WO2012101883A1

WO2012101883A1 - Radiation image acquisition device

Info

Publication number: WO2012101883A1
Application number: PCT/JP2011/074334
Authority: WO
Inventors: 須山　敏康; 元胤杉山
Original assignee: 浜松ホトニクス株式会社
Priority date: 2011-01-25
Filing date: 2011-10-21
Publication date: 2012-08-02
Also published as: JP2012154736A

Abstract

This radiation image acquisition device (1) is provided with a radiation source (2) for emitting radiation, a tabular frequency conversion plate (3) for generating scintillation light (L₁, L₂) in response to incidence of radiation emitted from the radiation source (2) and transmitted through an object (A), mirrors (6a, 6b) for guiding scintillation light (L₁) emitted from a surface (3a) on the radiation-incident side of the wavelength conversion plate (3), mirrors (7a, 7b) for guiding scintillation light (L₂) emitted from surface (3b) of the wavelength conversion plate (3) opposite of the incident surface (3a), a light detector (4) for imaging the scintillation light (L₁, L₂) guided by the mirrors (6a, 6b, 7a, 7b), and a mirror (8) for guiding towards the light detector (4) the scintillation light (L₁, L₂) which has been guided by the mirrors (6a, 6b, 7a, 7b).

Description

Radiation image acquisition device

The present invention relates to a radiological image acquisition apparatus that acquires a radiographic image of an object by irradiating radiation.

Conventionally, with regard to X-ray image detection technology, a direct conversion method that directly detects radiation incident on a detector with the detector, and a radiation that is converted into light using a scintillator and then detected with the detector An indirect conversion method is known. As an apparatus employing such an indirect conversion method, radiation obtained by laminating a planar scintillator between two solid-state photodetectors in order to increase the detection efficiency of visible light converted by the scintillator. A detector has been devised (see Patent Document 1 below).

JP-A-7-27866

However, in the conventional configuration as described above, since the two detectors are positioned in the radiation incident direction, the detectors are easily exposed, and noise is generated due to the direct conversion signal of the radiation inside the detector. There is. Further, there is a tendency that noise is generated due to the shadow of the detector reflected in the radiation detection image. In addition, since radiation is attenuated by the detector, there is a problem that it is difficult to obtain a radiation detection image of a low energy component.

Therefore, the present invention has been made in view of such problems, and an object of the present invention is to provide a radiation image acquisition apparatus that can acquire a radiation detection image with reduced noise over a wide energy band.

In order to solve the above-described problem, a radiological image acquisition apparatus according to one aspect of the present invention generates a scintillation light in response to an incident of radiation emitted from the radiation source and transmitted through the object. A flat plate-shaped wavelength conversion member, a first optical member that guides scintillation light emitted from the radiation incident surface of the wavelength conversion member, and a surface opposite to the incident surface of the wavelength conversion member A second optical member that guides the scintillation light emitted from the image sensor, an image sensor that images each of the scintillation lights guided by the first and second optical members, and the first and second optical members. A common optical member that guides each of the guided scintillation lights toward the image sensor.

According to such a radiation image acquisition device, the radiation that has passed through the object is converted into scintillation light by the wavelength conversion member, and the scintillation light emitted from the radiation incident surface side and the opposite surface of the wavelength conversion member. Is detected by the image sensor, and can be detected as an image signal. At this time, since the scintillation light radiated from both surfaces of the wavelength conversion member is respectively guided from the first optical member and the second optical member to the imaging device via the common optical member, the radiation emission region It is possible to move the image sensor away from. As a result, generation of noise in the radiation detection image detected by the image sensor can be reduced, and a high-contrast detection image can be acquired over a wide energy component.

According to the present invention, it is possible to acquire a radiation detection image with reduced noise over a wide energy band.

It is a schematic block diagram of the radiographic image acquisition apparatus which concerns on suitable one Embodiment of this invention. It is a schematic block diagram of the radiographic image acquisition apparatus which concerns on the modification of this invention. It is a figure which shows the image of the radiation detection image detected by the radiographic image acquisition apparatus of FIG. It is a schematic block diagram of the radiographic image acquisition apparatus which concerns on the modification of this invention. It is a schematic block diagram of the radiographic image acquisition apparatus which concerns on the modification of this invention. It is a schematic block diagram of the radiographic image acquisition apparatus which concerns on the modification of this invention.

Hereinafter, preferred embodiments of a radiological image acquisition apparatus according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Each drawing is made for the purpose of explanation, and is drawn so as to particularly emphasize the target portion of the explanation. Therefore, the dimensional ratio of each member in the drawings does not necessarily match the actual one.

FIG. 1 is a schematic configuration diagram of a radiological image acquisition apparatus 1 according to a preferred embodiment of the present invention. As shown in the figure, a radiation image acquisition apparatus 1 is emitted from a radiation source 2 that emits radiation such as X-rays toward an object A such as an electronic component such as a semiconductor device or a food product, and the radiation source 2. A wavelength conversion plate (wavelength conversion member) 3 for converting the radiation transmitted through the object A into light, a photodetector (imaging device) 4 for imaging the light converted by the wavelength conversion plate 3, and the wavelength conversion plate 3 And an optical system 5 that guides the light converted by the light toward the photodetector 4. The photodetector 4 is an indirect conversion type detector such as a CMOS sensor or a CCD sensor that detects light converted based on incident radiation and generates an image signal.

The wavelength conversion plate 3 is a plate-like member disposed so as to be substantially perpendicular to the radiation emission direction of the radiation source 2, and generates scintillation light according to the incidence of radiation transmitted through the object A. Examples of such wavelength conversion plate 3 include Gd ₂ O ₂ S: Tb, Gd ₂ O ₂ S: Pr, CsI: Tl, CdWO ₄ , CaWO ₄ , Gd ₂ SiO ₅ : Ce, Lu _0.4 Gd _1.6 SiO ₅ , Examples include scintillators such as Bi ₄ Ge ₃ O ₁₂ , Lu ₂ SiO ₅ : Ce, Y ₂ SiO ₅ , YAlO ₃ : Ce, Y ₂ O ₂ S: Tb, YTaO ₄ : Tm, etc. It is set to an appropriate value depending on the energy band of the radiation detected within a range of several mm. That is, the wavelength conversion plate 3 emits scintillation light from both the incident surface 3a of the radiation and the surface 3b opposite to the incident surface 3a in response to the incidence of the radiation transmitted through the object A. Scintillation light L ₁ emitted from the incident surface 3a becomes those converted from predominantly low-energy components of the incident radiation. On the other hand, scintillation light L ₂ emitted from the surface 3b is becomes converted from mainly the high energy component of the radiation incident. This is because radiation in the low energy band is easily converted into scintillation light on the incident surface 3a side inside the wavelength conversion plate 3, whereas radiation in the high energy band is transmitted through the wavelength conversion plate 3 and wavelength conversion plate. This is because it is easily converted into scintillation light near the inner surface 3b of 3.

The optical system 5 includes five

mirrors

6 a, 6 b, 7 a, 7 b, and 8 as optical members that control the optical path of scintillation light emitted from the wavelength conversion plate 3, and a rotation drive mechanism 9 that rotates the mirror 8. Has been. The

mirrors

6 a and 6 b in the optical system 5 are arranged on the incident surface 3 a side of the wavelength conversion plate 3, and the scintillation light L ₁ emitted from the incident surface 3 a is separated from the radiation irradiation direction of the radiation source 2. Light is guided toward the position. Specifically, it mirrors 6a, 6b, respectively, between the incident surface 3a and the radiation source 2, and is disposed at a position apart from the mirror 6a along the incident surface 3a, the scintillation light L _1, the wavelength conversion The light is sequentially reflected from the plate 3 toward the mirror 8 disposed at a position separated along the extending direction of the incident surface 3a. The

mirrors

7 a and 7 b in the optical system 5 are arranged on the surface 3 b side opposite to the incident surface 3 a of the wavelength conversion plate 3, and the scintillation light L ₂ emitted from the surface 3 b is used as the radiation of the radiation source 2. The light is guided toward the position separated from the irradiation direction. Specifically, it mirrors 7a, 7b, respectively, a position away from the surface 3b in the irradiation direction of the radiation source 2, and is disposed at a position apart from the mirror 7a along the surface 3b, the scintillation light L ₂ Then, the light is sequentially reflected toward the mirror 8 disposed at a position away from the wavelength conversion plate 3 along the extending direction of the surface 3b.

