Patent Application
20140126697
1. Field of the Invention
This disclosure is related to a radiation generating apparatus having a function of performing simulated display of a radiation-irradiated field with a visible-light-irradiated field, a radiation photographing system using the radiation generating apparatus, and a sighting projector unit to be used for forming the visible-light-irradiated field.
2. Description of the Related Art
A radiation generating apparatus typically includes a radiation generating unit having a radiation generating tube included therein and an adjustable diaphragm unit provided on a front surface of a release window of the radiation generating unit. The adjustable diaphragm unit has a function of adjusting a radiation field (the radiation-irradiated field), by shielding a portion of the radiation field. Specifically, a portion of radiation emitted via the release window of the radiation generating apparatus, which is not necessary for photographing, is blocked by the diaphragm unit so as to reduce exposure of a test body to the radiation. The adjustment of the radiation-irradiated field is achieved by adjusting the size of an aperture portion which is formed by the restriction blades and allows the radiation to pass through. The adjustable diaphragm unit is typically provided with a sighting projector unit configured to perform simulated display of the radiation-irradiated field with the visible-light-irradiated field to allow identification of the field to be irradiated with radiation by the naked eye before photographing.
In the related art, the adjustable diaphragm unit having a typical sighting projector unit is disclosed in Japanese Patent Laid-Open No. 7-148159. The sighting projector unit disclosed in Japanese Patent Laid-Open No. 7-148159 includes a reflector plate configured to allow radiation to pass therethrough and reflect visible light, restriction blades configured to restrict the radiation-irradiated field and the visible-light-irradiated field formed corresponding to the radiation-irradiated field, and a light source configured to emit visible light (a visible light source). The visible light source is arranged at a position deviated from the path of radiation to a field desired to be irradiated so as not to obstruct an optical radiation path when irradiating the field. The reflector plate is a flat mirror, and is arranged obliquely with respect to a center line connecting a focal point of the radiation and a center of the aperture portion of the restriction blades so as to reflect the visible light generated from the visible light source in this arrangement by a reflecting surface and form the visible-light-irradiated field to perform the simulated display of the radiation-irradiated field. The visible light source and the reflector plate are arranged together with the restriction blades within a housing having a radiation shielding property. The housing is formed of a material capable of reducing a radiation hitting the reflector plate or the restriction blades and scattering.
Radiation generated at a radiation generating spot (a focal point of the radiation) passes through the reflector plate and then forms a radiation-irradiated field narrowed to a required range of irradiation by the restriction blades of the adjustable diaphragm unit. The visible light emitted from the visible light source is reflected from the reflecting surface of the reflector plate, and then forms the visible-light-irradiated field narrowed to a required range of irradiation by the restriction blades. In order to enhance the accuracy of the simulated display with the visible-light-irradiated field so that the visible-light-irradiated field is allowed to match the radiation-irradiated field as accurately as possible, it is preferable that the distance from the visible light source to the reflecting surface of the reflector plate match the distance from the focal point of the radiation to the reflecting surface of the reflector plate.
The focal point of the radiation is located at a position in the radiation generating tube stored in the radiation generating unit, and hence there is a certain distance between the focal point and the reflector plate provided on the outside of the radiation generating unit. Therefore, when the distance from the visible light source to the reflecting surface of the reflector plate is allowed to match the distance from the focal point of the radiation to the reflecting surface of the reflector plate, the distance between the visible light source and the reflector plate is increased. Then, the size of the housing of the adjustable diaphragm unit that stores these members is increased, which may prevent reduction in the size of the radiation generating apparatus and of a radiation photographing system using the same. Since the material which constitutes the housing and is capable of diminishing the radiation is a material having a large mass, there arises a problem of increase in weight.
The present invention provides a radiation generating apparatus having a radiation generating unit and an adjustable diaphragm unit, and a radiation photographing system using the radiation generating apparatus, which achieve reduction in size and weight.
