Laser shock wave analysis method and device

Abstract

The invention discloses a laser shock wave analysis method and device. According to the specific scheme, the method comprises the steps of obtaining an electrode discharge picture of a laser within preset time; determining a shock wave processing area in the discharge picture area; and carrying out analysis processing on the shock wave processing area to obtain a shock wave analysis processing result. By adopting the method, the problem that the influence of the discharge time interval on the change of the shock wave region cannot be determined because the change condition of the shock wave region in the discharge cavity cannot be observed at low cost in the prior art is solved, and the discharge performance of the laser is improved. The invention also discloses a device for analyzing the shock wave by using the method.

Description

Technical Field

[0001] The invention relates to the field of optical technology, and in particular to a method and device for analyzing laser shock waves. Background Art

[0002] An excimer laser is a gas laser device that uses excimer gas as the working substance. During the short discharge cycle of an excimer laser when it is working, a large amount of energy is rapidly accumulated in the limited volume of laser gas in the discharge area, causing the temperature of the discharge area to rise rapidly, which leads to large fluctuations in the gas density and thus generates shock waves. By setting a high-speed rotating impeller, the discharge area is purged to propagate the shock wave outside the discharge area. The laser is reflected by the chamber wall and returns to the discharge area. As the discharge repetition frequency increases, the next discharge begins before the shock wave completely weakens. The reflected wave causes fluctuations in the gas density in the discharge area, thereby affecting the quality of the subsequent discharge laser pulses, increasing the line width of the laser, and ultimately reducing the performance of the laser.

[0003] Therefore, in order to ensure that the performance of the laser is not affected, the intensity of the laser at different time points after the laser discharge can be observed to understand the working frequency of the laser, or the structure of the discharge chamber can be changed so that the next discharge is not affected by the shock wave generated by the previous discharge. However, in the prior art, when observing the intensity of the laser at different time points after the shock wave discharge, the shock wave is not quantified, which will lead to inaccurate observation of the shock wave and low efficiency.

[0004] In the prior art, there is also a method of observing shock waves through frequency sweeping observation. However, when using this method, there will be many interference factors. If there is a problem with the shock wave, the result of the frequency sweeping will definitely be bad. However, if the result of the frequency sweeping is not good, it is not necessarily caused by the shock wave, and it may cause a large error in the final observed shock wave situation. Summary of the invention

[0005] The present invention provides a laser shock wave analysis method and device to solve the problems of complicated process, greatly increased observation cost and low efficiency in existing shock wave observation.

[0006] The present application provides a method for analyzing laser shock waves, including:

[0007] Obtaining the electrode discharge image of the laser within a preset time;

[0008] determining a shock wave processing area in the discharge image area;

[0009] An analysis process is performed on the shock wave processing area to obtain an analysis process result of the shock wave.

[0010] Optionally, the preset time is determined according to a discharge frequency of the laser.

[0011] Optionally, determining the shock wave processing area in the discharge image area includes:

[0012] Determining the range of the shock wave pretreatment area based on the spot size and energy distribution information of the laser;

[0013] The distance ratio information between the electrode discharge center and the pixel in the discharge picture is determined according to the position information of the laser electrode in the discharge picture.

[0014] Optionally, the range of the shock wave processing area is determined based on the discharge center of the electrode of the laser, pixel distance ratio information and the shock wave pre-processing area.

[0015] Optionally, the discharge center of the electrode is determined based on the identified position information of the left and right boundaries of the electrode of the laser in the discharge picture, the position information of the upper and lower boundaries of the electrode in the discharge picture, and the actual size information of the electrode;

[0016] Optionally, pixel distance ratio information in the discharge image is determined based on the identified position information of the left and right boundaries of the laser electrode in the discharge image, and / or the position information of the upper and lower boundaries of the electrode in the discharge image, and the actual distance information of the electrode.

[0017] Optionally, the center of the shock wave pre-processing area is overlapped with the discharge center, and the shock wave pre-processing area is expanded or reduced according to the pixel distance ratio information to determine the shock wave processing area in the discharge image area.

[0018] Optionally, based on the light intensity values ​​of all pixels in the shock wave processing area, an analysis and processing result of the shock wave is obtained.

[0019] Optionally, the performing analysis and processing on the shock wave processing area to obtain the analysis and processing result of the shock wave includes:

[0020] Based on the light intensity values ​​of all pixels in the shock wave processing area, the shock wave analysis result is obtained.

