JPS6052414B2 - Radiation image information reading device - Google Patents

Description

[Detailed Description of the Invention] Previous The present invention irradiates a stimulable fluorophore with excitation light and measures the 15 emitted photostimulated lights, thereby allowing the stimulable fluorophore to be accumulated and recorded in the body. This invention relates to a reading device that reads radiation image information on a light surface.

5. Radiation (X-rays, α-rays, β-rays, γ-rays)
When irradiated with radiation (rays, ultraviolet rays, etc.), a portion of the energy of this radiation, 20 lugs, is accumulated.

If this stimulable phosphor is irradiated with excitation light such as visible light or infrared light, stimulated luminescence will occur depending on the accumulated energy. Light surface: Using this accumulative fluorophore,
The line image lines are recorded once on a sheet-like stimulable phosphor plate, and then this is scanned with a laser beam, etc., and the emitted light is read by an image photodetector, and the image information thus read is used to generate images. An X-ray image forming apparatus is known that modulates a light beam to record an X-ray image on a recording medium such as a photographic film (US Pat. No. 3,859,527).

In this device, there are four
5 has a large slanted half mirror. The excitation light passes through this half mirror and enters the stimulable phosphor. The emitted light is reflected laterally by a half mirror, collected by a condenser lens, and enters a photodetector. The light emitted from this stimulable phosphor plate is non-directional and is itself weak light, so it is necessary to increase the light-receiving solid angle as much as possible to collect as much light as possible to increase light collection efficiency.

If this light collection efficiency is low, the S/N ratio decreases, and in the worst case, it becomes impossible to even detect a signal. However, with the above device,
Due to its configuration, the solid angle of light reception of the photodetector cannot be made sufficiently large, and there is a drawback that the light collection efficiency is poor.

Therefore, the present inventors proposed Japanese Patent Application No. 53-163572 (
In Japanese Patent Application Laid-Open No. 55-8797, a photodetector 2 for detecting light emitted by a stimulable phosphor plate 1 as shown in FIG.
and the stimulable phosphor plate 1, a light transmitting means 3 made of a light-guiding sheet material is provided, one end of which faces the scanning line on the stimulable phosphor plate 1, and the other end facing the scanning line on the stimulable phosphor plate 1. It was proposed to improve the S/N ratio by increasing the light collection efficiency of the light receiving surface by forming it to match the shape of the light receiving surface of the detector 2 and placing it adjacent to the light receiving surface.

By providing such a light transmission means as described above, the light collection efficiency and S/N ratio can be greatly improved compared to the conventional method. However, since this light transmission means is temporarily installed on one side of the scanning line, only the light that is emitted from this scanning line and traveling toward this one side can be effectively used. There is a drawback.

Therefore, the inventors also discovered that light traveling to the other side can also be used. In order to effectively utilize the light and increase the light collection efficiency, the above-mentioned patent application No. 53-1
In No. 635η, we proposed that two light transmitting means be placed opposite each other across a scanning line on a phosphor plate to collect most of the light emitted from the scanning line (see Figure 1).
However, this proposal not only requires two optical transmission means, but also two photodetectors, and an adder to add the outputs of the two photodetectors, making the device difficult to use. It has the drawbacks of being expensive and requiring a large amount of space. SUMMARY OF THE INVENTION In view of the above drawbacks, it is an object of the present invention to provide a radiation image information reading device that can increase light collection efficiency and improve the S/N ratio.

Such an object of the present invention is to provide a concentrator, which has one end adjacent to the scanning line on the phosphor plate, between a photodetector for detecting light emitted by the stimulable phosphor plate and the phosphor plate. A light transmitting means made of a light guiding sheet material is provided, the other end being a light surface and the other end being a light emitting surface formed to match the shape of the light receiving surface of the photodetector and provided adjacent to the light receiving surface. , a reflective surface faces the light condensing surface of the light transmission means on the opposite side of the scanning line with respect to the light condensing surface provided adjacent to the scanning line of the light transmission means. This was achieved by arranging a reflective optical means with a length approximately equal to the optical surface.

