X-ray imaging system

Abstract

To provide an x-ray imaging system that can reflect the spatial resolution obtained by adjusting the input field of view in a captured image.SOLUTION: An x-ray imaging system includes a sample table 1 on which an object to be inspected W is placed, an x-ray generator 2 that irradiates the object to be inspected W with x-rays, an x-ray image intensifier 3 that converts the x-rays into a visible light image, an x-ray image intensifier power supply unit 31 that supplies a voltage to the x-ray image intensifier 3, an imaging unit 4 that includes a lens system 41 and a camera 44 and is provided on the output side of the x-ray image intensifier 3 to capture a visible light image, a first adjustment mechanism 43 that changes the imaging magnification of the lens system 41, an x-ray image intensifier control unit 32 that adjusts the applied voltage from the x-ray image intensifier power supply unit 31 to change the input field of view of the x-ray image intensifier 3, and a first adjustment mechanism control unit 43a that controls the first adjustment mechanism 43 to change the imaging magnification of the lens system 41 corresponding to the input field of view.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to an x-ray imaging system that includes an x-ray image intensifier that converts an x-ray radiographic image into a visible light image. [Background technology]

[0002] An X-ray image intensifier is a device that converts an X-ray image that has passed through an object to electrons at the input surface, reduces and accelerates the electrons using an electron lens, and converts them into a high-brightness visible light image at the output surface. The resulting visible light image can be converted into an electrical signal, which is a video signal, and displayed as a fluoroscopic image on a monitor. Such X-ray image intensifiers are used in medical X-ray imaging systems and industrial non-destructive testing devices.

[0003] The X-ray image intensifier is configured by storing an image intensifier tube in a housing to which an X-ray image intensifier power supply unit is connected. The image intensifier tube is made of a vacuum container with an input window made of aluminum or the like. Inside the image intensifier tube, an input surface, an input fluorescent screen, a photocathode, multiple focusing electrodes, an anode, and an output fluorescent screen are arranged to form an electron lens system. The generated electron image is converted into a visible light image by the output fluorescent screen. The converted visible light image is configured to be output to the outside of the X-ray image intensifier through the output surface glass. The output visible light image is captured using a lens and a camera and converted into an electrical signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-23477 Summary of the Invention [Problem to be solved by the invention]

[0005] Some X-ray image intensifiers can change the input field of view of the input window to any diameter. In general, the smaller the effective diameter becomes by adjusting the input field of view, the higher the spatial resolution of the image formed on the output phosphor screen. Therefore, it is desirable to change the input field of view to any diameter depending on whether the size of the field of view or the spatial resolution is to be prioritized. On the other hand, the imaging magnification of a camera that captures a visible light image is constant, and most cameras use all pixels in their imaging area. Therefore, there is a possibility that the improvement in spatial resolution achieved by setting the effective diameter to a small value is not fully reflected in the image captured by the camera.

[0006] In order to solve the above problem, an object of this embodiment is to provide an X-ray imaging system capable of reflecting the spatial resolution obtained by adjusting the input field of view in a captured image. [Means for solving the problem]

[0007] The X-ray imaging system of the embodiment has the following configuration. the X-ray image intensifier control unit adjusting an applied voltage from the X-ray image intensifier power supply unit to change an input field of view of the X-ray image intensifier; and a first adjustment mechanism for changing the imaging magnification of the lens system.

[0008] The X-ray image intensifier device of the embodiment may further include the following configuration. (1) The imaging unit further includes an imaging unit moving mechanism that moves the imaging unit in an X-axis direction, and an imaging unit moving mechanism control unit that controls the imaging unit moving mechanism to move the imaging unit in the X-axis direction and adjust a focal length so that the camera can focus on and capture the visible light image, and the imaging unit moving mechanism control unit is configured to adjust the focal length of the imaging unit after the imaging magnification is adjusted in accordance with the input field of view.

[0009] (2) The imaging unit further includes an optical aperture provided in the lens system and a second adjustment mechanism that adjusts the aperture value of the optical aperture, and the control unit further includes a second adjustment mechanism control unit that controls the second adjustment mechanism to adjust the aperture value of the optical aperture, and the second adjustment mechanism control unit is configured to adjust the aperture value of the optical aperture after the imaging magnification is adjusted in accordance with the input field of view.

[0010] (3) The first adjustment mechanism control unit has a storage unit that stores the imaging magnification in association with a predetermined input field of view.

[0011] (4) The imaging unit movement mechanism control unit has a storage unit that stores the focal length in association with a given input field of view.

[0012] (5) The lens system is a macro lens with variable imaging magnification.

[0013] (6) The lens system is a compound lens in a tandem configuration including a zoom lens with variable imaging magnification and a fixed-focus lens.

[0014] (7) The first adjustment mechanism adjusts the imaging magnification to M L =(d I / d O )×2R I ×P C The imaging magnification calculation unit calculates the image magnification from L is the imaging magnification of the lens system, d I is the input field of view of the X-ray image intensifier, d Ois the diameter of the output phosphor screen of the X-ray image intensifier, R I is the spatial resolution per diameter of the input phosphor screen of the X-ray image intensifier, P C is the pixel pitch of the camera.

