JP2004109807A - Radiographic information reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent infrared light emitted by a laser diode from being detected by a photodetector in a radiographic information reading apparatus which uses the laser diode as an excitation light source and a photodiode as the photodetector. <P>SOLUTION: In the radiographic information reading apparatus having an excitation light irradiating means of irradiating a portion of a stimulable phosphor sheet 13 where the radiographic information is stored and recorded with the excitation light 10a including red light and infrared light emitted by the laser diode 11a through an irradiation optical system, the light path surface 32a having the smallest variation in excitation light incidence angle by light passing positions in a light passage surface of an optical element 32 constituting the irradiation optical system is given a coating 33 which excellently transmits the red light and excellently reflects the infrared light. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention irradiates a stimulable phosphor sheet on which radiation image information is accumulated and recorded with excitation light, thereby photoelectrically reading the stimulated emission light emitted from the sheet and indicating the radiation image. In particular, a radiation image information reading apparatus using a laser diode (semiconductor laser) as an excitation light source and a photo detector as a photodetector for detecting stimulated emission light is used. It relates to the device.
[0002]
[Prior art]
Conventionally, a part of this radiation energy is accumulated when irradiated with radiation, and then, when irradiated with excitation light such as visible light or laser light, a stimulable phosphor (stimulated phosphor) that exhibits stimulated luminescence according to the accumulated radiation energy. Exhaustible phosphors) are known, and radiation image recording / reproducing systems using a stimulable phosphor sheet obtained by laminating this stimulable phosphor on a support have been widely put into practical use.
[0003]
This radiographic image recording / reproducing system accumulates and records radiographic image information of a subject on the stimulable phosphor sheet by irradiating the stimulable phosphor sheet with radiation that has passed through a subject such as a human body, and then a laser beam. The sheet is scanned two-dimensionally with excitation light such as to generate stimulated emission light from a portion irradiated with the excitation light, and the stimulated emission light is read by a photoelectric reading means to obtain an image signal indicating the radiographic image information. To get.
[0004]
The image signal obtained by this system is subjected to image processing such as gradation processing and frequency processing suitable for observation interpretation, and the radiological image carried by the system is reproduced and recorded on the film as a diagnostic visible image. Or used for display on a CRT image display device or the like.
[0005]
Here, in the radiographic image information reading apparatus used in the radiographic image recording / reproducing system described above, photoelectric reading means (photodetection) is used from the viewpoint of shortening the reading time of the photostimulated luminescence light, downsizing the apparatus, and reducing the cost. It has been proposed to apply a line sensor comprising a CCD as a device. Patent Document 1 shows an example of a radiation image information reading apparatus that obtains an image signal indicating radiation image information from a stimulable phosphor sheet in this manner.
[0006]
Such a radiological image information reader is basically
Excitation light irradiation means for irradiating a part of the stimulable phosphor sheet on which radiation image information is accumulated and recorded, with excitation light in a linear main scanning direction through an irradiation optical system,
A line sensor consisting of a CCD for detecting the stimulated emission light emitted from the portion of the stimulable phosphor sheet that has been irradiated with the excitation light;
Sub-scanning means for moving one of the light detector and the excitation light irradiation means and the stimulable phosphor sheet in a sub-scanning direction substantially perpendicular to the main scanning direction relative to the other. It will be.
[0007]
As described above, the excitation light irradiation means for linearly irradiating the stimulable phosphor sheet with excitation light may be one that emits so-called fan beam-like excitation light, or a thin one. The beam may be deflected so as to be scanned linearly on the stimulable phosphor sheet.
[0008]
By the way, it is considered that a laser diode (semiconductor laser) is applied as an excitation light source that emits the above-described excitation light from the viewpoint of downsizing of the apparatus and cost reduction. Patent Documents 2 and 3 show examples of the radiation image information reading apparatus configured as described above.
