Method and apparatus for measuring glare in etc gantry lighting

Abstract

An apparatus for measuring glare in ETC gantry lighting, which apparatus belongs to the field of highway ambient lighting detection. The apparatus comprises a locator (1), a reflected signal demodulator (3-1), a reflected signal sensor (3-2), a transmitted signal modulator (4-1), a signal transmitter (4-2), a transmitted signal demodulator (5-1), a transmitted signal sensor (5-2), a transmissive-reflective mirror set (6), detectors (7, 8), an upper vertical illuminance detector (9), cameras (10, 11, 12), and a switcher (14). Further provided is a method for measuring glare in ETC gantry lighting. The reflectance and luminance of the ground below an ETC gantry are measured to obtain a ground luminance calculation formula, so as to realize the acquisition of ground luminance at a short distance, thereby solving the problems of there being relatively excessive external stray light interference caused by the use of a luminance meter, etc. for long-distance luminance measurement, and the measurement accuracy of the luminance meter decreasing when the distance is relatively long; moreover, by means of supplementary light luminance at different orders of magnitude which are acquired by means of switcher blades having different light transmittances, integrating with the sensitivity advantages of left and right cameras in a high luminance region and a low luminance region, a system error is reduced, thereby obtaining an accurate comprehensive illuminance value.

Description

A method and apparatus for measuring glare from ETC gantry lighting Technical Field

[0001] This invention belongs to the field of highway environmental lighting detection. Background Technology

[0002] Threshold increment: When glare occurs, the percentage increase in contrast between an object and its background is required to achieve the same good viewing conditions. It is commonly represented by TI and is a quantitative indicator of glare from lighting fixtures such as streetlights and ETC gantry supplementary lights.

[0003] ETC gantry lighting: This system uses lighting fixtures within the ETC gantry system to alter the ambient light around the gantry, enabling the monitoring equipment within the system to accurately capture license plate information or in-vehicle images. These lighting fixtures typically include supplementary lighting devices for automatic license plate video recognition and supplementary lighting devices for traffic technology monitoring imaging; they can be collectively referred to as supplementary lighting.

[0004] With the completion of the national transportation power construction and the deepening of toll road system reform, including the elimination of provincial toll stations on expressways, ETC gantry systems have been widely adopted. Among these systems, supplementary lighting systems are an important component of the ETC gantry image recognition and monitoring system.

[0005] Traffic technology monitoring imaging supplementary lighting device is installed on ETC gantry, at a vertical height of 6m from the target road. The supplementary lighting device is installed on the upper side of the target road. The spatial angle between the reference axis of the traffic technology monitoring imaging supplementary lighting device and the dividing line between the two roads is equal to 20°, and one device is installed per lane.

[0006] The automatic video recognition supplementary lighting device for highway vehicle license plates is installed on the ETC gantry at a vertical distance of 6.5m from the target road, directly above the center line of the target road, with one device installed per lane.

[0007] In Figure 3, S1 represents the target road, S2 is the ETC gantry, S4 is the road adjacent to the target road, S9 is the boundary line between the two roads, S5 is the automatic video recognition supplementary lighting device for highway vehicle license plates, S6 is the traffic technology monitoring imaging supplementary lighting device, S8 is the reference axis of the traffic technology monitoring imaging supplementary lighting device, and S7 is the centerline of the target road. α is the spatial angle between the reference axis of the traffic technology monitoring imaging supplementary lighting device and the boundary line between the two roads, with a value of 20°.

[0008] However, during the operation of the ETC gantry system, glare caused by inappropriate selection and installation of nighttime lighting systems, especially supplementary lights, has sparked heated discussions. At high speeds, temporary blindness caused by glare from malfunctioning ETC gantry lighting systems can lead to serious traffic accidents. Glare from supplementary lights has become a hot topic. In 2021, in response to public concerns, the Ministry of Transport organized nationwide monitoring of highway networks and inspections of gantry equipment, urging some provinces to further optimize gantry supplementary lights to mitigate the impact of light intensity on nighttime driving comfort within a certain distance.