[0015] (8) The imaging magnification calculation unit calculates the imaging magnification as M L =(d I / d O )×2R I ×P C ×k, where k is a coefficient for adjusting the imaging magnification of the lens system.

[0016] (9) The present invention further includes an imaging unit moving mechanism that moves the imaging unit in X, Y, and Z axis directions, and an imaging unit moving mechanism control unit that controls the imaging unit moving mechanism to move the imaging unit in the X axis direction to adjust a focal length and to move the imaging unit in the Y and Z axis directions to align the center of the output phosphor screen of the X-ray image intensifier with the center of the imaging element of the camera, wherein the imaging unit moving mechanism control unit is configured to adjust the focal length of the imaging unit and perform the alignment after the imaging magnification is adjusted in accordance with the input field of view. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing an X-ray imaging system according to an embodiment. [Diagram 2] 4 is a flowchart showing the operation of the X-ray imaging system according to the embodiment. [Diagram 3] FIG. 13 is a configuration diagram showing a compound lens in a tandem configuration in an X-ray imaging system according to another embodiment. [Figure 4] FIG. 2 is an explanatory diagram for explaining each variable used in Equation 1. [Diagram 5] FIG. 13 is a schematic diagram showing an X-ray imaging system according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [1. First embodiment] [1-1. Configuration of the embodiment] 1 and 2, a configuration of an X-ray imaging system 100 according to an embodiment will be described below. The X-ray imaging system 100 irradiates an inspection object W with X-rays and converts the X-rays transmitted through the inspection object W into a visible light image. The X-ray imaging system 100 captures this visible light image to obtain a visible light image of the inspection object W.

[0019] As shown in FIG. 1, the X-ray imaging system 100 includes a sample table 1 on which an object to be inspected W is placed, an X-ray generator 2 that irradiates the object to be inspected W with X-rays, an X-ray image intensifier 3 that converts the X-rays into a visible light image, and an imaging unit 4 that captures the visible light image. In the figure, the X-ray image intensifier is represented as X-ray II. The sample table 1, the X-ray generator 2, the X-ray image intensifier 3, and the imaging unit 4 are integrally arranged at a predetermined interval along the optical axis of the X-rays. Furthermore, the X-ray imaging system 100 includes a control unit that controls the operations of the sample table 1, the X-ray generator 2, the X-ray image intensifier 3, and the imaging unit 4.

[0020] The sample table 1 is a platform having a mounting surface on which an object to be inspected W is placed. The sample table 1 may include a sample table moving mechanism 11 and a sample table rotating mechanism 12. The sample table moving mechanism 11 moves the mounting surface in a parallel or perpendicular direction. As the sample table moving mechanism 11, for example, a ball screw mechanism driven by a servo motor can be used. The sample table moving mechanism 11 moves the object to be inspected W in a parallel or perpendicular direction to the mounting surface of the sample table 1 by driving the servo motor. By moving the sample table moving mechanism 11, the object to be inspected W can be aligned with the optical axis of the X-rays.

[0021] The sample table rotating mechanism 12 rotates the mounting surface of the sample table 1 around an axis perpendicular to the mounting surface. The sample table rotating mechanism 12 is provided below the sample table moving mechanism 11, and is, for example, an actuator including a drive source such as a motor. The sample table rotating mechanism 12 may be provided above the sample table moving mechanism 11. The sample table rotating mechanism 12 rotates the mounting surface around an axis perpendicular to the mounting surface. The sample table 1 may be fixed, and the X-ray generator 2 and the X-ray image intensifier 3 may be fixed to the ends of a C-shaped arm, for example, and the arm may be rotated to move the X-ray generator 2 and the X-ray image intensifier 3 around the object W to be inspected. A sample table control unit 13 is connected to the sample table moving mechanism 11 and the sample table rotating mechanism 12 of the sample table 1.

[0022] The X-ray generator 2 is an irradiation unit that irradiates a conical X-ray beam in the horizontal direction. The X-ray beam is a bundle of radiation that expands into a cone shape with the X-ray focal point 21 of the X-ray generator 2 as the apex. The X-ray generator 2 is, for example, an X-ray tube. The X-ray beam irradiated from the X-ray generator 2 is configured to pass through an object W to be inspected placed on a sample table 1 and reach an X-ray image intensifier 3. The X-ray generator 2 includes an X-ray generator driving mechanism (not shown) that changes the distance from the object W to be inspected, the position in the height direction (Z direction), etc. An X-ray generator control unit 22 is connected to the X-ray generator driving mechanism.

[0023] The X-ray image intensifier 3 converts the X-rays transmitted through the object to be inspected W into a visible light image, and is provided facing the output side of the X-ray generator 2. The X-ray image intensifier 3 is provided facing the X-ray generator 2. Therefore, the sample table 1 and the object to be inspected W are located between the X-ray generator 2 and the X-ray image intensifier 3. The X-ray image intensifier 3 is configured by storing an image intensifier tube in a housing to which an X-ray image intensifier power supply unit 31 is connected. In the drawings, the X-ray image intensifier power supply unit is referred to as the power supply unit.

