Extreme ultraviolet band complete machine transfer function testing device and method

Abstract

The invention relates to the technical field of optical detection, and particularly provides an extreme ultraviolet band complete machine transfer function testing device and method, which comprises a light source system, a collimator, a knife edge target, a two-dimensional translation stage, an imager and a vacuum tank, the light source system comprises a laser used for generating an extreme ultraviolet band light beam energy source and a metal target used for generating extreme ultraviolet band continuous spectral lines, the knife edge target is arranged on the two-dimensional translation table and installed at the focal plane position of the collimator, and the laser plasma light source is used for emitting extreme ultraviolet light beams with the continuous spectral lines; the method comprises the following steps: using a collimator with the same wave band as an imager, emitting a specific extreme ultraviolet wave band light beam, pasting a sharp knife edge on a focal plane of the collimator, after reaching a vacuum degree, lightening a light source, moving a two-dimensional translation platform to find a position with the strongest light spot, acquiring an image, and calculating and analyzing the image to obtain an MTF curve of the imager; the method is suitable for MTF tests of all extreme ultraviolet band responsive imagers, and the operation is simple.

Description

Technical Field

[0001] The present invention relates to the field of optical detection technology, and specifically provides an extreme ultraviolet band complete machine transmission function testing device and method. Background Art

[0002] With the rapid development of the optoelectronic industry, optical systems are widely used in the aerospace field, and the detection devices and processing methods for evaluating the imaging quality of optical systems have also been continuously improved. At present, the commonly used objective and effective evaluation method is the optical transfer function evaluation method, which determines the imaging quality of the system by analyzing the contrast of targets at different spatial frequencies. There are three main methods for testing the transfer function of optical systems: resolution method, wave aberration method and optical transfer function method. The resolution method often uses a black and white rectangular or fan-shaped resolution plate with equal width to calculate the resolution based on the minimum fringe width that can be determined. The test process of this method is simple and can obtain quantitative values ​​to a certain extent, but this method cannot obtain a complete full-band transfer function curve. The wave aberration method uses the difference between the actual wavefront and the ideal spherical wave generated by the point object after passing through an optical system with aberrations. The commonly used method is the interference method, which detects the interference fringes formed by the interference of the detected wavefront and the known wavefront to obtain the system wave aberration. This method has high precision and is currently widely used in the assembly and detection of optical systems. The disadvantage is that the test method is relatively complicated, ignores the influence of detector and system stray light, and cannot simulate the actual use environment of the optical system. The optical transfer function method treats the object as composed of spectra of different frequencies, and analyzes the image after passing through the optical system to obtain low, medium and high frequency information. This method has a simple test process and can better reflect the real environment than the resolution method. Commonly used methods include: star point method, slit method and knife edge method. Among them, the knife edge method lays the foundation for measuring the whole machine transfer function in the extreme ultraviolet band.

[0003] 2.1 Resolution method: The extreme ultraviolet band cannot penetrate quartz glass, so conventional resolution plates cannot be used. Metal hollow resolution plates are prone to deformation and the edges of high-frequency stripes are not sharp enough. The imaging area of ​​the laser plasma light source is small and uneven. The above factors will lead to deviations in the test results. And the resolution plate cannot achieve full-band continuous MTF testing. Therefore, this method is not used to test the whole machine transmission function in the extreme ultraviolet band.

[0004] 2.2 Wave aberration method. The current mainstream interferometers (such as ZYGO) use white light laser light sources to complete white light wave aberration tests, and cannot obtain extreme ultraviolet band transmission function data. Therefore, this method is not suitable for short-wave transmission function tests.

