JP2023061996A - Radiation image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image reading device with which it is possible to both reduce the device size and maintain the accuracy of reading radiation images.

SOLUTION: The radiation image reading device comprises: an optical scan unit for scanning excitation light along a scan line located on the surface of an imaging plate against the surface of an imaging plate on which a radiation image is recorded; and a light detection unit 7 for detecting, in a detection plane that includes the scan line and intersects the surface of the imaging plate, signal light radiated from the surface of the imaging plate by scanning of excitation light. The light detection unit 7 is a multi-pixel photon counting device that includes a plurality of photodiodes 71 arranged along a direction that is parallel to the scan line. The plurality of photodiodes 71 are controlled as one channel. Electric signals outputted from the plurality of photodiodes 71 are summed and outputted from the light detection unit 7.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a radiation image reader.

A radiographic image comprising: a light scanning unit that scans the surface of a recording medium on which a radiographic image is recorded with excitation light; and a light detection unit that detects signal light emitted from the surface of the recording medium by the scanning of the excitation light. A reader is known (see, for example, Patent Document 1).

JP-A-2002-77548

A radiographic image reading apparatus such as that described above is sometimes required to be downsized. However, if, for example, the photodetector is arranged so that the distance from the surface of the recording medium becomes small in order to reduce the size of the device, the reading accuracy of the radiographic image may decrease.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a radiographic image reading apparatus capable of achieving both reduction in device size and maintenance of radiographic image reading accuracy.

The radiation image reading apparatus of the present invention includes an optical scanning unit that scans the surface of a recording medium on which a radiation image is recorded with excitation light along scanning lines, and a scanning line that intersects the surface of the recording medium. A photodetector for detecting signal light emitted from the surface of the recording medium by scanning the excitation light in the detection plane, and an optical filter disposed between the surface of the recording medium and the photodetector, Transmittance of the excitation light reflected by the surface of the recording medium through the optical filter and emission from the surface of the recording medium at an angle greater than a predetermined angle with respect to the direction perpendicular to the scanning line in the detection plane The transmittance of the signal light emitted from the surface of the recording medium forms an angle smaller than a predetermined angle with respect to the direction perpendicular to the scanning line in the detection plane. It is smaller than the transmittance through the optical filter.

In this radiological image reader, the transmittance of the excitation light reflected on the surface of the recording medium through the optical filter and the signal light emitted from the surface of the recording medium at an angle larger than a predetermined angle are optically measured. Each transmittance through the filter is smaller than the transmittance through the optical filter of the signal light emitted from the surface of the recording medium at an angle smaller than the predetermined angle. This suppresses deterioration in reading accuracy of the radiographic image due to the excitation light entering the photodetector. Further, even if the photodetector is arranged so that the distance from the surface of the recording medium is small and the length of the photodetector in the direction parallel to the scanning line is limited, in order to reduce the device size, A decrease in reading accuracy of a radiographic image due to the signal light having a divergence angle is suppressed. The reason why the radiation image reading accuracy is lowered due to the divergence angle of the signal light is as follows. That is, since the signal light emitted from the surface of the recording medium has a divergence angle, in order to reduce the size of the device, the photodetector is arranged so that the distance from the surface of the recording medium is small, and the scanning line is aligned. When the length of the photodetector in the parallel direction is limited, for example, all of the signal light enters the photodetector at the center of the scanning line, whereas all of the signal light is incident on the both ends of the scanning line. This is because the light does not enter the photodetector. In other words, in this radiation image reading apparatus, even if the device size is reduced, a difference occurs in the detection range of the signal light emitted from the surface of the recording medium between the central portion and both ends of the scanning line. is suppressed. As described above, according to this radiographic image reading apparatus, it is possible to achieve both reduction in device size and maintenance of radiographic image reading accuracy.

In the radiation image reading apparatus of the present invention, when the excitation light scanning region and the signal light detection region are in a centered positional relationship in the detection plane, the width of the scanning region is W1 and the width of the detection region is W2. (>W1), the distance between the scanning area and the detection area is D, and the predetermined angle is θ, then θ=tan ⁻¹ {(W2−W1)/2D} may hold. According to this configuration, since the detection range of the signal light emitted from the surface of the recording medium is the same between the central portion and both ends of the scanning line, it is possible to more reliably suppress deterioration in reading accuracy of the radiation image. can be done.

