JPH02267894A - Focus compensation device for x-ray generator - Google Patents

Abstract

PURPOSE:To maintain an optimum focus condition at all times by detecting fluctuation in the focus of X-ray for controlling an X-ray generator according to the fluctuation therein, thereby compensating the focus thereof. CONSTITUTION:An X-ray generated form an X-ray generator 1 passes through a reference member 11 for observing the focus of X-ray arranged in an X-ray passage 11a for observing the same to make the image of the member 11 on an X-ray image taking part 13. The electric signal of the image thereof is supplied to a focus condition discriminator 15 and process judged, and based on the result, the focus 1a of the generator 1 is controlled by a controller 7 to be in a specified condition. By controlling the generator 1 and a high voltage generator 9 by this controller 7, the condition of focus 1a can be maintained to be a specified reference condition without being dependent on manual operation at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a focus correction device for an X-ray generator that controls the state of the focus of the X-ray generator.

(Prior art) In general, a microfocus X-ray generator, called a microfocus X-ray generator, has an extremely small focal point of several micrometers to several tens of micrometers, and the magnification during imaging is large. However, because the blur of the photographed image due to the size of the focal point is small, it is becoming widely used for X-ray inspection of fine structures.

Similar to conventional X-ray generators, this type of X-ray generator uses a method in which electron beams are focused and hit a target made of tungsten, etc., and X-rays are generated from there by bremsstrahlung radiation. Equation % Therefore, the focal state such as the position, size and shape of the X-ray focal point of the X-ray generator is determined by the position, size and shape of the part where the electron beam hits the target, and the fine focus X-ray In the generator, since the size of the focal point itself is small,
Temporal and spatial variations in the path and diameter of the electron beam cannot be ignored, and in most microfocus X-ray generators, the state of the focus changes even if the X-ray tube voltage or current is changed. It has the following characteristics and has means for manually or automatically controlling the position or size of the focal point. however,
These methods only try to adjust the focus state to a preset value, and do not monitor the actual focus state from the outside. It is necessary to make fine adjustments manually each time depending on the usage conditions of the line generator. Furthermore, conventionally, feedback control in real time by controlling the state of the focal point of the X-rays output from the X-ray generator has not been implemented.

(Problems to be Solved by the Invention) As mentioned above, because the focus of the microfocus X-ray generator is small, the anode loss, which is the product of the tube voltage and the tube current, is about several + W, which is different from that of a general X-ray generator. Since the amount of X-rays generated per unit time is extremely small, about 1/10 to 1/30 of that, the amount of X-rays generated per unit time is also reduced by the same ratio. Therefore, when applied to an industrial XIICT scan, - the cross-sectional imaging time is
This corresponds to 10 to 30 times more than when using a.
For example, in the second generation industrial XIICT scanner, approximately 2
This requires a long time of about 0 to 60 minutes, and there is a problem that the focal state becomes increasingly unstable.

In addition, with industrial CT scanners, there is no way to observe the focus state in real time during imaging, and even if the focus state is optimally adjusted just before the prefecture shadow, it is impossible to compensate for fluctuations during imaging. There's a problem.

The present invention has been made in view of the above, and its purpose is to control the focus state of an X-ray generator in real time, and to constantly maintain an optimal focus state.
An object of the present invention is to provide a focus correction device for a line generator.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the focus correction device for an X-ray generator of the present invention corrects the state of the focus of the X-rays output from the X-ray generator. Provides observable images x1! a reference means for focus observation; a Wi image stage that receives X-rays from the X-ray generator passing through the reference means and captures an image of the reference means;
a detection means for detecting a change in the focus of the X-rays from the X-ray generator by comparing an image of the reference means taken by the imaging means with predetermined reference image information; The present invention further comprises a control means for controlling the X-ray generator so as to correct the focus of the X-ray in accordance with a change in the focus.

