JPS6149556A - Reader for radiation image information - Google Patents

Abstract

PURPOSE:To reduce influence upon a readout and improve readout accuracy by preventing an afterglow of instantaneous light emission, an afterglow of accelerated phosphorescence, and accelerated phosphorescence from outside a scanned part to strike a converging body through a means which is easily designed and manufactured. CONSTITUTION:A memory type light emitting body sheet 3 provided to the reader is moved as shown by an arrow B to make a subscan, a main scan of laser scanning light 1b as exciting light is made along scanning lines 3a, and accelerated phosphorescence 1c is caused at the scanning position on the sheet 3. Further, emitted light 1c is made incident on the sheet 3 within a range of a visual angle theta and a cylindrical lens 5 is provided to converge the light only in the subscanning direction B. A light shield member 6 is arranged over the convergence position on the lens 5 and the emitted light 1c is made incident on the incidence surface 4a of the converging body 4 through the slit 6a of the material 6. Thus, an afterglow of instantaneous light emission, an afterglow of accelerated phosphorescence, and accelerated phosphorescence from outside the scanned body are prevented from being incident on the converging body 4 to reduce influence upon a readout, improving readout precision.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a reading device for radiation image information stored and recorded on a stimulable phosphor sheet. The present invention relates to a radiation image information reading device that can accurately read stimulated luminescence light emitted from the sheet in accordance with the radiation image information obtained.

(Technical Background of the Invention and Prior Art) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, ultraviolet rays, etc.), part of this radiation energy is absorbed into the phosphor. It is known that when this phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. is called a storage fluorophore.

Using this stimulable phosphor, the radiation of subjects such as the human body,
Line image information is once recorded on a sheet having a layer made of a stimulable phosphor (hereinafter referred to as a ``stimulable phosphor sheet'' or simply ``sheet''), and this stimulable phosphor sheet is exposed to a laser beam, etc. scan with excitation light to generate stimulated luminescence light.
A radiation image information recording and reproducing method has been proposed in which the stimulated luminescence light is read photoelectrically to obtain an image signal, and the image signal is processed to obtain a radiation image of the subject that is suitable for diagnosis. (For example, JP-A-55-12429, JP-A-56-113
No. 95, No. 55-163472, No. 56-10464
5@, No. 55-1163/10, etc.) The radiographic image information reading device used in the radiographic image information recording and reproducing method proposed above is shown in FIG. 5, and its convenience will be explained using this figure. do.

A laser beam 101a of a constant intensity is emitted from a laser light source 101 as excitation light to a galvanometer mirror 102.
c', by this galvanometer mirror 102,
Sheet 1 placed below the galvanometer mirror 102
Laser light main scans in the width direction of 03 (scanning in the direction of the arrow)
The laser beam is deflected and irradiated onto the sheet 103 in such a manner. Furthermore, since the sheet 103 is attracted onto, for example, an endless belt device 109 and conveyed in the direction of arrow B, the main scan is repeated at an angle substantially perpendicular to the sub-scan, and the entire surface of the sheet 103 is illuminated by the laser beam 101b. A target scan is performed. For this reason, the laser beam 101b
The part of the sheet irradiated with the laser beam 101b as scanned by the laser beam 101b emits stimulated light with an intensity corresponding to the accumulated and recorded image information, and this emitted light forms an incident end face 104a parallel to the main scanning line near the sheet. Transparent light collector 104
The light enters the light condenser 104 from the incident end face 104a. This light condenser 104 has a front end 104b located near the sheet 103.
is formed into a planar shape and gradually becomes cylindrical toward the rear end side, and the rear end portion 10
Since it has a substantially cylindrical shape at 4G and is connected to the 7-optional 105, the stimulated luminescent light entering from the incident end surface 104a is collected at the rear end 104C and transmitted to the 7-optional 105. After the C1 stimulated luminescence light is converted into an electrical signal in the photomultiple 105, it is sent to the image information reading circuit 106. The electrical signal is processed by the image information reading circuit 106, and is output as a visible image on a CRT 107, recorded on a magnetic tape 108, or as a hard copy on a photosensitive material for close-up photography. It can also be recorded.