The mirror 8 of the optical system 5 is substantially parallel to a plane including the optical paths of the scintillation lights L ₁ and L ₂ at a position away from the wavelength conversion plate 3 along the extending direction of the incident surface 3a. It is arranged to become. The mirror 8 is supported by a rotation drive mechanism 9 incorporating a motor so as to be rotatable about an axis substantially perpendicular to a plane including the optical paths of the scintillation lights L ₁ and L ₂ . By the mirror 8 supported by such a rotational drive mechanism 9, the scintillation lights L ₁ and L ₂ are selected toward the photodetector 4 arranged further away from the mirror 8 along the extending direction of the incident surface 3a. Light is guided. That, is reflected toward the imaging lens 4a of the rotating mirror 8 so as to direct a reflecting surface 8a mirror 6b side (solid line in FIG. 1), scintillation light L ₁ is the optical detector 4 by a rotational driving mechanism 9 . On the other hand, to rotate the mirror 8 so as to direct a reflecting surface 8a mirror 7b side by a rotational driving mechanism 9 (the two-dot chain line in FIG. 1), the scintillation light L ₂ toward the image pickup lens 4a of the optical detector 4 And reflected.

Further, the radiological image acquisition apparatus 1 controls the rotation control unit 11 that controls the rotation of the rotation drive mechanism 9, the timing of selection of the scintillation light L ₁ and L ₂ by the mirror 8, and the timing of imaging of the photodetector 4. And a timing control unit 12 for processing the image signal output from the photodetector 4.

Specifically, the rotation control unit 11 controls the rotation angle of the mirror 8 by sending a control signal to the rotation drive mechanism 9 in response to an instruction signal from the timing control unit 12. The timing control unit 12 sends an instruction signal to the rotation control unit 11 to switch the rotation angle of the mirror 8 so that the scintillation light L ₁ is reflected by the photodetector 4, and at the same time, The instruction signal is transmitted so as to capture the scintillation light L ₁ in synchronization with the switching of 8. Further, the timing controller 12 sends an instruction signal to the rotation controller 11 to switch the rotation angle of the mirror 8 so that the scintillation light L ₂ is reflected by the photodetector 4, and at the same time, to the photodetector 4. , in synchronization with the switching of the mirror 8 transmits an instruction signal to image scintillation light L _2. The image processing device 13 acquires two image signals obtained as a result of imaging the scintillation lights L ₁ and L ₂ from the light detector 4, and processes the two image signals to transmit radiation regarding the object A. Image data is generated.

According to the radiographic image acquisition apparatus 1 described above, the radiation transmitted through the object A is converted into scintillation light L ₁ and L ₂ by the wavelength conversion plate 3, and the radiation incident surface 3 a side of the wavelength conversion plate 3 and its side The scintillation lights L ₁ and L ₂ radiated from the opposite surface 3b are detected by the photodetector 4, thereby enabling detection as image signals. At this time, since the scintillation lights L ₁ and L ₂ radiated from both surfaces of the wavelength conversion plate 3 are guided to the photodetector 4 from the

mirrors

6a and 6b and the

mirrors

7a and 7b via the mirror 8, respectively. The photodetector 4 can be separated from the radiation emission region. Thereby, the shadow of the detector is not reflected in the radiation projection image of the object A, and the attenuation of the low energy component of the radiation by the detector is also eliminated. In addition, there is little occurrence of direct conversion noise due to radiation incident on the detector itself. Further, by detecting scintillation light from both surfaces of the wavelength conversion plate 3, a low-energy component radiation transmission image and a high-energy component radiation transmission image can be acquired. As a result, generation of noise in the radiation detection image can be reduced, and a high-contrast detection image can be acquired over a wide energy component.

In addition, by adopting a configuration in which _{one of} the scintillation lights L ₁ and L ₂ is selected using the mirror 8 and guided toward the photodetector 4, the radiation of low energy components is obtained by one detector. Since a transmission image and a radiation transmission image of a high energy component can be acquired, the apparatus can be easily downsized and a radiation detection image of a wide energy component can be obtained. Further, adjustment work such as correction of the optical axis and distortion of the shared part of the optical system 5 such as the mirror 8 is simplified.

Further, since the mirror 8 can be rotated by the rotation drive mechanism 9, the scintillation lights L ₁ and L ₂ radiated from both surfaces of the wavelength conversion plate 3 can be detected without interfering with each other. A radiation detection image can be obtained reliably.

