JP2017003639A - Radiographic image detection lens device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiographic image detection lens device that offers improved view angle, etc., using a configuration with a small number of lenses.SOLUTION: A radiographic image detection lens device 10 for focusing scintillation light exiting from a scintillator 20 to an image sensor 5 comprises a first lens 1, a second lens 2, an aperture stop 4, and a third lens 3 arranged in order from the object side. The first lens 1 is a negative meniscus lens having a convex surface on the object side, where at least a surface on one side is an aspherical surface. The second lens 2 is a positive lens having a convex surface on the image side. The second lens 3 is a positive lens having a convex surface on the image side. An effective diameter D12 of an image-side surface 12 of the first lens 1 and a sag amount S12 of the image-side surface 12 of the first lens 1 satisfy the following expression: 0.8<(D12/2)/S12<1.3 ...conditional expression (1).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radiation image detection lens device that condenses scintillation light emitted from a scintillator.

  In taking an X-ray image for medical diagnosis, a technique has been proposed in which X-rays are incident on a scintillator and the scintillation light emitted from the scintillator is condensed on an image sensor by a radiation image detection lens device (Patent Literature). 1). The radiographic image detection lens device described in Patent Document 1 has a lens configuration of five elements in four groups, its F value is 2.8, and the field angle is 46.6 ° (half field angle = 23 .3 °).

JP 2002-350547 A

  However, as in the technique described in Patent Document 1, the number of lenses in the four-group five-lens configuration increases the cost of the radiation image detection lens device and increases the size in the optical axis direction. End up. In addition, since the number of lenses is large, ghost flare is likely to occur. In addition, when the angle of view is 46.6 ° (half angle of view 23.3 °), the incident angle range is narrow. Therefore, it is necessary to provide a large number of radiation image detecting lens devices for the scintillator. Further, in the case of X-ray imaging, if the F value is 2.8, a bright image cannot be obtained, and therefore it is necessary to increase the amount of X-ray irradiation. In that case, the amount of exposure to the human body increases, which is not preferable.

  In view of the above problems, an object of the present invention is to provide a radiation image detecting lens device capable of improving the angle of view and the like with a small number of lens configurations.

In order to solve the above problems, the present invention provides a radiation image detection lens device that condenses scintillation light emitted from a scintillator, and includes a first lens, a second lens, a diaphragm, and an object side from the object side to the image side. A third lens is sequentially arranged, and the first lens is a negative meniscus lens having an aspheric lens surface on at least one side and a convex surface facing the object side, and the second lens has a convex surface facing the image side. The third lens is a positive lens having a convex surface facing the image side,
When the effective diameter of the image side lens surface of the first lens is D12 and the sag amount of the image side lens surface of the first lens is S12, the effective diameter D12 and the sag amount S12 are expressed by the following equations: 8 <(D12 / 2) / S12 <1.3
It is characterized by satisfying.

In the present invention, since the wavelength region of the scintillation light emitted from the scintillator is narrow, it is not necessary to attach importance to measures against chromatic aberration. For this reason, priority can be given to improving the angle of view and brightness, and the number of lenses can be set to three. Therefore, the cost of the radiation image detecting lens device can be reduced, and the size in the optical axis direction can be reduced. In addition, since the number of lenses is small, ghost flare hardly occurs. Further, since the first lens is a negative meniscus lens having at least one aspheric surface and a convex surface facing the object side, it is possible to suppress a decrease in the amount of peripheral light. Therefore, scintillation light can be appropriately condensed in a wide range of angle of view. Furthermore, since the effective diameter D12 of the image side surface of the first lens and the sag amount S12 of the image side surface of the first lens satisfy the above formula, astigmatism can be improved.

  In the present invention, it is preferable that the second lens has a convex surface facing the object side.

  In the present invention, the maximum angle of view is preferably 80 ° or more. With this configuration, the number of radiation image detection lens devices provided for the scintillator can be reduced.

  In the present invention, it is preferable that the F value of the entire lens system including the first lens, the second lens, and the third lens is 2 or less. According to this configuration, a bright image can be obtained.

