JPS6186744A - Method for reading and erasing radiant-ray image information and its device - Google Patents

Abstract

PURPOSE:To miniaturize the system of the titled method, by using a deflector for reading also for erasion and and almost simultaneously performing reading and erasion by causing the deflector to scan a section which has been scanned for reading. CONSTITUTION:Lights 2 from a laser light source 1 are made incident to an acoustic optical modulator 3 and divided into zero-dimensional lights and one-dimensional lights, namely, into reading laser lights 2A which are exciting lights and erasing laser lights 2B which are erasing lights. The reading laser lights 2A repeatedly make main scan in the direction shown by the arrow A on a phosphor sheet 6 on which radiant-ray image information is recorded through a mirror 4 and rotary polygon mirror 5 and the sheet 6 is carried in the direction shown by the arrow B and auxiliary-scanned. The accelerated phosphorescence of the sheet 6 enter into a transparent light condensing body 8 and outputted to a CRT11 as a visual image after the light is converted into electric signals by means of a photomultiplier tube 9 through the cylindrical read end section 8c of the light condensing body 8. On the other hand, the erasing laser lights 2B makes main scan in the direction shown by the arrow C on the section of the sheet 6 which has been read by the reading laser lights 2A through the rotary polygon mirror 5 can be used again for recording image information.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention provides a method for recording and reproducing radiation image information using a stimulable phosphor sheet, in which the radiation image information is removed and the stimulable phosphor sheet is The present invention relates to a reading and erasing method for erasing residual noise, and a reading and erasing device for carrying out this method.

(Technical Background and Prior Art of the Invention) When a certain kind of fluorescent material is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), part of this radiation energy is absorbed by the fluorescent material. When the energy is accumulated in the phosphor and the phosphor is then irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence in response to the accumulated energy. A phosphor exhibiting such properties is called a stimulable phosphor.

Using this stimulable phosphor, radiation image information of a subject such as a human body is stored and recorded on a sheet of stimulable phosphor, and this is scanned with excitation light to cause stimulated luminescence. A radiation image information recording and reproducing method has been proposed in which an image signal is obtained by photoelectrically reading the radiation image, and this image signal is processed to obtain a radiation image of a subject that is suitable for diagnosis. (For example, JP-A No. 5
No. 5-12429, No. 56-11395, No. 55-1
No. 63472, No. 56-104645, No. 55-11
No. 6340, etc.) In this method, the final image may be reproduced as a hard copy or reproduced on a display device such as a CRT. In such a radiation image recording and reproducing method, a stimulable phosphor sheet (strictly speaking, this is a panel-shaped sheet, a drum-shaped sheet, etc.)
Although it can take various forms, it is collectively called a "sheet"
Let's say that. ) is economical to use repeatedly.

If sufficient intensity of excitation light is applied during reading, the accumulated radiation energy caused by the recorded radiographic image information should be erased, but in reality, it cannot be completely erased only by the excitation light applied during reading. . Therefore, when the phosphor sheet is repeatedly used, there is a problem in that the previously recorded image remains, resulting in noise during the next recording.

According to experiments, if the maximum level of accumulated energy when recording radiation image information is 100, it is 0.01 to 0.00.
It has been found that if the image is not erased to about 0.01, that is, to 10-4 to 10 times, it will become an afterimage in the next recording, resulting in noise that hinders proper diagnosis.

In order to eliminate afterimages in such systems, the applicant has proposed that after reading, the phosphor sheet is excited with light at a wavelength that includes light in the excitation light wavelength range of the phosphor to sufficiently release the remaining radiation energy. proposed a method to do so. (Japanese Unexamined Patent Publication No. 57-116300) However, in conventional afterimage erasing methods, light emitted from a light source such as a fluorescent lamp, Na lamp, He lamp, or tungsten lamp is used as noise erasing light to emit residual radiation energy. Since erasing is performed by irradiating the entire surface of the sheet with this erasing light, in order to erase the accumulated energy level of the afterimage to 10-4 to 10-6 times, for example, 300001x irradiation with a tungsten lamp is required. It is necessary to irradiate the sheet with high-intensity erasing light for a long time, such as for 100 to 1000 seconds, and it is necessary to provide an erasing zone in which the sheet that has been read is stored for a certain period of time for erasing. Furthermore, since the above-mentioned light source generates not only light but also a large amount of heat, it is impossible to arrange the light source close to the sheet, and it is not possible to provide a wide gap between the light source and the sheet in the erasing zone. It was necessary.

Furthermore, a cooling device is also required to cool down the erasing zone, which generates a large amount of heat, resulting in the problem that the entire erasing device becomes a dog.

