Method and apparatus for referencing diffuse reflectance luminance factor

Abstract

The application provides a reference value setting method and device for diffuse reflection luminance coefficient, and focuses on the reference value setting research of the diffuse reflection luminance coefficient in view of the problem that it is difficult to directly measure the diffuse reflection luminance coefficient of a target sample. The method designs a reference value setting device; a positioning light source is used to observe whether the light entering the diffuse hemisphere directly irradiates on the supporting plate, the light spot is adjusted to be filled with the supporting plate or the light spot area outside the supporting plate is less than 10% of the light spot area on the supporting plate by visual observation through adjusting the trapezoidal lens; the sample is placed on the supporting plate, the diffuse illuminance measurer is started, the light intensity I in the integrating sphere is measured, and the diffuse illuminance value E' = I * p is obtained i *z i / R 2 The reflected light measuring module is started, the reflected light luminance L of the sample is measured, and the diffuse reflection luminance coefficient Qd = L / E' is calculated. The method realizes the reference value setting of the diffuse reflection luminance coefficient, can be applied to the measurement of the pre-formed target sample and the target sample, and improves the accuracy and consistency of the daytime visibility evaluation of the target sample.

Description

Technical Field

[0001] This invention belongs to the field of road traffic. Background Technology

[0002] Diffuse reflectance coefficient: Under diffuse lighting conditions, the ratio of the luminance of a specified road traffic marking in a given direction and within a specified area to the vertical illuminance of that area. It reflects the reflectivity of the road traffic marking during the day, and is measured in millicandelas per square meter per lux (mcd / m²). 2 / lx.

[0003] Retroreflection luminance coefficient: Retroreflection refers to the reflection of light that returns from the opposite direction of the incident light. When calculating the retroreflection luminance coefficient, the luminance in the observation direction is divided by the vertical illuminance.

[0004] Road markings play a vital role in channeling traffic, guiding alignment, and ensuring road safety. The visibility of these markings directly impacts driver safety. Domestic standards-setting bodies plan to use the diffuse reflectance luminance coefficient as a key quantitative indicator for evaluating the daytime visibility of road markings. The diffuse reflectance luminance coefficient refers to the ratio of the luminance of a designated road marking in a given direction and area to the vertical illuminance in that area under diffuse lighting conditions. However, currently, only a basic definition of the diffuse reflectance luminance coefficient exists; effective benchmarking methods and devices are lacking. This has hindered its application in evaluating the visibility of road markings, resulting in very little related research and application in China.

[0005] Currently, there is a lack of corresponding technology for the benchmark setting of diffuse reflectance luminance coefficient. However, for the retroreflectance luminance coefficient, which is also an indicator for evaluating the nighttime visibility of road traffic markings, a retroreflectance measurement system is used for benchmark setting. The benchmark setting of retroreflectance luminance coefficient is generally carried out in a large dark room with the optical path open. An illuminance meter is used to measure the normal illuminance on the surface of the retroreflector, and a telemetry photometer or luminance meter is used to measure the luminance of the retroreflector.

[0006] Current technology has the following drawbacks:

[0007] 1) Although both retroreflection luminance coefficient and diffuse luminance coefficient are indicators for evaluating the visibility of road traffic markings, and their units are expressed in the same way, the concepts and definitions of retroreflection luminance coefficient and diffuse luminance coefficient are completely different, making it impossible to use a retroreflection measurement system for benchmark setting. There is no classical theoretical model between retroreflection luminance coefficient and diffuse luminance coefficient, making mathematical derivation and conversion impossible. Summary of the Invention

[0008] This invention establishes a reference value for the diffuse reflectance luminance coefficient, reproducing the concept of the diffuse reflectance luminance coefficient using a specific method and apparatus. The method and apparatus exhibit good reproducibility and can be used to transmit quantitative values ​​of the diffuse reflectance luminance coefficient. The reference value setting accuracy of the diffuse reflectance luminance coefficient achieved by the method and apparatus reaches 0.01 mcd / m. 2 / lx.

[0009] The reference setting device for diffuse reflectance luminance coefficient described in this invention mainly consists of a diffuse illuminance measuring device, a diffuse illuminance measuring probe and data cable, an integrating sphere, an optical fiber, an integrating sphere optical fiber aperture, an optical fiber aperture baffle, a diffuse illuminance measuring aperture, an illuminance aperture baffle, a bulb, a diffuse hemisphere, a diffuse hemisphere optical fiber micro-aperture, an optical fiber micro-aperture light homogenizer, a base, a support platform, a tray, a right-side light trap, a left-side light trap, a reflectance measuring device, a reflectance aperture, a positioning hole, a reflectance measuring hole, a reflectance measuring module, a positioning light source, a trapezoidal lens, a calculation module, a diffuse illuminance data cable, and a reflectance data cable, etc. The hardware connection diagram is shown below. Figure 1 As shown.

