JP2002107851A - Radiographic image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a radiographic image reader small-sized, which reads image information out of both the surfaces of an accumulative phosphor sheet, without lowering light convergence efficiency. SOLUTION: As a photoelectric read means, which is arranged on the surface of the accumulative phosphor sheet opposite to a surface irradiated with excitation light, this reader is equipped with a light-converging guide 15b, a photomultiplier 16b which is connected to the projection end surface of the light-converging guide 15b, and a light-converging mirror 17b. The light-converging guide 15b is arranged, having its incidence end surface 18 slanted to the sheet surface and the light-converging mirror 17B is fixed to one end of the light-converging guide 15b so that stimulated phosphorescent light M2 is reflected to the incidence end surface 18b of the light-converging guide 15b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stimulable phosphor sheet which is scanned with excitation light to emit stimulating light emitted from the stimulable phosphor sheet. The present invention relates to a radiation image reading device that reads by photoelectric reading means provided on each side.

[0002]

2. Description of the Related Art When radiation (X-ray, α-ray, β-ray, γ-ray, electron beam, ultraviolet ray, etc.) is irradiated, a part of this radiation energy is accumulated. Using a stimulable phosphor (stimulable phosphor) that emits stimulable light in response to the applied energy, the radiation image information of a subject such as a human body is stored with a sheet-shaped stimulable phosphor layer. Once recorded on the phosphor sheet, the stimulable phosphor sheet is scanned with excitation light such as laser light to generate stimulated emission light, and the resulting stimulated emission light is photoelectrically read to obtain an image signal. A radiation image recording / reproducing system that outputs a radiation image of a subject as a visible image to a recording medium such as a photographic photosensitive material or a display device such as a CRT based on the image signal is known (Japanese Patent Application Laid-Open No. 55-12429, No. 56-11395, No. 56-113
No. 97).

As a method for reading image information recorded from a stimulable phosphor sheet, double-side reading for separately reading stimulated emission light emitted from both sides of the sheet is known. For this double-sided reading, for example, a sheet formed by laminating a stimulable phosphor layer on the surface side of a transparent support is used as the stimulable phosphor sheet, and excitation light scanning is performed on the sheet from the stimulable phosphor layer side. The stimulated emission light emitted from both the stimulable phosphor layer side and the transparent support side of the stimulable phosphor sheet by the excitation light scanning is read by photoelectric reading means provided on both sides of the stimulable phosphor sheet. It is read separately (JP-A-8-116485, etc.). According to such double-sided reading, signals obtained from both sides are added to each other in correspondence with pixels, so that light-collecting efficiency is improved and noise components are averaged. / N ratio can be improved.

Further, in the conventional double-sided reading, as in the case of the above-mentioned publication, both sides of the stimulable phosphor sheet are provided along the excitation light scanning lines on the stimulable phosphor sheet. And a head-on type photomultiplier having an annular light receiving surface connected to the exit end face of the condensing guide. It is a general practice to dispose photoelectric reading means and read the stimulated emission light by these photoelectric reading means. The condensing guide is for guiding stimulated emission light coming from the incident end face to the photoelectric reading and reading means, and is formed by a light guide sheet made of acrylic or the like, and is formed by bundling a number of optical fibers. There are various embodiments. At this time, the condensing guide disposed on the surface (rear surface) opposite to the surface irradiated with the excitation light is used to efficiently receive stimulated emission light emitted from the excitation light scanning position. Immediately below the position, the incident end face is disposed so as to face parallel to the sheet.

[0005]

However, in order to make the incident end face of the light-collecting guide on the rear surface face parallel to the rear surface of the stimulable phosphor sheet as described above, the light-collecting guide is disposed substantially vertically. However, there is a disadvantage that the arrangement of the light-condensing guide is not flexible and the size of the device is increased.

In order to increase the light-collecting efficiency on the back side, the light-collecting guide on the back side must be arranged sufficiently close to the stimulable phosphor sheet. The light-collecting guide may be used as a stimulable phosphor sheet because the peripheral edge of the device may be in a curled state in which it rises more than the central portion due to passing through a bent conveyance path inside the device or bending habits due to aging and the like. If the distance is too close, there is a problem that the curled leading end portion comes into contact with the light collecting guide when the stimulable phosphor sheet is transported. If the light-collecting guide and the stimulable phosphor sheet come into contact with each other, they will be damaged. Therefore, it is necessary to arrange the stimulable phosphor sheet and the light-collecting guide with a sufficient distance to avoid contact. Is partially sacrificed.

