Thermal lens effect detection method and detection device

Abstract

The present invention relates to a thermal lens effect detection method and device. The method comprises: using the Michelson interference method to set a test light path, so that the test light path forms circular ring-shaped fringes of equal-inclination interference after passing through a test window; passing a test light path through the test window, perpendicular to the test window; and determining the change in the test window by calculating the change in the circular ring-shaped fringes of equal-inclination interference. Because the method employs an interference method, even a slight wavelength-level change in the test window surface will cause a significant change in the circular ring-shaped fringes of equal-inclination interference. Therefore, high-precision measurements can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of thermal lens detection, and in particular to a thermal lens effect detection method and a detection device. Background Art

[0002] Optical components must minimize distortion during light transmission. If a laser light source is used in an application, the optical components must also exhibit extremely low light absorption. Light absorption can cause localized heating of the optical component, which can induce stress, refractive index changes, and ultimately cause focal shift. Light absorption can not only lead to poor performance but can also damage the optical component. Therefore, selecting an optical glass material with low absorption at the laser light source wavelength is particularly important in ultra-high-power optical systems.

[0003] The most widely used optical material for fiber laser cutting, welding, and marking is fused silica. Fused silica has two main sources of absorption: metallic impurities and hydroxyl groups. Synthetic fused silica typically contains negligible amounts of metallic impurities in the ppb range. However, in most of the near-infrared spectral range, light absorption is caused by hydroxyl groups. These groups are present in the fused silica glass matrix for manufacturing reasons. Fused silica is classified, among other parameters, based on its hydroxyl content as very high, high, medium, or low. The higher the power used, the lower the hydroxyl content of the fused silica material, resulting in lower light absorption and a smaller thermal lens.

[0004] Measuring thermal lensing is particularly difficult when using synthetic fused silica windows with very low hydroxyl content, for example, less than 8 ppm. Summary of the Invention

[0005] Based on this, a thermal lens effect detection method is provided, which can accurately detect the thermal lens effect of synthetic fused silica windows with very low hydroxyl content.

[0006] A thermal lens effect detection method, comprising:

[0007] The Michelson interference method is used to set the test light path so that the test light path forms an isotropic interference ring stripe after passing through the test window.

[0008] Make the test light path pass through the window to be tested, and the test light path is perpendicular to the window to be tested.

[0009] The change amount of the window to be measured is determined by calculating the change amount of the circular ring fringes of equal-inclination interference.

[0010] Because the method of this application utilizes an interferometric method, even a slight wavelength-level change in the surface of the test window will result in a significant change in the circular fringe pattern of the uniformly inclined interference pattern. Therefore, high-precision measurements can be achieved. This method is particularly suitable for testing synthetic fused silica windows with very low hydroxyl content, for example, less than 8 ppm.

[0011] This application separates the inspection and test optical paths, avoiding measurement accuracy errors caused by the test optical path. This application enables quantitative, high-precision measurements at the subwavelength level. This application is suitable for rapid measurement of a variety of window films.

[0012] In one embodiment, the test optical path is a high-power laser optical path.

[0013] In one embodiment,

[0014] The inspection optical path is formed by the following components:

[0015] In the first setting direction, an inspection laser light source, a light source aperture, a first condenser, a high-precision parallel plate and a first plane reflector are sequentially arranged. The first condenser is perpendicular to the first setting direction, the high-precision parallel plate is at an angle of 45 degrees to the first setting direction, and the first plane reflector is perpendicular to the first setting direction.

[0016] A second plane reflector, a second condenser and a measuring screen are sequentially arranged in the second setting direction.

[0017] The first setting direction and the second setting direction intersect each other perpendicularly, and the high-precision parallel plate is also located in the second setting direction, and the high-precision parallel plate is located between the second condenser and the measuring screen.

[0018] The window to be tested is arranged in a first setting direction, and is arranged parallel to the high-precision parallel plate. The window to be tested is located between the first plane reflector and the high-precision parallel plate.