A first aspect of the invention is a radiation generating apparatus including a radiation generating unit having a focal point where a radiation is released; and a sighting projector unit including a reflector plate, a visible light source configured to irradiate the reflector plate with visible light, and a movable diaphragm configured to be capable of adjusting an opening size of an aperture portion by a plurality of restriction blades, the sighting projector unit being arranged forward of the focal point. The reflector plate is composed of a concave mirror configured to allow the radiation to pass therethrough and arranged at a position traversing a path of the radiation from the focal point to the aperture portion.
A second aspect of the invention is a radiation photographing system including the above-described radiation generating apparatus; a radiation detecting apparatus configured to detect a radiation released from the radiation generating unit and passed through a test body; and a control apparatus configured to control the radiation generating apparatus and the radiation detecting apparatus in coordination with each other.
A third aspect of the invention is a sighting projector unit including a reflector plate, a visible light source configured to irradiate the reflector plate with visible light, and a movable diaphragm configured to be capable of adjusting an opening size of an aperture portion by a plurality of restriction blades and arranged forward of the focal point. The reflector plate is composed of a concave mirror configured to allow the radiation to pass therethrough and arranged at a position traversing a path of the radiation from the focal point to the aperture portion. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Referring now to the drawings, embodiments of this disclosure will be described. However, this disclosure is not limited to the embodiments described below. As regards portions not specifically illustrated or not described in this specification, known or publicly known technologies of the corresponding technical fields are applied. In the drawings that are referred to below, the same reference numerals indicate the same components.
As illustrated in
The radiation generating unit 101 includes a storage container 120, a radiation generating tube 102, and a driving circuit portion 103. The storage container 120 stores the radiation generating tube 102 and the driving circuit portion 103 therein. A remaining space in the interior of the storage container 120 is filled with insulating liquid 109 serving as a medium for cooling the radiation generating tube 102 and the driving circuit portion 103.
The radiation generating tube 102 includes a cathode 111 serving as an electron source, a grid electrode 112, and a lens electrode 113 in a vacuum chamber 110. A target 115 configured to generate radiation by being irradiated with electrons is provided at a position opposing the cathode 111. The radiation generating tube 102 of the embodiment is a transmission-type radiation generating tube using a transmission-type target as the target 115, and the target 115 constitutes a transmission window for causing the radiation to go out of the radiation generating tube 102.
The target 115 includes a supporting substrate 116 and a target layer 117 stacked on the supporting substrate 116. The supporting substrate 116 is formed of a material having good transmissivity for the radiation. For example, a diamond substrate may be used as the supporting substrate 116. The target layer 117 is formed of a material which releases radiation by being irradiated with electrons. The target layer 117 may be formed as a layer of a metal having an atomic number 42 or higher, or as a layer containing the metal. The target 115 is installed with the target layer 117 facing the cathode 111. The target layer 117 is irradiated with electrons which are taken out from the cathode 111 by the grid electrode 112 and accelerated and are converged by the lens electrode 113, whereby the radiation is generated. The radiation generated at target layer 117 passes through the supporting substrate 116 and goes out of the radiation generating tube 102.
A radiation shielding member 118 is provided around the target 115 (transmission window) of the radiation generating tube 102 stored in the storage container 120 so as to project both outward and inward of the radiation generating tube 102. The radiation shielding member 118 is configured to shield unnecessary part of the radiation, and is preferably formed of a material having low radiation transmissivity such as lead or tungsten. The radiation shielding member 118 has a through hole penetrating through the inside-and-outside direction of the radiation generating tube 102. The target 115 is provided in the through hole of the radiation shielding member 118, and shields a midsection of the through hole. The through hole of the radiation shielding member 118 includes an electron incident hole 118a on one side (the inside of the radiation generating tube 102) and a radiation extraction hole 118b on the other side (the outside of the radiation generating tube 102) with respect to the target 115 provided at the midsection of the through hole. The electron incident hole 118a is a hole which allows the target 115 (the target layer 117) to be irradiated with the electrons passing therethrough and faces the cathode 111. The radiation extraction hole 118b is a hole which allows the radiation generated by irradiating the target 115 (the target layer 117) with the electrons to pass therethrough and go out therefrom, and faces the release window 121 of the storage container 120.