[0021] Optionally, obtaining the analysis and processing result of the shock wave based on the light intensity values ​​of all pixels in the shock wave processing area includes:

[0022] Obtaining a first processing result based on statistical processing of light intensity values ​​in the shock wave processing area;

[0023] The first processing result is normalized and subjected to noise processing to obtain a processed first processing result, and the processed first processing result is used as the analysis processing result of the shock wave.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The laser spot size calculation method provided in the present application is used to obtain a discharge image within a preset time, determine the shock wave processing area in the discharge image area, analyze and process the shock wave processing area, and obtain the shock wave analysis and processing result. By observing the shock wave processing area in the discharge image at different time points, the observation cost can be greatly reduced, and the complexity of the shock wave processing area process can be greatly reduced, so that it is easy to confirm how long after the shock wave discharge, the discharge will not affect the performance of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of a laser shock wave analysis method provided in the first embodiment of the present application.

[0027] Figure 2 It is a schematic diagram of how to obtain a discharge picture provided in the first embodiment of the present application.

[0028] Figure 3 It is a schematic diagram of a laser shock wave analysis device provided in the first embodiment of the present application. DETAILED DESCRIPTION

[0029] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] In order to reduce the errors existing in the existing shock wave observation, the present application proposes a method for directly processing the data of the discharge image in a simpler and more convenient manner, so as to obtain the result of observing the shock wave more directly.

[0032] like Figure 1 As shown, the specific process of implementing this application is as follows:

[0033] Step 101: Acquire an electrode discharge image of a laser within a preset time;

[0034] The laser of the present application is an excimer laser, and the preset time is a plurality of different time points, that is, the discharge pictures of the laser at different time points are obtained. The laser in the embodiment of the present application may also be other gas lasers. When the laser discharges, about 1-2% of the energy generated by the discharge turns into light, and the rest turns into heat. The heat generated by the discharge heats the discharge gas, so the gas temperature in the discharge area will be very high, and the discharge area forms an overpressure area. The shock wave generated by the instantaneous expansion of the gas in the discharge area between the cathode area and the anode area spreads outward in a shape similar to a sphere. The shock wave formed at this time can be used as a shock wave. As time changes, the shock wave area will change, so the change of the shock wave can be determined by observing the shock wave pictures of different time periods, so that it can be confirmed that after the last discharge of the laser, how much time has passed before the discharge again will not cause fluctuations in the gas density in the discharge area, and thus will not affect the quality of the subsequent laser pulses of the discharge. The shock wave will gradually weaken within a period of time after it is generated. If the shock wave is very weak in the main discharge area a microsecond after the discharge, it proves that the discharge corresponding to the frequency 1 / a Hz, that is, the next discharge a microsecond after the current discharge, will not have an impact on the discharge. Under high-frequency discharge, the shock wave may worsen, but the main trend is the same. This patent mainly considers the impact of the discharge cavity structure on the shock wave.

[0035] The discharge image is the image information received by ICCD. The specific acquisition process is as follows: Figure 2As shown: when the discharge cavity of the laser to be tested is discharging, the visible light laser on the far left is turned on. The visible reference light emitted by the visible light laser (indicated by the dotted line in the figure) is collimated by beam expansion to become a parallel light with a larger spot. After the visible reference light passes through the discharge cavity of the laser to be tested, the shock wave generated by the discharge cavity to be tested will be indirectly imaged on the screen, and the picture on the screen will be received by the ICCD. Due to the different discharge frequencies of the lasers, in order to better observe the shock wave changes and process data, the time resolution of the ICCD needs to be at least 1us, that is, it is necessary to observe the shock wave changes in the discharge area every 1us after the discharge. When observing the discharge, the discharge frequency is 100Hz, assuming that the shock wave conditions after each discharge are consistent, so that a complete discharge is formed through several discharges. In other words, when setting the preset time for collecting pictures, the discharge frequency of the laser needs to be considered. The specific relationship is: the discharge frequency of the laser is inversely proportional to the discharge period. When the operating frequency of the discharge cavity is 3KHz, its discharge period is 1 / 3KHz=333.3us, and when the operating frequency of the discharge cavity is 8KHz, its discharge period is 1 / 8KHz=125us.

[0036] Step 102: determining a shock wave processing area in the discharge image area;

[0037] In order to ensure that the final result is more accurate, it is necessary to process the area in the discharge image. Only the shock wave processing area in the discharge image can accurately reflect the changes in the shock wave. Therefore, it is particularly important to confirm the shock wave processing area. The specific process of confirming the shock wave processing area is as follows:

[0038] The scope of the shock wave processing area is determined based on the spot size and energy distribution information of the laser.

