CN113587862A

CN113587862A - Device and method for measuring focus size of X-ray tube

Info

Publication number: CN113587862A
Application number: CN202110692234.7A
Authority: CN
Inventors: 袁钰函; 方志强; 张楠
Original assignee: Iray Technology Co Ltd
Current assignee: Iray Technology Co Ltd
Priority date: 2021-06-22
Filing date: 2021-06-22
Publication date: 2021-11-02

Abstract

The invention provides a device and a method for measuring the focal spot size of an X-ray tube. The CMOS detector has high sensitivity, high spatial resolution and high dynamic range, can quickly and accurately complete the detection of the focus of the X-ray tube by combining a one-key data processor, greatly improves the testing efficiency of the size of the focus, can realize the measurement of the focuses of different sizes from several micrometers to several millimeters, and has high detection precision and universality. In addition, the X-ray energy spectrum can be adjusted by selecting additional filtering with proper thickness, and the precision of focal spot size measurement is further improved.

Description

Device and method for measuring focus size of X-ray tube

Technical Field

The invention relates to the field of X-ray detection, in particular to a device and a method for measuring the focal size of an X-ray tube.

Background

An X-ray tube is an important component of an X-ray detection system, and is an element for generating X-rays, which functions to convert electrical energy into X-rays. In an X-ray imaging system, one of the factors that most affect the quality of X-ray imaging is the X-ray tube focal spot size, which affects the application and some main properties of the X-ray tube, such as bulb power, spatial resolution, thermal capacity, etc. Therefore, in the actual production and application of the X-ray tube, the size of the focal spot of the X-ray tube needs to be measured to evaluate the operating state and application type of the bulb.

The traditional measurement process of the focus size needs special focus detection equipment, the focus detection equipment is expensive and large in size, the operation is troublesome, the detection consistency is poor, and one set of equipment is difficult to adapt to the test of all types of focuses. When the traditional slit-camera-film method is used for measurement, the film needs to be frequently replaced, the film needs to be scanned and measured after the steps of washing, airing and fixing and the like are carried out in a darkroom, images on the film cannot be wiped or mistakenly touch an image area, otherwise the gray value of the images can be influenced, and meanwhile, a cassette needs to be prepared to tightly wrap the camera in the test process so as to prevent the influence of ambient light on the test result. The whole testing process has multiple steps, great difficulty and low efficiency, and a testing result has certain errors. In addition, because the size of the microfocus is small, when the microfocus size is measured, a high-precision camera is needed and is matched with a severe measurement parameter and a measurement system, and the traditional slit-camera-film method is difficult to simultaneously meet the high-precision detection of the microfocus and the common focus under one set of parameter or system and has certain limitation.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide an apparatus and a method for measuring the focal size of an X-ray tube, which are used to solve the problems of complicated process and poor versatility of the slit-camera-film method in the prior art.

To achieve the above and other related objects, the present invention provides an X-ray tube focal spot size measuring apparatus, comprising:

an X-ray tube that provides X-rays;

the through hole jig is provided with a through hole;

a CMOS detector, wherein the X-ray forms an image on the CMOS detector through the through hole to form an X-ray image;

and the data processor is communicated with the CMOS detector, acquires the X-ray image and performs data processing on the X-ray image, and outputs the length and the width of the focus of the X-ray tube and a corresponding line spread function.

Optionally, the through hole jig has a through hole diameter of 50 μm or less.

Optionally, an imaging area of the CMOS detector is smaller than 30mm × 40mm, a pixel size of the CMOS detector is 20 μm or less, an actual spatial resolution of the CMOS detector is 15lp/mm or more, and a dynamic range of the CMOS detector is 15Bits or more.

Optionally, the measuring apparatus further includes a beam limiter, and the beam limiter is located between the X-ray tube and the through hole jig.

Optionally, the size of the focus of the X-ray tube measured by the measuring device is in the range of 0.001mm-10mm, the magnification of the measuring device is above 20 times, and the error of the measuring device measuring the focus of the X-ray tube is less than 0.001 mm.

Optionally, the CMOS detector comprises an auto-triggered CMOS detector and a manual-triggered CMOS detector.

Optionally, the measuring device further comprises an additional filter, and the additional filter is located between the X-ray tube and the through hole jig.

Optionally, the material for additional filtering is Al, and the purity of Al is 99.5% or more.