[0005] 2.3 Optical transfer function method, in which 2.3.1 star point method, the star point method is to place an ideal point target on the focal plane of the collimator, adjust the camera position so that the image point is imaged on the surface of the camera detector, and calculate its point spread function to determine the MTF. The point spread function method requires that the target point smaller than 1 pixel is imaged in the pixel, and the target point is within the range of 1 pixel and cannot cross between two pixels (mixing phenomenon), which puts extremely high requirements on the registration of the target and the detector; and under vacuum conditions, vacuum equipment such as mechanical pumps and molecular pumps will vibrate, and it is easy for the point target to cross between two pixels, making the test difficult. 2.3.2 Slit method, in order to solve the problem of insufficient energy in the star point method, the slit method is proposed. The slit is equivalent to countless star points, which can provide relatively sufficient energy. The use of cross or rotating slits and other methods can realize the MTF test in the meridian and solitary directions. At present, the MTF transfer function instruments produced by TRIOPTICS of Germany and OPTIKOS of the United States all use this method. However, the slit width will affect the MTF test. The smaller the slit width, the closer it is to a line light source, and the more accurate the MTF test. The extreme ultraviolet light source has low brightness, poor light source uniformity, and a small area. The test result error is large, which is not suitable for extreme ultraviolet band testing. 2.2.3 Among the knife-edge methods, the inclined edge method proposed by Ruijter et al. has a simple test structure and calculation method. This method is to image the sharp knife edge onto the CMOS through a light pipe and a microscope lens, and with the filter, a single-wavelength full-frequency band MTF curve can be obtained. It is currently widely used in visible light detectors and whole-machine MTF tests, and is not suitable for extreme ultraviolet band testing. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an extreme ultraviolet band whole machine transmission function test device and method, which improves the energy of a specific extreme ultraviolet wavelength reaching the imager position. The knife-edge target realizes knife-edge image acquisition, and does not require the pixel-level alignment accuracy of the star point method, which reduces the difficulty of testing; the high-reflectivity coated collimator is used to increase the energy of the extreme ultraviolet band beam reaching the imager, and the extreme ultraviolet band whole machine MTF test is realized, which is suitable for all weak signal extreme ultraviolet band whole machine MTF tests.

[0007] In a first aspect, the present invention provides an extreme ultraviolet band whole machine transmission function test device, comprising a light source system, a collimator, a knife-edge target, a two-dimensional translation stage, an imager, and a vacuum tank for providing a target vacuum degree for all equipment in the test device, wherein the light source system comprises a laser for generating an energy source of an extreme ultraviolet band light beam and a metal target for generating a continuous spectrum line in the extreme ultraviolet band, the knife-edge target is arranged on the two-dimensional translation stage, and the knife-edge target is installed at the focal plane position of the collimator; In the rough alignment stage, a visible light source is placed at the position of the laser, the lens position is preliminarily determined according to the focal length of the front lens, and the two-dimensional translation stage is moved so that the knife-edge target is close to the light output position of the light source system, so that the imager receives the knife-edge target; In the test phase, the laser replaces the visible light source, all equipment in the test device is tightened and checked for air leakage, the vacuum degree of the vacuum tank is adjusted to the target vacuum degree, the laser is turned on, the lens position of the front lens is adjusted again so that the extreme ultraviolet band output light beam of the laser is the brightest, the position of the knife edge target on the two-dimensional translation stage in the translation direction is adjusted so that the knife edge position of the knife edge target is aligned with the brightest position of the extreme ultraviolet band output light beam, the extreme ultraviolet band output light beam is emitted to the imager through the collimator, the imager is turned on and collects the knife edge position image of the predetermined exposure time, the valve between the collimator and the imager is closed, the imager collects a dark field image, the knife edge image to be processed is subtracted from the dark field image, and the knife edge image to be processed is analyzed to obtain the modulation transfer function MTF curve of the imager.

[0008] As a preferred solution, the blade placement angle of the blade target is controlled at 2° to 10°.

[0009] As a preferred solution, the target vacuum degree is 1×10 -3 pa.

[0010] As a preferred solution, the visible light source is a visible light light emitting diode (LED).

[0011] As a preferred solution, the knife edge image to be processed is analyzed using the sfrmat3 software package.

[0012] As a preferred solution, the calculation method of the sfrmat3 software package is as follows:

[0013] Where LSF is the line transfer function, which is determined by the following formula:

[0014] in, is the line transfer function, e is a natural constant, is the actual distribution function of the gray value of the sharp edge of the image, is the actual ideal distribution function of the gray value of the knife edge, is the spatial frequency, i.e. the number of line pairs per millimeter, is the pixel position on the knife edge image to be processed.

