JPH0769480B2 - X-ray image detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an X-ray image detector used in an X-ray fluoroscopic inspection of industrial products, the medical field, and the like, and particularly as an X-ray image conversion element, an electro-optical effect and a light beam. The present invention relates to an X-ray image detector using a single crystal plate having both a conduction effect.

(Background Art) Conventionally, bismuth silicon oxide (BSO; Bi ₁₂ SiO
₂₀ ), bismuth germanium oxide (BGO: Bi ₁₂ GeO
_The single crystal plate that has both electro-optical effect and photoconductive effect, such as ₂₀ ), is used as an image conversion element, so-called PROM (Pockels read-out optical modulator) element, as a two-dimensional image processing device and information processing by light. Various uses have been studied for use in devices and the like. The basic structure of this PROM element is, for example, as shown in FIG. 1, for example, insulating layers 4 and 4 are provided on both sides of a BSO single crystal (wafer) 2, respectively, and a transparent electrode of indium oxide or the like is further formed thereon. It has a structure with 6,6.

By the way, the writing operation using such a PROM element is
Usually, it will be performed as follows. First,
A predetermined voltage is applied from the external power supply 8 between the electrodes 6 provided on both sides of the BSO crystal 2, and a uniform electric field is formed in the crystal perpendicularly to the crystal plane. Light (450
An image of about (nm) is formed. Since the BSO crystal 2 has a photoconductive effect exhibiting high sensitivity in the blue region, carriers are excited in the crystal according to this writing light amount. And
The carriers move in the crystal due to the electric field generated by the applied voltage, reach the insulating layer 4, and form a charge distribution corresponding to the writing light amount distribution. In the portion where the carrier exists, the electric field inside the crystal is reduced by the electric field created by the carrier, thereby forming the electric field distribution corresponding to the distribution of the writing light amount, which is recorded in the BSO crystal 2.

On the other hand, the read operation of the image recorded in this way is
This is performed by utilizing the electro-optical effect of the crystal 2. That is, the BSO crystal 2 has a birefringence proportional to the electric field strength inside the crystal due to the electro-optic effect. The directions of the two principal axes of the index ellipsoid are perpendicular to the electric field direction. Therefore, as shown in FIG. 2, red (about 600 nm) linearly polarized light having a polarization plane in the direction of the bisector of the two principal axes of the index ellipsoid is passed through the polarizing plate (polarizer) 10. When the light is incident on the PROM element 12 having the structure as shown in FIG.
The readout light becomes elliptically polarized light according to the local electric field in the crystal of the crystal 2. Since the photoconductive effect of the BSO crystal 2 has no sensitivity in the red region, the recorded information is not destroyed by the irradiation of the reading light. Then, by placing a polarizing plate (analyzer) 14 which is orthogonal to the input side polarizing plate 10 on the output side, it is possible to obtain a read light intensity corresponding to the ellipticity of the elliptically polarized light, so that the PROM element 12 records. The input image that has been displayed can be read.

The image recorded on the BSO crystal 2 of the PROM element 12 is erased by irradiating the entire surface of the BSO crystal 2 with intense blue light. Further, the PROM element 12 is configured by using a BGO crystal or the like in addition to the BSO crystal, and has the same function as above.

On the other hand, there is known a method of using X-rays as a writing light of an input image of such a PROM element [M. Graser, Jr. et.al.
pl. Phys. Lett. ". 34 (8) .15. April (1979)]. This is because, as in the case of the blue light described above, since a single crystal such as BSO has a highly sensitive photoconductive effect with respect to X-rays, it is possible to write even an X-ray image. . Note that this technique employs the same element configuration as that in FIG. 1 except that X-rays are used as the writing light, and the image reading method after image information recording is also the same.

However, X using the previously proposed PROM element
The line image detection method has many problems in practical use and is not yet in practical use. One of the main reasons for this is that the resolution of the optical system structure is limited. That is, in such a conventional X-ray image detection method, since an optical system structure in which the read light is transmitted through the PROM element is adopted, the X-ray source is used as the light source or the image of the read light centering around the PROM element. It is not possible to irradiate X-rays from the front of the PROM element because they must be placed on the same side of the detector as any of them and therefore their optics block the X-rays. Further, when the object to be inspected is placed in contact with the PROM element, the reading light is blocked. Therefore, the distance between the PROM element and the object to be inspected must be separated so that the reading light is not blocked. Moreover, unlike visible light, it is impossible to form an X-ray image by an optical system. For these reasons, it is difficult for the conventional X-ray image detection method to write a clear X-ray image on the PROM element, and the "blurring" of the X-ray image is more difficult than the resolution performance of the PROM element. However, it did not fully utilize the performance of the PROM device.