In the present invention, when the radius of curvature at the center of the image side surface of the first lens is R12, and the focal length of the entire lens system including the first lens, the second lens, and the third lens is f. , Radius of curvature R12 and focal length f are expressed by the following equation: R12 / f ≦ 0.9
It is preferable to satisfy. According to such a configuration, astigmatism can be improved.

  In the present invention, the second lens is preferably made of a glass lens. According to such a configuration, the temperature characteristics can be improved.

In the present invention, when the refractive index of the second lens is n2, the Abbe number of the second lens is ν2, and the Abbe number of the third lens is ν3,
The refractive index n2, Abbe number ν2, and Abbe number ν3 are expressed by the following two expressions 1.7 <n2
ν3 / ν2 <1.6
It is preferable to satisfy any of these. According to such a configuration, it is possible to appropriately collect light in each wavelength region included in the scintillation light.

  In the present invention, it is preferable that a light shielding layer is formed on the edge portion on the image side of the first lens. According to such a configuration, it is possible to suppress the occurrence of ghost flare caused by stray light.

  In the present invention, since the wavelength region of the scintillation light emitted from the scintillator is narrow, it is not necessary to attach importance to measures against chromatic aberration. For this reason, priority can be given to improving the angle of view and brightness, and the number of lenses can be set to three. Therefore, the cost of the radiation image detecting lens device can be reduced, and the size in the optical axis direction can be reduced. In addition, since the number of lenses is small, ghost flare hardly occurs. Further, since the first lens is a negative meniscus lens having at least one aspheric surface and a convex surface facing the object side, it is possible to suppress a decrease in the amount of peripheral light. Therefore, scintillation light can be appropriately condensed in a wide range of angle of view. Furthermore, since the effective diameter of the image side surface of the first lens and the sag amount of the image side surface of the first lens satisfy the above formula, astigmatism can be improved.

It is explanatory drawing of the lens apparatus for a radiographic image detection to which this invention is applied. It is explanatory drawing which shows the lens etc. of the lens apparatus for a radiographic image detection which concerns on Example 1 of this invention. It is explanatory drawing which shows the simulation result of the MTF characteristic of the lens apparatus for a radiographic image detection which concerns on Example 1 of this invention. It is explanatory drawing which shows the simulation result, such as a lateral aberration of the lens apparatus for a radiographic image detection which concerns on Example 1 of this invention. It is explanatory drawing which shows the simulation result of the spherical aberration etc. of the lens apparatus for a radiographic image detection which concerns on Example 1 of this invention. It is explanatory drawing which shows the lens etc. of the lens apparatus for a radiographic image detection which concerns on Example 2 of this invention. It is explanatory drawing which shows the simulation result of the MTF characteristic of the lens apparatus for a radiographic image detection which concerns on Example 2 of this invention. It is explanatory drawing which shows the simulation result, such as a lateral aberration of the lens apparatus for a radiographic image detection which concerns on Example 2 of this invention. It is explanatory drawing which shows the simulation result of the spherical aberration etc. of the lens apparatus for a radiographic image detection which concerns on Example 2 of this invention. It is explanatory drawing which shows the lens etc. of the lens apparatus for a radiographic image detection which concerns on Example 3 of this invention. It is explanatory drawing which shows the simulation result of the MTF characteristic of the lens apparatus for a radiographic image detection which concerns on Example 3 of this invention. It is explanatory drawing which shows the simulation result, such as a lateral aberration of the lens apparatus for a radiographic image detection which concerns on Example 3 of this invention. It is explanatory drawing which shows the simulation result, such as spherical aberration of the lens apparatus for a radiographic image detection which concerns on Example 3 of this invention.

