A system and method for determining the clarity of a windshield glass

Abstract

A windscreen clarity measurement system and method for detecting and evaluating the influence of a water film formed on the outer surface of a windscreen on the windscreen clarity, characterized by: a water film thickness detection device provided on the inner surface of the windscreen on the cabin side, capable of emitting infrared light to the outer surface side of the windscreen in a pulse manner and receiving the reflected infrared light as a detection signal; a control device sending a control signal to the water film thickness detection device, capable of driving the water film thickness detection device to emit infrared light at a specified frequency through the control signal; and a calculation device receiving the detection signal from the control device or the water film thickness detection device, capable of determining a clarity index capable of representing the windscreen clarity as a calculation result based on the detection signal. Thus, the influence of the water film formed on the outer surface of the windscreen on the windscreen clarity can be detected and evaluated in real time.

Description

Technical Field

[0001] This application relates to a system and method for measuring windshield clarity. Background Technology

[0002] It is well known that rainwater severely impairs driver visibility. Existing technologies have made significant improvements, but these improvements require reliable and accurate measurement data. Therefore, it is necessary to develop devices and methods for detecting or evaluating the impact of rainwater on windshield clarity. For example, there are known methods that evaluate wiping effectiveness by photographing and recording the pattern of water streaks on the windshield after a single wipe by a car's windshield wipers, based on the pattern and distribution of these streaks. However, this measurement method is suitable for situations where rainwater is distributed in stripes. In many situations, such as typhoons, torrential rains, or high-speed driving, rainwater is distributed as a film.

[0003] Specifically, streaks of water are discontinuous, linear marks formed by the flow or partial accumulation of water. They are of uneven width, do not cover the entire surface but remain in certain areas, and their optical effects manifest as localized refraction and scattering, causing localized distortion or blurring of the field of view. In contrast, a water film is a continuous, thin layer of water covering a solid surface, of varying thickness. It can create optical interference effects, significantly affecting transmittance and optical properties (reflection, refraction, scattering), resulting in overall blurring and haloing. Therefore, it requires special attention in sharpness measurements. It is evident that the two differ significantly in both characteristics and effects, and their measurement methods are not interchangeable.

[0004] Especially in the aviation industry, water films typically form on windshields. For example, when an aircraft encounters heavy rain during takeoff, approach, and landing, raindrops can form a water film on the outer surface of the cockpit windshield, reducing light transmission, interfering with the pilot's vision, and threatening flight safety. Therefore, international and domestic airworthiness regulations contain relevant provisions, such as requiring aircraft to have measures to ensure that a clear portion of the windshield remains visible during precipitation, providing both pilots with a sufficiently wide field of vision along the flight path in all normal aircraft attitudes. This measure must be designed to be effective in all situations without requiring constant attention from the crew. Consequently, during the type certification process for civil aircraft (i.e., the review and verification by the civil aviation airworthiness authority before a civil aircraft enters the market, hereinafter referred to as "civil aircraft certification"), tests must be conducted to demonstrate the compliance of the aircraft's windshield rain removal system with the relevant provisions.

[0005] However, heavy rain is extremely rare, and single heavy rain events are generally short-lived, making it difficult to capture weather windows for flight tests. Furthermore, conducting flight tests directly without sufficient ground testing also carries significant risks. Therefore, scientific and effective ground testing methods are crucial. Currently, it is known that the impact of rain on cockpit visibility stems primarily from two aspects: first, the attenuation of visible light after scattering by raindrops (i.e., the impact of external rain on cockpit visibility); and second, the reflection and refraction of light by the water film on the glass surface, reducing the clarity of the windshield (i.e., the impact of the water film on the windshield on cockpit visibility). The former can be quantitatively assessed using the visible light attenuation formula for rainy weather: I = I0e -βL Where β is the attenuation coefficient (related to raindrop density and size), and L is the propagation path length; for the latter, a purely subjective evaluation method is usually adopted, that is, in an artificially simulated rain environment, the test driver visually evaluates whether the windshield visibility is acceptable in the cockpit model.

[0006] While subjective methods for evaluating windshield clarity are easy to implement, they also have several drawbacks. For example, relying on participants' perceptions and judgments makes them susceptible to influences from personal preferences, emotions, and experiences, potentially leading to biased results. Furthermore, because subjective evaluation depends on individual feelings, different participants or even the same participant at different times may reach different conclusions, resulting in low reproducibility. Additionally, to ensure the validity of the results, participants must be active-duty drivers, limiting the pool of potential participants and making it difficult to obtain a large sample size, thus reducing the confidence level of the experiment. Moreover, subjective evaluations are typically qualitative and difficult to quantify with precise numerical values, posing challenges to data analysis and comparison. Therefore, there is an urgent need for a system and method capable of real-time detection and evaluation of the impact of water film on windshield clarity in simulated rain environments in the laboratory or in real-world rain environments. Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] This application was developed to solve the above-mentioned technical problems, and its purpose is to provide a windshield clarity measurement system and method, which can detect and evaluate the impact of water film formed on the outer surface of the windshield on windshield clarity in real time.

[0009] Technical solutions adopted to solve technical problems

[0010] This application provides a windshield clarity measurement system for detecting and evaluating the impact of a water film formed on the outer surface of the windshield on the windshield clarity. The system includes: a water film thickness detection device disposed on the inner surface of the windshield on the cockpit side, capable of emitting infrared light in a pulsed manner towards the outer surface of the windshield and receiving the reflected infrared light as a detection signal; a control device that sends a control signal to the water film thickness detection device, enabling the control signal to drive the water film thickness detection device to emit infrared light at a predetermined frequency; and a calculation device that receives the detection signal from the control device or the water film thickness detection device, and is capable of determining a clarity index characterizing the windshield clarity as a calculation result based on the detection signal.