In the radiation image reader of the present invention, the optical filter comprises a glass plate, a first dielectric multilayer film formed on one surface of the glass plate, and a second dielectric multilayer film formed on the other surface of the glass plate. and the transmittance of the excitation light reflected on the surface of the recording medium through the first dielectric multilayer film and the second dielectric multilayer film, and the transmittance in the direction perpendicular to the scanning line in the detection plane On the other hand, the transmittance of the signal light emitted from the surface of the recording medium at an angle larger than the predetermined angle is transmitted through the first dielectric multilayer film and the second dielectric multilayer film. The transmittance is smaller than the transmittance of the signal light emitted from the surface of the recording medium at an angle smaller than a predetermined angle with respect to the direction perpendicular to the line through the first dielectric multilayer film and the second dielectric multilayer film. may With this configuration, it is possible to easily and reliably obtain an optical filter having the functions described above.

The radiation image reader of the present invention is arranged between the surface of the recording medium and the optical filter, and emits excitation light reflected by the surface of the recording medium and emitted from the surface of the recording medium only in a plane perpendicular to the detection surface. An optical element having a function of converging the signal light may be further provided. According to this configuration, it is possible to use a photodetector that includes a plurality of photodetectors arranged along a direction parallel to the scanning line.

In the radiographic image reader of the present invention, the photodetection section may include a plurality of photodetection elements arranged along a direction parallel to the scanning line, and the plurality of photodetection elements may be controlled as one channel. . According to this configuration, a radiation image can be read with a simpler configuration.

According to the present invention, it is possible to provide a radiographic image reading apparatus capable of achieving both reduction in device size and maintenance of radiographic image reading accuracy.

1 is a configuration diagram of a radiographic image reading apparatus according to an embodiment, and is a diagram at the time of radiographic image reading; FIG. FIG. 2 is a perspective view of a portion of the radiographic image reading apparatus of FIG. 1; FIG. 2 is a configuration diagram of a photodetector of the radiation image reading apparatus of FIG. 1; FIG. 2 is a configuration diagram of an optical filter of the radiographic image reading apparatus of FIG. 1; FIG. 5 is a diagram showing transmittance characteristics for one embodiment of the optical filter of FIG. 4; 2 is an enlarged view of a portion of the radiographic image reading apparatus of FIG. 1; FIG. FIG. 2 is a configuration diagram of the radiographic image reading apparatus in FIG. 1, and is a diagram at the time of erasing the radiographic image. FIG. 7 is a cross-sectional view along line VIII-VIII of FIG. 6; It is a figure which shows the intensity distribution of the light with respect to the scanning position of excitation light. (a) It is a block diagram of the optical filter of a 1st modification. (b) It is a block diagram of the optical filter of a 2nd modification. (c) It is a block diagram of the optical filter of a 3rd modification.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted.

As shown in FIG. 1, the radiographic image reader 1 includes a housing 2, a plurality of conveying roller pairs 3, a carry-in detection sensor 4, an optical scanning unit 5, an optical element 6, an optical filter 10, A photodetector 7 and a radiation image eraser 8 are provided. The radiographic image reader 1 is a device that reads a radiographic image recorded on an imaging plate (recording medium) IP.

The housing 2 accommodates a plurality of conveying roller pairs 3, a carry-in detection sensor 4, an optical scanning unit 5, an optical element 6, an optical filter 10, a light detecting unit 7, a radiation image erasing unit 8, and the like. The housing 2 protects the components housed in the housing 2 from the outside and shields them from the outside. The housing 2 is provided with a carry-in port 2a through which the imaging plate IP is carried in and a carry-out port 2b through which the imaging plate IP is carried out. The carry-in port 2a is provided in one wall portion of the housing 2 in the X-axis direction. The carry-out port 2b is provided in the other wall portion of the housing 2 in the X-axis direction.

The plurality of conveying roller pairs 3 are arranged side by side along the X-axis direction while being separated from each other. A pair of rollers 31 constituting each conveying roller pair 3 extends along the Y-axis direction and faces each other in the Z-axis direction while being separated from each other. The gap between the pair of rollers 31 is substantially the same as the thickness of the imaging plate IP. The plurality of conveying roller pairs 3 are arranged such that the position of the gap between the pair of rollers 31 is substantially the same as the position of the carry-in port 2a and the carry-out port 2b in the Z-axis direction. In the radiographic image reader 1, the imaging plate IP is loaded from the loading port 2a, transported along the X-axis direction by the plurality of transport roller pairs 3, and transported from the loading port 2b.

The carry-in detection sensor 4 is arranged near the carry-in opening 2 a of the housing 2 . The carry-in detection sensor 4 detects that the imaging plate IP is carried in when the imaging plate IP is carried in from the carry-in port 2a. As the carry-in detection sensor 4, for example, a mechanical switch (for example, D2F-01FL-D3 manufactured by Omron) may be used, or an optical detection sensor such as a photointerrupter may be used. Considering that the radiographic image recorded on the imaging plate IP may deteriorate due to irradiation with the light emitted from the photodetection sensor, it is preferable to use a mechanical switch.