[0009] Glare is a visual state caused by inappropriate brightness distribution or range in the field of vision, or by extreme brightness contrast, resulting in discomfort or reduced ability to observe targets or details. Based on its effects, glare can be classified into uncomfortable glare and disabling glare. Glare is essentially a product of photometry and optometry, primarily manifesting as a physiological response of the human eye to changes in external light. Research shows that prolonged exposure to poorly lit environments, such as inappropriate illuminance, uneven light distribution, and excessive glare, poses serious health risks. Therefore, accurate glare measurement can effectively prevent and avoid safety problems.

[0010] Glare in road lighting is often quantitatively characterized by threshold increments. Recently, researchers have also proposed using threshold increments to characterize the glare level of ETC gantry supplementary lights. Currently, there is no commercially available technical solution for measuring glare from ETC gantry supplementary lights. Similar technical solutions can be used to measure glare from road streetlights. Traditional glare measurement methods combine measurements with conventional equipment such as lux meters, luminance meters, and measuring tapes. Because lux meters and luminance meters have slow response times, measurements must be taken in a stationary state. Another method involves using dedicated software to control a camera to measure glare from streetlights, or using dedicated software to control an imaging luminance meter to measure glare from streetlights, and then using a position measuring device to calculate the threshold increment. Such equipment is also known as a glare tester.

[0011] Current technology has the following drawbacks:

[0012] 1) Current technology cannot measure the glare of ETC gantry supplementary lights. The placement of ETC gantry supplementary lights is completely different from that of streetlights. ETC gantry supplementary lights are installed above the gantry spanning the road, while streetlights are installed on the roadside. ETC gantry supplementary lights are electromechanical facilities on highways, where there are no streetlights and the road surface brightness is very low, generally not exceeding 0.5 cd / m². 2 Streetlights are electromechanical facilities on the road. Due to the illumination from adjacent streetlights, the ground brightness is relatively high, at 1.5 cd / m². 2Therefore, the effects of ETC gantry supplementary lights and street light glare on drivers' vision are completely different.

[0013] 2) Currently, conventional glare testing instruments perform static measurements, meaning they are stationary several meters away from the streetlight being tested, take a still image, calculate the brightness at different points on the image, and finally obtain the threshold increment for the streetlight. This necessitates closing roads for glare measurement, affecting normal traffic flow.

[0014] 3) The operation process is cumbersome, time-consuming, and involves a large amount of data. The operation requires manual real-time point measurement, and the measurement results are easily affected by subjective factors such as the state of the inspector and the point setting habits, which can lead to large errors in the test results. Therefore, traditional manual point measurement technology can no longer meet the needs of efficient, real-time and accurate on-site testing.

[0015] This invention enables the measurement of glare from ETC gantry supplementary lights, and also enables dynamic measurement. When using this invention to measure the glare of ETC gantry supplementary lights, traffic can be stopped.

[0016] This invention is simple to operate. It uses an integrated device to measure the threshold increment, a quantitative evaluation index of glare. It also uses an integrated device to obtain the observation location information, the illuminance information at the simulated human eye, and the ground brightness information required for threshold increment calculation.

[0017] This invention requires significantly less time. Measuring the glare of a street lamp using conventional methods typically takes at least 30 minutes. However, measuring the glare of an ETC gantry supplementary lighting lamp using this invention generally takes only 3 minutes. Summary of the Invention

[0018] The ETC gantry lighting glare measuring device of the present invention mainly consists of a locator, a data processing module, a reflected signal demodulator, a reflected signal sensor, a transmitted signal modulator, a signal transmitter, a transmitted signal demodulator, a transmitted signal sensor, a transparent and reflective mirror group, a ground-off detector, a frame-off detector, an upper surface illuminance detector, a left camera, a middle camera, a right camera, a middle camera light tube, a switcher, a switcher controller, a support frame, and a reference level frame, etc. The hardware connection diagram is shown in Figure 1.

[0019] In Figure 1, 1 is the locator, 2 is the data processing module, 3-1 is the reflected signal demodulator, 3-2 is the reflected signal sensor, 4-1 is the transmitted signal modulator, 4-2 is the signal transmitter, 5-1 is the transmitted signal demodulator, 5-2 is the transmitted signal sensor, 6 is the transparent and reflective mirror assembly, 7 is the ground-off detector, 8 is the off-frame detector, 9 is the vertical illuminance detector, 10 is the left camera, 11 is the center camera, 12 is the right camera, 13 is the center camera's optical tube, 14 is the switcher, 15 is the switcher controller, 16 is the support frame, 17 is the reference horizontal frame, S1 is the target road, S2 is the ETC gantry, h is the vertical distance between the off-frame detector and the ETC gantry, and d is the vertical distance between the ground-off detector and the ground. All ground locations are assumed to be level.