The driving circuit portion 103 is arranged inside the storage container 120 of the radiation generating unit 101. The driving circuit portion 103 generates a voltage and the voltage is applied to the cathode 111, the grid electrode 112, the lens electrode 113, and the target layer 117 provided in the radiation generating tube 102. Examples of the cathode 111 include a tungsten filament, a heat cathode such as an impregnated cathode, and a cold cathode such as a cathode made of carbon nanotubes. In the vacuum chamber 110, electrons are discharged in the direction of the target layer 117 as an anode by an electric field formed by the grid electrode 112. The electrons are converged by the lens electrode 113, and collide with the target layer 117 formed on the supporting substrate 116 by a film-forming technology or the like, and generate a radiation. Examples of the target layer 117 include tungsten, tantalum, and molybdenum layers. The generated radiation passes through the release window 121 with unnecessary part thereof being shielded by the radiation shielding member 118. The radiation then passes through the sighting projector unit 150.
The storage container 120 is filled with the insulating liquid 109 serving as a cooling medium for the radiation generating tube 102. The insulating liquid 109 is preferably insulating oil, and mineral oil, silicone oil, or the like. Examples of the other usable insulating liquid 109 include fluorinated insulating liquid.
The sighting projector unit 150 is connected to the release window 121 of the radiation generating unit 101, and in this embodiment, includes restriction blades 152 and a housing 151.
As illustrated in
The housing 151 is an outer frame that is connected to the radiation generating unit 101 and contains the restriction blades 152 and the sighting projector unit while shielding the scattering radiation. The housing 151 is formed of the same material as the housing used in the related art. In order to suppress scattering of the visible light emitted from the visible light source 2, the housing 151 is preferably blackened by coating, chemical treatment, or the like for reducing a reflectance on the inner surface of the container with respect to the visible light.
The sighting projector unit 150 is provided with the sighting projector unit. The sighting projector unit includes the visible light source 2 and the reflector plate 3, and is configured to perform display of visible light which simulates the radiation-irradiated field 6 at the time of irradiation of a radiation using the visible-light-irradiated field 5 by the visible light (see
The visible light source 2 irradiates the outside with the visible light emitted therefrom through the aperture portion 153 via the reflector plate 3. Therefore, the visible light source 2 is installed so as to face the reflecting surface of the reflector plate 3. Specifically, in this disclosure, a concave mirror is used as the reflector plate 3. Since the concave mirror has an advantage in converging and reflecting incident light, even though the distance from the visible light source 2 to the reflecting surface of the reflector plate 3 is reduced, the same state of reflecting light as in a case where the distance from the visible light source 2 to the reflecting surface of the reflector plate 3 is increased may be obtained. In order to enhance the accuracy of the simulated display with the sighting projector unit using the reflector plate composed of the flat mirror of the related art, the distance between the focal point of the radiation and the reflecting surface of the reflector plate and the distance between the visible light source and the reflecting surface of the reflecting plate need to be equalized or made as close as possible. In the sighting projector unit of this disclosure, since the concave mirror is used as the reflector plate 3, even when the position of the visible light source 2 is moved toward the reflecting surface, the state of the reflected light is the same as the state in the case where the visible light source 2 is moved away from the reflecting surface, and the accuracy of the simulated display may be maintained at a high level. When the concave mirror is used as the reflector plate 3, since light is converged, and hence the intensity of illumination of the visible-light-irradiated field is increased and a half shadow of the visible light source 2 is reduced, so that the boundary of the visible-light-irradiated field 5 may be further clarified.