- When reading data, the light condenser 104
4a is parallel to the main scanning line and covers almost the entire width of the sheet 103, so all the light from the place where the incident end surface 104a can be seen is read, and the light from the place where the laser beam 101b is incident is read. A sheet 10 that allows you to see not only the stimulated luminescent light but also the incident end surface 104a.
It also reads all the light coming from other places on 3. The afterglow emitted by the sheet 103 poses a problem as light other than the stimulated luminescent light that enters the incident end surface 104a and is read. This afterglow includes instantaneous luminescence afterglow and stimulated luminescence afterglow.

Instantaneous light emission afterglow refers to the instantaneous R light emitted from a sheet when radiation is irradiated to record image information on the sheet. Even after the radiation irradiation is stopped, the light does not disappear and continues to emit light while attenuating. describe a phenomenon. The characteristics of this instantaneous light emission afterglow vary depending on the type of stimulable phosphor used in the sheet, but are generally as shown in FIG. FIG. 6 is a graph showing luminescence intensity on the vertical axis and time (1) on the horizontal axis. After radiation irradiation was performed for Δt2 hours from time t1 to t2, when the irradiation was cut off, the luminescence intensity it A ! The intensity of the instantaneous light emitted in No. 1 does not immediately reach 0, but it shows an instantaneous afterglow in which the intensity decreases as an exponential function with a gradually increasing time constant.

Specifically, the attenuation of the luminescence intensity of this instantaneous luminescence afterglow is, for example, about 180 seconds after radiation irradiation (i.e., (i3-'
l:2)-180 seconds) II j 3. The luminescence intensity of the instantaneous luminescence afterglow at I+ is approximately 10% of the intensity of the stimulated luminescence light generated by excitation light scanning in terms of order.
'4 times as much.

For this reason, after recording image information by irradiating the sheet with radiation through the subject, until this image information is read,
After one predetermined period of time has elapsed, the intensity of the instantaneous light emission afterglow decreases sufficiently, and the afterglow becomes negligible. However, when reading radiation image information immediately after recording, the image information recording section is integrated into a radiation image information reading device, such as that disclosed in Japanese Patent Application No. 58-66730 previously filed by the present applicant. When recording and reading are performed continuously, at high speed, and in large quantities using a device built into a radiographic image information recording/reading device (i.e., a radiographic image information recording/reading device), the @R emission afterglow as well as the stimulated emission light is The light is read before the light has sufficiently attenuated, and the influence of the instantaneous light emission afterglow on the read image information becomes large.

In addition, stimulated luminescence light is emitted from a small area where the excitation light is incident, whereas instantaneous luminescence afterglow is emitted from the entire surface irradiated with radiation. From the incident end surface 104a of the photomultiplier 104, stimulated luminescence light and instantaneous emission afterglow from all locations where the incident end surface 104a can be seen are simultaneously taken in and sent to the photomultiple 105. In this case, compared to the area of the sheet 103 where the laser beam is irradiated, the
Since the area of the part where the entrance end face 104a can be seen is extremely large, as mentioned above, after a certain amount of am has elapsed after radiation irradiation, the intensity of the instantaneous emission afterglow is ignored compared to the intensity of the stimulated emission light. Even if it is made as small as possible, the amount of light transmitted to the photomultiple 105 due to the instantaneous light emission afterglow cannot be ignored.