[0039] Specifically, based on the position information of the laser electrodes in the discharge image, the center of the two electrodes is determined, and this center is the discharge center; in addition, the pixel distance ratio information in the image is also determined.

[0040] Obtain the size of the spot and the distribution of energy, so that the shock wave pretreatment area information can be determined, the determined discharge center is used as the comparison center of the shock wave pretreatment area, and the pixel distance ratio information is used as the comparison standard for the expansion or reduction of the shock wave pretreatment area;

[0041] The pixel here refers to the resolution pixel on the ICCD. The ICCD can measure a light intensity value at each pixel.

[0042] Then, the center of the shock wave pre-processing area is aligned with the discharge center obtained as described above, and the shock wave pre-processing area is expanded or reduced according to the pixel distance ratio information, so as to determine the shock wave processing area in the discharge image area.

[0043] The specific process of determining the discharge center and pixel distance ratio information may be as follows:

[0044] Identify the position information of the left and right boundaries of the positive and negative electrodes of the laser in the discharge image, as well as the position information of the upper and lower boundaries of the positive and negative electrodes in the discharge image, so as to determine the discharge center;

[0045] Identify the position information of the left and right boundaries of the positive and negative electrodes of the laser in the discharge image, so as to determine the pixel information occupied by the electrode in the X direction on the discharge image, that is, confirm the pixel width information occupied by the electrode in the discharge image, and then convert the pixel distance ratio information in the image according to the actual width size of the electrode in the X direction.

[0046] Alternatively, the pixel distance information between the electrodes in the Y direction on the discharge image can be obtained, and the pixel distance ratio information in the discharge image can be determined according to the actual distance between the two electrodes in the Y direction. It is more accurate to determine the pixel distance ratio information in the discharge image according to the actual distance between the two electrodes in the Y direction, because the laser electrode is its key feature size and its projection is visible, which is more reference and marking.

[0047] Confirm the shock wave pretreatment area information based on the spot size and energy distribution information. For example, if the spot size is 2*10mm, but the spot energy is concentrated in the range of 1.5*8mm, we take the shock wave pretreatment range as 1.5*8mm. Make the center of the shock wave pretreatment area coincide with the above-mentioned discharge center, and expand or shrink the shock wave pretreatment area according to the above-mentioned pixel distance ratio information, so as to determine the shock wave treatment area in the discharge image area. If the shock wave treatment area is too large or too small, it cannot truly reflect the shock wave state of the laser discharge area.

[0048] Step 103: Analyze and process the shock wave processing area to obtain the analysis and processing result of the shock wave.

[0049] After the shock wave processing area is determined, shock wave images at different time points are collected. Therefore, it is necessary to perform certain analysis and processing on the shock wave processing area, specifically: based on the light intensity values ​​of all pixels in the shock wave processing area, the analysis and processing results of the shock wave are obtained. After the shock wave processing area is determined, the std (standard deviation) of the light intensity values ​​of all pixels in this area is calculated, and it is normalized. At the same time, some simple noise processing can be performed to remove the influence of noise. The final std result can directly reflect the disturbance of the light intensity in this area. The disturbance of the light intensity is proportional to the disturbance of the shock wave. The obtained std result of the light intensity value can be used to represent the shock wave disturbance in the discharge area. The above noise processing is conventional processing and will not be described in detail here.

[0050] By observing the above light intensity value std, the shock wave disturbance conditions at different time points can be observed by observing the results of the shock wave processing area in the discharge image at different time points. In this embodiment, by observing the intensity of the shock wave at different time points after the laser discharge, it can be known at what operating frequency the next discharge will not be affected by the shock wave generated by the previous discharge under a certain impeller speed of the laser, that is, it will not affect the quality of the laser pulse of the subsequent discharge.

[0051] Through this application, it is possible to understand which frequency of shock wave is the most obvious in the existing operating frequency range of the laser and at a certain impeller speed, and to better understand the changing trend of the shock wave. Through the present invention, it is possible to verify whether the shock wave structure design in the discharge cavity is reasonable, thereby promoting the optimization of the laser discharge cavity structure.