[0011] Preferably, the water film thickness detection device includes: a PCB substrate layer that can bend with the curvature of the windshield; a plurality of detection units, each including a corresponding infrared emitter and an infrared receiver, and independently arranged in a dot matrix on the PCB substrate layer; and an optical cover layer that is bonded to the PCB substrate layer to cover the plurality of detection units, wherein the infrared emitter emits infrared light and the infrared receiver receives the reflected light along the entire path of the infrared light emitted by the corresponding infrared emitter.

[0012] Preferably, the optical cover layer has a concave spherical cavity formed on the side of the PCB substrate layer that is attached to it, and at the position corresponding to the infrared receiver. The optical cover layer is attached to the PCB substrate layer in such a way that it completely covers the infrared emitter and houses the infrared receiver in the concave spherical cavity.

[0013] Preferably, the optical coating layer is attached to the inner surface of the windshield on the cockpit side of the opposite side of the PCB substrate layer by means of a suction cup structure or adhesive.

[0014] Preferably, the control device generates a high-frequency pulse signal to drive the water film thickness detection device to emit infrared light in such a way that the pulse interval T is greater than the sum of the time from the emission to the last reflection of the infrared light.

[0015] Preferably, the detection signal is a signal containing the light intensity of the reflected infrared light, and the computing device calculates the water film thickness at the emission location of the infrared light based on the light intensity of the reflected infrared light using Snell's law and Beer-Lambert's law.

[0016] Preferably, the computing device calculates the water film thickness distribution based on the calculated water film thickness using a spatial interpolation algorithm.

[0017] Preferably, the computing device establishes optical transfer models for dry and wet windshields based on the calculated water film thickness distribution, calculates the modulation transfer function and the area under the curve of the modulation transfer function for each optical transfer model, and determines the sharpness index of the windshield based on the ratio of the area under the curve.

[0018] Preferably, the windshield is divided into multiple viewing zones and assigned different weights. The computing device calculates the sharpness index of each viewing zone and obtains the overall sharpness index by weighted summation.

[0019] Preferably, it further includes a display device capable of receiving and displaying the calculation results of the computing device.

[0020] This application provides a method for measuring windshield clarity, which is performed using the aforementioned windshield clarity measurement system. The method includes: installing the water film thickness detection device on the inner surface of the windshield on the cockpit side; the water film thickness detection device collecting infrared reflection signals in a laboratory-constructed rain environment or a real rain environment as the detection result; and the computing device calculating the clarity index in real time based on the detection result as the calculation result.

[0021] Preferably, the display device dynamically presents the results based on the calculation.

[0022] Preferably, the wiper operating mode is adjusted, and the rain removal effect of the wipers is confirmed by the real-time measurement of the windshield clarity index. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the windshield clarity measurement system according to one embodiment of this application.

[0024] Figure 2 This is a diagram showing the water film thickness detection device in the absence of water.

[0025] Figure 3 This is a diagram showing the water film thickness detection device in the presence of water.

[0026] Figure 4 This is a schematic diagram of the installation of the water film thickness detection device on the windshield.

[0027] Figure 5 This is the overall flowchart of the windshield clarity measurement system.

[0028] Figure 6 This is a flowchart of the calculation process for the resolution index of a computing device.

[0029] Figure 7 This is a schematic diagram of the area under the curve of the modulation transfer function (MTF).

[0030] Figure 8 This is a schematic diagram of the windshield's viewing area division.

[0031] Figure 9 This is a schematic diagram of the windshield's viewing area division.

[0032] Figure 10 This is a schematic flowchart of a windshield clarity measurement method according to an embodiment of this application.

[0033] Symbol explanation:

[0034] 1: Water film thickness detection device; 11: PCB substrate layer; 12: Infrared emitter; 13: Infrared receiver; 14: Optical cover layer; 141: Concave spherical cavity; 15: Detection unit;

[0035] 2: Control device; 3: Computing device; 4: Display device. Detailed Implementation

[0036] The present application is further described below with reference to the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the present application. The same or corresponding reference numerals in the figures denote the same components, and repeated descriptions are omitted. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0037] In the description of this application, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience and simplification of the description of this application, and should not be construed as limiting this application. The term "connection" should be interpreted broadly; those skilled in the art can understand the specific meaning of the above term in this application according to the specific circumstances.

[0038] When the speed is high or the rainfall is heavy, rainwater falls on the outer surface of the windshield 7, causing a water film W to form on the outer surface of the windshield 7. This water film W reduces the overall clarity of the windshield, affecting the driver's vision and creating a flight hazard. Therefore, this application provides a windshield clarity measurement system (hereinafter sometimes referred to as the system) that can achieve objective, quantitative, and real-time measurement of windshield clarity under the influence of water film.

[0039] Hereinafter, a system according to an embodiment of this application will be described with reference to the accompanying drawings.

[0040] like Figure 1As shown, the system includes: a water film thickness detection device 1 installed on the windshield 7; a control device 2 connected to (at least including a communication connection) the water film thickness detection device 1 and controlling the water film thickness detection device 1; and a calculation device 3 connected to (at least including a communication connection) the control device 2 and calculating the sharpness based on the detection result of the water film thickness detection device 1. In addition, the system also includes a display device 4.