[0020] The locator can be a GPS-based positioning device or a BDS-based positioning device to obtain the positioning information of this device.

[0021] The data processing module can be a computer, industrial control computer, microcontroller, etc., which collects data output from the locator, reflected signal demodulator, transmitted signal modulator, ground-off detector, off-frame detector, vertical surface illuminance detector, left camera, middle camera, right camera, etc. via wired or wireless means, and controls the transmitted signal demodulator, switcher controller, etc.

[0022] A reflected signal demodulator is a signal demodulation circuit that demodulates the signal output from a reflected signal sensor. The demodulation method corresponds to the modulation method.

[0023] A signal modulator is a signal modulation circuit that controls the signal transmitter to emit modulated optical signals. The modulation method can be trigonometric functions, etc.

[0024] The transmitting signal demodulator is a signal demodulation circuit that demodulates the signal output from the transmitting signal sensor. The demodulation method corresponds to the modulation method.

[0025] The signal transmitter is the component that emits light signals. A single-wavelength laser is preferred, and the wavelength can generally be selected from the infrared band, such as 905nm or 1550nm, which have relatively weak intensity in the solar spectrum.

[0026] A reflective mirror assembly consists of a set of lenses with a reflectivity of m1% and a transmittance of m2% and a corresponding support. Its basic principle can be to cement two lenses with different refractive indices together, so that one lens surface reflects light while the other transmits light. Alternatively, an optical film can be coated on one lens surface, causing one surface to reflect light while the other transmits light. m1 + m2 = 100.

[0027] The central axis of the beam emitted by the signal transmitter passes through the center point of the translucent and reflective mirror assembly. The beam energy emitted by the signal transmitter is p. A portion m2% passes through the translucent and reflective mirror assembly, is reflected by the ground, and then enters the reflection signal sensor. After demodulation by the reflection signal demodulator, the energy p2 of the reflected light is obtained. A portion m1% of the beam emitted by the signal transmitter is reflected by the translucent and reflective mirror assembly, enters the transmitting signal sensor, and is demodulated by the transmitting signal demodulator to obtain the sensed beam energy p1.

[0028] By using a single-wavelength laser to emit signals and combining signal modulation and demodulation, interference from external ambient light is avoided.

[0029] A ground-based detector is a component that measures the vertical distance from the ground. It can be a laser ranging module or an ultrasonic ranging module, etc.

[0030] The off-frame detector is a device for measuring glare from ETC gantry lighting. It measures the vertical distance from the ETC gantry when passing under it. It can be a laser ranging module or an ultrasonic ranging module, etc.

[0031] The measuring surface on the lower side of the ground detector, the measuring surface on the upper side of the off-frame detector, the measuring surface on the upper side of the vertical illuminance detector, the photosensitive surface on the lower side of the reflective signal sensor, the emitting surface on the lower side of the signal transmitter, and the photosensitive surface on the lower side of the transmitting signal sensor are all on the same plane.

[0032] The vertical surface illuminance detector is an illuminance acquisition component with a sampling frequency higher than 100Hz.

[0033] The left, center, and right cameras are positioned on the same horizontal plane and fixed to a reference horizontal frame, facing the same direction. The external dimensions of the left, center, and right cameras are identical. All three cameras have a sampling frequency of k and can trigger simultaneous recording. The center camera is 1.5m above the ground, a height typically set in conventional studies for the driver's eye level. The axes of the left, center, and right cameras are parallel and lie on the same plane, forming an angle of 1° with the road axis. The axes of the left, center, and right cameras are horizontally downward relative to the road axis. This is to simulate a scenario where the observer's eye level is 1.5m above the road surface, and the line of sight passes through the observer's eye and downwards by 1° on the longitudinal vertical plane of the road. In other words, at this point, the axes of the left, center, and right cameras respectively pass through the left, center, and right cameras and downwards by 1° on the longitudinal vertical plane of the road.