As shown in FIGS. 1 and 2 , the optical scanning section 5 has an excitation light source unit 51 and a position adjustment mirror 52 . The excitation light source unit 51 includes an excitation light source (not shown) and a MEMS (Micro Electro Mechanical System) mirror (not shown). The excitation light source unit 51 emits the excitation light EL along the X-axis direction while swinging the excitation light EL about an axis parallel to the Z-axis direction. The position adjustment mirror 52 is configured such that the orientation of the reflecting surface can be adjusted with an axis parallel to the Y-axis direction as the center line. The position adjusting mirror 52 reflects the excitation light EL emitted from the excitation light source unit 51 onto the scanning line L. As shown in FIG. The scanning line L is a virtual line positioned on the surface IPa (the surface on which the radiation image is recorded) of the imaging plate IP conveyed by the plurality of conveying roller pairs 3, and is, for example, a line parallel to the Y-axis direction. . In the radiation image reader 1, the optical scanning unit 5 scans the surface IPa of the imaging plate IP on which the radiation image is recorded with the excitation light EL along the scanning lines L (that is, along the scanning lines L reciprocate the irradiation area (condensing area) of the excitation light EL).

The photodetector 7 is arranged so as to face the scanning line L in the Z-axis direction. The photodetector 7 detects the signal light FL emitted from the surface IPa of the imaging plate IP by scanning the excitation light EL within the detection surface S. The detection plane S is a virtual plane that includes the scanning line L and intersects the surface IPa of the imaging plate IP, for example, a plane parallel to the YZ plane.

As shown in FIG. 3 , the photodetector 7 has a plurality of photodiodes (photodetector elements) 71 , switches 72 , amplifiers 73 , and A/D converters 74 . The photodetector 7 is specifically an MPPC (Multi-Pixel Photon Counter). The MPPC is a photon counting device consisting of multiple photodiode 71 pixels. A plurality of photodiodes 71 are arranged along the Y-axis direction (that is, the direction parallel to the scanning line L). A plurality of photodiodes 71 are connected in parallel to one end of one switch 72 via wiring 75 . An amplifier 73 is connected to the other end of the switch 72 . An A/D converter 74 is connected to the amplifier 73 . Potentials having relatively different polarities are applied to the photodiode 71 . One of the potentials V2 may be the ground potential.

When the signal light FL is incident on the photodetector 7, each photodiode 71 outputs an electrical signal according to the light amount of the incident signal light FL. The electrical signals output from each photodiode 71 are added together and output to, for example, a control section (not shown) via an amplifier 73 and an A/D converter 74 . That is, the multiple photodiodes 71 are controlled as one channel.

As shown in FIGS. 1 and 2, the optical filter 10 is arranged between the scanning line L and the photodetector 7 . That is, the optical filter 10 is arranged between the surface IPa of the imaging plate IP conveyed by the plurality of conveying roller pairs 3 and the photodetector 7 . The optical filter 10 attenuates the excitation light EL reflected by the surface IPa of the imaging plate IP. Further, the optical filter 10 attenuates the signal light FL emitted from the surface IPa of the imaging plate IP at an angle larger than a predetermined angle with respect to the direction perpendicular to the scanning line L in the detection plane S, and detects the light. The signal light FL emitted from the surface IPa of the imaging plate IP at an angle smaller than a predetermined angle with respect to the direction perpendicular to the scanning line L in the plane S is transmitted. The optical filter 10 transmits the signal light FL emitted from the surface IPa of the imaging plate IP at a predetermined angle with respect to the direction perpendicular to the scanning line L in the detection plane S.

Here, "attenuating the excitation light EL reflected by the surface IPa of the imaging plate IP" means that the transmittance of the excitation light EL through the optical filter 10 is less than 50% on average. “Attenuating the signal light FL emitted from the surface IPa of the imaging plate IP at an angle larger than a predetermined angle with respect to the direction perpendicular to the scanning line L within the detection plane S” means that the signal light FL is less than 50% on average through the optical filter 10 . "Transmitting the signal light FL emitted from the surface IPa of the imaging plate IP at an angle smaller than a predetermined angle with respect to the direction perpendicular to the scanning line L in the detection plane S" means that the signal light FL is 50% or more on average.

As shown in FIG. 4 , the optical filter 10 has a glass plate 11 , a first dielectric multilayer film 12 and a second dielectric multilayer film 13 . The glass plate 11 has a first surface (one surface) 11a and a second surface (the other surface) 11b facing each other in the Z-axis direction. The first surface 11a is the surface of the glass plate 11 on the scanning line L side. The second surface 11b is the surface of the glass plate 11 on the side of the photodetector 7 . The glass plate 11 is a member that transmits the signal light FL. The glass plate 11 is made of colored glass that absorbs the excitation light EL. The first dielectric multilayer film 12 is formed on the first surface 11a. A second dielectric multilayer film 13 is formed on the second surface 11b. Each of the first dielectric multilayer film 12 and the second dielectric multilayer film 13 is a laminate in which SiO ₂ and Ta ₂ O ₅ are alternately laminated, for example. The first dielectric multilayer film 12 and the second dielectric multilayer film 13 are formed on the first surface 11a and the second surface 11b of the glass plate 11, respectively, by sputtering or vapor deposition, for example.