(Function) The focus correction device for an X-ray generator of the present invention compares the i-image of the reference means for X-ray focus observation with predetermined reference image information to detect a change in the focus of X-rays, and The X-ray generator is controlled according to changes in the focus of the X-ray, and the focus of the X-rays is corrected.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of a focus correction device for an X-ray generator according to an embodiment of the present invention. In the same figure, 1 is the minute focus
ray generator, 1a is the focal point of the X-ray generator 1, 3 is the object to be inspected whose internal state is to be inspected, 5 is Xll1 on which the image of the object 3 to be inspected is reflected by the X-rays output from the X-ray generator 1; .1. XI!, which consists of a real-time Ill image system such as or a latent image carrier system such as an X-ray film, etc. An imaging unit 7 is an X-ray controller having a function of setting and controlling X-ray generation conditions such as tube voltage and tube current of the X-ray generator 1 and setting and controlling the focal state of the X-ray generator 1; is a high voltage generator that supplies the X-ray generator 1 with a high voltage for generating X-rays.

Further, reference numeral 11 is supported by the same pedestal as the X-ray generator 1, and a focal point 1a of the X-rays output from the X-ray generator 1.
An X-ray focal point observation reference object 13 that provides an image that allows observation of the state of the , X-ray generation! ! ! 1.

15 processes and determines the electric signal of the image of the reference object 11 for X-ray focal point observation outputted from the X-ray carrier 13, and controls the XPJ controller 7 in the field so that the state of the focal point 1a becomes optimal. A focus state determiner that outputs a control signal for back control; 3a is an X-ray path for inspecting an object to be inspected; 11a
is the X-ray path for X-ray focus observation.

In the device configured as described above, the X-rays generated from the X-ray generator 1 pass through the object 3 to be inspected, form an image of the object 3 on the X-ray image section 5, and at the same time The X-rays generated from the generator 1 pass through the inspection object 3 through an X-ray focus observation X-ray path 11a provided in an X-ray focus observation X-ray path 11a that is separate from the inspection object inspection X-ray path 3a. Reference object 11
, and an image of the reference object 11 for X-ray focus observation is captured on the X-ray imaging section 13 .

Here, if even one change in the state of the focal point 1a of the X-ray generator 1, that is, the position, size, shape, etc. of the focal point 1a, the X-ray focal point observation reference object 1 imaged by the X-ray imaging unit 13 changes.
Image 1 also changes. Therefore, the state of the focal point 1a of the XII generator 1 can be determined by processing the image of the X-ray focal point 12 measuring reference object 11 taken by the X-ray imaging section 13. Therefore, X imaged by Wi in this xtam image section 13
Supplying the electrical signal of the image of the line focus observation reference object 11 to the focus state determiner 15, processing and determining it in the focus state determiner 15,
Based on this determination result, the X-ray controller 7 is controlled so that the focal point 1a of the X-ray generator 1 is in a predetermined reference state, and the
X-ray generator 1 and high voltage generator 9 by line controller 7
By controlling this, the constantly changing state of the focal point 1a can be corrected and controlled in real time, and the state of the focal point 1a can always be maintained at a predetermined reference state without manual intervention.

FIG. 2 is a block diagram of another embodiment of the present invention.

In this figure, the same components as in FIG. 1 are given the same reference numerals.

The focus correction device of the X-ray generator shown in Fig. 2 is an industrial Xl
It is applied to the 11CT scanner and is the third generation. In the figure, X-rays output from an X-ray generator 1 pass through a collimator 23 to pass through an object 3 placed on a sample stage 25, and then pass through a collimator 21 to transmit multichannel X-rays. It is detected by the detector 50. The multi-channel X-ray detector 50 separates the image of the object 3 to be inspected in a spatially divided state and detects C1 and supplies the detected image of the object 3 to data collection@M31.

The data acquisition device 31 performs processing such as integration, sample hold, multiplexing, and A/D conversion on the electrical signal of the X-rays detected by the multi-channel X-ray detector 50, and supplies the processed signal to the computer 33 as a digital signal. . Calculation 113
3 reconstructs a tomographic image of the inspected object 3 from the image data of the inspected object 3 collected from the data collection device 31, and displays the tomographic image on the image display device 35. The sample stage 25 is used to rotate the object 3 to be inspected, thereby irradiating the object 3 with Xa from the entire circumference.

The collimators 21 and 23 collimate the X-rays from the X-ray generator 1 to a desired thickness.

