JPH08240666A - X-ray detection apparatus - Google Patents

Abstract

PURPOSE: To provide an X-ray detection apparatus by which the spatial distribution of X-ray energy can be measured in real time. CONSTITUTION: An X-ray detection apparatus is constituted of an X-ray detection part 1 which detects the spatial distribution of X-rays, of an absorption film 2 whose transmittance depends on X-ray energy in order to adjust the energy distribution of the X-rays to be detected, of a signal processing part 3 which processes a signal detected by the X-ray detection part 1, of a control part 4 which controls the absorption film 2 and the signal processing part 3 and of a monitor 5 which outputs the signal processed by the signal processing part 3. In the signal processing part 3, the difference between the spatial distribution of the intensity of X-rays in a present absorption film and the spatial distribution of the intensity of X-rays in an immediately preceding absorption film is found by means of a control signal 11 from the control part 4. An output result from the signal processing part 3 is observed by the monitor 5, and the spatial distribution of the X-ray energy corresponding to the difference in a transmittance between the two absorption films is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray detecting apparatus for detecting X-rays, and more particularly to an X-ray detecting apparatus suitable for measuring a spatial distribution of irradiated X-ray energy.

[0002]

2. Description of the Related Art In conventional X-ray detectors, when measuring the intensity distribution of X-rays, a plurality of X-ray detectors that output a signal intensity proportional to the energy of X-rays are installed to detect individual X-rays. The energy distribution was measured by measuring the signal intensity of the instrument output value, and the X-ray energy spatial distribution was obtained by performing similar signal processing on each X-ray detector. Therefore, the signal processing of the X-ray detector becomes complicated, and there is a problem that it cannot be dealt with when the X-ray energy distribution changes with time, particularly when it changes with time.

Further, an absorption film whose X-ray absorption rate is known is installed on the front surface of the X-ray detector, several absorption films are prepared, and the X-ray energy distribution is measured by exchanging the absorption films. In this method, when measuring the spatial distribution of X-rays, the signal processing of the X-ray detectors is required because the number of X-ray detectors is the same as that of the X-ray detectors. Further, there is a problem that high-speed signal processing is required when the energy distribution of the X-ray changes with time, particularly when it changes with time.

A conventional X-ray detecting apparatus using an X-ray detector for detecting a two-dimensional distribution of X-rays is disclosed in Japanese Patent Laid-Open No.
No. 2 of X-rays that have passed through the sample as described in JP-A-210651.
There is an X-ray detection device that measures a three-dimensional image. In this conventional technique, X-rays that have passed through a sample are converted into light, detected by an image pickup tube such as an image intensifier, and stored in an image memory. The structure is such that the optimum sample position is detected from the detected X-ray image, and adjustments such as positioning are performed so as to set the optimum sample position. In this method, when a plurality of materials are used in the sample, in order to accurately detect the position of the sample, it is necessary to use X-rays having energy that does not pass through all the materials used. Therefore, it is necessary to adjust the X-ray energy every time the material in the sample changes. Also, to obtain the set position for each material,
If there are multiple intensities of X-ray transmission, there is a problem in determining the correct sample position.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an X-ray detector capable of measuring the spatial distribution of X-ray energy in real time.

[0006]

In order to achieve the above object, the present invention provides an absorption film for absorbing X-rays, and an X-ray absorption film for the absorption film.
Control means for controlling the line absorption characteristics, a detector for detecting the X-rays that have passed through the absorption film, and signal processing means for obtaining the spatial distribution of the X-ray energy by using the detection signal of the X-rays by the detector. Prepare

[0007]

The operation of the present invention will be described with reference to FIG. Figure 2
Is a calculation of the transmittance of the absorption film for X-ray energy with the thickness of the absorption film as a parameter when a beryllium film is installed as the X-ray absorption film on the front surface of the X-ray detector.

When the thickness of the absorption film is known in advance, the X-ray transmission rate of the absorption film is given by the equation 1.

[0009]

## EQU00001 ## T (E) = exp {-. Mu. (E) D} (Equation 1) where T (E) is the passage rate of X-rays having energy E,
μ is the total absorption coefficient of the absorption film, and D is the thickness of the absorption film.

When the difference between the case where the film thickness D of the absorbing film is 100 μm and the case where D is 1000 μm is obtained, the energy distribution at the portion “A” shown in FIG. 2 is obtained. Similarly, when the difference between the case where the thickness D of the absorption film is set to 1000 μm and the case where D is 5000 μm is obtained, the energy distribution in the portion “B” shown in FIG. 2 is obtained.

Similarly, the X-ray energy distribution can be measured by changing the film thickness D of the absorption film one after another, and further, by adjusting the film thickness of the absorption film in accordance with the X-ray energy to be measured, it is necessary. The energy distribution of various X-rays can be measured in real time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the X-ray detector according to the present invention will be described below with reference to FIG. The present X-ray detection apparatus includes an X-ray detection unit 1 that detects a spatial distribution of X-rays, an absorption film 2 that has a transmittance that depends on X-ray energy for adjusting the energy distribution of the detected X-rays, and an X-ray detection unit. The signal processing unit 3 processes the signal detected by the line detection unit 1, the control unit 4 controls the absorption film 2 and the signal processing unit 3, and the monitor 5 outputs the signal processed by the signal processing unit 3. .

