Angle scanning type airplane windshield scratch depth measuring device and method

Abstract

The invention discloses an angle scanning type airplane windshield scratch depth measuring device and method. The angle scanning type airplane windshield scratch depth measuring device comprises a 45-degree right-angle prism (1), a coupling agent (2), a linear beam laser (4) and a CMOS camera (5). The method has the advantages that the scattered light projection of the scratch can be obtained through angle scanning of the linear light beam, and the scratch depth is obtained through nonlinear fitting according to the relation between the projection length and the angle. The device is simple, the measurement is accurate, the device is very suitable for measuring the scratch depth of the airplane windshield with multiple layers of media, especially the high depth, and the device has a good application prospect in the field of civil aviation maintenance.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft windshield scratch depth measurement, and specifically to a scanning aircraft windshield scratch depth measurement device and method. Background Technique

[0002] The windshield of a civil aircraft is crucial for flight safety. The breakage of an aircraft windshield can lead to extremely serious consequences. At flight altitude, in order 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 an aircraft windshield may seriously affect flight safety, and timely regular inspection and replacement are very necessary. However, in aircraft maintenance, there is a lack of fast and accurate scratch measurement equipment. According to the regulations of the maintenance manual, if the scratch depth of the inner layer of the glass is higher than 381 μm, the entire windshield needs to be replaced (the damage standard refers to AMM56-11-00-200-803). However, in actual application, it is very difficult for aircraft maintenance personnel to directly obtain such accurate scratch depth, and they can only roughly judge by embedding a hair with experience. 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 windshields with multiple layers. Summary of the Invention

[0004] The purpose of the present invention is to provide an angular scanning aircraft windshield scratch depth measurement device and method 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 angular scanning aircraft windshield scratch depth measurement device and method, including a 45-degree right-angled triangular prism (1), a coupling agent (2), a line beam laser (4), and a CMOS camera (5). The line beam laser (4) can rotate around the center of the bottom of the triangular prism, so as to scan and measure scratches by using the total reflection light inside the aircraft glass. The CMOS camera (5) vertically downward collects the length of the projected bright line after being irradiated by the line beam, and calculates the scratch depth through the length of the projected bright line and the incident angle.

[0007] Preferably, the wavelength of the line beam laser (4) is in the visible light range of common 532 nm, 633 nm, or 650 nm. The coupling agent (2) is deionized water or other common non-corrosive liquids.

[0008] Preferably, the CMOS camera (5), the 45-degree right-angled triangular prism (1), and the rotation center of the line beam laser (4) are arranged in a row from left to right, fixed on a metal substrate, and their relative positions remain unchanged. The line beam laser (4) can rotate around the rotation center at a fixed angle, and the line beam direction is parallel to the paper surface.

[0009] An angle-scanning type aircraft windshield scratch depth measuring device and method, including the following measuring steps:

[0010] 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.

[0011] In the second step, the line beam laser (4) is turned on to emit a line beam parallel to the paper surface, which is obliquely irradiated onto the side surface of the prism at a certain incident angle. The beam width is about 1 cm.

[0012] In the third step, the CMOS camera (5) vertically downward collects the length of the projected bright line after being irradiated by the line beam.

[0013] In the fourth step, the incident angle between the incident light and the prism is changed, and the CMOS camera (5) vertically downward collects the length of the projected bright line after being irradiated by the line beam again. The incident light angle is changed multiple times by scanning, and the corresponding projected bright line lengths are obtained. Through non-linear fitting between the two, the scratch depth can be obtained. The specific formula derivation process for scratch depth measurement is as follows:

[0014] The laser emitted by the line beam laser (4) enters the side surface of the prism at an incident angle of i from the air. According to the refractive index law, and assuming the refractive index of air is 1 at the same time. It can be obtained that

[0015] sini = n1sinr

[0016] Where the refractive index of the triangular prism is n1. The beam enters the coupling agent at the bottom surface of the prism and then enters the aircraft windshield from the coupling agent, and is totally reflected and transmitted inside the glass. According to the refractive law again, there is

[0017] n1sinr = n3sinβ

[0018] Where the refractive index of the windshield is n3. The total reflection angle β inside the windshield can be obtained as

[0019]

[0020] After the total reflection line beam inside the windshield irradiates the scratch, a bright line with a length of l generated by scratch scattering will be produced on the upper surface of the glass. Let the scratch depth be h, then

[0021]

[0022] According to

[0023]

[0024] the relationship between the incident angle i and the scratch scattering length l can be obtained as follows:

[0025]

[0026] During the test, the incident angle i is changed by rotating the line beam laser (4), so that a series of scratch scattering lengths l on the windshield surface can be obtained. According to the above function relationship, the numerical value of the scratch depth h can be obtained through non-linear fitting.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The present invention is designed for measuring scratches on the surface of aircraft glass, especially deep scratches. The device uses a commercially common semiconductor laser and is combined with a CMOS camera. By measuring simple geometric parameters such as the incident angle and the length of the projected bright line, the scratch depth of the aircraft glass can be obtained by non-linear fitting. The multi-layer characteristics of aircraft glass cause that when obtaining the scratch depth by other means, the refraction influence of multi-layer media must be considered, resulting in inaccurate measurement, especially the poor measurement of some optical measurement devices. The device of the present invention is very suitable for measuring scratches on the surface of aircraft glass with a multi-layer structure, especially for on-line non-destructive measurement, and the refractive index of multi-layer glass has no influence on the method of the present invention. Description of the Drawings

[0029] Figure 1 An angle-scanning type aircraft glass scratch depth measuring device provided by the present invention.