The reflector plate 3 composed of the concave mirror of this disclosure is provided so as to traverse a path of the radiation between the release window 121 of the radiation generating unit 101 and the aperture portion 153 of the restriction blades 152 in the same manner as the reflecting plate composed of the flat mirror of the related art. As illustrated in
The reflector plate 3 illustrated in
A case will be described with reference to
In a case where the concave mirror having the two-dimensional curve as illustrated in
The reflector plate 3 is provided so as to be capable of reflecting the visible light from the visible light source 2 in the direction of the aperture portion 153 of the restriction blades 152 without any obstruction in an optical path of the reflected light with the visible light source 2. Specifically, the reflector plate 3 is provided obliquely with respect to a straight line (center line 162) connecting a focal point 7 of the radiation (see
For example, assuming that the angle formed between a normal line 160 at the center 161 of the concave mirror to be used as the reflector plate 3 and the center line 162 is 45 degrees, the size of the housing 151 in the vertical direction on the drawing may be reduced. In addition, since the visible light source 2 may be arranged closer to the reflector plate 3, if the angle formed between the normal line 160 at the center 161 of the concave mirror and the center line 162 is reduced, the visible light source 2 does not obstruct an optical path of the reflected light. Therefore, the angle formed between a normal line 160 at the center 161 of the concave mirror used as the reflector plate 3 and the center line 162 may be set to an angle smaller than 45 degrees, and further the size of the housing 151 in the lateral direction on the drawing may be reduced. In order to reduce the size of the housing 151, the angle formed between the normal line 160 at the center 161 of the concave mirror and the center line 162 is preferably set to an angle not larger than 40 degrees.
By setting the visible light source 2 and the focal point 7 to have an optically conjugated positional relationship, simulated-display of the radiation-irradiated field 6 formed by the focal point 7 on a detector, not illustrated, configured to detect a radiation and provided at a position opposing the sighting projector unit may be achieved with the visible-light-irradiated field 5 formed on the detector by the visible light source 2 with high reproducibility.
The reflector plate 3, which is a concave mirror, may be the one having a uniform thickness. However, the reflecting layer 10 formed of a material of metal or the like having a relatively high capability of diminishing the radiation may have a distribution in the film thickness. Specifically, an angle formed between a normal line at a certain position on the surface of the reflecting layer 10 and a radiation passing through the position of the normal line is defined as “a”, and an angle between a normal line at another position on the surface of the reflecting layer 10 and a radiation passing through this position of the normal line is defined as “b”. When a<b is established, it is preferable that the thickness of the portion of the reflecting layer 10, at the position where the angle “a” is formed, is larger than the thickness of the portion of the reflecting layer 10, at the position where the angle “b” is formed. That is, it is preferable that the portion of the reflecting layer 10 at angle “a” is large and the thickness of the portion of the angle “b” is small. In other words, it is preferable that the thickness of the reflecting layer 10 at a position where the angle formed between the normal line to the surface of the reflecting layer 10 and the direction of transmission of the radiation passing through the position of the normal line is relatively small be larger than the thickness of the reflecting layer 10 at a position where the angle is relatively large. In this configuration, the distance by which the radiation passes through the reflecting layer 10 may be close to uniform, so that unevenness in the quality of radiation passing through the reflector plate 3 may be reduced. When the radiation generating unit 101 is a transmission-type unit using the transmission-type radiation generating tube 102, the quality of the radiation emitted from the radiation generating unit 101 is relatively uniform. Therefore, this configuration is specifically effective for preventing deterioration in the uniformity of the radiation quality.
As illustrated in
Furthermore, the reflector plate may be varied in the thicknesses of the reflecting layer and the base layer as illustrated respectively in
An X-ray represents the radiation, and the radiation generating apparatus and the radiation photographing system of this disclosure may be used as an X-ray generating unit and an X-ray photographing system. The X-ray photographing system may be used in a non-destructive inspection for industrial products and used as medical equipment for supporting medical diagnosis of human bodies or animals.
A radiation generating apparatus as illustrated in
The size of the housing 151 of the sighting projector unit 150 was 50×50×30 mm, and a resin sheet containing tungsten powder was bonded to the inner surface of the housing 151 so as to prevent scattered radiation leaking therefrom. A visible light source 2 composed of 2 mm×2 mm white chip LED was provided inside of the housing 151. The normal line at the center of the reflector plate 3 of the concave mirror that reflects light from the visible light source 2 was inclined by 35° with respect to the center axis. The concave mirror used as the reflector plate 3 had a magnification of ×1.3 and a diameter of 30 mm. The visible light source 2 was assembled so that the area of the visible light from the visible light source 2 is restricted by the restriction blades 152 arranged inside of the housing 151, thereby forming the visible-light-irradiated field 5.
