JP2000292876A - Radiograph information reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-speed reading and to make a device compact in a radiograph information reader. SOLUTION: This reader is provided with a surface light source 20 irradiating the entire surface 10a of a stimulable phosphor sheet 10 with stimulating light L1 in a surface state, an area sensor 30 receiving stimulated phosphorescent light L2 emitted from the back surface 10b of the sheet 10, and a condensing optical system 40 constituted by plurally arraying Selfoc(R) lens condensing the light L2 emitted from the back surface 10a of the sheet 10 by each photoelectric conversion element 31 constituting the sensor 30. In the case of reading, the light L2 emitted from the surface 10b is collectively received by the sensor 30, so that the speeding-up of the reading time can be attained, and also a mechanism relatively moving the sheet 10 and the sensor 30 is unnecessary, and the device can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiographic image information reading apparatus, and more particularly to a radiographic image information reading apparatus that reads out stimulated light emitted from a stimulable phosphor sheet to obtain radiographic image information. is there.

[0002]

2. Description of the Related Art When irradiated with radiation, a part of the radiation energy is accumulated, and thereafter, when irradiated with excitation light such as visible light or laser light, a stimulable phosphor that emits stimulating light in accordance with the accumulated radiation energy. (Photostimulable phosphor) is used to temporarily store and record radiation image information of a subject such as a human body on a sheet-like stimulable phosphor sheet formed by laminating a stimulable phosphor on a support. Excitation light such as laser light is deflected and scanned for each pixel to generate stimulated emission light sequentially from each pixel, and the obtained stimulated emission light is photoelectrically sequentially read by photoelectric reading means to obtain an image signal. A radiation image recording / reproducing system that emits erasing light to the stimulable phosphor sheet after reading the image signal to emit radiation energy remaining on the sheet has been widely used in practice.

An image signal obtained by this system is subjected to image processing such as gradation processing and frequency processing suitable for observation and interpretation, and the image signal after these processings is applied as a diagnostic visible image. It is recorded on a film or displayed on a CRT and used for diagnosis by a doctor or the like. On the other hand, the stimulable phosphor sheet from which the residual radiation energy irradiated with the erasing light has been released can again store and record radiation image information, and can be used repeatedly.

Here, in the radiation image information reading apparatus used in the above-mentioned radiation image recording / reproducing system,
From the viewpoints of shortening the reading time of the stimulating light, shortening the size of the apparatus, and reducing the cost, a fluorescent lamp, a cold cathode fluorescent lamp (a cold cathode fluorescent lamp) that irradiates the sheet with the excitation light linearly as an excitation light source. ) Or a line sensor in which a large number of photoelectric conversion elements are arranged along the length direction of a linear portion of a sheet irradiated with excitation light by the line light source as a photoelectric reading unit using a line light source such as an LED array. And a line reading system including scanning means for moving the line light source and the line sensor relative to a sheet in a direction substantially perpendicular to the length direction of the linear portion has been proposed. (JP-A-60-111568, 60-111568)
236354, JP-A-1-101540, etc.).

Further, in order to further shorten the reading time as compared with the line reading type apparatus, an excitation light source for irradiating the sheet with excitation light in a planar manner, and a photostimulated light emitted from the sheet surface are collected. In addition to using a fiber condensing optical system using a fiber bundle or a reduction optical system using a spherical lens, and an area sensor consisting of a large number of photoelectric conversion elements arranged in a plane, a fiber condensing optical system or a reducing optical system There is also proposed an area reading type device in which the stimulated emission light emitted from the device is received several times by an area sensor.

[0006]

However, the line reading system described above requires scanning means for moving the line light source and the line sensor relative to the sheet in a direction substantially perpendicular to the length direction. In addition, the device cannot be downsized. Also, compared to the area reading method,
The reading time is long.

On the other hand, the above-described area reading type apparatus
Although the reading time can be shortened compared to the line reading method, the fiber condensing optical system and the reduction optical system for condensing the photostimulated light emitted from the sheet during reading are large, so a small and thin device must be used. Difficult to achieve.