[0034] The switcher is a circular ring, which can be made of glass and is symmetrically divided into 8 equal parts. Adjacent parts have different transmittance, while parts separated by a certain distance have the same transmittance. The part with higher transmittance has a transmittance of hn, and the part with lower transmittance has a transmittance of ln. The transmittance is quantified by placing different parts of the ring between a light source and a standard luminance meter. If the luminance value output by the standard luminance meter remains unchanged before and after placement, the transmittance is recorded as 100%. If the luminance value output by the standard luminance meter is 0% after placement, the transmittance is recorded as 0%. In other words, the transmittance is the ratio of the luminance value output by the standard luminance meter after placement to the luminance value output by the standard luminance meter before placement.

[0035] Under the control of the switcher controller, the switcher rotates around its center point at a speed of v revolutions per second. k ≥ 16V.

[0036] The reference level and support frame are connected, and the support frame is connected to the switch controller. The reference level is parallel to the road.

[0037] The central axis of the switcher coincides with the central axis of the central camera. The inner diameter of the switcher is equal to the lens diameter of the central camera.

[0038] The fields of view of the left and right cameras are directly blocked by the ring of the switcher.

[0039] The ETC gantry lighting glare measuring device establishes internal spatial coordinates. The midpoint of the central camera lens is designated as point O, with coordinates (0, 0). The x-axis is defined by the line connecting the midpoints of the central, left, and right camera lenses, with the positive direction pointing from the left camera to the right camera. The y-axis is defined by the central axis of the central camera, with the reference horizontal frame parallel to the x-axis, and the positive direction pointing from the central camera to the switcher.

[0040] The internal spatial coordinates of the locator are (xd, yd). After each component is installed, its coordinates are measured, and the distances between the different components are calculated.

[0041] The technical flowchart of the method for measuring glare from ETC gantry lighting is shown in Figure 4.

[0042] The ETC gantry lighting glare measuring device mainly consists of a locator, a data processing module, a reflected signal demodulator, a reflected signal sensor, a transmitted signal modulator, a signal transmitter, a transmitted signal demodulator, a transmitted signal sensor, a transparent and reflective mirror assembly, a ground-off detector, a frame-off detector, an upper surface illuminance detector, a left camera, a middle camera, a right camera, a middle camera light tube, a switcher, a switcher controller, a support frame, and a reference level frame.

[0043] The overall technical solution implementation process is as follows:

[0044] (1) It needs to be clarified that the supplementary lighting can refer to either the automatic video recognition supplementary lighting device for highway vehicle license plates or the supplementary lighting device for traffic technology monitoring imaging. The threshold increment of the two should be measured and calculated separately. That is, the corresponding supplementary lighting device needs to be selected for measurement, which can be referred to as the selected supplementary lighting. When the automatic video recognition supplementary lighting device for highway vehicle license plates is selected as the measurement object, the supplementary lighting mentioned below refers to the automatic video recognition supplementary lighting device for highway vehicle license plates; when the supplementary lighting device for traffic technology monitoring imaging is selected as the measurement object, the supplementary lighting mentioned below refers to the traffic technology monitoring imaging supplementary lighting device.

[0045] (2) The measuring device for ETC gantry lighting glare needs to be calibrated before use.

[0046] (3) First, calibrate the illuminance. Position the ETC gantry lighting glare measuring device at a distance of 13.75m from the ETC gantry. Here, 13.75m is the distance from the ETC gantry when the driver's eye is at a height of 1.5m, allowing them to observe the supplementary lighting. The calculation process is as follows: Assuming the observer's eye height is 1.5m above the road surface, and the line of sight passes horizontally downwards by 1° on the longitudinal vertical plane of the road, and the vertical distance between the automatic license plate recognition supplementary lighting device and the road surface is 6.5m, then the distance from the observer to the ETC gantry must be greater than 2.75(6.5-1.5)m, which is 13.75m. The vertical distance between the traffic technology monitoring imaging supplementary lighting device and the road surface is 6m, therefore the distance from the observer to the ETC gantry must be greater than 2.75(6-1.5)m, which is 12.375m. To accurately calibrate the illuminance, especially the illuminance generated by the automatic video recognition supplementary lighting device for highway vehicle license plates, the measuring device for ETC gantry lighting glare is stationary at a distance of more than 13.75m in front of the ETC gantry.