[0010] Figure 1 In the diagram, 1 is the diffuse illuminance measuring device, 101 is the diffuse illuminance measuring probe and data cable, 2 is the integrating sphere, 201 is the optical fiber, 202 is the integrating sphere optical fiber aperture, 203 is the optical fiber aperture baffle, 204 is the diffuse illuminance measuring aperture, 205 is the illuminance aperture baffle, 206 is the light bulb, 3 is the diffuse hemisphere, 301 is the diffuse hemisphere optical fiber micro-aperture, 302 is the optical fiber micro-aperture light homogenizer, 4 is the base, 401 is the support platform, 402 is the tray, 403 is the right light trap, 404 is the left light trap, 5 is the reflected light measuring device, 501 is the reflected light aperture, 502 is the positioning hole, 503 is the reflected light measuring hole, 504 is the reflected light measuring module, 505 is the positioning light source, 506 is the trapezoidal probe, 6 is the calculation module, 601 is the diffuse illuminance data cable, and 602 is the reflected light data cable.

[0011] Inside the base, a rectangular tray rests flat on a support platform. The tray is coated with light-absorbing paint or covered with light-absorbing fabric, resulting in a reflectivity of less than 1%. Left and right light traps are located on either side of the tray, absorbing incident light to prevent stray light from interfering with the trapezoidal probe. A diffuser hemisphere covers the tray, the left light trap, and the right light trap. The left light trap is connected to the inner wall of the diffuser hemisphere on the left and the tray on the right; similarly, the right light trap is connected to the inner wall of the diffuser hemisphere on the right and the tray on the left. The side lengths of the left and right light traps are the same as the shorter side of the tray.

[0012] The radius of the diffuse hemisphere is R. Uniformly distributed diffuse hemisphere fiber optic micro-apertures are arranged on the diffuse hemisphere. Behind each diffuse hemisphere fiber optic micro-aperture is a square fiber optic micro-aperture homogenizer, with an illuminance correction coefficient of p. iThe illuminance correction factor for the fiber optic micro-aperture homogenizer is p. i The calculation method involves using an integrating sphere light source connected to the same optical fiber, measuring the illuminance at the fiber's output aperture with a lux meter, connecting the fiber to different fiber micro-aperture light homogenizers, measuring the luminous intensity on the surface of the fiber micro-aperture light homogenizers, and calculating p. i R is the ratio of the luminous intensity on the surface of the fiber optic micro-aperture homogenizer to the illuminance at the fiber's exit aperture. The number of micro-apertures and fibers in the diffuse hemispherical fiber optic system is 1.8πR. 2 / S, where S is the area of ​​the fiber optic micro-aperture homogenizer, and the distance between the micro-apertures in the diffuse hemisphere fiber optic network is... The aperture of the diffuse hemispherical fiber optic microaperture is no larger than After passing through a diffuse hemispherical fiber optic microaperture, the optical fiber is connected to the center of the fiber optic microaperture homogenizer. The illuminance correction factor of the optical fiber is z. i The illuminance correction factor for the optical fiber is z. i The calculation method involves using an integrating sphere light source with a known luminous intensity at its emission point, connecting different optical fibers, measuring the illuminance at the fiber's output aperture with a lux meter, and then calculating z. i This is the ratio of the illuminance at the optical fiber exit aperture to the luminous intensity at the emission point. There is a reflecting aperture on the lower right side of the diffuse hemisphere. The axis of the reflecting aperture points to the center of the diffuse hemisphere. The angle α between the line connecting the center of the reflecting aperture and the center of the diffuse hemisphere and the perpendicular axis passing through the center of the diffuse hemisphere is taken as α. Referring to the geometric conditions for measuring the retroreflection luminance coefficient, α can be taken as 87.71°. A trapezoidal probe is fixed to the diffuse hemisphere through the reflecting aperture. A gap exists between the trapezoidal probe and the reflecting aperture as an observation port. One end of the trapezoidal probe is the probe fiber, and the other end is the trapezoidal lens. Through the trapezoidal lens, the support plate can be seen to fill the entire field of view. At this time, the extended surfaces of the upper and lower sides of the trapezoidal lens intersect the left and right short sides of the support plate, respectively. The extended surfaces of the two inclined sides of the trapezoidal lens, perpendicular to the paper and pointing inwards and outwards, intersect the two long sides of the support plate, perpendicular to the paper and pointing inwards and outwards, respectively.