Further, the conventional area sensor does not have a light receiving area enough to collectively receive stimulated emission light emitted from the image area on the sheet. In order to separate the reading, a mechanical means for relatively moving the two is required, which is an obstacle to shortening the reading time and realizing a small and thin apparatus. .

Further, both the line reading method and the area reading method require means for relatively moving the sheet and the sensor, and there is a limit in bringing the sheet and the optical system close to each other. The light collection efficiency is not always good, which has been a factor in image quality deterioration.

The present invention has been made in view of the above circumstances, and it is possible to obtain an image having an excellent S / N by further increasing the reading speed and improving the use efficiency of weak photostimulated light. It is an object of the present invention to provide a radiation image information reading apparatus capable of realizing a smaller apparatus.

[0011]

SUMMARY OF THE INVENTION A radiation image information reading apparatus according to the present invention collectively receives stimulated emission light emitted from an image area on a stimulable phosphor sheet.
The reading time is further increased, and the apparatus can be downsized. That is, the radiation image information reading apparatus according to the present invention includes a surface light source that irradiates excitation light in a plane onto a stimulable phosphor sheet on which radiation image information is accumulated and recorded, and a sheet corresponding to a portion irradiated on the sheet. An area sensor in which a large number of photoelectric conversion elements are arranged to receive photostimulated light emitted from the back side portion and perform photoelectric conversion, and the photostimulated light emitted from the back side of the sheet to the area. A light-collecting optical system for condensing light for each photoelectric conversion element constituting the sensor, and a reading means for reading the output of each photoelectric conversion element are provided.

The phrase "irradiating the stimulable phosphor sheet on which the radiation image information is stored and recorded with the excitation light in a planar manner" means irradiating the excitation light so as to cover the entire image area on the sheet. The “image area on the sheet” only needs to include at least the area of interest in the image information, and need not necessarily irradiate the entire recorded image area or the entire sheet.

"Condensing stimulated emission light emitted from the back side of the sheet for each photoelectric conversion element constituting the area sensor" means that the image area on the sheet irradiated with the excitation light as described above. Means that the stimulated emission light emitted from the entire area is collectively collected on the light receiving surface of the area sensor. As described above, the “image area on the sheet” may include at least the area of interest in the image information, and need not necessarily include the entire recorded image area or the entire sheet.

The light-collecting optical system used in the radiation image information reading apparatus according to the present invention is, for example, a spherical lens array, as long as it can collectively collect light as described above. However, in order to reduce the size of the device, a refractive index distribution type (GBI
It is desirable to use a lens having a large number of N (Gradient Index) lenses arranged in a plane. The refractive index distribution type lens can be roughly classified into a flat microlens and a selfoc lens (registered trademark; hereinafter abbreviated) (also referred to as a rod lens), and it is particularly preferable to use a selfoc lens.

A selfoc lens is a lens having a parabolic refractive index distribution from the center of thickness of a thick rod-shaped lens to the periphery thereof, and light has a constant period in the longitudinal direction in the thick lens. It travels while meandering, and is configured so that an erect equal-magnification image can be formed by selecting an appropriate length for the meandering cycle.

Further, in the radiation image information reading apparatus according to the present invention, image information on the entire surface of the sheet can be collectively detected irrespective of the size of the region of interest, and the light condensing loss is reduced. It is desirable that both the irradiation area of the excitation light irradiated toward the sheet of the surface light source and the light receiving area of the area sensor be equal to or larger than the area of the sheet. In other words, an area sensor having an area larger than the entire surface of the sheet is arranged close to the back surface of the sheet, and the excitation light is irradiated in a planar manner so as to cover the entire surface of the sheet, and stimulated emission emitted from the entire back surface of the sheet. Light is detected collectively by the area sensor.

Note that an excitation light cut filter (sharp cut filter, band pass filter) that transmits stimulated emission light but does not transmit excitation light is provided between the back surface of the sheet and the sensor. It is preferable to prevent incidence.