[0015] As a preferred solution, the metal target is a copper target, and the laser and the copper target together constitute a laser plasma light source.

[0016] As a preferred solution, it also includes a through-the-warehouse cable and a computer for receiving, real-time displaying and storing images, one end of the through-the-warehouse cable is electrically connected to the imager, and the other end of the through-the-warehouse cable is electrically connected to the computer, and the through-the-warehouse cable transmits the electrical signal of the imager to the computer.

[0017] In a second aspect, the present invention provides an extreme ultraviolet band whole machine transmission function test method, the method is applied to the extreme ultraviolet band whole machine transmission function test device as described above, the method comprising: In the rough alignment stage, a visible light source is placed at the position of the laser, the light output intensity of the light source system is adjusted by adjusting the front-to-back distance of the front lens of the laser, and the two-dimensional translation stage is moved so that the knife-edge target is close to the light output position of the light source system, so that the imager receives the knife-edge target; In the test phase, the laser is used to replace the visible light source, all equipment in the test device is tightened and checked for air leakage, the vacuum degree of the vacuum tank is adjusted to the target vacuum degree, the laser is turned on, the lens position of the front lens is adjusted again so that the extreme ultraviolet band output light beam of the laser is the brightest, the position of the knife edge target on the two-dimensional translation stage in the translation direction is adjusted so that the knife edge position of the knife edge target is aligned with the brightest position of the extreme ultraviolet band output light beam, the extreme ultraviolet band output light beam is emitted to the imager through a collimator, the imager is turned on and collects the knife edge position image of a predetermined exposure time, the valve between the collimator and the imager is closed, the imager collects a dark field image, the knife edge image to be processed is subtracted from the dark field image, and the knife edge image to be processed is analyzed to obtain the modulation transfer function MTF curve of the imager.

[0018] Compared with the prior art, the present invention can achieve the following beneficial effects: The present invention provides an extreme ultraviolet band whole machine transmission function testing device and method, comprising a light source system, a collimator, a knife-edge target, a two-dimensional translation stage, an imager, and a vacuum tank for providing a target vacuum degree for all equipment in the testing device, wherein the light source system comprises a laser for generating an energy source of an extreme ultraviolet band light beam and a metal target for generating a continuous spectrum line in the extreme ultraviolet band, the knife-edge target is arranged on the two-dimensional translation stage, the knife-edge target is installed at the focal plane position of the collimator, and a laser plasma light source is used to emit an extreme ultraviolet light beam with a continuous spectrum line. For external light beam, a collimator with the same wavelength as the imager is used to emit a specific EUV beam. A sharp knife edge is pasted on the focal plane of the collimator. After reaching the vacuum degree, the light source is turned on, and the two-dimensional translation stage is moved to find the strongest position of the light spot and collect the image, and the image is calculated and analyzed to obtain the MTF curve of the imager. Based on the inclined edge method, a collimator with EUV coating is used to realize the MTF curve test of the EUV imager. This method is suitable for MTF test of all imagers that respond to the EUV band, and the operation is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of an extreme ultraviolet band whole machine transmission function testing device provided according to an embodiment of the present invention.

[0020] Reference numerals include: Laser 1, metal target 2, knife-edge target 3, two-dimensional translation stage 4, front lens 5, collimator 6, vacuum tank 7, imager 8, warehouse cable 9, computer 10. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0023] Combination Figure 1 As shown, an extreme ultraviolet band whole machine transmission function test device is provided in an embodiment of the present invention, including a light source system, a collimator 6, a knife-edge target 3 for generating a sharp edge image, a two-dimensional translation stage 4, an imager 8, and a vacuum tank 7 for providing a target vacuum degree for all devices in the test device. The vacuum tank 7 can provide a vacuum environment better than the target vacuum degree, and the target vacuum degree can be 10 -3pa vacuum degree, the collimator 6 is used to collimate the extreme ultraviolet light beam passing through the knife edge position to form a parallel light source, and output an infinitely far simulated solar beam. The two-dimensional translation stage 4 can align the knife edge position with the position of the strongest output beam of laser target shooting. The light source system includes a laser 1 for generating an energy source of an extreme ultraviolet band beam and a metal target 2 for generating a continuous spectrum line in the extreme ultraviolet band. The knife edge target 3 is arranged on the two-dimensional translation stage 4. The knife edge target 3 is installed at the focal plane position of the collimator 6. The imager 8 can include components such as an optical system and a detector. The detector is used to receive a light intensity signal passing through the optical system.

[0024] In the rough alignment stage, the visible light source is placed at the position of the laser 1, so that the imager 8 can be aligned with the monochromator output light spot, and the lens position is preliminarily determined according to the focal length of the front lens 5. The imager 8 is turned on, and the position of the knife-edge target 3 in the translation direction is adjusted so that the imager 8 detector can receive the knife-edge target 3. The knife-edge target 3 is moved close to the light output position of the light source system by moving the two-dimensional translation stage 4 so that the imager 8 receives the knife-edge target 3. The front lens 5 of the laser is used to focus the laser to increase the output light intensity.

[0025] In the test phase, the laser 1 replaces the visible light source, all equipment in the test device is tightened and checked for air leakage, the vacuum degree of the vacuum tank 7 is adjusted to the target vacuum degree, the laser 1 is turned on, and the lens position of the front lens 5 is adjusted again so that the extreme ultraviolet band output light beam of the laser 1 is the brightest, and the position of the knife edge target 3 on the two-dimensional translation stage 4 is adjusted so that the knife edge position of the knife edge target 3 is aligned with the brightest position of the extreme ultraviolet band output light beam, and the extreme ultraviolet band output light beam is emitted to the imager 8 through the collimator 6, the imager 8 is turned on and collects the knife edge position image of the predetermined exposure time, the valve between the collimator 6 and the imager 8 is closed, the imager 8 collects a dark field image, and the knife edge image to be processed is subtracted from the dark field image, and the knife edge image to be processed is analyzed to obtain the modulation transfer function MTF curve of the imager 8.

[0026] It should be noted that the blade placement angle of the blade target 3 is controlled between 2° and 10°. When the angle exceeds this range, the calculation result may have a large deviation.

[0027] In some embodiments, the laser 1 is a laser plasma light source, and the visible light source is a visible light light emitting diode LED.

[0028] In some embodiments, the knife edge image to be processed is analyzed using the sfrmat3 software package, the sharp knife edge is placed at the focal position, and a collimator 6 with an extreme ultraviolet band coating is used to implement an MTF curve test of the extreme ultraviolet band imager 8. This method is applicable to the MTF test of all imagers 8 that respond to the extreme ultraviolet band.

[0029] In some embodiments, the calculation method of the sfrmat3 software package is as follows:

[0030] Where LSF is the line transfer function, which is determined by the following formula:

[0031] in, is the line transfer function, e is a natural constant, is the actual distribution function of the gray value of the sharp edge of the image, is the actual ideal distribution function of the gray value of the knife edge, is the spatial frequency, i.e. the number of line pairs per millimeter, is the pixel position on the knife edge image to be processed, which is equivalent to calculating the gray value difference of multiple pixels near the light and dark edges of the knife edge image to obtain the detector transfer function.

[0032] In some embodiments, the metal target 2 is a copper target, and the laser 1 and the copper target together constitute a laser plasma light source, which can generate continuous spectrum lines in the extreme ultraviolet band. Ordinary technicians in this field can flexibly choose according to needs and there is no limitation on this.

[0033] In some embodiments, it also includes a through-the-warehouse cable 9 and a computer 10 for receiving, real-time displaying and storing images. One end of the through-the-warehouse cable 9 is electrically connected to the imager 8, and the other end of the through-the-warehouse cable 9 is electrically connected to the computer 10. The through-the-warehouse cable 9 transmits the electrical signal of the imager 8 to the computer 10.

