JP3636787B2 - Radiation image reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation image reading apparatus that reads a radiation image from a stimulable phosphor sheet on which a radiation image is accumulated and recorded, and more particularly, a radiation image suitable for reading a radiation image from both sides of a stimulable phosphor sheet. The present invention relates to a reading device.
[0002]
[Prior art]
In various fields, a recorded radiation image is read to obtain an image signal, and an appropriate image process is performed on the image signal, and then the image is reproduced and recorded. For example, an X-ray image is recorded using a film having a low gamma value designed to be adapted for later image processing, and the X-ray image is read from the recorded film and converted into an electrical signal. A system capable of obtaining a reproduced image with good image quality performance such as contrast, sharpness, graininess, etc. by performing image processing on this electrical signal (image signal) and then reproducing it as a visible image on a copy photograph or the like It has been developed (see Japanese Patent Publication No. 61-5193).
[0003]
In addition, when the applicant applies radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a part of the radiation energy is accumulated, and when irradiated with excitation light such as visible light thereafter, it accumulates. Using a stimulable phosphor (stimulable phosphor) that emits a quantity of stimulated emission light according to the energy that is emitted, a radiation image of a subject such as a human body is once photographed and recorded on a sheet-like stimulable phosphor The stimulable phosphor sheet is scanned with excitation light such as laser light to generate stimulated emission light, and the obtained stimulated emission light is photoelectrically read to obtain an image signal. Based on this image signal, A radiation recording / reproducing system for outputting a radiographic image of a subject as a visible image on a recording material such as a photographic photosensitive material or a CRT has already been proposed (Japanese Patent Laid-Open No. 55-12429, etc.).
[0004]
On the other hand, as a method for photoelectrically reading the above-described stimulable light, the above-mentioned photoelectric reading means is arranged on both sides of the stimulable phosphor sheet, and the excitation light is scanned only on both sides or one side of the stimulable phosphor sheet. A double-sided condensing reading method has been proposed in which the photostimulated luminescence emitted by the excitation light scanning is photoelectrically read from both sides of the stimulable phosphor sheet (for example, Japanese Patent Laid-Open No. 55-87970). Such a double-sided condensing reading method is one in which one radiation image is accumulated and recorded on the stimulable phosphor sheet, and the stimulated emission light is condensed from both sides of the stimulable phosphor sheet. The light collection efficiency is improved and the S / N ratio is further improved.
[0005]
In the double-sided condensing reading method disclosed in the above Japanese Patent Application Laid-Open No. 55-87970, a stimulable phosphor sheet is formed by laminating a stimulable phosphor on the surface of a transparent support, and the transparent phosphor sheet is formed on a transparent holder. A stimulable phosphor sheet on which a radiation image is accumulated and recorded is mounted, and photoelectric reading means are arranged above and below it. That is, the photoelectric reading means arranged on the holder reads the photostimulated luminescence emitted from the surface of the stimulable phosphor sheet, and the photoelectric reading means arranged below the holder reads the back surface of the stimulable phosphor sheet. The stimulated emission light emitted from is read.
[0006]
On the other hand, the stimulable phosphor sheet is not a perfect plane, and its leading edge or trailing edge is curled to some extent. When the radiation image is read in a state where the sheet is curled in this way, unevenness occurs in the image when the curled portion comes into contact with the condensing guide or is suppressed by the conveying roller. Therefore, a method has been proposed in which the sheet is stably sub-scanned by pressing the sheet against a surface opposite to the side irradiated with the excitation light and conveying the sheet. However, when performing the above-described double-sided reading, since it is necessary to provide a condensing guide on both sides of the sheet, the sheet cannot be pressed against the surface opposite to the side irradiated with the excitation light.
[0007]
For this reason, the sheet is guided by a guide that sandwiches the conveyed sheet from the front and back, and the flatness of the sheet is maintained. When such a guide is used, a slit extending along the main scanning direction of the stimulable phosphor sheet is provided in the guide, and the stimulable phosphor sheet is scanned through the slit with the excitation light, and the light collecting guide is It is provided in parallel with the slit, and the stimulated emission light emitted from the stimulable phosphor sheet is photoelectrically detected through this slit.
