JPS63175572A - Photodetector - Google Patents

Abstract

PURPOSE:To attain photodetection with high accuracy by covering with a light shield material from the side face of a filter to the side of a photodetecting face so as to cut off a light made incident in the photodetection face without passing through the filter. CONSTITUTION:A elongated photomultiplier 5 having a photodetecting face 5a extended along the scanning line of a excited light 1a in a picture information reader while its photodetecting face 5a is arranged close to the sheet 3 toward the sheet 3, and a filter 6 provided incorporatedly with the photomultiplier tube 5 and transmitting selectively stimulated luminous light placed between the photodetecting face 5a and the scanning line are provided. The side face of the filter 6 is coated by a light shield material to the side of the photodetecting face 5a of the photomultiplier 5. Thus, it is prevented that the excited light 1a reflected in the vicinity of scanning is made incident in the photodetecting face 5a of the photomultiplier tube 5 not through the filter 6 causing noise in the reproduced picture.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a photodetection device used in a radiation image information reading device that reads radiation image information, and more particularly, to a photodetection device that is small and high performance. It is related to.

(Conventional technology) Certain 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 emitted OA ray energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, it It is known that phosphors exhibit stimulated luminescence, and phosphors exhibiting such properties are called stimulable phosphors (stimulable phosphors).

Using this stimulable phosphor, radiographic image information of a subject such as a human body is partially recorded on the storable A/I phosphor in the shape of a sheet. is scanned with excitation light such as a laser beam to generate stimulated luminescence light, and the resulting stimulated luminescence light is read photoelectrically to generate an image signal 8.
The present applicant has already proposed a radiation image information recording and reproducing system that outputs a radiation image of a subject as a visible image to a recording material such as a photographic light-sensitive material, a CRT, etc. based on this image signal. (Japanese Patent Publication No. 55-12429 Tan,
No. 56-11395, No. 55-163472, No. 5
No. 6-104645.

No. 55-116340, etc.) tIi vertical line image information reading device for reading radiation image information in the above system. Excitation of laser light, etc. while sub-scanning the stimulable phosphor sheet on which the radiation image information is stored and recorded. Main scanning is performed with light to generate stimulated luminescence light from substantially the entire surface of the sheet, and the resulting stimulated luminescence light is read photoelectrically to detect an image signal.

The radiation image information reading device has a built-in photodetection device that includes a photomultiplier and the like that photoelectrically detects light containing stimulated luminescence light. Hereinafter, a radiation image information reading device equipped with a conventional photodetector will be explained with reference to FIG.

Excitation light 101 with a constant intensity emitted from an excitation light source 101
a is made incident on the galvanometer mirror 102, and by this galvanometer mirror 102, the stimulable phosphor sheet 1 placed below the galvanometer mirror 102.
The excitation light is deflected so that the excitation light performs main scanning (scanning in the six directions of arrows) in the width direction of the stimulable phosphor sheet 10.
Irradiate to 3. Since the stimulable phosphor sheet 103 is attracted to, for example, an endless belt device 1090 and conveyed in the direction of arrow B, main scanning is repeated at an angle substantially perpendicular to this sub-scanning, and the stimulable phosphor sheet 103 is Two-dimensional scanning is performed over the entire surface of 103 using excitation light 101a.

The part of the stimulable phosphor sheet irradiated with the excitation light 101a according to the scanning by the excitation light 101a emits stimulated light according to the image information stored there, and this emitted light is transmitted to the stimulable phosphor sheet. The light enters the light guide 104 from the incident end surface 104a of the transparent light guide 104, which has an incident end surface 104a formed parallel to the main scanning line in the vicinity. This light guide 1
04 is a stimulable phosphor sheet. The front end 104b located near the 103 is formed into a planar shape and gradually becomes cylindrical toward the rear end, and the rear end 104C has a substantially cylindrical shape. The injection end surface 104d
Since it is coupled to the photomultiplier 105 provided above, the stimulated luminescent light entering from the incident end face 104a is guided to the rear end 104C, and a filter (not shown) that selectively transmits the stimulated luminescent light is guided to the rear end 104C. is transmitted to the photomultiplier 105 via the photomultiplier 105. Photo multiplier-105
, the stimulated luminescence light is converted into an electrical signal, and the obtained electrical signal is sent to the image information reading circuit 106 and processed, and then output as a visible image to the CRT 107 or recorded on the magnetic chip 7108. or directly recorded as a hard copy on a photographic material, etc.