Further, as the area sensor of the radiation image information reading apparatus according to the present invention, a square or circular sensor in which a large number of photoelectric conversion elements are arranged in a plane is preferable. For example, amorphous silicon sensor, CC
Although a D sensor, a MOS image sensor, or the like can be used, it is particularly preferable to use a back-illuminated type CCD, and it is more preferable to provide a cooling means for cooling the back-illuminated type CCD.

Here, a back illuminated type CCD
Unlike a front-illuminated CCD that illuminates light from the front, which is generally used in the past, a CC that illuminates light from the back by shaving the back, etc.
D, which is also called back-illuminated, back-illuminated, or back-illuminated CCD.

The front-illuminated CCD has a very low sensitivity in a short wavelength region such as blue light because of the provision of a protective layer of Si or the like.
Has relatively extremely high sensitivity in the high UV to blue light region. In addition, the CCD has a high quantum efficiency, and has higher sensitivity in the visible light range to the infrared range as well as the high UV (ultraviolet) to blue light range than the front-illuminated CCD.

As a cooling means for cooling the back-illuminated type CCD, for example, a cooling means using a Peltier element is preferable.

Further, in the radiation image information reading apparatus according to the present invention, a surface light source comprising a fluorescent lamp, a high pressure sodium lamp, a cold cathode tube, an LED or an organic EL element is used. It is desirable.

Here, the organic EL (also referred to as an organic LED) is a current that emits light by converting recombination energy between electrons and holes (holes) injected into an organic material into light energy. It is an injection type light emitting element. This organic EL can emit a strong light of several hundred thousand candela (luminance of a normal white fluorescent lamp is 1000 to 5000 candela) (can emit high brightness) and has an energy conversion efficiency of 10 lm / W or more. (High luminous efficiency) Being a self-luminous device, besides being able to be driven at a DC low voltage of about 10 V or less, capable of high-speed response on the order of nS, capable of emitting multicolor light from blue to red, and having a viewing angle like a liquid crystal device It has characteristic properties such as an ultra-thin and lightweight device without dependence, and has been noticed and put to practical use as a new electronic device today. In addition, what kind of thing may be used for the element material, the element structure, the manufacturing method, etc. of the organic EL.

The surface light source may be any one that irradiates the stimulable phosphor sheet with the excitation light in a planar manner (area shape). It may be provided with an enlargement mechanism for enlarging the emitted excitation light so that it becomes planar on the irradiation surface of the luminescent phosphor sheet. A large number of fluorescent lamps, high-pressure sodium lamps, cold-cathode tubes, LEDs or organic EL elements are arranged in a plane,
It is desirable to make the emitted excitation light itself planar, because higher illuminance can be obtained than when an enlargement mechanism is provided, and it is not necessary to provide an enlargement mechanism, and the light source can be made compact.

The excitation light emitted from the surface light source may be emitted continuously or may be emitted in a pulse shape in which emission and stop are repeated. From the viewpoint, it is desirable that the light is pulsed light with high output.

The wavelength of the excitation light may be any wavelength at which stimulated emission light can be generated by irradiating the stimulable phosphor sheet. For example, red excitation light is irradiated to generate stimulated emission light. In combination with a sheet to be pressed, the thickness is set to 600 to 1000 nm, more preferably 600 to 700 nm.

The reading means is capable of acquiring an image signal carrying radiation image information recorded on a sheet based on a signal output from each of the photoelectric conversion elements constituting the area sensor. Any one may be used.

[0028]

According to the radiation image information reading apparatus of the present invention, a surface light source for irradiating excitation light in a plane onto substantially the entire surface of a stimulable phosphor sheet, and a light emitted from the back surface of the sheet corresponding to the portion irradiated with the excitation light are provided. And an area sensor for detecting the stimulated emission light emitted, and a condensing optical system for condensing the stimulated emission light emitted from the back of the sheet for each photoelectric conversion element constituting the area sensor. Further, the stimulated emission light emitted from the image area on the sheet can be collectively received, so that the image can be read at a time and the reading time can be further shortened.