[0008]
[Problems to be solved by the invention]
However, since the slit is provided in parallel to the leading edge of the stimulable phosphor sheet, if the leading edge of the sheet is curled, when the sheet returns to the guide through the slit, The leading edge collides with the end of the slit, and there is a possibility that reading unevenness occurs in the obtained image due to the impact generated on the sheet at the time of the collision. In the worst case, the sheet rides out of the guide from the slit, and the sheet cannot be correctly conveyed.
[0009]
In view of the above circumstances, an object of the present invention is to provide a radiographic image reading apparatus in which a conveyed stimulable phosphor sheet does not collide with an end of a slit or come off a guide.
[0010]
[Means for Solving the Problems]
A radiographic image reading apparatus according to the present invention is an apparatus for reading a radiographic image by guiding a stimulable phosphor sheet by a guiding means such as the guide described above.
The slit of the guide means forms a predetermined angle with respect to the leading edge of the sheet to be sub-scanned, and the main scanning of the excitation light is performed along the slit having the predetermined angle.
[0011]
Here, the predetermined angle means that two corners formed by the leading edge of the sheet parallel to the sub-scanning direction and the side edge of the sheet perpendicular to the sub-scanning direction do not pass through the slit at the same time. An angle.
[0012]
【The invention's effect】
In the radiographic image reading apparatus according to the present invention, the slit of the guide means has an angle so that the two corners at the leading edge of the sheet do not pass through the slit at the same time. Since one of the corners at the leading edge is always sandwiched from above and below by the guiding means, curling of the leading edge of the sheet passing through the slit is suppressed, so that when the leading edge of the sheet returns from the slit into the guiding means, the sheet Can be prevented from colliding with the end of the slit or coming off the guide means from the slit. Therefore, it is possible to stably convey the sheet by suppressing the sheet deflection caused by the collision of the leading edge of the sheet with the end of the slit, and it is possible to eliminate image unevenness due to the sheet contacting.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0014]
FIG. 1 is a diagram showing an embodiment of a radiation image reading apparatus according to the present invention. FIG. 1 is a diagram showing a radiation image reading apparatus for performing double-sided reading. A stimulable phosphor sheet on which a radiographic image is accumulated and recorded by a radiographic image recording apparatus (not shown) is set at a predetermined position of the radiographic image reading apparatus shown in FIG.
[0015]
The stimulable phosphor sheet 1 is transported by transport means such as an endless belt (not shown), and is transported between guide plates 20 and 21 for guiding the stimulable phosphor sheet 1. Above the sheet 1, a laser light source 10 that emits a light beam 11 that is excitation light, and a rotary polygon mirror 12 that reflects and deflects the light beam 11 and is rotated by a motor (not shown) that performs main scanning of the sheet 1 are arranged. Has been. Further, above the position where the light beam 11 is scanned, a condensing guide 14a for condensing the stimulated emission light emitted from the scanning of the light beam 11 is disposed close to the position, and below the position. , A condensing guide 14 b that condenses the photostimulated luminescent light from below is arranged perpendicular to the sheet 1. The light collecting guides 14a and 14b are connected to photomultipliers (photomultiplier tubes) 15a and 15b for photoelectrically detecting the stimulated emission light, respectively. The photomultipliers 15a and 15b are connected to logarithmic amplifiers 16a and 16b. The logarithmic amplifiers 16a and 16b are further connected to A / D converters 17a and 17b. Each A / D converter 17a and 17b is a storage device. Connected to 18.
[0016]
Note that the guide plates 20 and 21 are arranged with an interval through which the stimulable phosphor sheet 1 can pass. For example, when the thickness of the stimulable phosphor sheet 1 is 0.5 mm, the interval is 0. It is arranged to be about 7 mm. In addition, slits 20A and 21A are formed in the guide plates 20 and 21, and introduction portions 20B and 21B are formed around the slits 20A and 21A so that the sheet 1 can easily pass therethrough (the slit 21A and the introduction portion). 21B is omitted in the drawing). Further, the slits 20 </ b> A and 21 </ b> A are formed to be inclined at a predetermined angle with respect to the conveyance direction of the sheet 1. This predetermined angle is an angle at which two corners formed by the leading edge of the sheet 1 and the side edge of the sheet 1 perpendicular to the conveying direction do not pass through the slits 20A and 21A at the same time. In the present embodiment, the slits 20A and 21A are formed such that the longitudinal direction is 400 mm and the short direction is 10 mm.