The invention also provides a method for measuring the focal spot size of the X-ray tube, which comprises the following steps:

s1: providing the measuring device, and acquiring the X-ray image containing an X-ray tube focal spot through the CMOS detector;

s2: automatically analyzing the change of the image gray value of the X-ray image through the data processor, positioning the position of a focal spot, and acquiring a focal spot image;

s3: processing and calculating the focal spot image to obtain a line spread function of the X-ray tube focal point in the length direction and the width direction through the data processor, and respectively calculating the length and the width of the X-ray tube focal point by combining the magnification factor during testing and the type of the X-ray tube focal point;

s4: and synchronously displaying the length and the width of the focus of the X-ray tube and the corresponding line spread function through the data processor.

Optionally, the line spread function is a signal intensity versus pixel coordinate curve.

As described above, the apparatus and method for measuring the focal point size of an X-ray tube according to the present invention have the following advantageous effects: the measuring device comprises an X-ray tube, a through hole jig, a CMOS detector and a data processor, and the focus of the X-ray tube is imaged on the CMOS detector by utilizing the small hole imaging principle. And calculating the image obtained by the CMOS detector through a data processor to obtain the size of a focal spot in the X-ray image, and further obtaining the real size of the focus of the X-ray tube. The data processor can measure and calculate the X-ray tube focuses of different sizes and different types, and synchronously displays the length and the width of the X-ray tube focus and a corresponding line spread function, so that the X-ray tube focus measuring and calculating method is more visual and convenient. The CMOS detector has high spatial resolution, is simple to operate and convenient and fast to test, can accurately and quickly complete the detection of the focus of the X-ray tube, can quickly and accurately complete the detection of the focus of the X-ray tube by combining a one-key data processor, and can greatly improve the testing efficiency of the focus size compared with the traditional slit-camera-film method. And the measuring device can simultaneously meet the high-precision detection of the microfocus and the normal focus, realize the measurement of the focuses with different sizes from a few micrometers to a few millimeters, and has very high detection precision and universality. In addition, the X-ray energy spectrum can be adjusted by selecting the additional filtering with proper thickness, so that the energy distribution of the X-ray is more concentrated, the proper additional filtering can be selected in the actual test, and the precision of the measurement of the size of the focus can be improved to a certain extent.

Drawings

FIG. 1 is a schematic view of the structure of the measuring device of the present invention.

Fig. 2 is a schematic diagram showing the relationship between the thickness variation of the additional filtering and the X-ray energy spectrum distribution in the present invention.

Fig. 3 is a schematic diagram showing a method for measuring the focal spot size of the X-ray tube according to the present invention.

Fig. 4(a) shows an X-ray image measured for a microfocus in example 2.

Fig. 4(b) shows a focal spot image measured for a micro-focus in example 2.

Fig. 4(c) is a graph showing the results of the line spread function (length direction) measured for the microfocus in example 2.

Fig. 4(d) is a graph showing the results of the line spread function (width direction) measured for the microfocus in example 2.

Fig. 4(e) is a graph showing the three-dimensional results of the signal intensity measured for the microfocus in example 2.

Fig. 5(a) shows a focal spot image measured for a small focal spot in example 2.

Fig. 5(b) is a graph showing the results of the line spread function (length direction) measured for small focal spots in example 2.

Fig. 5(c) is a graph showing the results of the line spread function (width direction) measured for small focal spots in example 2.

Fig. 5(d) is a graph showing the three-dimensional results of the signal intensity measured for a small focal point in example 2.

Fig. 6(a) shows a focal spot image measured for a large focal spot in example 2.

Fig. 6(b) is a graph showing the results of the line spread function (length direction) measured for a large focal point in example 2.

Fig. 6(c) is a graph showing the results of the line spread function (width direction) measured for a large focal point in example 2.

Fig. 6(d) is a graph showing the three-dimensional results of the signal intensity measured for a large focal point in example 2.

Fig. 7 shows the final test results displayed by the data processor in the present invention.

Description of the element reference numerals

1X-ray tube

2 beam limiter

3 additional filtration

4 through hole jig

5 CMOS detector

m focal distance

n imaging distance

S1-S4

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. As used herein, "between … …" is meant to include both endpoints.

In the context of this application, a structure described as having a first feature "on" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed freely, and the layout of the components may be more complicated.

Example 1

As shown in fig. 1, the present embodiment provides an X-ray tube focal spot size measuring apparatus, including:

an X-ray tube 1, the X-ray tube 1 providing X-rays;

the through hole jig 4 is provided with a through hole;

a CMOS detector 5, wherein the X-ray forms an image on the CMOS detector 5 through the through hole to form an X-ray image;

and the data processor (not shown) is communicated with the CMOS detector 5, acquires the X-ray image and performs data processing on the X-ray image, and outputs the length and the width of the focus of the X-ray tube and a corresponding line spread function.