The reflective surface of the reflective optical means receives most of the light emitted from the phosphor plate other than the light directly incident on the light converging surface of the light transmitting means, and transfers the light to the light condensing surface. A non-linear (1
(one or more curved surfaces or a combination of multiple planes). The light rays from the light emitting point on the scanning line spread radially, so in order to make these rays enter the converging surface,
The cross-sectional shape of the reflective surface in a plane perpendicular to the condensing surface is:
It is desirable that the shape is a part of an ellipse or a parabola with the scanning line (light emitting point) as the focal point. The condensing surface of the light transmitting means and the reflecting optical means are spaced apart from each other so that the excitation line is incident on the phosphor plate surface. In the present invention, the light transmission means is made of a material that is transparent to the wavelength of the light to be focused, and is as homogeneous as possible so that there is no loss of the light to be focused within the material, and
It is necessary to use a material in which the light to be focused undergoes so-called total reflection on the surface of the material (at the interface with air).

It is also necessary that the surface be finished sufficiently smooth. Further, its shape is required to be a straight line at one end facing the scanning surface, and an annular shape matching the shape of the light receiving surface of the photodetector at the other end.

The end face shape of the light transmitting means provided on the light-receiving surface of the photodetector need only be an annular shape that matches the light-receiving surface of the photodetector, and the shape of the sheet wrapped in a circular ring may also be used if the circular ring is closed. It may be in a shape that is not What is important here is that the main light transmission stage itself needs to be made of a material shaped so that when rolled, it becomes a single sheet with approximately uniform thickness and width. It is. This increases the probability of total reflection inside the light transmission means, making it possible to prevent light loss. The stimulable phosphor used in the present invention preferably has a stimulable emission wavelength of 300 to 500 nm, such as a rare earth element-activated alkaline earth metal fluorohalide phosphor [specifically, a 8474 Specification (Japanese Patent Application Laid-Open No. 1983-12)
(Bal-x-Y, M
gx, Cay) FX:AEl]2+ (where X is at least one of Cf and Br, and x and y are 0
x+y≦0.6 and Xy half 0, and a is 10-6≦
(Bal-X, Mllx)FX:YA (where M is Mg,
At least one of Ca, Cr, Zn and Cd,
x is at least one of Ce, Br and I, A is Eu, Tb, Ce, Tm, Dy, Pr, HO, Nd, Y
at least one of b and Er, x is 0≦x≦0
．． 6, y is O≦y≦0.2), etc.; Patent application 1987
-847 wholesale specification (Japanese Patent Application Laid-Open No. 55-12142)
It is described in. ZnS: Cu, Pb. ．． BaO-X
Ae2O3:Eu (0.8≦x≦10) and MO
・XSlO2: A (where M is Mg, Ca, Sr, Zn,
Cd or? and A is Ce, TO, Eu, Tm, P
b, Te, Bi or Mn, and x is 0.5≦x≦2
．． 5); and LnO described in Japanese Patent Application No. 53-84743 (Japanese Unexamined Patent Publication No. 55-12144)
X:XA (Ln is at least one of La, Y, Gd and Lu, x is at least one of Ce and Br, A is at least one of Ce and Tb, x is O<X <0.1); and the like. Among these, rare earth element-activated alkaline earth metal fluorohalide phosphors are preferred, and among these, barium fluorohalides shown as specific examples are particularly preferred because of their excellent stimulable luminescence. Furthermore, if the phosphor layer of the stimulable phosphor plate prepared using this stimulable phosphor plate is colored with a pigment or dye, the sharpness of the final image will be improved, resulting in favorable results. (Japanese Patent Application No. Sho M-71604 (Japanese Unexamined Patent Publication No. Sho 55-16350)).

In the present invention, a laser beam with good directivity is used as excitation light for reading out the radiation image accumulated on the stimulable phosphor plate. As a laser beam excitation light source, 50
0-800r1rn1 preferably 600-700r1m
A device that emits light of 1, such as a He-Ne laser (
633 nm) and a Kr laser (647 r1m) are preferred, but excitation light sources other than those mentioned above can also be used if a filter that cuts out light other than 500 to 800 r1m is used in combination. Materials for the light transmission means according to the present invention include acrylic resin, vinyl chloride resin, polycarbonate resin,
Transparent thermoplastic synthetic resins such as polyester resins and epoxy resins, glass, etc. can be used.