On the other hand, stimulated luminescence afterglow refers to irradiation of excitation light (e.g., laser light) in order to read the radiographic image stored and recorded on the sheet to cause stimulated luminescence. This refers to a phenomenon in which emitted light does not disappear at the same time as it is interrupted, but continues to emit light even though it is attenuated. The characteristics of this stimulated luminescence afterglow vary depending on the type of stimulable phosphor used in the sheet, but are generally as shown in FIG. 7. FIG. 7 is a graph showing the luminescence intensity on the vertical axis and the time (1) on the horizontal axis. When the excitation light is irradiated for Δt6 hours from time t4 to t5 and then cut off, the luminescence intensity "CI+" The intensity of stimulated luminescence does not immediately go to zero, but decreases along an exponential function with a gradually increasing time constant. (In other words, the intensity decreases rapidly at first, and then Specifically, the attenuation of the luminescence intensity of this stimulated luminescence afterglow has an initial time constant of about 1 microsecond. That is, the luminescence intensity is reduced to 1/e (D/C= 1/e)
:s j5) is about 1 microsecond. By the way, generally speaking, the speed at which the excitation light is scanned (main scanning) on the stimulable phosphor sheet by a galvanometer mirror is approximately 50
Since it is on the order of Hertz, one scan takes approximately 20,000 microseconds. Therefore, the intensity of the stimulated luminescence afterglow, which decays exponentially with an initial time constant of 1 microsecond, is an order of magnitude smaller than the intensity of the stimulated luminescent light, and each point has J3
The intensity of the stimulated luminescence afterglow becomes almost negligible at -.

However, stimulated luminescence light is emitted from a very small area where the excitation light is incident, whereas stimulated luminescence afterglow is emitted from all the surfaces scanned by the excitation light. From the incident end surface 104a of the light body 104, the stimulated luminescent light and the stimulated luminescent afterglow from all the locations where the incident end surface 104a can be seen are simultaneously taken in and sent to the photomultiple 105. In this case, compared to the area of the part where the excitation light is incident on the sheet 103 and the stimulated luminescence occurs, the area of the part where the stimulated luminescence afterglow occurs due to the scanning of the excitation light is the same as in the case of the instantaneous luminescence afterglow. Because the intensity of the stimulated luminescence afterglow is extremely large, even if the intensity of the stimulated luminescence afterglow is negligibly small compared to the intensity of the stimulated luminescence light as described above, the amount of light transmitted to the photomultiple 105 is still smaller than that of the stimulated luminescence afterglow. The amount of light can no longer be ignored.

The afterglow that is read at the same time as the stimulated luminescence light becomes a noise component in the image signal of the radiographic image, making it difficult to read accurate radiation image information.

In particular, instantaneous luminescence afterglow is a problem when reading radiation image information immediately after recording it on a stimulable phosphor sheet, and stimulated luminescence afterglow occurs when radiation image information is excited on a stimulable phosphor sheet on which a radiographic image has been recorded. This becomes a particular problem as the speed at which light scans becomes faster.

Next, Figures 8A and 8B show the influence of afterglow on image information.
This will be explained in detail using figures. Figure 8A shows Sea 1-1
(For example, radiation image information of a human head is recorded in J 3 a, and in Fig. 8B, excitation light (
When scanned by a laser beam), the
The amount of light transmitted to the tomaru is shown on the horizontal axis with the position corresponding to the scanning of line a. In the isB diagram, the amount of light actually transmitted to the photomultiplier is shown by the broken line 9J1, and of the amount of light shown by this broken line 1, the afterglow is the instantaneous light emission afterglow a3J.
: The sum of the afterglow afterglow emission) is indicated by the chain line 9J3,
The amount of stimulated luminescence is indicated by actual #Q9Jz. That is, afterglow m
9.3 and stimulated luminescence m9. The sum of z is
The light m 9.1 is transmitted from F1 to F1. This light f
i9.1 is converted into an electrical signal by a photomultiplier and then subjected to logarithmic conversion (LOG conversion), and a reproduced image is obtained from this logarithmically converted signal. In this case, the value is different when the photoluminescence 1 transmitted to the photomultiplier is converted into an electric signal and logarithmically converted, and when only the stimulated luminescence ff19J2 is converted into an electric signal and this is logarithmically converted. light transmitted
'9. If an image is reproduced using the value of l, the reproduced image will be different from the actual image. That is,
The reproduced image becomes inaccurate or unclear, which poses a serious problem in diagnostic suitability.