[0024] An image intensifier tube is a sealed vacuum vessel with an input window on the X-ray entrance side. The input window has a convex curved shape that protrudes toward the outside in order to withstand atmospheric pressure. Metal plates made of aluminum or beryllium, which have high transmittance and can withstand atmospheric pressure, can be used as the input window.

[0025] An input surface (input phosphor screen and photocathode) is formed as electrodes on the inner surface of the input window. The input phosphor screen converts the X-ray image into a visible light image. The photocathode converts the visible light image into an electron image. Next, multiple focusing electrodes and anodes are provided as electron deflection and acceleration sections, and the X-ray image is formed on the output phosphor screen. The multiple focusing electrodes and anodes form an electron lens, allowing the electron image from the input surface to be focused on a certain area of ​​the output phosphor screen.

[0026] When the X-ray image intensifier 3 is in operation, a high voltage is applied to the input window, with the input window being negative and the anode being positive. This electron multiplication mechanism controls the trajectory of the electrons so that the electron image generated at the input window is accelerated and focused toward the output phosphor screen. The output phosphor screen converts the focused electron image into a visible light image. The converted visible light image is output to the outside of the X-ray image intensifier 3 via the output surface glass. As described above, the X-ray image intensifier 3 is configured to convert the X-ray image into an electron image, intensify the electrons by imparting energy to them through acceleration, and generate a bright visible light image on the output phosphor screen.

[0027] An X-ray image intensifier power supply unit 31 is connected to the X-ray image intensifier 3. The X-ray image intensifier power supply unit 31 includes an electrode voltage supply circuit that supplies voltage to the photocathode, focusing electrode, and anode of the image intensifier tube. The power supply voltage supply circuit is configured to be able to apply 0 V to the input surface of the image intensifier tube, several hundred V to several kV to the focusing electrode, and approximately 20 kV to the anode (output phosphor screen). An X-ray image intensifier control unit 32 is connected to the X-ray image intensifier power supply unit 31.

[0028] The imaging unit 4 is provided on the output side of the X-ray image intensifier 3, and is a component that captures a visible light image output by the output fluorescent screen of the X-ray image intensifier 3. The imaging unit 4 includes a lens system 41, an optical aperture 42, an adjustment mechanism 43, a camera 44, and an imaging unit movement mechanism 45. The lens system 41 includes a plurality of lenses, and forms a visible optical image emitted from the output surface glass of the X-ray image intensifier 3 on the camera 44. A macro lens with a variable imaging magnification can be used as the lens system 41. It is preferable to use a macro lens whose imaging magnification can be changed at least 1 to 3 times.

[0029] The lens system 41 includes, for example, a first lens 41a and a second lens 41b. The first lens 41a and the second lens 41b are combined and arranged on the same optical axis. The first lens 41a converts the visible light emitted from the output surface glass into parallel light. The second lens 41b focuses the parallel light emitted from the first lens 41a and forms an image on the imaging surface of the camera 44.

[0030] The optical diaphragm 42 is provided between the first lens 41a and the second lens 41b, and adjusts the amount of parallel light passing through. The diameter of the optical diaphragm 42 can be set to a desired size, and the optical diaphragm 42 is a movable diaphragm whose aperture value can be adjusted. The adjustment mechanism 43 is a mechanism for adjusting the imaging magnification of the lens system 41 and the aperture value of the optical diaphragm 42. In the adjustment mechanism 43, the mechanism for adjusting the imaging magnification of the lens system 41 can be regarded as a first adjustment mechanism, and the mechanism for adjusting the aperture value of the optical diaphragm 42 can be regarded as a second adjustment mechanism.

[0031] The adjustment mechanism 43 changes the imaging magnification by adjusting the lens arrangement of the lens system 41 using a motor and its motor driver, etc. The adjustment mechanism 43 also adjusts the aperture value by adjusting the opening degree of the optical diaphragm 42 using a motor and its motor driver, etc. The adjustment mechanism 43 is connected to an adjustment mechanism control unit 43a. Note that the adjustment mechanism 43 may be provided in part or in whole as an integral part of the lens system 41.

[0032] The camera 44 is an imaging tube or a solid-state imaging device (an image sensor such as a CCD or CMOS) that converts the visible light image formed through the second lens 41b into an electric signal. The camera 44 is fixed to the housing of the X-ray image intensifier 3 in a state where it is integrally assembled with the lens system 41 in advance. The electric signal acquired by the camera 44 may be amplified by an amplifier circuit. The electric signal from the camera 44 is output to the image acquisition and display unit O. The image acquisition and display unit O is configured to perform A / D conversion of the electric signal, and perform various image processing such as logarithmic conversion and image density conversion, and display the result.