[0034] The present invention provides an extreme ultraviolet band whole machine transmission function testing device, comprising a light source system, a collimator 6, a knife-edge target 3, a two-dimensional translation stage 4, an imager 8, and a vacuum tank 7 for providing a target vacuum degree for all equipment in the testing device. The light source system comprises a laser 1 for generating an energy source of an extreme ultraviolet band light beam and a metal target 2 for generating a continuous spectrum line in the extreme ultraviolet band. The knife-edge target 3 is arranged on the two-dimensional translation stage 4. The knife-edge target 3 is installed at the focal plane position of the collimator 6. The laser plasma light source is used to emit a continuous spectrum line. An extreme ultraviolet beam is used, and a collimator 6 with the same band as the imager 8 is used to emit a specific extreme ultraviolet band beam. A sharp knife edge is pasted on the focal plane of the collimator 6. After reaching a vacuum degree, the light source is turned on, and the two-dimensional translation stage 4 is moved to find the strongest position of the light spot and collect the image and perform calculation and analysis on the image to obtain the MTF curve of the imager 8. Based on the inclined edge method, a collimator 6 with an extreme ultraviolet band coating is used to realize the MTF curve test of the extreme ultraviolet band imager 8. This method is suitable for testing the MTF test of all imagers 8 that have a response in the extreme ultraviolet band.

[0035] Accordingly, an embodiment of the present invention further provides an extreme ultraviolet band whole machine transmission function test method, the method is applied to the extreme ultraviolet band whole machine transmission function test device as described above, the method comprising: In the rough alignment stage, the visible light source is placed at the position of the laser 1, the lens position is preliminarily determined according to the focal length of the front lens 5, and the two-dimensional translation stage 4 is moved so that the knife-edge target 3 is close to the light output position of the light source system, so that the imager 8 receives the knife-edge target 3; In the test phase, the laser 1 replaces the visible light source, all equipment in the test device is tightened and checked for air leakage, the vacuum degree of the vacuum tank 7 is adjusted to the target vacuum degree, the laser 1 is turned on, and the lens position of the front lens 5 is adjusted again so that the extreme ultraviolet band output light beam of the laser 1 is the brightest, and the position of the knife edge target 3 on the two-dimensional translation stage 4 in the translation direction is adjusted so that the knife edge position of the knife edge target 3 is aligned with the brightest position of the extreme ultraviolet band output light beam, and the extreme ultraviolet band output light beam is emitted to the imager 8 through the collimator 6, the imager 8 is turned on and collects the knife edge position image of the predetermined exposure time, the valve between the collimator 6 and the imager 8 is closed, the imager 8 collects a dark field image, and the knife edge image to be processed is subtracted from the dark field image, and the knife edge image to be processed is analyzed to obtain the modulation transfer function MTF curve of the imager 8.

[0036] The present invention provides an extreme ultraviolet band whole machine transmission function test method, comprising a light source system, a collimator 6, a knife-edge target 3, a two-dimensional translation stage 4, an imager 8, and a vacuum tank 7 for providing a target vacuum degree for all equipment in the test device, wherein the light source system comprises a laser 1 for generating an energy source of an extreme ultraviolet band light beam and a metal target 2 for generating a continuous spectrum line in the extreme ultraviolet band, the knife-edge target 3 is arranged on the two-dimensional translation stage 4, the knife-edge target 3 is installed at the focal plane position of the collimator 6, and an extreme ultraviolet band with a continuous spectrum line is emitted by a laser plasma light source. Ultraviolet light beam, use a collimator 6 with the same band as the imager 8 to emit a specific extreme ultraviolet band light beam, stick a sharp knife edge on the focal plane of the collimator 6, after reaching a vacuum degree, light the light source, move the two-dimensional translation stage 4 to find the strongest position of the light spot and collect the image and perform calculation and analysis on the image to obtain the MTF curve of the imager 8. Based on the inclined edge method, use a collimator 6 with an extreme ultraviolet band coating to realize the MTF curve test of the extreme ultraviolet band imager. This method is suitable for testing the MTF test of all imagers 8 that respond to the extreme ultraviolet band, and the operation is simple.