In addition to the above-mentioned afterglow problem, a part of the laser beam 101b is reflected on the surface of the sheet 103, and this reflected light is further reflected on the incident end surface 104a of the light condenser 104, and the laser beam 101b is reflected on the surface of the sheet 1'03.
In some cases, the phosphor returns to an unspecified surface and excites the phosphor in that area, causing stimulated luminescence. When such stimulated luminescence light generated from outside the scanned area is read, it becomes a noise component of the image signal and reduces the sharpness of the image.

Therefore, it is desired to develop a device equipped with a means to prevent afterglow, etc. other than stimulated luminescence light from the scanning location of excitation light from entering the incident end face of the light collector, as described above. An invention proposing a method for solving the problem has already been filed by the present applicant (Japanese Patent Application No. 153691/1982).
.

In the reading device according to the above invention, the excitation light is irradiated onto the sheet and the sheet 1 is
A light-shielding member having a width of 1 to 1 to allow only the incidence of stimulated luminescence light from the body to the condensing body and covering a portion before scanning the sheet and along a scanning line of the scanning stream is used to condense the light. It is characterized in that it is provided between the incident end face of the body and the sheet. However, since the light collector is placed close to the sheet in order to increase the efficiency of collecting stimulated luminescence light, it is spatially difficult to actually provide a light shielding member between the sheet and the light collector. The necessary stimulated luminescence light is cut by the light shielding material.
In order to reduce the range of the sheet picked up by the light condenser without losing it, the slit of the light shielding member is made as small as the range of the sheet 1-, and the light shielding member is placed so that it is almost in contact with the sheet. There were problems such as the arrangement was difficult and it was difficult to make a light shielding member with a minute slit width.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and it is possible to eliminate instantaneous luminescence afterglow, stimulated luminescence afterglow, and from outside the scanned part by means that can be easily designed and manufactured. The object of the present invention is to provide a radiation image information reading device that can perform highly accurate reading by preventing the generated stimulated luminescence light from entering a condenser and reducing its influence on reading. be.

(Structure of the Invention) The radiation image information reading device of the present invention has a slit extending in the main scanning direction between the sheath 1 and the incident end surface of the condenser, so that light other than stimulated luminescence light is transmitted to the incident end surface. The light shielding member is provided to prevent the light from reaching the beam, and further focuses the stimulated luminescent light emitted from the scanning point toward the sea 1 into the slit only in the sub-scanning direction, so that the light enters the light condenser through the slit. The device is characterized in that it includes an optical system that allows the stimulated luminescence light to enter the end face. The optical system makes the stimulated luminescence light from the scanning point enter the cylindrical lens and focuses it only in the sub-scanning direction within the slit,
It can be designed such that the stimulated luminescence light that has passed through the cylindrical lens is deflected by a mirror so that the stimulated luminescence light passes through an arbitrary optical path before being focused within the slit.

Therefore, the reading device of the present invention prevents afterglow and the like from reaching the light condenser, and makes the design of the reading device easier and more versatile.

(Actual IM Mode) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing the structure around the scanning section of a reading device according to an embodiment of the present invention.

The stimulable phosphor sheet 3 is moved in the direction of arrow B for sub-scanning. The laser scanning light 1b as excitation light main scans the sheet 3 along the scanning line 3a, and the laser scanning light 1b
Stimulated luminescence light 1G is emitted from the scanning position on the sheet 3 irradiated with b.

Further, above the sheet 3, there is provided a cylindrical lens 5 which allows the stimulated luminescence light 1C to enter within the range of the field angle θ and focuses it only in the sub-scanning direction.
is focused above the cylindrical lens 5 by this cylindrical lens 5, and is incident on the incident end surface 4a of the light condenser 4 provided immediately above the focusing position.

The sheet 3 emits an afterglow 1A of instantaneous luminescence during storage recording from a portion 3A before scanning, and an afterglow 1B of stimulated luminescence from a portion 3B immediately after scanning. In order to prevent these afterglow lights from entering the light condenser 4, a light shielding member 6 is provided below the light condenser 4.

