JPH05128173A - Radiation image reader - Google Patents

Abstract

PURPOSE:To provide a small-sized and low-cost radiation image reader having high light collection efficiency of light collector and constant light collection efficiency. CONSTITUTION:The device converts stimulated phosphorescent light emitted by a stimulable phosphor panel 31 which absorbs radiated radiation energy and stores it as an latent image when excitation light radiates the panel into an electric signal and obtains image information. A photomultipliter tube 3 converting the stimulated phosphorescent light into the electric signal, and a light collection means 4 whose inside is hollow and surrounded with mirror walls, the area of whose aperture through which the stimulated phosphorescent light is made lincident is smaller than the area of photoelectrical surface of the photomultiplier tube 3, and which collects the stimulated phosphorescent light and leads it to the photomultiplier tube 3, are provided.

Description

Detailed Description of the Invention

[0001]

10. The optical filter is composed of a plurality of divided optical filters.
Radiation image reading device.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates stimulated emission light corresponding to radiation image information by scanning an excitation light beam on a phosphor plate or sheet that stores radiation image information, and this stimulated emission light is generated. The present invention relates to a radiation image information reading device that photoelectrically converts light and reads radiation image information as an electric signal. In particular, the present invention relates to a method of efficiently stimulating stimulated emission light and condensing it with a uniform condensing efficiency to perform photoelectric conversion.

Radiation images such as X-ray images are widely used for disease diagnosis and the like. As a means for obtaining an X-ray image, X-rays that have passed through the subject are irradiated to the phosphor layer (fluorescent screen), thereby generating visible light, and this visible light is converted into a film using silver salt. Irradiated and developed,
So-called radiography has been conventionally used.

On the other hand, as a high-sensitivity and high-resolution X-ray imaging system, instead of the conventional method of recording a two-dimensional image of radiation indirectly or directly on a film coated with a silver salt photosensitizer, a stimulable fluorescence is used. The method of using the body is beginning to be used. Such a method is described in detail in US Pat. No. 3,859,527 as a basic method.

The phosphor used in this system is a so-called accumulative phosphor that accumulates energy in the phosphor crystal when it receives the energy of radiation such as X-rays. It is stable and retained for a while or for a long time. When the phosphor in this state is irradiated with the first light that acts as the excitation light, the stimulated emission light having the intensity corresponding to the stored energy is emitted as the second light. At this time, the first light is not limited to visible light, and light having a wide wavelength range from infrared to ultraviolet is used. However, the choice depends on the phosphor material used. The second light also has various types from infrared rays to ultraviolet rays. The difference also depends on the phosphor material used.

Utilizing the characteristics of the stimulable phosphor, an X-ray imaging system for obtaining radiation image information by irradiating and recording radiation transmitted through a subject such as a human body on the stimulable phosphor has been put into practical use. Specifically, a stimulable phosphor plate or sheet that stores and records X-ray information of a subject is scanned with excitation light such as laser light to generate stimulated emission light, and this light is collected and received. Then, an electric signal proportional to the intensity of the accumulated radiation is obtained by converting it into an electric signal by a photoelectric converter. Thereafter, this electric signal is subjected to image processing and printed on a silver salt film or displayed on a cathode ray tube CRT or the like to obtain a visualized radiation image.

Therefore, in such a system S /
In order to obtain an image with good N, it is important to use a condenser that efficiently and uniformly collects the generated stimulated emission light and guides it to the photoelectric converter. Since the generated stimulated emission light has no directivity and diverges into the entire space, it can be collected with a solid angle as wide as possible as a condenser, and there is no attenuation or return light inside the condenser. There is a demand for a radiographic image reading apparatus with low loss.

[0008]

2. Description of the Related Art FIG. 10 is a block diagram of a radiation image reading apparatus showing a conventional example. The laser beam emitted from the excitation light source 34 is scanned in the main scanning direction (horizontal direction on the paper surface of the figure) by the scanner 35 composed of a galvanometer or the like. Further, by moving the stimulable fluorescent plate 31 in a direction orthogonal to the main scanning direction by the precision fine movement table 37, it is possible to scan the entire surface of the stimulable fluorescent plate 31 with the excitation light. Laser beam 1
The stimulated emission light generated by scanning is condensed by a condenser 38 in which a large number of optical fibers are bundled, and is guided to a photoelectric converter 39. At this time, between the condenser 38 and the photoelectric converter 39,
A filter (not shown) that does not transmit light having the wavelength of the excitation light laser but transmits light having the wavelength of stimulated emission light is installed.
The stimulated emission light selectively extracted by this filter is converted into an electric signal by the photoelectric converter 39, and the first stage amplifier 50
Is amplified to a signal level optimum for the A / D converter 51. The image data converted from an analog signal to a digital signal by the A / D converter 51 is stored in the image memory 52, subjected to image processing later, and output on a CRT (not shown) or as a hard copy.

FIG. 11 is a diagram showing a conventional collector. Conventionally, as means for collecting the stimulated emission light and guiding it to the photoelectric converter 39, a so-called bundle-type light collector in which a large number of plastic fibers or glass fibers are bundled, as shown in FIG. ─ 11396, Japanese Examined Patent Publication 56 ─ 11397
A so-called light guide sheet type concentrator, in which a plastic plate made of acrylic or the like is bent, was used as shown in Fig. 11 (b) of Fig.