[0047] (4) Adjust the switcher so that the part of the switcher with low light transmittance exactly blocks the left and right cameras. Install a light shield in front of the probe of the standard-grade illuminance meter. The diameter of the light shield is the same as the diameter of the probe, and the length is three times the diameter of the probe. Place the probe of the standard-grade illuminance meter and the light shield in front of the left camera, and point the light shield at the selected fill light. Measure the reference illuminance value ZSL1. Place the probe of the standard-grade illuminance meter and the light shield in front of the right camera, and point the light shield at the selected fill light. Measure the reference illuminance value ZSR1. Use the left and right cameras to capture images at this time, and obtain the electrical signal values ​​of all pixels of the selected fill light part in the image as DL1 and DR1, respectively. Adjust the switcher so that the part of the switcher with high light transmittance exactly blocks the left and right cameras. Place the probe of the standard-grade illuminance meter and the light shield in front of the left camera, and point the light shield at the selected fill light. Measure the reference illuminance value ZSL2. Place the probe and light shield of the standard-grade illuminance meter in front of the right camera, and point the light shield at the selected fill light to measure the reference illuminance value ZSR2. Use the left and right cameras to capture images at this time, and obtain the electrical signal values ​​of all pixels of the selected fill light portion in the image as DL2 and DR2, respectively. Calibrate the left and right cameras, and record the relationship between the selected fill light illuminance value ZCL and the electrical signal DLn acquired by the left camera as follows: when the area in front of the left camera is a part of the switch with low light transmittance, ZCL = DLn * ZSL1 / (DL1 / ln); when the area in front of the left camera is a part of the switch with high light transmittance, ZCL = DLn * ZSL2 / (DL2 / hn). The relationship between the selected supplementary light illuminance value ZCR obtained by the right camera and the electrical signal DRn is denoted as follows: when the area in front of the right camera is a part of the switch with low light transmittance, ZCR = DRn * ZSR1 / (DR1 / ln); when the area in front of the right camera is a part of the switch with high light transmittance, ZCR = DRn * ZSR2 / (DR2 / hn).

[0048] (5) Then, calibrate the position. Use a total station to measure the distance JLS1 between the selected supplementary light on the ETC gantry and the central camera. Using the image data acquired by the left and right cameras, calculate the distance JLW1 between the selected supplementary light on the ETC gantry and the central camera using a depth calculation method based on the parallax principle. Perform distance calibration, and record the relationship between the calibrated distance measurement result JLYn and the uncalibrated calculation result JLWn as JLYn=JLWn*(JLS1 / JLW1). Use a total station to measure the height LEDh of the selected supplementary light on the ETC gantry above the ground, and the lateral deviation LEDw of the selected supplementary light on the ETC gantry from the road centerline. Use the central camera to acquire image data, and extract the number of pixels XSh of the selected supplementary light above the ground and the number of pixels XSw of the selected supplementary light from the road centerline in the image. Perform coordinate calibration, and record the relationship between the selected supplementary light height measurement result Lhn and the number of pixels Xhn as Lhn=Xhn*(LEDh / XSh), and record the relationship between the selected supplementary light lateral deviation measurement result Lwn from the road centerline and the number of pixels Xwn as Lwn=Xwn*(LEDw / XSw).

[0049] (6) Recalibrate the brightness. First, measure the reference brightness value LS of the ground below the ETC gantry using a standard-grade luminance meter. Then, move the ETC gantry lighting glare measuring device directly below the ETC gantry. The signal transmitter emits a modulated beam with energy p0. The light with m2% energy passes through the translucent and reflective mirror group, is reflected by the ground below the ETC gantry, is measured by the reflection signal sensor, and demodulated by the reflection signal demodulator to obtain the reflected beam energy p20. The light with m1% energy is reflected by the translucent and reflective mirror group, then enters the transmitting signal sensor, is demodulated by the transmitting signal modulator to obtain the corresponding beam energy p10. Therefore, p0 = p10 / (m1%). The vertical illuminance detector measures the illuminance value E10, the ground distance detector measures the distance d0 from the ground, and the gantry distance detector measures the distance h0 from the ETC gantry. Thus, the brightness value LW of the ground below the ETC gantry is obtained as p20(E10h0). 2 ) / (p10(h0+d0) 2 The ground brightness measurement result obtained by the calibrated ETC gantry lighting glare measuring device is LJ = p20(E10h0). 2 ) / (p10(h0+d0) 2 )*LS / LW. That is, in subsequent measurements, the ground brightness measurement result is the actual measured value LC multiplied by the reference brightness value LS recorded during calibration, and then divided by the measured value LW recorded during calibration.