[0009]
However, when the laser diode is used as the excitation light source and the above-described CCD is used as the photodetector, there is a problem that the excitation light component is detected as noise by the photodetector. That is, as the laser diode, one that emits red light suitable for excitation of the stimulable phosphor sheet is usually used, but a laser diode whose oscillation wavelength is in the red region generally emits infrared light in addition to red light. . A CCD composed of a photodiode mainly composed of silicon has high sensitivity not only to visible light but also to infrared light, so that infrared light emitted from a laser diode is reflected by a storage phosphor sheet. It will be detected by this photodetector.
[0010]
In many cases, an excitation light cut filter that transmits the stimulated emission light and cuts the excitation light is disposed on the front side of the photodetector, but infrared light passes through such an excitation light cut filter. Resulting in.
[0011]
Therefore, conventionally, as also shown in Patent Document 2, the excitation light emitted from the laser light source is used as an optical filter that blocks light having a wavelength other than the oscillation wavelength desired for excitation of the storage phosphor. It has been proposed to irradiate the stimulable phosphor sheet after passing through.
[0012]
[Patent Document 1]
Japanese Patent Laid-Open No. 1-1101540
[Patent Document 2]
JP 60-135929 A
[Patent Document 3]
Japanese Patent Laid-Open No. 2002-77528
[Problems to be solved by the invention]
However, it is extremely difficult to sufficiently block the infrared light emitted from the above-described laser diode by the optical filter as shown in Patent Document 2 above. Further, when the optical filter as described above is provided in addition to the excitation light irradiation optical system, there is a problem that the structure of the optical system becomes complicated.
[0016]
The present invention has been made in view of the above circumstances, and even if a laser diode is used as an excitation light source and a photodiode is used as a photodetector, infrared light emitted from the laser diode is light. It is an object of the present invention to provide a radiographic image information reading apparatus that is not detected by a detector and that can avoid complication of an excitation light irradiation optical system.
[0017]
[Means for Solving the Problems]
The radiological image information reading apparatus according to the present invention, as described above,
Excitation light that irradiates excitation light containing red light and infrared light emitted from a laser diode on a part of the stimulable phosphor sheet on which radiation image information is stored and recorded in the linear main scanning direction through the irradiation optical system Irradiation means;
A photo detector such as a CCD line sensor made of a photodiode, which detects the stimulated emission light emitted from the portion of the stimulable phosphor sheet that has been irradiated with the excitation light;
Sub-scanning means for moving one of the light detector and the excitation light irradiation means and the stimulable phosphor sheet in a sub-scanning direction substantially perpendicular to the main scanning direction relative to the other. In the radiographic image information reading device,
Among the light passing surfaces of the optical elements constituting the irradiation optical system, the red light is transmitted well to the light passing surface with the smallest change in the excitation light incident angle for each light passing position, while the infrared light is It is characterized by a coating that reflects well.
[0018]
In addition, as the above-mentioned irradiation optical system, when an excitation light emitted in a divergent light state from a laser diode is collected in one direction and used to irradiate a stimulable phosphor sheet in the form of a fan beam, It is desirable to use a curved surface that is concave toward the incident side of the excitation light as the light passage surface on which the coating is applied.
[0019]
On the other hand, the irradiation optical system includes a collimator lens that collimates excitation light emitted in a divergent light state from a laser diode and an optical deflector that deflects the excitation light that has become parallel light. Even in this case, it is desirable to use a curved surface that is concave toward the incident side of the excitation light as the light passage surface on which the coating is applied.
[0020]
The light passing surface having the curved surface as described above is particularly preferably a curved surface that is concave toward the incident side of the excitation light in one direction and a cylindrical surface that is a flat surface in the other direction.
[0021]
【The invention's effect】
The coating applied to the light passage surface of the optical element to reflect infrared light can generally block infrared light better than an optical filter that absorbs and blocks infrared light. Yes. Therefore, in the radiological image information reading apparatus of the present invention to which such a coating is applied, a laser diode is used as an excitation light source, and even though a photo detector is used as a photodetector, the laser diode emits light. It is possible to reliably prevent infrared light from being detected by the photodetector.