In the optical filter 10, the excitation light EL reflected by the surface IPa of the imaging plate IP conveyed by the plurality of conveying roller pairs 3 and the detection surface Attenuates the signal light FL emitted from the surface IPa of the imaging plate IP forming an angle larger than a predetermined angle with respect to the direction perpendicular to the scanning line L in the detection plane S, and perpendicular to the scanning line L in the detection plane S It transmits the signal light FL emitted from the surface IPa of the imaging plate IP at an angle smaller than a predetermined angle with respect to the direction.

FIG. 5 is a diagram showing transmittance characteristics of an example of the optical filter 10. As shown in FIG. With respect to an embodiment of the optical filter 10, the inventors have investigated various angles of light having various wavelengths (in the detection plane S, angles formed with respect to the direction perpendicular to the scanning line L (here, "incident angle )), the transmittance of light was examined when it was made incident on the optical filter 10 . As shown in FIG. 5, for a wavelength of 650 nm, which corresponds to the wavelength of the excitation light EL, the transmittance is approximately 0 regardless of the incident angle. Further, for a wavelength of 400 nm, which corresponds to the wavelength of the signal light FL, the transmittance exceeds 95% at the incident angles of 0 degrees, 20 degrees, and 40 degrees, while the transmittance at the incident angle of 60 degrees is 20%. fell below In other words, according to this example of the optical filter 10, when the wavelength of the signal light FL is 400 nm, it has been found that an angle larger than 40 degrees and smaller than 60 degrees can be set as the predetermined angle described above.

As shown in FIGS. 1 and 2, the optical element 6 is arranged between the scanning line L and the optical filter 10 . That is, the optical element 6 is arranged between the surface IPa of the imaging plate IP conveyed by the plurality of conveying roller pairs 3 and the optical filter 10 .

As shown in FIG. 6, the optical element 6 is, for example, a cylindrical rod lens whose center line is an axis parallel to the Y-axis direction. As a result, the optical element 6 converges the excitation light EL and the signal light FL incident on the optical element 6 onto the line in which the plurality of photodiodes 71 are arranged in a plane parallel to the ZX plane. On the other hand, the optical element 6 does not substantially converge the excitation light EL and the signal light FL incident on the optical element 6 within the detection surface S, and allows the light to enter the plurality of photodiodes 71 . That is, the optical element 6 emits excitation light EL reflected by the surface IPa of the imaging plate IP and emitted from the surface IPa of the imaging plate IP only within a plane perpendicular to the detection surface S (that is, a plane parallel to the ZX plane). It has a function of converging the signal light FL that has been received.

As shown in FIGS. 1 and 2, the radiographic image erasing section 8 is arranged downstream of the scanning line L in the conveying direction of the imaging plate IP. The radiation image erasing unit 8 erases the radiation image from the surface IPa of the imaging plate IP, for example, by irradiating the surface IPa of the imaging plate IP with white light. As the radiation image erasing section 8, for example, a white lamp such as a white LED (Light Emitting Diode), a fluorescent lamp, or the like is used.

The radiation image reader 1 configured as described above reads the radiation image recorded on the imaging plate IP as follows.

As shown in FIG. 1, the imaging plate IP is carried into the housing 2 through the inlet 2a with the front surface IPa of the imaging plate IP facing the photodetector 7 side. At this time, the carry-in detection sensor 4 detects that the imaging plate IP has been carried in, and the operation of the transport roller pair 3 and the optical scanning unit 5 is started. The imaging plate IP carried into the housing 2 is transported along the X-axis direction by the transport roller pair 3 . When the imaging plate IP is transported to a position facing the photodetector 7, the optical scanning unit 5 scans the excitation light EL along the scanning line L with respect to the surface IPa of the imaging plate IP. The excitation light EL scanned on the surface IPa of the imaging plate IP is reflected by the surface IPa of the imaging plate IP. At the same time, the signal light FL is emitted from the surface IPa of the imaging plate IP scanned by the excitation light EL. The photodetector 7 detects the signal light FL transmitted through the optical element 6 and the optical filter 10 . Then, as shown in FIG. 7, the imaging plate IP is carried out from the outlet 2b after the radiographic image recorded on the surface IPa of the imaging plate IP is erased by the radiographic image erasing section 8 . According to the radiographic image reader 1, the entire region of the surface IPa of the imaging plate IP in which the radiographic image is stored is irradiated with the excitation light EL, and the signal light FL is detected for the entire region. can be formed.

