polarity of the bias voltage changes, the imaging unit and the lead beam are turned on and off. τ3 represents the time for the imaging unit and the lead beam to remain on. However, according to the experiment of the present inventor, when the lead beam is turned on for a period of τ3 while a bias voltage of + polarity is applied as shown in FIG. 4, the transmittance measured by electrons and holes generated by the lead beam is affected. It was found that the distorted transmittance was measured.

5 is a reference transmittance graph measuring the case where + polarity is applied as a bias voltage and-polarity is applied to the liquid crystal X-ray detector shown in FIGS. 1 and 2, similarly to the waveform and timing shown in FIG. 4. The solid line is measured when the bias voltage is + polarity, and the broken line is a graph measured when the bias voltage is applied as-polarity. It can be seen that as the bias voltage increases, a difference in relative transmittance measured at both polarities occurs. According to the inventors of the present application, it is assumed that the lead beam is irradiated to the amorphous selenium layer, electrons and holes are generated, and the electric charges caused by this are moved to the transparent conductive film by the bias voltage, causing some polarization inside the amorphous selenium layer. do. Since charges and holes generated in the amorphous selenium layer are continuously accumulated without being erased by the lead beam, it is seen that as the bias voltage increases, the relative transmittance according to + polarity and -polarity gradually increases. That is, in the case of an ideal amorphous selenium layer (photoconductive layer), electrons and holes are separated only by excitation of X-rays, and electrons and holes should be maintained without separation by a lead beam having energy lower than X-rays. However, according to the experiment of the inventors of the present application, as shown in FIG. 5, in the case of the actual amorphous selenium layer (photoconductive layer), the electrons and holes are separated even by the lead beam to grasp that charge is generated, and thus generated by the lead beam It was found that image distortion was caused by the electric charge.

In the present invention, in order to eliminate image distortion caused by electrons and holes generated by the lead beam, the measurement of transmittance is improved by preventing electrons and holes from being generated while the lead beam is irradiated in the reference transmittance measurement step and the detection transmittance measurement step. The purpose. In order to achieve this object, the present invention proposes a liquid crystal X-ray detector and a driving method for driving a lead beam to emit light only when a bias voltage is applied as a ground voltage (0V). In addition, even if electrons and holes are generated by the lead beam, the generated electrons and holes are extinguished by maintaining the bias voltage for a certain period of time after the lead beam is turned off, thereby affecting the next reference transmittance measurement or measurement voltage application step. It was constructed so as not to go crazy.

6 is a timing diagram of ON/OFF of a bias voltage applied to a first transparent conductive film and a second transparent conductive film from a driving unit, an imaging unit, and a lead beam in a step of measuring a reference transmittance in a liquid crystal X-ray detector according to the present invention. In FIG. 6, (a) shows a bias voltage waveform, and (b) shows an on/off timing diagram of a lead beam and an imaging device. The liquid crystal X-ray detector according to the present invention has the same configuration as the liquid crystal X-ray detector shown in FIGS. 1 and 2 except that the shape of the bias voltage waveform applied to the driving unit and the shape of the measurement voltage waveform, and the timing for controlling the driving unit and the imaging unit are changed. .

The bias voltage waveform was maintained to be grounded for a period of τ1 whenever switching from +polar to -polar. The lead beam on time (τ1-τ2) is formed to have a section shorter than the τ1 section within the τ1 section. As shown in FIG. 6, when the lead beam is turned on to coincide with the timing at which the bias voltage falls to the ground voltage, the τ2 section is defined as a section for dissipating electrons and holes generated by the lead beam.