[0050] (7) During on-site measurement, the ETC gantry lighting glare measuring device is moved from an area more than 50m away from the ETC gantry towards the ETC gantry. The central camera is located on a plane perpendicular to the road surface and including the road centerline. The switcher controller controls the switcher to rotate at a speed of v revolutions per second. The left, central, and right cameras face the ETC gantry and simultaneously trigger the acquisition of images at a sampling frequency k, where k≥16v. Since the switcher is axially symmetrically divided into 8 equal parts, the transmittance of adjacent parts is different, while the transmittance of separated parts is the same. The transmittance of the part with high transmittance is hn, and the transmittance of the part with low transmittance is ln. When the switcher rotates, the left and right cameras can acquire images that are simultaneously blocked by the part with high transmittance, and can also acquire images that are simultaneously blocked by the part with low transmittance. Using the image data acquired by the left and right cameras, the distance JLYn between the selected supplementary light on the ETC gantry and the central camera is obtained using a depth calculation method based on the parallax principle and calibration. Using the image data acquired by the central camera and combined with calibration, the height measurement result Lhn of the selected supplementary light and the lateral deviation measurement result Lwn of the selected supplementary light from the road centerline are obtained. Then, the angle formed by the line connecting the center point of the central camera and the selected supplementary light with the axis of the central camera is calculated. The combined illuminance value ZCZ = (ZCR + ZCL) / 2 was measured using the left and right cameras.

[0051] (8) When the ETC gantry lighting glare measuring device passes under the ETC gantry, the signal transmitter emits a modulated light beam with energy p. m2% of the light passes through the translucent and reflective mirror group, is reflected by the ground below the ETC gantry, and is measured by the reflection signal sensor. After being demodulated by the reflection signal demodulator, the reflected light beam energy p2 is obtained. m2% of the light is reflected by the translucent and reflective mirror group, then enters the transmitting signal sensor, and is demodulated by the transmitting signal modulator to obtain the corresponding light beam energy p1. Therefore, p = 2 * p1. The vertical illuminance detector measures the illuminance value E1, the ground-based detector measures the distance d from the ground, and the gantry-based detector measures the distance h from the ETC gantry. Therefore, the ground brightness measurement result is p2(E1h). 2 ) / (p1(h+d) 2 )*LS / LW.

[0052] (9) Calculate the threshold increment of the selected supplementary light: Attached Figure Description

[0053] Figure 1 Hardware connection diagram

[0054] In Figure 1, 1 is the locator, 2 is the data processing module, 3-1 is the reflected signal demodulator, 3-2 is the reflected signal sensor, 4-1 is the transmitted signal modulator, 4-2 is the signal transmitter, 5-1 is the transmitted signal demodulator, 5-2 is the transmitted signal sensor, 6 is the transparent and reflective mirror assembly, 7 is the ground-off detector, 8 is the off-frame detector, 9 is the vertical illuminance detector, 10 is the left camera, 11 is the center camera, 12 is the right camera, 13 is the center camera's optical tube, 14 is the switcher, 15 is the switcher controller, 16 is the support frame, 17 is the reference horizontal frame, S1 is the target road, S2 is the ETC gantry, h is the vertical distance between the off-frame detector and the ETC gantry, and d is the vertical distance between the ground-off detector and the ground. In this invention, the ground is assumed to be level.

[0055] In Figure 2, 11 is the center camera, 17 is the reference horizontal frame, S1 is the ground, S3 is the axis of the center camera, and β is the angle formed between the axis of the center camera and the ground, with a value of 1°.