Among these, quartz glass and acrylic resin are excellent light transmission means for the emission spectrum of the phosphor according to the present invention. Furthermore, from the viewpoint of processability, acrylic resin and other synthetic resins are preferred. Therefore, from both of these points, it can be said that acrylic resin is the most desirable material for the light transmission means. The light transmission means according to the present invention can be manufactured by heating and softening the sheet, and in addition to the above-mentioned heating and softening of the sheet and processing it into a predetermined shape, various types of pressing, casting, etc. are used. You can also do that. However, since it is not possible to have a smooth mirror surface that allows total reflection light to be transmitted by pressing or casting, it is preferable to use the above-mentioned heat softening and deformation processing that does not touch the surface. The radiation image read according to the present invention is subjected to image processing and reproduced on a recording medium, and as the recording medium, in addition to silver halide photographic film, diazo film, electrophotographic material, etc. can be used.

It may also be displayed on a CRT or the like. In the present invention, the stimulable phosphor plate is scanned by a laser beam, but scanning generally involves a method of performing main scanning and sub-scanning simultaneously with either the stimulable phosphor plate or the laser beam, and a method of simultaneously performing main scanning and sub-scanning of either the stimulable phosphor plate or the laser beam. There is a method of scanning two-dimensionally by combining movements, but in the apparatus of the present invention, the light transmission means is provided adjacent to the scanning line of the laser beam on the stimulable phosphor plate, so only the sub-scanning is performed mechanically. There is a structural merit in that it can be done in a consistent manner. In this case, the sub-scanning is performed by moving the phosphor plate itself, or by moving the light transmitting means and the main scanning by a laser beam together on the phosphor plate. Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a schematic side view of an image information reading device using a photodetector having a circular light-receiving surface, and FIG. 3 is a perspective view thereof, showing an embodiment using a holder 10 capable of linear movement on a plane. It is something.

On the surface of the holder 10 is a rectangular stimulable phosphor plate 1.
1 is installed. X-ray image information is recorded on this stimulable phosphor plate 11 by ordinary X-ray photography. The stimulable phosphor plate 11 is one with a d angle, and BaFBr:Eu phosphor with an average particle size of 10 μm is coated on a cellulose triacetate support using nitrocellulose and dried. The film thickness was 200μ.

The light transmitting means 12 is arranged so that the condensing surface 12a faces the stimulable phosphor plate 11 as close as possible, and the light emitting surface 12b of the light transmitting means 12 is in close contact with the light detector. 13 are arranged.

The photodetector 13 should have as large a light receiving area as possible, and since it measures weak light emission, S
A material with a good /N ratio is desirable.