If no energy is injected from the outside, the electrons generated in the amorphous selenium disappear after 0.1 to 1.0 ms, and the holes are thought to disappear after 0.1 to 0.5 ms. If the period during which the lead beam is irradiated (τ1-τ2) in the reference transmittance measurement step is 0.5 ms to 1 ms, if the lead beam is designed to maintain the bias voltage at ground for about 0.5 to 1.0 ms after completing the irradiation, the lead beam The influence of the charge generated by can be eliminated. That is, assuming that the period (τ1-τ2) in which the lead beam is irradiated is 0.5 ms to 1 ms, τ 1 may be maintained at 1 ms to 2 ms. More practically, assuming that the period (τ1-τ2) at which the lead beam is irradiated is 0.5 ms, the period of τ1 is maintained at 1.5 ms. When using an LED (Light Emit Diode) as a lead beam, the on/off response time of the LED is 100 ms (0.1 ms), so it is negligible.

7 is a timing diagram of on/off timing of a bias voltage, an imaging unit, and a lead beam applied to the first transparent conductive film and the second transparent conductive film from the driving unit in the reference transmittance measurement step in the liquid crystal X-ray detector according to the present invention. It is different from FIG. 6 in that some sections τ4 to which a bias voltage of + polarity is applied and sections to which a lead beam is turned on coexist and the rest of the configuration is the same. When the lead beam is turned on/off at the timing shown in FIG. 7(b), there is a possibility that some error may occur in the reference transmittance measurement by electrons and holes generated by the lead beam. However, by providing sufficient time (τ2) for the electrons and holes generated by the lead beam irradiated in the previous step to disappear, the cumulative error due to electrons and holes generated by the lead beam can be eliminated.

FIG. 8 is a graph of reference transmittance measured at bias voltages of + polarity and − polarity while turning on the lead beam while maintaining the bias voltage as the ground voltage as illustrated in FIG. 6. The solid line is measured when the bias voltage is + polarity, and the broken line is a graph measured when the bias voltage is applied as-polarity. It can be seen that the measured values of the two coincide, and it can be seen that electrons and holes generated by the lead beam no longer affect the reference transmittance.

Next, a method of applying a measurement voltage in the detection transmittance measurement step will be described.

9 is a timing diagram of a measurement voltage waveform including an error in transmittance measured by electrons and holes generated by a lead beam, and an imaging device and a lead beam. FIG. 9(a) simply shows voltage waveforms applied to the first transparent conductive film and the second transparent conductive film through the driving unit in the sections T1, T2, T3, and T4, and FIG. 9(b) shows the imaging device and the lead beam. It is a timing diagram. The T1 section represents a preparation step before the electron-hole separation step, the T2 section is a step of separating electrons and holes by applying a Vs voltage, the T3 section represents a detection transmittance measurement step, and the T4 step represents a charge erasing step. . In FIG. 9, the same measurement voltage (Vm) is applied to the first transparent conductive film and the second transparent conductive film by using the driving unit in the T3 section, but it is needless to say that two or more different voltages can be used as the measurement voltage. When the lead beam is turned on while applying a constant measurement voltage (Vm) in the detection transmittance measurement step (T3) as shown in FIG. 9 to the liquid crystal X-ray detector shown in FIGS. 1 and 2, it is generated by the lead beam as described above. An error occurs in the transmittance measured by the electrons and holes.

10 is a timing diagram of a measurement voltage waveform and an imaging device and a lead beam that are not affected by electrons and holes generated by the lead beam. FIG. 10(a) is a simple diagram showing voltage waveforms applied to the first transparent conductive film and the second transparent conductive film through the driver in the sections T1, T2, T3, and T4, and FIG. 10(b) is an image pickup device and a lead beam. It is a timing diagram. The division of the T1, T2, T3, and T4 sections is the same as in FIG. 9. In FIG. 10, one measurement voltage Vm is applied to the first transparent conductive film and the second transparent conductive film by using a driver in the T3 section, but it is needless to say that two or more different voltages can be used as the measurement voltage. The difference from FIG. 9 is that the method of applying one measurement voltage (Vm) is the same, but after applying the measurement voltage (Vm) as the ground voltage during the period (τ1-τ2) for irradiating the lead beam, after the lead beam finishes irradiation It is designed to maintain the measured voltage (Vm) as the ground voltage during the period of τ2. As described above, assuming that the period (τ1-τ2) in which the lead beam is irradiated in FIG. 10 is 0.5 ms, the period τ1 may be maintained at 1.5 ms.