A radiation image detecting lens device to which the present invention is applied will be described below with reference to the drawings. In addition, in FIG.1, FIG.2, FIG.6, FIG.10, Table 1, Table 2, and Table 3 referred to below, each surface 1-10 is shown in parenthesis, and each surface points out the following surfaces. ing.
First surface (1) .. Scintillator 20
Second surface (2) .. Object-side lens surface 11 of the first lens 1
Third surface (3)... Image-side lens surface 12 of the first lens 1
Fourth surface (4) .. Object-side lens surface 21 of the second lens 2
Fifth surface (5)... Image side lens surface 22 of the second lens 2
6th surface (6) · · 4 aperture
Seventh surface (7) .. Object-side lens surface 31 of the third lens 3
Eighth surface (8)... Image side lens surface 32 of the third lens 3
Ninth surface (9) ··· Filter 8
Tenth surface (10) ..Image sensor 5

  FIG. 1 is an explanatory diagram of a radiation image detecting lens device 10 to which the present invention is applied. A radiological image detection lens device 10 shown in FIG. 1 is an optical device that condenses scintillation light emitted from a scintillator 20. In the radiological image detection lens device 10, for example, X-rays emitted from an X-ray tube (not shown) during X-ray imaging, X-rays transmitted through a subject (not shown) are scintillator 20 (X When incident on a line scintillator, the scintillator 20 generates scintillation light composed of fluorescence. Therefore, if scintillation light is condensed on the image sensor 5 by the radiation image detection lens device 10, a radiation image (X-ray image) can be obtained. In this embodiment, the scintillation light is visible light having a center wavelength of 0.550 μm.

In the present embodiment, the radiation image detecting lens device 10 includes a first lens 1, a second lens 2, an aperture 4, and a third lens 3 arranged in this order from the object side to the image side. The two lenses 2, the diaphragm 4, and the third lens 3 are held by a cylindrical holder 9. At this time, a cylindrical first intermediate ring 6 is disposed between the first lens 1 and the second lens 2. The diaphragm 4 is constituted by an end portion on the object side of the second intermediate ring 7 disposed between the second lens 2 and the third lens 3.

  A large diameter portion 91, a medium diameter portion 92 having an outer diameter smaller than that of the large diameter portion 91, and a small diameter portion 93 having an outer diameter smaller than that of the medium diameter portion 92 are formed in this order from the object side to the image side. ing. The first lens 1 is disposed inside the large diameter portion 91, the first intermediate ring 6 and the second lens 2 are disposed inside the medium diameter portion 92, and the second intermediate ring 7 is disposed inside the small diameter portion 93. And the 3rd lens 3 is arrange | positioned.

  The first lens 1 is a negative meniscus lens having an aspheric surface on at least one side and a convex surface facing the object side. The second lens 2 is a positive lens having a convex surface facing the image side. In the present embodiment, the second lens 2 is a biconvex lens having a convex surface on the object side in addition to the image side. The third lens 3 is a positive lens having a convex surface facing the image side.

Here, the effective diameter of the image-side lens surface 12 (third surface (3)) of the first lens 1 is D12, and the sag of the image-side lens surface 12 (third surface (3)) of the first lens 1 is assumed. When the amount is S12, the effective diameter D12 and the sag amount S12 are expressed by the following equation: 0.8 <(D12 / 2) / S12 <1.3 Conditional expression (1)
Meet.

  In this way, in the radiation image detecting lens device 10 of the present embodiment, the scintillation light emitted from the scintillator 20 has a narrow wavelength range, and therefore, it is not necessary to attach importance to measures against chromatic aberration. For this reason, the number of lenses is set to three in order to prioritize the improvement of the angle of view and the brightness. Therefore, the cost of the radiation image detecting lens device 10 can be reduced, and the size in the optical axis direction can be reduced. In addition, since the number of lenses is small, ghost flare hardly occurs. Further, since the first lens 1 is a negative meniscus lens having an aspheric surface on at least one side and a convex surface facing the object side, it is possible to suppress a decrease in peripheral light amount. Therefore, scintillation light can be appropriately condensed in a wide range of angle of view. Furthermore, since the effective diameter D12 of the image-side lens surface of the first lens 1 and the sag amount S12 of the image-side lens surface 12 of the first lens 1 satisfy the above formula, astigmatism is improved. Can do. In conditional expression (1), when (D12 / 2) / S12 is 0.8 or less, sufficient power cannot be obtained, while when (D12 / 2) / S12 is 1.3 or more, Astigmatism increases.

  In this embodiment, the maximum field angle is 80 ° or more. For this reason, the number of radiation image detection lens devices provided for the scintillator 20 can be reduced.