Next, the relationship between the scanning area of the excitation light EL and the detection area of the signal light FL will be described.

As shown in FIG. 8, in the detection surface S, the width of the scanning region R1 of the excitation light EL (the width in the Y-axis direction) is W1. The scanning region R1 of the excitation light EL refers to a range within the detection surface S in which the surface IPa of the imaging plate IP is scanned with the excitation light EL. That is, in the detection surface S, the width W1 of the scanning region R1 of the excitation light EL is the same as the length of the scanning line L. As shown in FIG. Within the detection plane S, the width of the detection region R2 for the signal light FL (the width in the Y-axis direction) is W2. The detection area R2 of the signal light FL is a range within the detection surface S in which the light detection section 7 detects light. That is, the length is the same as the length of the detection area of the plurality of photodiodes 71 arranged along the Y-axis direction. In the detection surface S, the width W2 of the detection region R2 of the signal light FL is longer than the width W1 of the scanning region R1 of the excitation light EL. In the detection plane S, the scanning region R1 for the excitation light EL and the detection region R2 for the signal light FL are aligned in the center. The centered positional relationship means that, in the detection plane S, the center position of the scanning region R1 of the excitation light EL (the center position in the Y-axis direction) and the center position of the detection region R2 of the signal light FL (the Y-axis direction). center position) coincides in the Y-axis direction. In the Z-axis direction, D is the distance between the scanning region R1 for the excitation light EL and the detection region R2 for the signal light FL. At this time, θ=tan ⁻¹ {(W2−W1)/2D} is established, where θ is the predetermined angle of the optical filter 10 described above.

As described above, in the radiation image reader 1 , the excitation light EL reflected by the surface IPa of the imaging plate IP is attenuated by the optical filter 10 . That is, the excitation light EL reflected by the surface IPa of the imaging plate IP at an angle smaller than a predetermined angle θ with respect to the direction perpendicular to the scanning line L in the detection plane S, and the scanning line L in the detection plane S excitation light EL reflected by the surface IPa of the imaging plate IP at an angle larger than a predetermined angle θ with respect to a direction perpendicular to the scanning line L, and a predetermined angle with respect to the direction perpendicular to the scanning line L in the detection surface S The excitation light EL reflected by the surface IPa of the imaging plate IP at the angle θ is attenuated by the optical filter 10 . As a result, it is possible to prevent the radiation image reading accuracy from deteriorating due to the excitation light EL entering the photodetector 7 . Further, in the radiographic image reader 1, the signal light FL emitted from the surface IPa of the imaging plate IP at an angle larger than the predetermined angle θ is attenuated by the optical filter 10 and formed at an angle smaller than the predetermined angle θ. Then, the signal light FL emitted from the surface IPa of the imaging plate IP is transmitted through the optical filter 10 . As a result, in order to reduce the size of the apparatus, the photodetector 7 is arranged so that the distance from the surface IPa of the imaging plate IP is small, and the length of the photodetector 7 in the direction parallel to the scanning line L is Even if it is limited, it is possible to prevent the reading accuracy of the radiographic image from deteriorating due to the divergence angle of the signal light FL. As described above, according to the radiographic image reading apparatus 1, it is possible to achieve both reduction in size of the apparatus and maintenance of reading accuracy of the radiographic image.

The reason why the radiation image reading accuracy is lowered due to the divergence angle of the signal light FL is as follows. That is, since the signal light FL emitted from the surface IPa of the imaging plate IP has a divergence angle, the light detection unit 7 is arranged so that the distance from the surface IPa of the imaging plate IP becomes small in order to reduce the size of the apparatus. If the length of the photodetector 7 in the direction parallel to the scanning line L is limited, for example, all the signal light is incident on the photodetector 7 at the center of the scanning line L, whereas the scanning This is because not all of the signal light FL enters the photodetector 7 at both ends of the line L (both ends of the scanning region R1 of the excitation light EL).

Specifically, as shown in FIG. 8, in the detection plane S, for example, at one end of the scanning line L, imaging is performed at an angle smaller than a predetermined angle θ with respect to the direction perpendicular to the scanning line L. A signal light FL2 (FL) emitted from the surface IPa of the plate IP, and a signal emitted from the surface IPa of the imaging plate IP forming an angle larger than a predetermined angle θ with respect to the direction perpendicular to the scanning line L. Of the light FL1 (FL), the signal light FL1 that travels toward the other end of the scanning line L in the direction perpendicular to the scanning line L enters the photodetector 7 . On the other hand, of the signal light FL1 (FL) emitted from the surface IPa of the imaging plate IP at an angle larger than the predetermined angle θ with respect to the direction perpendicular to the scanning line L, On the other hand, the signal light FL1 traveling in the opposite direction to the other end of the scanning line L does not enter the photodetector 7. As shown in FIG. As described above, a difference occurs in the detection range of the signal light FL emitted from the surface IPa of the imaging plate IP between the central portion and both ends of the scanning line L. FIG.

