GB2127538A

GB2127538A - X-ray device

Info

Publication number: GB2127538A
Application number: GB8323706A
Authority: GB
Inventors: Toshiyuki Koga
Original assignee: Seiko Instruments Inc
Current assignee: Seiko Instruments Inc
Priority date: 1982-09-24
Filing date: 1983-09-05
Publication date: 1984-04-11
Also published as: FR2533794B1; NL8302740A; GB2127538B; GB8323706D0; JPS5967449A; DE3334458A1; FR2533794A1; JPS6259258B2

Abstract

An X-ray device comprising an X- ray tube (1); a shutter (9) which is movable between an open position (not shown) in which X-rays from the X-ray tube (1) may be directed onto material (8) to be tested and a closed position (shown in Figure 1) in which the said X-rays are prevented from being so directed; an X-ray detector (4) for detecting fluorescent X-rays emitted by said material (8) when the shutter (9) is open; means (2) movable with the shutter (9) for receiving X- rays from the X-ray tube (1) and for directing fluorescent X-rays onto the X-ray detector (4) when the shutter (9) is closed; and correction means (11-14) connected to said X-ray detector (4) for automatically correcting a change in the X-rays produced by the X-ray tube (1). <IMAGE>

Description

SPECIFICATION X-ray device This invention concerns an X-ray device provided with means for automatically correcting a change (e.g. in the intensity and/or in the wave height) in the X-rays produced by the X-ray device.

In our co-pending British Patent Application No.

8,315,135 we have disclosed an X-ray device in which the required correction is effected by comparing fluorescent X-rays emitted from a correction standard plate when a shutter of the Xray device is closed with fluorescent X-rays emitted from sample material when the shutter is open. However, a predetermined length of time has to elapse during which the fluorescent X-rays emitted by the correction standard plate are detected if true values for the intensity and wave height of these fluorescent X-rays are to be obtained. Moreover, it has been necessary to correct the X-ray device for any fluctuation in the X-rays produced thereby before it was possible to determine the value of a property of the sample material, such as the thickness of a surface layer thereof.

Although, therefore the present invention is primarily directed to any novel integer or step, or combination of integers or steps, as herein described and/or as shown in the accompanying drawings, nevertheless, according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided an X-ray device comprising an X-ray tube; a shutter which is movable between an open position in which Xrays from the X-ray tube may be directed onto material to be tested and a closed position in which the said X-rays are prevented from being so directed; an X-ray detector for detecting fluorescent X-rays emitted by said material when the shutter is open; means movable with the shutter for receiving X-rays from the X-ray tube and for directing fluorescent X-rays onto the X-ray detector when the shutter is closed; and correction means, including a memory, connected to said X-ray detector for automatically correcting a change in the X-rays produced by the X-ray tube when there is a predetermined difference between the fluorescent X-rays which are received by the X-ray detector from the material and those which are received by the X-ray detector from the means movable with the shutter.

Preferably the means movable with theshutter is a correction standard plate carried by the shutter.

The correction means are preferably arranged to compare first data which relate to the fluorescent X-rays emitted by the said material with second data which relate to the fluorescent X-rays emitted by the said means movable with the shutter, the second data having been previously stored in the said memory. Thus there may be means for periodically storing the second data in the memory at predetermined intervals.

Moreover, there may be means for averaging the second data which are stored in the memory at the said predetermined intervals.

The X-ray tube preferably has a collimator for collimating the X-rays from the X-ray tube. Thus the collimator may have a first passage therein which is arranged to receive X-rays from the X-ray tube, and second and third passages therein which can communicate with the first passage, the second passage being arranged to direct X-rays from the said first passage onto the X-ray detector only when the shutter is closed, and the third passage being arranged to direct X-rays from the said first passage onto the material only when the shutter is open.

There may be an indicator or control means, controlled by the X-ray detector, for indicating the value of a property of said material or for exercising a control in dependence on said value.

The correction means may comprise a wave height analyser and a scaler timer.

Preferably, the correction means is controlled by a position sensor which senses the position of the shutter.

The invention also comprises a method of correcting said X-ray device, said method comprising storing the second data in the memory and comparing the first data with the previously stored second data. In this case, the means movable with the shutter may be similar in composition and construction to that of the said material.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which Figure 1 is a diagrammatic view of an X-ray device according to the present invention, Figure 2 is a diagrammatic view of the X-ray device shown in Figure 1, the view of Figure 2 being at right angles to that of Figure 1, and Figure 3 is a block diagram of the X-ray device of Figures 1 and 2.