If the light-collecting guide on the back side is arranged so that the incident end face faces parallel to the stimulable phosphor sheet, the surface of the stimulable phosphor sheet is irradiated and transmitted through the stimulable phosphor sheet. The reflected excitation light is reflected by the incident surface of the light-collecting guide, and when the reflected light of the excitation light is incident on the stimulable phosphor sheet again, it excites the periphery of the read pixel (around the excitation light scanning position). When the reflected light of the excitation light is incident on a portion of the phosphor sheet where image reading has not been completed, stimulating light is generated from the reflected light, which causes an increase in flare in the resulting image.

The present invention has been made in view of the above circumstances, and has as its object to provide a radiation image reading apparatus that can be configured to be smaller in size as compared with the related art without lowering the light collection efficiency.

[0009]

According to the radiation image reading apparatus of the present invention, the stimulable phosphor emitted from the stimulable phosphor sheet is scanned by exciting the surface of the stimulable phosphor sheet with excitation light. In a radiation image reading apparatus which is read by photoelectric reading means provided on each of the front side and the back side of the stimulable phosphor sheet, the photoelectric reading means provided on the back side of the stimulable phosphor sheet comprises: A photoelectric conversion unit that photoelectrically converts the emitted light, and one end surface is provided near the back surface of the sheet, and the other end surface is optically connected to the photoelectric conversion unit. A light-collecting guide for guiding the light to the other end surface and a light-collecting mirror for reflecting the stimulated emission light toward the one end surface of the light-collecting guide are provided.

Here, it is preferable that the condensing mirror transmits the excitation light and reflects the stimulated emission light.

Further, the one end face of the light collecting guide is
It is preferable that the stimulable phosphor sheet is disposed so as to have a predetermined angle with respect to the back surface of the stimulable phosphor sheet. here,
“Having a predetermined angle” means that the one end face of the light-collecting guide does not face parallel to the back surface of the stimulable phosphor sheet.

In the radiation image reading apparatus, there is provided a transporting means for relatively transporting the stimulable phosphor sheet to the photoelectric reading means, and the one end face of the light-collecting guide is provided on the stimulable phosphor sheet. It is desirable to be disposed toward the downstream side in the transport direction. In this case, the one end face is oriented such that the center thereof is located downstream of the excitation light scanning position in the sheet conveying direction, that is, the perpendicular line at the center of the one end face is located downstream of the excitation light scanning position of the sheet. Further, it is preferable that the perpendicular line at the end of the one end face on the upstream side in the sheet conveyance direction extends further downstream than the excitation light scanning position in the sheet conveyance direction. More preferably, it is performed. In this case, the condensing mirror may be disposed downstream of the condensing guide in the sheet conveying direction.

It is preferable that the light collecting mirror is fixed to a part of the light collecting guide such that a mirror surface of the light collecting mirror is continuous with the one end surface of the light collecting guide. .

[0014]

According to the radiation image reading apparatus of the present invention,
A photoelectric reading unit disposed on the back side of the stimulable phosphor sheet, a photoelectric conversion unit for photoelectrically converting the stimulating light, and one end surface is provided near the back surface of the sheet, and the other end surface is provided. A light-collecting guide optically connected to the photoelectric conversion means for guiding the stimulated emission light from the one end surface to the other end surface, and directing the stimulated emission light to the one end surface of the light collection guide. And a light-collecting mirror that reflects light without having to converge the light-collecting guide directly below the excitation light scanning position of the sheet, as in the past, without having one end face parallel to the sheet surface. As a result, the light-collecting guide can be arranged at an angle to the sheet surface, and the size of the apparatus can be reduced. In addition, since the light-collecting mirror is provided, even if the end portion of the light-collecting guide is made thinner than the conventional one, it is possible to obtain light-collecting efficiency equal to or higher than that of the conventional light-collecting guide. Cost can be reduced.

If the condensing mirror transmits or absorbs the excitation light and reflects the stimulated emission light, the excitation light transmitted through the sheet is reflected by the condensing mirror to the condensing guide. Can be prevented, and flare in the obtained reproduced image can be suppressed.

The one end surface of the light-collecting guide is disposed so as to have a predetermined angle with respect to the back surface of the stimulable phosphor sheet. If the stimulable phosphor sheet is disposed so as to prevent the excitation light reflected on one end face of the light-collecting guide from being incident on a portion where reading of the stimulable phosphor sheet has not been completed.