Further, since the images can be read at once, a means for relatively moving the sheet and the sensor, in other words, the sheet and the optical system during reading is not required. The light collection efficiency of exhaust light is improved,
An image with a good S / N can be obtained, and the cost can be reduced by downsizing the apparatus and reducing mechanical scanning optical parts.

When a gradient index lens, particularly a selfoc lens, is used as the condensing optical system, a simple optical system can be constructed without the need to adjust the optical axis of the lens and the like. It is easy to manufacture and has a great effect on reducing the cost of the device. Further, the distance between the sheet and the sensor can be reduced, and the apparatus can be made more compact. Further, the light amount and the resolving power can be made uniform in the direction in which the thick lenses are arranged.

When an equal-magnification imaging system is formed by using a spherical lens, there is a problem that the image plane illuminance is reduced as compared with a reduction system. However, when a condensing optical system is formed by a gradient index lens. Is advantageous because such a problem does not occur.

Further, if both the irradiation area of the excitation light applied to the sheet of the surface light source and the light receiving area of the area sensor are equal to or larger than the sheet area, regardless of the size of the region of interest. Thus, image information on the entire surface of the sheet can be detected at a time, and the light-collecting loss is reduced.

Further, if reading is performed using a back-illuminated type CCD having a high quantum efficiency as an area sensor, an image having a larger level can be obtained as compared with a front-illuminated CCD sensor generally used conventionally. A signal can be obtained, and as a result, a high-quality image with a better S / N than before can be obtained. Further, the back illuminated type CCD has higher speed and higher accuracy than the front-illuminated CCD sensor, and can ensure high speed and high accuracy of reading.

The quantum efficiency of the back illuminated type CCD is high over the entire range from ultraviolet to infrared.
Particularly, in the ultraviolet to blue light region, it has a characteristic property that it is extremely high (for example, 50% or more) as compared with the quantum efficiency (approximately zero) of the conventional front-illuminated CCD sensor, and the brightness of the blue light is high. When used in combination with a stimulable phosphor sheet that emits stimulating light, the utilization efficiency of stimulating light is significantly improved,
The effect of high image quality is extremely large.

Further, if the cooling means for cooling the back illuminated type CCD is provided, the dark output can be reduced, and a higher quality image with reduced noise can be obtained.

If a surface light source made of a fluorescent lamp, a high-pressure sodium lamp, or a cold cathode tube is used, the device is inexpensive, easily available, and can be simply constructed.

If a surface light source made of an LED is used, it is easy to obtain and a thin light source can be used, so that a small and thin device can be realized.

Further, when a surface light source made of organic EL is used, a thin light source can be obtained, and the emission light can be reduced as compared with a device using a fluorescent lamp, a cold cathode tube or an LED as a light source. Since the intensity is high and sufficient luminance is obtained, higher excitation energy can be applied to the stimulable phosphor sheet, and as a result, an image having an extremely high S / N can be obtained.

While the laser method is expensive, when a fluorescent light, a high-pressure sodium lamp, or a cold cathode tube, an LED, or an organic EL is used as a surface light source, it is compact, inexpensive, and easy to handle. Can be configured.

Further, when a condensing optical system using a gradient index lens, particularly a selfoc lens, and a surface light source using an LED or an organic EL are combined, an extremely small and thin device can be realized. In addition, since the battery can be driven, a portable cassette in which these and a sheet are accommodated in a case can be configured.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of a radiation image information reading apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing one embodiment of the radiation image information reading apparatus according to the present invention.