[0022]
In the radiological image information reading apparatus of the present invention, since the coating is applied to the light passage surface of the optical element constituting the originally required excitation light irradiation optical system, the infrared light is newly blocked in the irradiation optical system. Unlike the case of adding an optical filter for the above, the structure of the irradiation optical system is not complicated.
[0023]
The above-mentioned coating is usually composed of a multilayer coating, and the reflectance of infrared light incident thereon varies depending on the incident angle. In view of this point, in the radiological image information reading apparatus according to the present invention, the coating is applied to the light passage surface where the change in the excitation light incident angle for each light passage position is the smallest. It is possible to prevent a significant decrease in the light reflectance and to obtain a good infrared light blocking effect.
[0024]
In addition, when the irradiation optical system is one that collects excitation light emitted in a divergent light state from a laser diode in one direction and irradiates the stimulable phosphor sheet in the form of a fan beam, When a curved surface that is concave toward the incident side of the excitation light is used as the light passage surface to be coated, each component of the fan beam-like excitation light is close to normal incidence on this light passage surface. Can be made incident. If it is so, it can prevent more reliably that the reflectance of infrared light falls by the light passage position in this light passage surface.
[0025]
The irradiation optical system includes a collimator lens that collimates excitation light emitted in a divergent light state from a laser diode, and an optical deflector that deflects the excitation light that has become parallel light. In this case, if a curved surface that is concave toward the incident side of the excitation light is used as the light passage surface on which the coating is applied, the deflected excitation light is applied to the light passage surface for each deflection position. It becomes possible to make it enter in the state near perpendicular incidence. Thereby, also in this case, it is possible to more reliably prevent the reflectance of the infrared light from being lowered due to the light passage position on the light passage surface.
[0026]
On the other hand, on the light passage surface having the curved surface as described above, the reflection component of red light returns to the light emitting point of the laser diode, causing a problem that the operation of the laser diode becomes unstable. In order to solve this problem, a cylindrical surface that is a concave surface toward the incident side of the excitation light in one direction and a flat surface in the other direction, in particular, as the light passage surface having the curved surface as described above. It is preferable to apply. In this case, a part of the excitation light reflected by the cylindrical surface is perpendicularly incident on the cylindrical surface in the plane including the one direction and is folded on the same optical path as it is, but in the plane including the other direction. Since it almost folds back at an angle with respect to the incident optical path, the reflected excitation light does not enter the laser diode as return light. Thereby, it becomes possible to prevent the operation of the laser diode from becoming unstable due to the return light.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0028]
FIG. 1 shows a schematic configuration of a radiographic image information reading apparatus according to an embodiment of the present invention. FIGS. 2 and 3 are side views of a reading optical system portion of the radiographic image information reading apparatus, respectively. The front shape is shown.
[0029]
As shown in FIG. 1, this apparatus includes a laser diode array 11 that emits fan beam-shaped excitation light 10, a lens array 12 that collects the excitation light 10 only in the plane shown in FIG. A lens array 15 that collects the stimulated emission light 14 emitted from the portion of the stimulable phosphor sheet 13 that has been irradiated linearly and the optical path of the stimulated emission light 14 that has passed through the lens array 15 are arranged. The excitation light cut filter 16, the CCD line sensor 17 that detects the stimulated emission light 14 that has passed through the excitation light cut filter 16, and the stimulable phosphor sheet 13 are irradiated with excitation light in the arrow Y direction, that is, on the sheet 13. And an endless belt 18 as sub-scanning means for feeding at a constant speed in a direction orthogonal to the length direction of the portion (arrow X direction).
[0030]
Further, an amplifier 20 that amplifies the analog photodetection signal S output from the CCD line sensor 17, an A / D converter 21 that digitizes the amplified photodetection signal S, and the A / D converter 21. Is provided with an image processing device 22 that performs image processing on the digital image signal D output from the image processing device 23 and an image reproduction device 23 that receives the digital image signal D after image processing.