[0041] [Water film thickness detection device 1]

[0042] like Figure 2 , 3 As shown in Figure 4, in this embodiment, the water film thickness detection device 1 is installed on the inner surface of the windshield 7 on the cockpit side, covering the entire windshield 7, i.e., the side that does not come into contact with rainwater, thereby avoiding direct scouring and interference from external rainwater. However, the water film thickness detection device 1 may also cover only a portion of the windshield 7 depending on specific test requirements. Specifically, the water film thickness detection device 1 includes: a PCB substrate layer 11 that can be bent and fitted according to the curvature of the windshield 7; a plurality of detection units 15 provided on the PCB substrate layer 11; and an optical cover layer 14 that is fitted to the PCB substrate layer 11 to cover the detection units 15.

[0043] The PCB substrate layer 11 serves as a base for mechanical connections and a pathway for electrical connections, on which electronic components (e.g., an infrared transmitter 12 and an infrared receiver 13) are mounted. In this embodiment, the PCB substrate layer 11 may be made of flexible materials such as polyimide (PI) or polyester film (PET), and is connected to the control device 2 and the computing device 3 (at least including communication connections) via printed circuits.

[0044] The detection unit 15 includes an infrared emitter 12 and an infrared receiver 13. The infrared emitters 12 and infrared receivers 13 are disposed one-to-one on the PCB substrate layer 11, forming an independent detection unit 15. Multiple infrared emitters 12 and multiple infrared receivers 13 respectively constitute multiple independent detection units 15. For example... Figure 2 , 3 As shown in Figure 4 (for simplicity, only some detection units are labeled), multiple detection units 15 are evenly arranged in a dot matrix on the PCB substrate layer 11. However, this is not the only possibility; the multiple detection units 15 can also be arranged with varying densities depending on specific requirements. Furthermore, in this embodiment, since the detection units 15 are independent of each other, the water film thickness detection device 1 can be appropriately tailored according to specific needs without affecting the functionality. Preferably, the area of ​​each detection unit 15 can be set to, for example, one square centimeter, and they are arranged adjacent to each other. In addition, since visible light is easily affected by environmental interference and ultraviolet light is easily absorbed, neither is suitable as a detection signal, so infrared light is selected for detection.

[0045] In this embodiment, the infrared emitter 12 converts electrical energy into infrared light of a specific wavelength, and the infrared receiver 13 receives the reflected light along the entire path of the infrared light emitted by the corresponding infrared emitter 12, and converts the incident infrared light into an electrical signal. Specifically, the infrared emitter 12 can be, for example, an infrared light-emitting diode or an infrared laser diode, and the infrared receiver 13 can be, for example, a photodiode and / or a phototransistor. The infrared emitter 12 generates infrared light towards the windshield 7 according to a control command. This infrared light propagates to the target object (such as the windshield 7 or the surface of a water film on it) and is reflected and refracted. The infrared receiver 13 receives the reflected infrared light and converts it into an electrical signal, thereby calculating the film thickness using optical path difference or reflection intensity.

[0046] Furthermore, in this embodiment, the infrared emitter 12 preferably emits infrared light with a wavelength of approximately 1450 nm. This is because water exhibits significant absorption characteristics at this wavelength, and variations in the water film thickness lead to noticeable differences in the intensity of the reflected signal, thereby achieving highly sensitive detection of the water film thickness. Simultaneously, 1450 nm falls within the near-infrared band, outside the visible light range, effectively avoiding ambient light interference and ensuring the stability and accuracy of the measurement.

[0047] Furthermore, in this embodiment, preferably, the incident angle of the infrared emitter 12 is set to less than 30°. This is because a smaller incident angle reduces reflection loss at the air / glass interface, allowing most of the infrared light to enter the windshield. Simultaneously, it avoids total internal reflection caused by an excessively large incident angle, thus ensuring that the reflected light can be effectively received by the infrared receiver 13. Moreover, under small incident angle conditions, the relationship between the optical path and the water film thickness is more stable, which is beneficial for improving the accuracy of subsequent water film thickness calculations. In this embodiment, the reflection of infrared light includes, for example, reflection at the windshield-air interface (hereinafter referred to as interface 3) in the absence of water, and reflection at the windshield-water film interface (hereinafter referred to as interface 1) and the water film-air interface (hereinafter referred to as interface 2) in the presence of water. Furthermore, the relative positions of the infrared emitter 12 and the infrared receiver 13 are not particularly limited, as long as the aforementioned transmission and reception functions can be effectively achieved.

[0048] The optical cover layer 14 is a transparent optical medium layer used to cover and protect electronic components (such as the external emitter 12 and the infrared receiver 13). In this embodiment, the optical cover layer 14 can be made of flexible optical silicone, for example, and its refractive index can be the same as that of the windshield glass 7, thereby reducing the refraction and reflection loss of light. Furthermore, on the side of the optical cover layer 14 that is attached to the PCB substrate layer 11, a concave spherical cavity 141 is formed at a position corresponding to the infrared receiver 13. Therefore, when the optical cover layer 14 is attached to the PCB substrate layer 11 (on which electronic components are arranged), the optical cover layer 14 can completely cover the infrared emitter 12, and the infrared receiver 13 is housed in the concave spherical cavity 141. Thus, the reflected light can be refracted and converged through the concave spherical cavity 141, allowing it to enter the infrared receiver 13 more efficiently. Preferably, the infrared receiver 13 is positioned approximately at the center of the circle at the junction of the concave spherical cavity 141 and the PCB substrate layer 11. In this embodiment, for example, a pre-made mold can be used during the manufacturing of the optical cover layer 14 to reserve a spherical cavity at the position corresponding to the infrared receiver 13. After the optical cover layer 14 is formed, it is bonded to the underlying PCB substrate layer 11 to form a concave spherical cavity 141. Because such a concave spherical cavity 141 is formed, the relative positions of the infrared emitter 12 and the infrared receiver 13 can be more flexible.