Each of these condensers 38 has a shape for guiding the stimulated emission light linearly generated on the scanning line to one photoelectric converter 39 having a circular photoelectric surface.

[0011]

The first problem with such a conventional condenser 38 is that it has a low efficiency of collecting stimulated emission light. In conventional bundle-type concentrators, the solid angle that can be collected is determined by the numerical aperture of the plastic fiber or glass fiber used. Generally, plastic fibers and multi-component glass fibers have a larger numerical aperture than quartz fibers, but on the other hand, they have a large attenuation rate for the light of the wavelength of stimulated emission light, and the total light collection is I couldn't hope to improve efficiency. In addition, the light guide sheet type light collector has a larger solid angle than the bundle type light collector, but since acryl is the medium for transmitting the stimulated emission light, the stimulable phosphor plate is used. When the stimulated emission light generated from 31 propagates in the air and enters the condenser 38,
It was not possible to achieve the ideal light collection efficiency because reflection loss occurred due to the difference in the refractive index between air and acrylic, or it was attenuated during propagation.

Next, the second problem of the conventional condenser 38 is as follows.
This means that there are large variations in the light collection efficiency. In the bundle type concentrator, it is caused by the arrangement of many fibers and the dispersion of the transmittance. In the light guide sheet type concentrator, it is caused by the stress when the acrylic is bent and the defects inside and on the acrylic plate. However, there is a problem that the light collection efficiency varies greatly depending on the location.

Next, the third problem of the conventional condenser 38 is as follows.
That is, a collecting mirror is required. The stimulated emission light is emitted to the entire space including the up and down direction of the stimulable phosphor plate 31, centering on the point irradiated with the excitation light. Regarding the stimulated emission light traveling to the lower surface (back side) of the stimulable phosphor plate 31, a method has been devised in which it is effectively used by reflecting it to the front side with a reflective film or the like provided on the back surface of the stimulable phosphor plate 31. However, since it is not the gist of the present invention, it will not be described in detail. Focusing only on the stimulated emission light radiated on the surface, since the above-mentioned conventional condenser 38 is usually provided only on one side of the scanning line, it is radiated on one side where the condenser 38 is not installed. The stimulated emission light thus generated cannot be collected. In order to solve this problem, conventionally, the mirror 61 (see FIG.
(Refer to FIG. 4), and the stimulated emission light reflected by the mirror 61 is directed to the condenser 38 to improve the light collection efficiency. However, the mirror for directing the stimulated emission light emitted at all angles to the condenser 38 is expensive because high processing accuracy is required, which leads to cost increase and time adjustment for position adjustment. There was a problem that it was necessary.

The present invention provides a radiation image reader having a high light-collecting efficiency of the light collector, a small light-collecting efficiency variation depending on the position of the light collector, and a small light collector. To aim.

[0015]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, 31 is a stimulable phosphor plate that absorbs the emitted radiation energy and accumulates it as a latent image, and emits stimulated emission light when irradiated with excitation light. 3 shows the stimulated emission light. The photomultiplier tube 4 for converting into an electric signal is hollow, the inner surface of which is surrounded by a mirror-like wall, and the photocathode area of the photomultiplier tube 3 is the opening of the portion where the photostimulated luminescent light enters. It is a condensing means having a structure of not less than the area and condensing the stimulated emission light to guide it to the photomultiplier tube 3.

[0016]

[Function] A radiation image reading device that absorbs radiation energy and converts the stimulated emission light emitted by irradiating the stimulable phosphor plate 31 accumulated as a latent image with excitation light into an electric signal to obtain image information In the device, the condensing means 4 is hollow, the inner surface of which is surrounded by walls of mirror surfaces, and the area of the photocathode of the photomultiplier tube 3 is equal to or larger than the area of the opening where the stimulated emission light is incident. And collects the stimulated emission light and guides it to the photomultiplier tube 3, and the photomultiplier tube 3 converts the stimulated emission light into an electric signal. Therefore, the stimulated emission light is collected by the light collecting means 4.
Since air is transmitted through the inside as a medium, the optical interface on the incident surface of the light collecting means 4 is eliminated. Further, since the inner surface of the wall surface of the light collecting means 4 is a mirror surface having a constant reflectance regardless of the angle, incident stimulated emission light is not emitted to the outside of the light collecting means 4. Furthermore, since the wall surface has a structure that gradually expands from the entrance to the photomultiplier tube 3, the incident photostimulable light returns to the entrance while repeating reflection, and does not reach the photomultiplier tube 3. Does not occur.

[0017]

2A and 2B are structural views of a condenser according to a first embodiment of the present invention. FIG. 2A is a perspective view and FIG. 2B is an exploded view. FIG. 3 is a configuration diagram of a condenser and a photoelectric converter according to the first embodiment of the present invention, showing a plan view and a side view thereof. Regarding FIG. 2, the present applicant filed Japanese Patent Application No. 2-4079.
It was filed as No. 35 (filed on December 27, 1990).