[0031]
As shown in FIG. 3, the laser diode array 11 has a plurality of laser diodes 11a, 11b, 11c,... Having an oscillation wavelength of 660 nm arranged in a line as an example. The divergent excitation light 10a, 10b, 10c,... Emitted from the laser diodes 11a, 11b, 11c,... ... Is condensed in only one direction to form a fan beam, and the excitation light 10 formed by connecting the fan beams irradiates a part of the stimulable phosphor sheet 13 linearly. The combination lenses 12a, 12b, 12c,... Will be described in detail later.
[0032]
The CCD line sensor 17 has a large number of sensor chips (photoelectric conversion elements) 17a arranged in a line as shown in FIG. In this example, the light receiving width of the CCD line sensor 17 in the direction perpendicular to the direction in which the sensor chips are arranged, that is, the width W of the sensor chip 17a is about 100 μm.
[0033]
In the CCD line sensor 17, the sensor chips 17a are arranged in a direction along the length direction (arrow X direction) of the excitation light irradiation portion on the stimulable phosphor sheet 13 of FIG. The CCD line sensor 17 may be constituted by connecting a plurality of line sensors in the length direction in order to correspond to the wide storage phosphor sheet 13.
[0034]
On the other hand, the lens array 15 includes, for example, a large number of gradient index lenses 15a, 15b, 15c, 15d,. It will be. Each gradient index lens 15a, 15b, 15c, 15d,... Condenses the photostimulated light 14 emitted from the stimulable phosphor sheet 13, and guides it to the CCD line sensor 17 as shown in FIG. . This lens array 15 is arranged in such a direction that the gradient index lenses 15a, 15b, 15c, 15d,... Are aligned along the length direction (arrow X direction) of the excitation light irradiation portion on the stimulable phosphor sheet 13. Has been.
[0035]
The operation of the radiological image information reading apparatus having the above configuration will be described below. The storable phosphor sheet 13 stores and records radiographic image information of the subject, for example, by irradiating the radiation that has passed through the subject, and the sheet 13 is sent by the endless belt 18 at a constant speed in the arrow Y direction. At the same time, excitation light 10 emitted from the laser diode array 11 is irradiated linearly onto a part of the stimulable phosphor sheet 13.
[0036]
From the portion of the stimulable phosphor sheet 13 that has been irradiated with the excitation light 10, the stimulated emission light 14 having a light amount corresponding to the radiation image information that has been stored and recorded diverges. For example, the blue stimulated emission light 14 is condensed by the lens array 15 and guided to the CCD line sensor 17, and is detected photoelectrically by the CCD line sensor 17. The excitation light 10 reflected by the stimulable phosphor sheet 13 and traveling toward the CCD line sensor 17 is cut by the excitation light cut filter 16.
[0037]
The CCD line sensor 17 outputs an analog light detection signal S corresponding to the light amount of the stimulated emission light 14 (that is, indicating the radiation image information). The light detection signal S is amplified by the amplifier 20 and then converted into a digital image signal D by the A / D converter 21.
[0038]
This digital image signal D is next subjected to image processing such as gradation processing in the image processing device 22 and then sent to the image reproduction device 23 to reproduce the radiation image recorded on the stimulable phosphor sheet 13. Provided. The image reproducing device 23 may be a display means such as a CRT display device or a recording device that performs optical scanning recording on a photosensitive film.
[0039]
Next, the convergence states and wavelengths of the excitation light 10a, 10b, 10c,... Will be described in detail with reference to FIG. In this embodiment, the laser diodes 11a, 11b, 11c,... Constituting the laser diode array 11 each have an output of 50 mW, and 24 of them are used as an example. If a number of laser diodes 11a, 11b, 11c,... Are used in this way, the stimulable phosphor sheet 13 is linearly irradiated with the excitation light 10a, 10b, 10c,. As long as the main scanning width is the same, naturally the distance from the laser diode to the stimulable phosphor sheet 13 can be made shorter in this embodiment than in the case of using only one laser diode. Thereby, the radiation image information reading apparatus can be sufficiently downsized.