(Problems to be Solved by the Invention) In the above-mentioned device, a photodetection device consisting of the light guide 104 and the photomultiplier 105 is incorporated to detect stimulated luminescence light. However, the light guide in the conventional photodetecting device uses photomultiply V-1 with a small width in the main scanning direction by total reflection of the stimulated luminescence light incident from the human IJJQ surface 104a provided along the main scanning line. As shown in the figure, the light detecting device equipped with such a light guide, and furthermore, the entire reading device becomes large in size. In addition, as mentioned above, the stimulated luminescence light that is transmitted through the large light guide by total internal reflection may pass through the light guide without being totally reflected at an angle, so that Such large light guides also have problems with light transmission efficiency. Furthermore, the above light guide is
Deforming a light-guiding sheet-like member such as an acrylic plate into a straight line at one end corresponding to the incident end surface and into a shape (e.g., cylindrical) that matches the light-receiving surface of the photomultiplier at the other end corresponding to the exit end surface. It is difficult to process because it is made by
There is also the problem that the processing cost becomes high and the manufacturing cost of the photodetecting device increases.

Therefore, in view of the above problem, the applicant of the present application has developed a system that uses a long photomultiplier tube with a light-receiving surface extending along the main scanning line to emit photosensitivity from a sheet without using a large and complex-shaped light guide. A photodetection device has been proposed that detects emitted light and can be miniaturized, improve light collection efficiency, and reduce manufacturing costs (Japanese Patent Application No. 156255/1986, etc.).

The present invention was made in connection with a photodetector using the long photomultiplier tube described above, and the excitation light reflected in the vicinity of scanning enters the light-receiving surface of the photomultiplier tube without passing through a filter and is reproduced. The object of the present invention is to provide a photodetecting device that does not cause image noise.

(Means for Solving the Problems) The photodetecting device of the present invention has a light receiving surface extending along a scanning line of excitation light in an image information reading device, and the light receiving surface is directed toward the sheet. A long photomultiplier tube disposed close to the photomultiplier tube, and a photomultiplier tube provided integrally with the photomultiplier tube and positioned between the light receiving surface and the scanning line, selectively transmitting the stimulated luminescent light. The device is characterized in that the filter is provided with a filter, and a side surface of the filter to a side of the light receiving surface of the photomultiplier tube is covered with a light shielding material.

The elongated photomultiplier tube has a light-receiving surface arranged along the main scanning line, and has a shape that allows light emitted from the scanning position to be detected at any position in the main scanning direction. It is particularly desirable that the length of the light-receiving surface of this long photomultiplier tube be equal to or longer than the reading scanning width on the surface to be scanned, but it may be slightly shorter than that. In particular, when a small light guide (described later) is provided on the light-receiving surface E of the photomultiplier tube, the length of the light-receiving surface can be reduced by making the shape of the light guide gradually wider toward the main scanning line. Efficient light detection can be performed even if the scanning width is somewhat shorter than the reading scanning width on the sheet. Further, the filter may be disposed between the light-receiving surface and the scanning line, and may be directly provided on the light-receiving surface.
The above-mentioned small-sized light guide may be bonded onto the light-receiving surface, and the light guide may be provided on the stimulated emission light incident surface of the light guide. In addition, since the above-mentioned filter and, if necessary, a light guide etc. are connected to the light-receiving surface of the photomultiplier tube in this way, it is difficult to place six tubes close to the surface to be scanned. In order to be able to place these light guides and filters on the light-receiving surface, the photomultiplier tube should be placed away from the scanned surface by the thickness of these optical elements and as close to the scanning line as possible. It means to do something.

(Function) The photodetector of the present invention is equipped with a long photomultiplier tube disposed close to the scanned surface as described above, thereby eliminating the need for a conventional large and complex-shaped photodetector. Light emitted from a sheet of stimulated luminescence can be made incident on the light-receiving surface of a photomultiplier tube without using a light guide, making it possible to miniaturize the device and improve photodetection efficiency. If the intensifier tube is long, there is a problem that light other than stimulated luminescence light, such as excitation light reflected at the scanning position, is likely to enter the light receiving surface. If the light enters from the joint between the filter and the light-receiving surface without passing through the filter, this reflected light will be detected and cause noise in the reproduced image, which is not preferable. By covering the sides with the light-shielding material, light that attempts to enter the light-receiving surface without passing through the filter is blocked, and highly accurate light detection can be performed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an outline of a radiation image information reading device equipped with a photodetection device according to an embodiment of the present invention.