[0056] Figure 3 is a schematic diagram of the location of the supplementary lighting device in the prior art.

[0057] In Figure 3, S1 represents the target road, S2 is the ETC gantry, S4 is the road adjacent to the target road, S9 is the boundary line between the two roads, S5 is the automatic video recognition supplementary lighting device for highway vehicle license plates, S6 is the traffic technology monitoring imaging supplementary lighting device, S8 is the reference axis of the traffic technology monitoring imaging supplementary lighting device, and S7 is the centerline of the target road. α is the spatial angle between the reference axis of the traffic technology monitoring imaging supplementary lighting device and the boundary line between the two roads, with a value of 20°.

[0058] Figure 4 Flowchart of Technical Solution

[0059] Figure 5. Flowchart of the technical solution for specific example 1 Detailed Implementation

[0060] This invention can be used to measure the threshold increment of the automatic video recognition supplementary lighting device for highway vehicle license plates and the supplementary lighting device for traffic technology monitoring imaging installed on the ETC gantry, and its process is shown in Figure 5.

[0061] Referring to the flowchart of Example 1, the implementation process of the technical solution in Example 1 is as follows:

[0062] (1) The glare measuring device for ETC gantry lighting is installed on the inspection vehicle. The left camera, center camera, right camera, center camera optical tube, switcher, switcher controller, support frame, and reference level frame are installed in the passenger seat. The locator and data processing module are installed inside the inspection vehicle. The reflected signal demodulator, reflected signal sensor, transmitted signal modulator, signal transmitter, transmitted signal demodulator, transmitted signal sensor, transparent and reflective mirror assembly, ground clearance detector, off-frame detector, and vertical illuminance detector are installed on the side of the inspection vehicle.

[0063] (2) Park the testing vehicle at least 13.75 meters away from an ETC gantry and use a standard illuminance meter and total station to calibrate the illuminance and position. If only the threshold increment of the traffic technology monitoring imaging supplementary lighting device on the ETC gantry is considered, the testing vehicle can also be parked at least 12.375 meters away from an ETC gantry for illuminance and position calibration.

[0064] (3) Park the testing vehicle directly under the same ETC gantry and use a standard-grade luminance meter to calibrate the luminance.

[0065] (4) Drive the testing vehicle toward the target ETC gantry and stop only after passing the target ETC gantry. Use the ETC gantry lighting glare measurement device to collect and calculate the corresponding ETC gantry supplementary light threshold increment formula.

[0066] This invention enables the measurement of glare from ETC gantry supplementary lights, and also enables dynamic measurement. When using this invention to measure the glare of ETC gantry supplementary lights, traffic can be stopped.

[0067] This invention is simple to operate. It uses an integrated device to measure the threshold increment, a quantitative evaluation index of glare. It also uses an integrated device to obtain the observation location information, the illuminance information at the simulated human eye, and the ground brightness information required for threshold increment calculation.

[0068] This invention requires significantly less time. Measuring the glare of a street lamp using conventional methods typically takes at least 30 minutes. However, measuring the glare of an ETC gantry supplementary lighting lamp using this invention generally takes only 3 minutes.

[0069] This invention utilizes a locator, a data processing module, a reflected signal demodulator, a reflected signal sensor, a transmitted signal modulator, a signal transmitter, a transmitted signal demodulator, a transmitted signal sensor, a transparent and reflective mirror assembly, a ground-off detector, a frame-off detector, an upper surface illuminance detector, a left camera, a middle camera, a right camera, a middle camera light tube, a switcher, a switcher controller, a support frame, and a reference level frame to form a device for measuring glare from ETC gantry lighting.

