JPH05313263A - Radiation image reader - Google Patents

Abstract

PURPOSE:To provide the radiation image reader which can compatibly improve both sharpness and condensing efficiency without complicating an optical system. CONSTITUTION:This radiation image reader reads accumulated and recorded radiation image information as stimulated luminous light by scanning a radiation image conversion panel 13 accumulated and recorded with the radiation ima9e information with exciting light. The above-mentioned radiation image reader has the radiation image conversion panel 13 having a stimulable phosphor layer 13a constituted of columnar crystals independent by having a specific inclination with the direction normal to the plane of a base, a exciting light projecting means which projects the exciting light from the inclination direction of the columnar crystals constituting the stimulable phosphor layer 13a of the radiation conversion panel 13, a condensing means having the incident end face of the stimulated luminous light disposed to be approximately perpendicular to the direction normal to the plane of the radiation image conversion panel 13 and a photoelectric conversion means for photoelectric conversion of the stimulated luminous light condensed by the condensing means.

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 which scans a radiation image conversion panel on which radiation image information is stored and recorded with excitation light and reads the stored and recorded radiation image information as stimulated emission light. More specifically, it relates to improvement of sharpness and light collection efficiency.

[0002]

Radiation images are used for medical purposes. In such a case, a radiation image conversion panel having a stimulable phosphor layer is used, and the radiation transmitted through the subject is applied to the stimulable phosphor layer of the radiation image conversion panel to correspond to the radiation transmittance of each part of the subject. The radiation energy is stored to form a latent image. Then, by scanning the stimulable phosphor layer with excitation light, the radiation energy accumulated in each part is converted into stimulated emission light, and the intensity of the stimulated emission light is read to obtain image information.

A radiation image conversion panel having a stimulable phosphor layer used for such radiation image conversion needs to have a high radiation absorption rate and a high light conversion rate, and the image obtained has good graininess. However, high sharpness is required.

In such a case, sharpness is improved by making excitation light incident vertically on the radiation image conversion panel and detecting stimulated emission light at a position perpendicular to the radiation image conversion panel.

However, if the excitation light is made to enter the radiation image conversion panel vertically to improve the sharpness, the optical system for focusing cannot be arranged in the vertical position,
There is a problem that the light collection efficiency decreases.

On the contrary, when the condensing optical system is arranged at the vertical position of the panel, there is a problem that it is difficult to make the excitation light perpendicularly enter the panel. Then, when the excitation light is incident on the panel at an angle other than vertical, the apparent light beam diameter on the panel surface becomes large in the sub-scanning direction, which causes a problem that the sharpness in the sub-scanning direction deteriorates.

FIG. 8 is a configuration diagram showing the configuration of a conventional radiation image reading apparatus in consideration of the above points. In this configuration, the excitation light beam emitted from the radiation source 11 is vertically irradiated to the radiation image conversion panel 13 through the dichroic filter 12, and the fluorescence (stimulable fluorescence) emitted at that time is vertically irradiated by the dichroic filter 12. After being received in a certain direction and reflected, the reflected light is condensed by the lens 14, the fluorescence component is further extracted by the filter 15, and the image information is detected by the photoelectric conversion element 16 as an electric signal. That is, the irradiation of the excitation light and the detection of the emitted light are performed vertically to efficiently obtain an image with high sharpness.

[0008]

However, even in the apparatus of such a system, the dichroic filter 12 attenuates the excitation light beam to reduce the light collection efficiency, and the vertical irradiation and the vertical detection are performed. Therefore, there is a problem that the optical system becomes complicated.

The present invention has been made to solve the above problems, and an object thereof is radiation capable of achieving both sharpness improvement and light collection efficiency improvement without complicating the apparatus. It is to realize an image reading device.

[0010]

A means for solving the above-mentioned problems is to scan a radiation image conversion panel on which radiation image information is stored and recorded with excitation light, and use the stored and recorded radiation image information as stimulated emission light. In a radiation image reading device for reading, a radiation image conversion panel having a stimulable phosphor layer composed of independent columnar crystals having a specific inclination with respect to a normal direction of a surface of a support, and a radiation conversion panel Excitation light irradiating means for irradiating excitation light from the tilt direction of the columnar crystals constituting the stimulable phosphor layer, and stimulated emission light arranged so as to be substantially perpendicular to the direction normal to the surface of the radiation image conversion panel. And a photoelectric conversion means for photoelectrically converting the stimulated emission light collected by the light collecting means.

[0011]

In the radiation image reading apparatus of the present invention, the excitation light is incident from the tilt direction of the columnar crystals forming the stimulable phosphor layer of the radiation image conversion panel. As a result, the excitation light is incident with the highest sharpness. Further, the sharpness becomes equal in the main scanning direction and the sub scanning direction.