(Problem to be solved) Here, the present invention has been made in view of such circumstances, and the problem to be solved is to irradiate a PROM element with X-rays without being blocked by an obstacle. And it is possible to read the image,
An object of the present invention is to provide an X-ray image detector capable of obtaining an image with high resolution.

(Solution Means) The present invention, in order to solve the above-mentioned problems,
A single crystal plate having an electro-optical effect and a photoconductive effect, a reflective conductive layer provided on one surface of the single crystal plate and capable of reflecting light but transmitting X-rays, and the other of the single crystal plates. A transparent layer which is permeable to light and is provided on the insulating layer and which applies a predetermined electric field to the insulating layer and the single crystal plate in cooperation with the reflective conductive layer. X having a conductive layer
In an X-ray image detector using a line image conversion element, an X-ray irradiation source is disposed on the side of the image conversion element on which the reflective conductive layer is provided, and X-ray irradiation from the X-ray irradiation source is performed. While allowing an X-ray image to be written in the image conversion element, a light source for irradiating the image conversion element with predetermined reading light on the side of the image conversion element on which the transparent conductive layer is provided, And an optical system for forming an image of the readout light reflected from the image conversion element, and the X-ray image written in the image conversion element is read by the light source and the optical system. The feature is an X-ray image detector which is a feature.

In such an X-ray image detector, it is advantageous to arrange a reflecting mirror in the optical path of the optical system so that the X-ray irradiation direction from the X-ray irradiation source and the optical axis of the imaging system are perpendicular to each other. In addition, a medium capable of blocking the X-rays and transmitting the read-out light may be arranged in the optical path of the optical system.

In one aspect of the X-ray image detector according to the present invention, a plurality of the image conversion elements are used, and
The writing position of the X-ray image by the ray irradiation source, the reading position of the X-ray image by the light source and the optical system, and the erasing position of the X-ray image are made different, and the writing position is moved by moving these image conversion elements. A configuration is adopted in which the reading position and the erasing position are sequentially arranged.

Further, according to the present invention, a surface emitting light source is used as a light source, or a configuration in which the optical system is provided with a lens means for changing the visual field range of the read image is also adopted.

Furthermore, in the present invention, by controlling the X-ray irradiation amount,
In order to obtain an X-ray image detector capable of setting an optimum irradiation amount and obtaining a clear image, it is advantageous that (a) X-ray measuring means for measuring an X-ray irradiation dose from an X-ray irradiation source. And an X-ray irradiation control device for controlling the X-ray irradiation time by the X-ray irradiation source based on the X-ray irradiation dose measured by the X-ray measuring means, and (b) from the light source. Measuring means for measuring the intensity of the reading light of the X-ray irradiation source, and X based on the reading light intensity measured by the light measuring means.
A configuration in which an X-ray irradiation control device that controls the irradiation time of the rays is further provided is adopted.

Further, in such an advantageous aspect of the X-ray image detector according to the present invention, the reading light from the light source is perpendicular to the image conversion element on the side where the transparent conductive layer is provided. In the meantime, a structure in which a convex lens for forming an image of the readout light reflected from the image conversion element is provided while irradiating the same with the above is adopted.

(Specific Configuration / Example) Hereinafter, the configuration of the present invention will be described more specifically based on an example shown in the drawings.

First, FIG. 3 shows an example of an X-ray image conversion element used in the X-ray image detector according to the present invention, in which 22 denotes a single element having an electro-optical effect and a photoconductive effect. A crystal plate, for example, bismuth silicooxide (Bi
₁₂ SiO ₂₀ ) and bismuth germanium oxide (Bi ₁₂ GeO
₂₀ ) and other well-known single crystal materials. In addition,
The single crystal plate 22 generally has a thickness of about 10 μm to 5 mm, and both sides thereof are polished by a known appropriate method.