[0013] To achieve a brightness deviation of less than 1% on different fiber optic micro-aperture homogenizers, the correction coefficient p of the fiber and the fiber optic micro-aperture homogenizer at different locations is required. i *z i The value deviation should not be less than 1%. The most convenient option is to change the length of the optical fiber. The correction factor z of the optical fiber is... i This is the ratio of the illuminance at the fiber optic exit aperture to the luminous intensity at the emission point, and the illuminance at the fiber optic exit aperture is related to the fiber length. It can also be achieved by replacing the fiber with a different material or a fiber optic micro-perforation diffuser. Furthermore, it can be achieved by replacing different combinations of fibers and fiber optic micro-perforation diffusers.

[0014] The reflective light measuring device has a reflective light measurement hole on the left outer wall, behind which is the reflective light measurement module. There is a positioning hole on the right outer wall, behind which is the positioning light source. The optical fiber at one end of the trapezoidal probe can be installed either on the reflective light measurement hole or on the positioning hole.

[0015] The integrating sphere has an inner wall coated with a diffuse reflective coating. Inside the integrating sphere, there is an integrating sphere fiber optic opening at the top, inside which a fiber optic baffle is installed. A diffuse illuminance measurement opening is located on the side, inside which an illuminance baffle is installed. A light bulb is installed at the center of the integrating sphere; this bulb can be a D65 light source, an A light source, or another type of light source. When the bulb is not a D65 light source, the diffuse illuminance meter and the reflected light meter should be the same photometer. The diffuse illuminance measurement probe and data cable are installed at the diffuse illuminance measurement opening and connected to the diffuse illuminance meter. Both the illuminance baffle and the fiber optic baffle are coated with a diffuse reflective coating. The reflectivity of the diffuse reflective coating on the inner wall of the integrating sphere is the same as the reflectivity of the diffuse reflective coating on the illuminance baffle and the fiber optic baffle.

[0016] The diffuse illuminance measuring device transmits diffuse illuminance data to the computing module via a diffuse illuminance data line, and the reflected light measuring module transmits reflected light data to the computing module via a reflected light data line. The computing module can be a computer, a microcontroller, an FPGA, or other unit capable of data computation. The diffuse illuminance data line and the reflected light data line can also be wireless data transmission modules.

[0017] The reference setting device for the diffuse reflection luminance coefficient described in this invention mainly consists of a diffuse illuminance measuring device, a diffuse illuminance measuring probe and data cable, an integrating sphere, an optical fiber, an integrating sphere optical fiber aperture, an optical fiber aperture baffle, a diffuse illuminance measuring aperture, an illuminance aperture baffle, a light bulb, a diffuse hemisphere, a diffuse hemisphere optical fiber micro-aperture, an optical fiber micro-aperture light homogenizer, a base, a support platform, a tray, a right-side light trap, a left-side light trap, a reflected light measuring device, a reflected light aperture, a positioning hole, a reflected light measuring hole, a reflected light measuring module, a positioning light source, a trapezoidal lens, a calculation module, a diffuse illuminance data cable, and a reflected light data cable.

[0018] The overall technical solution implementation process is as follows:

[0019] (1) Connect the components according to the hardware connection diagram, disconnect the fiber optic cable from the integrating sphere, turn on the bulb inside the integrating sphere, and preheat it according to the bulb's instruction manual.

[0020] (2) If the light bulb has just been turned on, a self-test is required to determine whether the tray can be seen to fill the entire field of view through the trapezoidal lens.

[0021] (3) The first step of self-test is to install the probe fiber onto the positioning hole.

[0022] (4) The second step of self-test is to turn on the positioning light source and let the light pass through the trapezoidal lens along the probe optical fiber and into the diffuse hemisphere. Using the gap between the trapezoidal probe and the reflective aperture as the observation port, observe whether the light entering the diffuse hemisphere directly illuminates the tray, that is, whether the light spot exactly fills the tray.

[0023] (5) Self-inspection step 3: If the tray is not completely filled by the light spot, or the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray, the focal length of the trapezoidal lens should be adjusted so that the light spot just fills the tray, or the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray.

[0024] (6) After completing the self-test, turn off the positioning light source.

[0025] (7) Install the probe fiber onto the reflected light measurement hole and connect the fiber to the fiber opening on the integrating sphere.

[0026] (8) Place the sample on the tray. The area of ​​the sample is generally the same as the area of ​​the tray, so the sample should coincide with the tray when placing it. If the area of ​​the sample is smaller than the tray, the center of the sample should coincide with the center of the tray, and the four sides of the sample should be parallel to the four sides of the tray.

[0027] (9) Start the measurement. First, start the diffuse illuminance meter to measure the light intensity I inside the integrating sphere, and calculate the diffuse illuminance value E' = I * p. i *z i / R 2 R is the radius of the diffuse hemisphere. Then, activate the reflected light measurement module to measure the brightness L of the light reflected from the sample at an observation angle of 90°-α.