The collector of the present invention is the same as the conventional collector 38 described above.
It was invented to solve one of the problems, and the basic shape is, as shown in FIG. 2 and FIG. 3, the inner surface of the upper wall surface 41, the side wall surface 42 and the lower wall surface 43 of the condenser 4a is mirror-finished. It is composed of a plate of metal, glass, resin, or the like, and has a structure in which the wall surface gradually expands from the entrance 45 toward the photoelectric converter 3a or 3b. That is, the area of the exit port 46 is larger than the area of the entrance port 45 of the condenser 4a, and the exit port is determined by the length of the entrance port 45 in the scanning direction and the length in the direction orthogonal to the scanning direction.
The length of 46 in the scanning direction and the length in the direction orthogonal to the scanning direction are longer. Therefore, the photoelectric converter 3a or 3b arranged closely to the emission port 46 is a single photoelectric converter 3b having a photoelectric surface area larger than that of the emission port 46, or the total area of the photoelectric surfaces is the emission port. It is composed of a plurality of photoelectric converters 3a having an area of 46 or more.

By using air as the medium for transmitting the stimulated emission light inside the condenser 4a, the optical interface on the incident surface of the condenser 4a is eliminated, and the stimulated emission light is increased even if the incident angle becomes large. Are made to enter the inside of the light collector 4a. In order to prevent the incident stimulated emission light from being emitted to the outside of the condenser 4a, the inner surface of the wall surface of the condenser 4a is made a mirror surface having a constant reflectance regardless of the angle, and the incident stimulated emission light is also used. While the light is repeatedly reflected, it returns to the entrance 41, and the photoelectric converter 3a or 3b
In order to prevent the situation where the wall surface is not reached, the structure is such that the wall surface gradually expands from the entrance 45 toward the photoelectric converter 3a or 3b. By configuring the condenser 4a in this way, it was possible to improve the conventional first problem of the condensing efficiency.

Further, in the concentrator 4a of the present invention, since the transmission medium is air, the second problem of the conventional example is that the concentration efficiency varies due to defects and non-uniformity in the transmission medium. do not do.

FIG. 4 is a diagram for explaining the operation of the condenser according to the first embodiment of the present invention. The stimulated emission light radiated on one side where the condenser 4a is not installed is the condenser for the scanning line.
It is reflected by a mirror 61 installed at a position opposite to 4a,
The light collection efficiency is improved by directing it toward the light collector 4a.

Further, the condenser 7a according to the second embodiment of the present invention.
According to the mirror of FIG.
It becomes possible to eliminate 61. FIG. 5 is a diagram for explaining the operation of the condenser of the second embodiment of the present invention.

In FIG. 5, the reflector 74 is the mirror 61 of FIG.
It has the same function as and improves the light collection efficiency. FIG. 6 is a structural diagram of a condenser according to a second embodiment of the present invention, which is shown in FIG.
Shows a perspective view and FIG. 6 (b) shows an exploded view.

In FIG. 6 (b), the condenser 7a is provided with a slit 77 for passing the excitation light in a part thereof, and further, at the position where the mirror 61 is installed in FIG. A reflecting plate 74 made of the same material as is provided.

As shown in FIG. 6 (b), the condenser 7a is a combination of five metal plates whose inner surfaces are mirror-finished, and the entrance 75 for stimulated emission light has a long side length. Is about 360 m
m, the short side is a rectangle of 1 to 30 mm. The exit port 76 is larger than the entrance port on both the long and short sides and is 400 m
m, 80 mm. The photoelectric converter 3a has a photoelectric surface of 100 ×
Four 80 mm rectangles are arranged in the scanning line direction.
Although FIG. 6 shows a case where four photoelectric converters 3a are arranged, the number of arranged photoelectric converters 3a can be changed according to the size of the entrance 75 to accommodate various sizes of photostimulable fluorescent plates.

Further, the upper wall surface 71 is provided with a slit 77 having a size of about 300 μm × 360 mm for allowing laser light to pass therethrough. Each of the wall surfaces 71-73 made of a metal plate is configured so as to satisfy the angle shown in FIG.

FIG. 7 is a sectional view of a condenser according to the second embodiment of the present invention. In FIG. 7, the angle ∠ABO formed by the reflection plate 74 and the surface of the stimulable phosphor plate 31 is θ2, the angle ∠CAO formed by the upper wall surface 71 and the scanning line is θ1, and the upper wall surface 71 and the surface of the stimulable phosphor plate 31. If the angle ∠CGB formed by θ3 and the angle between the lower wall surface 73 and the surface of the stimulable phosphor plate 31 ∠FED are θ4, then θ2 ≧ 90 ° and ∠AOB from the light emission point O
The stimulated emission light emitted to is reflected by the reflector 74, is entirely taken into the inside of the condenser 7a, and does not return to the surface of the stimulable phosphor plate 31.

By setting θ1 ≧ 90 ° and θ4 ≦ θ3, all the stimulated emission light emitted from the light emitting point O to other than ∠AOB is taken into the inside of the condenser 7a and reflected. While repeating the above, it reaches the photocathode of the photoelectric converter 3a or 3b without returning to the surface of the stimulable phosphor plate 31.

Although FIG. 7 has been described with a two-dimensional plane for simplification of the description, even if the stimulated emission light is emitted at a certain angle with respect to the paper surface, as shown in FIG. Has a structure that spreads from the entrance 75 toward the photoelectric converter 3a or 3b, and thus reaches the photoelectric surface of the photoelectric converter 3a or 3b, and the surface of the stimulable phosphor plate 31 is reached while repeating reflection. Never return to.

