CN116106350A

CN116106350A - Imaging method, device and application based on material with continuous photoconductive effect

Info

Publication number: CN116106350A
Application number: CN202111329751.4A
Authority: CN
Inventors: 梁会力; 朱锐; 王燕; 刘尧平; 梅增霞
Original assignee: Songshan Lake Materials Laboratory
Current assignee: Songshan Lake Materials Laboratory
Priority date: 2021-11-11
Filing date: 2021-11-11
Publication date: 2023-05-12

Abstract

An imaging method, equipment and application based on a material with continuous photoconductive effect belong to the field of high-energy radiation detection. The present application proposes a solution for X-ray detection using a material with a sustained photoconductive effect. Since the above-mentioned material has an electric signal generated in the case of being irradiated with X-rays, and still has an electric signal existing due to the persistent photoconductive effect within a certain time range after the X-rays stop being irradiated. Therefore, by collecting the electric signals in the two time periods and processing and imaging the data accordingly, the irradiation dose of the X-rays can be effectively reduced and a relatively more ideal image with higher signal to noise ratio can be obtained.

Description

Imaging method, device and application based on material with continuous photoconductive effect

Technical Field

The present application relates to the field of high energy radiation detection, and in particular to an imaging method, apparatus and application based on materials with persistent photoconductive effect.

Background

An X-ray detector is a device that converts X-rays invisible to the naked eye into an electrical signal and performs detection by processing the signal. The device can accurately detect internal fine structures such as organisms, metals and the like, and has wide application in the fields of medical treatment, scientific research, nuclear industry, precision part processing, aerospace and the like.

The X-ray detector is classified into a gas detector and a semiconductor detector according to the detection medium.

The gas detector has the advantages of simple preparation, low cost, high response speed and the like, but is difficult to integrate in a large area and needs good air tightness. The semiconductor detector has the advantages of high resolution, small volume, easy large-area integration and the like, and therefore has great development potential.

Currently, one of the key materials commonly used in semiconductor detectors is the semiconductor detection material. The semiconductor probe material comprises CdTe, cdZnTe, pbI ₂ 、HgI ₂ Perovskite material, amorphous Se, diamond, siC, gaN, amorphous oxide semiconductor material, and the like.

When the signal-to-noise ratio is not ideal, it is difficult for current semiconductor detectors to obtain an effective detection result.

The information disclosed in this background section is only for enhancement of understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

The application proposes an imaging method, device and application based on a material with a sustained photoconductive effect, which can be used to overcome the problem of not being able to perform high quality detection when the signal-to-noise ratio is not ideal without increasing or not significantly increasing the radiation dose.

The application is realized in such a way that:

in a first aspect, examples of the present application provide for the use of a persistent photoconductive effect of a material having a persistent photoconductive effect to improve the signal to noise ratio of an X-ray detector without increasing the radiation dose.

According to some examples of the present application, a material with a persistent photoconductive effect is fabricated as a sensitive element in an X-ray detector. The sensitive element refers to an electronic component capable of giving measurable data in response to X rays; i.e. it is a sensor that gives feedback on the X-ray exposure.

According to some examples of the present application, a material with a persistent photoconductive effect is fabricated as a photoelectric converter in an X-ray detector.

Optionally, the photoelectric converter is used in a way that increases the signal-to-noise ratio of the X-ray detector without increasing the X-ray radiation dose;

optionally, the material having a persistent photoconductive effect comprises amorphous Ga ₂ O ₃ 。

According to some examples of the present application, a photoelectric converter includes: a substrate; by amorphous Ga ₂ O ₃ An active layer formed on the substrate; an electrode formed on the active layer; wherein the electrodes are conductive glass and the conductive glass is used to increase the speed of the photoelectric converter in response to reverse voltage to eliminate persistent photoconductive. For example, the conductive glass is ITO (indium tin oxide). The improvement may be, for example, compared to the case where no reverse voltage is applied.

Alternatively, the photoelectric converter includes: a substrate; by amorphous Ga ₂ O ₃ An active layer formed on the substrate; an electrode formed on the active layer; wherein the electrode comprises a metal electrode or a conductive glass electrode; alternatively, the electrode is a gold electrode.

In a second aspect, the present examples provide an imaging method.