Then, on one surface of such a single crystal plate 22, the metal thin film electrode 23 as a reflective conductive layer according to the present invention has a predetermined thickness, in other words, reflects light but transmits X-rays. It is formed in the thickness to obtain. In addition, this metal thin film electrode
As the material of 23, a conductive material having an excellent X-ray transmittance such as gold, silver, platinum, aluminum, and metal beryllium is preferably used. The thickness of the metal thin film electrode 23 is
It is thin enough to allow X-rays to pass therethrough, and generally has a thickness of about 1 μm or less, so that an X-ray image can be written from the side of the metal thin film electrode 23. On the surface of, the reading light can be reflected, and thus a reflection type reading optical system can be adopted, and the reading light source and the imaging portion can be located on the same side with the X-ray image conversion element as the center. Thus, the writing portion and the reading portion can be completely separated.

The single crystal plate on which the readout optical system is provided
An insulating layer 24 capable of transmitting light is provided on the other surface of 22 similarly to the conventional PROM element, and a transparent electrode (conductive layer) made of a known transparent conductive material such as indium oxide is further formed thereon. Layer) 26 is formed. Then, by applying a voltage (for example, about 0 to 30 KV) from an external power source 28 between the transparent electrode 26 and the metal thin film electrode 23,
A predetermined electric field can be applied to the single crystal plate 22 and the insulating layer 24.

By the way, the insulating layer 24 provided on the single crystal plate 22.
Can be formed of known organic insulating materials such as polyparaxylene and polystyrene, and inorganic insulating materials such as glass and mica.

Further, in the formation of the transparent electrode 26 that applies a predetermined electric field to the single crystal plate 22 and the insulating layer 24, the same method as the conventional method is adopted. A method of directly forming a transparent electrode or a transparent electrode plate formed by providing a transparent electrode layer on a predetermined plate body such as (b) glass is attached onto the insulating layer 24 by using an appropriate optical adhesive. Method etc.
Adopted appropriately.

The present invention configures an apparatus (X-ray image detector) for writing and reading an image by using the X-ray image conversion element having such a configuration. An X-ray source (X-ray irradiation source) is arranged on one side of the image conversion element, and a reading system is arranged on the other side of the X-ray image conversion element.

That is, as shown in FIG. 4, an X-ray image conversion element
An X-ray source 32 is arranged on the side of the metal thin-film electrode 23 of 30. The X-ray source 32 irradiates the inspection object 34 with X-rays, whereby image information to be recorded is displayed. The X-rays possessed are formed, and the X-ray image conversion element 30 is irradiated with the surface on the side where the metal thin film electrodes 23 are formed. As a result, the intended X-ray image is written on the single crystal plate 22 of the image conversion element 30.

On the other hand, the readout optical system is arranged on the other side of the X-ray image conversion element 30, in other words, on the side where the transparent electrode 26 is provided, where it has a predetermined readout light, that is, a photoconductive effect. Light source 36 for irradiating the X-ray image conversion element 30 with light that does not destroy the written information, for example, red light.
A polarizer 38, a convex lens 42 for vertically irradiating the X-ray image conversion element 30 with the irradiation light and for forming an image of the reflected reading light, and a beam splitter 40 for separating the irradiation light and the reflected light. , An analyzer 44 for obtaining a light intensity according to the ellipticity of the elliptically polarized light of the reading light, and a CCD image pickup device 48 of the CCD camera 46, which is a light receiving means for receiving the reading light transmitted through the analyzer 44, It is arranged. Here, the beam splitter 40 can be replaced by a half mirror, and the polarizer 38, the beam splitter 40, and the analyzer 44 can be used.
Can be replaced by PBS (Polarized Beam Splitter).

Therefore, in the X-ray image detector having such a configuration,
The writing of the X-ray image is performed on one side of the X-ray image conversion element 30, while the reading of the X-ray image written on the X-ray image conversion element 30 is performed on the other side of the X-ray image conversion element 30. Since the writing and reading parts are completely separated, the structural interference between the X-ray image writing system and the reading optics can be effectively avoided, and The X-ray image can be written by irradiating the X-ray from the front with the object to be inspected (34) as close to the X-ray image conversion element 30 as possible, and a clear X-ray can be written. It has become possible to obtain an X-ray image detector having a high resolution, which can advantageously obtain an image and can sufficiently discriminate even a fine metal line of about 25 μm.