[0033] The lens system 41, the optical aperture 42, the adjustment mechanism 43, and the camera 44 are assembled together to form the imaging unit 4. The imaging unit moving mechanism 45 is a mechanism for moving the imaging unit 4 in the X-axis direction. The X-axis direction is a direction parallel to the optical axis of the X-rays. The imaging unit moving mechanism 45 moves the imaging unit 4 to adjust the focal position. An imaging unit moving mechanism control unit 45a is connected to the imaging unit moving mechanism 45.

[0034] The sample table control unit 13, the X-ray generator control unit 22, the X-ray image intensifier control unit 32, the adjustment mechanism control unit 43a, and the imaging unit movement mechanism control unit 45a are configured by a computer and a driver circuit that operate according to a predetermined program. The computer is configured by a storage device such as an HDD or SSD, a RAM, a CPU, and the like. In addition, each process of each control unit can be regarded as a control method of the X-ray imaging system 100 executed by a computer, or each process of the control method can be regarded as a control program of the X-ray imaging system 100 that causes a computer to execute the control method. The processing range of the hardware and the processing range of the software including the program can also be set appropriately and are not limited to a specific embodiment.

[0035] In FIG. 1, each control unit is configured independently. However, the sample table control unit 13, the X-ray generator control unit 22, the X-ray image intensifier control unit 32, the adjustment mechanism control unit 43a, and the imaging unit movement mechanism control unit 45a may be realized using the same computer and driver circuit. An operation unit I as an input unit and an image acquisition and display unit O as an output unit are connected to each control unit. An operator causes each control unit to control each component of the X-ray imaging system 100 via the operation unit I. The image acquisition and display unit O includes a display that displays the results of image processing and a GUI. The image acquisition and display unit O is configured to be able to display, for example, a visible light image captured by the imaging unit 4 in a desired format.

[0036] Each control unit will be described in detail. The sample table control unit 13 controls the sample table moving mechanism 11 and the sample table rotating mechanism 12 of the sample table 1. Specifically, the sample table 1 is controlled so as to align the object W placed on the sample table 1 with the optical axis of the X-ray beam. The X-ray generator control unit 22 controls the tube voltage and tube current of the X-ray generator 2 to irradiate the object W with the X-ray beam. That is, under the control of the sample table control unit 13 and the X-ray generator control unit 22, the object W is irradiated with the X-ray beam, and the X-ray image intensifier 3 obtains a fluoroscopic image of the object W. The X-ray image intensifier control unit 32 controls the X-ray image intensifier 3 to convert the fluoroscopic image into a visible light image by the X-ray image intensifier power supply unit 31.

[0037] Here, the X-ray image intensifier control unit 32 is configured to be able to adjust the voltage applied to the anode and focusing electrode of the X-ray image intensifier 3 by controlling the X-ray image intensifier power supply unit 31. By adjusting the voltage applied by the X-ray image intensifier power supply unit 31 and controlling the electronic deflection system of the X-ray image intensifier 3, the input field of view of the X-ray image intensifier 3 can be changed. The input field of view is the effective diameter of the input phosphor screen. In general, the smaller the input field of view, the better the spatial resolution on the input phosphor screen. In other words, making the input field of view smaller brings a specific small range into focus, enabling clearer observation.

[0038] The X-ray image intensifier control unit 32 can store the applied voltage and the input field of view in association with each other. For example, the X-ray image intensifier control unit 32 may store applied voltages that can obtain each input field of view so that the input field of view of the X-ray image intensifier 3 can be changed to three stages of diameter 230 mm, diameter 160 mm, and diameter 120 mm.

[0039] The adjustment mechanism control unit 43a is configured to be able to change the imaging magnification of the lens system 41 by controlling the adjustment mechanism 43. The adjustment mechanism control unit 43a changes the imaging magnification by, for example, adjusting the distance between lens elements of a macro lens. It can be said that the change in the imaging magnification by the adjustment mechanism control unit 43a changes the imaging magnification so that the camera 44 can collect an image that exhibits the spatial resolution of the set input field of view executed in conjunction with the change in the input field of view.

[0040] The adjustment mechanism control unit 43a may have a storage unit that stores the input field of view of the X-ray image intensifier 3 in association with the imaging magnification. For example, the adjustment mechanism control unit 43a may store an imaging magnification optimal for each input field of view, such as an imaging magnification of 1.8 when the input field of view of the X-ray image intensifier 3 has a diameter of 230 mm, an imaging magnification of 1.5 when the input field of view of the X-ray image intensifier 3 has a diameter of 160 mm, and an imaging magnification of 1.3 when the input field of view of the X-ray image intensifier 3 has a diameter of 120 mm. The above-described configuration of the adjustment mechanism control unit 43a can be regarded as a first adjustment mechanism control unit.

[0041] The adjustment mechanism control unit 43a is configured to be able to control the adjustment mechanism 43 to adjust the aperture value of the optical diaphragm 42. The adjustment of the aperture value of the optical diaphragm 42 should be performed after the adjustment mechanism control unit 43a has changed the imaging magnification of the lens system 41 and the imaging unit movement mechanism 45 has moved the lens system 41 and the camera 44. That is, the control is performed in the following order: change of the input field of view, change of the imaging magnification, adjustment of the focal length, and adjustment of the brightness of the output image.