The imaging method comprises the following steps:

receiving transmitted light generated by irradiating a target object to be imaged with X-rays by using a photoelectric conversion element made of a material having a continuous photoconductive effect;

collecting the electric signal of the photoelectric conversion element during the X-ray irradiation period and in a period of a preset time period after stopping the X-ray irradiation;

the electrical signal is processed to obtain image information corresponding to the target object.

According to some examples of the present application, an imaging method includes: after the electrical signal of the photoelectric conversion element is collected, a reverse voltage is supplied to the photoelectric conversion element.

Alternatively, the reverse voltage is a reverse pulse voltage.

Optionally, the preset duration is determined by determining an acquisition end point for acquiring an electrical signal of the photoelectric conversion element, and the determining method includes: when the current value acquired from the photoelectric conversion element after stopping the X-ray irradiation is equal to the current value acquired from the photoelectric conversion element before the X-ray irradiation.

According to some examples of the present application, a method of processing the electrical signal to obtain image information corresponding to a target object includes:

the electrical signal is time integrated and the integration formula is as follows:

wherein the X-ray ON moment is defined as integral 0 point and the current corresponding to this moment is the background current I before X-rays are not irradiated ₀ The method comprises the steps of carrying out a first treatment on the surface of the The raw current value obtained by acquisition is defined as I ^meas (t); effective response current is I ^meas (t)-I ₀ The method comprises the steps of carrying out a first treatment on the surface of the Time-integrating the effective response current to obtain an output signal S ^output (t)。

Thus, the image information corresponding to the target object is S as described above ^output (t). The output signal is then correlated with gray scale (black to white).

In a third aspect, the present application examples provide an imaging apparatus.

The image forming apparatus includes:

an irradiation source for generating X-rays;

a photoelectric conversion element disposed opposite to the irradiation source for receiving X-rays;

and the electric signal collector is electrically connected with the photoelectric conversion element and is used for collecting electric signals generated by the photoelectric conversion element, wherein the photoelectric conversion element is manufactured based on a material with a continuous photoconductive effect.

According to some examples of the present application, an imaging apparatus includes: and a power supply electrically connected to the photoelectric conversion element for supplying a reverse voltage to the photoelectric conversion element.

Optionally, the power supply provides a periodic bias voltage to the photoelectric conversion element.

Optionally, the electrical signal collector and the power supply are provided by an integrated power meter.

According to some examples of the present application, an imaging apparatus includes: and the irradiation manipulator is connected with the irradiation source in a matching way and is used for controlling the irradiation source.

Optionally, the imaging device comprises an information processor matingly connected to the photoelectric conversion element for processing the electrical signals to generate an image.

According to some examples of the present application, an imaging apparatus includes: and the display is used for displaying images and/or the memory is used for storing images, the display is electrically connected with the information processor, and the memory is electrically connected with the information processor.

According to some examples of the present application, the imaging device includes a remote terminal connected to the controlled device through a wired network or a wireless network to control the controlled device.

In the above implementation, the present embodiments propose to utilize materials with persistent photoconductive effects in an active manner in the imaging field. By using a continuous photoconductive effect, good images are obtained with relatively less irradiation.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic cross-sectional structure of an X-ray photoelectric conversion unit in an example of the present application;

FIG. 2 is a schematic diagram of an X-ray detection imaging apparatus in the practice of the present application;

FIG. 3 is a schematic diagram of an imaging system of an X-ray detection imaging device based on the principles shown in FIG. 2;

FIG. 4 is a graph showing the periodic response of three X-ray photoelectric conversion unit devices in an X-ray detection imaging system of example 1 of the present application at 10V bias, X-ray tube voltages of 40kV, tube currents at 50, 125, and 200 μA, respectively;

FIG. 5 shows the effective response current versus time for cycle 6 of the graph of FIG. 4;

FIG. 6 is a graph of the effective response current versus time integral obtained based on the graph of FIG. 5;

FIG. 7 is a graph showing the effect of self-enhancement over time of an image simulated from the effective response current time integral in FIG. 6;

FIG. 8 is a graph showing the continuous cycle response performance of the X-ray photoelectric conversion element of example 1 of the present application under irradiation of a tube current of 100 and 200. Mu.A at a cycle bias of.+ -.10V at an X-ray tube voltage of 40 kV;

FIG. 9 is a plot of effective response current of an X-ray photoelectric conversion element in an X-ray detection imaging system of example 1 of the present application at cycle 6 and effective response current without persistent photoconductive effect over time in comparative example 1;

