JPH0212235A - Noise erasing device for accumulation type fluorescent material sheet - Google Patents

Abstract

PURPOSE:To erase residual energy and to allow noise erasing while generating adequate fogging in the accumulation type fluorescent material sheet by releasing the radiation energy remaining in the sheet by the light reflected from a reflecting plate having the lower reflectivity of UV ray than the reflectivity of visible light. CONSTITUTION:This device is constituted of the light sources such as, for example, aperture type fluorescent lamps 32, which are so disposed as to emit light in the direction to avert the direction irradiation of the accumulation type fluorescent material sheet 1 disposed in the prescribed position and emit the light including visible light and UV light and the reflecting plate which consists of, for example, an aluminum sheet or the like, reflects the light emitted from the light sources 32 toward the sheet 1 and is formed to have the lower reflectivity of the UV light region than the reflectivity of the visible light region. The UV rays of an adequate ratio with the visible light, etc., are selected by the combination of the light sources 32 and the reflecting plate 33 in such a manner that the sheet 1 is irradiated with said rays. The adequate fogging is generated over the entire surface of the sheet in this way and the allowance when the sheet 1 is partly irradiated with the external light is enhanced.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention involves irradiating a stimulable phosphor sheet with radiation to accumulate and record a radiation image, and irradiating the sheet with light to record radiation images emitted from the sheet. The present invention relates to a noise canceling device for a stimulable phosphor sheet, which emits radiation energy remaining in the sheet after reading stimulated luminescence light representing a radiation image.

(Conventional technology) Certain types of phosphors are exposed to radiation (X-rays, α-rays, β-rays.

When irradiated with γ-rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, the phosphor changes depending on the accumulated energy. is known to exhibit stimulated luminescence, and phosphors exhibiting this property are called stimulable phosphors (stimulable phosphors).

Using this stimulable phosphor, radiation image information of a subject such as a human body is partially recorded on a sheet of stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam to make it shine. The resulting stimulated luminescent light is generated and photoelectrically read to obtain an image signal, and based on this image signal, the radiation image of the subject is recorded as a visible image on a recording material such as a photographic light-sensitive material, a CRT, etc. The applicant has already proposed a radiation image information recording and reproducing system for outputting radiation image information. (Unexamined Japanese Patent Publication No. 55
-12429, 5B-11395, 55-18
No. 3472.

No. 5B-104845, No. 55-118340, etc. ) The stimulable phosphor sheet in the above system accumulates and records radiation image information and temporarily carries the recorded image information until it is read by the excitation light scanning, and therefore, the stimulable phosphor sheet is used to temporarily carry radiation image information until it is read by the excitation light scanning. After the process is completed, it is desirable to erase the image information remaining on the sheet and reuse the sheet.

Based on these requests, we have developed a radiographic image sensor that has a built-in noise canceling device that erases the image information remaining on the stimulable phosphor sheet after reading the image information recorded on the stimulable phosphor sheet. An information reading device has been proposed.

In the radiation image information reading device, a cassette containing a stimulable phosphor sheet imaged by an external imaging device is loaded into the cassette holding section, and the stimulable phosphor sheet is taken out from the cassette and read. After reading the image information, the stimulable phosphor sheet is further sent to a noise canceling device to erase the image information remaining on the stimulable phosphor sheet. . The stimulable phosphor sheets that have been erased are, for example, once accumulated in an accumulation tray within the reading device, and the entire tray containing the accumulated sheets is taken out of the device. Thereafter, these erased stimulable phosphor sheets are used again to photograph and record image information. In the above noise canceling device, a light source such as an aperture-type fluorescent lamp (a fluorescent lamp with a reflective film formed on the part other than the aperture so that light is emitted only in the direction in which the aperture is open) is attached to the stimulable phosphor sheet. This is accomplished by irradiating the stimulable phosphor sheet with light emitted from the fluorescent lamp. For example, when the light emitted from the light source, such as the above-mentioned fluorescent lamp, contains an ultraviolet light component, the stimulable phosphor sheet has the function of accumulating radiation energy, as described above, and thus accumulates the energy of the ultraviolet light. Even if the noise is balanced with the energy emitted by visible light or the like, it is not possible to eliminate any more noise, and a so-called fog occurs in which a predetermined amount of radiation energy remains accumulated. This fog is
As long as fogging occurs over the entire surface of the sheet, a fairly high level of ultraviolet light is allowed, so the amount of ultraviolet light used for erasing is allowed as long as fogging does not reach an unacceptably high level. However, in order to record radiation images on the sheet, it is better to have a low level of fog, so we installed a noise canceling device that is configured to cut ultraviolet light as much as possible by installing an ultraviolet removal filter between the fluorescent lamp and the sheet. The applicant has also proposed (Japanese Unexamined Patent Publication No. 63-9793
(See Publication No. 9).