Then, the photostimulable luminescent light generated in the radiation image conversion panel has an incident end face of the stimulable luminescence light arranged so as to be substantially perpendicular to the normal line direction of the surface of the radiation image conversion panel. It is detected by optical means and converted into an electrical signal. In this way, since the incident end surface of the light collecting means is arranged so as to be substantially perpendicular to the normal line direction of the surface of the radiation image conversion panel, the light collecting efficiency is good.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a fluorescence detection surface of the device of the present invention. In the figure, 13 is the above-mentioned radiation image conversion panel, 21 is a filter for extracting only stimulated emission components of the light from the radiation image conversion panel 13, and 22 is an electrical signal that receives the emitted light that has passed through the filter 21. It is a photodetector that converts to. The photodetector 22 is composed of a combination of the photoelectric conversion elements described above. Reference numeral 23 denotes a light detection surface, and the surface of the filter 21 corresponds to this. Light detection surface 2
3 is arranged so as to be substantially perpendicular to the normal line n of the radiation image conversion panel 13.

The stimulable phosphor layer 13a is composed of independent columnar crystals having a specific inclination with respect to the direction normal to the surface of the radiation image conversion panel 13. In the present embodiment, the inclination θ1 of the columnar crystal needs to be larger than 0 ° and smaller than 90 °, preferably 10 ° to 50 °. The applicant of the present invention has filed an application for such a radiation image conversion panel according to Japanese Patent Application No. 63-129996. In addition, the excitation light is inclined in the tilt direction θ1 of the columnar crystals forming the stimulable phosphor layer 13a of the radiation conversion panel 13.
It is configured to be irradiated from.

The operation of the apparatus configured as described above will be described below. When the excitation light beam is incident on the normal line n of the radiation image conversion panel 13 at an angle of .theta.1 and irradiates the point A on the panel surface, stimulated emission as shown in the figure is generated from around the point A. Then, the emitted light enters the light detection surface 23, which is the incident end surface. The light detection surface 23 is
Since it is a filter surface, the excitation light beam
The reflected light of the light is blocked and only the emitted light passes through the filter 21. The emitted light transmitted through the filter 21 is detected by the photodetector 22.
After being converted into an electric signal by the processing device (not shown)
Image processing and image reconstruction are performed at. The relationship between the columnar crystals and the excitation light beam at this time is as shown in FIG.

In this case, the intensity of the stimulated emission light has an angle dependence. FIG. 3 is a diagram showing the angle-dependent characteristics of stimulated emission light. In the figure, X indicates the normal direction.
A plurality of arrows surrounded by a circle C are emitted light intensity at that angle. That is, the emitted light intensity is highest in the component in the normal direction (θ = 0 °). This is because the stimulated emission light is completely diffused light.

The reflected light of the excitation light beam has a reflection angle θ.
It has been confirmed that the light intensity decreases rapidly as the direction of becomes maximum and deviates from that angle. The reflected light strongly depends on the surface condition of the panel of the radiation image conversion panel 13, and the higher the smoothness, the stronger this tendency (close to specular reflection). Higher smoothness is usually preferable for improving the graininess of the image, but the angle dependence of reflected light appears strongly.
However, as the incident angle θ1 of the excitation light beam is increased, it becomes difficult to reduce the irradiation beam diameter of the light beam, and the surface reflection of the light beam increases and the excitation efficiency increases. The incident angle θ1 is 10 ° to 6 for reasons such as a decrease.
A range of 0 ° is suitable.

Further, as shown in FIG. 4, the sharpness is highest when the light beam incident angle θ 1 coincides with the columnar crystal direction. As described above, according to the embodiment shown in FIG. 1, the emitted light can be detected most efficiently per the detection area of the light detection surface 23, and the influence of the reflected light of the excitation light beam on the filter 23 is also effective. Can be made smaller and the incident light beam
Since there is nothing that hinders the scanning, the photoelectric conversion efficiency of the photodetector 22 can be improved. Further, the sharpness can be improved by irradiating the excitation light beam in independent columnar crystal directions with a specific inclination. In addition, 0
The sharpness is high even in the vicinity of the degree because the beam diameter becomes the minimum at 0 degree. A radiation image conversion panel having a columnar crystal stimulable phosphor layer is suitable for enhancing sharpness because excitation light is less likely to be scattered in the phosphor layer. Furthermore,
The high filling rate of the phosphor also contributes to the enhancement of sensitivity.

FIG. 5 is a block diagram showing an example of the optical system of the device of the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. In FIG. 1, the stimulated fluorescence of the radiation image conversion panel 13 is directly taken into the photodetector 22, but in the case of FIG. 5, it is different in that it is guided to the photodetector 22 by the fiber-shaped photoconductor 31. ing. Reference numeral 32 is a deflection mirror that distributes the incident excitation light beam in the main scanning direction (z direction in the figure). The operation of the apparatus configured as described above will be described below.