FIG. 10 is a plot of the effective response current time integral of the X-ray photoelectric conversion element in the X-ray detection imaging system of example 1 of the present application at cycle 6 and the effective response current time integral of the comparative example 1 without persistent photoconductive effect;

FIG. 11 is a graph showing the image enhancement effect over time according to a comparison curve time integration simulation of the comparative example 1 without the persistent photoconductive effect shown in FIGS. 9 and 10;

FIG. 12 shows the recovery and continuous operation of the X-ray photoelectric conversion element of example 2 of the present application by applying a reverse bias voltage of 10V for a short time under irradiation of an X-ray tube voltage of 40kV and a tube current of 200. Mu.A.

Icon: 11-a quartz substrate; 12-an X-ray detecting active layer; 131-a first top electrode; 132-a second top electrode; 200-a radiation source; 201-emitting X-rays; 202-detected object; 203-transmitting X-rays; 204-X-ray photoelectric conversion unit.

Detailed Description

An X-ray detector is a widely used detection device. Which can be used to image the interior of an object in a non-contact or non-invasive manner in order to detect the fine structure of the interior. As an example of wide use, the X-ray detector may be applied to various CT imaging apparatuses, X-ray flaw detectors, and the like.

In all-solid-state X-ray detectors, one of the key core elements is a semiconductor photoelectric conversion element. Therefore, a high-quality semiconductor photoelectric conversion element plays an important role in the performance of an X-ray detector, the imaging quality.

In the practical use process, when the signal to noise ratio is not ideal enough, the imaging effect of the current X-ray detector is poor. Currently, in order to address the above-described problems, a countermeasure generally adopted in practice is to increase the exposure time (X-ray irradiation time).

Such a solution does in some cases solve the problem of insufficient signal-to-noise ratio. However, in other scenarios, increasing exposure times is often impractical or at other costs. For example, for medical probe imaging, in order to reduce irradiation damage to a human body, it is necessary to reduce the irradiation dose (for example, to reduce the X-ray irradiation time) as much as possible, and thus improvement for numerous X-ray detectors is required.

Through analysis and study of the present situation, the inventors have proposed a solution that can positively contribute to the above-mentioned problems. By analysis, at present, the exposure time is increased with a low signal-to-noise ratio in order to obtain a correspondingly formed signal due to the X-ray irradiation over a longer period of time. Accordingly, the inventors believe that it is possible to obtain an electrical signal long or longer enough for processing the electrical signal to obtain an image without increasing the irradiation time of the X-rays; and the contrast of the image is high, with an acceptable signal to noise ratio.

In other words, the present examples propose the use of a persistent photoconductive effect with a material having a persistent photoconductive effect to improve the signal to noise ratio without increasing the radiation dose of the X-ray detector. That is, in the present application, the persistent photoconductive effect is used in favor of conditions and factors, and thereby improves the performance of the X-ray detector. Wherein the material with the continuous photoconductive effect refers to a material capable of generating the continuous photoconductive effect under specific illumination; the specific illumination in the examples of the present application refers to X-rays.

The imaging scheme has remarkable application value in the fields of medical imaging, tumor treatment, public place safety detection such as airports, subways, wharfs and the like, industrial flaw detection, X-ray photoelectron spectroscopy, X-ray diffractometer equipment and the like.

In view of this recognition, the inventors therefore propose to use a new material as one of the key components in an X-ray detector. In the example used is a material with a persistent photoconductive effect, referred to as photoelectric material, for example amorphous Ga ₂ O ₃ 。

The photovoltaic material generates an electric current upon irradiation of light, and also generates an electric current continuously for a certain period of time after the light is stopped. Thus, based on this characteristic of the photoelectric material, an image can be obtained by using the generated electric signal. In an example, the electro-optical material is an X-ray sensitive material. Thus, it can generate a response current under X-ray irradiation while also being able to continue to maintain a higher current than before irradiation for a period of time after the X-ray irradiation is stopped.

Thus, an image can be obtained by processing the above-described current. The main processing mode is to obtain a charge quantity signal in a period of time by time integration of the current, and construct an image based on the charge quantity signal. In this way, a gray-scale pixel map, i.e. an image of pixels of different gray-scales, can be constructed. Moreover, the application of the detection scheme described in the example of the application to imaging effects can be applied to single device row-by-row scanning imaging, real-time imaging of an area array structure formed by combining a plurality of unit devices, and a non-imaging scene of single-point test.

In an example, the photovoltaic material is used in such a way that: a photoelectric converter, in the example an X-ray photoelectric conversion unit.

In other words, the exemplary aspects of the present application make use of the persistent photoconductive phenomenon of an X-ray photoelectric conversion unit to time integrate a current signal. The memory current after short X-ray pulse irradiation extends over time, thereby spontaneously enhancing the contrast of the image. The scheme can effectively shorten the exposure time and reduce the irradiation dose of X rays, thereby realizing self-enhancement type X-ray detection imaging.

In addition, the current of the device is slowly reduced under the condition of not changing the external bias voltage after the irradiation of the X-ray source is finished, and the state before the irradiation is difficult to quickly recover. Therefore, further, the continuous photocurrent after the illumination is finished can be effectively erased by utilizing the reverse bias voltage, so that the device is quickly restored to the initial state, and the repeatable cycle operation of the device is ensured.

The X-ray photoelectric conversion unit may have a plurality of detection pixel points, each of which may be independently subjected to the action of the X-rays and independently generate a current. Therefore, when detection is performed, detection is performed for each pixel to be detected, and the charge amount is calculated correspondingly. And then according to the corresponding relation between different electric charge amounts and gray scales, each pixel point is correspondingly changed into a pixel point with different gray scales. Then all the pixels can correspondingly obtain a gray scale map.

The detection pixel points in the X-ray photoelectric conversion units therein may be configured as follows.

Referring to fig. 1, the specific preparation steps are as follows:

1. pretreatment of a substrate:

a piece of quartz substrate 11 is ultrasonically cleaned by using organic reagents such as acetone, alcohol and the like, and is dried by using dry high-purity nitrogen. Placing it in a container filled with Ga ₂ O ₃ Magnetron sputtering equipment of ceramic target (purity 99.999%).

2. Preparation of the X-ray detection active layer 12:

starting the vacuum system, and the like to reach a set back vacuum, such as 3.0X10 ^-4 Pa, 10sccm Ar is introduced as sputtering gas, and a gallium oxide layer with a thickness of 150nm is sputtered under the conditions of 0.4Pa background air pressure and 60W sputtering power.

In order to obtain a plurality of pixel points, device isolation operation can be performed on the gallium oxide layer, so that a whole gallium oxide layer is manufactured into a plurality of independent 'small' gallium oxide blocks. Each gallium oxide block is a pixel point. The whole X-ray photoelectric conversion unit is provided with a plurality of pixel point sets which are uniformly distributed in determinant and are distributed in two dimensions.

3. Preparation and patterning of the electrode:

continuously depositing a 40nm Au film on the gallium oxide film in the step 2, exposing by adopting a photoetching technology to form an electrode structure, etching away redundant metal by utilizing commercial Au etching liquid, and then dissolving away the redundant electrode by utilizing acetone to obtain interdigital top electrodes with parameters of 5 mu m of line width, 5 mu m of interval and 300 mu m of length, wherein 75 pairs of interdigital top electrodes are formed; in fig. 1, a first top electrode 131 and a second top electrode 132 are shown, respectively.

Based on the above-described X-ray photoelectric conversion unit structure, application is performed in the following manner, referring to fig. 2.

The object 202 to be detected is placed between the radiation source 200 and the X-ray photoelectric conversion unit 204. And the output electrode of the X-ray photoelectric conversion unit 204 is electrically connected with the positive and negative electrodes (not shown) of a power supply, and the power supply provides a preset voltage to the X-ray photoelectric conversion unit 204, and records the dark current without X-ray radiation at this time as a background current I ₀ 。

The X-rays are then emitted by the radiation source 200, forming emitted X-rays 201. After the outgoing radiation 201 passes through the object 202 to be detected, it is partly absorbed, partly transmitted; wherein the transmitted formation transmits X-rays 203 and irradiates an X-ray photoelectric conversion unit 204. The real-time change of the output current of the X-ray photoelectric conversion unit 204 under the X-ray irradiation and the applied voltage at this time is acquired. After the irradiation for a preset time period, stopping X-ray irradiation, and continuously recording the current real-time change of another preset time period.

The acquired time/current two-dimensional data array is processed using an integral function as shown in equation 1 below.