This light shielding member 6 has a slit 6a extending in the main scanning direction and having a length equal to or greater than the main scanning width in the center thereof.
The cylindrical lens 5 is arranged so that the focused position of the stimulated luminescence light 1C is within the slit 6a.

The width W of this slit 6a is defined as a distance from the scanning position to the cylindrical lens 5, a distance from the cylindrical lens 5 to the focal position of the stimulated luminescence light, and b.
The imaging magnification of the cylindrical lens represented by /, a is M, and the width of the sheet 3 on which the emitted light is to be focused is S.
Then, it is defined by SXM. Therefore, by increasing the imaging magnification M, the width S of the condensing range can be decreased, and the width W of the slit 6a can be made sufficiently large, making it easier to create the slit. The cylinder 1 sill lens 5 is
In order to make all of the stimulated luminescence light from the condensing range incident, it is necessary to arrange it as close to the sheet 3 as possible (increase the angle of view θ), so it is preferable to use a lens with a short focal length, and it is preferable to use a lens with a relatively short focal length. It is preferable to use a round bar lens or a semi-round bar lens that can provide a short focal length. Furthermore, in this embodiment described above, the laser scanning light 1
b is shown in the figure, and the cylindrical lens 5 is lightened after being deflected by the reflecting mirror 7 disposed below the light shielding member 6.
Although the C-sheet 3 is scanned, the cylindrical lens 5 does not need to act as a lens for the laser scanning light 1b, so as shown in FIG. The incident portion of the laser scanning light 1b may be made flat.

Next, with reference to FIG. 3, an optical system for collecting stimulated luminescence light on a condenser according to another embodiment of the present invention will be described.

In the embodiment shown in FIG. 3<a,), two cylindrical lenses 5A having the same focal length are used.

5B are arranged continuously in the sub-scanning direction. This is effective when it is not possible to obtain a sufficiently large angle of view θ by using one cylindrical lens. It is reflected by 8A and 8B and guided to be focused at the same position within the slits 1 to 6a of the light shielding member 6. Another embodiment shown in FIG. 3(b) is also effective for increasing the angle of view θ, and includes three cylindrical lenses 5C15D with the same axis,
51 are provided in series to focus the stimulated luminescent light that has passed through each lens.

Furthermore, in the first embodiment of the present invention shown in FIG.
Although the laser scanning light 1b is irradiated upwardly, it is also possible to irradiate the laser scanning light 1b from above the light shielding member 6, as shown in FIG. That is, the light-shielding portion 6A of the light-shielding member 6 is made of a dichroic film that transmits light of the wavelength of the laser scanning light 1b and cuts the light of the wavelength of stimulated luminescence and afterglow, and the slit portion 6B of the light-shielding member 6 is made of a transparent film. The laser scanning light is irradiated from above the light shielding member while blocking afterglow by using a film or dichroic film that passes light with the wavelength of stimulated luminescence light and cuts light with the wavelength of laser scanning light. This is what made it possible. Although the embodiments of the present invention have been described above, the present invention has the ability to design devices in various modes other than the above-mentioned embodiments by changing the arrangement and combination of optical systems, and has an extremely wide range of applications. It is something.

a5, the shape of the condenser constituting the radiation image information reading device of the present invention is not limited to the shape shown in FIG.
As described in No. 27543, the exit end face may be divided into a plurality of sections, and each section may be connected to a photodetector such as a 7-meter.