As described above, in the radiographic image reading apparatus 1, the optical filter 10 forms an angle larger than the predetermined angle θ with respect to the direction perpendicular to the scanning line L and emits signal light from the surface IPa of the imaging plate IP. Attenuate FL1 (FL). That is, in the radiation image reading device 1, even if the size of the device is reduced, the central portion and both ends of the scanning line L are within the detection range of the signal light FL emitted from the surface IPa of the imaging plate IP. The occurrence of a difference is suppressed.

In a conventional radiation image reader, a dielectric multilayer film that attenuates the excitation light EL reflected by the surface IPa of the imaging plate IP along the direction perpendicular to the scanning line L within the detection surface S is employed as an excitation light cut filter. As a result, the excitation light EL reflected by the surface IPa of the imaging plate IP at a predetermined angle with respect to the direction perpendicular to the scanning line L in the detection plane S may not be sufficiently attenuated. FIG. 9 is a diagram showing the intensity distribution of light detected by the photodiode 71 arranged in the center of the photodetector 7 in the Y-axis direction when such an excitation light cut filter is employed. Note that FIG. 9 shows the light intensity distribution when the excitation light EL is scanned a plurality of times along the scanning line L. (Scanning position of excitation light EL). In this case, the excitation light EL reflected by the surface IPa of the imaging plate IP at a predetermined angle with respect to the direction perpendicular to the scanning line L in the detection plane S enters the photodetector 7 . Therefore, as shown in FIG. 9, the intensity distribution of the light detected by the photodiode 71 arranged in the center of the photodetector 7 in the Y-axis direction is such that the scanning position of the excitation light EL is away from the dashed line. Enhanced on both sides. On the other hand, in the radiation image reader 1, the optical filter 10 detects not only the excitation light EL reflected by the surface IPa of the imaging plate IP along the direction perpendicular to the scanning line L within the detection surface S, but also the excitation light EL. It also attenuates the excitation light EL reflected by the surface IPa of the imaging plate IP at a predetermined angle with respect to the direction perpendicular to the scanning line L in the plane S. This suppresses the intensity distribution of the light detected by the photodiode 71 arranged in the center of the photodetector 7 in the Y-axis direction from being enhanced on both sides of the scanning position of the excitation light EL away from the dashed line. be done.

Further, in the radiation image reader 1, when the scanning region R1 of the excitation light EL and the detection region R2 of the signal light FL are in a centered positional relationship in the detection surface S, the width of the scanning region R1 is set to W1, Assuming that the width of the detection region R2 is W2 (>W1), the distance between the scanning region R1 and the detection region R2 is D, and the predetermined angle is θ, θ=tan ⁻¹ {(W2−W1)/2D} holds. do. According to this configuration, since the detection range of the signal light FL emitted from the surface IPa of the imaging plate IP is the same between the central portion and both end portions of the scanning line L, deterioration in reading accuracy of the radiographic image can be more reliably prevented. can be suppressed to

Further, in the radiation image reader 1, the optical filter 10 is formed on the glass plate 11, the first dielectric multilayer film 12 formed on the first surface 11a of the glass plate 11, and the second surface 11b of the glass plate 11. and a second dielectric multilayer film 13 . According to this configuration, the optical filter 10 having the functions described above can be obtained easily and reliably. For example, if the first dielectric multilayer film 12 and the second dielectric multilayer film 13 are as follows, the optical filter 10 will have the functions described above. That is, the first dielectric multilayer film 12 detects the signal light FL1 (FL) emitted from the surface IPa of the imaging plate IP at an angle larger than the predetermined angle θ with respect to the scanning line L in the detection plane S, and the detection Attenuate the excitation light EL reflected by the surface IPa of the imaging plate IP at an angle smaller than a predetermined angle θ with respect to the scanning line L in the plane S, and the second dielectric multilayer film 13 scans in the detection plane S. Any device may be used as long as it attenuates the excitation light EL reflected by the surface IPa of the imaging plate IP at an angle larger than the predetermined angle θ with respect to the line L. Thus, when it is difficult to obtain the optical filter 10 having the above-described functions with one type of dielectric multilayer film, two or more types of dielectric multilayer films can be combined to have the above-described functions. An optical filter 10 can be obtained. The functions of the first dielectric multilayer film 12 and the second dielectric multilayer film 13 are not limited to those described above. and the type of light attenuated by each of the second dielectric multilayer film 13 can be arbitrarily set. Since the glass plate 11 is made of colored glass that absorbs the excitation light EL, the light is reflected by the first dielectric multilayer film 12 and the second dielectric multilayer film 13 inside the optical filter 10 . The excited light EL is absorbed by the glass plate 11, and the entrance of the excited light EL to the photodetector 7 is more reliably suppressed. Also, the first dielectric multilayer film 12 and the second dielectric multilayer film 13 can be stably formed on the first surface 11a and the second surface 11b of the glass plate 11, respectively.