[0028] (10) The calculation module performs the calculation. Based on the data E' transmitted by the diffuse illuminance meter and the data L transmitted by the reflected light measurement module, the diffuse reflectance luminance coefficient Qd = L / E' is calculated.

[0029] (11) Qd is the result required for measurement, and the baseline value of the diffuse reflectance luminance coefficient has been achieved. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the device of the present invention.

[0031] Figure 2 This is a schematic diagram of the method of the present invention.

[0032] Figure 3 This is a partial schematic diagram of the device of the present invention. Detailed Implementation

[0033] This invention utilizes a diffuse illuminance measuring device, a diffuse illuminance measuring probe and data cable, an integrating sphere, an optical fiber, an integrating sphere optical fiber aperture, an optical fiber aperture baffle, a diffuse illuminance measuring aperture, an illuminance aperture baffle, a light bulb, a diffuse hemisphere, a diffuse hemisphere optical fiber micro-aperture, an optical fiber micro-aperture light homogenizer, a base, a support platform, a tray, a right-side light trap, a left-side light trap, a reflected light measuring device, a reflected light aperture, a positioning hole, a reflected light measuring hole, a reflected light measuring module, a positioning light source, a trapezoidal lens, a calculation module, a diffuse illuminance data cable, and a reflected light data cable to form a reference setting device for the diffuse reflectance luminance coefficient.

[0034] The reference value determination method for diffuse reflectance luminance coefficient proposed in this invention enables direct measurement of diffuse reflectance luminance coefficient.

[0035] This invention uses an integrating sphere to generate uniform light, which is then uniformly guided into a diffuse hemisphere via an optical fiber. A micro-aperture optical fiber homogenizer further homogenizes the light guided through the fiber, with a 1.8πR ratio. 2 / S fiber micro-aperture light homogenizers form an approximate hemisphere within the diffuse hemisphere, providing an active, diffuse illumination environment for the marking sample. Ambient light is unaffected by reflected light; that is, the change in light intensity within the diffuse hemisphere is less than 1% when the marking sample is placed inside or outside the diffuse hemisphere. In contrast, the illumination environment generated within a typical integrating sphere is easily affected by objects placed inside it, especially when the reflectivity of the object differs significantly from the reflectivity of the diffuse reflective coating on the inner wall of the integrating sphere. If the difference exceeds 10%, the resulting diffuse illumination environment becomes unstable.

[0036] The trapezoidal lens, left light trap, and right light trap reduce stray light—that is, the situation where reflected light not originating from the marking sample is measured by the reflected light measuring instrument—reducing the uncertainty component introduced by stray light by 1%. Specifically, since the long side of the support plate is larger than its short side, the shape of the light spot on the plane of the support plate after light exits the lens differs from that of the lens. In particular, the size of the light spot along the long side of the support plate is significantly larger than that of the lens in this direction, while the size of the light spot along the corresponding short left side of the support plate is significantly larger than that along the short right side. To ensure that the light spot covers the support plate and the area exceeding the support plate is no more than 10%, thus reducing the measurement error caused by stray light entering the lens during measurement, this invention proposes a trapezoidal lens to solve this problem. The upper side of the trapezoidal lens is aa, the lower side is bb, and the hypotenuse is cc. The short side of the support plate is dd, and the long side is ee. The distance from the lower side of the trapezoidal lens to the short right side of the support plate is l. aa<bb, cc / ee≈sin(90°-α), dd≈2*l*sin0.165°+bb, dd≈aa+2*sin0.165°*(l+ee*cos0.165°), bb≈aa+2ee*sin0.165°*cos0.165°. The right and left light traps at both ends of the support plate absorb the light incident on both ends of the support plate during measurement, preventing unwanted reflected light from entering the trapezoidal lens.

[0037] By examining the situation where the light emitted from the positioning light source passes through the trapezoidal lens and covers the tray, the situation where the light reflected from the marking sample enters the trapezoidal lens during the measurement of the marking sample was simulated in reverse, thus solving the problem of determining the range of reflected light entering the trapezoidal lens during measurement.

[0038] The light propagation of the device takes place in enclosed cavities such as integrating spheres and diffuse hemispheres. Therefore, this invention does not rely on a darkroom, and the ambient light in the laboratory will not affect the measurement results. The device can be placed in any laboratory, and the baseline value of the diffuse reflectance luminance coefficient can be determined according to the method.

[0039] (1) Connect the components according to the hardware connection diagram, disconnect the fiber optic cable and the integrating sphere, turn on the D65 light source inside the integrating sphere, and preheat the D65 light source according to the instruction manual.

[0040] (2) If the D65 light source has just been turned on, a self-test is required, that is, observe whether the tray can be seen to fill the entire field of view through the trapezoidal lens.