Excitation light 1a emitted from excitation light source 1 enters galvanometer mirror 2, is reflected and deflected, and passes over stimulable phosphor sheet 3, which is conveyed in the direction of arrow B by endless belt device 9, which is a sub-scanning means, in the direction of arrow 6. Main scan in the direction. The scanning position on the stimulable phosphor sheet 3 irradiated with the excitation light 1a emits stimulated light according to the image information stored there. As a means for detecting the stimulated luminescence light emitted from this scanning position, in this apparatus, a long photomultiplier tube (photomultiplier) is installed in the vicinity of the stimulable phosphor sheet 3.
) 5 is provided.

It is particularly preferable that the photomultiplier 5 has its light receiving surface 5a arranged along the main scanning line so that stimulated luminescence emitted from any position in the main scanning direction can efficiently enter the interior from the light receiving surface 5a. The length of the light receiving surface 5a is longer than the reading scanning width on the sheet 3. Further, caps 5B are attached to both ends of the main body 5A of the photomultiplier 5.

Conventional photomultipliers are generally divided into several types depending on the structure of the electrodes in the multiplier part, which is provided inside the main body and multiplies a minute photocurrent to an appropriate level. Multipliers can be created by extending these various photomultipliers in a direction perpendicular to their sides. Figure 2 (
a).

The photomultiplier 5 used in this embodiment shown in FIG. 2(b), which is a cross-sectional view taken along the line I-I, has an electrode structure generally referred to as a Venetian blind type. be. The photomultiplier shown in FIG. 2(a) is shown with the cap 5B removed for convenience.

This photomultiplier 5 has a main body 5Δ made of glass having a cylindrical shape, and a photocathode 5b is provided along the main body 5A facing the light-receiving surface 5a. A plurality of dynodes 5C (13 in this embodiment) are stacked below via an insulating member 5d to form a bottle 5C.
is fixed to constitute the multiplier 5f. Each of the dynodes 5C is formed by making a large number of U-shaped cuts in one conductive plate and bending the plate to form a blind shape. A shield electrode 5g is fixed with a bottle 5e below the multiplier 5f via an insulating member 5d, and an anode 5h is provided within the shield electrode 5g. These electrodes are electrically connected in one-to-one correspondence to the respective legitimate children of the terminal group 51 provided at the end of the main body 5A.

FIG. 3 shows an electric circuit 12 for driving the photomultiplier 5 and extracting a photoelectric output, and parts corresponding to each part of the photomultiplier 5 are given the same reference numerals. A negative high voltage is applied to the photocathode 5b via the negative high voltage application terminal 12a. Further, the negative high voltage applied to the negative high voltage application terminal 12a is divided by the bleeder resistor group 12b and applied to the dynodes 5C, respectively. In addition, the shield electrode 5
9 is grounded, and the anode 5h is grounded via a resistor 12c and is input to one terminal of an amplifier 12d. The other terminal of the amplifier 12d is grounded, and the photoelectrically converted image information is taken out as an electrical signal from the output terminal 12e. Note that the shield electrode 5g does not necessarily have to be provided.

By the way, among various image reading devices, in the above-mentioned radiation image information reading device, it is especially important to efficiently guide the stimulated luminescent light, which is the light emitted from the stimulable phosphor sheet, to the light receiving surface of the photomultiplier. Needed. Furthermore, when the excitation light is incident on the stimulable phosphor sheet, a part of it may be reflected on the stimulable phosphor sheet, and a part of the reflected light may reach the light receiving surface of the photomultiplier. ,
The photomultiplier needs to correctly detect only the stimulated luminescence light and not detect the reflected light of the excitation light. Therefore, in the device of this embodiment, a long filter 6 and a small light guide 4 are joined to the long photomultiplier 5 on its light receiving surface 5a.
A photomultiplier 5, a filter 6, and a light guide 4 constitute a photodetector 10. Further, a black paint, which is a light-shielding material, is applied to the circumferential surface of the photodetector 10. Refer to FIG. 4(a'), which is an enlarged perspective view of the photodetector 10, and FIG. 4(b), which is a sectional view taken along line ■-■ (however, the internal structure of the photomultiplier is omitted). The photodetecting device of this example will be further explained.

On the light-receiving surface 5a of the photomultiplier 5, a filter 6 is bonded via an ultraviolet curing adhesive 7, which is an example of a light transmitting agent. A light guide 4 is integrally arranged. The filter 6 selectively transmits only light in the wavelength region of stimulated luminescence light, thereby cutting off the light reflected by the excitation light on the sheet 3. On the other hand, the light guide 4 described in "1" transmits the stimulated luminescence light emitted from the scanning position to the photomultiplier 5 by total reflection, and the light guide used in this light detection device is as shown in the figure. The length from the light entrance surface to the light exit surface is extremely short.
Since the shape is simple, there is no risk of causing problems such as an increase in the size of the device and an increase in manufacturing costs, unlike conventional light guides.