[0030] Figure 2 The angle-scanning process of an angle-scanning type aircraft glass scratch depth measuring device provided by the present invention. Detailed Embodiments

[0031] The following combines the drawings and specific embodiments to detail an angle-scanning type aircraft glass scratch depth measuring device provided by the present invention.

[0032] Please refer to Figure 1 - Figure 2, the present invention provides a technical solution: an angle-scanning device and method for measuring the scratch depth of an aircraft windshield, including a 45-degree right-angled triangular prism (1), a coupling agent (2), a line-beam laser (4), and a CMOS camera (5). The line-beam laser (4) can rotate around the center of the bottom of the triangular prism, so as to use the total internal reflection light inside the aircraft glass to scan and measure the scratch. The CMOS camera (5) vertically downward collects the length of the projected bright line after being irradiated by the line beam, and calculates the scratch depth through the length of the projected bright line and the incident angle.

[0033] The wavelength of the line-beam laser (4) is in the visible light range of common 532nm, 633nm, or 650nm. The coupling agent (2) is deionized water or other common non-corrosive liquids.

[0034] The CMOS camera (5), the 45-degree right-angled triangular prism (1), and the rotation center of the line-beam laser (4) are arranged in a row from left to right, fixed on a metal substrate, and the relative positions remain unchanged. The line-beam laser (4) can rotate around the rotation center at a fixed angle, and the direction of the line beam is parallel to the paper surface.

[0035] The angle-scanning device and method for measuring the scratch depth of an aircraft windshield include the following measurement steps:

[0036] In the first step, the surface of the aircraft windshield is sprayed with a coupling agent, and the 45-degree right-angled triangular prism (1) is pressed on the coupling agent to form a stable and bubble-free close contact.

[0037] In the second step, the line-beam laser (4) is turned on to emit a line beam parallel to the paper surface, and it is obliquely irradiated to the side surface of the prism at a certain incident angle. The beam width is about 1 cm.

[0038] In the third step, the CMOS camera (5) vertically downward collects the length of the projected bright line after being irradiated by the line beam.

[0039] In the fourth step, the incident angle between the incident light and the prism is changed, and the CMOS camera (5) vertically downward collects the length of the projected bright line after being irradiated by the line beam again. By changing the incident light angle multiple times through the scanning method and obtaining the corresponding lengths of the projected bright lines, the scratch depth can be obtained through non-linear fitting between the two. The specific formula derivation process for measuring the scratch depth is as follows:

[0040] The laser emitted by the line-beam laser (4) is incident on the side surface of the prism at an incident angle of i from the air. According to the refractive index law, and assuming the refractive index of air is 1 at the same time. It can be obtained that

[0041] sini = n1sinr

[0042] Among them, the refractive index of the triangular prism is n1. The light beam is incident on the coupling agent from the bottom surface of the prism and then from the coupling agent into the aircraft windshield. It is totally reflected and transmitted inside the glass. According to the law of refraction again, we have

[0043] n1sinr = n3sinβ

[0044] Among them, the refractive index of the windshield is n3. The total reflection angle β inside the windshield can be obtained as

[0045]

[0046] After the total reflection line beam inside the windshield irradiates the scratch, a bright line with a length of l generated by the scratch scattering will be produced on the upper surface of the glass. Let the scratch depth be h, then

[0047]

[0048] According to

[0049]

[0050] The relationship between the incident angle i and the scratch scattering length l can be obtained as follows

[0051]

[0052] During the test, by rotating the line beam laser (4) to change the incident angle i, a series of scratch scattering lengths l on the windshield surface can be obtained. According to the above functional relationship, the scratch depth h value can be obtained through non-linear fitting.

[0053] 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.

[0054] 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 angle scanning aircraft windshield scratch depth measurement device and method, characterized in that: The device comprises a 45-degree right-angle prism (1), a coupling agent (2), a line beam laser (4), and a CMOS camera (5). The line beam laser (4) can use the bottom center of the prism as the rotation center to scan and measure the scratches using the total reflected light inside the aircraft glass. The CMOS camera (5) vertically downwardly collects the length of the projected bright line of the scratch after being irradiated by the line beam, and calculates the scratch depth based on the projected length and angle.

2. According to claim 1, an angle scanning aircraft windshield scratch depth measurement device and method, characterized in that: The wavelength of the linear beam laser (4) is in the common visible light range of 532nm, 633nm, or 650nm. The coupling agent (2) is deionized water or other commonly used non-corrosive liquids.

3. According to claim 1, an angle scanning aircraft windshield scratch depth measurement device and method, characterized in that: The CMOS camera (5), the 45-degree right-angle prism (1), and the rotation center of the line beam laser (4) are arranged in a row from left to right and fixed on the metal substrate, and the relative positions remain unchanged. The line beam laser (4) can rotate around the rotation center at a fixed angle, and the direction of the line beam is parallel to the paper surface.

4. According to claim 1, an angle scanning aircraft windshield scratch depth measurement device and method, 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 turn on the line beam laser (4) to emit a line beam parallel to the paper surface and irradiate the side of the prism at a certain incident angle. The beam width is about 1 cm. The third step is to collect the length of the projected bright line after the meridian light beam is irradiated vertically downward by using the CMOS camera (5). The fourth step is to change the incident angle between the incident light and the prism, and collect the projection light length of the scratch light vertically downward again through the CMOS camera (5). The scratch depth is obtained by nonlinear fitting between multiple angles and projection light lengths.

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