(Problem to be Solved by the Invention) By the way, the stimulable phosphor sheet after noise cancellation may be exposed to external light such as sunlight or indoor lighting, and in this case, the stimulable phosphor sheet remaining on the sheet may be exposed to external light such as sunlight or indoor lighting. Radiation energy may be further erased by the external light, or conversely, energy may be accumulated in the sheet by ultraviolet light contained in the external light. In these cases, if the entire surface of the sheet is irradiated with external light in a --like manner, the fog (residual energy) on the entire surface of the sheet will only change slightly in a --like manner, but if this fog reaches a considerably high level. There are few problems except for cases where only a part of the sheet is exposed to external light. When radiography was performed using this sheet, the noise due to the external light was superimposed on the accumulated image from the radiography, and when this accumulated image was read and reproduced and output as a visible image, the noise due to the external light was superimposed. There is a problem in that a visible image becomes visible and the visible image becomes very difficult to observe.

The present invention aims to solve the above-mentioned problems, and more specifically, it is an object of the present invention to eliminate noise so that even if a stimulable phosphor sheet is partially exposed to external light, the above-mentioned noise caused by external light does not become independent. The purpose of this invention is to provide an erasing device.

(Means for Solving the Problems) A noise canceling device for a stimulable phosphor sheet of the present invention is provided with a noise canceling device for a stimulable phosphor sheet, which is arranged to emit light in a direction that does not directly illuminate a stimulable phosphor sheet placed at a predetermined position. A light source that emits light containing visible light and ultraviolet light, such as an aperture-type fluorescent lamp, and a light source that reflects the light emitted from the light source toward the sheet, have a lower reflectance in the ultraviolet light range than in the visible light range. For example, it is characterized in that it is composed of a reflective plate such as an aluminum plate.

Here, the light source and the reflector are not limited to specific ones, but the combination of the light source and the reflector allows the stimulable phosphor sheet to be irradiated with ultraviolet rays at an appropriate ratio to visible light, etc. selected.

(Function) As mentioned above, if the remaining energy of the stimulable phosphor sheet is erased and the sheet is placed under external light, the remaining energy may be further erased (fogging may be reduced to a lower level). In some cases, energy may be stored (leading to higher levels of fog). The present invention has been made focusing on this phenomenon. As a result of experiments, the level of fog generated on the sheet by the noise canceling device almost determines whether the level of fog after being exposed to external light will be lower or higher. It has been found that when adjusting the level of fog, the level of fog may hardly change even when exposed to external light.

The present invention takes the above points into consideration and reduces the ultraviolet light component by using a reflector that is normally provided.

A reflector having a lower reflectance in the ultraviolet light range than in the visible light range can be realized by, for example, an aluminum plate (aluminum that is electropolished and treated with white alumite), which is commonly used as a reflector.

The noise canceling device of the present invention uses light including visible light and ultraviolet light emitted from a light source such as an aperture-type fluorescent lamp, to reduce the reflectance of the ultraviolet light region compared to the visible light region of the aluminum plate mentioned above. Since the stimulable phosphor sheet is irradiated with light after being reflected by a reflector, the stimulable phosphor sheet is irradiated with light that contains some ultraviolet light, making it possible to cause a moderate amount of fog over the entire surface of the sheet. , the tolerance when a part of the sheet is exposed to external light is increased. Further, as mentioned above, since a commonly used aluminum plate or the like is used, a noise canceling device that is low in cost and easy to maintain can be realized.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

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

FIG. 1 is a schematic side view of a radiation image information reading device incorporating an embodiment of the noise canceling device of the present invention.