[0049] Furthermore, in this embodiment, the optical cover layer 14 has a suction cup structure (not shown) on the side opposite to the bonding surface of the PCB substrate layer 11. Therefore, when the water film thickness detection device 1 is installed on the windshield 7, the side of the optical cover layer 14 with the suction cup is tightly bonded to the inner surface of the windshield 7, achieving stable and tight adhesion and preventing air gaps from affecting the measurement. However, the installation method is not limited to this; any method can be used as long as it allows the water film thickness detection device 1 to be stably and completely bonded to the windshield 7 to avoid the formation of air gaps, such as adhesive bonding.

[0050] The following, combined with Figure 2 , 3 Explain the detection principle of water film thickness detection device 1.

[0051] like Figure 2 As shown, when there is no water film on the outer surface of the windshield 7, infrared light with an incident intensity of Io reaches the interface 3 between the windshield 7 and the air, and undergoes refraction towards the air side and reflection towards the glass side. The refracted light (L...) 折射1 The intensity of the reflected light (L) is Iz1, and the intensity of the reflected light (L) is... 反射1 The intensity of the reflected light (L) is Ir1. 反射1The light is refracted by the concave spherical cavity 141 and then received by the infrared receiver 13. The infrared receiver 13 will then combine the received light with the reflected light (L... 反射1 The relevant optical signals are converted into electrical signals (i.e., detection signals) and output to the control device 2 and / or the computing device 3.

[0052] like Figure 3 As shown, when a water film exists on the outer surface of the windshield 7, infrared light with an incident intensity of Io reaches the interface 1 between the windshield 7 and the water film, and undergoes refraction towards the water film side and reflection towards the glass side. The refracted light (L...) 折射1 The intensity of the reflected light (L) is Iz1, and the intensity of the reflected light (L) is... 反射1 The intensity of the reflected light (L) is Ir1. 反射1 The light is refracted by the concave spherical cavity 141 and then received by the infrared receiver 13. Simultaneously, the refracted light (L...) 折射1 After passing through the water film, the light reaches the interface 2 between the water film and the air, where it is refracted again towards the air side and reflected towards the water film and the glass side. At this point, the refracted light (L) 折射2 The intensity of the reflected light (L) is Iz2, and the intensity of the reflected light (L) is... 反射2 The intensity of ) is Ir2, and the reflected light (L) 反射2 The light passes through the water film and windshield 7, and is refracted by the concave spherical cavity 141 before being received by the infrared receiver 13. The infrared receiver 13 then receives the light sequentially and interacts with the two reflected lights (i.e., L). 反射1 L 反射2 The related optical signals are added together (i.e., L) 反射1 +L 反射2 After being converted into an electrical signal (i.e., a detection signal), it is output to the control device 2 and / or the computing device 3.

[0053] [Control Device 2]

[0054] like Figure 1 As shown, the control device 2 is connected to the water film thickness detection device 1 and sends high-frequency pulse commands (i.e., control signals) to it. Specifically, based on predetermined information and real-time feedback, the control device 2 drives the infrared transmitter 12 and the infrared receiver 13 to emit and receive infrared light at a certain pulse interval T (i.e., frequency), thereby adjusting the detection frequency of the water film thickness detection device 1. For example, the control device 2 determines the initial pulse interval T based on predetermined information such as windshield thickness, water film thickness range, and optical path propagation time. It can also further dynamically adjust the pulse interval T based on real-time feedback from the infrared receiver 13, thereby achieving high-frequency real-time measurement of water film thickness while ensuring that the signals do not overlap. In addition, the control device 2 can also adjust the infrared emission power of the infrared transmitter 12 to optimize the signal-to-noise ratio.

[0055] In this embodiment, the pulse interval T is made to be at least greater than the time taken from the start of infrared light emission from infrared emitter 12 until all reflected infrared light is received by infrared receiver 13, that is, T > t. 0-1 +t1+t 1-2 +t2, where,

[0056] t 0-1 The time it takes for the incident light from infrared emitter 12 to reach interface 1;

[0057] t1: The time it takes for the reflected light from interface 1 to reach infrared receiver 13;

[0058] t 1-2 : The time it takes for the refracted light from interface 1 to reach interface 2;

[0059] t2: The time it takes for the reflected light from interface 2 to reach infrared receiver 13.

[0060] This avoids signal overlap, clearly distinguishes between transmitted and reflected signals, and prevents the superposition of subsequent pulse transmissions and reflections, which could lead to signal aliasing at the receiving end and affect subsequent calculations of water film thickness. Therefore, as long as the time constraint is met, the pulse interval can be shortened as much as possible, thereby enabling high-frequency data acquisition and dynamic display, which is helpful for achieving high-frequency real-time measurement.

[0061] [Computing Device 3]

[0062] The computing device 3 is connected to the control device 2 to acquire the electrical signals output by the infrared receiver 13 of each detection unit 15 in real time, and calculate the water film thickness at the detection unit 15 corresponding to each infrared receiver 13.