On the other hand, the X-rays from the X-ray generator 1 are transmitted to the reference object 10 for X-ray focus observation provided in the X-ray path 11a for X-ray focus observation.
irradiate. The reference object 10 for X-ray focus observation is, for example, 10
0 μl straight platinum wires are orthogonally crossed in a cross shape, and the installation direction thereof coincides with the direction in which the focal point of the X-ray generator 1 can be moved.

A transmission image of xta generated from the X-ray generator 1 through the reference object 10 for X-ray focus observation is captured by the X-ray vidicon 27. X for X-ray focus observation of X-rays imaged by this X-ray vidicon 27
Ray path 11a and the multi-channel X-ray detection P! A scattered ray shielding plate 29a is provided between the X-ray path 3a for inspecting the object to be inspected and the X-ray imaged at A50.

29b is provided to prevent X-rays outside the desired range from being scattered and incident. The image signal of the reference object 10 for X-ray focus observation taken by the X-ray vidicon 27 is supplied to the focus state determiner 15, where it is processed and determined, and the focus 1a of the X-ray generator 1 is placed in a predetermined reference state based on the result of this determination. Yoni X II
The X-ray controller 7 controls the X-ray generator 1 and the high voltage generator 9.

Also, the device shown in Figure 2 is a system control device that commands and controls data collection tamping! 37, the calculation 1133 is controlled by the system 11 control device 137, and the mechanical control device 39 is controlled by the system 11 control device 137.
This controls the rotation of the sample stage 25.

Next, the automatic X-ray focus correction function of the focus correction device of the present X-ray generator will be explained with reference to FIGS. 3 and 4.

An image of the reference object 10 for X-ray focus observation by X-rays generated from the focal point 1a of the X-ray generator 1 is projected onto the entrance surface 27a of the X-ray vidicon 27, as shown in FIG. Here, when the position of the focal point 1a changes, the position of the image on the entrance surface of the X-ray vidicon 27 moves in the opposite direction to the moving direction of the focal point 1a. That is, if the direction parallel to one platinum wire of the Xli focus observation reference object 10 is X, and the direction parallel to the other platinum wire perpendicular to this direction is y (in this case, × and ■ are the positions of the focal point 1a). (Assume that the directions in which adjustment is possible are also the same), the focal point 1a is 1α, as shown in Fig. 3,
When moving in the directions of 1β, 1γ, and 1δ, the images on the incident plane of the X-ray vidicon 27 become 27α, 27β, and 27γ, respectively.
, 27δ. Therefore, by fixing the relative positional relationship between the X-ray generator 1°, the reference object 10 for X-ray focus observation, and the X-ray vidicon 27, the focal point 1
The movement of a can be observed on the incident surface of the X-ray vidicon 27.

In addition, even if the position of the focal point 1a remains unchanged, if the size changes,
As shown in FIG. 4, since the state of the X-ray intensity distribution on the entrance surface of the X-ray vidicon 27 changes, fluctuations in the focal spot size can be observed on the entrance surface of the X-ray vidicon 27. . In FIG. 4, 278' is the X-ray intensity distribution on the incident surface of the X-ray vidicon 27 when the focal spot size is optimal, and 27a'' is the X-ray intensity distribution when the focal spot size changes greatly.
This is the X-ray intensity distribution on the incident surface of the ray vidicon 27.

Furthermore, even if the shape of the focal point 1a changes, the change can be observed using the same principle as shown in FIG.

As explained above, when the position, size, and shape of the focal point 1a change, the change appears as an image on the incident surface of the X-ray vidicon 27, so the X-ray vidicon 27 converts it into an electrical signal and converts it into an electric signal. The state of the focal point 1a can be determined by supplying the information to the state determining device 15 and comparing it with image information stored in advance and captured in an optimal state in the focus state determining device 15. Then, a control signal is supplied to the X-ray controller 7 so that the state of the determined focal point 1a becomes the same as the optimal state, and X-rays are generated via the xm controller 7 and the high voltage generator 9. Control device 1.

The X-ray generator 1 has an internal function that can control the path and focusing state of the electron beam. That is, a plurality of deflection coils and steering coils are provided around the path of the electron beam in the focal point 1a, and by changing the current flowing through these coils, x! 1 The path and focusing state of the electron beam within the generator 1 can be varied. Therefore, the focus state determiner 15 supplies the result of determining the difference between the focus state and the optimal state to the X-ray controller 7, and the X-ray controller 7 sends a control signal to the X-ray generator 1 so that the focus state is in the optimal state. If supplied, the state of the focal point 1a of the X-ray generator 1 can always be controlled to the optimum state.