This radiation image information reading apparatus uses a stimulable phosphor sheet using a support formed of a stimulable luminescent light transmissive material, and connects a surface light source and an area sensor to different surfaces of the sheet. And a transmission light condensing type configuration in which stimulated emission light emitted from a surface opposite to the sheet surface on which the excitation light is incident is received. That is, as shown in FIG. 1, the front end portion and the rear end portion of the stimulable phosphor sheet 10 (the front end portion and the rear end portion do not have a radiographic image recorded, or even if the radiographic image is recorded, A transport belt 90 that transports the sheet 10 while supporting the sheet 10, a surface light source 20 that irradiates the surface of the sheet 10 with the radiation image information accumulated and recorded with the excitation light L1 in a planar manner, and a surface 10a of the sheet 10 (Hereinafter simply referred to as back surface) 10 on the back surface (surface opposite to the incident surface of excitation light L1) of sheet 10 corresponding to the portion irradiated with
a, an area sensor 30 in which a large number of photoelectric conversion elements 31 are arranged for receiving and receiving photostimulated luminescence light L2 emitted from the light emitting element a, and an area sensor for generating photostimulated light L2 emitted from the back surface 10a of the sheet. Each photoelectric conversion element 3 constituting 30
Selfoc lens array (hereinafter referred to as SLA) as a condensing optical system that condenses light for each light and makes it incident on its light receiving surface
40 and each photoelectric conversion element 3 constituting the area sensor 30
And a reading means 50 for reading an output signal output from the device 1.

The area sensor 30 is mounted on a cooling means 70 using a Peltier element, and is configured to cool the area sensor 30 during operation of the apparatus. Not only the cooling means 70 using the Peltier element but also various known cooling methods such as a heat sink can be used.

An excitation light cut filter 60 for cutting the excitation light L1 mixed with the stimulating light L2 incident on the SLA 40 is arranged between the sheet 10 and the incident surface of the stimulating light L2 of the SLA 40. ing.

The sheet light source 20 is
It is possible to irradiate the area of interest of the sheet 10 at one time so that the area of irradiation of the excitation light L1 applied to the zero surface 10a is equal to or greater than the area of the area of interest (effective image area) of the sheet 10. In order to make it possible, a large number of organic EL elements are arranged in a plane. As the sheet 10, a sheet that emits red excitation light L1 and generates blue stimulating light L2 (for example, a sheet using BFX: Eu or the like as a stimulable phosphor) is used here. The emission wavelength of the EL light emitted from the EL element, that is, the wavelength of the excitation light L1 is set to 600 to 1000 nm, more preferably 600 to 700 nm in consideration of the combination with the sheet 10. Specifically, for example, an organic EL element using a red light emitting material such as a rhodamine dielectric, an oxazine dielectric, or an Eu (III) complex may be used.

The excitation light may be excitation light having a wavelength that matches the excitation wavelength of the stimulable phosphor sheet to be used, and is not limited thereto. For example, the excitation light may be used as a carrier transport layer or a light emitting layer of an organic EL. Anthracene dielectric, perylene dielectric, azomethine zinc complex, N-arylbenzimidazole, beryllium of 5-hydroxy-chromone and S
If c complex, distyryl arylene dielectric, etc. are used,
Since the organic EL can emit blue light, blue light can be used as excitation light.

[0048] Similarly, using metal complexes such as Alq _3, coumarin dielectric, quinacridone dielectric, tris (2,4-Pentajiono) 1,10 phenanthrylethynyl Ro phosphorus terbium, naphthalimide dielectric, coronene dielectric such Then, blue light emitted from the organic EL can be used as excitation light. Furthermore, if a rubrene dielectric is used, yellow light can be used as excitation light. Of course, it is not limited to the materials described above. Note that it is more preferable that the luminous efficiency be improved by using a doping material.

The device structure of this organic EL is generally a DL-
The three basic structures of H, DL-E, and TL are used, but the present invention is not limited to this, and it does not matter whether or not it has a laminated structure. Further, as for the manufacturing method, any method such as a vacuum evaporation method and a casting method may be used.

When the emission wavelength of the EL light emitted from the organic EL element is different from the above, the surface light source 20 and the sheet light are adjusted so that the wavelength of the excitation light L1 is 600 to 1000 nm on the surface 10a of the sheet 10. 10, a wavelength conversion filter 62 is inserted as shown by a dotted line in FIG. For example, when an organic EL element for emitting white light is used, a red color filter may be used as the wavelength conversion filter 62.

The surface light source 20 emits high-output pulsed light for a short time from the viewpoint of reducing the inherent noise during reading.
Irradiate to zero.

On the other hand, the excitation light cut filter 60 cuts the excitation light L1 having a wavelength of 600 to 1000 nm in consideration of the combination with the sheet 10 and transmits the blue stimulated emission light L2 emitted from the sheet 10. A blue optical bandpass filter (for example, B-390 or B-410) is used. The excitation light cut filter 60 is an SLA
It may be arranged between the emission surface of the 40 photostimulated light L2 and the area sensor.

Further, in this apparatus, the monitor means for monitoring the amount of the excitation light L1 emitted from the surface light source 20 and the sheet 10 based on the monitoring result by the monitor means
Modulating means for modulating the light emission intensity of the organic EL so that the light amount of the excitation light L1 on the surface is constant is provided, and when the fluctuation in the light amount is detected by the monitor means, the surface light source 20 is constituted by the modulating means. The light emission power of the organic EL may be made constant.

The area sensor 30 is provided on the back surface 1 of the sheet 10.
0b, and the stimulating light L passed through the SLA 40
2 (e.g., 1000 or more) are arranged in a plane so that all of the light-receiving elements 2 can be received at one time, that is, the total light-receiving area is equal to or larger than the area of the region of interest of the sheet 10. It is configured. This area sensor 3
0 is a back illuminated type CCD (hereinafter B
T-CCD) is used. As this BT-CCD, for example, S7031 (1) manufactured by Hamamatsu Photonics KK
(Electronic cooling type).

FIG. 2 shows S70 manufactured by Hamamatsu Photonics Co., Ltd.
FIG. 31 is a block diagram of the photoelectric conversion element 31. Each of the photoelectric conversion elements 31 constituting S7031 has a light receiving surface having a size of about 24 μm × 24 μm. FIG. 3 is a diagram showing the spectral sensitivity characteristics of S7031, and shows typical spectral sensitivity characteristics of the BT-CCD. For comparison, the spectral sensitivity characteristics of a conventional front-illuminated CCD are also shown. As is clear from the figure, the quantum efficiency of the BT-CCD is higher over the entire range from the ultraviolet to infrared regions than the quantum efficiency of the conventional front-illuminated CCD sensor, and the conventional front-illuminated CC sensor has a higher quantum efficiency.
An image signal with a higher level can be obtained as compared with the D sensor, and a high-quality image with a better S / N than before can be obtained.

In the ultraviolet to blue light region, the front-illuminated CCD sensor has a quantum efficiency of almost zero, whereas the BT-CCD has a quantum efficiency of about 50% or more, and the ratio is extremely large. Therefore, by applying the BT-CCD to the line sensor 20, the use efficiency of the stimulated emission light can be significantly improved when used in combination with the stimulable phosphor sheet that emits blue stimulated emission light. Great effect of image quality.

The line sensor 20 is configured to be cooled by cooling means (not shown) to suppress thermal noise. FIG. 4 is a diagram showing temperature characteristics of dark output (log scale). As is clear from the figure, BT-
By cooling the CCD, the dark output can be reduced, and a high-quality image with reduced noise can be obtained. Here, the set temperature of the cooling means is set to about −20 °, and the dark output is about 10 (e / pixel / sec).

The target of the detection limit of the BT-CCD in which the thermal noise is suppressed by this cooling is 20 (electron / pi
xel). CCD photoelectric conversion efficiency = 0.995, 40
Since the quantum efficiency at 0 nm = 0.6, the detection limit photon number of the BT-CCD = 34 (photon / pixel). Although the detection limit of the BT-CCD is higher than that of the photomultiplier, the level is not greatly different from the digit. Therefore, even when the BT-CCD is used, it is possible to obtain the same image quality as an apparatus using the photomultiplier.