[0063] In this embodiment, the electrical signal from the infrared receiver 13 is a signal related to the intensity I of the reflected infrared light. Therefore, the computing device 3 calculates the thickness of the water film at the detection unit 15 based on the intensity I of the reflected infrared light received from a certain detection unit 15, using Snell's law and Beer-Lambert's law, as follows.

[0064] Snell's law describes the relationship between incident and refracted light when light propagates through interfaces of different media (with different refractive indices).

[0065] n1sinθ1=n2sinθ2 where, n1: refractive index of the incident medium, n2: refractive index of the refracting medium, θ1: angle of incidence (angle between the ray and the interface normal).

[0066] θ2: Angle of refraction (the angle between the refracted ray and the normal to the interface)

[0067] The Beer-Lambert law states that when light propagates in a uniform absorbing medium, the intensity of the light decreases with the distance it travels.

[0068] I = I0e -αl

[0069] I0: Incident light intensity

[0070] I: Transmitted light intensity

[0071] α: Absorption coefficient (related to medium and wavelength)

[0072] l: Length (thickness) of the path of light propagation in the medium.

[0073] Therefore, the water film thickness δ is calculated based on the following formula (1):

[0074]

[0075] Where, n1: the refractive index of the glass.

[0076] n2: Refractive index of water

[0077] n3: Refractive index of air; α: Absorption coefficient of water film; λ: Wavelength of infrared light; θ1: Angle of incidence of infrared light onto glass.

[0078] θ3 = arcsin(n2sinθ2).

[0079] r 12 The reflectance coefficient of the glass-water film interface, specifically,

[0080]

[0081] t 12 The transmittance coefficient at the glass-water film interface, specifically,

[0082]

[0083] t 21 The reverse transmission coefficient at the glass-water film interface, specifically,

[0084]

[0085] r 21 The back reflection coefficient at the glass-water film interface, specifically, r 21 =-r 12

[0086] r 23 The reflectance coefficient of the water film-air interface, specifically,

[0087]

[0088] d: Phase delay, specifically, d = 4πn²δcosθ² / λ

[0089] According to the above formula (1), the water film thickness δ at a certain moment is calculated for each detection unit 15. That is, as shown in the formula (1), the water film thickness δ at a certain moment is calculated for each detection unit 15. Figure 5 As shown, in step S1, the control device 2 controls all or part of the infrared emitters 12 of the detection units 15 of the water film thickness detection device 1 to emit infrared light simultaneously, and the infrared light emitted by the infrared emitters 12 is reflected and refracted. In step S2, each infrared receiver 13 corresponding to the aforementioned infrared emitters 12 receives the reflected light, converts it into a signal related to the reflected light, and outputs it. In step S3, after receiving the electrical signals from each infrared receiver 13, the calculation device 3 performs calculations synchronously and separately based on these electrical signals, thereby calculating the water film thickness δ at each detection unit 15. However, the electrical signals received by the calculation device 3 from the infrared receivers 13 of each detection unit 15 are not limited to the infrared reflected light intensity I. For example, they can also be other types of electrical signals representing reflected light, as long as the electrical signals output by the infrared receivers 13 can be converted into the infrared reflected light intensity I required for calculation. In addition, the calculation device 3 does not necessarily have to calculate the water film thickness δ using the above formula. For example, it can also obtain the water film thickness δ at a certain detection unit position through a pre-calibrated mapping relationship between electrical signals and water film thickness. Furthermore, the computing device 3 does not necessarily need to obtain signals through the control device 2; it can also be directly connected to the water film thickness detection device 1 to obtain the signal output by the infrared receiver 13.

[0090] Next, the computing device 3 uses a spatial interpolation algorithm based on the calculated water film thickness (which is a point value at this time) to obtain the water film thickness distribution (which is a continuous value) of the entire measurement area (windshield 7) at this moment. As the spatial interpolation algorithm, any method known in the art can be used, such as inverse distance weighting.

[0091] In step S4, the computing device 3 calculates the clarity index c (1 to 10) based on the water film thickness distribution. Hereinafter, in conjunction with... Figure 6 Detailed explanation.

[0092] In step S41, an optical model is established. As mentioned above, the computing device 3 calculates the water film thickness distribution (i.e., the measured water film thickness distribution) based on the detection results of the water film thickness detection device 1, and then establishes two models using known methods: an optical transmission model for dry windshield and an optical transmission model for wet windshield (water film coverage).

[0093] In step S42, the modulation transfer function (MTF) is calculated. For example, optical simulation software can be used to calculate the MTF (dry) and MTF (wet) for the two optical transfer models described above. The MTF describes the optical system's ability to transmit details at different spatial frequencies. A higher value indicates better sharpness. However, it is not always necessary to use the MTF.

[0094] In step S43, the area under the MTF curve is calculated. For example, as... Figure 7 As shown, the area (S) is obtained by integrating the two MTF curves (dry vs. wet) over the spatial frequency range. MTF(湿润) and S MTF(干燥) (corresponding to respectively) Figure 7 (Red and blue lines are shown in the image). Generally speaking, the larger the area under the MTF curve, the better the overall imaging performance of the optical system.

[0095] In step S44, the area ratio is calculated. Calculate S MTF(湿润) / S MTF(干燥) This allows us to obtain the ratio of image sharpness maintained by wet glass compared to dry glass.

[0096] In step S45, the area ratio is multiplied by 10 to obtain the sharpness index c (i.e., the calculation result). At this point, if the sharpness index c ≈ 10, it means that the wet glass covered by the water film is almost as sharp as the dry glass; if the sharpness index c < 10, it means that the wet glass covered by the water film reduces the sharpness; if the sharpness index c << 10, it means that the wet glass covered by the water film severely reduces the sharpness; if the sharpness index c ≈ 0, it means that the wet glass covered by the water film has almost no sharpness.