A fifth example of another example of the X-ray image detector according to the present invention
In the figure, a reflecting mirror 50 is arranged in the optical path of the reading optical system, and the reading light reflected by the metal thin film electrode 23 of the X-ray image conversion element 30 is reflected by the reflecting mirror 50 from the X-ray source 32 to the X-ray source 32. The X-ray irradiation direction and the imaging system optical axis are perpendicular to each other, so that the X-ray irradiation direction and the imaging system optical axis are perpendicular to each other. In order to prevent the portions (46, 48) from being irradiated with X-rays, it is possible to advantageously extract a good image free from noise due to X-rays.

When an electronic component is irradiated with X-rays, electric charges are excited inside the semiconductor due to X-ray photons having high energy, which adversely affects the component and, in the worst case, causes destruction. Even in the case of the target X-ray image detector, the same is true when a CCD camera or image pickup tube is used to detect the read-out image. This is because the noise on the monitor will disturb the image on the monitor.

Further, in order to better prevent noise from being included in the read image due to such X-ray irradiation, a shield plate 52 such as a lead plate is provided between the X-ray source 32 and the read optical system as shown in the drawing. The X-ray from the X-ray source 32 is arranged, and the CCD camera 46,
It is desirable not to reach the image pickup device 48 or the like.

In the X-ray image detector shown in FIG. 5, the read light is emitted from a light source (36) arranged in a direction perpendicular to the plane of the paper through a beam splitter (38) through a polarizer (38).
The light is made incident on the beam splitter 40, and is further made incident from the beam splitter 40 via the convex lens 42 and the reflecting mirror 50 to the side of the X-ray image conversion element 30 where the transparent electrode 26 is provided. Further, the readout light reflected from the X-ray image conversion element 30 is reflected by the reflecting mirror 50 and then passes through the convex lens 42, the beam splitter 40, and the analyzer 44, and the CCD image pickup of the CCD camera 46 is performed as described above. The light is received by the element 48.

Further, in order to eliminate the mixing of noise in the read image due to such X-ray irradiation, the reflection mirror 50 as in the above example is provided so that the optical axis of the imaging system does not coincide with the X-ray irradiation direction. In addition, a medium that blocks X-rays but allows read-out light to pass therethrough, such as lead glass, is used in the X-ray rather than the imaging device portion (46, 48).
The line image conversion element 30 side, for example, in FIG.
If it is arranged between the CCD image pickup device 48 and the CCD image pickup device 48, even if the X-ray irradiation direction coincides with the optical axis of the imaging system,
It is possible to obtain a good image without line noise.

By the way, the X-ray image conversion element cannot perform real-time image output because it writes and reads images alternately. To approach the near real-time operation, the write / read / erase cycle may be shortened, but the voltage applied to the image conversion element is usually as high as several KV, and the speed cannot be increased easily. Moreover, since the writing speed and the erasing speed are determined by the physical properties of the crystal plate (BSO etc.) of the image conversion element,
Speeding up beyond a certain limit is impossible.

Therefore, in the X-ray image detector according to the present invention, a plurality of X-ray image conversion elements 30 are used and rotated as shown in FIG. A configuration is adopted in which the write, read, and erase operations for each element 30 are performed in parallel by being arranged on the table 54 and rotated. In short, while using a plurality of X-ray image conversion elements 30, the writing position of the X-ray image by the X-ray source (32), the light source (36) and the optical system (38,40,42,44,46,48). The X-ray image read position by (4) is made different, and the X-ray image conversion elements 30 are sequentially moved so as to be sequentially arranged at the write position and the read position. Further, for the X-ray image conversion element 30 after being read,
By sequentially illuminating the entire surface with blue light, the recorded images are erased.

Further, in the X-ray image detector, when the read-out image is detected by the camera (46) and displayed on the monitor screen, the resolution of the final image is limited by the number of pixels of the monitor screen, so that it is very effective. Even if an image conversion device with a large area and high resolution is manufactured, all the pixels cannot be observed at once on the monitor screen. However, as shown in FIGS. By providing the lens means for changing the visual field range, it is possible to read out the whole image of the image or a magnified image of a part thereof according to the purpose. In the example shown in FIG. 7,
A field lens 56 is arranged between the analyzer 44 and the CCD image pickup device 48, and a read image is picked up by a two-lens imaging system including the field lens 56 and the convex lens 42. By changing the focal length of the lens 56 and its position, the readout range and magnification of the image can be easily changed. The focal length of the field lens 56 and its position can be changed, for example, by attaching various field lenses 56 to the lens holder 58 and rotating the lens holder 58 as shown in FIG. .