FIG. 8 is a constitutional view of a condenser and a photoelectric converter according to a second embodiment of the present invention, showing a plan view and a side view thereof. As can be seen from FIG. 8 (a), the concentrator 7a according to the present invention has an entrance opening in both the thickness direction and the width direction.
Since it has a shape that widens from 75 to the exit 76, the stimulated emission light once taken in from the entrance 75 repeats total reflection on the inner surface of the condenser 7a, regardless of the incident angle.
All reach the photoelectric surface of the photoelectric converter 3a. Also, collector 7a
Since the inside of the air is air, there is no optical interface at the entrance 75, and there is no restriction on the light collection solid angle due to the refractive index of the transmission medium of the light collector 7a. Further, as shown in FIG. 8B, one photoelectric converter 3b having a large-area photoelectric surface may be used instead of the plurality of photoelectric converters 3a.

FIG. 9 is a system configuration diagram of a radiation image reading apparatus showing an embodiment of the present invention, in which a radiation image reading using the condenser 7a and the photoelectric converter 3a of the second embodiment of the present invention. Shows the device.

A semiconductor laser having a wavelength of 780 nm is used as the excitation light source 34, and the laser beam is scanned by the scanner 35 composed of a galvanometer on the photostimulable phosphor plate 31 in the main scanning direction through the slit 77 of the condenser 7a. To do. Further, by moving the stimulable phosphor plate 31 in the direction perpendicular to the main scanning direction by the precision fine movement table 37, it is possible to scan the entire surface of the stimulable phosphor plate 31 with the excitation light. The stimulated emission light generated by one scanning of the laser beam is condensed by the condenser 7a and guided to the photoelectric converter 3a. Light collector 7a and photoelectric converter
A filter (not shown) that does not transmit light having the wavelength of the excitation light laser but transmits light having the wavelength of stimulated emission light is provided between 3a. The stimulated emission light selectively extracted by this filter is simultaneously converted into an electric signal by the four photoelectric converters 3a, and the output signals from the four photoelectric converters 3a are added by the signal adder 53. It The added signal is amplified by the first-stage amplifier 50 to an optimum signal level for the A / D converter 51, stored in the image memory 52, and subjected to image processing later, C
It is output on RT (not shown) or as a hard copy.

In the present embodiment, the case where the wall surface of the condenser is formed by using the metal plate has been described, but the same effect can be obtained by using other than the metal plate, for example, a glass plate, a plate of resin such as acrylic, etc. A reflective surface may be formed on the surface of the substrate by using a thin film forming technique such as plating, vacuum deposition, sputtering, or ion plating. When forming the reflective thin film on the surface of a metal plate, a glass plate, or a resin plate such as acrylic resin, a dielectric such as ZnS or Na ₃ AlF ₆ or
And by forming a so-called dichroic mirror by stacking multiple metal thin films, the reflectance at the wavelength of stimulated fluorescence is increased,
In addition, the reflectance of laser light can be reduced.

[0034]

As described above, according to the present invention, since the concentrator has a large condensing solid angle and high transmission efficiency,
The stimulated emission light can be efficiently guided to the photoelectric converter, and S
An image with a good / N can be obtained. Further, since the transmission medium is air, and the stimulated emission light from one point is received by a plurality of (large area) photocathodes, the variation of the light collection efficiency due to the location caused by the variation of the medium and the photocathodes. Can be eliminated and a uniform image can be obtained. In addition, by eliminating the mirror that was required to improve the light collection efficiency, it is possible to reduce the cost and size of the device and eliminate the time required to adjust the mirror.

[Brief description of drawings]

FIG. 1 is a block diagram of the principle of the present invention.

FIG. 2 is a structural diagram of a concentrator according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a condenser and a photoelectric converter according to a first embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of the light collector according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation of the light collector according to the second embodiment of the present invention.

FIG. 6 is a structural diagram of a concentrator according to a second embodiment of the present invention.

FIG. 7 is a sectional view of a concentrator according to a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a condenser and a photoelectric converter according to a second embodiment of the present invention.

FIG. 9 is a system configuration diagram of a radiation image reading apparatus showing an embodiment of the present invention.

FIG. 10 is a configuration diagram of a radiation image reading apparatus showing a conventional example.

FIG. 11 is a diagram showing a conventional concentrator.

[Explanation of symbols]

 3 Photomultiplier tube 4 Condensing means 31 Accumulative phosphor plate 34 Excitation light source 35 Scanner 36 fθ lens 37 Precision movement table 38, 4a, 7a Concentrator 39 Photoelectric converter 41, 71 Upper wall surface 42, 72 Side wall surface 43,73 Lower wall 45,75 Entrance 46,76 Exit 50 First stage amplifier 51 A / D converter 52 Image memory 53 Current adder 61 Mirror 74 Reflector 77 Slit

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[Procedure amendment]

[Submission date] November 9, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Added

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates stimulated emission light corresponding to radiation image information by scanning an excitation light beam on a phosphor plate or sheet that stores radiation image information, and this stimulated emission light is generated. The present invention relates to a radiation image information reading device that photoelectrically converts light and reads radiation image information as an electric signal. In particular, the present invention relates to a method of efficiently stimulating stimulated emission light and condensing it with a uniform condensing efficiency to perform photoelectric conversion.

Radiation images such as X-ray images are widely used for disease diagnosis and the like. As a means for obtaining an X-ray image, X-rays that have passed through the subject are irradiated to the phosphor layer (fluorescent screen), thereby generating visible light, and this visible light is converted into a film using silver salt. Irradiated and developed,
So-called radiography has been conventionally used.