[0019] In one embodiment, the test optical path is formed by the following components:

[0020] A test laser light source, a collimating lens group, a focusing lens group and a laser absorption cell are sequentially arranged in the third setting direction, wherein the collimating lens group is perpendicular to the third setting direction, and the focusing lens group is perpendicular to the third setting direction.

[0021] The angle between the third setting direction and the first setting direction is 45 degrees. The window to be tested is also located in the third setting direction and perpendicular to the third setting direction. The window to be tested is located between the collimating lens group and the focusing lens group.

[0022] In one embodiment, the testing laser light source is a high-power laser light source.

[0023] A thermal lens detection device,

[0024] In the first setting direction, an inspection laser light source, a light source aperture, a first condenser, a high-precision parallel plate and a first plane reflector are sequentially arranged. The first condenser is perpendicular to the first setting direction, the high-precision parallel plate is at an angle of 45 degrees to the first setting direction, and the first plane reflector is perpendicular to the first setting direction.

[0025] A second plane reflector, a second condenser and a measuring screen are sequentially arranged in the second setting direction.

[0026] The first setting direction and the second setting direction intersect each other perpendicularly, and the high-precision parallel plate is also located in the second setting direction, and the high-precision parallel plate is located between the second condenser and the measuring screen.

[0027] During the test, the window to be tested is set in the first setting direction, the window to be tested is located between the first plane reflector and the high-precision parallel plate, and the window to be tested is set parallel to the high-precision parallel plate.

[0028] A test laser light source, a collimating lens group, a focusing lens group and a laser absorption cell are sequentially arranged in the third setting direction, wherein the collimating lens group is perpendicular to the third setting direction, and the focusing lens group is perpendicular to the third setting direction.

[0029] The angle between the third setting direction and the first setting direction is 45 degrees. During detection, the window to be tested is also located in the third setting direction and perpendicular to the third setting direction, and the window to be tested is located between the collimating lens group and the focusing lens group. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of a thermal lens effect detection method according to an embodiment of the present application.

[0031] Figure 2 Schematic diagram of a thermal lens effect detection device according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details 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 may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] It should be noted that when an element is referred to as being “fixed to” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0035] like Figure 1 As shown, an embodiment of the present application provides a thermal lens effect detection method, which includes: using the Michelson interference method to set a test light path, so that the test light path forms circular ring stripes of equal-inclination interference after passing through the test window piece to be tested, so that the test light path passes through the test window piece to be tested, and the test light path is perpendicular to the test window piece to be tested, and the change amount of the test window piece to be tested is determined by calculating the change amount of the circular ring stripes of equal-inclination interference.

[0036] Specifically, the change amount of the window to be measured is d, the movement number of the circular ring fringes of the equal-inclination interference is N, and the wavelength of the incident light is λ, then d=Nλ / 2.

[0037] In one embodiment, the test optical path is a high-power laser optical path.

[0038] The above detection method of the present application is described in detail below through specific examples.

[0039] In one embodiment, the inspection optical path is formed by the following components: an inspection laser light source, a light source aperture, a first condenser, a high-precision parallel plate (with a surface profile accuracy better than λ / 10@632.8nm), and a first plane reflector are sequentially arranged in a first setting direction, the first condenser being perpendicular to the first setting direction, the high-precision parallel plate being at a 45-degree angle to the first setting direction, and the first plane reflector being perpendicular to the first setting direction. A second plane reflector, a second condenser, and a measurement screen are sequentially arranged in a second setting direction, the first and second setting directions intersecting perpendicularly, and the high-precision parallel plate is also located in the second setting direction, its rear surface coated with a spectroscopic silver film, and located between the second condenser and the measurement screen. The window to be tested is arranged in the first setting direction and parallel to the high-precision parallel plate. The window to be tested is located between the first plane reflector and the high-precision parallel plate.