As shown in Figures 1 and 2, an X-ray device according to the present invention comprises an ray tube 1 and a shutter 9. The shutter 9 is movable between an open position (not shown), in which X-rays from the X-ray tube 1 may be directed onto a sample material 8 to be tested, and a closed position (shown in Figure 1) in which the X-rays from the X-ray tube 1 are prevented from being so directed. The X-ray tube 1 has a collimator I a for collimating the X-rays from the X-ray tube 1. The collimator 1 a has a first guide passage 6 therein which is arranged to receive Xrays from the X-ray tube 1 and to collimate the Xrays because of its large diameter, and second and third guide passages 3, 7 therein which can communicate with the first passage 6.Mounted on the shutter 9 and carried thereby so as to be movable therewith is a correction standard plate 2 which may be a thin gold plate or may be similar in composition and construction to that of the sample material 8. Thus if the sample material 8 is intended to be provided with a layer of a specific material having a specific thickness, the correction standard plate 2 is similarly provided with such a layer.

When the correction standard plate 2 is in the position shown in Figure 1 and is thus in the position in which the shutter 9 is closed, X-rays which are directed through the first guide passage onto the correction standard plate 2 will produce fluorescent X-rays which will be directed through the second guide passage 3 and through an opening 5a onto an X-ray detector 4 which may comprise a proportional counter or other detecting device.

The third guide passage 7 is arranged to direct X-rays from the first guide passage 6 onto the sample material 8 only when the shutter 9 is open.

That is to say, the first passage 6 and the third passage 7 communicate with each other only when the shutter 9 is open, these passages being out of communication with each other when the shutter 9 is closed. Fluorescent X-rays produced by the sample material 8 are directed onto the Xray detector 4 by way of an opening 5a therein.

The X-ray detector 4, which is thus responsive to the fluorescent X-rays produced by the sample material 8, produces signals related to these fluorescent X-rays, and means (not shown) are provided which are responsive to these signals for indicating the value of a property of the sample material 8 (e.g. the thickness of a surface layer thereon) or for exercising a control (e.g. the control of the thickness of said layer) in dependence upon said value.

As shown in Figure 3, the X-ray detector 4 is connected to and passes electrical signals to a wave height analyser 11. The output of the wave height analyser 11 is counted buy a scalertimer 12 and is passed to an X-ray automatic correction means 13 which is arranged to correct the X-ray tube 1 automatically when there is a variation in the X-rays produced by the X-ray tube 1, e.g.

when there is a variation in the wave height and/or intensity of the X-rays. The output from the scaler timer 12 is also passed to a memory 14 which is connected to the X-ray automatic correction means 13. A position sensor 10 is provided which senses the position of the shutter 9 and ensures that the correction in the X-rays produced by the X-ray tube 1 occurs only at a time when the shutter 9 is closed.

The arrangement may be desired be such that the fluorescent X-rays which are received by the X-ray detector 4 from the sample material 8 are compared with those which are received from the correction standard plate 2, the X-ray automatic correction means 1 3 being required to correct the X-ray tube 1 only when there is a predetermined difference between the two lots of fluorescent Xrays.

Thus in the case of the embodiment of the present invention shown in Figures 1 and 2, the Xrays from the X-ray tube 1 are directed onto the correction standard plate 2 by way of the first guide passage 6 only while the shutter 9 is closed.

When, however, the correction standard plate 2 is moved together with the shutter 9 to the open position of the latter, in which it is spaced from the axis of the X-ray tube 1, then since the third guide passage 7 is positioned over the sample material 8 and since the shutter 9 is moved from the position shown in Figure 1, X-rays are directed onto the sample material 8.

Since the position of the shutter 9 is detected by the position sensor 10, the X-ray device is maintained in a correction mode only while the shutter 9 is closed.

Since the corrected X-rays are transmitted to the X-ray detector 4 only during the time that the shutter 9 is closed, the corrected X-rays do not affect a measuring operation on the sample material 8.

In operation, the shutter 9 is first opened so as to direct the X-rays onto the sample material 8.

The open position of the shutter 9 is sensed by the position sensor 10 and data concerning the intensity and the wave height of the fluorescent Xrays from the sample material is stored in the memory 14. The shutter 9 is now closed and the correction means 1 3 is so formed that the data concerning the fluorescent X-rays emitted from the sample material 8 which has been so stored in the memory 14 is compared with the data concerning the intensity and the wave height of the fluorescent X-rays from the correction standard plate 2 which has been previously stored in the memory 14. If there is a predetermined difference between the two lots of data, the X-ray automatic correction means 13 effects correction of the X-ray tube 1, whereby to restore the intensity and/or the wave height of the X-rays from the tube 1 to a predetermined value.At the same time, the data concerning the fluorescent Xrays from the sample material 8 are evaluated (by means not shown) so as to indicate the value of a property of the sample material 8 (e.g. the thickness of a surface layer thereon).