[0040]
In the present embodiment, the combination lenses 12a, 12b, 12c,... Are provided corresponding to the plurality of laser diodes 11a, 11b, 11c,. A lens array 12 is configured by being connected in the direction.
[0041]
Hereinafter, the combination lenses 12a, 12b, 12c... Will be described in detail. In the following, one of the combination lenses 12a will be described. However, the shapes and installation states of the other combination lenses 12b, 12c,. As shown in FIG. 6, the combination lens 12a is formed by integrating a beam splitter 31 disposed on the laser diode 11a side and a toric lens 32 disposed on the stimulable phosphor sheet 13 side. .
[0042]
The beam splitter 30 is formed in the shape of a rectangular parallelepiped block using optical glass. When the laser diode 11a is driven by an APC (Automatic Power Control), its output is monitored by an excitation light 10a. Is arranged to be branched partially.
[0043]
On the other hand, the toric lens 32 has a plane including the optical axis direction and the main scanning direction (arrow X direction), that is, the shape in the plane shown in FIG. 6, each component of the fan beam-like excitation light 10a is close to normal incidence. The incident end face 32a is a cylindrical surface that is curved so as to be incident in a state, and the exit end face 32b is a toric surface. The excitation light 10a is condensed only in the sub-scanning direction, and the storage fluorescence is accumulated. It converges linearly on the body sheet 13. At that time, the curvature of field is corrected by the action of the exit end face 32b which is a toric surface, and the beam diameter of the excitation light 10a on the stimulable phosphor sheet 13 is made constant regardless of the position in the main scanning direction.
[0044]
Here, the excitation light 10a has a wavelength of 650 to 670 nm which is effective for exciting the stimulable phosphor of the stimulable phosphor sheet 13 in the same manner as light emitted from a general laser diode whose oscillation wavelength is in the red region. In addition to red light, infrared light of 750 to 1050 nm in a longer wavelength region is included. Therefore, the incident end face 32a of the toric lens 32 is provided with a multilayer coating 33 that allows the red light having the above wavelength to be transmitted satisfactorily while reflecting the infrared light satisfactorily. FIG. 7 shows the spectral transmittance characteristics of the multilayer coating 33. The action of the multilayer coating 33 having such characteristics prevents the infrared light from reaching the stimulable phosphor sheet 13 and being reflected there and being detected as noise by the CCD line sensor 17.
[0045]
In addition, the reflectance of the infrared light in the above-mentioned multilayer coating 33 varies according to the incident angle. However, in the present embodiment, the multilayer coating 33 is formed on the incident end face 32a of the toric lens 32 having the cylindrical surface as described above, and therefore the infrared light is incident on the incident end face with respect to the multilayer coating 33. Nearly normal incidence occurs at any position on 32a. Therefore, the reflectance of infrared light is not greatly reduced by the light incident position on the incident end face 32a, and a good infrared light blocking effect is obtained.
[0046]
Further, since the incident end face 32a of the toric lens 32 is shaped as described above, a part of the excitation light 10a reflected by the incident end face 32a is reflected by the incident end face 32a in the plane shown in FIG. However, the reflected excitation light 10a is folded back almost at an angle with respect to the incident optical path in the plane perpendicular to FIG. 6 (in the plane including the sub-scanning direction). Does not enter the laser diode 11a as return light. Thereby, it is possible to prevent the operation of the laser diode 11a from becoming unstable due to the return light.
[0047]
In the embodiment described above, the excitation light 10a, 10b, 10c,... Emitted from the laser diodes 11a, 11b, 11c,. However, in order to irradiate the stimulable phosphor sheet linearly with the excitation light, the collimator lens 41 emits the excitation light 50 emitted in a divergent light state from one laser diode 40 as shown in FIG. Then, the collimated light is deflected by, for example, a light deflector 42 such as a galvanometer mirror, and the stimulable phosphor sheet 13 may be irradiated with the deflected excitation light 50.