Specifically, the measuring device utilizes a small-hole imaging principle, the through hole jig 4 is arranged between the X-ray tube 1 and the CMOS detector 5, during testing, the X-ray tube 1 is started, parameters such as current and voltage of the X-ray tube 1 are well controlled, the position of the through hole jig 4 is well adjusted, and the focus of the X-ray tube 1 can be imaged on the CMOS detector 5. And obtaining the focal spot size of the X-ray tube 1 by the data processor through the focal spot size and the magnification of the X-ray image obtained on the CMOS detector 5. Wherein the magnification M is (n + M)/M. The X-ray image obtained by the CMOS detector 5 is transmitted to the data processor, and the data processor performs data processing on the X-ray image, so as to obtain a focal spot image corresponding to the X-ray image, and finally obtain the focal spot size of the X-ray tube 1 by processing the focal spot image. The data processor can also have a display function to synchronously display the length and the width of the focus of the X-ray tube and a corresponding line spread function, as shown in fig. 7, so that a plurality of test results can be synchronously observed, and the method is more intuitive and convenient. The data processor can be a one-button data processor, and after a start button is manually clicked, the one-button data processor can automatically complete the processes of image acquisition (acquiring the X-ray image), image processing (performing data processing on the X-ray image to finally obtain the focal size of the X-ray tube 1), result display (synchronously displaying the length and the width of the focal point of the X-ray tube and a corresponding line spread function) and the like, so that the operation is simple, convenient and intelligent.

The data processor may include a computer, the CMOS detector 5 and the data processor may communicate with each other by wire, for example, by a USB interface, although wireless communication may also be used between the CMOS detector 5 and the data processor, and the communication manner between the CMOS detector 5 and the data processor and the specific type of the data processor are not limited herein.

Further, the imaging area of the CMOS detector 5 is smaller than 30mm × 40mm, the pixel size of the CMOS detector 5 is 20 μm or less, the actual spatial resolution of the CMOS detector 5 is 15lp/mm or more, and the dynamic range of the CMOS detector 5 is 15Bits or more.

Further, the size of the focal point of the X-ray tube 1 measured by the measuring device ranges from 0.001mm to 10 mm.

Specifically, the CMOS detector 5 has a small size, and is generally used for intraoral dental photographing. In addition, the CMOS detector 5 has the advantages of small pixel size, high spatial resolution, and high dynamic range, and is simple to operate and convenient to test, and can accurately and rapidly complete the detection of the focus of the X-ray tube 1, and compared with the conventional slit-camera-film method, the efficiency of testing the focus size can be greatly improved. After calculation, the measurement device of the CMOS detector 5 is adopted, the focal size of the X-ray tube 1 is automatically calculated after exposure is started until the CMOS detector 5 obtains an image, the required time is within 10 seconds, and the mapping time is short. In addition, the CMOS detector 5 does not need environmental requirements such as a darkroom and a cassette in the using process, is directly connected with a computer through a USB interface for use, is convenient to connect, has high transmission speed, is convenient and efficient to test, and is convenient to operate repeatedly and adjust the placing angle and the amplification factor. The measuring device can simultaneously meet the high-precision detection of the microfocus and the normal focus, realizes the measurement of the focuses with different sizes from dozens of micrometers to several millimeters, and has high detection precision and universality. The measuring device can realize focus measurement of different types of X-ray tubes with different sizes, such as a microfocus bulb tube, a DR bulb tube, a CT bulb tube and the like.

Further, the magnification of the measuring device is more than 20 times, and the error of the measuring device for measuring the focus 1 of the X-ray tube is less than 0.001 mm.

Specifically, the testing accuracy depends on the size of the focal point size of the X-ray tube 1, the magnification M, and the pixel size of the CMOS detector 5, and when the magnification M is large, the through hole jig 4 is close to the X-ray tube 1, and the CMOS detector 5 is far from the X-ray tube 1. The larger the magnification is, the larger the focal spot area imaged by the X-ray tube 1 on the CMOS detector 5 is, the more the error generated during measurement can be reduced, and the measurement accuracy is improved.