Examples of such a photodetector 13 include a head-on type photomultiplier tube having a light-receiving surface formed on its end face, a channel plate for photoelectron amplification, and the like. Details of the light transmission means 12 are shown in FIG. The light transmitting means 12 is made of a light guide sheet, one end surface 12a is linear, and the other end surface 12b, which is in close contact with the photodetector 13, has the shape of the light receiving surface of the photodetector (in this case, It has a shape that is rolled up in an annular shape to match the circular shape. This light guide sheet has a thickness of 8wn
A length of 15C71 is used. Light transmission means 12
A light condensing surface 12a provided on the scanning line 16 (see FIG. 5)
On the opposite side across this scanning line 16, there is a reflective surface 1.
7a faces the light condensing surface 12a, and a reflective optical means 17 having a length substantially equal to the condensing surface 12a is disposed. This reflective optical means 17 consists of a reflective mirror with aluminum or silver deposited on the surface of the substrate. The reflective surface 17a receives most of the light L2 emitted from the scanning line 16 on the phosphor plate 11, excluding the light L1 directly incident on the condensing surface 12a, and directs this toward the condensing surface 12a. As such, it has a non-linear shape in a cross section perpendicular to the light condensing surface 12a. Since the light ray L2 from the scanning line 16 spreads radially, the transverse shape of this reflecting surface is an ellipse (or parabola) with the scanning line 16 as the focal point in order to make the light ray L2 enter the converging surface 12a as efficiently as possible. 18 is desirable. However, the reflection surface 17a does not necessarily have to be an ellipsoid or a paraboloid, as long as sufficient incidence/injection efficiency can be obtained, for example, at least two reflection planes 1
It may also consist of a mirror with 9a and 19b. In this case the reflective planes 19a and 19b are respectively scan line 1
6 and at an angle to each other. In addition, by combining a large number of reflection planes, the above two
Although it is possible to have a shape that approximates the following curved surface, since it is easy to manufacture, the reflecting optical means is usually made up of two or three reflecting planes. Since there is absorption, it is desirable that the reflective optical means 17 be reflected once.The reflective optical means 17 may be arranged and fixed at a predetermined angle with respect to the light collecting surface 12a. In order to make the angle of the reflection surface 17a with respect to the light collection surface 12a variable so as to correct uneven light collection in the direction, it may be attached via a screw 20 or the like as shown in FIG. 7.A laser that emits red light. The laser beam from the light source 15 is directed to the stimulable phosphor plate 11 by the optical deflector 14.
The stimulable phosphor plate 11 is vibrated in a direction substantially parallel to one edge of the stimulable phosphor plate 11, resulting in a beam that scans the stimulable phosphor plate 11 in that direction.

A red laser beam having a wavelength of 600 to 700 nm emitted from a laser light source 15 is turned into a scanning beam by an optical deflector 14, and is incident on a stimulable phosphor plate 11 mounted on a holder 10, where it emits a stimulable fluorescent light. Excite body layers.

This light excitation causes the stimulable phosphor layer to emit stimulated light. This luminescence corresponds to the energy accumulated by X-ray irradiation. Therefore, the emitted light from each point carries the X-ray image information at that point. By the laser scanning beam and the movement of the stimulable phosphor plate 11 in a direction perpendicular thereto, the stimulable phosphor plate 11 is two-dimensionally scanned, and each point on the stimulable phosphor plate 11 emits light.

A part of the emitted light is transmitted directly to the light converging surface 12 of the light transmitting means 12, and most of the remaining part is transmitted through the reflective optical means 17.
The light enters the light transmitting means 12 from a point a, is transmitted inside the light transmitting means 12, enters the light receiving surface of the photodetector 13 via the other end face, and is converted into an electrical signal. The read X-ray image information controls the laser light modulator of the photographic film exposure device.

Using this laser light whose intensity is controlled, an X-ray image is reproduced on a recording medium such as a photographic film. In the case of the present invention, a single layer of the filter as described above may be provided on the converging surface 12a of the light transmitting means 12, or a single layer of this filter may be provided on the light receiving surface of the photodetector 13.

Alternatively, the light transmitting means 12 itself may be colored and used as a filter. The filter layer can also be provided as a vapor deposited film. As the photodetector 13, one that is sensitive only to emitted light and not to excitation light may be used, or a filter may be attached in front of the photodetector 13 to allow only emitted light to pass through. Good too. According to the present invention, the weak light emitted from the stimulable phosphor plate by the scanning beam is efficiently collected and detected by the combination of the light transmission means made of the light guiding sheet and the reflective optical means. Since the light can be incident on the device, the collection efficiency is greatly improved compared to conventional devices, and the S/N ratio can thereby be significantly improved, and the cost is lower than that of conventional devices. It has major features in that it is extremely inexpensive and compact.

The present invention scans light in a linear manner, and the reflected light or transmitted light (
In particular, it provides a means to efficiently condense light (scattered light).
Needless to say, it can be widely applied to all such purposes.

EXAMPLE An acrylic resin sheet (1 Acrylite #000J manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of 5 TrON was heated and softened to prepare a light transmission means sample having a width of 200 W 1 B at the end on the incident side.

Here, one end of the light transmission means was formed into a straight line shape, and the other end was formed into an annular shape so as to fit within the light receiving surface of a 3-inch photomultiplier tube. As the reflective optical means 17, one made of vapor-deposited aluminum and having an elliptical cross-sectional shape was used. The effective reflectance was about 92.5% for the wavelength of light emitted from the phosphor. Here, the stimulable phosphor plate 11 placed on the holder 10 is made of 200TH! made of BaFBr:Eu. ! t×200? A size of 1 was used.

In addition, as a laser light source, output 10n1Wf) He-N
An e-laser (633 nm) was used. In the experiment, a laser beam was scanned on the phosphor plate 11 by a scanning mirror 14 to cause the phosphor plate 11 to emit light, and the emitted light was first focused by one light transmission means, and then the second one was focused. The light condensed from one light transmission means by one reflective optical means was detected by a 3-inch head-on photomultiplier tube 13 having an S-11 type spectral sensitivity distribution.

A filter having a transmittance of 0.01% for light of 633r1rn and 80% for light of 400nn1 was placed in front of the Stl photomultiplier tube 13. As a result, it is approximately 1.8 to 1.5 times better to collect light using a combination of light transmitting means than to collect light using only one light transmitting means.
It was found that the light collection efficiency could be increased by 85 times.

This light collection efficiency is only slightly inferior to the light collection rate (twice) when two light transmission means and two photodetectors are used.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional radiation image information reading device, FIGS. 2 and 3 are a side view and a perspective view showing an embodiment of the present invention, and FIG. FIG. 5 is a perspective view showing the transmission means, FIG. 5 is a side view illustrating the positional relationship between the condensing surface of the light transmission means and the reflection surface of the reflection optical means, and FIG. 6 is a perspective view showing a modified example of the reflection optical means. FIG. 7, a similar figure, is a perspective view of a structure in which the longitudinal position of the reflective optical means can be adjusted with respect to the converging surface of the light transmitting means. 1, 11... Accumulative phosphor plate, 3, 12...
... Light transmission means, 2, 13 ... Photodetector, 12
a... Light condensing surface, 12b... Light exit surface, 17
......Light reflecting means, 17a...Reflecting surface,
19a, 19b...Reflection B plane, 20...
··screw.

Claims (1)

[Scope of Claims] 1. In a radiation image information reading device that scans a stimulable phosphor plate with excitation light and reads radiation image information accumulated and recorded thereon by stimulating luminescence, the phosphor plate Between the photodetector that detects the light emitted by the photodetector and this phosphor plate, one end is a light converging surface provided adjacent to the scanning line on the phosphor plate, and the other end is a condensing surface provided on the scanning line of the photodetector. A light transmitting means made of a light-guiding sheet-like material is provided, which is a light-emitting surface formed to match the shape of the light-receiving surface and provided adjacent to the light-receiving surface; Disposed on the opposite side of the light condensing surface across the scanning line is a reflective optical means whose reflective surface faces the light condensing surface of the light transmission means and has a length approximately equal to that of the condensing surface. The light-condensing surface is configured such that the reflective surface receives most of the light emitted from the phosphor plate other than the light that is directly incident on the light-condensing surface, and directs this toward the light-condensing surface. It has a non-linear shape in a vertical cross section, and the light collecting surface of the light transmitting means and the reflecting optical means are spaced apart from each other so that the excitation light can enter the surface of the phosphor plate. A radiation image information reading device characterized by: 2. A cross-sectional shape of the reflective surface of the reflective optical means in a plane perpendicular to the condensing surface is a shape that forms part of an ellipse with the scanning line as the focal point. The radiation image information reading device according to item 1. 3. Claim characterized in that the reflective optical means comprises a mirror having at least two reflective planes, each of which is located parallel to the scanning line and at an angle with respect to each other. The radiation image information reading device according to item 1. 4. Any one of claims 1 to 3, wherein the reflective optical means is arranged so as to be able to change its angle with respect to the light condensing surface of the phosphor plate. The radiation image information reading device described in .