[0041] (3) The first step of self-test is to install the probe fiber onto the positioning hole.

[0042] (4) The second step of the self-test is to turn on the positioning light source, allowing the light to enter the trapezoidal lens along the probe's optical fiber and shine into the diffuse hemisphere. Using the gap between the trapezoidal probe and the reflecting aperture as the observation port, with the gap area less than half the area of ​​the trapezoidal probe, observe whether the light entering the diffuse hemisphere directly illuminates the support plate, i.e., whether the light spot exactly fills the support plate. The light spot area can be slightly larger than the support plate area, but should not exceed 10%. Alternatively, a separate observation hole can be opened on the diffuse hemisphere for observation.

[0043] (5) In the third self-inspection step, if the tray is not completely filled by the light spot, or if the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray, the focal length of the trapezoidal lens should be adjusted so that the light spot just fills the tray, or the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray. The self-inspection step, by checking the situation where the light emitted from the positioning light source covers the tray through the trapezoidal lens, reversely simulates the situation where the light reflected from the marking sample enters the trapezoidal lens when measuring the marking sample, thus solving the problem of difficulty in determining the range of reflected light entering the trapezoidal lens during measurement. The long side of the tray is larger than the short side. After the light is emitted from the lens, the shape of the light spot on the plane where the tray is located is different from that of the lens. In particular, the size of the light spot in the direction of the long side of the tray is larger than that of the lens in this direction, while the size of the light spot on the short side of the left side of the tray is larger than that on the short side of the right side of the tray. In order to make the light spot cover the tray and the area exceeding the tray is no more than 10%, and to reduce the measurement error caused by stray light entering the lens during measurement, this invention proposes a trapezoidal lens to solve this problem. The top edge of the trapezoidal lens is aa, the bottom edge is bb, and the hypotenuse is cc. The short side of the support plate is dd, and the long side is ee. The distance from the bottom edge of the trapezoidal lens to the right short side of the support plate is l. aa < bb, cc / ee ≈ sin(90° - α), dd ≈ 2 * l * sin0.165° + bb, dd ≈ aa + 2 * sin0.165° * (l + ee * cos0.165°), bb ≈ aa + 2ee * sin0.165° * cos0.165°. The light traps on the right and left sides of the support plate absorb the light incident on both ends of the support plate during measurement, preventing unwanted reflected light from entering the trapezoidal lens.

[0044] (6) After completing the self-test, turn off the positioning light source. Wait for the D65 light source to complete its 10-minute preheating.

[0045] (7) Install the probe fiber onto the reflected light measurement hole, connect the fiber to the fiber opening on the integrating sphere, and the beam enters the diffuse hemisphere to form a uniform light field. The brightness deviation on different fiber micro-aperture light homogenizers is less than 1%.

[0046] (8) Place the marking sample on the support plate. The area p of the marking sample is generally the same as the area of ​​the support plate, and the long and short sides of the marking sample are the same as the long and short sides of the support plate. Therefore, the marking sample should coincide with the support plate when placed. If the area of ​​the marking sample is smaller than the support plate, that is, the four sides of the marking sample and the support plate are different, the center of the marking sample should coincide with the center of the support plate, and the four sides of the marking sample should be parallel to the four sides of the support plate. The marking sample can be positioned by measuring the distance from the four sides of the marking sample to the four sides of the support plate. If the distance from the two short sides to the short side of the support plate is the same, and the distance from the two long sides to the long side of the support plate is the same, then the center of the marking sample and the center of the support plate are considered to coincide.

[0047] (9) Start the measurement. First, start the diffuse illuminance meter and measure the light intensity I inside the integrating sphere. Take 10 consecutive measurements and use the arithmetic mean as the result. Calculate the diffuse illuminance value E'≈I*p. i *z i / R 2 R is the radius of the diffuse hemisphere.

[0048] (10) Restart the reflected light measurement module. The reflected light measurement module can be used for brightness measurement or illuminance measurement. At this time, light entering the diffuse hemisphere from the integrating sphere illuminates the marking sample from various angles. The marking sample reflects light at different incident angles. Under the condition of observation angle (90°-α), part of the reflected light enters the trapezoidal lens. The reflected light measurement module measures the brightness L of the light reflected by the marking sample under this condition. The measurement is repeated 10 times, and the arithmetic mean is taken as the result. Alternatively, instead of measuring brightness L, the reflected illuminance E2 can be measured.

[0049] (11) The calculation module performs the calculation. Based on the data E' transmitted by the diffuse illuminance meter and the data L transmitted by the reflected light measurement module, the diffuse reflectance luminance coefficient Qd = L / E' of the marking sample is calculated. When the reflected light measurement module measures the reflected illuminance E2, the diffuse reflectance luminance coefficient Qd = R of the marking sample is calculated. 2 *E2 /

[0050] (p*E'*cos(90°-α)).