Wherein the X-ray turning-on moment is integral 0 point, and the acquisition current (dark state current) before irradiation is used as background current I ₀ . The raw current value obtained by acquisition is defined as I ^meas (t). Effective response current is I ^meas (t)-I ₀ The method comprises the steps of carrying out a first treatment on the surface of the The preset irradiation time of X-rays is t.

After the irradiation is finished, the effective response current is time integrated at the time t is more than or equal to t to obtain an output signal S ^output (t). Wherein t is at least greater than the duration from turning on the X-rays to turning off the X-rays, i.e. the integration time also comprises a preset duration after turning off the X-rays. The total integration time can be appropriately selected according to the need. For example, in the application of medical CT devices, taking the medical image imaging quality criteria as an example, imaging structures are classified into three levels of invisible, visible and clear visible, depending on the level of visibility of important anatomy and details.

Therefore, when the integration end point is selected, the corresponding integration end point time can be correspondingly selected according to the presentation effect of the imaging details. Illustratively, the method of determining an acquisition endpoint for acquiring an electrical signal of a photoelectric conversion element, thereby determining an integration endpoint, comprises: when the current value acquired from the photoelectric conversion element after stopping the X-ray irradiation is equal to the current value acquired from the photoelectric conversion element before the X-ray irradiation.

Since the dark current collected by the X-ray photoelectric conversion element before the X-ray irradiation is equal to the current collected from the X-ray photoelectric conversion element after the end of the X-ray irradiation, it is indicated that the continuous photoconductive effect has ended at this time. Therefore, the current signal that is collected again thereafter does not effectively improve the signal-to-noise ratio and the contrast of the image.

After the integration period, i.e. after a preset period after turning off the X-rays, a reverse voltage may be applied to the X-ray photoelectric conversion unit 204 in order to reset it in preparation for the next detection. I.e. changing the voltage bias state, for example by switching the working electrode or setting a pulsed bias, the current of the X-ray photoelectric conversion unit 204 is quickly restored to the initial state for continuous operation.

To obtain an accurate image, in some examples, a subject having an image that has been predetermined may be selected and imaged in the manner described above. And then restoring the corresponding relation between the gray distribution of the image and the integral data according to the obtained integral data. In this way, when detecting other objects, after the integral data is obtained, the image of the detected object can be obtained according to the correspondence relation. Thus, such a scheme is a scheme of pre-correction.

In other examples, a pre-designed object may be placed on the object to be detected, and then detected in the manner described above. After the integral data is obtained, the image of the previously designed object is "restored" therefrom, and then the image of the corresponding object to be detected can be obtained based on the data of the remaining portion of the process.

Based on the above application manner, an imaging apparatus may be correspondingly proposed in the examples. It should be noted that the illustration is in the form of X-ray imaging. However, other wavelengths of light may be used for imaging. The light is correspondingly matched to the photoelectric conversion device, i.e. the light can be such that it produces a continuous photoconductive effect. That is, materials with a sustained photoconductive effect are also sensitive to this wavelength; which is capable of generating an electrical signal upon irradiation of the light, and which is also capable of generating an electrical signal continuously over a period of time after the light has ceased.

Generally, an imaging apparatus includes an irradiation source, a photoelectric conversion element, and an electrical signal collector. Wherein the irradiation source is arranged opposite to the photoelectric conversion element, and the electric signal collector is electrically connected with the photoelectric conversion element.

The irradiation source is used for generating X-rays for irradiating the object to be measured, and the mode of generating the X-rays can be realized by controlling the irradiation source. In some examples, the control of the irradiation source is manipulated by its own control means. Alternatively, in some other examples, the imaging device may be configured with a separate control device for manipulating the irradiation source. For example, the control device is an irradiation manipulator which is connected with the irradiation source in a matching way. In other words, the irradiation source may be a device provided with only an X-ray source, or may be a device provided with a control device outside the source and integrated. In the present example, the irradiation source is provided in the form of a light source.

Further, the image forming apparatus may be further provided with a power supply. The power supply is electrically connected with the photoelectric conversion element and is used for providing electric energy for the photoelectric conversion element. When the detection is performed, the power supply supplies a set voltage to the photoelectric conversion element. The voltage may be a forward voltage applied during normal detection or a reverse voltage applied after one detection is completed. In some examples, the power supply may be integrated with the electrical signal collector so that current data of the photoelectric conversion element can also be recorded or collected when power is supplied. For example, the power supply and the electric signal collector can be optionally provided by a power meter; exemplary power meters are the commercial Keithley source meters or monolithically integrated dc power supplies and current collection components.

