JPH07171143A - Radioactive ray image reading device - Google Patents

Abstract

PURPOSE:To enhance converging efficiency by providing an accelerated phosphorescent fluorescencer for absorbing the radiation energy part transmitted by a subject, and providing radioactive ray image information from the photoelectric signal of the accelerated phosphorescent light emitted by emitting an exciting light to the fluorescencer, and using a specified condenser. CONSTITUTION:A radioactive ray image reading device has a flat accelerated phosphorescent fluorescencer 1 in which the radiation energy part transmitted by a subject is accumulated as a latent image. The accelerated phosphorescent light is emitted from the fluorescencer 1 by the emission of an exciting light 2, this accelerated phosphorescent light is converged by a condenser 8, and the electric signal obtained in a photoelectric converter 4 is subjected to a necessary processing and outputted to a CRT. The condenser 8 is formed into block from a transparent member, and reflecting films 5 for reflecting the accelerated phosphorescent light are provided on both the side surfaces and the lower wall surface. It also has a slit 6 for transmitting the exciting light 2 and the accelerated phosphorescent light substantially in the center part of the lower wall surface, and a dichroic reflecting surface 7 gradually increased in height from about the center toward both the end parts in the inner part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image reading apparatus, and more particularly, to a phosphor plate or sheet having radiation image information stored therein, which is scanned with an excitation light beam to produce stimulated emission of light corresponding to the image information. The present invention relates to a radiation image information reading device that generates light and photoelectrically converts this stimulated emission light to read the image information as an electric signal.

Radiation images such as X-ray images are widely used for disease diagnosis and the like. A means for obtaining an X-ray image is a so-called radiograph in which a phosphor layer (fluorescent screen) is irradiated with X-rays that have passed through a subject, and thereby visible light is irradiated to a film using a silver salt for development. Has been used more often than before.

On the other hand, as a high-sensitivity and high-resolution X-ray imaging system, photostimulable fluorescence is used 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. The method of using body 1 is beginning to be used.

Such a method is disclosed in US Pat. No. 3,859,527.
It is described in detail in the issue and is structured as follows.
That is, the phosphor used in this system is a so-called stimulable phosphor 1 which accumulates energy in the phosphor crystal when receiving the energy of radiation such as X-rays. It is stable and is retained for a while or for a long time.

When the phosphor in this state is irradiated with the first light which acts as the excitation light, the stimulated emission light having the intensity corresponding to the stored energy is emitted as the second light.
The first light is not limited to visible light, but light of a wide wavelength range from infrared to ultraviolet is used as the first light, depending on the phosphor material used, and the second light is also from infrared to ultraviolet. There are various types depending on the phosphor material used.

Utilizing the characteristics of such a stimulable phosphor, first, radiation transmitted through an object such as a human body is irradiated and recorded on a stimulable phosphor plate or sheet, and the stimulable phosphor is irradiated with a laser beam or the like. The excited light is scanned to generate stimulated emission light.

Then, after the light is collected and received by the light collecting means, it is converted into an electric signal by the photoelectric converter to obtain an electric signal proportional to the intensity of the accumulated radiation. afterwards,
Image processing is performed using this electric signal, and a visible radiation image is obtained by printing on a silver salt film or displaying on a display.

[0008]

2. Description of the Related Art A conventional example of a radiation image reading apparatus using the above stimulable phosphor 1 is shown in FIG. In this conventional example, 2b indicates an excitation light source, and the excitation light source 2b
The laser beam (excitation light 2) emitted from the laser beam is scanned by the galvanometer 2c in the main scanning direction, passes through the fθ lens 2d, and is then irradiated on the stimulable phosphor 1. The stimulable phosphor 1 is driven in the direction orthogonal to the main scanning direction by the precision fine movement table 13, and the excitation light 2 scans the entire surface of the stimulable phosphor 1.

The stimulated emission light 3 generated by one scanning of the laser beam is condensed by the light guide path 14 in which a large number of optical fibers are bundled, and is guided to the photomultiplier (photoelectric converter 4). Light guide 14 and photomultiplier 4
A filter (not shown) which does not transmit the light of the excitation light 2 laser but transmits the light of the wavelength of the stimulated emission light 3 is installed between the two, and the bright light selectively extracted by the filter is installed. The exhaust light 3 is converted into an electric signal by the photomultiplier 4 and is amplified by the first stage amplifier 15 to an optimum signal level for the A / D converter 12.

The image data converted into a digital signal by the A / D converter 12 is stored in the image memory 16, and after being subjected to image processing, is displayed on a display device such as a CRT or is output as a hard copy. It

Here, in order to obtain an image with a good S / N, it is important to collect the stimulated emission light 3 generated efficiently and uniformly and guide it to the photoelectric converter 4. The generated stimulated emission light 3 has no directivity and diverges into the entire space, so that the condenser 8 can collect light over a wide solid angle as much as possible. It is desirable that there is no loss such as internal attenuation and return light, and further, a photomultiplier 4 that is connected to a condenser 8 and photoelectrically converts the stimulated emission light 3.
Is that the dark current, which is a noise source, increases in proportion to the size of the photocathode, and that large ones are generally expensive,
In addition, since it leads to an increase in the volume of the device, it is desirable that the device be as small as possible.