The X-ray detection unit 1 converts the incident X-rays into light, a microchannel plate 6, a high-voltage power supply 7 for supplying a voltage to the microchannel plate 6, and a CC for measuring the light converted by the microchannel plate 6.
It is composed of a D camera 8 and a CCD driver 9 for driving the CCD camera 8. The X-rays that enter the X-ray detector become X-rays that pass with a pass rate that has the energy dependence of the X-rays that is determined by the characteristics of the absorption film 2 defined by the control signal 10 from the control unit 4. In the X-ray detector, light proportional to the incident X-ray is emitted from the microchannel plate 6, and this light is measured by the CCD camera 8. Therefore, the light measured by the CCD camera 8 has an amount proportional to the X-ray intensity. C
Using the spatial distribution of X-ray intensity measured by the CD camera 8,
The signal processing unit 3 obtains an X-ray energy distribution. At this time, the signal processing unit 3 obtains the difference between the spatial distribution of the X-ray intensity at the current absorption film and the spatial distribution of the X-ray intensity at the immediately previous absorption film by the control signal 11 from the control unit 4. . By observing the output result of the signal processing unit 3 on the monitor 5, the spatial distribution of the X-ray energy corresponding to the difference in the transmittance between the two absorption films is measured.

According to this embodiment, it is possible to measure the spatial distribution of X-ray energy within the total time of exchanging the absorption film and the time required for signal processing.

An embodiment of the signal processing unit 3 is shown in FIG. X
The X-ray intensity spatial distribution detected by the line detection unit 1 is converted by the A / D conversion unit 12 and then divided into two. One of the divided signals 16a is directly input to the subtraction unit 14, and the other signal 16a is input.
b is input to the subtraction unit 14 as a signal 17 having a predetermined time delay with respect to the signal 16a by the delay unit 13. The subtraction unit 14 finds the difference between the signals of 16a and 17 and calculates the D / A
The conversion unit 15 outputs the X-ray intensity spatial distribution with a specific energy distribution. Here, the delay unit 13 sets the delay time to be set by the control signal 11 from the control unit 4.

The method of setting the delay time in the delay unit 13 is shown in FIG.
Will be explained. Figure 4 shows the A / D signal from the CCD.
After conversion, the state of being divided into two is shown. The smallest box shown in FIG. 4 represents the data for each pixel from the CCD.
That is, assuming that the number of pixels of the CCD is N and the retention time of one data is T, the product of the two represents the spatial distribution of the X-ray intensity measured by one absorption film. Therefore, if the delay time is set to be N × T, CCD signals A and C are set.
When the difference from the CD signal B is calculated, CC measured at the same place
The difference in D output can be calculated.

According to this method, the subtraction unit 14 that sequentially calculates
Can output the difference between the current spatial distribution of the X-ray intensity and the spatial distribution of the X-ray intensity at the absorption film set immediately before.

Next, an embodiment of the absorption film will be described with reference to FIG. Two or more absorption films (2a, 2b, 2c) are attached on the absorption film stay 20, and the absorption film stay 20 has a structure in which the rotation driving unit 18 rotates about a rotation shaft 21. On the other hand, the rotation drive unit 18 has a structure that controls the rotation amount by the control signal 10 from the control unit 4. The X-rays applied to the absorption film are made to pass through only one absorption film by the collimator 19. According to this structure, the control signal 10 of the control unit 4 can control the X-ray passing through the absorption film. Therefore, as the control signal 10 from the control unit 4, the time for changing the film from one absorption film to the next absorption film is controlled to be equal to the delay time of the signal processing unit 3.

According to this embodiment, the spatial distribution of the energy distribution of the X-ray to be measured can be measured every time the absorbing film is changed.

[0020]

According to the present invention, the spatial distribution of the X-ray energy distribution can be measured in substantially real time by adjusting the changing time of the absorption film and the time required for signal processing.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an X-ray detection device according to the present invention.

FIG. 2 is a diagram showing the X-ray energy dependence of the X-ray transmittance of the absorption film.

FIG. 3 is a diagram showing an embodiment of the signal processing unit of FIG.

FIG. 4 is an explanatory diagram of a delay time setting method in the delay unit of FIG.

FIG. 5 is a diagram showing an embodiment of the absorption film of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... X-ray detection part, 2 ... Absorption film, 3 ... Signal processing part, 4 ... Control part, 5 ... Monitor, 6 ... Microchannel plate,
7 ... High-voltage power supply, 8 ... CCD camera, 9 ... CCD driver, 12 ... A / D conversion section, 13 ... Delay section, 14 ... Subtraction section, 15 ... D / A conversion section, 18 ... Rotation drive section, 19 ... Collimator, 20 ... Absorption film stay.

Claims (3)

[Claims] 1. An absorption film that absorbs X-rays, a control means that controls the X-ray absorption characteristics of the absorption film, a detector that detects X-rays that have passed through the absorption film, and an X-ray by the detector. And a signal processing means for obtaining a spatial distribution of X-ray energy by using the detection signal of 1. 2. The X-ray detection apparatus according to claim 1, wherein the signal processing by the signal processing means and the control by the control means are performed in synchronization with each other. 3. The signal processing means according to claim 1,
An X-ray detection device, wherein a spatial distribution of X-ray energy is obtained from a difference between an X-ray detection signal from the detector and a signal obtained by delaying the detection signal by a predetermined time.