Further, the diameter of the through hole jig 4 is 50 μm or less. The smaller the diameter of the through hole is, the higher the precision is, and the microfocus with smaller size can be tested. The CMOS detector 5 with high resolution is combined with the through hole jig 4 with high precision, the focus of the X-ray tube 1 can be tested without large amplification factor, and the testing precision is higher. Furthermore, the measuring device does not require a large magnification, the X-ray tube 1 and the CMOS detector 5 can be closer together, requiring a smaller X-ray dose, being safer and more rational (since the X-ray dose is inversely proportional to the square of the distance, the closer together the X-ray dose is required, the smaller the radiation).

Further, the CMOS detector 5 includes an auto-trigger CMOS detector and a manual-trigger CMOS detector. The automatic triggering CMOS detector can automatically acquire images after exposure is sensed, manual control of operations such as image acquisition is not needed, and work efficiency is greatly improved.

Further, the measuring device further comprises a beam limiter 2, and the beam limiter 2 is located between the X-ray tube and the through hole jig.

Specifically, the beam limiter 2 can control the irradiation range of the X-ray, so that the projection range can be reduced as much as possible on the premise that the test can be satisfied, unnecessary dose is avoided, scattered rays are absorbed, and the measurement accuracy is improved.

Further, the measuring device further comprises an additional filter 3, and the additional filter 3 is located between the X-ray tube 1 and the through hole jig 4 to filter soft rays in the X-rays. The material of the additional filter 3 is Al, and the purity of the Al is more than 99.5 percent. The thickness of the additional filter 3 is optional.

In particular, the additional filtering 3 is able to filter soft rays among the X-rays, making the X-ray energy distribution more concentrated, thereby further improving the accuracy of the focal spot size measurement. Because the soft rays can bring noise and other influences on the detection precision of the focus of the X-ray tube, the X-ray energy spectrum is adjusted through the additional filtering 3, and then the measurement of the focus is carried out, thereby being beneficial to the improvement of the measurement precision of the focus size.

As shown in fig. 2, the X-ray energy spectrum can be adjusted by changing the thickness of the additional filter 3, so that the energy distribution of the X-ray is more concentrated, and the appropriate additional filter can be selected in the actual test, thereby improving the precision of the measurement of the focal spot size to a certain extent.

Example 2

The present embodiment provides a method for measuring the focal spot size of an X-ray tube, as shown in fig. 3, the method includes the following steps:

In particular, the line spread function is a signal intensity (gray value) versus pixel coordinates. The method comprises the steps of determining a pixel coordinate span when the signal intensity of the line spread function is larger than a certain threshold value, respectively obtaining the length and the width of the focal spot according to the pixel coordinate span, and then respectively calculating the length and the width of the focal spot of the X-ray tube by combining the amplification factor during testing and the type of the focal spot of the X-ray tube. Since different types of the X-ray tube focus correspond to different calculation parameters, the X-ray tube focus type needs to be combined when calculating the size of the X-ray tube focus. The focus type of the X-ray tube can be divided into a micro focus, a small focus, and a large focus by size. Wherein the micro focus size is smaller than the small focus size and smaller than the large focus size.

The following describes in detail the testing of the focus of the X-ray tube 1 for different sizes.

(1) Measuring microfocus

Fig. 4(a) shows an X-ray image of the micro-focus, fig. (b) shows a focal spot image of the micro-focus, and fig. 4(c) and 4(d) show line spread functions of the focal spot in a length direction (X direction) and a width direction (y direction) obtained when the micro-focus is measured, respectively; the line spread function is a plot of signal intensity (gray scale value) versus pixel coordinates. Fig. 4(e) is a three-dimensional result graph of the signal intensity of the focal spot obtained when the micro-focus is measured.

When the pixel coordinate span is calculated, the threshold value is 50% or 90% of the signal intensity peak value, then the length and the width of the focal spot are obtained according to the obtained pixel coordinate span, and then the length and the width of the microfocus are respectively calculated by combining the amplification factor during the test; the resulting microfocus had a length and width of 0.07mm and 0.09mm, respectively (nominal size of 0.05 mm).

(2) Measuring small focal point

Fig. 5(a) shows a focal spot image of the small focal spot, and fig. 5(b) and 5(c) show line spread functions of the focal spot in the length direction (x direction) and the width direction (y direction) obtained when the small focal spot is measured, respectively; the line spread function is a plot of signal intensity (gray scale value) versus pixel coordinates. Fig. 5(d) shows a three-dimensional result graph of the signal intensity of the focal spot obtained when the small focal spot is measured.