Since the efficiency and accuracy of manually processing data is relatively poor and may be difficult to implement effectively, the imaging device in the example corresponds to a configuration information processor. The information processor is used to process the electrical signals/data to produce an image. The electrical signal at least comprises current data corresponding to any moment in the detection process and dark current of the photoelectric conversion element, and can also comprise data such as voltage value provided for the photoelectric conversion element. The information processor may be various electronic components or a collection thereof having data processing capabilities. Such as a Central Processing Unit (CPU), a Micro Control Unit (MCU), an editable logic controller (PLC), a Programmable Automation Controller (PAC), an industrial control computer (IPC), a Field programmable gate array (Field-Programmable Gate Array, FPGA), a specially applied integrated circuit chip (ASIC chip, application Specific Integrated Circuit), etc.

Still further, the imaging device may also configure one or both of the memory and the display. The two are electrically connected with the information processor in a matching way, and can be also selectively electrically connected with the electric signal collector in a matching way. As the name suggests, the memory therein may be used to store the aforementioned electrical signals and images generated by the information processor. The display may be used to display images, or may be used to display recorded data or other content recorded by the information processor or processed to obtain results.

In addition, the imaging device may also be configured with a remote terminal device for ease of operational use or viewing results. The remote terminal device may be connected to the controlled device through a wired network or a wireless network to control the controlled device. Wherein the controlled device may be a different specific device according to different configurations of the imaging device. For example, the controlled device may be a radiation source, or a combination of one or more of the foregoing power meters, signal processors, radiation operators, displays, and memories.

It will be appreciated by those skilled in the art that the X-ray source, the object under test, the X-ray photoelectric conversion unit, the source table, and the data processing software of the present application are not limited to the kinds defined in the embodiments.

In particular, the X-ray photoelectric conversion unit is not limited to the amorphous gallium oxide material in the embodiment, and the continuous photoconductive phenomenon and the corresponding current memory effect after the X-ray irradiation are realized by regulating the defect content in other materials such as oxide, nitride, halide and perovskite. Then, these conditioned materials can be used for self-enhanced detection imaging after short-time low-dose X-ray irradiation.

The description will be described below with reference to specific examples.

Example 1

The self-enhanced X-ray imaging detection system of the present embodiment is shown in fig. 3, and mainly includes the following parts.

1. An X-ray source:

A12W miniature X-ray source has X-ray beam cone angle range of 48 deg. and X-ray tube current of 10-300 muA@40 kV.

2. The object to be measured:

the object to be measured is the symmetrical letter H constructed on an organic plastic substrate. Wherein the letter and the frame portion constitute areas with different absorption efficiencies on the same object (substrate).

3. An X-ray photoelectric conversion unit:

the magnetron sputtering equipment deposits an amorphous gallium oxide film at room temperature as an oxide active layer to prepare an X-ray photoelectric conversion unit, and the schematic diagram of the cross-section structure of the device is shown in figure 1.

4. And (3) data acquisition:

and (3) conducting wire connection is carried out on the top electrode of the X-ray photoelectric conversion unit device by utilizing low-temperature cured conductive silver adhesive and copper wires so as to electrically connect the Au electrode with the Keithley2636B source surface. The source meter can record the current value of the device in real time when the X-ray photoelectric conversion unit is applied with a constant 10V bias.

Three X-ray photoelectric conversion unit devices are respectively placed under X-ray irradiation under an X-ray source, and the tube voltage of the radiation source is respectively controlled to be 40kV and the tube current is respectively controlled to be 50, 125 and 200 mu A. An X-ray periodic response curve is obtained from the source table, see fig. 4. Fig. 5 is a graph showing the change of effective response current with time of the three photoelectric conversion units in fig. 4 at the 6 th cycle (70 to 80 seconds).

After the radiation was turned off, the current and time to continue photoconduction were recorded. During the test, the X-ray source remains on and off for a period of time, and the current is recorded using the source table. The time interval for each cycle of X-ray irradiation to be on and off is 5s (other time intervals are possible, as is standard for the occurrence of a distinct persistent photoconductive phenomenon).