On the other hand, as a high-sensitivity and high-resolution X-ray imaging system, instead of the conventional method of recording a two-dimensional image of radiation indirectly or directly on a film coated with a silver salt photosensitizer, a stimulable fluorescence is used. The method of using the body is beginning to be used. Such a method is described in detail in US Pat. No. 3,859,527 as a basic method.

The phosphor used in this system is a so-called accumulative phosphor that accumulates energy in the phosphor crystal when it receives the energy of radiation such as X-rays. It is stable and retained for a while or for a long time. When the phosphor in this state is irradiated with the first light that acts as the excitation light, the stimulated emission light having the intensity corresponding to the stored energy is emitted as the second light. At this time, the first light is not limited to visible light, and light having a wide wavelength range from infrared to ultraviolet is used. However, the choice depends on the phosphor material used. The second light also has various types from infrared rays to ultraviolet rays. The difference also depends on the phosphor material used.

An X-ray imaging system for obtaining radiation image information by utilizing the characteristics of the stimulable phosphor to irradiate and record radiation transmitted through an object such as a human body on the stimulable phosphor has been put into practical use. Specifically, a stimulable phosphor plate or sheet that stores and records X-ray information of a subject is scanned with excitation light such as laser light to generate stimulated emission light, and this light is collected and received. Then, an electric signal proportional to the intensity of the accumulated radiation is obtained by converting it into an electric signal by a photoelectric converter. Thereafter, this electric signal is subjected to image processing and printed on a silver salt film or displayed on a cathode ray tube CRT or the like to obtain a visualized radiation image.

Therefore, in such a system, S /
In order to obtain an image with good N, it is important to use a condenser that efficiently and uniformly collects the generated stimulated emission light and guides it to the photoelectric converter. Since the generated stimulated emission light has no directivity and diverges into the entire space, it can be collected with a solid angle as wide as possible as a condenser, and there is no attenuation or return light inside the condenser. There is a demand for a radiographic image reading apparatus with low loss.

[0007]

2. Description of the Related Art FIG. 10 is a block diagram of a radiation image reading apparatus showing a conventional example. The laser beam emitted from the excitation light source 34 is scanned in the main scanning direction (horizontal direction on the paper surface of the figure) by the scanner 35 composed of a galvanometer or the like. Further, by moving the stimulable fluorescent plate 31 in a direction orthogonal to the main scanning direction by the precision fine movement table 37, it is possible to scan the entire surface of the stimulable fluorescent plate 31 with the excitation light. Laser beam 1
The stimulated emission light generated by scanning is condensed by a condenser 38 in which a large number of optical fibers are bundled, and is guided to a photoelectric converter 39. At this time, between the condenser 38 and the photoelectric converter 39,
A filter (not shown) that does not transmit light having the wavelength of the excitation light laser but transmits light having the wavelength of stimulated emission light is installed.
The stimulated emission light selectively extracted by this filter is converted into an electric signal by the photoelectric converter 39, and the first stage amplifier 50
Is amplified to a signal level optimum for the A / D converter 51. The image data converted from an analog signal to a digital signal by the A / D converter 51 is stored in the image memory 52, subjected to image processing later, and output on a CRT (not shown) or as a hard copy.

FIG. 11 is a diagram showing a conventional collector. Conventionally, as means for collecting the stimulated emission light and guiding it to the photoelectric converter 39, a so-called bundle-type light collector in which a large number of plastic fibers or glass fibers are bundled, as shown in FIG. ─ 11396, Japanese Examined Patent Publication 56 ─ 11397
A so-called light guide sheet type concentrator, in which a plastic plate made of acrylic or the like is bent, was used as shown in Fig. 11 (b) of Fig.

These condensers 38 have a shape for guiding the stimulated emission light linearly generated on the scanning line to one photoelectric converter 39 having a circular photoelectric surface.

[0010]

The first problem with such a conventional condenser 38 is that it has a low efficiency of collecting stimulated emission light. In conventional bundle-type concentrators, the solid angle that can be collected is determined by the numerical aperture of the plastic fiber or glass fiber used. Generally, plastic fibers and multi-component glass fibers have a larger numerical aperture than quartz fibers, but on the other hand, they have a large attenuation rate for the light of the wavelength of stimulated emission light, and the total light collection is I couldn't hope to improve efficiency. In addition, the light guide sheet type light collector has a larger solid angle than the bundle type light collector, but since acryl is the medium for transmitting the stimulated emission light, the stimulable phosphor plate is used. When the stimulated emission light generated from 31 propagates in the air and enters the condenser 38,
It was not possible to achieve the ideal light collection efficiency because reflection loss occurred due to the difference in the refractive index between air and acrylic, or it was attenuated during propagation.

Next, the second problem of the conventional condenser 38 is as follows.
This means that there are large variations in the light collection efficiency. In the bundle type concentrator, it is caused by the arrangement of many fibers and the dispersion of the transmittance. In the light guide sheet type concentrator, it is caused by the stress when the acrylic is bent and the defects inside and on the acrylic plate. However, there is a problem that the light collection efficiency varies greatly depending on the location.