This device has a cassette 2 that can store a stimulable phosphor sheet 1.
A cassette holding unit IO1 that removably holds the cassette holder IO1 A reading unit 2 that reads image information stored and recorded on the stimulable phosphor sheet
0. An erasing section 30 equipped with a noise erasing device 31 for erasing the radiation energy remaining in the stimulable phosphor sheet 1 which has been read by the reading section 20. In the cassette holding section 10, a first sheet conveying section 40 conveys the stimulable phosphor sheet taken out from the cassette 2 to the reading section 20, and a second sheet conveying section 40 reciprocates the stimulable phosphor sheet in the reading section 20. Sheet transport section 50 and reading section 2
A third sheet conveying section 60 is provided which receives the stimulable phosphor sheet carried out from the cassette 2, conveys it to the erasing section 30, and then conveys it into the empty cassette 2 in the cassette holding section. Further, the cassette holding section 10 and the reading section 20 are connected to the upper end and the lower end of the first sheet conveying section 40, respectively, as shown in the figure, and are disposed facing each other. The length of the first sheet conveying section 40 is approximately equal to the length of one stimulable phosphor sheet, and the length of the device in the vertical direction is
The height is approximately the same as the height of the cassette holding section 10 and the reading section 20 plus the length of one sheet.

In an external photographing device (not shown), the cassette 2 in which the stimulable phosphor sheet 1 stored therein has been photographed is loaded into the cassette holding portion IO. This cassette 2 has a light-shielding property to prevent the stimulable phosphor sheet 1 from being exposed to external light (change in fog) when recording (photographing) image information by irradiating the stimulable phosphor sheet 1 with radiation. It consists of a cassette main body 2a for storing a stimulable phosphor sheet and a lid part 2b that can be opened and closed. In this apparatus, the cassette 2 is inserted from the cassette insertion opening 3 at the right end of the apparatus with the lid 2b closed and the shutter 4 of the insertion opening opened.

When the cassette 2 is pushed deep into the cassette holder 10 along the guide surface 13 inclined diagonally upward, the tip of the cassette 2 is pushed into the lock release pin 1 which is biased in the projecting direction by a spring.
4, the locking mechanism of the lid (not shown) is released.

When the cassette is released after the lid is unlocked, the cassette falls in the direction of the insertion slot 3 due to its own weight and the urging force of the lock release pin 14, and is held at a predetermined position by a stopper 15 provided at the rear of the guide surface 13. is forced to stop. Next, in the cassette holding section 10, the lid opening means 11 such as a suction cup opens the lid 2b as shown in the figure, and when the lid 2b is opened, the sheet ejecting means 12 such as a suction cup enters into the cassette 2. The stimulable phosphor sheet 1 is adsorbed and transferred to a nearby first sheet conveying section 40. Note that stimulable phosphor sheet 1
is held in the cassette 2 so that the front surface on which the stimulable phosphor layer is formed faces down.

The first to third sheet conveyance sections 40, 50, and 60 each include an endless belt, a guide plate, and a roller, and are taken out from the cassette 2 and transported to the first sheet conveyance section 4.
The stimulable phosphor sheet 1 whose tip is held at the first
The sheet is conveyed in the direction of the arrow A1 by the sheet conveyance section 40, and after stopping once at the position indicated by 1 in the figure to perform width adjustment, etc., it is further conveyed in the direction of the arrow A2 and sent to the reading section 20.