[0017]
A stimulable phosphor sheet 1 on which a radiographic image of a subject is accumulated and recorded is set on a conveying means (not shown). At this time, the sheet 1 is set so that the surface on which the phosphor layer is provided faces upward. The stimulable phosphor sheet 1 set at this predetermined position is conveyed by the conveying means into the space between the guide plates 20 and 21, and is conveyed in the direction of the arrow Y while being guided by the guide plates 20 and 21 (sub-scanning). ) On the other hand, the light beam 11 emitted from the laser light source 10 is reflected and deflected by a rotating polygon mirror 12 driven by a motor (not shown) and rotated at high speed in the direction of the arrow, and the sheet 1 is subjected to main scanning in the X ′ direction along the slits 20A and 21A. To do. The main scanning of the sheet 1 is performed in order from the leading edge of the sheet 1 conveyed to the slits 20A and 21A.
[0018]
From the location of the sheet 1 irradiated with the light beam 11, the stimulated emission lights 13a and 13b having a light amount corresponding to the stored and recorded radiographic image information (here, the stimulated emission lights 13a and 13b are respectively emitted from the sheet 1). Diverges from above and below). This stimulated emission light 13a is guided by a condensing guide 14a and is detected photoelectrically by a photomultiplier (photomultiplier tube) 15a. The photostimulated emitted light 13a that has entered the condensing guide 15a from the incident end face repeatedly undergoes total internal reflection inside the condensing guide 14a, exits from the exit end face, is received by the photomultiplier 15a, and represents a radiation image. The amount of the stimulated emission light 13a is converted into an electric signal by the photomultiplier 15a. Similarly, the stimulated emission light 13b is guided by a light collecting guide 14b and is detected photoelectrically by a photomultiplier (photomultiplier tube) 15b.
[0019]
Analog output signal SA output from the photomultiplier 15a is inputted is logarithmically amplified by the logarithmic amplifier 16a to the A / D converter 17a, is entered where it is converted into digital image signals S ₁ to the storage medium 18 The Similarly, photomultiplier 15b analog output signal SB output from the inputted is logarithmically amplified by a logarithmic amplifier 16b to the A / D converter 17b, a storage medium where it is converted into a digital image signal S ₂ Input to 18. Here, in the present embodiment, since the light beam 11 performs main scanning at a predetermined angle θ with respect to the sheet 1, the obtained image signals S ₁ and S ₂ are processed and stored. It is necessary to be able to view the image recorded on the phosphor sheet 1 in a straight line. For this reason, these two image signals S ₁ and S ₂ are subjected to gradation processing and processing for enabling the image to be viewed normally in an image processing means (not shown), and thereafter allowed to be reproduced in a reproducing means such as a laser printer or CRT. Reproduced as a visual image.
[0020]
Here, the stimulable phosphor sheet 1 is not completely flat, and the leading edge and the trailing edge thereof are curled. If there are many curls, the size is about 3 mm. Therefore, if the slit 20A ′ is parallel to the leading edge of the sheet 1 as in the conventional guide plate 20 ′ shown in FIG. 2, the leading edge of the sheet 1 that has passed through the slit 20A ′ enters the guide plate 20 ′ again. Sometimes, it collides with the end of the slit 20A ', and there is a possibility that reading unevenness occurs in the obtained image due to the impact generated on the sheet 1 at the time of the collision. In the worst case, the sheet 1 rides out of the guide 20 'from the slit 20A', and the sheet 1 cannot be correctly conveyed.
[0021]
Since the radiographic image reading apparatus according to the present invention is provided with the slits 20A and 21A inclined at the predetermined angle θ as described above with respect to the leading end of the conveyed sheet 1 as shown in FIGS. When conveyed into 20A, 21A, one corner 1A at the leading end of the sheet 1 is first conveyed into the slits 20A, 21A. In this state, since the other corner 1B of the sheet 1 is guided by the guide plates 20 and 21, even if the leading edge of the sheet 1 is curled, the degree of curling is suppressed. Further, after one corner 1A is conveyed again into the guide plates 20 and 21, the other corner 1B is conveyed into the slits 20A and 21A. In the state within 21A, since one corner 1A of the sheet 1 is guided by the guide plates 20 and 21, even if the leading edge of the sheet 1 is curled, the degree of curling is suppressed. It becomes.