[0042] The adjustment mechanism control unit 43a corrects changes in brightness of the output image accompanying changes in the input field of view and imaging magnification by automatically adjusting the aperture value of the optical diaphragm 42. The adjustment mechanism control unit 43a determines the aperture value by performing a calculation using predetermined parameters such as the imaging magnification and lens characteristics, or a calculation using the brightness of the actual image of the camera 44. The adjustment mechanism control unit 43a determines the aperture value of the optical diaphragm 42 so that the brightness of the obtained visible light image is optimized. The above-mentioned configuration of the adjustment mechanism control unit 43a can be considered as a second adjustment mechanism control unit.

[0043] The imaging unit movement mechanism control unit 45a controls the imaging unit movement mechanism 45 to move the imaging unit 4 in the X-axis direction and adjust the focal length so that the camera 44 can focus and capture the visible light image. The focal length can be the distance between the output fluorescence of the X-ray image intensifier 3 and the imaging element of the camera 44. The imaging unit movement mechanism control unit 45a may have a storage unit that stores the input field of view of the X-ray image intensifier 3 and the focal length in association with each other. For example, the imaging unit movement mechanism control unit 45a may store the optimal focal length for each input field of view, such as a focal length of 220 mm when the input field of view of the X-ray image intensifier 3 is 230 mm in diameter, a focal length of 210 mm when the diameter is 160 mm, and a focal length of 200 mm when the diameter is 120 mm.

[0044] Alternatively, the imaging unit movement mechanism control unit 45a may be configured to determine the focal length by calculation. The imaging unit movement mechanism control unit 45a can determine the focal length at which the lens system 41 focuses on the output fluorescence of the X-ray image intensifier 3 by using a focusing method such as a contrast detection method, a phase difference detection method, or an image plane phase difference detection method. However, the focusing method is not limited to these, and various focusing methods can be adopted. Note that if the lens system 41 has a focal position adjustment function, it is also possible to adjust the focal length by controlling the lens system 41.

[0045] [1-2. Operation of the embodiment] The procedure for changing the input field of view in this embodiment will be described with reference to Fig. 2. Fig. 2 is a flow chart showing the process in which the X-ray image intensifier 3 of this embodiment changes the input field of view.

[0046] First, in step S01, when changing the input field of view, the user inputs a desired input field of view via operation unit I. For example, if the user inputs that the input field of view is to be 230 mm in diameter, X-ray image intensifier control unit 32 adjusts the voltage applied by X-ray image intensifier power supply unit 31 and controls the electronic deflection system of X-ray image intensifier 3 to set the input field of view of X-ray image intensifier 3 to a diameter of 230 mm.

[0047] When the change of the input field of view is completed, the adjustment mechanism control unit 43a controls the adjustment mechanism 43 to change the imaging magnification of the lens system 41 (step S02). For example, when the input field of view of the X-ray image intensifier 3 is changed to a diameter of 230 mm, the adjustment mechanism control unit 43a refers to the storage unit and acquires the imaging magnification associated with the diameter of 230 mm. Then, the adjustment mechanism control unit 43a changes the imaging magnification of the lens system 41 to a predetermined value by controlling the lens elements included in, for example, a macro lens.

[0048] When the change in the imaging magnification is completed, the adjustment mechanism control unit 43a controls the adjustment mechanism 43 to change the aperture value of the optical diaphragm 42 to the smallest value, and the imaging unit movement mechanism control unit 45a controls the imaging unit movement mechanism 45 to move the imaging unit 4 in the X-axis direction to adjust the focal length (step S03). For example, when the input field of view of the X-ray image intensifier 3 is changed to a diameter of 230 mm, the imaging unit movement mechanism control unit 45a refers to the storage unit and obtains the movement distance associated with the diameter of 230 mm. Then, the distance between the output fluorescence of the X-ray image intensifier 3 and the imaging element of the camera 44 is controlled to change the focal length to a predetermined value.

[0049] By setting the aperture value to the smallest value, the depth of field of the lens system 41 becomes shallow, and when the focal length is calculated, the focal length can be adjusted with higher accuracy. When setting the aperture value to the smallest value, measures are taken, for example, to temporarily reduce the tube current or temporarily increase the distance between the X-ray focal point 21 and the X-ray image intensifier 3 so that the visible light image does not become bright and the imaging element of the camera 44 does not become saturated.

[0050] When the change in focal length is completed, the adjustment mechanism control unit 43a controls the adjustment mechanism 43 to adjust the aperture value of the optical diaphragm 42 (step S04). The adjustment mechanism control unit 43a adjusts the aperture value of the optical diaphragm 42 so that the brightness of the visible light image obtained by changing the input field of view is optimized.