The reading unit 20 scans the stimulable phosphor sheet 1 on which image information is stored and recorded with an excitation light 2LA such as a laser beam, and converts the stimulated luminescent light excited by the scanning and emitted from the sheet 1 into a photoelectric reading unit 22. It is read out photoelectrically and produces an electrical image signal for outputting a visible image. In the figure, 21 is an excitation light source such as a He-Ne laser, and 2
3 is an optical deflector such as a galvanometer mirror. In addition, in this device, as the photoelectric reading means, JP-A-62
A combination of a long photo multiplier 22A disposed along the main scanning line and a small light guide 22B provided on the light receiving surface of the photo multiplier 22A, which is disclosed in No. 18668 etc. The following are used. Further, numeral 24 in the figure is a reflecting mirror that reflects the stimulated luminescence light emitted from the stimulable phosphor sheet toward the light guide 22B. If a long photomultiplier is used in this way, the photoelectric reading means can be miniaturized, which is preferable in terms of downsizing the entire device. A combination of a photomultiplier and a sheet-like light guide, one end of which is arranged along the main scanning line and the other end of which is bent into a cylindrical shape along the photomultiplier, may be used.

Even if the leading end of the stimulable phosphor sheet 1 carried into the reading unit 20 in the direction of arrow A2 reaches the excitation light scanning position, the trailing end of the stimulable phosphor sheet 1 is transported to the nip roller 41A of the first conveying unit 40,
41B, it is not preferable to perform reading in this state because it will cause uneven feeding, etc.
The paper is once conveyed in the arrow A3 direction (forward direction) and placed at the position indicated by 12 in the figure, and then switched back and read while being conveyed in the four directions indicated by the arrow (return direction). The stimulable phosphor sheet 1 is scanned with excitation light 21A substantially perpendicular to the conveyance direction, and the entire surface of the stimulable phosphor sheet is two-dimensionally scanned by the excitation light 21A, producing stimulated luminescence light. This stimulated luminescence light is transmitted to the light guide 22.
B is detected by the photomultiplier 22A. In the photomultiplier 22A, the stimulated luminescent light is converted into an electrical signal, and the obtained electrical signal is sent to an image information processing circuit for image processing.

In addition, when reading radiation image information, reading to obtain image signals for visible image output as explained above (main reading)
Prior to this, pre-reading is performed to read the outline of the radiation image information stored and recorded on the stimulable phosphor sheet, and based on the image information obtained by this pre-reading, the reading conditions etc. for performing the main reading are determined. However, a method of performing the main reading according to the reading conditions is known. As a method for performing such pre-reading, for example, the stimulable phosphor sheet 1 is scanned using excitation light with an energy lower than that of the excitation light used for the above-mentioned main reading, and the stimulated luminescence light emitted by this scanning is Similarly, a method of reading by photoelectric reading means (for example, Japanese Patent Application Laid-Open No. 58-6724
(see Publication No. 0), etc.

The reading unit 20 in the present invention may perform pre-reading in addition to the main reading described above. For example, during pre-reading, the accuracy of sheet conveyance is not required as during main reading, so pre-reading is performed before the stimulable phosphor sheet is conveyed in the direction of arrow A3 and placed at the position indicated by I2 in the figure. You may read the book while switching back in the direction of arrow A4. If you want to match the reading start position of the stimulable phosphor sheet between main reading and pre-reading, after the pre-reading is finished, feed the stimulable phosphor sheet in the direction of arrow A4 and place it at the position indicated by I3 in the figure. The stimulable phosphor sheet may be conveyed to position 13 by performing the main reading again while feeding in the direction of the arrow A3, and after the main reading is completed, by empty feeding in the direction of the arrow A4.

Note that, as shown in the figure, the width of the reading section 20 makes this device
The width of the device in the lateral direction is specified, and the second sheet conveyance section 50 in the reading section conveys the stimulable phosphor sheet along a curved surface. The length is extremely small, about the length of one stimulable phosphor sheet. Therefore, the width of the entire device has been reduced to an extremely small size.

The reading is completed in the reading section 20 as described above.The stimulable phosphor sheet 1 is then transferred to the third sheet conveying section 60, conveyed in the direction of arrow A5, and carried into the erasing section 30. Note that the first sheet transport section 40 and the third sheet transport section 60 are arranged substantially parallel to each other, and the erasing section 30 is also arranged substantially parallel to the first sheet transport section 40 .