[0022]
Therefore, in the radiographic image reading apparatus according to the present invention, even when the leading edge of the sheet 1 conveyed to the slits 20A and 21A is curled, the degree of curling is suppressed, so the leading edge of the sheet 1 is slit. When returning from 20A and 21A into the guide plates 20 and 21, it is possible to prevent the leading edge of the sheet 1 from touching and colliding with the ends of the slits 20A and 21A or coming off the guide plates 20 and 21. Therefore, the sheet 1 can be stably conveyed by suppressing the deflection of the sheet 1 caused by the front end of the sheet 1 colliding with the ends of the slits 20A and 21A, and the unevenness of the image due to the contact of the sheet 1 can be eliminated. be able to.
[0023]
In this embodiment, since the introduction portions 20B and 21B are formed in the slits 20A and 21A, the sheet 1 is easily returned from the slits 20A and 21A into the guide plates 20 and 21.
[0024]
In the above-described embodiment, the stimulable phosphor sheet 1 is scanned by the laser light emitted from one laser light source 10, but the present invention is not limited to this, and as shown in FIG. Are provided with laser light sources 10a and 10b and rotating polygon mirrors 12a and 12b, respectively, on the front side and the back side of the stimulable phosphor sheet 1, and light beams 11a and 11b are scanned on both sides of the stimulable phosphor sheet 1 to shine. The exhausted light may be read to obtain _two image signals S ₁ and S ₂ .
[0025]
Further, in the above-described embodiment, the slits 20A and 21A are formed in the guide plates 20 and 21 so as to form a predetermined angle with respect to the front end of the sheet 1, but for example, as shown in FIG. An oblique member 22 having a predetermined angle θ added to the front end of the sheet 1 may be provided in a conventional slit 20A ′ parallel to the front end of the first sheet. Even when such an oblique member 22 is provided, the leading edge of the sheet 1 is guided from the slits 20A and 21A because curling of the leading edge of the sheet 1 is suppressed as in the slits 20A and 21A shown in FIGS. When returning to the inside of the plates 20 and 21, it is possible to prevent the sheet 1 from touching and colliding with the ends of the slits 20A and 21A or coming off the guide plates 20 and 21. Therefore, it is possible to stably convey the sheet 1 while suppressing the deflection of the leading edge of the sheet 1 and to eliminate image unevenness due to the sheet 1 being touched.
[0026]
In the above-described embodiment, an apparatus for reading a radiation image from both sides of the stimulable phosphor sheet has been described. However, the present invention is not limited to this, and excitation light is emitted from one side of the stimulable phosphor sheet. The radiation image reading apparatus according to the present invention can be applied even when irradiation is performed and the stimulated emission light is detected only from one side.
[Brief description of the drawings]
FIG. 1 is a view showing a radiation image reading apparatus according to an embodiment of the present invention. FIG. 2 is a view showing a conventional guide plate. FIG. 3 is a guide plate used in the radiation image reading apparatus according to an embodiment of the invention. FIG. 4 is a diagram illustrating another radiographic image reading apparatus according to an embodiment of the present invention. FIG. 5 is a diagram illustrating another example of a slit.
1 Storage phosphor sheet
10 Laser light source
11 Laser light
12 Mirror
13a, 13b Photoluminescent light
14a, 14b Light guide
15a, 15b Photomultiplier
16a, 16b logarithmic converter
17a, 17b A / D converter
18 Storage media
20, 20 ', 21 Guide plate
20A, 20A ', 21A Slit
20B, 21B introduction
22 Diagonal member

Claims (1)

By means of guiding means for main-scanning the stimulable phosphor sheet on which radiation images are accumulated and recorded with excitation light, and having a slit extending along the main-scanning direction at the main-scanning position and guiding the sheet from above and below The sheet is guided and moved in the sub-scanning direction with respect to the excitation light to irradiate the sheet with the excitation light in a two-dimensional manner, and emitted from both sides of the sheet by the irradiation of the excitation light. In the radiation image reading apparatus for obtaining an image signal representing the radiation image by photoelectrically detecting the stimulated emission light carrying the radiation image by a photoelectric detection means,
A radiation image reading apparatus, wherein the slit of the guide means forms a predetermined angle with respect to the leading edge of the sub-scanned sheet, and the excitation light is main-scanned along the slit having the predetermined angle.

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