Next, the third problem of the conventional condenser 38 is as follows.
That is, a collecting mirror is required. The stimulated emission light is emitted to the entire space including the up and down direction of the stimulable phosphor plate 31, centering on the point irradiated with the excitation light. Regarding the stimulated emission light traveling to the lower surface (back side) of the stimulable phosphor plate 31, a method has been devised in which it is effectively used by reflecting it to the front side with a reflective film or the like provided on the back surface of the stimulable phosphor plate 31. However, since it is not the gist of the present invention, it will not be described in detail. Focusing only on the stimulated emission light radiated on the surface, since the above-mentioned conventional condenser 38 is usually provided only on one side of the scanning line, it is radiated on one side where the condenser 38 is not installed. The stimulated emission light thus generated cannot be collected. In order to solve this problem, conventionally, the mirror 61 (see FIG.
(Refer to FIG. 4), and the stimulated emission light reflected by the mirror 61 is directed to the condenser 38 to improve the light collection efficiency. However, the mirror for directing the stimulated emission light emitted at all angles to the condenser 38 is expensive because high processing accuracy is required, which leads to cost increase and time adjustment for position adjustment. There was a problem that it was necessary.

The present invention provides a radiation image reading apparatus which has a high light-collecting efficiency of the light collector, a small variation in light-collecting efficiency depending on the location of the light collector, and a small light collector. To aim.

[0014]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, 31 is a stimulable phosphor plate that absorbs the emitted radiation energy and accumulates it as a latent image, and emits stimulated emission light when irradiated with excitation light. 3 shows the stimulated emission light. The photomultiplier tube 4 for converting into an electric signal is hollow, the inner surface of which is surrounded by a mirror-like wall, and the photocathode area of the photomultiplier tube 3 is the opening of the portion where the photostimulated luminescent light enters. It is a condensing means having a structure of not less than the area and condensing the stimulated emission light to guide it to the photomultiplier tube 3.

[0015]

[Function] A radiation image reading device that absorbs radiation energy and converts the stimulated emission light emitted by irradiating the stimulable phosphor plate 31 accumulated as a latent image with excitation light into an electric signal to obtain image information In the device, the condensing means 4 is hollow, the inner surface of which is surrounded by walls of mirror surfaces, and the area of the photocathode of the photomultiplier tube 3 is equal to or larger than the area of the opening where the stimulated emission light is incident. And collects the stimulated emission light and guides it to the photomultiplier tube 3, and the photomultiplier tube 3 converts the stimulated emission light into an electric signal. Therefore, the stimulated emission light is collected by the light collecting means 4.
Since air is transmitted through the inside as a medium, the optical interface on the incident surface of the light collecting means 4 is eliminated. Further, since the inner surface of the wall surface of the light collecting means 4 is a mirror surface having a constant reflectance regardless of the angle, incident stimulated emission light is not emitted to the outside of the light collecting means 4. Furthermore, since the wall surface has a structure that gradually expands from the entrance to the photomultiplier tube 3, the incident photostimulable light returns to the entrance while repeating reflection, and does not reach the photomultiplier tube 3. Does not occur.

[0016]

2A and 2B are structural views of a condenser according to a first embodiment of the present invention. FIG. 2A is a perspective view and FIG. 2B is an exploded view. FIG. 3 is a configuration diagram of a condenser and a photoelectric converter according to the first embodiment of the present invention, showing a plan view and a side view thereof. Regarding FIG. 2, the present applicant filed Japanese Patent Application No. 2-4079.
It was filed as No. 35 (filed on December 27, 1990).

The concentrator of the present invention is the same as the conventional concentrator 38 described above.
It was invented to solve one of the problems, and the basic shape is, as shown in FIG. 2 and FIG. 3, the inner surface of the upper wall surface 41, the side wall surface 42 and the lower wall surface 43 of the condenser 4a is mirror-finished. It is composed of a plate of metal, glass, resin, or the like, and has a structure in which the wall surface gradually expands from the entrance 45 toward the photoelectric converter 3a or 3b. That is, the area of the exit port 46 is larger than the area of the entrance port 45 of the condenser 4a, and the exit port is determined by the length of the entrance port 45 in the scanning direction and the length in the direction orthogonal to the scanning direction.
The length of 46 in the scanning direction and the length in the direction orthogonal to the scanning direction are longer. Therefore, the photoelectric converter 3a or 3b arranged closely to the emission port 46 is a single photoelectric converter 3b having a photoelectric surface area larger than that of the emission port 46, or the total area of the photoelectric surfaces is the emission port. It is composed of a plurality of photoelectric converters 3a having an area of 46 or more.

By using air as the medium for transmitting the stimulated emission light inside the condenser 4a, the optical interface on the incident surface of the condenser 4a is eliminated, and the stimulated emission light is increased even if the incident angle becomes large. Are made to enter the inside of the light collector 4a. In order to prevent the incident stimulated emission light from being emitted to the outside of the condenser 4a, the inner surface of the wall surface of the condenser 4a is made a mirror surface having a constant reflectance regardless of the angle, and the incident stimulated emission light is also used. While the light is repeatedly reflected, it returns to the entrance 41, and the photoelectric converter 3a or 3b
In order to prevent the situation where the wall surface is not reached, the structure is such that the wall surface gradually expands from the entrance 45 toward the photoelectric converter 3a or 3b. By configuring the condenser 4a in this way, it was possible to improve the conventional first problem of the condensing efficiency.