Conventionally, as a condensing means that meets such a demand, as shown in FIG. 16 (a), a so-called bundle type concentrator in which a large number of plastic fibers or glass fibers are bundled, or FIG. 16 (b) is used. A so-called light guide sheet type concentrator in which a plastic plate such as acrylic is bent is used as shown in FIG.

However, the following drawbacks have been pointed out in the reading apparatus using such a condenser 8. That is, in the above-mentioned bundle type light collector,
The solid angle at which light can be collected is determined by the numerical aperture of the plastic fiber or glass fiber used. Generally, plastic fiber and multi-component glass fiber have a larger numerical aperture than quartz fiber. , The attenuation factor for the light of the wavelength of the stimulated emission light 3 is large,
It cannot be expected to improve the light collection efficiency as a whole.

Further, in the light guide sheet type collector,
Although the solid angle that can collect light is larger than that of the bundle-type light collector, since the medium that transmits the stimulated emission light 3 is acrylic, the stimulated emission light 3 generated from the stimulable phosphor 1 is air. When propagating through the inside and entering the condenser 8, reflection loss occurs due to a difference in refractive index between air and acryl, or attenuation occurs during the propagation, so that ideal condensing efficiency cannot be achieved.

Further, the second drawback of the light collector 8 according to the conventional example described above is that the light collection efficiency varies greatly. That is, in the bundle type concentrator, it is caused by the arrangement of the multiple fibers and the variation in the transmittance, and in the light guide sheet type concentrator, the stress when the acrylic is bent and the defects inside the acrylic plate and the surface are caused. For this reason, the variation in light collection efficiency depending on the location becomes large.

In addition, the third drawback of the above-described conventional condenser 8 is that a condenser mirror is essential. That is, the stimulated emission light 3 is emitted into the entire space including the up and down direction of the stimulable phosphor 1 with the point irradiated with the excitation light 2 as the center, and the condenser 8 causes the scanning line to move. Since it is provided only on one side, it becomes impossible to capture the stimulated emission light 3 emitted in the opposite direction.

In order to solve such a problem, the conventional method shown in FIG.
7, a condenser mirror 17 is installed at a position facing the condenser 8 with respect to the scanning line, and the stimulated emission light 3 emitted in the opposite direction by the condenser mirror 17 is condensed by the condenser 8 However, in order to manufacture the condenser mirror 17 that directs the stimulated emission light 3 emitted at all angles to the condenser 8, high processing accuracy is required. In addition to being expensive, position adjustment is very troublesome.

The present invention has been made to solve the above-mentioned drawbacks. By increasing the light-collecting solid angle and reducing the attenuation and the reflection loss, the light-collecting efficiency of stimulated emission light is improved. It is an object of the present invention to provide a radiographic image reading device having improved performance.

Further, another object of the present invention is to reduce variations in light collection efficiency depending on locations, that is, shading, and to reduce the size of the light collector and the photoelectric converter. In addition, it is an object of the present invention to provide a radiation image reading apparatus that facilitates adjustment, is inexpensive, and does not require a condenser mirror.

[0020]

1 and 2 show a radiation image reading apparatus of the present invention. Reference numeral 1 denotes a sheet or plate-shaped stimulable phosphor that accumulates a part of the radiation energy transmitted through the subject as a latent image, and emits stimulated emission light 3 upon irradiation with excitation light 2.

The stimulated emission light 3 is condensed by the condenser 8 and then converted into an electric signal by the photoelectric converter 4, subjected to necessary processing and output to a CRT or a printer. As shown in detail in FIGS. 3 and 4, the condenser 8 is formed of a transparent material in the shape of a prism having a long shape in the main scanning line 2a direction, and has excitation on both side walls parallel to the main scanning line 2a. A reflection film 5 for reflecting the light 2 and the stimulated emission light 3 emitted from the stimulable phosphor 1 is formed, and the laser light and the stimulated emission light 3 are transmitted to the lower wall surface at approximately the center. The slit 6 for forming is formed.

Further, inside the condenser 8, a dichroic reflection surface 7 having a characteristic of transmitting the wavelength of the excitation light beam (excitation light 2) and reflecting the wavelength of the stimulated emission light 3 is formed. The dichroic reflection surface 7 is formed at a position where the height thereof increases from substantially the center of the main scanning line 2a toward both ends of the scanning line.

[0023]

The excitation light 2 is scanned along the scanning line direction, enters from the upper surface of the condenser 8, passes through the dichroic reflection surface 7, passes through the slit 6 on the lower wall surface of the condenser 8, and is condensed. Bowl 8
Is irradiated to the stimulable phosphor 1 arranged close to the lower surface of the.