When there is a gap between one end surface of the light-collecting guide and the mirror surface of the light-collecting mirror, there is stimulated emission light passing through the gap. If the light-collecting mirror is fixed to a part of the light-collecting guide so that the mirror surface of the light-collecting mirror is continuous with the one end surface of the light-collecting guide, the stimulated emission light can be collected more efficiently. As a result, an image signal with a good S / N can be obtained by increasing the light collection efficiency.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing an example of a stimulable phosphor sheet that can be read on both sides and is used in the radiation image reading apparatus of the present invention. The illustrated stimulable phosphor sheet 1 includes a sheet-shaped transparent support 1a and a stimulable phosphor (for example, BaFBrI: Eu) layer 1b laminated on the surface side of the transparent support 1a. . As the transparent support 1a,
For example, a thin transparent plastic film having a thickness of 100 to 500 μm having flexibility can be used. However, the present invention is not limited to this, and other various transparent supports such as a glass transparent support can be used. Although not shown, the surface of the stimulable phosphor layer 1b has a thickness of 2 to 50 μm.
m of the transparent protective layer.

Since the stimulable phosphor sheet 1 uses a transparent support that transmits stimulable luminescent light as a support, the stimulable luminescent light is applied to the stimulable phosphor layer 1b and the support 1a, respectively. , And thus the stimulating light can be read from both sides of the sheet 1.

Next, an embodiment of the radiation image reading apparatus of the present invention will be described with reference to FIG. 2 which is a perspective view showing the embodiment.

The reading device shown in FIG. 1 emits radiation transmitted through a subject in a photographing unit (not shown), and reads the stimulable phosphor sheet 1 on which radiation image information of the subject is recorded.
This is a device for reading the radiation image information from both the front surface and the back surface of the sheet 1. Here, the surface,
The back surface is simply a distinction for convenience of distinguishing and describing one surface and the other surface, and either surface may be referred to as a front surface. In the present embodiment, the surface on the side irradiated with the excitation light during image reading is referred to as the front surface, and the surface on the back side is referred to as the back surface.

In the illustrated reader, two endless belts 19 are rotated by a motor (not shown).
A stimulable phosphor sheet (hereinafter, referred to as a sheet) 1 is set on the endless belts 19a and 19b, and is conveyed in the direction of arrow Y by the endless belts 19a and 19b. Above the sheet 1 to be conveyed, a laser light source 11 that emits laser light L as excitation light
And a rotary polygon mirror 13 that is rotated by a motor (not shown) to reflect and deflect the laser light L to scan the sheet 1 in the main direction.
And a scanning lens 14 for focusing the laser beam L on the sheet.
And are arranged. In addition, as the laser light source 11, in addition to a single semiconductor laser, a semiconductor-pumped solid-state laser SHG laser, a MOPA laser including a semiconductor laser and an amplifier for amplifying the laser output, and a semiconductor laser combined light source may be used. .

Above the surface (upper surface side in the drawing) of the sheet 1 on which the laser light L is scanned, a light-collecting light M1 emitted from the surface of the sheet by the scanning of the laser light L is condensed. The guide 15a has its incident end face (light receiving face) 18a
Is disposed on the upstream side of the scanning position of the laser light L in the sheet conveying direction so as to be close to the conveyance path of the sheet 1 and is located near the condensing guide 15a and at the scanning position of the laser light L. On the downstream side in the sheet conveying direction, the sheet 1
The stimulated emission light M1 scattered and emitted from the
condenser mirror 17 for reflecting light toward the incident end face 18a
a is provided.

A condensing guide 15b for condensing stimulated emission light M2 emitted from the back surface of the sheet (the lower surface in the figure) is provided below the position where the laser light L is scanned. The sheet 18b is disposed upstream of the scanning position of the laser beam L in the conveying direction of the sheet 1 so as to be close to the conveying path of the sheet 1. Note that this light collection guide 15b
Is inclined with respect to the sheet surface so as to face the downstream side of the sheet 1 in the conveying direction. Further, the stimulated emission light M2 scattered and emitted from the sheet 1 is provided at one end of the light collecting guide 15b on the downstream side in the sheet conveying direction.
Condensing mirror for reflecting toward the incident end face 18b of 15b
17b is fixed. The condensing mirror 17b is formed such that its mirror surface is continuous with the incident end face 18b of the condensing guide 15b, thereby efficiently stimulating the emitted light M2.
Can be collected.

The exit end faces of each of the condensing guides 15a and 15b have
Photomultipliers (photomultiplier tubes) 16a and 16b for photoelectrically detecting the stimulated emission light M1 and M2, respectively, are connected. That is, the photoelectric reading means is constituted by the light collecting guides 15a and 15b, the light collecting mirrors 17a and 17b, and the photomultipliers 16a and 16b. Further, the Foti multipliers 16a and 16b are connected to logarithmic amplifiers 21a and 21b, which are connected to A / D converters 22a and 22b.
A / D converters 22a and 22b are connected to an image processing unit.
Connected to 30.