Further, in the concentrator 4a of the present invention, since the transmission medium is air, the second problem of the conventional example is that there is a variation in the condensing efficiency due to defects and nonuniformity in the transmission medium. do not do.

FIG. 4 is a diagram for explaining the operation of the condenser of the first embodiment of the present invention. The stimulated emission light radiated on one side where the condenser 4a is not installed is the condenser for the scanning line.
It is reflected by a mirror 61 installed at a position opposite to 4a,
The light collection efficiency is improved by directing it toward the light collector 4a.

Further, the condenser 7a according to the second embodiment of the present invention.
According to the mirror of FIG.
It becomes possible to eliminate 61. FIG. 5 is a diagram for explaining the operation of the condenser of the second embodiment of the present invention.

In FIG. 5, the reflector 74 is the mirror 61 of FIG.
It has the same function as and improves the light collection efficiency. FIG. 6 is a structural diagram of a condenser according to a second embodiment of the present invention, which is shown in FIG.
Shows a perspective view and FIG. 6 (b) shows an exploded view.

In FIG. 6 (b), the condenser 7a is provided with a slit 77 for passing the excitation light in a part thereof, and further, at the position where the mirror 61 is installed in FIG. A reflecting plate 74 made of the same material as is provided.

As shown in FIG. 6 (b), the condenser 7a is a combination of five metal plates whose inner surfaces are mirror-finished, and the entrance 75 for stimulated emission light has a long side length. Is about 360 m
m, the short side is a rectangle of 1 to 30 mm. The exit port 76 is larger than the entrance port on both the long and short sides and is 400 m
m, 80 mm. The photoelectric converter 3a has a photoelectric surface of 100 ×
Four 80 mm rectangles are arranged in the scanning line direction.
Although FIG. 6 shows a case where four photoelectric converters 3a are arranged, the number of arranged photoelectric converters 3a can be changed according to the size of the entrance 75 to accommodate various sizes of photostimulable fluorescent plates.

Further, a slit 77 having a size of about 300 μm × 360 mm is formed on the upper wall surface 71 so that the laser light can pass therethrough. Each of the wall surfaces 71-73 made of a metal plate is configured so as to satisfy the angle shown in FIG.

FIG. 7 is a sectional view of a condenser according to the second embodiment of the present invention. In FIG. 7, the angle ∠ABO formed by the reflection plate 74 and the surface of the stimulable phosphor plate 31 is θ2, the angle ∠CAO formed by the upper wall surface 71 and the scanning line is θ1, and the upper wall surface 71 and the surface of the stimulable phosphor plate 31. If the angle ∠CGB formed by θ3 and the angle between the lower wall surface 73 and the surface of the stimulable phosphor plate 31 ∠FED are θ4, then θ2 ≧ 90 ° and ∠AOB from the light emission point O
The stimulated emission light emitted to is reflected by the reflector 74, is entirely taken into the inside of the condenser 7a, and does not return to the surface of the stimulable phosphor plate 31.

By setting θ1 ≧ 90 ° and θ4 ≦ θ3, all the stimulated emission light emitted from the light emitting point O to other than ∠AOB is taken into the inside of the condenser 7a and reflected. While repeating the above, it reaches the photocathode of the photoelectric converter 3a or 3b without returning to the surface of the stimulable phosphor plate 31.

Although FIG. 7 has been described with a two-dimensional plane for simplification of explanation, even if the photostimulated luminescence light emitted at a certain angle with respect to the paper surface, as shown in FIG. Has a structure that spreads from the entrance 75 toward the photoelectric converter 3a or 3b, and thus reaches the photoelectric surface of the photoelectric converter 3a or 3b, and the surface of the stimulable phosphor plate 31 is reached while repeating reflection. Never return to.

FIG. 8 is a constitutional view of a condenser and a photoelectric converter according to a second embodiment of the present invention, showing a plan view and a side view thereof. As can be seen from FIG. 8 (a), the concentrator 7a according to the present invention has an entrance opening in both the thickness direction and the width direction.
Since it has a shape that widens from 75 to the exit 76, the stimulated emission light once taken in from the entrance 75 repeats total reflection on the inner surface of the condenser 7a, regardless of the incident angle.
All reach the photoelectric surface of the photoelectric converter 3a. Also, collector 7a
Since the inside of the air is air, there is no optical interface at the entrance 75, and there is no restriction on the light collection solid angle due to the refractive index of the transmission medium of the light collector 7a. Further, as shown in FIG. 8B, one photoelectric converter 3b having a large-area photoelectric surface may be used instead of the plurality of photoelectric converters 3a.

FIG. 9 is a system configuration diagram of a radiation image reading apparatus showing an embodiment of the present invention. A radiation image reading using the condenser 7a and the photoelectric converter 3a of the second embodiment of the present invention. Shows the device.