[0097] Therefore, by quantifying the decrease in clarity of a wet windshield compared to a dry windshield, a clarity index c is calculated, providing an intuitive numerical indicator to evaluate the impact of wet windshield covered with a water film on clarity.

[0098] Therefore, the windshield clarity measurement system according to this application realizes the objective, quantitative, and real-time measurement of windshield clarity by the water film W.

[0099] However, for the aircraft windshield 7, it is even more preferable to calculate the sharpness index c by differentiating the detection results. Specifically, aircraft cockpits are typically large, and the windshield 7 installed within them is also usually correspondingly large. Pilots have limited visibility and attention spans, making it difficult and unnecessary for them to observe the entire area of ​​the windshield 7 simultaneously and to an equal degree. Therefore, the windshield 7 is usually divided into different viewing zones and considered separately during the design phase. The following example illustrates the method of dividing the viewing zones. Furthermore, since the cockpit windshield 7 includes a left main windshield and a right main windshield, and they are symmetrical, the left main windshield will be used as an example for explanation.

[0100] In this embodiment, specifically, the viewing area of ​​the left main windshield is divided into a first viewing area, a second viewing area, a third viewing area, and a fourth viewing area. For example... Figure 8 , 9 As shown, the first field of view extends 15 degrees to the left and right of the design eye position. The upward direction represents the horizontal plane passing through the design eye position when the aircraft approaches via the steepest approach path. The downward direction represents the limitation given in the field of view range under no precipitation conditions. The first field of view is the minimum range that guarantees a clear field of view under precipitation conditions. The second field of view is the area excluding the first field of view, extending from 20 degrees to the left and 20 degrees to the right of the design eye position. The upward angle of view decreases from 28.3 degrees to 15 degrees above the horizontal reference plane, and the downward angle of view first extends from the horizontal line 17 degrees below the horizontal reference plane to 10 degrees to the right and then linearly decreases to 10 degrees below. The third visual zone is the area excluding the first and second visual zones, as follows: Based on the designed eye position, from 40 degrees to the left and 20 degrees to the right of the vertical reference plane, the upward angle decreases linearly from 35 degrees to 15 degrees above the horizontal reference plane; from 30 degrees to the left and 10 degrees to the right of the vertical reference plane, the downward angle is the horizontal line 17 degrees below the horizontal reference plane; from 10 degrees to the right and 20 degrees to the right of the vertical reference plane, the downward angle decreases linearly to 10 degrees below; from 40 degrees to the left and 80 degrees to the left of the vertical reference plane, the upward angle is the horizontal line 35 degrees above; from 80 degrees to the left and 120 degrees to the left of the vertical reference plane, the upward angle decreases linearly to 15 degrees above; from 30 degrees to the left and 70 degrees to the left of the vertical reference plane, the downward angle increases linearly from 17 degrees to 27 degrees below; from 70 degrees to the left and 95 degrees to the left of the vertical reference plane, the downward angle is the horizontal line 27 degrees below the horizontal reference plane; from 95 degrees to the left and 120 degrees to the left of the vertical reference plane, the downward angle decreases linearly from 27 degrees to 15 degrees below. The fourth viewing area is the remaining area of ​​the windshield excluding the first, second, and third viewing areas. It should be understood that the above method of dividing the viewing area is only a common method in this field and is not limited to using only this method.

[0101] Based on the above division, different weights f are assigned according to the varying requirements for sharpness in different viewing zones. i Weight f iThis, to some extent, reflects the difference in the importance of different visual zones to flight safety. For example, the first visual zone has the highest requirement for sharpness, therefore its weight f is higher. i The weights of the second, third, and fourth viewing zones decrease sequentially, with the fourth viewing zone having the lowest requirement for sharpness, therefore its weight f is relatively high. i Smaller.

[0102] Each detection unit's corresponding detection position (point) is located within a certain viewing area, thus belonging to that viewing area's detection unit. When calculating the sharpness index c, it is calculated separately for each viewing area. Specifically, in this embodiment, viewing areas are pre-divided, and the detection units within each viewing area are pre-defined. Based on the detection results of multiple detection units in each viewing area, the computing device 3 calculates the water film thickness and water film thickness distribution for each viewing area separately, thereby calculating the sharpness index c for each viewing area. i That is, the sharpness index of the first viewing area is c1, the sharpness index of the second viewing area is c2, the sharpness index of the third viewing area is c3, and the sharpness index of the fourth viewing area is c4. Then, according to the weight of each viewing area, the overall sharpness index C of the entire windshield 7 is calculated by weighted summation. The table below is an example.

[0103] First View 0.4 8 3.2 Second View 0.3 6 1.8 Third View 0.2 4 0.8 Fourth View 0.1 3 0.3

[0104] Therefore, the overall clarity index C of the windshield 7 is C = ∑f i c i =6.1.