The light-collecting guides 15a and 15b are formed by molding a light-guiding material such as an acrylic plate, and the linear incident end faces 18a and 18b are formed along the main scanning line on the sheet 1. The light receiving surfaces of the photomultipliers 16a and 16b are coupled to the emission end face formed on the ring. In addition, the incident end face of each of the condensing guides 15a and 15b
Excitation light cut filters (not shown) for preventing the excitation light L from entering are formed on the thin films 18a and 18b. The condensing mirrors 17a and 17b are composed of dichroic mirrors and transmit light in the wavelength range of laser light, which is excitation light, and reflect light in the wavelength range of stimulated emission light. In addition, instead of providing the excitation light cut filters on the incident end faces 18a, 18b of the light collection guides 15a, 15b, photomultipliers 16a,
An excitation light cut filter that absorbs the excitation light may be provided on the light receiving surface 16b. Further, an excitation light cut filter may be provided on both the incident end face of the light collection guide and the light receiving face of the photomultiplier.

Next, the operation of this embodiment will be described. The sheet 1 on which the radiation image of the subject is accumulated and recorded is set at a predetermined position on the endless belt 19a, and the set sheet 1 is conveyed (sub-scan) in the arrow Y direction by the endless belts 19a and 19b. On the other hand, the laser light L, which is the excitation light emitted from the laser light source 11, is reflected and deflected by the rotating polygon mirror 13 driven by a motor (not shown) and rotated at a high speed in the direction of the arrow, and converges on the surface of the sheet 1 by the scanning lens 14. The main surface of the sheet 1d is scanned by scanning at a constant speed. By the main scanning of the laser beam L and the sub-scanning of the sheet 1, the sheet 1 is irradiated with the laser beam L over the entire surface. The laser beam L irradiating the sheet 1 excites the stimulable phosphor layer 1b of the sheet 1, and the photostimulable emission light M1 corresponding to the recorded radiation image information is emitted from the front surface side of the sheet 1; From the back side of the device, the stimulating light M2 corresponding to the recorded radiation image information is emitted.

Some of the stimulated emission light M1 and M2 emitted from the front and back surfaces of the sheet 1 are directly incident on the light-collecting guides 15a and 15b disposed close to the front and back surfaces of the sheet 1, respectively. Part of the light is reflected by the light collecting mirrors 17a and 17b and is collected on the light collecting guides 15a and 15b. The stimulated emission light M1 and M2 condensed on the condensing guides 15a and 15b are guided to photomultipliers 16a and 16b, and are photoelectrically detected by the photomultipliers 16a and 16b. The stimulated emission light M1, M2 that has entered the light-collecting guides 15a, 15b from the incident end faces 18a, 18b is reflected by the light-collecting guides 15a, 15b.
b, the light is emitted from the output end face and received by the photomultipliers 16a and 16b, and the photostimulated light M1 and M2 representing the radiation image information are converted into analog light by the photomultipliers 16a and 16b. It is converted into image signals y1 and y2.

The analog signals y1 and y2 output from the photomultipliers 16a and 16b are converted to logarithmic amplifiers 21a and 21b.
Are amplified logarithmically and converted into logarithmic image signals q1 and q2. The logarithmically amplified logarithmic image signals q1 and q2 are A
/ D conversion circuits 22a and 22b are input to the digital image data Q by sampling at a predetermined sampling period T.
1, Q2, that is, converted into the front image signal Q1 and the back image signal Q2 and input to the addition unit 23.
The two image signals Q1 and Q2 are weighted and added at a predetermined addition ratio so that the pixels correspond to each other.
Output as The addition ratio of the front side and the back side is
A ratio suitable for suppressing noise is used.

FIG. 3A shows the sheet 1 of the radiation image reading apparatus shown in FIG. 2 and the back side of the sheet 1 (downward in the figure).
FIG. 4 is an enlarged cross-sectional view showing a light-collecting guide 15b and a light-collecting mirror 17b provided in the first embodiment. In addition, FIG.
FIG. 2 is a cross-sectional view illustrating a configuration of a condensing guide 45 according to a conventional technique.