Further, in the radiation image reader 1, the excitation light EL reflected by the surface IPa of the imaging plate IP and the signal light FL emitted from the surface IPa of the imaging plate IP are converged only within a plane perpendicular to the detection surface S. A functional optical element 6 is arranged between the surface IPa of the imaging plate IP and the optical filter 10 . According to this configuration, as the photodetector 7, one including a plurality of photodiodes 71 arranged along the direction parallel to the scanning line L can be used.

In the radiographic image reader 1, the photodetector 7 controls a plurality of photodiodes 71 arranged in a direction parallel to the scanning line L as one channel. According to this configuration, a radiation image can be read with a simpler configuration.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

Although the plurality of photodiodes 71 are controlled as one channel in the photodetector 7 in the above embodiment, the plurality of photodiodes 71 may be controlled as a plurality of channels. By controlling the plurality of photodiodes 71 as a plurality of channels, noise can be reduced compared to the case where the plurality of photodiodes 71 are controlled as a single channel. Further, when a plurality of photodiodes 71 are controlled as a plurality of channels, even if the excitation light EL is not scanned along the scanning line L and the entire scanning region R1 is irradiated with the excitation light EL, imaging A radiation image recorded on the surface IPa of the plate IP can be read.

Further, in the above embodiment, the average transmittance of the “excitation light EL reflected by the surface IPa of the imaging plate IP” through the optical filter 10 is less than 50%, and the “scanning line L within the detection surface S The transmittance of the signal light FL emitted from the surface IPa of the imaging plate IP at an angle larger than a predetermined angle with respect to the vertical direction through the optical filter 10 is less than 50% on average, and the "detection The average transmittance of the signal light FL emitted from the surface IPa of the imaging plate IP through the optical filter 10 at an angle smaller than a predetermined angle with respect to the direction perpendicular to the scanning line L in the plane S is Although it was 50% or more, each transmittance value is not limited to these values. Transmittance (e.g., average transmittance) of "excitation light EL reflected by the surface IPa of the imaging plate IP" through the optical filter 10, and "in the detection plane S in the direction perpendicular to the scanning line L On the other hand, the transmittance (e.g., average transmittance) of the signal light FL emitted from the surface IPa of the imaging plate IP at an angle larger than the predetermined angle passes through the optical filter 10, respectively. Transmittance (for example, average transmittance), it is possible to both reduce the size of the device and maintain the reading accuracy of the radiographic image. However, since the excitation light EL is generally stronger in intensity than the signal light FL, the transmittance of the excitation light EL through the optical filter 10 is preferably less than 1% on average.

In the above embodiment, the optical element 6 has a cylindrical shape, but the optical element 6 converges the signal light FL emitted from the surface IPa of the imaging plate IP only within the plane perpendicular to the detection surface S. Any shape can be used as long as it has the function of Also, the optical element 6, the optical filter 10, and the photodetector 7 may be in contact with each other (see FIG. 6), or may be separated from each other.

Alternatively, both the first dielectric multilayer film 12 and the second dielectric multilayer film 13 may be formed on the second surface 11b of the glass plate 11, as shown in FIG. 10(a). Specifically, the first dielectric multilayer film 12 is formed on the second surface 11b of the glass plate 11, and the second dielectric multilayer film 13 is formed on the surface of the first dielectric multilayer film 12. may Alternatively, the second dielectric multilayer film 13 may be formed on the second surface 11b of the glass plate 11, and the first dielectric multilayer film 12 may be formed on the surface of the second dielectric multilayer film 13. .

Moreover, as shown in FIG. 10(b), the optical filter 10 may have a plurality of glass plates 11. FIG. In this case, a first dielectric multilayer film 12 is formed on the surface 11 a of one glass plate 11 and a second dielectric multilayer film 13 is formed on the surface 11 b of the other glass plate 11 . A plurality of glass plates 11 are connected to each other so as to be sandwiched between the first dielectric multilayer film 12 and the second dielectric multilayer film 13 . Alternatively, the first dielectric multilayer film 12 and the second dielectric multilayer film 13 may be connected to each other so as to be sandwiched between the glass plates 11, as shown in FIG. 10(c).