A semiconductor laser having a wavelength of 780 nm is used as the excitation light source 34, and the laser beam is scanned by the scanner 35 composed of a galvanometer on the photostimulable phosphor plate 31 in the main scanning direction through the slit 77 of the condenser 7a. To do. Further, by moving the stimulable phosphor plate 31 in the direction perpendicular to the main scanning direction by the precision fine movement table 37, it is possible to scan the entire surface of the stimulable phosphor plate 31 with the excitation light. The stimulated emission light generated by one scanning of the laser beam is condensed by the condenser 7a and guided to the photoelectric converter 3a. Light collector 7a and photoelectric converter
A filter (not shown) that does not transmit light having the wavelength of the excitation light laser but transmits light having the wavelength of stimulated emission light is provided between 3a. The stimulated emission light selectively extracted by this filter is simultaneously converted into an electric signal by the four photoelectric converters 3a, and the output signals from the four photoelectric converters 3a are added by the signal adder 53. It The added signal is amplified by the first-stage amplifier 50 to an optimum signal level for the A / D converter 51, stored in the image memory 52, and subjected to image processing later, C
It is output on RT (not shown) or as a hard copy.

In the present embodiment, the case where the wall surface of the condenser is formed by using the metal plate has been described, but the same effect can be obtained by using other than the metal plate, for example, a glass plate, a plate of resin such as acrylic, etc. A reflective surface may be formed on the surface of the substrate by using a thin film forming technique such as plating, vacuum deposition, sputtering, or ion plating. When forming the reflective thin film on the surface of a metal plate, a glass plate, or a resin plate such as acrylic resin, a dielectric such as ZnS or Na ₃ AlF ₆ or
And by forming a so-called dichroic mirror by stacking multiple metal thin films, the reflectance at the wavelength of stimulated fluorescence is increased,
In addition, the reflectance of laser light can be reduced.

[0033]

As described above, according to the present invention, since the concentrator has a large condensing solid angle and high transmission efficiency,
The stimulated emission light can be efficiently guided to the photoelectric converter, and S
An image with a good / N can be obtained. Further, since the transmission medium is air, and the stimulated emission light from one point is received by a plurality of (large area) photocathodes, the variation of the light collection efficiency due to the location caused by the variation of the medium and the photocathodes. Can be eliminated and a uniform image can be obtained. In addition, since the mirror, which was necessary for improving the light-collecting efficiency, is not required, the device can be inexpensive and downsized, and the time required for adjusting the mirror is not required.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Ishiwata 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Hideyuki Hirano 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (9)

[Claims] 1. Absorbing emitted radiation energy,
A radiation image reading device for obtaining image information by converting stimulated emission light emitted by irradiating excitation light to a stimulable phosphor plate (31) accumulated as a latent image to obtain image information,
A photomultiplier tube (3) for converting stimulated emission light into an electric signal,
The photocathode of the photomultiplier tube (3) has a hollow inner surface surrounded by a mirror wall, and the photocathode area of the photomultiplier tube (3) is equal to or larger than the area of the opening where the stimulated emission light is incident. A radiation image reading apparatus comprising: a light collecting means (4) for collecting the exhausted light and guiding it to the photomultiplier tube (3). 2. absorbing emitted radiation energy,
A radiation image reading device for obtaining image information by converting stimulated emission light emitted by irradiating excitation light to a stimulable phosphor plate (31) accumulated as a latent image to obtain image information,
A photomultiplier tube (3) for converting stimulated emission light into an electric signal,
The inner surface of the photomultiplier tube (3) is hollow and the photocathode area of the photomultiplier tube (3) is defined as A condensing means (4) having a structure which is larger than the area of the opening of the incident part and condenses the stimulated emission light to the photomultiplier tube (3).
) And a radiation image reading device. 3. The light condensing means (4) comprises an upper wall surface having a slit for transmitting excitation light, a lower wall surface facing the upper wall surface, and two pieces provided on both sides of the upper wall surface and the lower wall surface. It is composed of a side wall surface and a reflective wall surface that is in contact with the long side of the upper wall surface and reflects the stimulated emission light to the inside of the light condensing means (4). The upper wall surface and the stimulable phosphor plate (31) The angle formed by the surface of the storage phosphor plate (3) is θ3, the angle formed by the lower wall surface and the surface of the storage phosphor plate (31) is θ4, the reflection wall surface and the storage phosphor plate (3).
The radiation image reading apparatus according to claim 2, characterized in that when the angle formed by 1) and θ2 is θ2, θ4 ≦ θ3 and θ2 ≧ 90 ° are satisfied. 4. The radiation image reading apparatus according to claim 1, wherein the photomultiplier tube (3) is a photomultiplier tube having one photocathode. 5. The radiation image reading apparatus according to claim 1, wherein the photomultiplier tube (3) has a plurality of photomultiplier tubes arranged in a scanning line direction. 6. The condensing means (4) is such that the shape of the opening of the portion where the stimulated emission light is incident is such that the long side is longer than the length of the scanning line and the photocathode of the photomultiplier tube (3) is Characterized by being a rectangle whose length is less than or equal to the total length of the long sides and less than or equal to the length of the short sides of the photocathode of the plurality of photomultiplier tubes (3) in which the lengths of the short sides are arranged. The radiation image reading apparatus according to claim 1, 2, or 3. 7. The light collecting means (4) is composed of a metal plate whose inner surface is mirror-finished.
And the radiation image reading device of 3. 8. The condensing means (4) is characterized in that an inner surface thereof is a dichroic surface having a low reflectance for a wavelength of laser light and a high reflectance for a wavelength of stimulated emission light. Radiation image readers 1, 2, and 3. 9. An optical filter is provided between the condensing means (4) and the photomultiplier tube (3), which transmits the wavelength of stimulated emission light but does not transmit the wavelength of excitation light. The radiation image reading apparatus according to claim 1, 2, or 3.