As can be seen from fig. 4 and 5, the X-ray photocurrent gradually increases with the irradiation time and with the increase in the irradiation dose (the larger the irradiation source current, the higher the irradiation dose). And the sustained photoconductive effect of the device gradually increases after switching off the X-ray source. This indicates that the photocurrent corresponding to continuous photoconduction is positively correlated with the irradiation time and irradiation intensity, and shows a remarkable memory effect.

5. And (3) data processing:

by taking the moment of X-ray opening asZero crossing and taking the dark current before the irradiation period as background current I ₀ The acquired original current value is defined as I ^meas (t) the effective response current is I ^meas (t)-I ₀ 。

6. Time integration processing:

the effective response current in fig. 5 is subjected to time integration processing.

The time integration processing adopts an integral module in the origin software to obtain a time integration curve S ^output (t) as shown in fig. 6, it is apparent that the gain effect of the time integration treatment remains due to the continuous photoconductive phenomenon in fig. 4 and 5 after the end of the X-ray irradiation for 5 s.

7. Analog imaging display:

simulating an H-shaped object to be tested by using the data in FIG. 6, wherein the letter character part corresponds to low-dose X-rays with the tube current of 50 microamps; the periphery of the tube is the part with the lowest X-ray absorption, and corresponds to high-dose X-rays with the tube current of 200 microamps; the frame is an X-ray medium absorption component and corresponds to medium-intensity X-rays with the tube current of 125 microamps.

At the moment of turning off the X-ray, the image of the object to be measured is constructed by taking the time integral value of the current in the photoelectric conversion elements (1, 2 and 3) at the time t=5s in fig. 6, and the imaging effect is shown in the left graph of fig. 7, namely a.

After the integration time end point is 2.5 seconds after the X-ray is turned off, the current time integration value in the photoelectric conversion elements (1, 2 and 3) at the moment of t=7.5 s in fig. 6 is taken to construct the image of the detected object, and the imaging effect is shown as a middle graph in fig. 7, namely B;

after the end point of the integration time is 5 seconds after the X-ray is turned off, the image of the measured object is constructed by taking the time integral value of the current in the photoelectric conversion elements (1, 2 and 3) at the time t=10s in fig. 6, and the imaging effect is shown as a right graph of fig. 7, namely C.

The results show self-enhancement of the imaging effect of the device after short-time X-ray irradiation, and effectively reduce the X-ray irradiation dose received by an imaging object.

Since the continuous photoconductive phenomenon is maintained for a long time without changing the voltage bias state of the photoelectric conversion element, the continuous operation efficiency and the imaging accuracy of the photoelectric conversion element are greatly affected. For this reason, a reverse bias voltage is applied to the X-ray photoelectric conversion unit device, the result of which is shown in fig. 8; the result shows that the constant bias voltage with alternating positive and negative can effectively erase the continuous photoconductive effect, and continuous effective operation of the device is realized.

Comparative example 1

The X-ray imaging detection system of this embodiment is identical to that of embodiment 1 except that the X-ray photoelectric conversion unit having the continuous photoconductive effect is not used.

The X-ray photoelectric conversion unit in this example was completely free of the persistent photoconductive effect, and quickly recovered to the initial state before irradiation after X-ray shutdown, and the comparison result of the effective current (dotted line portion) of the comparative device of this example with the effective current (solid line portion) in fig. 5 of example 1 was shown as a comparison curve in fig. 9. The results of the comparison of the effective current time integral curve (open graph) of the comparative device of this example with the effective current time integral curve (solid graph) shown in fig. 6 of example 1 are shown in fig. 10.

As shown in FIG. 9, in the embodiment, during the process of irradiating the device by X-rays (t is less than or equal to 5 s), the time integral of the effective current has obvious gain; however, after the X-ray is turned off, the effective current of the device is close to 0 because the current is quickly restored to the state before irradiation, so that the time integral of the effective current is basically unchanged in the subsequent integral processing, and the gain is close to 0.

The effect of constructing the imaging of the measured object by using the effective current time integral curve without the continuous photoconductive effect is shown in fig. 11, and the imaging effect is not improved with time because the effective current is close to 0 and the time integral process has no gain after the X-ray is turned off.

Example 2

The components and data acquisition and processing modes of the X-ray imaging detection system of this embodiment are exactly the same as those of embodiment 1, except that:

the electrode material of the X-ray photoelectric conversion unit in the system of the present example is ITO. Fig. 12 shows a graph of the periodic bias voltage applied to the X-ray photoelectric conversion element during detection and the current and voltage acquired from the element over time.