The stimulated emission light 3 generated by the irradiation of the excitation light 2 is taken into the inside of the condenser 8 from the slit 6 as shown in FIG. 5, and the dichroic reflection surface 7 or both sides having the reflection film 5 are provided. Reach the wall.

The dichroic reflecting surface 7 has a photostimulable luminescent light 3
Of the excitation light 2, and at the same time, functions as a transmission film for the excitation light 2, so that the excitation light 2 is reflected from the stimulable phosphor 1 and taken into the condenser 8 from the slit 6. The excitation light 2 is emitted to the outside of the condenser 8 again, whereas the stimulated emission light 3 is reflected by the dichroic reflection surface 7 at a reflection angle substantially equal to the incident angle to the lower wall surface side, The dichroic reflection surface 7 is reached again.

On the other hand, since the dichroic reflecting surface 7 is arranged so that its height gradually increases from the approximate center of the main scanning line 2a toward both ends thereof, the dichroic reflecting surface 7 of the main scanning line 2a is initially reflected. The stimulated emission light 3 directed to the central portion gradually has an acute incident angle, and is finally switched to the reflection toward the end face of the condenser 8.

In short, the excitation light 2 is emitted to the outside of the condenser 8 as much as possible, and only the stimulated emission light 3 is reflected on the dichroic reflection surface 7, both side walls and the lower wall surface. Since it becomes possible to repeat reflection and guide the light to both end faces of the condenser 8, it is possible to obtain a high-quality signal with desired intensity.

Further, in the invention described in claim 2, the dichroic reflection surface 7 of the condenser 8 is formed so that its height gradually increases from one end of the main scanning line 2a to the other end thereof. The stimulated emission light 3 is guided to one end surface of the condenser 8.

Further, in the invention according to claim 3, the dichroic reflecting surface 7 is at least 350 nm to 5 nm.
In the wavelength band of 00 nm, the stimulated emission light 3 is formed as a multilayer reflective surface having a reflectance of 90% or more and is excited by the excitation light beam 2 having a wavelength of about 780 nm.
The emission of light to the outside of the light collector 8 is prevented as much as possible.

In the fourth aspect of the invention, the condenser 8 is formed by joining two transparent block bodies 8a and 8b having the dichroic reflection surface 7 as an interface with an optical adhesive.

Further, in the invention described in claim 5, the condenser 8 is replaced with the excitation light 2 instead of the dichroic reflection surface 7.
And a reflecting surface 9 that reflects the stimulated emission light 3, and a slit 9a that is provided substantially in the center of the reflection surface 9 in parallel with the main scanning line 2a and that transmits the excitation light 2 and the stimulated emission light 3. It is formed.

The stimulable luminescent light 3 emitted from the stimulable phosphor 1 is emitted in all directions, so that the internal slit 9
The amount emitted from a to the outside of the condenser 8 is very small,
The light collection efficiency is not significantly reduced, and the manufacturing is easier than when the dichroic reflection surface 7 is formed.

Further, in the manufacture of the condenser 8, as described in claim 6, two transparent block bodies 8a and 8b having the reflecting surface 9 provided with the slit 9a as an interface are joined by an optical adhesive. This can be done by

In the invention as set forth in claim 7, the light receiving surface 4a of the photoelectric converter 4 is directly attached to both end surfaces or one end surface of the condenser 8, specifically, the end surface on the side where the stimulated emission light 3 is guided. ,
Optically connected, the structure is simple.

Further, in the invention described in claim 8, the transmittance of the wavelength of the excitation light 2 is low and the transmittance of the wavelength of the stimulated emission light 3 is between the condenser 8 and the photoelectric converter 4. A high optical filter 10 is provided to prevent the excitation light beam 2 from being introduced into the photoelectric converter 4.

In the invention described in claims 9, 10, 11 and 12, the stimulated emission light 3 guided to the end face of the condenser 8 is bent at an appropriate angle by the reflection prism 11 and is arranged at an arbitrary position. To the photoelectric converter 4.

In the thirteenth aspect of the invention, the optical filter 10 is a color glass filter having a transmittance of 80% or more in the wavelength band of 400 nm to 450 nm.

By using the condenser 8 of the present invention in which the excited light beam 2 is less likely to be mixed into the stimulated emission light 3 to be taken out, the optical filter 10 need not consider the blocking performance of the excited light beam 2. Therefore, it becomes possible to select a filter centering on the transmittance of the stimulated emission light 3.

In the fourteenth aspect of the invention, the light collector 8
The reflective film 5 is formed of an aluminum vapor deposition film, which facilitates manufacturing. Further, in the invention as set forth in claim 15, the reflective film 5 of the condenser 8 has a high reflectance at the wavelength of the stimulated emission light 3 and a low reflectance at the wavelength of the excitation light 2. Is formed by.

With such a structure, while repeating reflection inside the condenser 8, the stimulated emission light 3 is reliably reflected inside the condenser 8, while the excitation light 2 is collected from the wall surface. 8 is transmitted and emitted to the outside, and the utilization efficiency of the stimulated emission light 3 is improved.

In the sixteenth aspect of the invention, the condenser 8
A black coating is applied to the lower surface of the surface facing the stimulable phosphor 1. In the black coating, the excitation light 2 that has reached the stimulable phosphor 1 after passing through the slit 6 on the lower wall surface again collects light.
Generation of stimulated emission light 3 from a site other than the scanning line due to excitation of the stimulable phosphor 1 by reflection from the lower wall surface is prevented.

In the seventeenth aspect of the invention, the condenser 8
An antireflection film is provided on the slit 6. The antireflection film prevents the excitation light 2 and the stimulated emission light 3 from being reflected when passing through the slit 6, and improves the utilization efficiency of the excitation light 2 and the stimulated emission light 3.

In the eighteenth aspect of the present invention, the stimulable phosphor 1 is formed of a transparent substrate, a phosphor layer, and a transparent protective film, and the condenser 8 includes the stimulable phosphor 1. The photostimulable phosphor 1 is sandwiched and arranged on the front and back. The stimulated emission light 3 generated by being excited by the excitation light 2 is emitted to the front and back of the stimulable phosphor 1, and is condensed by the condensers 8 on the front and back.

In the invention according to claim 19, the excitation light 2
The main scanning speed of is increased toward the end of the scanning line. By changing the main scanning speed, the condenser 8
Velocity delay due to refraction of the excitation light 2 inside, more specifically, the photostimulable phosphor 1 as it goes to the end of the main scanning line 2a due to refraction.
Distortion of the image due to the slower scanning speed of the image is prevented.

Further, in the invention of claim 20,
The above-mentioned problem is solved by lowering the sampling frequency of the A / D converter 12 toward the end of the scan line.

[0046]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. First, the condenser 8 used in the present invention will be described with reference to FIGS.

The condenser 8 comprises a pair of transparent block bodies 8a,
By adhering 8b with an optical adhesive, a prism shape that is long in the scanning line direction is formed. Transparent block body 8a,
8b is formed of, for example, a glass block such as quartz, and one is formed in a reverse roof shape so that the height thereof increases from substantially the center of the scanning line to both ends of the scanning line, and the other is The roof-shaped block has a V-shaped projection that matches the V-shaped recess of the inverted roof-shaped block and is combined with the inverted-roofed block 8b to form a prismatic shape.

A dichroic reflection surface 7 having a characteristic of transmitting the wavelength of the excitation light beam 2 and reflecting the wavelength of the stimulated emission light 3 is formed on the upper surface of the inverted roof type block 8b or the lower surface of the roof type block 8a. After that, they are adhered with an optical adhesive.

An example of the characteristics of the dichroic reflecting surface 7 is shown in FIG. The dichroic reflection surface 7 has a wavelength of the excitation light beam 2 of about 780 nm and a wavelength of the stimulated emission light 3 of 4
It shows effective characteristics when the thickness is about 00 nm.
nS, a dielectric such as NaAlF ₆ or the like and a metal thin film formed by stacking multiple layers, and has a large reflectance of the wavelength of the stimulated emission light 3 and the wavelength of the excitation light beam 2 (about 780 n
The reflectance of m) is reduced.

Further, the required reflection wavelength band is 4
The dichroic reflection surface 7 is set to have a wavelength sufficiently longer than the wavelength of 00 nm (600 nm in this example).
Even if the incident angle of the stimulated emission light 3 with respect to is large, good reflection characteristics can be ensured, and as a result, the excitation light beam 2
Since the stimulated emission light 3 generated from the point light source is reflected in a wide angle range and can be guided to both ends of the condenser 8, it is possible to significantly improve the light collection efficiency.

Of the condenser 8 formed as described above,
A reflective film 5 made of aluminum or the like is formed on both side surfaces and a lower wall surface which are parallel to the main scanning line 2a. Further, a slit 6 for peeling off the reflection film 5 and transmitting the excitation light beam 2 and the stimulated emission light 3 is formed in a substantially central portion of the lower wall surface. The slits 6 can be formed by appropriate means such as masking in the step of forming the reflective film 5.

Here, as the material of the transparent block bodies 8a and 8b, various materials other than glass such as quartz can be used as long as they are transparent media having a high transmittance at the wavelengths of the stimulated emission light 3 and the excitation light beam 2. Can be used, for example
A transparent resin such as an acrylic resin may be used.

Further, as the reflection film 5, the stimulated emission light 3 is used.
At the wavelength of
In addition to the aluminum reflective film, other metals may be used to form the reflective surface by using thin film forming techniques such as plating, vacuum deposition, sputtering, and ion plating. Further, the wavelength of the stimulated emission light 3 may be used. And its reflectivity is high,
Further effects can be expected if the dichroic mirror has wavelength selectivity and has a small reflectance at other wavelengths.

If an antireflection film such as an AR coat is formed on the upper and lower surfaces through which the excitation light 2 and the stimulated emission light 3 pass, the excitation light 2 and the stimulated emission light 3 at the interface can be formed.
Are prevented from being reflected and the excitation light 2 and the like can be efficiently taken into the condenser 8, so that the utilization efficiency of these is further improved.

Further, when a black coating for antireflection is applied on the lower wall surface of the condenser 8 outside the reflection film 5, more specifically, on the lowermost surface facing the photostimulable phosphor 1, the photostimulability is increased. Since multiple reflection of the excitation light 2 with the phosphor 1 can be prevented, the efficiency of taking in the stimulable phosphor 1 can be improved.

Therefore, in this embodiment, the stimulated emission light 3 is surely guided to both end faces of the condenser 8 and taken out as a signal of good quality. In particular, it has the following advantages over the conventional light collector 8.

That is, in the conventional condensing / photoelectric converter 4, when trying to condense a larger amount of stimulated emission light 3, the excitation light beam 2 inevitably condense too. Usually, an optical filter 10 for selectively transmitting the stimulated emission light 3
Is designed to attach importance to the transmittance of wavelengths other than the stimulated emission light 3 in order to block the excitation light beam 2 which is 10 ₃ to 10 ₄ times stronger than the stimulated emission light 3 or the leakage light from the outside. The need arises.

Therefore, it is necessary to sacrifice the transmittance of the stimulated emission light 3 at the wavelength. For example, when a colored glass filter such as BG39 manufactured by Schott is used,
When the transmittance of wavelengths other than the stimulated emission light 3 is to be made smaller than a predetermined value, it is necessary to increase the thickness of the optical filter 10 accordingly, and the transmittance at the wavelength of the stimulated emission light 3 is also small. turn into.

As a result, in the conventional condenser 8, if the influence of the light other than the stimulated emission light 3 is reduced and the quality of the signal is improved, the signal of the stimulated emission light 3 is also reduced. , As a result, I could not expect the improvement of signal quality.

However, in the condenser 8 described above, the condensed excitation light beam 2 passes through the dichroic reflection surface 7, and most of it is emitted to the outside of the condenser 8.
Since a small amount of light reaches the photoelectric converter 4, it is possible to use an optical filter 10 that places importance on the transmittance of the stimulated emission light 3 and the larger amount of the stimulated emission light 3 can be used. Since it is guided to the photoelectric converter 4, a high quality signal can be obtained.

FIG. 7 shows a modification of the condenser 8. In this modified example, the condenser 8 is formed by joining a pair of transparent block bodies 8a and 8b, and a reflecting surface 9 is formed at the interface between the transparent block bodies 8a and 8b, as in the above-described embodiment. To be done.

The reflecting surface 9 is the same aluminum reflecting film as described above, and a slit 9a through which the excitation light 2 can be transmitted is formed in the center thereof. The slit 9a is provided at a position overlapping the slit 6 formed on the lower wall surface in a plan view, and it is desirable that the slit 9a be as narrow as possible.

Therefore, in this modification, the excitation light beam 2 emitted from the upper surface has two slits 6 and 9a.
Through which the stimulable phosphor 1 is excited to emit stimulated emission light 3, and the stimulated emission light 3 is emitted from the slit 6 on the lower wall disposed in the vicinity of the emission surface into the condenser 8. Is taken into.

The stimulated emission light 3 is omnidirectionally emitted from the points (pixels) of the stimulable phosphor 1 at any angle, and the condenser 8 is used.
Since it is taken into the inside, it does not pass through the slit 9a directly inside and is not emitted to the outside of the condenser 8, and almost the entire amount is repeatedly reflected by the reflecting surfaces 9 and 11a of the central portion, both side walls, and the lower wall surface. While being guided to both ends of the condenser 8.

It should be noted that various possible modifications of the above-described embodiment can be similarly applied to the modification shown in FIG. 7 and the embodiments described below. The condenser 8 in FIG.
Another embodiment will be described. The condenser 8 is formed by joining a pair of transparent block bodies 8a and 8b into a prism shape that is long in the scanning line direction. In this embodiment, the transparent block 8a,
8b is formed such that its height increases from one end to the other end of the main scanning line 2a, and the condenser 8 is formed by adhering the sloped portions to each other.

Therefore, in this embodiment, the photostimulable emitted light 3 taken into the condenser 8 from the slit 6 on the lower wall surface is repeatedly reflected by the dichroic reflecting surface 7, both side walls and the reflecting film 5 on the lower wall surface. While being guided to one end surface of the condenser 8.

In the condenser 8 having the above structure, as shown in FIG. 8B, the dichroic reflecting surface 7 may be replaced with the reflecting surface 9 having the slit 9a. is there.

1 and 2 show an embodiment of the present invention. In this embodiment, the radiation image reading device includes two excitation light beam generators 18, a condenser 8 and two condenser surfaces 8a and 8b each having a 45 ° reflecting surface 11a formed therein. Reflective prisms 11, 11, an optical filter 10 joined to each reflective prism 11, and a photoelectric converter 4 such as a photomultiplier tube for converting the stimulated emission light 3 extracted through the optical filter 10 into an electric signal. And a processing unit 19 for processing the output from the photoelectric converter 4, and the stimulable phosphor 1 formed in a sheet shape or a plate shape is orthogonal to the main scanning direction by a precision fine movement table (not shown). Driven in the direction.

The excitation light beam generator 18 includes the excitation light source 2
b, a laser generator 2b, a galvanometer 2c for scanning the laser beam emitted from the laser generator 2b in the main scanning direction, and an fθ lens 2d.

In this embodiment, a semiconductor laser having a wavelength of 780 nm is used as the excitation light source 2b, and the laser beam is scanned by the galvanometer 2c (or polygon mirror) almost in the center of the condenser 8 and the stimulability is increased. By moving the phosphor 1 in a direction orthogonal to the main scanning direction by the precision fine movement table, the entire surface of the stimulable phosphor 1 is scanned.

Since the excitation light beam 2 guided into the condenser 8 is refracted, even if the excitation light beam 2 is scanned at the same speed on the upper surface of the condenser 8, the condenser 8 for the excitation light 2 On the photostimulable phosphor 1 due to internal refraction, the scanning speed becomes slower toward the end of the main scanning line 2a, which causes a problem that the read image is distorted.
It is desirable that the specifications of the lens 2d be determined so that the excitation light beam 2 is scanned at a constant velocity on the upper surface of the stimulable phosphor 1 in consideration of refraction of the excitation light beam 2 in the condenser 8.

In order to cope with the abnormal scanning speed due to the refraction of the excitation light beam 2 in the condenser 8, the fθ lens 2d is a normal one, that is, the condenser 8 in addition to the above. A method in which the excitation light beam 2 scans at a constant speed is used on the upper surface of the above, and the sampling frequency of the A / D converter 12 to be described later is low at the end of the main scanning line 2a and high at the center. It is also possible to use.

On the other hand, the stimulated emission light 3 in a wide angle range collected by the condenser 8 is similarly filtered by the optical filter 10.
The optical filter 1 has a wide angle of incidence with respect to
0 means that the transmittance of the stimulated emission light 3 is high in a wide incident angle range and the transmittance of the wavelengths other than the stimulated emission light 3 is small in a wide incident angle range. It is desirable to use, for example, the characteristics shown in FIG.
A color glass filter BG39 manufactured by Schott Co. can be used.

Here, the condenser 8, the reflection prism 11, the optical filter 10, and the photomultiplier tube 4 can be adhered to each other and adhered to each other with an optical adhesive. It is also possible to make close contact via the liquid medium.

Therefore, in this embodiment, the condenser 8
The stimulated emission light 3 propagating through the inside of the photomultiplier tube 4 is reflected by the reflection prism 11, and only the stimulated emission light 3 is selectively transmitted by the optical filter 10. The light enters the light receiving surface 4a) and is converted into an electric signal.

The outputs from the photomultiplier tubes 4 are added in an analog manner, amplified to a predetermined level by the first stage amplifier 15 of the processing section 19 and the logarithmic amplifier 20, and then A / A.
The image memory 16 is digitally converted by the D converter 12.
Is stored in the CRT, is subjected to image processing later, and is output on a CRT or as a hard copy.

In the above description, the case where the condenser 8 having the dichroic reflecting surface 7 formed so that the height increases toward both ends is used as an example. The same configuration can be achieved by using the optical device 8.

Further, as shown in FIGS. 8 (a) and 8 (b),
Condenser 8 formed to guide stimulated emission light 3 to one end surface
When using, the optical filter 10 and the like may be arranged only on the light collecting surface as shown in FIG. Further, in the above-described embodiments, the case where the photomultiplier tube 4 is arranged at a position orthogonal to the condenser 8 is shown, but the optical filter 10 is directly condensed without using the reflection prism 11. It is also possible to join it to the end face of No. 8 and develop it in the longitudinal direction.

FIG. 11 shows a second embodiment of the present invention. In this embodiment, the photomultiplier tube 4 and the optical filter 10 are optically connected to the condenser 8 via a reflecting prism 11 having two 45 ° reflecting surfaces 11a, 11a.

By adopting such a configuration, the photomultiplier tube 4 can be arranged in parallel with the back surface of the condenser 8, and therefore the device can be further downsized. In this case, when the condenser 8 shown in FIGS. 3 and 7 is used,
As shown in FIG. 12, two photomultiplier tubes 4 and 4 may be arranged in series.

13 and 14 show the third embodiment of the present invention. In this embodiment, the light-collecting efficiency is further improved, and the stimulable phosphor 1 is formed by sandwiching the upper and lower sides of the phosphor layer with glass having a thickness of about 0.5 mm.