  Further, the F value of the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is 2 or less. For this reason, a bright image can be obtained.

When the radius of curvature at the center of the image side lens surface of the first lens 1 is R12 and the focal length of the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is f, The radius of curvature R12 and the focal length f are expressed by the following equation: R12 / f ≦ 0.9 ·· Condition (2)
Meet. For this reason, astigmatism can be improved.

  Here, the second lens 2 is made of a glass lens. For this reason, temperature characteristics can be improved.

When the refractive index of the second lens 2 is n2, the Abbe number of the second lens 2 is ν2, and the Abbe number of the third lens 3 is ν3,
Refractive index n2, Abbe number ν2, and Abbe number ν3 are expressed by the following two expressions 1.7 <n2 ··· conditional expression (3)
ν3 / ν2 <1.6 ·· Condition (4)
Both of these are met. For this reason, the light of each wavelength range contained in scintillation light can be appropriately condensed.

  In this embodiment, a light shielding layer 14 called so-called black is formed on the image side of the edge portion 13 of the first lens 1. For this reason, generation | occurrence | production of the ghost flare resulting from the stray light which injected into the edge part 13 can be suppressed.

[Example 1]
FIG. 2 is an explanatory diagram illustrating the lens and the like of the radiation image detecting lens device 10 according to the first embodiment of the invention. FIG. 3 is an explanatory diagram showing simulation results of MTF (Modulation Transfer Function) characteristics of the radiation image detecting lens device 10 according to Example 1 of the present invention, and FIGS. 3 (a), 3 (b), and 3 (c). These are explanatory drawing which shows MTF characteristic of normal temperature (+25 degreeC), explanatory drawing which shows MTF characteristic of -10 degreeC, and explanatory drawing which shows MTF characteristic of +60 degreeC. FIG. 3 shows the MTF characteristics when the distance from the center is 0 mm and 2.61 mm. S is attached to the sagittal characteristic, and T is attached to the tangential characteristic. FIGS. 4A and 4B are explanatory diagrams illustrating simulation results of lateral aberration and the like of the radiation image detecting lens device 10 according to the first embodiment of the present invention. FIGS. 4A and 4B are distances from the center of 0 mm. It is explanatory drawing of lateral aberration in 2.61 mm, and explanatory drawing of astigmatism. FIG. 4B also shows distortion. Distortion indicates the rate of change of the image in the central part and the peripheral part of the imaging, and the smaller the absolute value of the numerical value representing the distortion, the more accurate the lens system. In FIG. 4B, S is added to the sagittal characteristic, and T is added to the tangential characteristic. FIGS. 5A and 5B are explanatory diagrams illustrating simulation results of spherical aberration and the like of the radiation image detecting lens device 10 according to the first embodiment of the present invention. FIGS. 5A and 5B are explanatory diagrams of spherical aberration. It is also an explanatory diagram of lateral chromatic aberration in light of each wavelength region (0.540 μm, 0.550 μm, 0.560 μm).

  As shown in FIG. 2, the radiation image detecting lens device 10 of this example includes a first lens 1, a second lens 2, an aperture 4, and an object side from the object side to the image side, as described with reference to FIG. 1. The third lens 3 is arranged in order. Each configuration of the radiographic image detection lens apparatus 10 configured as described above is as shown in Table 1. The first column from the top of Table 1 shows the effective focal length (f: Effective Focal Length), distance between object images (Total Track), F value (Image Space F / #) of the entire lens system, and maximum field angle (Max. Field of Angle) are shown. The F value is an index indicating the brightness of the entire lens system.

  In the second column from the top of Table 1, the radius of curvature (Radius), thickness (Thickness), refractive index Nd, Abbe number νd, focal length fn, and sag amount sag of each surface of the radiation image detecting lens device 10 are shown. It is shown.

  In the third column and the fourth column from the top of Table 1, aspherical coefficients A3 to A10 when the aspherical shape of each surface of the radiation image detecting lens device 10 is expressed by the following equation (Equation 1) are shown. , A12, A14, and A16 are shown. In the following expression, the axis in the optical axis L direction is Z, the height in the direction perpendicular to the optical axis L is r, the conic coefficient is K, and the center curvature is c. The unit of each value is mm. The same applies to Tables 2 and 3 described later.