Furthermore, this erasing device is usually placed close to other devices such as a reading device that reads images, and the sheet is transported and circulated between each device by a conveyance mechanism, so it is difficult to erase the image. If a device generates a large amount of heat, it will have an adverse effect on other devices and electrical circuits placed nearby. Further, in the conventional erasing method, a high voltage power source is provided for the light source, which poses the risk of electric shock and also has the disadvantage of consuming a large amount of power (which is not economical).

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to omit the erasure zone in a radiographic image information recording and reproducing system by incorporating an afterimage erasing device into a radiographic image information reading device. It is an object of the present invention to provide a method and apparatus for reading and erasing radiation image information, which can solve problems such as a large amount of heat generation and the installation of a high voltage power supply.

(Structure of the Invention) The reading and erasing method and device of the present invention splits a light beam emitted from a beam light source into excitation light and erasing light by a light beam splitting optical system, and separates the divided excitation light and erasing light, respectively. The erasing light is applied to the same deflector to scan mutually different positions on the stimulable phosphor sheet on which radiation image information is stored and recorded, and the erasing light is applied to the sheet for reading by the excitation light. The feature is that the portion that has been scanned is scanned. In other words, a sheet that is relatively moved in the sub-scanning direction at a constant speed within the reading/erasing device is first scanned by excitation light, and stimulated luminescence light is generated from the scanned location to read image information. Subsequently, the portion of the sheet where this reading has been performed is scanned with erasing light to remove residual radiation energy, and the erasure and erasure are performed almost simultaneously.

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

FIG. 1 is a perspective view showing an outline of a reading/erasing device according to an embodiment of the present invention.

A laser beam 2 emitted from a laser light source 1 is made incident on an acousto-optic modulator (AOM) 3 provided on the optical path, and is split into 0th-order light and 1st-order light, which is read as excitation light. The laser beam 2A is an eraser laser beam 2A, and the eraser laser beam 2B is an eraser beam. After the two reading laser beams are reflected by a mirror 4 provided on the optical path and change their optical path, they are made incident on a rotating polygon mirror 5 which is a deflector, and as the rotating polygon mirror 5 rotates, It is reflected and deflected, and is repeatedly main-scanned in the direction of the arrow on a stimulable phosphor sheet 6 on which radiographic image information is stored and recorded, which is disposed below the rotating polygon mirror 5. The seat 6 is an endless belt device 7
Since the sheet 6 is attracted to the sheet 6 and is conveyed in the direction of arrow B and subjected to sub-scanning, the main scanning is repeated in a direction substantially perpendicular to this sub-scanning, and the two-dimensional scanning of the reading laser beams over the entire surface of the sheet 6 is performed. It is done.

As the sheet 6 is irradiated with the reading laser beam by the two reading laser beams as it is scanned by the two reading laser beams, the sheet 6 emits stimulated light according to the image information accumulated and recorded thereon, and this emitted light (not shown) enters a transparent light condenser 8 having an incident end face 8a arranged parallel to the main scanning line near the sheet.

The light condenser 8 has a front end 8b located near the sheet 6 formed into a flat plate shape, and gradually becomes cylindrical toward the rear end, and becomes approximately cylindrical at the rear end 8C. The photomultiplexer 9 is coupled to a photomultiplexer 9, which is a photodetector, and the stimulated luminescent light incident from the incident end face 8a is focused on the rear end portion 8C, and is received by the photomultiplexer 9. In this photomultiplier 9, the stimulated luminescent light is converted into an electric signal, and the obtained electric signal is sent to the image information processing circuit 10 for image processing, and then outputted to, for example, a C Tll as a visible image. or recorded on the magnetic tape 12.

On the other hand, the erasing laser beam 2B is made to enter the rotating polygon mirror 5 at a different angle from the reading laser beam 2A, and is reflected and deflected by the rotating polygon mirror 5 to produce the reading laser beam of the sheet 6. The reading laser beam main scans the portion where the reading by the two persons has been completed in the direction of arrow C, which is substantially parallel to the main scanning direction of the two persons. Although some of the accumulated radiation energy remains in the portion of the sheet 6 where reading has been completed, the residual energy is removed by being irradiated with the erasing laser beam 2B, and the sheet 6 is replaced with a new one. It becomes possible to record radiation image information. Note that, in order to sufficiently erase the residual energy on the sheet 6, it is preferable to use zero-order light, which has a large amount of light rays, as the erasing light among the laser beams split by the AOM 3. Also, 0th order light and 1st order light.

The quantity balance may be adjusted as appropriate so that reading and erasing can be carried out most effectively.