[0051] (12) Qd is the result required for measurement, and the measurement of the diffuse reflectance luminance coefficient of the marking sample is thus achieved.

[0052] This invention enables the measurement of the diffuse reflectance luminance coefficient of road marking samples using a direct measurement method. It is the first time a benchmark value for the diffuse reflectance luminance coefficient has been established, concretely reproducing the concept of the diffuse reflectance luminance coefficient through a specific method and device. This establishes a traceable source for the measurement of diffuse reflectance luminance coefficient in the highway transportation field. This invention can provide a benchmark value for others developing portable diffuse reflectance luminance coefficient measuring equipment for road marking samples, and provides technical possibilities for the development of new equipment.

[0053] When light shines from the lens onto the support plate, since the light is emitted parallel from the lens, conversely, the parallel light reflected from the support plate must also enter the lens precisely, and light from other positions should not enter the lens to avoid noise affecting the measurement results. Based on geometric relationships, the invention designs the lens as a trapezoid, satisfying the geometric dimensional conditions so that the light reflected from the rectangular position where the support plate is located can completely fill the trapezoidal lens. The geometric relationships that satisfy this requirement are: aa<bb, cc / ee≈sin(90°-α), dd≈2*l*sin0.165°+bb, dd≈aa+2*sin0.165°*(l+ee*cos0.165°), bb≈aa+2ee*sin0.165°*cos0.165°. The central axis of the trapezoidal lens must pass through the center point of the diffuse hemisphere, which is also the center point of the support plate or the sample. A trapezoidal lens can be obtained through design. However, due to assembly issues, even if the fabricated trapezoidal lens and the support plate (or sample) meet these geometric relationships, insufficient assembly precision may cause some light to enter the trapezoidal lens from both ends of the support plate. Furthermore, since some light from the ends of the support plate is not parallel to the central axis of the trapezoidal lens, it may still enter the lens due to its position. Therefore, right-side and left-side light traps are placed at both ends of the support plate to absorb the light incident on both ends during measurement, preventing unwanted reflected light from entering the trapezoidal lens. Simultaneously, a positioning light source was designed. When not measuring, light is reflected onto the probe and falls on the tray or sample. Based on the resulting light spot, the trapezoidal lens position is fine-tuned. If the tray is not completely filled with the light spot, or if the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray (meaning the area of ​​the light spot on the tray is less than 90% of the total light spot area), the focal length of the trapezoidal lens should be adjusted so that the light spot exactly fills the tray. If the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray (meaning the area of ​​the light spot on the tray is greater than 90% of the total light spot area), no further adjustment is needed. This reduces noise entering the trapezoidal lens during detection.

[0054] Because the light entering through a single diffuse hemispherical fiber micro-aperture is a point source, a large hemispherical light source is needed. If the light source were simply composed of points, the fiber density would be too high, requiring significant bending and potentially causing fiber breakage, making it impossible to create such a sphere. To reduce the number of fibers, square fiber micro-aperture light-diffusing sheets were designed. Several square fiber micro-aperture light-diffusing sheets of the same area can be joined together to form an approximate hemisphere. The fiber micro-aperture light-diffusing sheet is connected to an optical fiber, and its four sides are connected to other fiber micro-aperture light-diffusing sheets, forming an approximate hemisphere within the diffuse hemisphere. The approximate hemisphere formed by the fiber micro-aperture light-diffusing sheets and the diffuse hemisphere are mainly connected by optical fibers, and at the bottom edges of the diffuse and approximate hemispheres, welding and other processes are used to connect the approximate hemisphere and the diffuse hemisphere.

[0055] Ensuring uniform light intensity across all light rays on the inner wall of a diffuse hemisphere, resulting in a homogeneous light field distribution, is challenging. To achieve this, a method was invented that creates several diffuse hemisphere fiber optic micro-apertures. Behind each micro-aperture is a square fiber optic micro-aperture homogenizer. The spacing between these micro-apertures is identical, and all are connected to an outer fiber optic cable, which in turn connects to a common light-emitting aperture on an outer integrating sphere. The number of both the diffuse hemisphere fiber optic micro-apertures and the number of fibers is 1.8πR. 2 / S, the distance between the micro-apertures in the diffuse hemispherical fiber is S represents the area of ​​the fiber optic micro-aperture homogenizer. The diameter of the diffuse hemispherical fiber optic micro-aperture is generally no larger than [missing information].

[0056] 87.71° is the observation angle obtained based on the classic road observation model. At this angle, the angle between the line formed by the human eye observing the road marking and the normal of the marking is 87.71°, while the angle between the line formed by the human eye observing the road marking and the straight line between the projection of the human's position and the observed marking is 2.29°.