In the above-described embodiment, the optical filter 10 transmits the signal light FL emitted from the surface IPa of the imaging plate IP at a predetermined angle θ with respect to the direction perpendicular to the scanning line L in the detection surface S. However, the optical filter 10 may attenuate the signal light FL emitted from the surface IPa of the imaging plate IP at a predetermined angle θ with respect to the direction perpendicular to the scanning line L in the detection plane S.

Further, in the above embodiment, θ=tan ⁻¹ {(W2−W1)/2D} holds for the optical filter 10, but the optical filter 10 is reflected on the surface IPa of the imaging plate IP within the detection surface S. and the signal light FL1 (FL) emitted from the surface IPa of the imaging plate IP at an angle larger than a predetermined angle θ with respect to the direction perpendicular to the scanning line L. The size of the predetermined angle θ can be set as required. It should be noted that the smaller the predetermined angle θ is, the more the reduction in reading accuracy of the radiographic image is suppressed.

Further, regardless of whether or not the scanning region R1 of the excitation light EL and the detection region R2 of the signal light FL are in a center-aligned positional relationship in the detection plane S, the predetermined angle θ can be grasped as follows. can be done. Referring to FIG. 8, the predetermined angle .theta. can be regarded as an angle formed by a virtual line connecting the two with respect to the direction perpendicular to the scanning line. Alternatively, the predetermined angle .theta. It can be regarded as an angle formed by a connecting virtual line with respect to a direction perpendicular to the scanning line L. FIG. When the scanning region R1 of the excitation light EL and the detection region R2 of the signal light FL are not in a centered positional relationship, the predetermined angle θ differs between one side and the other side. In this case, it is preferable to adopt the smaller predetermined angle θ out of the predetermined angle θ on one side and the predetermined angle θ on the other side from the viewpoint of maintaining the reading accuracy of the radiographic image.

Further, in the above-described embodiment, in the photodetector 7, the plurality of photodiodes 71 are arranged one-dimensionally along the Y-axis direction. They may be arranged two-dimensionally.

DESCRIPTION OF SYMBOLS 1... Radiation image reader 5... Optical scanning part 10... Optical filter 11... Glass plate 11a... First surface 11b... Second surface 12... First dielectric multilayer film 13... Second dielectric Multilayer film 6 Optical element 7 Photodetector 71 Photodiode (photodetector) EL Excitation light FL Signal signal IP Imaging plate (recording medium) IPa Imaging plate surface L: scanning line, R1: scanning area, R2: detection area, S: detection surface, W1: width of scanning area, W2: width of detection area, D: distance between scanning area and detection area, θ: predetermined angle.

Claims (4)

an optical scanning unit that scans the surface of a recording medium on which a radiation image is recorded with excitation light along scanning lines positioned on the surface of the recording medium;
a photodetector that detects signal light emitted from the surface of the recording medium by scanning the excitation light in a detection plane that includes the scanning line and intersects the surface of the recording medium;
The photodetector is a multi-pixel photon counting device including a plurality of photodetectors arranged along a direction parallel to the scanning line,
The plurality of photodetector elements are controlled as one channel,
The radiation image reading device, wherein the electrical signals output from the plurality of photodetecting elements are combined and output from the photodetecting section. 2. The radiographic image reader according to claim 1, wherein the width of the detection area of the signal light in the photodetector is longer than the width of the scanning area of the excitation light on the surface of the recording medium in the detection plane. . placed on the optical path between the surface of the recording medium and the photodetector, and reflected by the surface of the recording medium in a plane that intersects the surface of the recording medium and is perpendicular to the detection surface; and converge the excitation light emitted from the surface of the recording medium and the signal light emitted from the surface of the recording medium, and in the detection plane, the excitation light reflected from the surface of the recording medium and the surface of the recording medium 3. The radiographic image reading apparatus according to claim 1, further comprising an optical element for causing the signal light emitted from the light detector to enter the light detection unit without converging the signal light. an optical filter placed on an optical path between the surface of the recording medium and the photodetector,
transmittance of the excitation light reflected by the surface of the recording medium through the optical filter, and forming an angle larger than a predetermined angle with respect to the direction perpendicular to the scanning line in the detection plane, Each transmittance of the signal light emitted from the surface of the recording medium passing through the optical filter forms an angle smaller than the predetermined angle with respect to the direction perpendicular to the scanning line in the detection plane. and the transmittance of the signal light emitted from the surface of the recording medium is smaller than the transmittance of the optical filter,
The predetermined angle is such that an imaginary line connecting one end of the excitation light scanning region on the surface of the recording medium and one end of the signal light detection region on the photodetector is perpendicular to the scanning line. 4. The radiographic image reading device according to claim 1, wherein the angle is formed by

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