Furthermore, in the embodiment shown in FIG. 1, the scanning position by the bladder tightening laser beam 2A and the erasing laser beam 2
A light shielding plate 15 having a width equal to or larger than the length of the scanning line and standing upright on the sheet 6 is provided between the scanning position B and the scanning position B. This light-shielding plate 15 is made of a light-absorbing plate or a reflecting mirror, and when the erasing laser beam 2B irradiates the sheet 6, the light emitted from the irradiation position' is transmitted through the light-shielding plate 15.
This prevents the light from entering the light condenser 8. In addition, if the light shielding plate 15 is small (both have a reflective mirror on the reading side surface and are arranged sufficiently close to the light condenser 8), the stimulated luminescence light emitted from the scanning position of the two reading laser beams will be absorbed by the light shielding plate 15.
5 toward the incident end surface 8a of the light collector 80, the light collection efficiency of the light collector 8 can be improved.

Note that this light shielding plate 15 is used when the scanning positions of the reading laser beam and the erasing laser beam can be separated sufficiently, or when a condenser is used that does not cause the possibility of condensing light emitted from a far position on the sheet. It may be omitted in cases where the emission of light from the sheet by the erasing laser beam does not affect reading.

In the embodiment shown in FIG. 1, the light beam splitting optical system that splits the light beam 2 into two excitation lights and the erasing light 2B and causes them to enter the deflector from different directions and at different angles is the same as described above. Although it is composed of the AOM 3 and the mirror 4, the light beam splitting optical system does not necessarily have to be composed of the above-mentioned optical elements. For example, as shown in FIG. It may be made up of a beam splitter 13 that splits the light into two excitation lights and an erase light 2B, and a mirror 14 that adjusts the optical path of the split light.

(Effects of the Invention) As explained above, according to the reading and erasing method and device of the present invention, since the deflector for reading is also used for erasing, a large erasing device can be omitted, resulting in a compact system as a whole. can be realized. In addition, since afterimages are erased by scanning the erasing light, there is no need to irradiate high-intensity erasing light for long periods of time, and the amount of heat generated is significantly reduced, greatly reducing the negative impact on other equipment and electrical circuit systems. be able to. Furthermore, since a high-voltage power source for the erasing light source is not required, the power consumption is reduced, which is economical, and the risk of electric shock is eliminated, so its practical value is extremely great.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an outline of a reading/erasing device according to one embodiment of the present invention, and FIG. 2 is a schematic diagram showing a light beam splitting optical system of a reading/erasing device according to another embodiment of the present invention.

Claims (1)

[Claims] 1) A stimulable phosphor sheet on which radiation image information has been accumulated and recorded is conveyed at a constant speed in the sub-scanning direction, and excitation light deflected by a deflector is caused to main-scan the sheet. This stimulated luminescence light is generated by photoelectronic reading to obtain an image signal, and after reading, erasing light is irradiated onto the sheet to eliminate noise due to residual radiation energy, etc. In a method for reading and erasing radiation image information, a light beam emitted from a laser light source is incident on a light beam splitting optical system to be split into two light beams, and each of these two light beams is attached to a sheet on the same deflector. The sheet is scanned at different positions on the sheet and is reflected and deflected, one of the light beams is used as the excitation light to scan and read the sheet, and the other light beam is used as the erasing light. A radiation image information reading and erasing method characterized in that reading and erasing are performed almost simultaneously by scanning a portion of the sheet where the scanning for reading by one of the light beams has been completed. 2) A beam light source that emits a light beam, which is provided on the optical path of the light beam, reflects and deflects the light beam onto a stimulable phosphor sheet on which radiation image information is stored and recorded, and emits the light beam onto the sheet. a deflector for repeatedly main-scanning the sheet; a sub-scanning device for sub-scanning by moving the sheet and the light beam relatively in a direction substantially perpendicular to the main-scanning direction; an excitation light that irradiates the light beam onto the sheet to produce stimulated luminescence light in accordance with image information accumulated on the sheet; and a light beam that remains on the sheet after irradiation with the excitation light. and an erasing light for erasing radiographic image information, and the divided excitation light and erasing light are transmitted to a part of the sheet downstream in sub-scanning from the part of the sheet that is main-scanned by the excitation light. a light beam splitting optical system that causes a light beam to enter the deflector in a main scanning manner; one end has an entrance end face extending in the main scanning direction of the excitation light; the other end has an exit end face; A radiation image information reading and erasing device comprising: a light condenser that guides light incident from the light source to the exit end surface; and a photodetector connected to the exit end surface of the light collector. 3) A light shielding plate having a width at least equal to the length of the scanning line and standing substantially perpendicular to the sheet surface is provided between the scanning position by the excitation light and the scanning position by the erasing light. A radiation image information reading and erasing device according to claim 2. 4) the light beam splitting optical system includes an acousto-optic modulator;
4. The radiation image information reading and erasing apparatus according to claim 2, wherein the light beam is split by the acousto-optic modulator.