[0057] The illuminance correction factor for the optical fiber is z. i The calculation method involves using an integrating sphere light source with a known luminous intensity at its emission point, connecting different optical fibers, measuring the illuminance at the fiber's output aperture with a lux meter, and then calculating z. i It is the ratio of the illuminance at the optical fiber's output aperture to the luminous intensity at the emission point.

[0058] The illuminance correction factor for the fiber optic micro-aperture homogenizer is p. i The calculation method involves using an integrating sphere light source connected to the same optical fiber, measuring the illuminance at the fiber's output aperture with a lux meter, connecting the fiber to different fiber micro-aperture light homogenizers, measuring the luminous intensity on the surface of the fiber micro-aperture light homogenizers, and calculating p. iIt is the ratio of the luminous intensity on the surface of the fiber micro-aperture homogenizer to the illuminance at the fiber exit aperture.

[0059] To achieve a brightness deviation of less than 1% on different fiber optic micro-aperture homogenizers, the correction coefficient p of the fiber and the fiber optic micro-aperture homogenizer at different locations is required. i *z i The value deviation should not be less than 1%. The most convenient option is to change the length of the optical fiber. The correction factor z of the optical fiber is... i This is the ratio of the illuminance at the fiber optic exit aperture to the luminous intensity at the emission point, and the illuminance at the fiber optic exit aperture is related to the fiber length. It can also be achieved by replacing the fiber with a different material or a fiber optic micro-perforation diffuser. Furthermore, it can be achieved by replacing different combinations of fibers and fiber optic micro-perforation diffusers.

[0060] This invention has excellent applicability and can be applied to the measurement of pre-formed road marking tape samples, road marking blocks cut from actual roads, and road marking samples prepared by other methods.

[0061] Prior to this invention, there was a lack of reasonable methods for evaluating the daytime visibility of road traffic markings, and visual assessment was often the primary method. Domestic standards-setting organizations planned to use the diffuse reflectance luminance coefficient as an important quantitative indicator for evaluating the daytime visibility of road traffic markings. This invention uses quantifiable methods and devices to achieve quantitative measurement, improving the accuracy and consistency of evaluating the daytime visibility of road traffic markings and standardizing the quantitative value of the diffuse reflectance luminance coefficient for road markings.

[0062] This invention can promote the scientific maintenance of road traffic markings and save on the maintenance costs of road traffic markings.

Claims

1. A reference setting device for diffuse reflectance luminance coefficient, characterized in that: Inside the base, a rectangular tray rests flat on the support platform. The tray is coated with light-absorbing paint or covered with light-absorbing velvet, making its reflectivity less than 1%. The left and right light traps are located on both sides of the tray, respectively. The left and right light traps are used to absorb the light incident upon them, so that the probe is not interfered with by stray light from outside the tray. A diffuse hemisphere is located on the tray, the left light trap, and the right light trap. The left light trap is connected to the inner wall of the diffuse hemisphere on the left and the tray on the right. The right light trap is connected to the inner wall of the diffuse hemisphere on the right and the tray on the left. The side lengths of the left and right light traps are the same as the short side of the tray. The radius of the diffuse hemisphere is R; uniformly distributed on the diffuse hemisphere are diffuse hemispherical fiber micro-apertures; behind each diffuse hemispherical fiber micro-aperture is a square fiber micro-aperture beam leveling plate. The number of diffuse hemispherical fiber micro-apertures and fibers is 1.8πR. 2 / S, where S is the area of ​​the fiber optic micro-aperture homogenizer, and the distance between the micro-apertures in the diffuse hemisphere fiber optic network is... The aperture of the diffuse hemispherical optical fiber micropore is no larger than / 6; The optical fiber passes through the fiber micro-aperture of the diffuse hemisphere and is connected to the center of the fiber micro-aperture homogenizer. There is a reflective aperture on the lower right side of the diffuse hemisphere. The axis of the reflective aperture points to the center of the diffuse hemisphere. The angle between the line connecting the center point of the reflective aperture and the center of the diffuse hemisphere and the vertical axis perpendicular to the center of the diffuse hemisphere is α, which is 87.71°. The probe passes through the reflective aperture and is fixed on the diffuse hemisphere. There is a gap between the probe and the reflective aperture as an observation port. One end of the probe is the probe fiber, and the other end is a trapezoidal lens. Through the trapezoidal lens, the tray can be seen to fill the entire field of view. At this time, the extended surfaces of the upper and lower sides of the trapezoidal lens intersect the left and right short sides of the tray, respectively. The extended surfaces of the two inclined sides of the trapezoidal lens perpendicular to the paper and ...