When the pixel coordinate span is calculated, the threshold value is 15% of the signal intensity peak value, then the length and the width of the focal spot are obtained according to the obtained pixel coordinate span, and then the length and the width of the small focus are respectively calculated by combining the amplification factor during the test; the resulting small focal spots have a length and width of 0.86mm and 0.72mm, respectively (nominal size of 0.6 mm).

(3) Measuring large focal point

Fig. 6(a) shows a focal spot image of the large focal point, and fig. 6(b) and 6(c) show line spread functions of the focal spot in the length direction (x direction) and the width direction (y direction) obtained when the large focal point is measured; the line spread function is a plot of signal intensity (gray scale value) versus pixel coordinates. Fig. 6(d) shows a three-dimensional result graph of the signal intensity of the focal spot obtained when the large focal spot is measured.

When the pixel coordinate span is calculated, the threshold value is 15% of the signal intensity peak value, then the length and the width of the focal spot are obtained according to the obtained pixel coordinate span, and then the length and the width of the large focus are respectively calculated by combining the amplification factor during the test; the resulting large focal spot has a length and width of 1.48mm and 1.37mm, respectively (nominal size of 1.2 mm).

The following table shows the results obtained by measuring the focal size of the X-ray tube using the measuring apparatus of this embodiment:

fig. 7 shows the final test result displayed by the data processor in the present invention, which includes the X-ray image, the calculated length and width of the X-ray tube focus and the corresponding line spread function. A plurality of test results can be synchronously observed through the result page, and the method is more visual and convenient.

In summary, the present invention provides an apparatus and a method for measuring the size of a focus of an X-ray tube, wherein the apparatus comprises an X-ray tube, a through hole fixture, a CMOS detector and a data processor, and the focus of the X-ray tube is imaged on the CMOS detector by using the pinhole imaging principle. And calculating the image obtained by the CMOS detector through the data processor to obtain the focal spot size of the X-ray image, and further obtaining the real size of the focus of the X-ray tube. The data processor can measure and calculate the X-ray tube focuses of different sizes and different types, and synchronously displays the length and the width of the X-ray tube focus and a corresponding line spread function, so that the X-ray tube focus measuring and calculating method is more visual and convenient. The CMOS detector has high spatial resolution, is simple to operate and convenient and fast to test, can accurately and quickly complete the detection of the focus of the X-ray tube, can quickly and accurately complete the detection of the focus of the X-ray tube by combining a one-key data processor, and can greatly improve the testing efficiency of the focus size compared with the traditional slit-camera-film method. And the measuring device can simultaneously meet the high-precision detection of the microfocus and the normal focus, realize the measurement of the focuses with different sizes from a few micrometers to a few millimeters, and has very high detection precision and universality. In addition, the X-ray energy spectrum can be adjusted by selecting the additional filtering with proper thickness, so that the energy distribution of the X-ray is more concentrated, the proper additional filtering can be selected in the actual test, and the precision of the measurement of the size of the focus can be improved to a certain extent.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. An X-ray tube focal spot size measurement device, comprising:

an X-ray tube that provides X-rays;

the through hole jig is provided with a through hole;

2. The measurement device of claim 1, wherein: the diameter of the through hole jig is less than 50 mu m.

3. The measurement device according to claim 1, wherein the imaging area of the CMOS detector is less than 30mm x 40mm, the pixel size of the CMOS detector is 20 μm or less, the actual spatial resolution of the CMOS detector is 15lp/mm or more, and the dynamic range of the CMOS detector is 15Bits or more.

4. The measurement device of claim 1, further comprising a beam limiter positioned between the X-ray tube and the through-hole fixture.

5. The measurement device of claim 1, wherein the measurement device measures the size of the X-ray tube focus in a range of 0.001mm to 10mm, the measurement device has a magnification of 20 times or more, and the measurement device measures the X-ray tube focus with an error of less than 0.001 mm.

6. The measurement device of claim 1, wherein: the CMOS detector comprises an automatic trigger type CMOS detector and a manual trigger type CMOS detector.

7. The measurement device of claim 1, further comprising an additional filter positioned between the X-ray tube and the through-hole fixture.

8. The measuring device according to claim 7, wherein the material of the additional filtration is Al, and the purity of Al is more than 99.5%.

9. A method of measuring a focal spot size of an X-ray tube, the method comprising the steps of:

s1: providing the measurement device of any one of claims 1 to 8, acquiring the X-ray image containing an X-ray tube focal spot by the CMOS detector;

10. The measurement method according to claim 9, characterized in that: the line spread function is a relation curve of signal intensity and pixel coordinates.