When detecting stimulated luminescence light by the photodetector 10, part of the excitation light reflected at the scanning position, which passes through the light guide 4 and enters the filter 6, is cut by the filter 6. However, as shown by the arrow a in FIG. 4(b), the reflected light of the excitation light is incident from the adhesive 7 or the like having optical transparency without passing through the filter 6. may be transmitted to the light-receiving surface 5a. If the photo multi-briar is long,
Since the area where the reflected light can be incident becomes larger, the sea 1
The above-mentioned reflected light, which is scattered by being reflected by surrounding members after being reflected at the top, enters from these parts and has a high possibility of interfering with highly accurate detection of stimulated luminescence light. Also,
- In addition to the reflected light of the excitation light, when other light from the outside world enters from the circumferential surface of the photomultiplier 5 as shown by the arrow in FIG. Since the main body 5Δ of --5 is usually made of glass or the like, the incident light may be transmitted to the light-receiving surface 5a. Therefore, in this embodiment, the photodetector 1
0, black paint 8 is applied to all surfaces of the light guide 4 and filter 6 except for the top surfaces. By applying the black paint 8 in this way, the applied area is shielded from light, and the light that enters the light receiving surface 5a is only the light that has passed through one filter 6.
Reflected light of the excitation light and the like are no longer transmitted to the light receiving surface 5a. Note that the reason why black paint is not applied to the side surfaces of the light guide 4 is to bring the light guide 1 into contact with the outside air so that the incident light is fully reflected in a good manner. In addition, if you use epoxy paint as the black paint, it will
Hemalgiply A7 is preferred because it has good adhesion to the main body.

In the reading device equipped with the above-mentioned photodetection means 10,
Stimulated luminescence light emitted from the scanning position is efficiently guided by the light guide 4 and transmitted to the photomultiplier 5 via the filter 6.

The stimulated luminescent light is converted into an electrical signal in this photomultiplier 5, and the jqed electrical signal is sent to an image information reading circuit (not shown) and processed, and then output as a visible image on a CRT or magnetic be recorded on tape.

As described above, the photodetection means according to this embodiment has a long photomultiplier whose light-receiving surface is arranged along the main scanning line, and is arranged close to the stimulable phosphor sheet.
The large and complicated shapes that were conventionally used,
A light guide, which is expensive to manufacture, is not required, the entire device can be made smaller and the manufacturing cost 1- can be reduced, and the reading device in which the photodetector is incorporated can also be made more compact. Furthermore, since the scanning position where the stimulated luminescence light is generated and the light receiving surface are close to each other, it is possible to improve the light collection efficiency compared to the case where the stimulated luminescence light is transmitted by a conventional light guide. Furthermore, in the device of this example, by covering the circumferential surface of the photodetector with the aforementioned J: sea urchin black paint, light other than stimulated luminescence light, such as reflected light of excitation light, enters the photomultiplier. This eliminates the inconvenience of noise in the reproduced image. Furthermore, if black paint is used as the light-shielding material, the uneven circumferential surface of the photodetector can be easily covered with the light-shielding material, resulting in extremely good workability.

Note that a long photomultibrier is not limited to the Venetian blind type mentioned above, but can also be created by extending a photomultibrier equipped with a multiplier made of other types of conventionally known electrodes. Is possible. Figure 5(a).

(b) shows a 7AI multiplier 15 used in the present invention, which has an electrode structure generally called a box type. This photo multiplier-1! + indicates that the interior is made of glass or the like and has a vacuum inside. A photoelectrode (photocathode) 15b for emitting photoelectrons is provided in the main body 15A, facing a long light-receiving surface 15a.
A multiplier section 15d in which a plurality of quarter-cylindrical electrodes (dynodes) 15C having a secondary electron emission effect are combined is disposed on the side of the photocathode 15b. This multiplier 15d
The shield electrode 1 is placed opposite the dynode 15c at the bottom of the
5e, and an anode 15f that collects the electron flow multiplied by the multiplier and outputs it to the outside as a signal is further arranged within the shield electrode 15e. Each of these electrodes is electrically connected on a one-to-one basis to each terminal of the terminal group 159, the number of which corresponds to the number of electrodes provided on the opposite side of the light-receiving surface 15a. Note that the dynode 15c and the shield electrode 15e are fixedly held within the main body 15A by a support member 15h formed of an insulator.

Note that the shield electrode 15e does not necessarily need to be provided in this embodiment as well. This photo multiplier
To take out the photoelectric output from 15, a circuit exactly the same as that shown in FIG. 3 may be used.

In addition, the elongated photomultiplier used in the present invention may include a multiplier section made of other conventionally known types of electrodes or a multiplier section formed by combining a plurality of types of electrodes. It can be created by extending the multiplier.

Furthermore, if the black paint is applied to the entire surface of the device other than the light guide as shown in the example above, the light shielding effect will be extremely high. If it is necessary to mainly prevent light from entering, it is sufficient to block light from at least the filter to the sides of the light-receiving surface of the photomultiplier. Furthermore, the structure and arrangement of the filter are not limited to those of the above embodiments. Hereinafter, other embodiments of the photodetecting device of the present invention will be described with reference to FIG.

FIG. 6 <a> shows an example of adhesive 7 on the light receiving surface 5a of a Venetian blind type photomultiplier.
The light guide 14' is joined through the light guide 14'.
′ is colored to selectively transmit only light in the wavelength range of stimulated luminescence light and absorb light in the wavelength range of excitation light, and has the function of a filter. In this case, since the total length L1 of the light guide 14 is determined for the purpose of good light collection, only the length L2 of the light guide 14', which is sufficient to act as a filter, is considered to be the filter portion. It is sufficient to cover the sides of the light-receiving surface 5a with the black paint 8. The reflected light of the excitation light incident from the side surface of the light guide other than the covered portion is sufficiently attenuated by the filtering action of the light guide 14'.
It is not transmitted to the light receiving surface. For example, if the length L2 to which black paint is applied is 3.5 m, the amount of reflected light of the excitation light incident on the light receiving surface 5a is reduced to about 1/109 compared to the case where no black paint is applied. be able to. Further, as shown in FIG. 6(1), for example, a light guide 4 is bonded onto the light receiving surface 15a of a box-shaped photomultiplier 15, and the above-mentioned filter 6 is bonded onto the incident end surface of this light guide 4. You may. In this case, light must be continuously blocked from the side of the filter 6 to the side of the light-receiving surface 15a, but since the side of the light guide 4 needs to be in contact with the outside air, the light guide is 4
The width of the light-shielding material 18 may be made smaller than the width of the filter 6, and a light-shielding plate, a light-shielding chip, etc. may be used as the light-shielding material 18, and both ends thereof may be fixed onto the photomultiplier 15 and the filter 6, respectively.

(Effects of the Invention) As described in detail above, the photodetection device of the present invention has a long photomultiplier disposed close to the stimulable phosphor sheet along the scanning line. According to
Stimulated luminescence light emitted from a sheet can be detected without using a conventional large-sized, double-N shaped light guide. Therefore, it is possible to reduce the overall size and manufacturing cost of the photodetector and the reading device in which the photodetector is embedded, and it is also possible to increase the efficiency of detecting light emitted from the sheet. By covering at least the area from the filter to the light-receiving surface with the light-shielding material, light other than the stimulated luminescence light is prevented from entering the light-receiving surface, and the stimulated luminescence light can be detected with high precision.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an overview of a radiation image information reading device equipped with a photodetection device according to an embodiment of the present invention, and FIG.
A perspective view showing a blind type photomultiplier, FIG. 2(b) is a sectional view taken along the line I-I, FIG. ) is a perspective view of the photodetector, and FIG.
)) is a sectional view taken along the line ■-■, FIG. 5(a) is a perspective view showing a long box-type photomultiplier used in the device of the present invention, and FIG. 6(a) and 6(b) are perspective views of a photodetecting device according to an embodiment of the present invention, and FIG. 7 shows an outline of a radiation image information reading device equipped with a conventional photodetecting device. FIG. 1a... Excitation 9 〇... Stimulable phosphor sheet 4.14... Light guide 5.15... Photomultiplier (photomultiplier)

Claims (1)

[Scope of Claims] 1) A photodetector for detecting stimulated luminescence light emitted from a scanned surface when a stimulable phosphor sheet on which radiation image information is stored and recorded is scanned with excitation light; a long photomultiplier tube having a light-receiving surface extending along the scanning line of the excitation light and disposed close to the sheet with the light-receiving surface facing toward the sheet; and integrally attached to the photomultiplier tube. a filter that selectively transmits the stimulated luminescence light, the filter being disposed between the light-receiving surface and the scanning line, and extending from the side of the filter to the side of the light-receiving surface of the photomultiplier tube. 1. A photodetecting device characterized by being coated with a light-shielding material. 2) The photodetecting device according to claim 1, wherein the light-shielding material is black paint.