A noise erasing device 31 provided in the erasing section 30 erases the radiation image information remaining in the stimulable phosphor sheet 1 after the reading is completed (by causing the stimulable phosphor to emit the remaining radiation energy). ). That is,
A portion of the radiation image information stored and recorded on the stimulable phosphor sheet 1 still remains on the stimulable phosphor sheet after reading, and this residual image is removed in order to reuse the stimulable phosphor sheet 1. The information is erased by the noise eraser 31. The noise canceling device 31 is provided with an erasing light source 32, and the stimulable phosphor sheet 1 is provided with an erasing light source 32.
The residual radiation energy on the stimulable phosphor sheet is emitted by the stimulable phosphor sheet.

The length of the noise erasing device 31 is shorter than the length of one stimulable phosphor sheet, and the stimulable phosphor sheet is stopped within the erasing section 30 to undergo erasure.

In other words, in order to miniaturize the device, this device has a reading section 2.
Since the stimulable phosphor sheet and the erasing section 30 are arranged relatively close to each other, when the stimulable phosphor sheet is conveyed and passed through the erasing section 30 for erasing, the stimulable phosphor sheet is erased when erasing is started. The rear end of the sheet remains inside the reading section 20, making it impossible to carry the next stimulable phosphor sheet into the reading section.

On the other hand, if the stimulable phosphor sheet is stopped in the erasing part and erased, the stimulable phosphor sheet can be moved to the first erasing position (position indicated by 14 in the figure) after reading is completed. Since it can be fed quickly, the next stimulable phosphor sheet can be successively carried into the reading section 20. Along with this, in order to reduce the size, the erasing section 30 is shorter in length than the stimulable phosphor sheet as described above, and the stimulable phosphor sheet 1 is transferred to the third sheet conveying section. First, it is stopped at the position indicated by 4 in the figure, and the first half of the conveyance direction is erased, and then it is moved to the position indicated by I in the figure, and the latter half of the conveyance direction is erased. When the erased stimulable phosphor sheet 1 is placed in the cassette protection part 10, the stimulable phosphor sheet 1 is moved to the direction of the arrow A6 + A? It is transported in the force direction and carried into the cassette 2. Cassette holding part IO
Since the inner cassette is held obliquely, after the stimulable phosphor sheet leaves the third sheet conveying section 80, it is reliably stored in the cassette main body 2a by falling under its own weight. In addition, if there is no cassette in the cassette holding unit 10, such as when the operation of the device is interrupted, or if the reading unit 20 is in use and the stimulable phosphor sheet has not been removed from the cassette, the erased The stimulable phosphor sheet is placed on standby at position 15 in the figure. Furthermore, even if the stimulable phosphor sheet has been erased for a certain period of time, trace amounts of 221 may be mixed into the stimulable phosphor.
Radiation energy is accumulated due to radiation emitted from radioactive isotopes such as RB and 40, and environmental radiation such as X-rays from cosmic rays and other X-ray sources, and this radiation energy is used for the next imaging image. This may cause noise, so
If the waiting time is long, it is desirable to perform erasing again (so-called secondary erasing) in order to remove such noise components. In that case, the stimulable phosphor sheet may be returned to position I4 to perform secondary erasing on the first half of the sheet, and then conveyed again to position 5 and perform secondary erasing on the latter half.

Next, the timing of loading and unloading the cassette into and out of the apparatus and the timing of loading and unloading the stimulable phosphor sheet into and out of the cassette will be explained. When the cassette holding section 10 is empty, the cassette 2 containing the photographed stimulable phosphor sheet 1 can be loaded into the cassette holding section 10, and when the reading section 20 is empty, the The fluorescent phosphor sheet is immediately taken out from the cassette 2 and conveyed to the reading section 20.

In addition, when the preceding stimulable phosphor sheet 1 is being processed in the reading section 20, the stimulable phosphor sheet waits in the cassette with only the lid 2b unlocked. During this time, it is possible to replace the cassette in the cassette holder and change the reading conditions for the stimulable phosphor sheet. On the other hand, if there is an erased stimulable phosphor sheet in the position indicated by I in the cassette from which the stimulable phosphor sheet has been taken out, the secondary erasing described above is performed (the sheet is removed from the primary eraser). If the stimulable phosphor sheet has just been erased, the erased stimulable phosphor sheet is immediately carried into the cassette.