Although preferred embodiments of the present invention have been described above using specific terms, such terms are only intended to clearly describe the present invention, and embodiments and described terms of the present invention deviate from the technical spirit and scope of the following claims. It is obvious that various changes and changes can be made without being done. Such modified embodiments should not be individually understood from the spirit and scope of the present invention and should be said to fall within the scope of the claims of the present invention.

10: photoconductive part 11: first substrate
13: first transparent conductive film 15: insulating film
17: photoconductive layer 19: first alignment layer
20: liquid crystal unit 21: second substrate
23: second transparent conductive film 25: second alignment film
27: liquid crystal layer 30: polarizing plate
40: inspection plate 50: X-ray output
60: lead beam output unit 61: lead beam
65: transflective mirror 70: driving unit
80: imaging lens 85: imaging unit
90: subject 100: X-ray sensing liquid crystal panel
110: control unit

Claims (9)

In the X-ray sensing liquid crystal panel comprising a photoconductive layer made of amorphous selenium, a liquid crystal X-ray detector including a lead beam output unit and an imaging unit,
A liquid crystal X-ray detector, characterized in that a ground voltage is applied to the X-ray sensing liquid crystal panel for at least some period of turning on the lead beam.
According to claim 1,
A liquid crystal X-ray detector, characterized in that a ground voltage is applied to the X-ray sensing liquid crystal panel for a period of τ1 including a period for turning on the lead beam.
According to claim 2,
A liquid crystal X-ray detector, characterized in that the X-ray sensing liquid crystal panel is further maintained at a ground voltage for a period of τ2 even after the lead beam is switched from an on state to an off state.
According to claim 3,
The τ2 section is a liquid crystal X-ray detector, characterized in that 0.5ms or more.
The method of claim 4,
The τ2 section is 1.0ms or more, characterized in that the liquid crystal X-ray detector.
An X-ray sensing liquid crystal panel including a photoconductive layer made of amorphous selenium, a liquid crystal X-ray detector including a lead beam output unit and an imaging unit, and a reference transmittance according to a bias voltage applied to the X-ray sensing liquid crystal panel without applying X-rays In the liquid crystal X-ray detector driving method for measuring,
A first step of applying a first bias voltage made of a square wave of + polarity having a first magnitude to the X-ray sensing liquid crystal panel;
a second step of applying a ground voltage (0V) to the X-ray sensing liquid crystal panel during a period of τ1;
A third step of turning on and off the lead beam for a predetermined time between at least a portion of the τ1 section of the second step;
A fourth step of applying a square wave of polarity to the X-ray sensing liquid crystal panel; and
And a fifth step of applying a second bias voltage made of a square wave of + polarity having a second magnitude (second magnitude> first magnitude) to the X-ray sensing liquid crystal panel.
The method of claim 6,
The τ1 section of the second step includes a τ2 (τ1> τ2) section for applying a ground voltage even after the lead beam is switched from an on state to an off state.
A method for driving a liquid crystal X-ray detector for measuring the transmittance of an imaging unit pixel according to X-rays through a subject in a liquid crystal X-ray detector including an X-ray sensing liquid crystal panel including a photoconductive layer made of amorphous selenium, a lead beam output unit, and an imaging unit. In,
A first step of applying a first measurement voltage made of a square wave of + polarity to the X-ray sensing liquid crystal panel;
a second step of applying a ground voltage (0V) to the X-ray sensing liquid crystal panel during a period of τ1;
A third step of turning on and off the lead beam for a predetermined period between at least a portion of the τ1 section of the second step; and
And a fourth step of applying a second measurement voltage made of a square wave of + polarity to the X-ray sensing liquid crystal panel.
The method of claim 8,
The τ1 section of the second step includes a τ2 (τ1> τ2) section for applying a ground voltage even after the lead beam is switched from an on state to an off state.

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