Further, since the control is performed so that the selection timing of the scintillation lights L ₁ and L ₂ by the rotation drive mechanism 9 and the imaging timing by the photodetector 4 are synchronized, the dual energy radiation detection image is not caused to cause image shift. Can be detected. As a result, image processing when obtaining a radiation transmission image of the object A based on the two radiation detection images is simplified.

In addition, this invention is not limited to embodiment mentioned above. For example, various modifications can be adopted as the configuration of the optical system that guides the scintillation lights L ₁ and L ₂ .

For example, even if the common part of the optical system 105 has a structure in which two

mirrors

108 and 109 are arranged in a V shape, like a radiation image acquisition apparatus 101 which is a modification of the present invention shown in FIG. Good. The mirror 108 has its reflection surface 108a facing the mirror 6b, and the mirror 109 has its reflection surface 109a facing the mirror 7b. By

such mirrors

108 and 109, both the scintillation lights L ₁ and L ₂ are simultaneously guided toward the imaging lens 4a of the photodetector 4. With such a structure, the scintillation lights L ₁ and L ₂ radiated from both surfaces of the wavelength conversion plate 3 can be detected at the same time, so that a dual energy radiation detection image can be obtained simultaneously. If the optical system 105 is a dark optical system, that is, an optical system with a deep aperture and a deep depth of field, detection can be performed with a certain degree of clarity by simply replacing the mirror 8 with the

mirrors

108 and 109 in the configuration of the optical system 5. An image can be obtained. On the other hand, when the optical system 105 is a bright optical system, that is, an optical system having a small F value and a shallow depth of field, in order to obtain a clear detection image, between the mirror 6a and the mirror 6b and the mirror. It is preferable that a relay lens 6c and a relay lens 7c are disposed between 7a and the mirror 7b, respectively. Here, FIG. 3 shows an image of a radiation detection image detected by the radiation image acquisition apparatus 101. As described above, the optical system 105 is adjusted so that the scintillation lights L ₁ and L ₂ are divided and guided onto the detection region of the image pickup element in the photodetector 4, and therefore is output from the photodetector 4. in that image signal S _G, included a radiation detecting image G ₂ of a high energy component detected by the radiation detection image G ₁ and the scintillation light L ₂ of the low energy component detected by the scintillation light L ₁ is divided into two Will be.

Further, like the radiographic

image acquisition apparatuses

201a and 201b which are another modification example of the present invention shown in FIGS. 4 and 5, the prism 208a or the prism 208b is arranged as a common part of the optical system 205. Also good. Specifically, the

prism

208a, 208b is configured to change the optical path of the scintillation light L ₁ incident from the mirror 6b side to face the photodetector 4, the optical light path of the scintillation light L ₂ incident from the mirror 7b side Change so that it faces the detector 4. The prism 208a shown in FIG. 4 is a cross dichroic prism configured by bonding four triangular prisms, and the prism 208b shown in FIG. 5 is formed by integrating two triangular prisms to form a V-shaped wedge. Or a single prism molded to have a V-shaped wedge. Even when

such prisms

208a and 208b are used, both the scintillation lights L ₁ and L ₂ can be simultaneously guided toward the imaging lens 4a of the photodetector 4.

Further, like a radiographic image acquisition apparatus 301 which is another modified example of the present invention shown in FIG. 6, the common part of the optical system 305 has a structure in which two

beam splitters

308 and 309 are arranged in a V shape. There may be. Specifically, the

beam splitters

308 and 309 are arranged so that the normal lines of the reflecting

surfaces

308a and 309a are substantially parallel to a plane including the optical paths of the scintillation lights L ₁ and L _2. The reflecting surface 309a is directed to the mirror 6b, and the beam splitter 308 has the reflecting surface 308a directed to the mirror 7b.

Such beam splitters

308 and 309 are arranged on the mirror 6b and mirror 7b sides to form a V shape. With such a configuration of the optical system 305, both the scintillation lights L ₁ and L ₂ are simultaneously guided toward the imaging lens 4 a of the photodetector 4. With such a structure, the scintillation lights L ₁ and L ₂ radiated from both surfaces of the wavelength conversion plate 3 can be detected at the same time, so that a dual energy radiation detection image can be obtained simultaneously. Here, the

beam splitters

308 and 309 may be half mirrors, and the beam splitter 308 has a property of transmitting the wavelength region of the scintillation light L ₁ and reflecting the wavelength region of the scintillation light L _2. , the beam splitter 309 is transmitted through the wavelength region of the scintillation light L _2, and may have a property of reflecting the wavelength region of the scintillation light L _1.