In addition, the signal from the X-ray vidicon 27 is transmitted to the data acquisition device 3.
1, and is used as X-ray intensity fluctuation correction data for each unit acquisition time. That is, the X-ray vidicon 27 also has the function of a comparison detector for collecting X-rays that do not pass through the inspection object 3 and correcting the X-ray intensity from the source of the X-rays.

As described above, the focus 1a, the reference object 10 for X-ray focus observation,
A focus state observation system consisting of the X-ray vidicon 27 and the focus state determiner 15 stores an image in the optimal state of focus, and then the image information sequentially supplied from the X-ray vidicon 27 to the focus state determiner 15 is used to determine the optimal state of the focus. By comparing the image information at the time of the state and supplying a command signal from the focus state determiner 15 to the X-ray controller 7 to correct the change in the state of the focus, the change in the state of the focus is corrected. Optimal conditions can be maintained automatically.

Therefore, it is possible to prevent blurring of reconstructed images, generation of false images, etc. due to errors in acquired data due to changes in the state of focus, which are problems in, for example, X-ray CT scanners.

Furthermore, the X-ray vidicon 27 can also serve as a comparison detector b1 for obtaining reference data for correcting the intensity of X-rays from the X-ray generator 1. Furthermore, it is possible to prevent the electron beam from being focused more than a predetermined value due to temporal fluctuations and from melting the focal point due to heat concentration.

In addition, in the above embodiment, the reference object 1 for X-ray focus observation
Although a platinum wire orthogonally crossed in a cross shape is used as the zero, the present invention is not limited to this, and for example, a pinhole may be used. When a pinhole is used, the linear state parallel to the x and y directions described above becomes unnecessary, and the portion corresponding to the XII focus observation reference object 10 can be simplified. Furthermore, in the above embodiment, the X-ray vidicon 27 and the multi-channel X-ray detector 50 are provided separately, but by forming the multi-channel X-ray detector 50 large, the multi-channel X-ray detector 50 can perform The line vidicon 27 can also be used.

[Effects of the Invention] As explained above, according to the present invention, the captured image of the reference means for X-ray focus observation is compared with predetermined reference image information, and the
Changes in the focus of the X-ray are detected, the X-ray generator is controlled according to the change in the focus of the X-ray, and the focus of the X-ray is corrected, so the state of the focus of the X-ray generator is always kept as desired. It can be used stably for a long time in a preset optimal condition. Therefore, the fine focus X-ray generator can be effectively used in the most effective state even in, for example, an X-ray CT scanner where fluctuations in the state of focus are a particular problem. In addition, there is a certain relationship between the size of the focal point and the anode loss in the 8-position micro-focus X-ray generator, and if the size of the focal point is reduced below a certain value under a certain anode loss, the focal point will dissolve due to heat concentration. However, by applying the focus correction device for the X-ray generator of the present invention, it is possible to prevent the focus from becoming smaller.
The life of the focus can be extended.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a focus correction device for an X-ray generator according to an embodiment of the present invention, FIG. 2 is a block diagram of another embodiment of the present invention, and FIGS. FIG. 2 is a partially enlarged view of a main part of the embodiment. 1...X-ray generator 1a...Focus 3...Object to be inspected 5...X-ray image section 7...X-ray controller 9...High voltage generator 11...X-ray Focus observation reference object 13...Xla imaging unit 15...Focus state determiner. Figure 1

Claims (1)

[Claims] X-ray focus observation reference means for providing an image that allows observation of the state of the focus of X-rays output from the X-ray generator; an imaging means for receiving the radiation and taking an image of the reference means, and an image of the reference means for X-ray focus observation taken by the imaging means is compared with predetermined reference image information to detect the X-ray from the X-ray generator. The apparatus comprises a detection means for detecting a change in the focus of the X-ray, and a control means for controlling the X-ray generator so as to correct the focus of the X-ray in accordance with the change in the focus of the X-ray detected by the detection means. A focus correction device for an X-ray generator, characterized by: