Aircraft windshield ultrathin scratch depth measuring device and method

Abstract

The invention discloses a device and a method for measuring the depth of an ultrathin scratch on an airplane windshield. The device comprises a 45-degree right-angle prism (1), a coupling film medium (2), airplane glass (3), a laser (4), a beam expanding collimating mirror (5) and a projection screen (6). According to the invention, the ultrathin scratch depth of the airplane windshield is measured through a thin film interference principle. The device takes water as a film medium and has no influence on the glass. The device obtains interference fringes projected to a screen, and the scratch depth with the visible light wavelength magnitude can be accurately obtained according to the fringe bending degree in combination with the thin film interference principle. The device is simple, the measurement is accurate, the device is very suitable for measuring the ultrathin scratch depth of the airplane windshield with multiple layers of media, and an important basis is provided for civil aviation maintenance personnel to evaluate the scratch depth.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft windshield scratch depth measurement, and particularly to an ultra-thin scratch depth measurement device and method for aircraft windshields. Background Technique

[0002] Aircraft windshields are crucial for flight safety, especially for civil aircraft windshields which are directly related to the safety of passengers. The breakage of an aircraft windshield can lead to extremely serious consequences. At flight altitude, to ensure the safety and comfort of passengers, the pressure and oxygen content inside the cabin need to be precisely regulated to simulate the ground environment. However, once any part of the aircraft is damaged, the huge pressure difference between the inside and outside of the cabin will quickly cause the cabin pressure to drop, and the air inside the cabin will rush out through the damaged part, and passengers may even be sucked out of the cabin.

[0003] Scratches on the surface of aircraft windshields may seriously affect flight safety, and timely regular inspection and replacement are very necessary. However, in aircraft maintenance, there is a lack of a fast and accurate scratch measurement device. In actual application, it is very difficult for aircraft maintenance personnel to directly obtain such accurate scratch depth, and they can only rely on experience and roughly judge by the method of embedding a hair. Equipment suitable for surface profile measurement, such as a line-scanning 3D profiler, can only be used to express the surface profile of an object in the air and is not suitable for measuring scratches on aircraft windshield glass with a multi-layer structure. Although ultra-thin scratches on the surface of aircraft windshields do not affect the structure of the windshield, a large number of ultra-thin scratches will significantly affect the pilot's line of sight. This will have an important impact on the takeoff and landing safety of the aircraft. When the shallow scratches on the windshield surface reach a certain degree, the windshield still needs to be replaced. However, there is still a lack of relevant auxiliary devices for judging the depth of shallow scratches. Although the naked eye is intuitive, it is difficult to give a quantitative result. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-thin scratch depth measurement device and method for aircraft windshields to solve the problems raised in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] An ultra-thin scratch depth measuring device and method for an aircraft windshield, characterized in that: the device includes a 45-degree right-angled triangular prism (1), a coupling thin film medium (2), an aircraft glass (3), a laser (4), a beam expander collimator (5), and a projection screen (6). The laser (4) and the beam expander collimator (5) are arranged at an interval in a row. The 45-degree right-angled triangular prism (1), the laser (4), the beam expander collimator (5), and the projection screen (6) maintain their relative positions unchanged. The laser is expanded by the beam expander collimator (5) and then irradiated onto the 45-degree right-angled triangular prism (1), and enters the coupling thin film medium (2) through the bottom of the prism. The reflected light on the upper and lower surfaces of the coupling thin film medium (2) generates interference at the projection screen (6), and the ultra-thin scratch depth of the windshield can be obtained according to the degree of interference fringe shift.

[0007] Preferably, the wavelength of the line beam laser (4) is in the visible light range of common 532nm, 633nm, or 650nm.

[0008] Preferably, the coupling thin film medium (2) can be water or a non-corrosive liquid with a certain viscosity.

[0009] Preferably, the interference fringes on the surface of the projection screen (6) can be collected by a camera.

[0010] Preferably, an ultra-thin scratch depth measuring device and method for an aircraft windshield includes the following measuring steps:

[0011] In the first step, a coupling agent is sprayed on the surface of the aircraft windshield, and the 45-degree right-angled triangular prism (1) is pressed against the coupling agent to form a stable and bubble-free close contact.

[0012] In the second step, the line beam laser (4) is turned on to emit a beam of visible light, and the spot diameter can cover the scratch width after passing through the beam expander collimator (5).

[0013] In the third step, the interference fringes on the surface of the projection screen (6) are collected, and the ultra-thin scratch depth is obtained according to the degree of offset of the interference fringe spacing and in combination with the thin film interference principle.

[0014] The specific formula derivation process for scratch depth measurement is as follows:

[0015] The height difference formula between two adjacent fringes of equal thickness interference

[0016]

[0017] where Δd is the height difference between two adjacent fringes of thin film interference, λ is the wavelength of the incident laser, and n 2 is the refractive index of the coupling thin film medium (2). The ratio between the adjacent fringe spacing Δl and the fringe offset width Δh obtained on the projection screen (6) is:

[0018]

[0019] The formula for the scratch depth can be obtained as follows:

[0020]

[0021] Among them, the ratio of the fringe offset width Δh to the adjacent fringe spacing Δl can be obtained according to the calibration operation based on the screen image collected by the camera, and its value range is from 0 to 1. The scratch depth can be obtained according to the specific values of each known quantity in the above formula. The scratch depth h measured by this method is close to the incident light wavelength and is in the nanometer range. Therefore, this method can accurately measure the depth of ultra-thin scratches.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] The present invention is designed for measuring scratches on the surface of aircraft glass, especially ultra-thin scratches. The device uses the principle of thin-film interference to measure the scratch depth. By collecting the spacing of interference fringes and the offset of fringes at the scratch by a camera, and substituting the specific values of each known quantity into the theoretical formula, the scratch depth can be obtained. The measurement range of the device is close to the incident light wavelength, and both the measurement accuracy and range reach the nanometer level, which can accurately reflect the depth of ultra-thin scratches on the aircraft windshield. The device of the present invention is very suitable for accurately measuring ultra-thin scratches on the surface of aircraft glass with a multi-layer structure. Brief Description of the Drawings

[0024] Figure 1 This is a device for measuring the depth of ultra-thin scratches on an aircraft windshield provided by the present invention.

[0025] Figure 2 This is a schematic diagram of the interference fringes of the reflected light of ultra-thin scratches on an aircraft windshield provided by the present invention. Detailed Description of the Invention

[0026] The following will combine the drawings and specific embodiments to elaborate in detail on a scanning device for measuring the depth of scratches on aircraft glass provided by the present invention.

[0027] Please refer to Figure 1 - Figure 2, the present invention provides a technical solution: an ultra-thin scratch depth measuring device and method for an aircraft windshield. The device includes a 45-degree right-angled triangular prism (1), a coupling thin film medium (2), an aircraft glass (3), a laser (4), a beam expander and collimator (5), and a projection screen (6). The laser (4) and the beam expander and collimator (5) are arranged at an interval in a row. The 45-degree right-angled triangular prism (1), the laser (4), the beam expander and collimator (5), and the projection screen (6) maintain their relative positions unchanged. The laser is expanded by the beam expander and collimator (5) and then irradiated onto the 45-degree right-angled triangular prism (1), and enters the coupling thin film medium (2) through the bottom of the prism. The reflected light on the upper and lower surfaces of the coupling thin film medium (2) generates interference at the projection screen (6), and the ultra-thin scratch depth of the windshield can be obtained according to the degree of interference fringe shift.

[0028] The wavelength of the linear beam laser (4) is in the visible light range of common 532nm, 633nm, or 650nm.

[0029] The coupling thin film medium (2) can be water or a non-corrosive liquid with a certain viscosity.

[0030] The interference fringes on the surface of the projection screen (6) can be collected by a camera.

[0031] An ultra-thin scratch depth measuring device and method for an aircraft windshield includes the following measuring steps:

[0032] In the first step, a coupling agent is sprayed on the surface of the aircraft windshield, and the 45-degree right-angled triangular prism (1) is pressed against the coupling agent to form a stable and bubble-free tight contact.

[0033] In the second step, the linear beam laser (4) is turned on to emit a beam of visible light, and the spot diameter can cover the scratch width after passing through the beam expander and collimator (5).

[0034] In the third step, the interference fringes on the surface of the projection screen (6) are collected, and the ultra-thin scratch depth is obtained according to the degree of offset of the interference fringe spacing and in combination with the thin film interference principle.

[0035] The specific formula derivation process for scratch depth measurement is as follows:

[0036] The height difference formula between two adjacent fringes of equal thickness interference

[0037]

[0038] where Δd is the height difference between two adjacent fringes of thin film interference, λ is the wavelength of the incident laser, and n 2 is the refractive index of the coupling thin film medium (2). The ratio between the adjacent fringe spacing Δl and the fringe offset width Δh obtained on the projection screen (6) is:

[0039]

[0040] The scratch depth formula can be obtained as follows:

[0041]

[0042] Among them, the ratio of the fringe offset width Δh to the adjacent fringe spacing Δl can be obtained through calibration operations based on the screen image captured by the camera, and its value range is from 0 to 1. The scratch depth can be obtained according to the specific values of each known quantity in the above formula. The scratch depth h measured by this method is close to the incident light wavelength and is in the nanometer range. Therefore, this method can accurately measure the depth of ultra-thin scratches.

[0043] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0044] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An ultra-thin scratch depth measurement device and method for aircraft windshield, characterized in that: The device comprises a 45-degree right angle prism (1), a coupling film medium (2), an aircraft glass (3), a laser (4), a beam expansion collimator (5), and a projection screen (6). The laser (4) and the beam expansion collimator (5) are arranged in a row at a distance. The relative positions of the 45-degree right angle prism (1), the laser (4), the beam expansion collimator (5), and the projection screen (6) remain unchanged. After being expanded by the beam expansion collimator (5), the laser is irradiated onto the 45-degree right angle prism (1), coupled into the coupling film medium (2) through the bottom of the prism, and the reflected light from the upper and lower surfaces of the coupling film medium (2) generates interference at the projection screen (6), and the depth of the ultra-thin scratch on the windshield can be obtained according to the degree of deviation of the interference fringes.

2. According to claim 1, a device and method for measuring the depth of ultra-thin scratches on an aircraft windshield, characterized in that: The wavelength of the linear beam laser (4) is in the common visible light range of 532nm, 633nm, or 650nm.

3. According to claim 1, a device and method for measuring the depth of ultra-thin scratches on an aircraft windshield, characterized in that: The coupling film medium (2) can be water or a non-corrosive liquid with a certain viscosity.

4. According to claim 1, an ultra-thin scratch depth measurement device and method for aircraft windshield, characterized in that: The interference fringes on the surface of the projection screen (6) can be collected by a camera.

5. According to claim 1, a device and method for measuring the depth of ultra-thin scratches on an aircraft windshield, characterized in that: The measurement steps include: The first step is to spray the coupling agent on the surface of the aircraft windshield, and press the 45-degree right-angle prism (1) against the coupling agent to form a stable and bubble-free close contact. The second step is to start the line beam laser (4) to emit a beam of visible light, and after passing through the beam expander collimator (5), the spot diameter can cover the width of the scratch. The third step is to collect interference fringes on the surface of the projection screen (6), and obtain the depth of the ultra-thin scratches based on the degree of deviation of the interference fringes spacing and the thin film interference principle.

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