Wherein, after each period of X-ray imaging detection is finished, a short-time reverse bias voltage of 10 seconds is applied to the X-ray photoelectric conversion unit, and then the device is switched to an operating state under a forward 10V bias voltage. As can be seen from fig. 12, the dark current of the device is obviously recovered, and the continuous operation effect of the device is ensured.

In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application are clearly and completely described in the foregoing description with reference to the accompanying drawings in the embodiments of the present application. It will be apparent that the embodiments described are some, but not all, of the embodiments of the present application. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the present application, it should be noted that the azimuth or positional relationship indicated in each is based on the azimuth or positional relationship shown in the drawings, or the azimuth or positional relationship that is commonly put in use of the product of the application, is merely for convenience of description and simplification of the description, and is not indicative or implying that the apparatus or element referred to must have a specific azimuth, be configured and operated in a specific azimuth, and therefore should not be construed as limiting the present application.

In the description of the present application, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art in a specific context.

In this application, all of the examples, embodiments, and features of the present application may be combined with one another without contradiction or conflict. In this application, conventional equipment, devices, components, etc., are either commercially available or homemade in accordance with the present disclosure. In this application, some conventional operations and devices, apparatuses, components are omitted or only briefly described in order to highlight the focus of the present application.

The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. Use of a material having a persistent photoconductive effect to improve the signal-to-noise ratio of an X-ray detector without increasing the radiation dose.

2. The use according to claim 1, characterized in that the material with a persistent photoconductive effect is made as a sensitive element in an X-ray detector;

optionally, the material with persistent photoconductive effect is fabricated as a photoelectric converter in an X-ray detector;

optionally, the material with continuous photoconductive effect comprises amorphous Ga ₂ O ₃ 。

3. The use according to claim 2, wherein the photoelectric converter comprises: a substrate; by amorphous Ga ₂ O ₃ An active layer formed on the substrate; an electrode formed on the active layer; wherein the electrode is a conductive glass and the conductive glass is used to increase the speed of the photoelectric converter in response to a reverse voltage to eliminate the persistent photoconductive; optionally, the conductive glass is ITO;

alternatively, the photoelectric converter includes: a substrate; by amorphous Ga ₂ O ₃ An active layer formed on the substrate; an electrode formed on the active layer; wherein the electrode comprises a metal electrode or a conductive glass electrode; optionally, the electrode is a gold electrode.

4. An imaging method, the imaging method comprising:

receiving transmitted light generated by irradiating a target object to be imaged with X-rays by using a photoelectric conversion element, wherein the photoelectric conversion element is made of a material having a continuous photoconductive effect;

5. The imaging method of claim 4, wherein the imaging method comprises: providing a reverse voltage to the photoelectric conversion element after collecting an electrical signal of the photoelectric conversion element;

optionally, the reverse voltage is a reverse pulse voltage;

optionally, the preset duration is determined by determining an acquisition end point of acquiring the electrical signal of the photoelectric conversion element, and the method for determining the acquisition end point includes: when the current value acquired from the photoelectric conversion element after stopping the X-ray irradiation is equal to the current value acquired from the photoelectric conversion element before the X-ray irradiation.

6. The imaging method of claim 4, wherein processing the electrical signal to obtain image information corresponding to the target object comprises:

7. An image forming apparatus, characterized in that the image forming apparatus comprises:

an irradiation source for generating X-rays;

8. The image forming apparatus according to claim 7, wherein the image forming apparatus comprises: a power supply electrically connected to the photoelectric conversion element for supplying forward and reverse voltages to the photoelectric conversion element;

optionally, the power supply provides a periodic bias voltage to the photoelectric conversion element;

9. The imaging device of claim 7, wherein the imaging device comprises one or more of the following definitions:

first definition: the imaging device comprises an irradiation manipulator which is connected with the irradiation source in a matching way and is used for controlling the irradiation source;

a second definition: optionally, the imaging device includes: an information processor in matched connection with the photoelectric conversion element for processing the electrical signal to generate an image;

third definition: the image forming apparatus includes: a display for displaying the image, the display being electrically connected to the information processor;

fourth definition: the image forming apparatus includes: and the memory is used for storing the image and is electrically connected with the information processor.

10. The imaging apparatus according to any one of claims 7 to 9, wherein the imaging apparatus includes a remote terminal connected to a controlled apparatus through a wired network or a wireless network to control the controlled apparatus.