As can be seen from FIG. 2 and Table 1, in the radiation image detecting lens device 10 of the present example, the first lens 1 is an aspherical surface in which the object-side lens surface 11 (second surface (2)) is convex, The image-side lens surface 12 (third surface (3)) is a meniscus lens having a concave aspheric surface and has negative power. The first lens 1 is made of a plastic lens. On the image side of the edge portion 13 of the first lens 1, a light shielding layer 14 called so-called black is formed.

  In the second lens 2, the object-side lens surface 21 (fourth surface (4)) is a convex aspheric surface, and the image-side lens surface 22 (fifth surface (5)) is a convex aspheric surface. It is a biconvex lens and has positive power. The second lens 2 is made of a glass lens.

  In the third lens 3, the object-side lens surface 31 (seventh surface (7)) is a convex aspheric surface, and the image-side lens surface 32 (eighth surface (8)) is a convex aspheric surface. It is a biconvex lens and has positive power. The third lens 3 is made of a plastic lens.

  Here, the effective diameter D12 of the lens surface 12 (third surface (3)) of the first lens 1 is 6.427 mm, and the sag amount S12 of the lens surface 12 (third surface (3)) of the first lens 1 is. Is 2.94. Therefore, (D12 / 2) / S12 is 1.09, which satisfies the conditional expression (1). The maximum angle of view is 86.1 °, which is 80 ° or more. The F value of the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is 1.5 and is 2 or less. The radius of curvature R12 at the center of the lens surface 12 (third surface (3)) of the first lens 1 is 2.061 mm, and the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is used. Has a focal length f of 2.682. Therefore, R12 / f is 0.77 and is 0.9 or less. Therefore, the conditional expression (2) is satisfied. The refractive index n2 of the second lens 2 is 1.806, which satisfies the conditional expression (3). The Abbe number ν2 of the second lens 2 is 40.7, and the Abbe number ν3 of the third lens 3 is 55.8. Therefore, ν3 / ν2 is 1.37, which satisfies the conditional expression (4).

  Therefore, the lens apparatus 10 for detecting a radiographic image of this example has the optical characteristics shown in FIGS. 3, 4 and 5, and can improve the angle of view and the like with a small number of lens configurations. The effects described with reference to FIG.

[Example 2]
FIG. 6 is an explanatory diagram illustrating a lens and the like of the radiation image detecting lens device 10 according to the second embodiment of the invention. FIG. 7 is an explanatory diagram showing the simulation results of the MTF characteristics of the radiation image detecting lens device 10 according to the second embodiment of the present invention. FIGS. 7 (a), 7 (b), and 7 (c) are room temperature (+25 FIG. 6 is an explanatory diagram showing an MTF characteristic at − ° C .; FIG. 7 shows the MTF characteristics when the distance from the center is 0 mm and 2.61 mm. S is attached to the sagittal characteristic, and T is attached to the tangential characteristic. FIGS. 8A and 8B are explanatory diagrams illustrating simulation results of lateral aberration and the like of the radiation image detecting lens device 10 according to the second embodiment of the present invention. FIGS. 8A and 8B are distances from the center of 0 mm. It is explanatory drawing of lateral aberration in 2.61 mm, and explanatory drawing of astigmatism. FIG. 8B also shows distortion. In FIG. 8B, the sagittal characteristics are marked with S, and the tangential characteristics are marked with T. FIGS. 9A and 9B are explanatory diagrams illustrating simulation results of spherical aberration and the like of the radiation image detecting lens device 10 according to the second embodiment of the present invention. FIGS. 9A and 9B are explanatory diagrams of spherical aberration. It is also an explanatory diagram of lateral chromatic aberration in light of each wavelength region (0.540 μm, 0.550 μm, 0.560 μm).

  As shown in FIG. 6, the radiation image detecting lens device 10 of the present example includes a first lens 1, a second lens 2, an aperture 4, and an object side from the object side to the image side, as described with reference to FIG. 1. The third lens 3 is arranged in order. Each configuration of the radiographic image detection lens device 10 configured as described above is as shown in Table 2.