When a photodiode array with an amplifier is used, the detection limit of the photodiode array with an amplifier is, for example, 1250 (electr
on / pixel). Quantum efficiency at 400 nm =
0.57, and assuming that the photoelectric conversion efficiency is almost 1, the detection limit number of photons of the photodiode array with the amplifier is about 2
000 (photon / pixel). However, this value also includes an increase in the amount of noise due to arraying. Therefore, when a photodiode array with an amplifier is used as a light receiving element, the detection limit value is two to three orders of magnitude lower than that of a photomultiplier, and the same image quality as an apparatus using a photomultiplier cannot be obtained. In the case of photomulti, 5
6.4 photons emitted from a sheet of 0 μm square pixels were detected.

FIG. 5 shows an SLA4 used as a condensing optical system.
FIG. 5A is a perspective view, and FIG. 5B is a view showing a relationship between an outer diameter dimension and an optical parameter.

As shown in FIG. 5A, the SLA 40
A large number of rod-shaped thick lenses 41 are regularly and precisely arranged between the frames 43 such that the light incident surface 40a and the light exit surface 40b are planar. The space between the thick lenses 41 is filled with a black silicone resin 42 to remove flare light.
The frame 43 has a glass cloth base epoxy resin black laminate (FR) having substantially the same characteristics as the thermal expansion of the thick lens 41.
By using P), the thermal strain on the lens 42 is reduced and the strength of the SLA 40 is increased.

Each thick lens 41 is a gradient index lens having a parabolic refractive index distribution from the center to the periphery of the thick lens, and light has a constant period in the thick lens 41 in the longitudinal direction. It is configured to be able to form an erect equal-magnification image at a working distance lo shown in FIG. 5B.

Sheet 10, SLA 40 and Sensor 30
Forms an image of the emission area of the photostimulated emission light L2 on the back surface 10b of the sheet 10 in a one-to-one size on the light receiving surface of the sensor 30, that is, can form an erect equal-size image. The back surface 10b of the sheet 10 and the incident surface 4 of the SLA 40
0a and the distance between the light exit surface 40b of the SLA 40 and the light receiving surface of the sensor 30 are respectively SLA 40
Are arranged so as to be equal to the working distance lo. As a result, the vertical length of 24 μm ×
The stimulated emission light L2 emitted from a portion having a width of about 24 μm and corresponding to the accumulated and recorded radiation image information is vertically
The light can be incident on each photoelectric conversion element 31 having a light receiving surface having a size of about mx 24 μm in width.

Next, the operation of the radiation image information reading apparatus of this embodiment will be described.

First, the sheet 10 is supported on the transport belt 90 and moved from the erasing zone to the reading zone. As shown in FIG.
The sheet 10 is set at a position opposite to the above.

Next, the excitation light L 1 is emitted from the surface light source 20 to the surface 10 a of the sheet 10. Here sheet 10
Is emitted from an organic EL capable of emitting light with high luminance, and has higher excitation energy than fluorescence emitted from a fluorescent lamp or light emitted from an LED.
Therefore, the stimulable phosphor of the sheet 10 can be sufficiently excited, and as a result, the stimulable phosphor emits blue stimulable luminescence light L2 having a high luminous intensity according to the radiation image information stored and recorded. Is emitted from the back surface 10b of the sheet 10.

The stimulated emission light L 2 emitted from the back surface 10 b of the sheet 10 is condensed by the SLA 40 on the light receiving surface of each photoelectric conversion element 31 constituting the area sensor 30. At this time, the excitation light L1 transmitted through the sheet 10 is cut by the excitation light cut filter 60.

The stimulated emission light L that has passed through the SLA 40
2 is received by a number of photoelectric conversion elements 31 constituting the area sensor 30 and is converted into image signals Q by photoelectric conversion. These analog image signals Q obtained by photoelectric conversion are input to the reading means 50, digitized by an A / D converter, subjected to predetermined signal processing, and output to an image processing device (not shown) or the like. Is done.