[0051] [1-3. Effects of the embodiment] (1) The X-ray imaging system 100 of this embodiment includes a sample table 1 on which an object to be inspected W is placed, an X-ray generator 2 that irradiates the object to be inspected W with X-rays, an X-ray image intensifier 3 that converts the X-rays into a visible light image, an X-ray image intensifier power supply unit 31 that supplies voltage to the X-ray image intensifier 3, an imaging unit 4 that includes a lens system 41 and a camera 44 and is provided on the output side of the X-ray image intensifier 3 to capture a visible light image, a first adjustment mechanism 43 that changes the imaging magnification of the lens system 41, an X-ray image intensifier control unit 32 that adjusts the applied voltage from the X-ray image intensifier power supply unit 31 to change the input field of view of the X-ray image intensifier 3, and a first adjustment mechanism control unit 43a that controls the first adjustment mechanism 43 to change the imaging magnification of the lens system 41 in accordance with the input field of view.

[0052] In conventional X-ray imaging systems, even if the input field of view of the X-ray image intensifier is changed, the output image from the output phosphor screen is captured by a lens system with a constant imaging magnification. As a result, since the imaging magnification is constant regardless of the input field of view, the spatial resolution of the input field of view may not be reflected in the output image. Therefore, there is a possibility that it may not be possible to meet the demand for observing the details of an inspection object, for example.

[0053] On the other hand, the X-ray imaging system 100 of this embodiment includes a first adjustment mechanism 43 that changes the imaging magnification of the lens system 41. The first adjustment mechanism control unit 43a is configured to change the imaging magnification of the lens system 41 in accordance with the changed input field of view of the X-ray image intensifier 3. Therefore, a visible light image can be captured at an imaging magnification that is optimal for the spatial resolution of each of the multiple input fields of view of the X-ray image intensifier 3. Therefore, it is possible to provide an X-ray imaging system that can reflect the spatial resolution obtained by adjusting the input field of view in the captured image. That is, the accuracy and quality of the captured image can be improved.

[0054] (2) The imaging unit moving mechanism 45 further includes an imaging unit 4 moving mechanism that moves the imaging unit 4 in the X-axis direction, and an imaging unit moving mechanism control unit 45a that controls the imaging unit moving mechanism 45 to move the imaging unit 4 in the X-axis direction and adjust the focal length so that the camera can focus on and capture the visible light image, and the imaging unit moving mechanism control unit 45a is configured to adjust the focal length of the imaging unit 4 after the imaging magnification is adjusted in accordance with the input field of view.

[0055] The X-ray imaging system 100 is configured such that the imaging unit moving mechanism control unit 45a controls the imaging unit moving mechanism 45 to move the imaging unit 4 in the X-axis direction, thereby making it possible to adjust the focal length. Therefore, even if the focal length differs from the previous setting due to a change in the input field of view and imaging magnification, it is possible to adjust the focal position. Even if a lens system 41 without a focal position adjustment function is adopted in the imaging unit 4, it is possible to perform focusing, thereby improving the accuracy and quality of the captured image.

[0056] (3) The imaging unit 4 further includes an optical aperture 42 provided in the lens system 41 and a second adjustment mechanism 43 that adjusts the aperture value of the optical aperture 42, and further includes a second adjustment mechanism control unit 43a that controls the second adjustment mechanism 43 to adjust the aperture value of the optical aperture 42, and the second adjustment mechanism control unit 43a is configured to adjust the aperture value of the optical aperture 42 after the imaging magnification is adjusted in accordance with the input field of view.

[0057] The second adjustment mechanism control unit 43a is configured to control the second adjustment mechanism 43 to adjust the aperture value of the optical aperture 42. Therefore, even if the brightness of the captured image changes due to a change in the input field of view and imaging magnification, the aperture value can be adjusted. Therefore, even if the effective aperture value changes as a result of changing the imaging magnification of the lens system 41, a visible light image can be captured at a constant brightness, thereby improving the accuracy and quality of the captured image.

[0058] (4) The first adjustment mechanism control unit 43a has a storage unit that stores imaging magnifications in association with a predetermined input field of view. By using the imaging magnifications associated with each input field of view stored in the storage unit, it becomes possible to automatically set the imaging magnification without calculating the imaging field ratio.

[0059] (5) The imaging unit movement mechanism control unit 45a has a storage unit that stores focal lengths in association with the predetermined input field of view. By using the focal lengths associated with each input field of view stored in the storage unit, it is possible to automatically set the focal length even when the focal position changes due to a change in the input field of view and imaging magnification. Therefore, even when it is difficult to perform the measurement required for focusing, it is possible to automatically focus.

[0060] (6) The lens system 41 is a macro lens with variable imaging magnification. By using a macro lens, it is possible to handle imaging magnifications of 1 or more, and to obtain a perspective image with a sharpness superior to that of a general lens.

[0061] [2. Second embodiment] In the above-described first embodiment, an example has been described in which a macro lens with a variable imaging magnification is used as the lens system 41. However, as in the second embodiment, a compound lens in a tandem configuration may be used as the lens system 41. The compound lens in a tandem configuration will be described below with reference to FIG.