It is also effective to apply the radiation image acquisition apparatus of the above embodiment as a semiconductor fault inspection apparatus in which the object A is a semiconductor device and the semiconductor device is an inspection target. In this case, since the radiation that has passed through the semiconductor device to be inspected is not cut by the imaging unit (image acquisition device for image acquisition), a failure of the semiconductor device can be detected with high accuracy.

Here, the common optical member is preferably a member that selects and guides one of the scintillation lights guided by the first and second optical members toward the image sensor. If such a common optical member is provided, the scintillation light emitted from both surfaces of the wavelength conversion member can be detected by one image sensor, so that the apparatus can be easily downsized and radiation having a wide energy component can be achieved. A detection image can be obtained.

The common optical member is a mirror that reflects the scintillation light guided by the first and second optical members, and a rotation that rotates the mirror to selectively guide the scintillation light toward the image sensor. It is also preferable to have a mechanism. By adopting such a configuration, it is possible to detect the scintillation light emitted from both surfaces of the wavelength conversion member without interfering with each other, so that a dual energy radiation detection image can be obtained with certainty.

Furthermore, it is preferable to further include a control means for controlling the selection timing of the scintillation light by the rotation mechanism and the imaging timing by the imaging device to be synchronized. In this case, the dual energy radiation detection image can be detected without causing image shift.

Furthermore, it is preferable that the common optical member is a member that simultaneously guides both the scintillation light guided by the first and second optical members toward the image sensor. If such a common optical member is provided, scintillation light emitted from both surfaces of the wavelength conversion member can be detected simultaneously, so that a dual energy radiation detection image can be obtained simultaneously.

Here, the common optical member may be a mirror arranged in a V shape, a beam splitter arranged in a V shape, or a prism.

The present invention uses a radiological image acquisition apparatus that acquires a radiographic image of an object by irradiating radiation, and makes it possible to acquire a radiation detection image with reduced noise over a wide energy band.

1, 101, 201a, 201b, 301 ... Radiation image acquisition device, 2 ... Radiation source, 3 ... Wavelength conversion plate (wavelength conversion member), 3a ... Incident surface, 4 ... Photodetector (imaging device), 5, 105, 205, 305 ... optical system, 6a, 6b ... mirror (first optical member), 7a, 7b ... mirror (second optical member), 8, 108, 109 ... mirror (common optical member), 208a, 208b ... Prism (common optical member), 308, 309 ... Beam splitter (common optical member), 9 ... Rotation drive mechanism (common optical member), 11 ... Rotation control unit (control unit), 12 ... Timing control unit (control unit), A: object, L ₁ , L ₂ ... scintillation light.

Claims

A radiation source that emits radiation; and
A plate-like wavelength conversion member that generates scintillation light in response to incidence of the radiation emitted from the radiation source and transmitted through the object;
A first optical member that guides the scintillation light emitted from the radiation incident surface of the wavelength conversion member;
A second optical member that guides the scintillation light emitted from a surface opposite to the surface on the incident side of the wavelength conversion member;
An image sensor that images each of the scintillation lights guided by the first and second optical members;
A common optical member for guiding each of the scintillation lights guided by the first and second optical members toward the image sensor;
A radiological image acquisition apparatus comprising:
The common optical member is a member that selects one of the scintillation lights guided by the first and second optical members and guides the light toward the imaging element.
The radiological image acquisition apparatus according to claim 1.
The common optical member selectively guides the scintillation light toward the imaging element through a mirror that reflects the scintillation light guided by the first and second optical members, and the mirror. A rotation mechanism for rotating the
The radiographic image acquisition apparatus according to claim 2.
Control means for controlling the scintillation light selection timing by the rotation mechanism and the imaging timing by the imaging device to be synchronized;
The radiographic image acquisition apparatus according to claim 3.
The common optical member is a member that simultaneously guides both the scintillation light guided by the first and second optical members toward the imaging element.
The radiological image acquisition apparatus according to claim 1.
The common optical member is a mirror arranged in a V shape,
The radiological image acquisition apparatus according to claim 5.
The common optical member is a beam splitter arranged in a V shape,
The radiological image acquisition apparatus according to claim 5.
The common optical member is a prism;
The radiological image acquisition apparatus according to claim 5.