Further, in the X-ray image detector according to the present invention shown in FIG. 9, the surface emitting light source 60 is used as the light source of the reading optical system, which makes it possible to reduce the size of the optical system.
It is simple, which enables downsizing of the entire X-ray image detector. In the reflection type image conversion element 30, the read light is collimated and therefore the image conversion element 30 is read.
This is because the state in which the light is vertically incident on the lens is highly efficient with respect to the light intensity and a bright image can be formed. On the other hand, if an attempt is made to irradiate a large area with a single light source in order to eliminate unevenness in the brightness of the image, the distance between the light source and the image conversion element becomes large, and the X-ray image detector This is a factor that hinders miniaturization. The surface emitting light source 60
For example, a surface emitting LED, a surface emitting fluorescent lamp, an electroluminescent element (EL) luminous body, etc. are used.

In addition, the difference in the X-ray transmitted light amount of the inspected object (34) causes X
An X-ray image detector that forms a line image is required to have good gradation representation of an image and to have a wide dynamic range.
Since the range is relatively narrow at about 15 dB, it is easy to unexpose or overexpose it depending on the X-ray irradiation condition, and it becomes difficult to manage it, but as shown in FIG.
By providing a control system for controlling the X-ray irradiation amount, a clear image can be advantageously obtained.

That is, in FIG. 10, the light separated by the half mirror 62 arranged in the optical path of the image forming system of the readout light is focused by the convex lens 64, and the light intensity thereof is measured by a light measuring device 66 such as a photomultibryer or a photodiode. Based on the read light intensity measured by the light measuring device 66, the writing amount is estimated, the optimum X-ray irradiation condition is determined by the X-ray irradiation control device 68, and the X-ray source 32
Therefore, the X-ray irradiation time can be controlled.

Further, instead of such reading light intensity measurement, an X-ray source
It is also possible to measure the X-ray irradiation dose from 32 and control the X-ray irradiation time based on the measured dose. That is,
An X-ray dosimeter 70 such as an ionization chamber dosimeter, a scintillation detector, a semiconductor detector, etc. arranged on the side of the X-ray image conversion element 30.
Thus, the X-ray irradiation dose from the X-ray source 32 is measured, and the X-ray irradiation control device 68 controls the X-ray irradiation time by the X-ray source 32 based on the measured value.

The specific configuration of the present invention has been described above in detail based on some preferred embodiments according to the present invention. However, the present invention does not control what kind of control is performed by such an embodiment or a specific description based on it. The present invention is never subject to the above, and may be carried out in a mode in which various changes, modifications, improvements and the like are added based on the knowledge of those skilled in the art without departing from the gist of the present invention, and the present invention is also It should be understood to include those of such embodiments.

(Effects of the Invention) As is clear from the above description, in the X-ray image detector according to the present invention, the X-ray source and the reading optical system are arranged on opposite sides of each other with the X-ray image conversion element interposed therebetween. Since the writing portion and the reading portion can be completely separated from each other, the object to be inspected can be brought as close as possible to the recording surface of the image conversion element and X-rays can be irradiated from the front. In addition, a high resolution image can be obtained,
It is possible to use an X-ray image detector capable of sufficiently discriminating even minute metal wires.

Further, in the present invention, in the optical path of the reading optical system of the X-ray image detector, it is configured such that the X-ray irradiation direction and the optical axis of the imaging system are at a right angle via a reflecting mirror, By disposing a medium that shields X-rays so that the image pickup device portion is shielded from X-rays, a good image with less noise due to X-rays can be obtained.

Furthermore, in the X-ray image detector according to the present invention, a plurality of image conversion elements are used, and these image conversion elements are sequentially moved so that operations such as writing and reading are performed in parallel for each element. Then, there is an advantage that the writing / reading time of one screen can be shortened and the continuous image can be obtained by making it as close to the real-time operation as possible, and the reading optical system can change the visual field range of the read image. By providing the X-ray, the image reading range can be switched, both the entire image and the magnified image can be read arbitrarily, and the X-ray that can utilize both the effective area and the resolution of the image conversion element according to the purpose. It also became possible to use it as an image detector.