[0105] [Display Device 4]

[0106] like Figure 1 As shown, the system also includes a display device 4. In this embodiment, the display device 4 is point-connected to the computing device 3 and is used to receive the calculation results transmitted by the computing device 3 and present them intuitively in various forms. For example, the display device 4 receives the water film thickness distribution on the outer surface of the windshield 7 calculated by the computing device 3 in real time and its change over time, and displays it dynamically in the form of a two-dimensional heat map, so that the size and distribution of the water film thickness can be intuitively reflected through color gradients. Furthermore, the display device 4 also displays in real time the sharpness index of the windshield calculated by the computing device 3 based on the water film thickness of each viewing area, including the local sharpness index c of each viewing area. i This also includes the overall clarity index C of the entire windshield. In this embodiment, the display device 4 can be a liquid crystal display, an organic light-emitting diode display, an electronic ink display, a head-up display, or other display components capable of providing the user with information on the measured water film thickness distribution and clarity. In addition, the display device 3 can also overlay and display the clarity change trend curves of each viewing area or a specific viewing area, and provide color warnings or audio-visual prompts when the clarity index is lower than a preset threshold.

[0107] It should be understood that Figure 1 The connections between the devices are shown only as examples, but are not particularly limited as long as the required information can be transmitted between the devices. For example, the computing device 3 can be connected to both the control device 2 and the water film thickness detection device 1. As another example, the control device 2 is connected to the computing device 3 to obtain the calculation results, while the display device 4 is not connected to the computing device 3 but is connected to the control device 2 to obtain the calculation results and display them.

[0108] The following, combined with Figure 10 The method for measuring windshield clarity based on the above system is described below. The method includes the following steps.

[0109] In step S100, a detection device is installed on the aircraft to be tested. Specifically, the water film thickness detection device 1 is stably installed (e.g., by adsorption, adhesion, etc.) on the inner surface of the windshield 7 to be tested, ensuring that the position is fixed and the signal is reliable during the test.

[0110] In step S200, a rain environment is constructed in the laboratory. Specifically, the windshield 7 to be tested and its corresponding enclosure structure are placed in a pre-created rain environment with known rain intensity in the laboratory, thereby simulating the rainfall situation in actual flight under controlled conditions.

[0111] In step S300, data is collected at fixed times and locations. Specifically, the infrared emitter 12 and infrared receiver 13 of the water film thickness detection device 1 are driven by the control device 2 to operate at a specified frequency, and the infrared receiver 13 receives infrared light reflected from the water film on the outer surface of the windshield 7.

[0112] In step S400, the infrared light received by the infrared receiver 13 is converted into an electrical signal and transmitted to the computing device 3 via the control device 2 through a known communication method. However, the electrical signal can also be transmitted directly to the computing device 3.

[0113] In step S500, the sharpness index is calculated in real time. Specifically, the computing device 3 calculates the water film thickness and the corresponding sharpness index of the measurement area of ​​the windshield 7 in real time based on the received electrical signal.

[0114] Furthermore, if necessary, step S600 may be included to further visualize the water film thickness and the corresponding clarity index. Specifically, the calculation results (clarity index) from the computing device 3 can be sent to the display device 4 in real time, and the display device 4 can visualize the results. For example, the display device 4 can visually present the water film thickness and / or its distribution heatmap, as well as the clarity index, etc. Thus, during the wiper rain removal effect test described later, the display device 4 synchronously updates the dynamic changes in the water film thickness distribution and clarity index of the windshield 7, so as to intuitively compare the rain removal effect under different wiper settings.

[0115] Furthermore, if necessary, step S700 can be included to further test the wiper's rain-removing effect. The wiper system is turned on, and different operating modes or speeds are selected for testing. The water film thickness and clarity index, along with their changes, are calculated in real time to confirm the wiper's rain-removing effect. A clarity index closer to 10 indicates a clearer windshield 7, signifying excellent rain-removing performance. Thus, the water film thickness detection device 1 uses high-frequency infrared pulses, and the calculation device 3 performs real-time calculations, easily capturing the transient characteristics of the wiper wiping process, making wiper wiping defects visible, and supporting the optimized design of the wiper system.

[0116] In this embodiment, the real-time calculation results (clarity index) of the computing device 3 can also be sent to the control device 2. The control device 2 stores or exports the data for subsequent analysis and airworthiness certification. Furthermore, by constructing different rain environments in a laboratory, the clarity of the windshield 7 under different rain conditions can be obtained. However, the experimental method is not limited to the above; experiments can also be conducted in real rain environments, measuring clarity while measuring rain intensity, and then performing data comparison and analysis after the experiment.

[0117] In summary, the windshield clarity measurement system and method of the present invention can achieve objective, dynamic, and continuous measurement of the thickness and clarity of the water film on the outer surface of the windshield in simulated rain environments in the laboratory or in real rain environments on the ground. Specifically, by utilizing infrared light and the characteristics of the water film, the water film thickness distribution can be objectively measured through the water film thickness detection device 1, solving the problems of large deviations and low repeatability in traditional subjective evaluation tests. In addition, high-frequency infrared pulse measurement enables high-frequency dynamic continuous detection of the water film thickness, solving the problem that existing technologies cannot capture transient changes and addressing the difficulties in data quantification and analysis in subjective methods. Furthermore, by dividing the windshield into four viewing zones according to the cockpit visibility requirements and assigning different weights, clarity can be calculated regionally, objectively quantifying clarity and further meeting actual needs.

[0118] Furthermore, it should be understood that this application primarily measures the effect of water film formed on the windshield on windshield clarity. The system and method of this application are preferably applied to aircraft, but can also be applied to other situations where clarity measurement under the influence of water film is required, such as helicopters, automobiles, ships, and lookout towers. For example, it can be used to measure the clarity of ship glass during a storm at sea, or to measure the clarity of the windshield of a car traveling on a highway during a severe rainstorm.