  As can be seen from FIG. 6 and Table 2, in the radiographic image detection lens device 10 of this example, the first lens 1 has a convex aspherical surface 11 on the object side and a concave surface 12 on the image side. This is a meniscus lens composed of an aspherical surface having negative power. The first lens 1 is made of a plastic lens. On the image side of the edge portion 13 of the first lens 1, a light shielding layer 14 called so-called black is formed.

  The second lens 2 is a biconvex lens in which the object-side lens surface 21 is a convex aspheric surface and the image-side lens surface 22 is a convex aspheric surface, and has positive power. The second lens 2 is made of a glass lens.

  The third lens 3 is a biconvex lens in which the object-side lens surface 31 is a convex aspheric surface and the image-side lens surface 32 is a convex aspheric surface, and has positive power. The third lens 3 is made of a plastic lens.

Here, the effective diameter D12 of the lens surface 12 of the first lens 1 is 6.498 mm, and the sag amount S12 of the lens surface 12 of the first lens 1 is 3.01, and therefore (D12 / 2) / S12. Is 1.08, which satisfies the conditional expression (1). The maximum angle of view is 86.1 °, which is 80 ° or more. The F value of the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is 1.5 and is 2 or less. The radius of curvature R12 at the center of the lens surface 12 of the first lens 1 is 2.103 mm, and the focal length f of the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is 2.658. It is. Therefore, R12 / f is 0.79 and is 0.9 or less. Therefore, the conditional expression (2) is satisfied. The refractive index n2 of the second lens 2 is 1.806, which satisfies the conditional expression (3). The Abbe number ν2 of the second lens 2 is 40.7, and the Abbe number ν3 of the third lens 3 is 55.8. Therefore, ν3 / ν2 is 1.37, which satisfies the conditional expression (4).

  Therefore, the lens apparatus 10 for detecting a radiographic image of this example has the optical characteristics shown in FIGS. 7, 8, and 9, and can improve the angle of view with a small number of lens configurations. The effects described with reference to FIG.

[Example 3]
FIG. 10 is an explanatory diagram illustrating a lens and the like of the radiation image detecting lens device 10 according to the third embodiment of the invention. 11A and 11B are explanatory diagrams showing simulation results of MTF characteristics of the radiation image detecting lens device 10 according to the third embodiment of the present invention. FIGS. 11A, 11B, and 11C are room temperature (+25). FIG. 6 is an explanatory diagram showing an MTF characteristic at − ° C., an explanatory diagram showing an MTF characteristic at −10 ° C., and an explanatory diagram showing an MTF characteristic at + 60 ° C. FIG. 11 shows the MTF characteristics when the distance from the center is 0 mm and 2.61 mm. S is attached to the sagittal characteristic, and T is attached to the tangential characteristic. FIGS. 12A and 12B are explanatory diagrams illustrating simulation results of lateral aberration and the like of the radiation image detecting lens device 10 according to the second embodiment of the present invention. FIGS. 12A and 12B are distances from the center of 0 mm. It is explanatory drawing of lateral aberration in 2.61 mm, and explanatory drawing of astigmatism. FIG. 12B also shows distortion. In FIG. 12B, the sagittal characteristic is denoted by S, and the tangential characteristic is denoted by T. FIGS. 13A and 13B are explanatory diagrams illustrating simulation results of spherical aberration and the like of the radiation image detecting lens device 10 according to the second embodiment of the present invention. FIGS. 13A and 13B are explanatory diagrams of spherical aberration. It is also an explanatory diagram of lateral chromatic aberration in light of each wavelength region (0.540 μm, 0.550 μm, 0.560 μm).

  As shown in FIG. 10, the radiation image detection lens device 10 of the present example includes a first lens 1, a second lens 2, an aperture 4, and an object side from the object side to the image side, as described with reference to FIG. 1. The third lens 3 is arranged in order. Each configuration of the radiographic image detection lens device 10 configured as described above is as shown in Table 3.

  As can be seen from FIG. 10 and Table 3, in the radiation image detecting lens device 10 of the present example, the first lens 1 has a convex aspherical surface 11 on the object side and a concave surface 12 on the image side. This is a meniscus lens composed of an aspherical surface having negative power. The first lens 1 is made of a plastic lens. On the image side of the edge portion 13 of the first lens 1, a light shielding layer 14 called so-called black is formed.