[0037] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0038] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An extreme ultraviolet band complete machine transmission function test device, characterized in that: It includes a light source system, a collimator, a knife-edge target, a two-dimensional translation stage, an imager, and a vacuum tank that provides a target vacuum degree for all equipment in the test device. The light source system includes a laser for generating an energy source of an extreme ultraviolet light beam and a metal target for generating a continuous spectrum line in the extreme ultraviolet band. The knife-edge target is arranged on the two-dimensional translation stage, and the knife-edge target is installed at the focal plane position of the collimator; In the rough alignment stage, a visible light source is placed at the position of the laser, the lens position is preliminarily determined according to the focal length of the front lens, and the two-dimensional translation stage is moved so that the knife-edge target is close to the light output position of the light source system, so that the imager receives the knife-edge target; In the test phase, the laser replaces the visible light source, all equipment in the test device is tightened and checked for air leakage, the vacuum degree of the vacuum tank is adjusted to the target vacuum degree, the laser is turned on, the lens position of the front lens is adjusted again so that the extreme ultraviolet band output light beam of the laser is the brightest, the position of the knife edge target on the two-dimensional translation stage in the translation direction is adjusted so that the knife edge position of the knife edge target is aligned with the brightest position of the extreme ultraviolet band output light beam, the extreme ultraviolet band output light beam is emitted to the imager through the collimator, the imager is turned on and collects the knife edge position image of the predetermined exposure time, the valve between the collimator and the imager is closed, the imager collects a dark field image, the knife edge image to be processed is subtracted from the dark field image, and the knife edge image to be processed is analyzed to obtain the modulation transfer function MTF curve of the imager.

2. The extreme ultraviolet band complete machine transmission function testing device according to claim 1, characterized in that: The knife edge placement angle of the knife edge target is controlled at 2° to 10°.

3. The extreme ultraviolet band complete machine transmission function testing device according to claim 1, characterized in that: The target vacuum degree is 1×10 -3 pa.

4. The extreme ultraviolet band complete machine transmission function testing device according to claim 1, characterized in that: The visible light source is a visible light light emitting diode (LED).

5. The extreme ultraviolet band complete machine transmission function testing device according to claim 1, characterized in that: The knife edge image to be processed is analyzed using the sfrmat3 software package.

6. The extreme ultraviolet band complete machine transmission function testing device according to claim 5, characterized in that: The calculation method of the sfrmat3 software package is as follows: Where LSF is the line transfer function, which is determined by the following formula: in, is the line transfer function, e is a natural constant, is the actual distribution function of the gray value of the sharp edge of the image, is the actual ideal distribution function of the gray value of the knife edge, is the spatial frequency, i.e. the number of line pairs per millimeter, is the pixel position on the knife edge image to be processed.

7. The extreme ultraviolet band complete machine transmission function testing device according to claim 1, characterized in that: The metal target is a copper target, and the laser and the copper target together constitute a laser plasma light source.

8. The extreme ultraviolet band complete machine transmission function testing device according to claim 1, characterized in that: It also includes a through-the-warehouse cable and a computer for receiving, real-time displaying and storing images. One end of the through-the-warehouse cable is electrically connected to the imager, and the other end of the through-the-warehouse cable is electrically connected to the computer. The through-the-warehouse cable transmits the electrical signal of the imager to the computer.

9. A method for testing the transmission function of a complete machine in the extreme ultraviolet band, characterized in that: The method is applied to the extreme ultraviolet band complete machine transmission function testing device according to any one of claims 1 to 8, and the method comprises: In the rough alignment stage, a visible light source is placed at the position of the laser, the lens position is preliminarily determined according to the focal length of the front lens, and the two-dimensional translation stage is moved so that the knife-edge target is close to the light output position of the light source system, so that the imager receives the knife-edge target; In the test phase, the laser is used to replace the visible light source, all equipment in the test device is tightened and checked for air leakage, the vacuum degree of the vacuum tank is adjusted to the target vacuum degree, the laser is turned on, the lens position of the front lens is adjusted again so that the extreme ultraviolet band output light beam of the laser is the brightest, the position of the knife edge target on the two-dimensional translation stage in the translation direction is adjusted so that the knife edge position of the knife edge target is aligned with the brightest position of the extreme ultraviolet band output light beam, the extreme ultraviolet band output light beam is emitted to the imager through a collimator, the imager is turned on and collects the knife edge position image of a predetermined exposure time, the valve between the collimator and the imager is closed, the imager collects a dark field image, the knife edge image to be processed is subtracted from the dark field image, and the knife edge image to be processed is analyzed to obtain the modulation transfer function MTF curve of the imager.

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