[0040] The test optical path is a high-power laser optical path. The test optical path is formed by the following components: a test laser light source, a collimating lens assembly, a focusing lens assembly, and a laser absorption cell are sequentially arranged in a third setting direction. The collimating lens assembly is perpendicular to the third setting direction, and the focusing lens assembly is perpendicular to the third setting direction. The angle between the third setting direction and the first setting direction is 45 degrees. The window to be tested is also located in the third setting direction and is perpendicular to the third setting direction, and the window to be tested is located between the collimating lens assembly and the focusing lens assembly.

[0041] The specific detection process is as follows. First, the detection beam from the inspection laser light source passes through the light source aperture, the first condenser, the high-precision parallel plate, and the test window. Next, the detection beam is reflected by the first plane mirror, forming a first reflected beam. After passing through the test window, the first reflected beam is reflected by the high-precision parallel plate to the second condenser.

[0042] After passing through the second condenser, the detection beam is reflected by the second reflector, forming a second reflected beam. This second reflected beam then passes through the second condenser and a high-precision parallel plate before illuminating the measuring screen. Simultaneously, the detection beam from the inspection laser source passes through the light source aperture and the first condenser. A portion of the beam is reflected by the high-precision parallel plate, forming a third reflected beam, which then illuminates the measuring screen. Ultimately, on the measuring screen, the second and third reflected beams form circular interference fringes of equal inclination.

[0043] The window to be measured is made of the same material as the high-precision parallel plate, and its thickness is close to that of the high-precision parallel plate. This allows the optical paths of the second and third reflected beams to be compensated, ultimately causing interference between the second and third reflected beams. The rear surface of the high-precision parallel plate is coated with a translucent silver film, which separates the incident light into reflected and transmitted light of equal amplitude. Based on the Michelson interference principle, the virtual images of the first and second plane mirrors are adjusted to be strictly parallel, resulting in the appearance of circular fringes of equal-inclination interference on the measurement screen.

[0044] The laser beam emitted by the test laser source passes through the collimating lens assembly, the test window, and the focusing lens assembly, and finally converges into the laser absorption cell. The collimating lens assembly converges the diverging laser beam into a parallel beam. The focusing lens assembly converges the nearly parallel laser beam into the laser absorption cell.

[0045] When the test window is continuously irradiated by the laser beam from the test laser source, if a defect in the test window causes a change in the lens surface profile, the corresponding beam in the test light path will cause an optical path difference. For example, the corresponding beam in the first set direction will cause an optical path difference. This causes the interference fringes between the reference wavefront and the test wavefront in the test light path to shift. By calculating the change in the circular fringes of the uniformly inclined interference, the change in the overall surface profile can be determined. Because the interferometric method is used, even a slight change in the measured surface, at the wavelength level, will cause a significant change in the interference pattern. Therefore, high-precision measurements can be achieved.

[0046] In one embodiment, the testing laser light source is a high-power laser light source.

[0047] From the above analysis, it can be seen that the above method of the present application has the following beneficial effects:

[0048] 1. The high-power laser optical path used for testing is separated from the inspection optical path, which is very safe and convenient and can also ensure the consistency of measurement results.

[0049] 2. The inspection optical path adopts the Michelson interference principle, and the detection accuracy is very high.

[0050] 3. It overcomes the problem that traditional methods cannot achieve quantitative and high-precision measurements.

[0051] like Figure 2 As shown, the embodiment of the present application further provides a thermal lens detection device, specifically comprising:

[0052] In the first setting direction, a test laser light source, a light source aperture, a first condenser, a high-precision parallel plate, and a first plane reflector are sequentially arranged. The first condenser is perpendicular to the first setting direction, the high-precision parallel plate forms a 45-degree angle with the first setting direction, and the first plane reflector is perpendicular to the first setting direction. In the second setting direction, a second plane reflector, a second condenser, and a measuring screen are sequentially arranged. The first setting direction and the second setting direction intersect perpendicularly with each other, and the high-precision parallel plate is also located in the second setting direction, and the high-precision parallel plate is located between the second condenser and the measuring screen. During testing, the window to be tested is arranged in the first setting direction, the window to be tested is located between the first plane reflector and the high-precision parallel plate, and the window to be tested is arranged parallel to the high-precision parallel plate. In the third setting direction, a test laser light source, a collimating lens group, a focusing lens group, and a laser absorption cell are sequentially arranged. The collimating lens group is perpendicular to the third setting direction, and the focusing lens group is perpendicular to the third setting direction. The angle between the third setting direction and the first setting direction is 45 degrees. During detection, the window to be tested is also located in the third setting direction and perpendicular to the third setting direction, and the window to be tested is located between the collimating lens group and the focusing lens group.

[0053] The specific application method of the above device can refer to the specific description of the thermal lens effect detection method above.

[0054] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A thermal lens effect detection method, characterized in that: include: The Michelson interference method is used to set the test light path so that the test light path forms an isotropic interference ring stripe after passing through the test window. Make the test light path pass through the window to be tested, and the test light path is perpendicular to the window to be tested. The change of the window to be measured is determined by calculating the change of the circular fringes of equal-inclination interference. The inspection optical path is formed by the following components: In the first setting direction, an inspection laser light source, a light source aperture, a first condenser, a high-precision parallel plate and a first plane reflector are sequentially arranged. The first condenser is perpendicular to the first setting direction, the high-precision parallel plate is at an angle of 45 degrees to the first setting direction, and the first plane reflector is perpendicular to the first setting direction. A second plane reflector, a second condenser and a measuring screen are sequentially arranged in the second setting direction. The first setting direction and the second setting direction intersect each other perpendicularly, and the high-precision parallel plate is also located in the second setting direction, and the high-precision parallel plate is located between the second condenser and the measuring screen. The window to be tested is arranged in a first setting direction, and the window to be tested is arranged parallel to the high-precision parallel plate, and the window to be tested is located between the first plane reflector and the high-precision parallel plate. The test optical path is formed by the following components: a test laser light source, a collimating lens group, a focusing lens group and a laser absorption cell are sequentially arranged in the third setting direction, the collimating lens group is perpendicular to the third setting direction, the focusing lens group is perpendicular to the third setting direction, The angle between the third setting direction and the first setting direction is 45 degrees. The window to be tested is also located in the third setting direction and perpendicular to the third setting direction. The window to be tested is located between the collimating lens group and the focusing lens group.

2. The thermal lens effect detection method according to claim 1, characterized in that: The test optical path is a high-power laser optical path.

3. The thermal lens effect detection method according to claim 1, characterized in that: The test laser light source is a high-power laser light source.

4. A thermal lens effect detection device, characterized in that: In the first setting direction, an inspection laser light source, a light source aperture, a first condenser, a high-precision parallel plate and a first plane reflector are sequentially arranged. The first condenser is perpendicular to the first setting direction, the high-precision parallel plate is at an angle of 45 degrees to the first setting direction, and the first plane reflector is perpendicular to the first setting direction. A second plane reflector, a second condenser and a measuring screen are sequentially arranged in the second setting direction. The first setting direction and the second setting direction intersect each other perpendicularly, and the high-precision parallel plate is also located in the second setting direction, and the high-precision parallel plate is located between the second condenser and the measuring screen. During the test, the window to be tested is set in the first setting direction, the window to be tested is located between the first plane reflector and the high-precision parallel plate, and the window to be tested is set parallel to the high-precision parallel plate. A test laser light source, a collimating lens group, a focusing lens group and a laser absorption cell are sequentially arranged in the third setting direction, wherein the collimating lens group is perpendicular to the third setting direction, and the focusing lens group is perpendicular to the third setting direction. The angle between the third setting direction and the first setting direction is 45 degrees. During detection, the window to be tested is also located in the third setting direction and perpendicular to the third setting direction, and the window to be tested is located between the collimating lens group and the focusing lens group.

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