Furthermore, if the light source of the reading optical system is a surface emitting light source,
The optical system of the reading light is simplified, and the miniaturization of the X-ray image detector can be advantageously achieved. Furthermore, by providing the control system for controlling the X-ray irradiation amount, By setting the optimum X-ray irradiation amount, a clear image can be easily obtained.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a conventional X-ray image conversion element, and FIG. 2 is a schematic explanatory view of a conventional X-ray image detector using such an image conversion element. FIG. 3 is a schematic explanatory view showing an example of an X-ray image conversion element used in the present invention, and FIG. 4 is an X-ray image detector according to the present invention using such an X-ray image conversion element. FIG. 3 is an explanatory diagram of an arrangement form showing an example. Further, FIG. 5, FIG. 7, FIG. 9 and FIG. 10 are respectively explanatory views of arrangement forms showing other different examples of the X-ray image detector according to the present invention, and FIG. FIG. 8 is an explanatory diagram showing write / read / erase operations for a plurality of X-ray image conversion elements provided on a table, and FIG. 8 is an explanatory diagram showing a lens holder to which a plurality of field lenses are attached. 22: Single crystal plate, 23: Metal thin film electrode 24: Insulating layer, 26: Transparent electrode 28: Power source 30: X-ray image conversion element 32: X-ray source, 34: Object to be inspected 36: Light source, 38: Polarizer 40: Beam splitter 42: Convex lens, 44: Analyzer 46: CCD camera, 48: CCD image sensor 50: Reflector, 52: Shield 54: Rotating table, 56: Field lens 58: Lens holder, 60: Surface emitting light source 62: Half mirror, 64: Convex lens 66: Light measuring device, 68: X-ray irradiation control device 70: X-ray dosimeter

Claims (9)

[Claims] 1. A single crystal plate having an electro-optical effect and a photoconductive effect, and a reflective conductive layer provided on one surface of the single crystal plate, the reflective conductive layer being capable of reflecting light but transmitting X-rays. A light-transmitting insulating layer provided on the other surface of the single crystal plate, and a predetermined number provided on the insulating layer and on the insulating layer and the single crystal plate in cooperation with the reflective conductive layer. X-ray image detector using an X-ray image conversion element having a transparent conductive layer to which an electric field is applied, and X-ray image detector is provided on the side of the image conversion element where the reflective conductive layer is provided.
An X-ray irradiation source is arranged so that an X-ray image can be written in the image conversion element by the X-ray irradiation from the X-ray irradiation source, and on the side of the image conversion element where the transparent conductive layer is provided. A light source for irradiating the image conversion element with predetermined reading light and an optical system for forming an image of the reading light reflected from the image conversion element are arranged and written in the image conversion element. An X-ray image detector characterized in that the X-ray image is read by the light source and the optical system. 2. A reflecting mirror is arranged in the optical path of the optical system, and the X-ray irradiation direction from the X-ray irradiation source and the optical axis of the imaging system are perpendicular to each other. An X-ray image detector according to item (1). 3. An X-ray image detector according to claim 1, wherein a medium capable of blocking X-rays and transmitting read-out light is arranged in the optical path of the optical system. 4. While using a plurality of the image conversion elements,
The writing position of the X-ray image by the X-ray irradiation source, the reading position of the X-ray image by the light source and the optical system, and the erasing position of the X-ray image are made different, and the image conversion elements are moved to make the writing position, The X-ray image detector according to any one of claims (1) to (3), wherein the X-ray image detector is arranged at the read position and the erase position sequentially. 5. The X-ray image detector according to claim 1, wherein the optical system is provided with lens means for changing a visual field range of a read image. 6. The light source is a surface emitting light source (1).
An X-ray image detector according to any one of (5) to (5). 7. X-ray measuring means for measuring an X-ray irradiation dose from the X-ray irradiation source, and X measured by the X-ray measuring means.
The X-ray irradiation control device for controlling the X-ray irradiation time by the X-ray irradiation source on the basis of the radiation irradiation dose, further provided. X-ray image detector. 8. Light measuring means for measuring the intensity of read light from the light source, and X for controlling the X-ray irradiation time by the X-ray irradiation source based on the read light intensity measured by the light measuring means. The X-ray image detector according to any one of claims (1) to (6), further comprising a radiation irradiation control device. 9. A reading light reflected from the image conversion element while vertically irradiating the image conversion element with the reading light from the light source on the side where the transparent conductive layer of the image conversion element is provided. The X-ray image detector according to claim 1, further comprising a convex lens that forms an image of light.