During the time that the shutter 9 is closed, the correction standard plate 2 will be irradiated with X-rays from the X-ray tube 1 and will itself produce fluorescent X-rays. These fluorescent Xrays from the correction standard plate 2 are directed onto the X-ray detector 4 and their intensity and wave height are evaluated at regular intervals, e.g. of one second, there being means (not shown) such that data relating to the said intensity and wave height are stored in the memory 14 for subsequent comparison with the data relating to the fluorescent X-rays from the sample material 8. Consequently, the measurement of the sample material 8 does not need to be held up, as has previously been the case, until a sufficient length of time has elapsed to establish the average value of the intensity and wave height of the fluorescent X-rays from the correction standard plate 2 and until a separate correction step for correcting the X-ray tube 1 has been carried out. In the case of the present invention, the correction of the X-ray tube 1 can be effected immediately at any time when the sample material 8 is not being measured so that the measurement of the sample material 8 is not held up even though the time required for effecting a correction of the X-ray tube 1 amounts to the total time required to obtain data concerning the fluorescent X-rays produced by the correction standard plate 2 and by the sample material 8.

If, for example, the time for which it is necessary to measure the fluorescent X-rays emitted from the correction standard plate 2 in order to obtain a correct measurement is Tseconds, this measurement can be effected by taking the instantaneous measurement of the fluorescent X-rays emitted from the correction standard plate 2 every second, storing these measurements in the memory 14, and obtaining an average value of these measurements during the T-seconds. For example, means (not shown) may be provided for obtaining a running average value of these measurements, which average value is continuously being corrected and which is not cleared from the memory 14 when the data relating to the fluorescent X-rays from the sample material 8 is cleared therefrom.

Claims

1. An X-ray device comprising an X-ray tube, a shutter which is movable between an open position in which X-rays from the X-ray tube may be directed onto material to be tested and a closed position in which the said X-rays are prevented from being so directed; an X-ray detector for detecting fluorescent X-rays emitted by said material when the shutter is open; means movable with the shutter for receiving X-rays from the Xray tube and for directing fluorescent X-rays onto the X-ray detector when the shutter is closed; and correction means, including a memory, connected to said X-ray detector for automatically correcting a change in the X-rays produced by the X-ray tube when there is a predetermined difference between the fluorescent X-rays which are so received by the X-ray detector from the material and those which are received by the X-ray detector from the means movable with the shutter.

2. An X-ray device as claimed in claim 1 in which the means movable with the shutter is a correction standard plate carried by the shutter.

3. An X-ray device as claimed in claim 1 or 2 in which the correction means are arranged to compare first data which relate to the fluorescent X-rays emitted by the said material with second data which relate to the fluorescent X-rays emitted by the said means movable with the shutter, the second data having been previously stored in the said memory.

4. An X-ray device as claimed in claim 3 in which there are means for periodically storing the second data in the memory at predetermined intervals.

5. An X-ray device as claimed in claim 4 in which there are means for averaging the second data which are stored in the memory at the said predetermined intervals.

6. An X-ray device as claimed in any preceding claim in which the X-ray tube has a collimator for collimating the X-rays from the X-ray tube.

7. An X-ray device as claimed in claim 6 in which the collimator has a first passage therein which is arranged to receive X-rays from the X-ray tube, and second and third passages therein which can communicate with the first passage, the second passage being arranged to direct X-rays from the said first passage onto the X-ray detector only when the shutter is closed, and the third passage being arranged to direct X-rays from the said first passage onto the material only when the shutter is open.

8. An X-ray device as claimed in any preceding claim in which there is an indicator or control means, controlled by the X-ray detector, for indicating the value of a property of said material or for exercising a control in dependence on said value.

9. An X-ray device as claimed in any preceding claim in which the correction means comprises a wave height analyser and a scaler timer.

10. An X-ray device as claimed in any preceding claim in which the correction means is controlled by a position sensor which senses the position of the shutter.

11. An X-ray device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

12. A method of correcting an X-ray device as claimed in claim 3 in which the second data are stored in the memory, and the first data are compared with the previously stored second data.

13. A method as claimed in claim 12 in which the means movable with the shutter is similar in composition and construction to that of the said material.

14. Any novel integer or step, or combination of integers or steps, hereinbefore described, and/or as shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention form that of, the preceding claims.

1 5. Automatic X-ray correction device comprising in combination: an X-ray tube: a collimator for collimating an X-ray beam emitted by said X-ray tube; a shutter for controlling irradiation of said X-rays onto a sample: an X-ray detector composed of a proportional counter or other detecting devices: a wave height analyzer: a scaler timer: a correction device for correcting an irregularity in the X-ray intensity and wave height value: a standard correction plate positioned on said shutter and positioned with respect to said X-ray tube to automatically correct an irregularity of X ray intensity and wave height value while said shutter is closed: a first guide hole for irradiating X-rays onto said standard correction plate: and a second guide hole which is connected to said first guide hole for irradiating a fluorescent X-ray of said standard correction plate onto said X-ray detector: whereby data measured during correction is memorized in a memory, and said data is used as secondary correction data when a sufficient measuring time for a correction has elapsed.