On the other hand, the condenser 8 is in a state in which the dichroic reflection surface 7 is reversed in direction, and more specifically, the dichroic reflection surface 7 has its lowest point facing the stimulable phosphor 1. Reflective prisms 11 which are disposed above and below the fluorescent substance 1 and have a 45 ° reflection surface 11a formed therein are adhered to both end surfaces of the upper and lower light collectors 8 and 8.

The reflection prism 11 is composed of the upper and lower condensers 8.
For collecting the stimulated emission light 3 propagated at both ends by the photomultiplier tube 4, and two condensers 8,
It is formed in a vertically long shape so that the end faces of 8 can be bonded at the same time.

Further, the reflecting prism 11 and the photomultiplier tube 4
The optical filter 10 is adhered to the reflection prism 11 between and. These photomultiplier tube 4 and optical filter 1
0 also has a vertically elongated shape.

Therefore, in this embodiment, when the excitation light beam 2 is irradiated from above the condenser 8 arranged above, stimulated emission light 3 is emitted from the front and back surfaces of the stimulable phosphor 1. Since the light is collected by the light collector 8, the light collection efficiency can be further improved.

Furthermore, in the conventional condensing / photoelectric converter 4,
When the condensers 8 are provided above and below the photostimulable phosphor 1, the number of photomultiplier tubes 4 is also required to be doubled, but in this embodiment, the photomultiplier tubes 4 having a large photocathode 4a are used. Since it is sufficient, it is possible to save costs.

In the stimulable phosphor 1, a transparent resin film or the like can be used instead of glass as a material for sandwiching the phosphor layer. Further, since the condenser 8 used on the lower side does not need to transmit the excitation light beam 2, it may be a normal reflecting surface such as aluminum instead of the dichroic reflecting surface 7.

[0088]

As is apparent from the above description, according to the present invention, stimulated emission light can be efficiently guided to the photomultiplier tube and an image with a good S / N can be obtained.

Further, it is possible to eliminate the variation in the light-collecting efficiency due to the location caused by the variation in the medium and the photocathode, and it is possible to obtain a uniform image. Furthermore, since the condenser mirror is not required and the size of the condenser and the photoelectric converter can be reduced, the entire apparatus can be downsized, and space and cost can be saved.

Furthermore, since the slit, the reflecting surface, the optical filter and the photomultiplier tube are integrated, the adjustment can be easily performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a perspective view showing an embodiment of a light collector.

FIG. 4 is a view showing details of a light collector, (a) is a front view,
(B) is a side view.

5A and 5B are explanatory views showing the action of the light collector, in which FIG. 5A is a sectional view and FIG. 5B is an enlarged front view.

FIG. 6 is a diagram showing characteristics of a dichroic anti-slope.

FIG. 7 is a perspective view showing a modified example of FIG.

FIG. 8 is a diagram showing another embodiment of the light collector.

FIG. 9 is a diagram showing characteristics of an optical filter.

10A and 10B are views showing a modified example of FIG. 1, in which FIG. 10A is a perspective view of a main part, and FIG. 10B is a plan view.

FIG. 11 is a view showing a second embodiment of the present invention, (a) is a perspective view and (b) is a plan view.

FIG. 12 is a plan view showing a modified example of FIG.

13A and 13B are views showing a third embodiment of the present invention, in which FIG. 13A is a plan view and FIG. 13B is a front view.

FIG. 14 is an enlarged perspective view of a main part of FIG.

FIG. 15 is a diagram showing a conventional example.

FIG. 16 is a diagram showing a conventional light collector.

FIG. 17 is a diagram showing a condenser mirror.

[Explanation of symbols]

 1 Photostimulable phosphor 2 Excitation light 2a Main scanning line 3 Photostimulated emission light 4 Photoelectric converter 4a Light receiving surface 5 Reflective film 6 Slit 7 Dichroic reflection surface 8 Condenser 8a, 8b Transparent block 9 Reflective surface 9a Slit 10 Optical filter 11 Reflective prism 11a Reflective surface 12 A / D converter

Claims (20)