2. The apparatus as described in claim 1, characterized in that: The top side of the trapezoidal lens is aa, the bottom side is bb, and the hypotenuse is cc; the short side of the support plate is dd, and the long side is ee; the distance from the bottom of the trapezoidal lens to the right short side of the support plate is l; aa<bb, cc / ee≈sin(90°-α), dd≈2*l*sin0.165°+bb, dd≈aa+2*sin0.165°*(l+ee*cos0.165°), bb≈aa+2ee*sin0.165°*cos0.165°.

3. The method using the apparatus as described in claim 1, characterized in that: The illuminance correction factor for the fiber optic micro-aperture homogenizer is p. i The calculation method involves using an integrating sphere light source connected to the same optical fiber, measuring the illuminance at the fiber's output aperture with a lux meter, connecting the fiber to different fiber micro-aperture light homogenizers, measuring the luminous intensity on the surface of the fiber micro-aperture light homogenizers, and calculating p. i It is the ratio of the luminous intensity on the surface of the fiber micro-aperture homogenizer to the illuminance at the fiber exit aperture; The illuminance correction factor for the optical fiber is z. i The calculation method involves using an integrating sphere light source with a known luminous intensity at its emission point, connecting different optical fibers, measuring the illuminance at the fiber's output aperture with a lux meter, and then calculating z. i It is the ratio of the illuminance at the optical fiber's output aperture to the luminous intensity at the emission point; To achieve a brightness deviation of less than 1% on different fiber optic micro-aperture homogenizers, the illuminance correction coefficient p of the fiber and the fiber optic micro-aperture homogenizer at different locations is required. i *z i The value deviation should not be less than 1%, and the most convenient option is to change the length of the optical fiber. On the reflective light measuring device, there is a reflective light measuring hole on the left outer wall, behind which is the reflective light measuring module; there is a positioning hole on the right outer wall, behind which is the positioning light source; the probe fiber at one end of the probe can be installed on either the reflective light measuring hole or the positioning hole. The inner wall of the integrating sphere is coated with a diffuse reflection paint. Inside the integrating sphere, there is an integrating sphere fiber optic opening at the top, inside which a fiber optic baffle is installed. On the side, there is a diffuse illuminance measurement opening, inside which an illuminance baffle is installed. A light bulb is installed in the center of the integrating sphere. The diffuse illuminance measurement probe and data cable are installed at the diffuse illuminance measurement opening and connected to the diffuse illuminance measuring device. The diffuse illuminance measuring device transmits diffuse illuminance data to the calculation module via the diffuse illuminance data cable, and the reflected light measurement module transmits reflected light data to the calculation module via the reflected light data cable.

4. The method as described in claim 3, characterized in that: (1) Connect the components according to the hardware connection diagram, disconnect the fiber optic cable from the integrating sphere, turn on the bulb inside the integrating sphere, and preheat it according to the bulb's instruction manual; (2) If the light bulb has just been turned on, a self-test is required to determine whether the tray can be seen to fill the entire field of view through the trapezoidal lens. (3) The first step of self-test is to install the probe fiber onto the positioning hole; (4) Self-inspection step 2: Light up the positioning light source and let the light pass through the lens along the probe fiber and into the diffuse hemisphere; use the gap between the probe and the reflective light hole as the observation port to observe whether the light entering the diffuse hemisphere directly shines on the tray, that is, whether the light spot just fills the tray. (5) In the third step of self-inspection, if the tray is not completely filled by the light spot, or the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray, the focal length of the trapezoidal lens should be adjusted so that the light spot just fills the tray, or the area of ​​the light spot outside the tray is visually larger than 10% of the area of ​​the light spot on the tray. (6) After completing the self-test, turn off the positioning light source; (7) Install the probe fiber onto the reflected light measurement hole and connect the fiber to the fiber optic opening on the integrating sphere; (8) Place the sample on the tray. The area of ​​the sample is generally the same as the area of ​​the tray, so the sample should coincide with the tray when it is placed. If the area of ​​the sample is smaller than the tray, the center of the sample should coincide with the center of the tray, and the four sides of the sample should be parallel to the four sides of the tray. (9) Start the measurement; first start the diffuse illuminance meter, measure the light intensity I inside the integrating sphere, and calculate the diffuse illuminance value E'=I*p i *z i / R 2 R is the radius of the diffuse hemisphere; then start the reflected light measurement module to measure the brightness L of the light reflected by the sample at the observation angle of 90°-α; (10) The calculation module performs the calculation; based on the data E' transmitted by the diffuse illuminance meter and the data L transmitted by the reflected light measurement module, the diffuse reflectance luminance coefficient Qd=L / E' is calculated; (11) Qd is the result required for measurement, and the baseline value of the diffuse reflectance luminance coefficient has been achieved.

Images