As shown in FIG. 3A, the condensing mirror 17b
Is fixed to one end of the light-collecting guide 15b, and both are integrated. The distance l from the sheet 1 is determined by the curl 1s at the sheet tip shown by a dotted line in the drawing.
b. Even if the curl 1s at the leading end of the sheet is not sufficiently contacted, the light is collected by the light collecting guide 15b and the mirror 17b, so that the light collecting efficiency can be improved. In addition, since the light-collecting guide 15b is arranged on the upstream side in the sheet conveying direction indicated by the arrow Y and the incident end face 18b is directed to the downstream side, the excitation light L reflected on the incident end face 18b is Is reflected toward the portion where the image reading is completed (the hatched portion in the figure), and is not irradiated to the portion before the image reading, so that the reflected light of the excitation light L irradiates the portion of the sheet 1 before the image reading. The flare generated by this can be suppressed.

Further, as shown in FIG. 3B, in the prior art, reading of the stimulated emission light from the back side is performed only by the condensing guide 45, and in that case, the condensing light is efficiently condensed. Therefore, in order to dispose the incident end face in parallel with the sheet 1 surface, it is necessary to dispose the condensing guide 45 substantially perpendicular to the sheet 1. As shown in the above embodiment, in the radiation image reading apparatus of the present invention, by using the light collecting guide and the light collecting mirror together, the light collecting guide can be disposed diagonally, and The size can be reduced. Further, when the incident end face of the condensing guide was arranged in parallel with the sheet surface, the excitation light reflected on the incident end face was incident on a portion of the sheet before image reading, and flare occurred. As described above, flare can be suppressed in the present embodiment. FIG. 3 (b)
When the light-collecting guide 45 is arranged in parallel to the sheet surface as shown in FIG. 3, in order to obtain the same light-collecting efficiency as the apparatus of the present invention shown in FIG. FIG.
A thickness t 'larger than the thickness t of the light-collecting guide 15b in (a) was required. That is, the light-collecting guide of the radiation image reading apparatus of the present invention can achieve the same or higher light-collecting efficiency with a smaller thickness than the conventional light-collecting guide, and thus can reduce the cost.

In the above embodiment, an example in which the light-collecting guide and the light-collecting mirror are formed integrally has been described. However, as shown in FIG. They may be formed individually.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the structure of a stimulable phosphor sheet that can be read on both sides.

FIG. 2 is a sectional view showing a schematic configuration of a radiation image reading apparatus according to the present invention.

3A is a partially enlarged cross-sectional view of the radiation image reading apparatus shown in FIG. 2, and FIG.

FIG. 4 is a cross-sectional view showing another embodiment of the photoelectric reading means arranged on the back side of the sheet.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 stimulable phosphor sheet 1 a support 1 b stimulable phosphor layer 1 c back surface 1 d front surface 15 a front-side condensing guide 15 b back-side condensing guide 17 a front-side condensing mirror 17 b back-side condensing mirror 18 a front side End face of the light-collecting guide 18b

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) H04N 1/113 H04N 1/04 104A F term (reference) 2G083 AA03 BB04 CC10 DD13 DD16 DD17 EE10 2H013 AC05 5B047 AA17 AB02 BA01 BB08 BC09 BC11 BC14 BC30 5C072 AA01 BA01 CA06 DA04 DA17 DA21 EA02 HA13

Claims (5)

[Claims] 1. A stimulable luminescent light emitted from a stimulable phosphor sheet by scanning the surface of the stimulable phosphor sheet with excitation light is applied to each of the front side and the back side of the stimulable phosphor sheet. In a radiation image reading apparatus that is read by a disposed photoelectric reading unit, a photoelectric reading unit disposed on a back surface side of the stimulable phosphor sheet performs photoelectric conversion of the stimulated emission light; Is provided adjacent to the back surface of the sheet, the other end surface is optically connected to the photoelectric conversion means, a light-collecting guide for guiding the stimulated emission light from the one end surface to the other end surface, A radiation mirror, comprising: a light-collecting mirror that reflects the stimulating light toward the one end surface of the light-collecting guide. 2. The radiation image reading apparatus according to claim 1, wherein the condenser mirror transmits or absorbs the excitation light and reflects the stimulated emission light. 3. The light-collecting guide according to claim 1, wherein the one end face of the light-collecting guide is disposed so as to have a predetermined angle with respect to a back surface of the stimulable phosphor sheet. Radiation image reading device. 4. A convey means for conveying the stimulable phosphor sheet relatively to the photoelectric reading means, wherein the one end face of the light-collecting guide faces downstream in the conveying direction of the stimulable phosphor sheet. 4. The radiation image reading apparatus according to claim 3, wherein the radiation image reading apparatus is disposed. 5. The light-collecting mirror is fixed to a part of the light-collecting guide such that a mirror surface of the light-collecting mirror is continuous with the one end surface of the light-collecting guide. The radiation image reading device according to any one of claims 1 to 4, wherein