The excitation light beam is deflected by the deflection mirror 32 in the main scanning direction (z direction in the figure) and at a certain inclination θ 1 with respect to the normal line direction of the radiation image conversion panel 13. Irradiated on. The sub-scanning is performed by moving the radiation image conversion panel 13 in a direction perpendicular to the main scanning by a driving unit (not shown), and two-dimensional scanning is performed. The radiation image conversion panel 13 emits stimulated emission light when irradiated with the excitation light beam. This emitted light is guided to the photodetector 22 by the photoconductor 31. The photodetection surface in this case is one cross section 33 of the photoconductor 31 and is installed so as to be substantially parallel to the radiation image conversion panel 13 with the scanning line as the center. The length of the light detection surface in the scanning direction (z direction) is designed to be longer than the width of the radiation image conversion panel 13 to prevent a reduction in detection efficiency around the scanning. Since the other cross section of the photoconductor 31 is in close contact with the filter 21 and the other surface of the filter 21 is in contact with the photodetector 22, there is no light loss. The detection efficiency can be improved by using, for example, a plastic fiber bundle as the photoconductor.

FIG. 6 is a configuration diagram showing the overall configuration of another embodiment of the present invention. Although sub-scanning is performed by moving the radiation image conversion panel 13 in the above embodiment,
In the configuration shown in this figure, the sub-scan is realized by fixing the radiation image conversion panel 13 and moving the reading unit 40. Therefore, the radiation image conversion panel 13 is fixed to the left wall surface. And
The movable reading unit 40 includes a sub-scanning motor 50.
It moves in the Y (sub-scanning) direction in the figure by the ball screw 51 driven by, and scans the excitation light in the sub-scanning direction. The excitation light irradiation unit 41 is composed of a light source and a main scanning means such as a galvano mirror or a polygon mirror, and generates excitation light for scanning in the main scanning (perpendicular to the paper surface) direction. FIG. 7 is an explanatory diagram showing the relationship between the tilt of the columnar crystals of the radiation image conversion panel 13 and the excitation light in this example. As shown in this figure,
The excitation light is arranged so as to enter the radiation image conversion panel 13 at an angle substantially equal to the inclination of the columnar crystals.

As described above, a radiation image conversion panel in which the columnar crystals have an inclination on the sub-scanning side is prepared, the incident angle of excitation light is 0 ° with respect to the main scanning direction, and the radiation angle is 0 ° with respect to the sub-scanning direction. By matching the columnar crystal angle and the incident angle, the sharpness in the sub-scanning direction is increased and substantially matched with the sharpness in the main-scanning direction even though the beam diameter is larger in the sub-scanning direction than in the main-scanning direction. be able to.

[0023]

As described above in detail, in the present invention, a radiation image conversion panel having columnar crystals having a specific inclination on the side of the sub-scanning direction is used, and a radiation image conversion panel from a direction substantially matching the inclination of the columnar crystals is used. By irradiating with excitation light, sharpness can be improved. Furthermore, the sharpness in the main scanning direction and the sharpness in the sub-scanning direction can be matched.

Further, since the incident end face of the light collecting means is arranged perpendicularly to the normal line direction of the radiation image conversion panel for light detection, the stimulated emission light can be detected most efficiently.
For this reason, it is possible to realize a radiographic image reading apparatus that has a simple circuit configuration and that can improve both sharpness and light collection efficiency without complicating the optical system.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing incident angles according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a state of emitted light detection according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the sharpness of one embodiment of the present invention.

FIG. 5 is a configuration diagram showing a specific configuration of an embodiment of the present invention.

FIG. 6 is a configuration diagram showing a specific configuration of another embodiment of the present invention.

FIG. 7 is an explanatory diagram showing an excitation light incident angle in the configuration shown in FIG.

FIG. 8 is a configuration diagram showing a configuration of a conventional reading device.

[Explanation of symbols]

 13 Radiation image conversion panel 13a Photostimulable phosphor layer 21 Filter 22 Photodetector

Claims (1)

[Claims] 1. A radiographic image reading apparatus which scans a radiographic image conversion panel on which radiographic image information is stored and recorded with excitation light to read the stored and recorded radiographic image information as stimulated emission light. Radiation image conversion panel having a stimulable phosphor layer composed of independent columnar crystals having a specific inclination with respect to the line direction, and inclination of columnar crystals forming the stimulable phosphor layer of the radiation conversion panel Excitation light irradiating means for irradiating excitation light from a direction, a condensing means having an incident end face of stimulated emission light arranged substantially perpendicular to the normal direction of the surface of the radiation image conversion panel, and a condensing means And a photoelectric conversion means for photoelectrically converting the stimulated emission light collected by the radiation image reading apparatus.