Therefore, such a cassette can be immediately removed from the apparatus and used for new photography. Additionally, if there is no stimulable phosphor sheet at the position indicated by ■5, the empty cassette will wait until the stimulable phosphor sheet that has been read and erased is brought in; Since there is no waiting time for the stimulable phosphor sheet, there is no need to perform secondary erasing.

Here, the noise canceling device 31 in this embodiment will be explained in more detail.

The noise canceling device 31 uses an aperture type fluorescent lamp that emits green light as a noise canceling light source.

Figure 5A is a side view showing an example of an aperture type fluorescent lamp;
FIG. 5B is an enlarged sectional view taken along line xx' in FIG. 5A.

As shown in FIG. 5A, the external shape is that of a normal fluorescent lamp, but as shown in FIG. 5B, the glass bulb 32a
A reflective film 32e is formed on the inner surface of the portion other than the slit-shaped opening 32b, and a fluorescent film 32d is further formed inside the reflective film 32c. Therefore, when this aperture type fluorescent lamp 32 is turned on, the aperture 82
A mixture of visible light and ultraviolet light is emitted from part b.

As shown in FIG. 1, the fluorescent lamp 32 is arranged with its opening 32b facing the reflecting plate 33. Therefore, the erasing unit 30
The stimulable phosphor sheet 1 sent to the stimulable phosphor sheet 1 is not directly irradiated with the light emitted from the fluorescent lamp 32, but is irradiated with the light reflected by the reflection plate 33. The reflecting plate 33 in this embodiment is made of aluminum and is subjected to electropolishing and white alumite treatment.

The ratio of ultraviolet light to illuminance at the position where the stimulable phosphor sheet 1 is irradiated is approximately 3. I x 104mW/c
It was d/9Jx. Here, the aperture 3 of the fluorescent lamp 32
2b toward the stimulable phosphor sheet 1 side,
When the light emitted from the sheet is directly irradiated onto the sheet 1, the ratio of ultraviolet rays to illuminance is approximately 8.4.
810' W/cd/Q, x was shown.

That is, the ultraviolet light component is reduced by a little less than half due to the reflection by the reflection plate 33.

FIG. 2 is a graph in which the spectral reflectance of the reflection plate 33 is determined by n1.

The reflectance in the ultraviolet light region B2 is lower than that in the visible light region B1. Due to this difference in reflectance, the light reflected from the reflector is
The ratio of ultraviolet light components to visible light components is decreasing.

FIG. 3 shows the elapsed time (seconds) after the start of irradiation and the sheet when the stimulable phosphor sheet 1 is irradiated with X-rays of 200 mH and then the sheet 1 is irradiated with light using the fluorescent lamp 32. 1 is a graph showing the relationship between the amount of radiation energy remaining in 1 (relative ff1 when the initial value is 1).

Graph cl, C2 represents the aperture 32b of the fluorescent lamp 32.
2 is a graph of experimental results when the sheet 1 is directly irradiated with light with the light directed toward the sheet 1 side. Graphs D, D2, which will be described later
Compared to this, residual energy elimination by visible light and energy accumulation by ultraviolet light are balanced at a fairly high level.

Graph DI + DZ is a graph of experimental results when the aperture of the fluorescent lamp 32 was directed toward the reflecting plate 33 and the sheet 1 was irradiated with light reflected from the aperture. The residual energy elimination by visible light and the like and the energy accumulation by ultraviolet light are balanced at a considerably lower level than in the graphs Ct and C2.

In this way, the level of energy (fog) remaining on the sheet 1 after noise erasing is determined by the proportion of ultraviolet light included in the noise erasing light.

FIG. 4 is a diagram showing changes in the fog level when a predetermined external light is irradiated after various fog levels on the sheet 1 after erasing with the noise erasing device. The horizontal axis is the ultraviolet light (m
W/cj), and the vertical axis indicates the amount of remaining energy (relative amount) as in FIG.