The image signal Q obtained from the area sensor 30 in this manner is read by using a back-illuminated type CCD so as to read the blue stimulable light L2 emitted from the stimulable phosphor sheet 10. Compared with the case of using a front-illuminated CCD,
Is significantly improved, and an image with extremely good S / N can be obtained.

Further, since it is based on the stimulated emission light L2 excited by the excitation light L1 having a high excitation energy,
Compared to the image signal based on the fluorescent light emitted from the fluorescent lamp or the stimulated emission light excited by the light emitted from the LED,
An image having a high S / N can be obtained.

As described above, according to the radiation image information reading apparatus of the above embodiment, the sheet 10 and the area sensor 30
And the back illuminated type C can be realized, in which a high-speed reading apparatus capable of acquiring an image of the entire sheet 10 at once in a short time without realizing relative movement of
By using a combination of a CD area sensor and a surface light source using an organic EL, a small, thin, and compact device capable of obtaining an image with extremely good S / N can be realized.

Although the preferred embodiment of the radiation image information reading apparatus according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes can be made unless the gist of the invention is changed. It is possible.

For example, in the above embodiment, a condensing optical system having a large number of selfoc lenses arranged in a plane is used. For example, a condensing optical system having a large number of flat microlenses arranged in a plane is used. An optical system may be used.

In the above embodiment, a surface light source having a large number of organic EL elements arranged in a plane is used. A small and thin device can be realized by using a surface light source composed of

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of a radiation image information reading apparatus according to the present invention.

FIG. 2 is a block diagram of a back-illuminated type CCD used in the radiation image information reading apparatus shown in FIG. 1;

FIG. 3 is a diagram showing typical spectral sensitivity characteristics of a back-illuminated type CCD.

FIG. 4 is a diagram showing a temperature characteristic of a typical dark output of a back-illuminated type CCD.

5A is a perspective view showing details of a selfoc lens used in the radiation image information reading apparatus shown in FIG. 1, and FIG. 5B is a diagram showing a relationship between an outer diameter of the selfoc lens and optical parameters; )

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Storage phosphor sheet 20 Surface light source 30 Area sensor 40 Selfoc lens array (SLA) as a condensing optical system 50 Reading means 60 Excitation light cut filter 62 Wavelength conversion filter L1 Excitation light L2 Stimulated emission light

Claims (8)

[Claims] 1. A surface light source for irradiating excitation light in a plane onto a stimulable phosphor sheet on which radiation image information is stored and recorded, and light is emitted from a portion on the back side of the sheet corresponding to a portion irradiated on the sheet. An area sensor in which a large number of photoelectric conversion elements are arranged to receive the photostimulated light emitted and perform photoelectric conversion, and the photostimulated light emitted from the back side of the sheet constitutes the area sensor. A radiation image information reading apparatus comprising: a light-collecting optical system for collecting light for each photoelectric conversion element; and reading means for reading an output of each of the photoelectric conversion elements constituting the area sensor. 2. The radiation image information reading apparatus according to claim 1, wherein the light-collecting optical system comprises a gradient index lens. 3. The sheet according to claim 1, wherein an irradiation area of the excitation light emitted from the surface light source toward the sheet and a light receiving area of the area sensor are both equal to or larger than the area of the sheet. 2. The radiation image information reading device according to item 2. 4. The radiation image information reading apparatus according to claim 1, wherein the area sensor is a back-illuminated type CCD. 5. The back illuminated type CCD
The radiation image information reading apparatus according to claim 4, further comprising cooling means for cooling the radiation image information. 6. The radiation image information reading apparatus according to claim 1, wherein the surface light source comprises a fluorescent lamp, a high-pressure sodium lamp, or a cold cathode tube. 7. The radiation image information reading apparatus according to claim 1, wherein the surface light source is formed of an LED. 8. The radiation image information reading apparatus according to claim 1, wherein the surface light source is formed of an organic EL element.