[0052] like Figure 3 As shown: The present application also provides a laser shock wave analysis device 300, comprising:

[0053] The image acquisition module 310 is used to acquire the discharge image within a preset time;

[0054] A processing area determination module 320, for determining a shock wave processing area in a discharge image area;

[0055] The result obtaining module 330 is used to perform analysis and processing on the shock wave processing area to obtain the analysis and processing result of the shock wave.

[0056] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

[0057] like Figure 2 As shown: The present application also provides a laser shock wave analysis device, comprising:

[0058] Visible light laser light source, the visible light laser light source in this embodiment is a green laser, of course, it can also be other visible light lasers;

[0059] The analysis device of this embodiment comprises a lens, a laser to be measured, a discharge image acquisition device, and a discharge result processing device arranged in sequence along the optical path behind the visible light laser light source;

[0060] Here, the lens amplifies the laser spot emitted by the light source and then injects it into the discharge cavity of the laser under test;

[0061] The lens can also be a combination of a microscope objective lens and a lens, both of which are used to amplify the laser spot emitted by the laser source;

[0062] The discharge image acquisition module is an ICCD here, but it can also be other similar devices that can measure light intensity.

[0063] When the discharge cavity of the laser under test discharges, the discharge image acquisition module acquires the discharge image of the laser under test within a preset time. For details, refer to the above embodiment.

[0064] The discharge result processing module determines the shock wave processing area in the discharge image area, and analyzes and processes the shock wave processing area to obtain the analysis and processing result of the shock wave. For details, refer to the above embodiment.

Claims

1. A method for analyzing laser shock waves, characterized in that: include: Obtaining the electrode discharge image of the laser within a preset time; determining a shock wave processing area in the discharge image area; An analysis process is performed on the shock wave processing area to obtain an analysis process result of the shock wave.

2. The method according to claim 1, characterized in that include: The preset time is determined according to the discharge frequency of the laser.

3. The method according to claim 1, characterized in that : The method of determining the shock wave processing area in the discharge image area includes: Determining the range of the shock wave pretreatment area based on the spot size and energy distribution information of the laser; The distance ratio information between the electrode discharge center and the pixel in the discharge picture is determined according to the position information of the laser electrode in the discharge picture.

4. The method according to claim 3, characterized in that: The range of the shock wave processing area is determined based on the electrode discharge center of the laser, the pixel distance ratio information and the shock wave pre-processing area.

5. The method according to claim 3, characterized in that: Determine the discharge center of the electrode based on the identified left and right boundary position information of the electrode of the laser in the discharge picture, the upper and lower boundary position information of the electrode in the discharge picture, and the actual size information of the electrode; The pixel distance ratio information in the discharge image is determined based on the identified left and right boundary position information of the laser electrode in the discharge image, and / or the upper and lower boundary position information of the electrode in the discharge image, and the actual distance information of the electrodes.

6. The method according to claim 4, characterized in that The center of the shock wave pre-processing area is made to coincide with the discharge center, and the shock wave pre-processing area is expanded or reduced according to the pixel distance ratio information to determine the shock wave processing area in the discharge image area.

7. The method according to claim 1, wherein the step of analyzing and processing the shock wave processing area to obtain the shock wave analysis and processing result comprises: Based on the light intensity values ​​of all pixels in the shock wave processing area, the shock wave analysis result is obtained.

8. The method according to claim 7, obtaining the analysis and processing result of the shock wave based on the light intensity values ​​of all pixels in the shock wave processing area, comprising: Obtaining a first processing result based on statistical processing of light intensity values ​​of all pixels in the shock wave processing area; The first processing result is normalized and subjected to noise processing to obtain a processed first processing result, and the processed first processing result is used as the analysis processing result of the shock wave.

9. A laser shock wave analysis device, characterized in that: include: A picture acquisition module, used to acquire discharge pictures within a preset time; A processing area determination module, used to determine a shock wave processing area in the discharge image area; The result obtaining module is used to perform analysis and processing on the shock wave processing area to obtain the analysis and processing result of the shock wave.

10. A laser shock wave analysis device, characterized in that: include: A visible light laser light source, and a lens, a laser to be tested, a discharge image acquisition module, and a discharge result processing module arranged in sequence along the light path; The lens amplifies the laser spot emitted by the light source and then injects it into the discharge cavity of the laser under test; When the discharge cavity of the laser under test discharges, the discharge picture acquisition module acquires the discharge picture of the laser under test within a preset time; The discharge result processing module determines a shock wave processing area in the discharge image area, and performs analysis and processing on the shock wave processing area to obtain an analysis and processing result of the shock wave.

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