[0062] The tandem lens assembly includes a primary lens 46a and a secondary lens 46b. The primary lens 46a is a lens arranged on the X-ray image intensifier 3 side in the lens system 41. The secondary lens 46b is a lens arranged on the camera 44 side in the lens system 41. When the primary lens 46a is a fixed-focus lens, the secondary lens 46b uses a zoom lens with a variable imaging magnification. When the primary lens 46a is a zoom lens with a variable imaging magnification, the secondary lens 46b uses a fixed-focus lens. The tandem lens assembly is configured so that the imaging magnification can be changed at least from 1 to 3 times.

[0063] An optical aperture 42a is provided at a predetermined position of the lens group of the primary lens 46a. Similarly, an optical aperture 42a is provided at a predetermined position of the lens group of the secondary lens 46b. The imaging unit 4 further includes an adjustment mechanism 47a that adjusts the imaging magnification of the primary lens 46a and the aperture value of the optical aperture 42a, and an adjustment mechanism 47b that adjusts the imaging magnification of the secondary lens 46b and the aperture value of the optical aperture 42b.

[0064] It can be said that a tandem lens combination is configured to change the imaging magnification by using a zoom lens on one side, and to maintain optical quality by using a fixed focus lens on the other side. By using a tandem lens combination, it is possible to obtain a high-quality output image with reduced image distortion.

[0065] [3. Third embodiment] In the first embodiment, the adjustment mechanism control unit 43a is configured to control the adjustment mechanism 43 using the imaging magnification that is stored in the storage unit and that is associated with the input field of view of the X-ray image intensifier 3. However, the adjustment mechanism control unit 43a may also include an imaging magnification calculation unit that calculates the imaging magnification of the lens system 41 by the following equation 1. The adjustment mechanism control unit 43a controls the adjustment mechanism 43 using the imaging magnification M calculated by the imaging magnification calculation unit. L The adjustment mechanism 43 is controlled so as to obtain the above. (Number 1) M L =(d I / d O )×2R I ×P C

[0066] As shown in FIG. 4, the variables in the above formula 1 have the following meanings. M L : Imaging magnification of lens system 41 d I : Effective diameter of the input phosphor screen of the X-ray image intensifier 3 (input field of view) d O : Diameter of the output phosphor screen of X-ray image intensifier 3 R I: Spatial resolution per diameter of the input phosphor screen of the X-ray image intensifier 3, the unit is Lp / mm, and it represents the number of pairs of black and white that can be resolved per 1 mm of the input phosphor screen. In the case of X-ray images, instead of black and white pairs, it represents a state in which a slit through which X-rays pass and a partition of the same width through which X-rays have difficulty passing are considered as one pair, and it represents a state in which multiple pairs are lined up. P C : Pixel pitch of camera 44

[0067] The imaging magnification calculation unit of the adjustment mechanism control unit 43a may calculate the imaging magnification of the lens system 41 by the following equation 2. (Number 2) M L =(d I / d O )×2R I ×P C ×k

[0068] Here, the coefficient k is a coefficient for adjusting the imaging magnification of the lens, and is preferably set to a value between 1.1 and 1.3. In the above formula 1, depending on the positional relationship between the pixels of the camera 44 and the X-ray image intensifier 3, the spatial resolution per diameter of the input phosphor screen of the X-ray image intensifier 3 and the spatial resolution of the camera 44 may be exactly the same, and the resolution of the X-ray image intensifier 3 may not be fully utilized. In such a case, by setting the coefficient k to a value exceeding 1, the spatial resolution of the camera 44 becomes better than the spatial resolution per diameter of the input phosphor screen of the X-ray image intensifier 3, and it becomes possible to utilize the spatial resolution of each input field of view. On the other hand, the larger k is, the smaller the field of view becomes, which is an adverse effect. Therefore, in order to prevent this adverse effect from becoming excessive, it is preferable to set k to a value between 1.1 and 1.3 as described above.

[0069] [4. Fourth embodiment] In the first embodiment, the imaging unit 4 is moved in the X-axis direction using the imaging unit moving mechanism 45. However, as shown in FIG. 5, the imaging unit moving mechanism may be an imaging unit moving mechanism 48 that moves the imaging unit 4 in the X-, Y-, and Z-axis directions. The Y-axis direction is a direction perpendicular to the optical axis of the X-rays. The Z-axis direction is a height direction perpendicular to both the X-axis and Y-axis directions. An imaging unit moving mechanism control unit 48a is connected to the imaging unit moving mechanism 48.

[0070] The imaging unit moving mechanism control unit 48a controls the imaging unit moving mechanism 48 to move the imaging unit 4 in the X-axis direction to adjust the focal length, and to move the imaging unit 4 in the Y and Z axes to align the center of the output phosphor screen of the X-ray image intensifier 3 with the center of the imaging element of the camera 44. This can be done, for example, by attaching a small marker such as tin foil that is difficult for X-rays to transmit to the center of the input surface of the X-ray image intensifier 3, and moving the camera 44 in the Y and Z axes directions so that it appears in the center of the fluoroscopic image. Note that a mechanism not shown may be further included to enable the imaging unit 4 to perform rolling, yawing and pitching.