[Claims] 1. A stimulable luminescent light emitted by irradiating excitation light (2) to a stimulable phosphor (1) which has absorbed a part of radiation energy transmitted through a subject and accumulated as a latent image. A radiation image reading device for obtaining radiation image information by converting 3) into an electric signal by a photoelectric converter (4), which collects the stimulated emission light (3) and guides it to the photoelectric converter (4). As a means, it is formed in a block shape by a transparent member and is installed substantially parallel to the main scanning line (2a) of the excitation light (2), and the side surface and the lower wall surface thereof reflect the stimulated emission light (3). A reflective film (5) is provided, and a slit (6) for transmitting the excitation light (2) and the stimulated emission light (3) is provided in the substantially central portion of the lower wall surface, and inside the main film, a slit (6) is provided. The height of the scanning line (2a) gradually increases from the center to both ends. The radiation image reading apparatus concentrator dichroic reflecting surfaces (7) is formed (8) is used. 2. The radiation image reading apparatus according to claim 1, wherein the dichroic reflection surface (7) of the condenser (8) is gradually moved from one end of the main scanning line (2a) to the other end thereof. A radiation image reading apparatus formed so as to increase in height. 3. The dichroic reflecting surface (7) has a wavelength band of at least 350 nm to 500 nm,
A multilayer reflective surface having a reflectance of 90% or more.
Alternatively, the radiation image reading device according to item 2. 4. The concentrator (8) comprises two transparent block bodies (8a, 8) having a dichroic reflecting surface (7) as an interface.
The method according to claim 1, wherein b) is joined by an optical adhesive.
The radiographic image reading device described in 2 or 3. 5. The concentrator (8) comprises, instead of the dichroic reflection surface (7), a reflection surface (9) for reflecting the excitation light (2) and the stimulated emission light (3), The excitation light (2) and the stimulated emission light (3) are provided substantially in the center of the surface (9) in parallel with the main scanning line (2a).
The radiographic image reading device according to claim 1 or 2, wherein a slit (9a) for transmitting the light is formed. 6. The light collector (8) according to claim 5, wherein the two transparent block bodies (8a, 8b) having the reflecting surface (9) as an interface are joined by an optical adhesive. Radiation image reading device. 7. The both end surfaces or one end surface of the light collector (8) is optically connected directly to the light receiving surface (4a) of the photoelectric converter (4). 4. The radiation image reading device according to 4. 8. The transmittance between the light collector (8) and the photoelectric converter (4) at the wavelength of the excitation light (2) is low, and the transmittance at the wavelength of the stimulated emission light (3) is high. High optical filter (10)
The radiographic image reading device according to claim 1, wherein the radiographic image reading device is provided. 9. A photoelectric converter (4) is disposed in the vicinity of the light collector (8) at a substantially right angle, and an end face of the light collector (8) and a light-receiving surface of the photoelectric converter (4) ( 4a) is optically connected via a reflecting prism (11) having a 45 ° reflecting surface (11a).
The radiographic image reading device described in 3 or 4. 10. A photoelectric converter (4) is disposed in the vicinity of the light collector (8) at a substantially right angle, and the end face of the light collector (8) and the light receiving of the photoelectric converter (4). The surface (4a) is a reflection prism (11) having a reflection surface (11a) of 45 °, a transmittance of the excitation light (2) at a low wavelength, and a transmittance of the stimulated emission light (3) at a wavelength. The radiographic image reading device according to claim 1, 2, 3, 4, 5, or 6, which is optically connected through an optical filter (10) having a high height. 11. The photoelectric converter (4) is arranged substantially parallel to the light collector (8), and the end face of the light collector (8) and the light-receiving surface (4a) of the photoelectric converter (4). Are optically connected via a reflecting prism (11) having two 45 ° reflecting surfaces (11a).
Alternatively, the radiation image reading device according to item 2. 12. The photoelectric converter (4) is arranged substantially parallel to the light collector (8), and the end face of the light collector (8) and the light receiving surface ( 4a) is a reflection prism (11) provided with two 45 ° reflection surfaces (11a), and has a low transmittance of the wavelength of the excitation light (2) and a transmission of the wavelength of the stimulated emission light (3). The radiation image reading apparatus according to claim 1, 2, 3, 4, 5, or 6, which is optically connected through an optical filter (10) having a high rate. 13. The optical filter (10) is 400 n
13. A color glass filter having a transmittance of 80% or more in a wavelength band of m to 450 nm.
The radiographic image reading device described. 14. The radiation image reading apparatus according to claim 1, wherein the reflection film (5) of the light collector (8) is an aluminum vapor deposition film. 15. The reflection film (5) of the condenser (8) has a high reflectance at the wavelength of the stimulated emission light (3) and a low reflectance at the wavelength of the excitation light (2). 14. The radiation image reading device according to claim 1, wherein the radiation image reading device is a dichroic reflective film. 16. The lower surface of the light collector (8), which faces the photostimulable phosphor (1), is painted black to prevent multiple reflection of the excitation light (2). The radiation image reading device according to any one of claims 1 to 15. 17. Slits (6, 9) of said collector (8).
The antireflection film is provided in part (a), and the transmittance of light having a wavelength of excitation light (2) and light having a wavelength of stimulated emission light (3) is increased. The radiographic image reading device according to. 18. The photostimulable phosphor (1) comprises a transparent substrate, a phosphor layer, and a transparent protective film, and the condenser (8) comprises a photostimulable phosphor (1). The radiation image reading device according to any one of claims 1 to 17, wherein the radiation image reading device is arranged on the front and back sides of the stimulable phosphor (1) with a photolithography member interposed therebetween. 19. The main scanning speed of the excitation light (2) is increased toward the end of the scanning line.
The radiation image reading device according to claim 8. 20. An A / D converter (12) for digitally converting the output from the photoelectric converter (4), wherein the sampling frequency of the A / D converter (12) goes to the end of the scanning line. 20. The radiation image reading apparatus according to claim 1, wherein the radiation image reading apparatus is lowered according to the above.