[0119] Furthermore, it should be understood that, as mentioned above, a water film will form under conditions of high flight speed, heavy rainfall, or windshield wipers, while stripes of water or raindrops will form under conditions of low speed. The above description in this application mainly concerns the thickness of the water film. By measuring the thickness at each detection point, a spatial interpolation algorithm is used to obtain the continuous water film thickness. However, this application can also measure stripes of water or raindrops, but it is not recommended to use the spatial interpolation algorithm thereafter, as it will lead to distortion of the calculated clarity.

[0120] Furthermore, the instructions mentioned above for performing the aforementioned processes or steps are embodied as computer-executable instructions. Computer-executable instructions can be compiled or interpreted from computer programs created using various programming languages ​​and / or technologies—including, but not limited to, Java™, C, C++, Visual Basic, JavaScript, Perl, HTML, etc., alone or in combination. Generally, a processor (e.g., a microprocessor) receives instructions from memory, computer-readable media, etc., and executes these instructions to perform one or more processes, including one or more processes described herein. Such instructions and other data can be stored and transmitted using various computer-readable media. Files in computing devices are typically collections of data stored on computer-readable media such as storage media, random access memory, etc.

[0121] Furthermore, any process or method description in the flowchart or otherwise described herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0122] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above are merely one specific embodiment of this application and are not limited to the scope of protection of this application. This application can be embodied in various forms without departing from its fundamental characteristics. Therefore, the embodiments described in this application are for illustrative purposes only and not for limitation. Since the scope of this application is defined by the claims rather than the description, and all variations falling within the scope defined by the claims, or their equivalents, should be understood to be included in the claims. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A windshield clarity measurement system, A device for detecting and evaluating the impact of a water film formed on the outer surface of a windshield on the clarity of the windshield, characterized in that... include: A water film thickness detection device is installed on the inner surface of the windshield on the cockpit side. It can emit infrared light in a pulse manner toward the outer surface of the windshield and receive the reflected infrared light as a detection signal. A control device that sends a control signal to the water film thickness detection device, and can drive the water film thickness detection device to emit infrared light at a specified frequency through the control signal; as well as A computing device receives the detection signal from the control device or the water film thickness detection device, and is able to determine a sharpness index characterizing the windshield's clarity as a calculation result based on the detection signal. The detection signal is a signal containing the light intensity of the reflected infrared light. The computing device calculates the water film thickness at the emission position of the infrared light based on the light intensity of the reflected infrared light, calculates the water film thickness distribution based on the calculated water film thickness, and establishes optical transfer models for dry and wet windshields based on the calculated water film thickness distribution. The modulation transfer function and the area under the curve of the modulation transfer function are calculated for the optical transfer models respectively, and the sharpness index of the windshield is determined based on the ratio of the area under the curve.

2. The windshield clarity measurement system according to claim 1, characterized in that, The water film thickness detection device includes: The PCB substrate layer is capable of bending with the curvature of the windshield. Multiple detection units, each including a corresponding infrared emitter and receiver, are independently arranged in a dot matrix on the PCB substrate layer; and An optical cover layer is bonded to the PCB substrate layer in a manner that covers multiple detection units. The infrared emitter emits infrared light. The infrared receiver receives the reflected light along the entire path of the infrared light emitted by the corresponding infrared transmitter.

3. The windshield clarity measuring system according to claim 2, characterized in that, The optical cover layer has a concave spherical cavity formed on the side of the surface that is in contact with the PCB substrate layer, at a position corresponding to the infrared receiver. The optical cover layer is attached to the PCB substrate layer in such a way that it completely covers the infrared emitter and houses the infrared receiver within the concave spherical cavity.

4. The windshield clarity measuring system according to claim 2, characterized in that, The optical coating layer is attached to the inner surface of the windshield on the cockpit side by means of a suction cup structure or adhesive on the side opposite to the PCB substrate layer.

5. The windshield clarity measuring system according to claim 1, characterized in that, The control device generates a high-frequency pulse signal, and drives the water film thickness detection device to emit infrared light in such a way that the pulse interval T is greater than the sum of the time from the emission to the last reflection of the infrared light.

6. The windshield clarity measuring system according to claim 1, characterized in that, The computing device calculates the water film thickness at the emission location of the infrared light based on the intensity of the reflected infrared light, using Snell's law and Beer-Lambert's law.

7. The windshield clarity measuring system according to claim 6, characterized in that, The computing device calculates the water film thickness distribution using a spatial interpolation algorithm based on the calculated water film thickness.

8. The windshield clarity measuring system according to claim 1, characterized in that, The windshield is divided into multiple viewing zones and assigned different weights. The computing device calculates the sharpness index of each view area and obtains the overall sharpness index by weighted summation.

9. The windshield clarity measuring system according to claim 1, characterized in that, It also includes a display device capable of receiving and displaying the calculation results from the computing device.

10. A method for measuring the clarity of a windshield, characterized in that, Performed using the windshield clarity measurement system as described in any one of claims 1 to 9, comprising: The water film thickness detection device is installed on the inner surface of the windshield on the cockpit side; The water film thickness detection device collects infrared reflection signals as detection results in a laboratory-constructed rain environment or a real rain environment; and The computing device calculates the sharpness index in real time based on the detection results as the calculation result.

11. The method for measuring windshield clarity according to claim 10, characterized in that, The display device dynamically presents the results based on the calculation.

12. The method for measuring windshield clarity according to claim 10, characterized in that, Adjust the wiper working mode and confirm the rain removal effect of the wipers by measuring the clarity index of the windshield in real time.

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