[0048]
Even when such a configuration is employed, infrared light can be accumulated by forming a multilayer coating 33 similar to that described above on the incident end surface 42a of the toric lens 42 used as the excitation light irradiation optical system. It can be prevented that the body sheet 13 is reached and reflected there and detected as noise by the photodetector.
[0049]
In the embodiment described above, the stimulable phosphor sheet 13 is conveyed at a constant speed by the endless belt 18 for the excitation light sub-scanning, but the means for sub-scanning the excitation light is not limited to this. Alternatively, for example, a roller that transports the stimulable phosphor sheet 13 with a roller, or a device that relatively moves the excitation light irradiation means and the line sensor with respect to the fixed stimulable phosphor sheet 13 may be applied. Is possible.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a radiation image information reading device according to an embodiment of the present invention. FIG. 2 is a side view showing a reading optical system of the radiation image information reading device shown in FIG. FIG. 4 is a plan view of a line sensor used in the radiation image information reading apparatus. FIG. 5 is a front view (1) of a lens array used in the radiation image information reading apparatus. , Side view (2)
FIG. 6 is a plan view of excitation light irradiation means used in the radiation image information reading apparatus. FIG. 7 is a graph showing spectral reflectance characteristics of a coating formed in the excitation light irradiation optical system of the radiation image information reading apparatus. FIG. 8 is a plan view showing another excitation light irradiation means used in the radiation image information reading apparatus of the present invention.
10a, 10b, 10c Excitation light 11 Laser diode array 11a, 11b, 11c Laser diode 12 Lens array 12a, 12b, 12c Combination lens 13 Stimulating phosphor sheet 14 Stimulated light 15 Lens array 15a, 15b, 15c Refractive index distribution Type lens 16 Excitation light cut filter 17 CCD line sensor 17a CCD line sensor sensor chip 18 Endless belt 20 Amplifier 21 A / D converter 22 Image processing device 23 Image reproducing device 32, 42 Toric lens 32a, 42a Incident end face of toric lens 33 Multilayer coating 40 Laser diode 41 Collimator lens 42 Optical deflector

Claims (4)

Excitation light that irradiates excitation light containing red light and infrared light emitted from a laser diode on a part of the stimulable phosphor sheet on which radiation image information is stored and recorded in the linear main scanning direction through the irradiation optical system Irradiation means;
A photo-detector composed of a photodiode for detecting the stimulated emission light emitted from the portion of the stimulable phosphor sheet that has been irradiated with the excitation light;
Sub-scanning means for moving one of the light detector and the excitation light irradiation means and the stimulable phosphor sheet in a sub-scanning direction substantially perpendicular to the main scanning direction relative to the other. In the radiographic image information reading device,
Among the light passing surfaces of the optical elements constituting the irradiation optical system, the red light is transmitted well to the light passing surface with the smallest change in the excitation light incident angle for each light passing position, while the infrared light is A radiation image information reading apparatus, characterized in that a coating that reflects well is applied. The irradiation optical system collects excitation light emitted in a divergent light state from a laser diode in one direction and irradiates the stimulable phosphor sheet in the form of a fan beam,
The radiation image information reading apparatus according to claim 1, wherein the light passing surface provided with the coating is a curved surface that is concave toward the incident side of the excitation light. The irradiation optical system comprises a collimator lens that collimates the excitation light emitted in a divergent light state from a laser diode, and an optical deflector that deflects the excitation light that has become parallel light,
The radiation image information reading apparatus according to claim 1, wherein the light passing surface provided with the coating is a curved surface that is concave toward the incident side of the excitation light. 4. The light passing surface to which the coating is applied is a curved surface that is concave toward the incident side of the excitation light in one direction and a cylindrical surface that is a plane in the other direction. The radiation image information reading device described.

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