[0071] In addition to adjusting the focal length, by aligning the center of the output phosphor screen of the X-ray image intensifier 3 with the center of the image sensor of the camera 44, the light is evenly distributed on the sensor and the reduction in peripheral light intensity is suppressed. Also, image distortion can be minimized. By aligning in three directions of the X, Y, and Z axes, the spatial resolution can be further improved.

[0072] 5. Other embodiments In this specification, several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. The above-mentioned embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and gist of the invention. [Explanation of symbols]

[0073] 100: X-ray imaging system I:Operation unit O:Display part W: Inspection object 1: Sample table 11: Sample table movement mechanism 12: Sample table rotation mechanism 13: Sample table control unit 2: X-ray generator 21:X-ray focus 22: X-ray generator control unit 3: X-ray image intensifier 31: X-ray image intensifier power supply 32: X-ray image intensifier control section 4: Imaging section 41: Lens system 41a: First lens 41b: Second lens 42, 42a, 42b: optical aperture 43, 47a, 47b: Adjustment mechanism 43a: Adjustment mechanism control section 44: Camera 45, 48: Imaging unit movement mechanism 45a, 48a: Imaging unit movement mechanism control unit 46a: Primary lens 46b: Secondary lens

Claims

1. a sample table on which an object to be inspected is placed; an X-ray generator for irradiating the object to be inspected with X-rays; an X-ray image intensifier for converting the X-rays into a visible light image; an X-ray image intensifier power supply unit that supplies a voltage to the X-ray image intensifier; an imaging unit including a lens system and a camera, provided on an output side of the X-ray image intensifier, and configured to capture the visible light image; a first adjustment mechanism for changing an imaging magnification of the lens system; an X-ray image intensifier control unit that adjusts an applied voltage from the X-ray image intensifier power supply unit to change an input field of view of the X-ray image intensifier; a first adjustment mechanism control unit that controls the first adjustment mechanism to change the imaging magnification of the lens system in accordance with the input field of view; An X-ray imaging system comprising:

2. an imaging unit moving mechanism that moves the imaging unit in an X-axis direction; an image capture unit moving mechanism control unit that controls the image capture unit moving mechanism to move the image capture unit in an X-axis direction and adjust a focal length so that the camera can focus on and capture the visible light image, The imaging unit moving mechanism control unit is configured to adjust the focal length of the imaging unit after the imaging magnification is adjusted in accordance with the input field of view.

2. The x-ray imaging system of claim 1.

3. The imaging unit includes: an optical aperture provided in the lens system; and a second adjustment mechanism for adjusting the aperture value of the optical aperture, a second adjustment mechanism control unit that controls the second adjustment mechanism to adjust the aperture value of the optical aperture, the second adjustment mechanism control unit is configured to adjust the aperture value of the optical diaphragm after the imaging magnification is adjusted in accordance with the input field of view.

3. The X-ray imaging system according to claim 1 or 2.

4. 3. The X-ray imaging system according to claim 1, wherein the first adjustment mechanism control unit includes a storage unit that stores the imaging magnification in association with a predetermined input field of view.

5. 3. The X-ray imaging system according to claim 2, wherein the imaging unit moving mechanism control unit has a storage unit that stores the focal length in association with a predetermined input field of view.

6. 3. The X-ray imaging system according to claim 1, wherein the lens system is a macro lens having a variable imaging magnification.

7. 3. The X-ray imaging system according to claim 1, wherein the lens system is a compound lens in a tandem configuration including a zoom lens with a variable imaging magnification and a lens with a fixed focus.

8. The first adjustment mechanism adjusts the imaging magnification to M Ｌ = (d Ｉ / d Ｏ ) x 2R Ｉ ×P Ｃ An imaging magnification calculation unit is provided which calculates the imaging magnification ratio by M Ｌ is the imaging magnification of the lens system, d Ｉ is the input field of view of the X-ray image intensifier, d Ｏ is the diameter of the output phosphor screen of the X-ray image intensifier, R Ｉ is the spatial resolution per diameter of the input phosphor screen of the X-ray image intensifier, P Ｃ is the pixel pitch of the camera, 3. The X-ray imaging system according to claim 1 or 2.

9. The imaging magnification calculation unit calculates the imaging magnification as M Ｌ = (d Ｉ / d Ｏ ) x 2R Ｉ ×P Ｃ × k, k is a coefficient for adjusting the imaging magnification of the lens system; 9. The x-ray imaging system of claim 8.

10. an imaging unit moving mechanism for moving the imaging unit in X, Y, and Z axis directions; an imaging unit moving mechanism control unit that controls the imaging unit moving mechanism to move the imaging unit in the X-axis direction to adjust the focal length, and to move the imaging unit in the Y-axis and Z-axis directions to align the center of the output phosphor screen of the X-ray image intensifier with the center of the imaging element of the camera, The imaging unit moving mechanism control unit is configured to adjust the imaging magnification in accordance with the input field of view, and then adjust the focal length of the imaging unit and perform the alignment.

2. The x-ray imaging system of claim 1.

Images