The amount of ultraviolet light of the noise canceling device was adjusted to generate residual energy (fog) corresponding to each mark on sheet 1, and then in this experiment, when the device was placed under external light with a constant amount of light for a certain period of time, each corresponding The amount of remaining energy has changed to correspond to the 0 mark. In other words, when the residual energy at the noise canceling device is small, the amount of remaining energy increases by irradiating with external light, and when the amount of remaining energy at the noise canceling device is large, the amount of remaining energy increases by irradiating with external light. is decreasing. The point where this broken line connecting the ・ marks and the solid line connecting the 0 marks intersect is approximately 3X on the horizontal axis.
10' mW/c/1x (7) point tear, the amount of remaining energy at this time is shown in the graph DI + D shown in Figure 3.
It almost matches the balance point of Z. That is, an appropriate amount of ultraviolet light is irradiated onto the sheet 1 by the combination of the aperture type fluorescent lamp 32 and the aluminum reflector 33 in this embodiment.

In this way, the noise canceling device 31 in this embodiment is
The aperture 32b of the fluorescent lamp 32 is directed toward the aluminum reflector plate 33, and light is irradiated onto the reflector plate 33, so that the energy remaining in the stimulable phosphor sheet 1 is erased by the light reflected from the reflector plate 33. Therefore, noise can be eliminated so as to cause appropriate fogging on the sheet 1.

By causing an appropriate level of fog on the sheet 1 in this way, before reusing the sheet 1, it is possible to prevent the sheet 1 from becoming dirty due to light leakage from the cassette 2 or from opening the lid of the cassette 2. Even if 1 is irradiated with external light, no problem will occur even if it is reused as is.

(Effects of the Invention) As explained in detail above, according to the noise canceling device for a stimulable phosphor sheet of the present invention, the noise canceling device for a stimulable phosphor sheet of the present invention can reduce the amount of light reflected from a reflector whose reflectance for ultraviolet light is lower than that of visible light. Since the radiation energy remaining in the stimulable phosphor sheet is emitted by light, the remaining energy in the stimulable phosphor sheet can be erased with a simple configuration without using any special optical filter, and the remaining energy in the stimulable phosphor sheet can be erased. Moderate fogging can be caused, and even if a portion of the sheet is exposed to external light, the sheet can be reused as is.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of a radiation image information reading device incorporating an embodiment of the noise canceling device of the present invention, Fig. 2 is a graph of the spectral reflectance of a reflector, and Fig. 3 is a graph of the spectral reflectance of a stimulable phosphor sheet. FIG. 4 is a graph showing the relationship between the elapsed time after the start of irradiation and the amount of energy remaining in the sheet when radiation energy is accumulated and the sheet is irradiated with light to release the energy. Figure 5A is a diagram showing various levels of fog on a sheet after it has been erased with a noise canceling device, and the change in fog level when the sheet is then irradiated with a certain amount of external light. Side view of an example, No. 5B
The figure is an enlarged cross-sectional view taken along line xx' in FIG. 5A. 1...Stormable phosphor sheet 2...Cassette 10.
...Cassette holding section 12...Sheet take-out means 20...Reading section 21
A...Excitation light 30...Eraser section 32...Aperture type fluorescent lamp 40...First sheet conveyance section 50...Second sheet conveyance section 60...Third sheet conveyance section 22...Photoelectric reading means 31...Noise erasing device 33...Reflector plate 0'sF mark-・Gin → key- To, CH eMo 11

Claims (1)

[Scope of Claims] A stimulable phosphor sheet noise canceling device that irradiates light onto a stimulable phosphor sheet capable of repeatedly recording and reading radiation images, and emitting remaining radiation energy after the reading is completed, comprising: a light source that emits light including visible light and ultraviolet light, and is arranged so as to emit light in a direction that does not directly illuminate the sheet placed at a predetermined position; and a light source that emits light including visible light and ultraviolet light; 1. A noise canceling device for a stimulable phosphor sheet, comprising a reflective plate having a lower reflectance in the ultraviolet light region than in the visible light region.