(Effects of the Invention) As described above in detail, according to the radiation image information reading device of the present invention, the light shielding member prevents afterglow from reaching the incident end surface of the light collector, and stimulated luminescence Since only the laser beam is guided through the slit to the condenser, the influence of afterglow on reading can be greatly reduced, and a part of the laser scan is reflected from the surface of the sheet and reaches the incident end face of the condenser. Since the reflected light is prevented from returning to the sheet from the incident end surface, stimulated luminescence will not occur outside the scanned area, and an image with high sharpness can be obtained. In addition, by disposing the optical system including the cylindrical lens between the light shielding member and the sheet, it is no longer necessary to arrange the light shielding member and the light condenser close to the sheet, which simplifies the installation h1. When the image magnification is increased, a sufficient afterglow light shielding effect can be obtained even if the slit width is large, and the production of a light shielding member is facilitated, which has extremely great practical value.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure near the scanning section of a reading device according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. 1 showing the shape of the cylindrical lens in the embodiment shown in FIG. , FIG. 3 is a cross-sectional view showing the optical system of the scanning section according to another embodiment of the present invention, FIG. 4 is a cross-sectional view showing the structure near the scanning section according to another embodiment of the present invention, and FIG. 5 is a conventional one. 6 is a graph showing the temporal characteristics of instantaneous luminescence afterglow, FIG. 7 is a graph showing the temporal characteristics of stimulated luminescence afterglow, and FIG. 8A is a graph showing the temporal characteristics of stimulated luminescence afterglow. FIG. 8B shows a sheet on which radiation image information of FIG.
It is a graph showing the luminescence intensity transmitted to ~ circle. 1b... Laser scanning light 1C... Stimulated luminescence light 4.
...to the condenser 5.5, 5B, 5C, 5, o,! 5E... Cylindrical lens 6... Light blocking member 6a... Slit Figure 1 Figure 2 Figure 3 Figure 6 Figure 7 Figure 8A Figure 88 (voluntary) Procedure? ■Authentic Director General of the Patent Office September 20, 1980 1, Indication of the case Patent application 171227/1982 2, Name of the invention Radiographic image information reading device 3, Person making the amendment Relationship to the case Appointment of patent applicant Address: 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name:
Fuji Photo Film Co., Ltd. 4, Agent 5-2-1-6 Roppongi, Minato-ku, Tokyo Number of inventions increased by amendment None Claims: On a stimulable phosphor sheet on which radiation image information is stored and recorded main scanning means for main-scanning the sheet with excitation light to generate stimulated luminescence light; sub-scanning means for sub-scanning by moving the sheet and the excitation light relatively in a direction substantially perpendicular to the main-scanning direction; 9 - a light condenser that guides the light incident from the input end face to the exit end face; a light detector connected to the exit end face of the light collector; a light shielding member having a slit extending in the main scanning direction, which is disposed between the surface of the sheet and the incident end surface of the light condensing body, and a light shielding member having a slit extending in the main scanning direction; A radiation image information reading device comprising an optical system that focuses the light only in the sub-scanning direction using a cylindrical lens provided above the sheet and causes the light to enter the incident end surface of the light collector through the slit. (Voluntary) Procedural amendment Dear Commissioner of the Japan Patent Office November 8, 1980 2 Name of the invention Radiographic image information reading device 3 Relationship to the person making the amendment Case Patent applicant address Address 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture name
Fuji Photo Film Co., Ltd. 4, Agent 5-2-1-6 Roppongi, Minato-ku, Tokyo Number of inventions increased by amendment None 7 Subject of amendment No. 3 (a) □---i]

Claims (1)

[Claims] a main scanning means for generating stimulated luminescence light by main scanning a stimulable phosphor sheet on which image information of a subject is stored and recorded using excitation light; a sub-scanning means for performing sub-scanning by moving in a direction, an entrance end surface extending in the main scanning direction, the end surface being arranged parallel to the main scanning line, and guiding light incident from the entrance end surface to an exit end surface; a light collector, a photodetector connected to an exit end face of the light collector, and a slit extending in the main scanning direction, disposed between the surface of the sheet and the entrance end face of the light collector. A light shielding member and a cylindrical lens provided above the sheet focus the stimulated luminescent light emitted from the scanning point of the sheet only in the sub-scanning direction and make it enter the incident end surface of the light condenser through the slit. A radiation image information reading device comprising an optical system.