  The second lens 2 is a biconvex lens in which the object-side lens surface 21 is a convex aspheric surface and the image-side lens surface 22 is a convex aspheric surface, and has positive power. The second lens 2 is made of a glass lens.

  The third lens 3 is a biconvex lens in which the object-side lens surface 31 is a convex aspheric surface and the image-side lens surface 32 is a convex aspheric surface, and has positive power. The third lens 3 is made of a plastic lens.

Here, the effective diameter D12 of the lens surface 12 of the first lens 1 is 6.394 mm, and the sag amount S12 of the lens surface 12 of the first lens 1 is 2.93. Therefore, (D12 / 2) / S12. Is 1.09, which satisfies the conditional expression (1). The maximum angle of view is 86.2 °, which is 80 ° or more. The F value of the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is 1.5 and is 2 or less. The radius of curvature R12 at the center of the lens surface 12 of the first lens 1 is 2.050 mm, and the focal length f of the entire lens system including the first lens 1, the second lens 2, and the third lens 3 is 2.679. It is. Therefore, R12 / f is 0.77 and is 0.9 or less. Therefore, the conditional expression (2) is satisfied. The refractive index n2 of the second lens 2 is 1.768, which satisfies the conditional expression (3). The Abbe number ν2 of the second lens 2 is 49.2, and the Abbe number ν3 of the third lens 3 is 55.8. Therefore, ν3 / ν2 is 1.13, which satisfies the conditional expression (4).

  Therefore, the lens apparatus 10 for detecting a radiographic image of this example has the optical characteristics shown in FIGS. 11, 12, and 13, and can improve the angle of view and the like with a small number of lens configurations. The effects described with reference to FIG.

DESCRIPTION OF SYMBOLS 1 .... 1st lens 2 ... 2nd lens 3 ... 3rd lens 4 ... Diaphragm 10 ... Radiation image detection lens apparatus 13 ... Edge part 14 ... Shading layer 20 ... Scintillator

Claims (8)

A radiological image detection lens device that collects scintillation light emitted from a scintillator,
A first lens, a second lens, a diaphragm, and a third lens are sequentially arranged from the object side to the image side,
The first lens is a negative meniscus lens having an aspheric lens surface on at least one side and a convex surface facing the object side,
The second lens is a positive lens having a convex surface facing the image side,
The third lens is a positive lens having a convex surface facing the image side,
The effective diameter of the image side lens surface of the first lens is D12,
When the sag amount on the image side lens surface of the first lens is S12,
The effective diameter D12 and the sag amount S12 are expressed by the following formula: 0.8 <(D12 / 2) / S12 <1.3
A lens device for detecting a radiographic image, characterized in that:   The radiographic image detection lens device according to claim 1, wherein the second lens has a convex surface directed toward the object side.   The lens apparatus for detecting a radiographic image according to claim 1 or 2, wherein the maximum angle of view is 80 ° or more.   4. The radiological image detection according to claim 1, wherein an F value of an entire lens system including the first lens, the second lens, and the third lens is 2 or less. 5. Lens device. The radius of curvature at the center of the image side surface of the first lens is R12,
When the focal length of the entire lens system including the first lens, the second lens, and the third lens is f, the radius of curvature R12 and the focal length f are expressed by the following formula: R12 / f ≦ 0.9
The lens apparatus for detecting a radiographic image according to any one of claims 1 to 4, wherein:   The radiographic image detection lens device according to claim 1, wherein the second lens is made of a glass lens. The refractive index of the second lens is n2,
The Abbe number of the second lens is ν2,
When the Abbe number of the third lens is ν3,
The refractive index n2, Abbe number ν2, and Abbe number ν3 are expressed by the following two expressions 1.7 <n2
ν3 / ν2 <1.6
The radiographic image detection lens device according to claim 1, wherein both of the above are satisfied.   The radiographic image detection lens device according to claim 1, wherein a light-shielding layer is formed on an edge portion on the image side of the first lens.

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