The thickness of the reflecting layer 10 of the concave mirror was configured to be large at a portion where the angle formed between the normal line to the reflecting layer 10 and the direction of transmission of the radiation which passes through the position of the normal line was small and the thickness thereof be small at a portion where the angle was large, so that the distance of passage of the radiation becomes uniform.
The adjustable diaphragm unit was mounted on the sighting projector unit 150 of the transmission-type radiation generating apparatus 200. When the operation of the radiation photographing system using the radiation generating apparatus 200 was observed, the visible-light-irradiated field 5 substantially same as the radiation-irradiated field 6 was displayed, and variations in the radiation quality were small, and an image having a good image quality was obtained.
With respect to the operation of the adjustable diaphragm unit, the intensity of illumination became brighter than that when using the flat mirror by the lens effect of the concave mirror used as the reflector plate 3, a half shadow of the visible light source 2 became small, and the boundary of the visible-light-irradiated field 5 became clear. When the entire weight of the sighting projector unit 150 was measured, it was about 200 g, and the weight was reduced as compared to the products of the related art.
A sighting projector unit of the related art will be described below as a comparative example. A visible light source in the related art was a tube having a diameter of approximately 20 mm, and had a minimum capacity when arranged with the normal line of the reflector plate composed of the flat mirror arranged obliquely with respect to the center line by 45°. The size of the housing was 200×200×150 mm, and the weight was approximately 2 kg.
When an image was taken by using a transmission-type radiation generating unit, unevenness occurs in radiation quality due to the obliquely arranged reflector plate composed of the flat mirror and an image with a gradation was obtained.
Example 2 will be described with reference to
A radiation generating apparatus provided with the sighting projector unit 150 illustrated in
The adjustable diaphragm unit was mounted on the sighting projector unit of the transmission-type radiation generating apparatus. When the operation of the radiation photographing system using the radiation generating apparatus was observed, simulated display of the radiation-irradiated field 6 using the visible-light-irradiated field 5 was achieved with good reproducibility.
With respect to the operation of the adjustable diaphragm unit, the intensity of illumination increases by the lens effect of the reflector plate 3 composed of the concave mirror, the half shadow of the visible light source 2 became small, and the boundary of the visible-light-irradiated field became clearer. When the radiation was released for a long time, deterioration of the resin-made portion of the white LED is less than that in Example 1, and normal illumination for a long time was achieved.
When the entire weight of the sighting projector unit 150 was measured, it was about 200 g, and the weight was reduced as compared to the products of the related art.
The radiation generating apparatus of this disclosure employs the concave mirror serving as the reflector plate. Therefore, the state of the reflected light same as the state in the case of the reflection of light from a visible light source located at a farther position may be obtained by the light converging effect. In other words, in the radiation generating apparatus of this disclosure, even when the distance between the reflecting surface of the reflector plate and the visible light source is set to be shorter than the distance between the reflecting surface of the reflector plate and the focal point of the radiation, the same state of the reflecting light as a case where these distances are matched is obtained. Therefore, even when the accuracy of the simulated display by the visible-light-irradiated field is increased, the size of the movable aperture unit provided with the adjustable diaphragm unit is reduced, so that reduction in size and weight of the entire apparatus may be achieved in association with reduction in size and weight of the housing of the sighting projector unit.
In the radiation photographing system of this disclosure, reduction in size and weight of the entire system may be realized by using the radiation generating apparatus reduced in size and weight.
Furthermore, by using the sighting projector unit of this disclosure, reduction in size and weight of the radiation generating apparatus and the radiation photographing system using the same are realized.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that those embodiments are not intended to be limiting. The scope of the following claims is to be accorded the broadest reasonable interpretation so as to encompass all modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2012-242634 filed in Nov. 2, 2012, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-242634 | Nov 2012 | JP | national |