[0070] The proposed method for measuring glare from ETC gantry lighting in this invention derives the formula p2(E1h) for calculating ground brightness by measuring the ground reflectivity and ground brightness beneath the ETC gantry. 2 ) / (p1(h+d) 2 The LS / LW method enables the acquisition of ground brightness at close range, solving the problems of excessive external stray light interference and decreased accuracy of brightness measurements at long distances caused by using luminance meters. By obtaining supplementary light brightness at different orders of magnitude through switch blades with varying transmittance, the method combines the sensitivity advantages of the left and right cameras in high and low brightness areas, reducing system errors and obtaining a more accurate comprehensive illuminance value ZCZ = (ZCR + ZCL) / 2. Using the left and right cameras, the distance between the ETC gantry supplementary light and the central camera was measured using a binocular vision method. The height of the ETC gantry supplementary light and its lateral deviation from the road centerline were calculated using the central camera. The angle formed by the line connecting the center point of the central camera and the supplementary light to the central camera's axis was calculated using three geometric parameters. Quantitative measurement of glare from ETC gantry lighting was achieved, and the threshold increment formula for ETC gantry supplementary lighting was calculated:

[0071] 3. This invention uses the on-site ETC gantry for pre-use calibration. Calibration is not required in a standard darkroom or geometric metrology laboratory, improving work efficiency. Since highways lack streetlights and have low nighttime brightness, other light sources are less bright and have weaker interference capabilities compared to the ETC gantry supplementary lighting; therefore, the site can be considered equivalent to an open darkroom. When the ETC gantry lighting glare measuring device is stationary at a distance of more than 13.75m in front of the ETC gantry, a standard-grade illuminance meter is used to obtain standard illuminance values ​​to calibrate the illuminance measurement capability of the ETC gantry lighting glare measuring device; a total station is used to obtain the standard position value of the ETC gantry supplementary lighting to calibrate the position measurement capability of the ETC gantry lighting glare measuring device. When calibrating the brightness measurement capability of the ETC gantry lighting glare measuring device, first place the ETC gantry lighting glare measuring device at a distance of more than 13.75m in front of the ETC gantry, and measure the standard value of the ground brightness using a standard-grade luminance meter. Then, place the ETC gantry lighting glare measuring device under the ETC gantry and collect brightness information using the ETC gantry lighting glare measuring device. Finally, calibrate the brightness measurement capability of the ETC gantry lighting glare measuring device.

Claims

1. A measuring device for glare from ETC gantry lighting, characterized in that: Includes a locator, data processing module, reflected signal demodulator, reflected signal sensor, transmitted signal modulator, signal transmitter, transmitted signal demodulator, transmitted signal sensor, transparent and reflective mirror assembly, ground-off detector, off-frame detector, vertical illuminance detector, left camera, center camera, right camera, center camera light tube, switcher, switcher controller, support frame, and reference level frame; A locator is a positioning device based on a GPS receiver module or a positioning device based on a BDS receiver module. The data processing module is a computer, industrial control computer, or microcontroller that collects data from the locator, reflected signal demodulator, transmitted signal modulator, ground-off detector, off-frame detector, vertical surface illuminance detector, left camera, middle camera, and right camera via wired or wireless means, and controls the transmitted signal demodulator and switcher controller. A reflected signal demodulator is a signal demodulation circuit that demodulates the signal output from a reflected signal sensor. The demodulation method corresponds to the modulation method. A transmitting signal modulator is a signal modulation circuit that controls the signal transmitter to emit modulated optical signals. The transmitting signal demodulator is a signal demodulation circuit that demodulates the signal output from the transmitting signal sensor. The demodulation method corresponds to the modulation method. A signal transmitter is a component that emits light signals; The reflective mirror assembly consists of a set of lenses with a reflectivity of m1% and a transmittance of m2% and a corresponding support, where m1+m2=100; The central axis of the beam emitted by the signal transmitter passes through the center point of the translucent and reflective mirror group; the energy of the beam emitted by the signal transmitter is p, and m2% of it passes through the translucent and reflective mirror group, is reflected by the ground, and then enters the reflection signal sensor. After being demodulated by the reflection signal demodulator, the energy of the reflected light p2 is obtained; m1% of the beam emitted by the signal transmitter is reflected by the translucent and reflective mirror group, enters the transmission signal sensor, and after being demodulated by the transmission signal demodulator, the sensed beam energy p1 is obtained. A ground clearance detector is a component that measures the vertical distance from the ground. The off-frame detector is a device for measuring the glare of ETC gantry lighting. It is a component that measures the vertical distance from the ETC gantry when passing under it. It can be a laser ranging module or an ultrasonic ranging module. The measuring surface on the lower side of the ground detector, the measuring surface on the upper side of the off-frame detector, the measuring surface on the upper side of the vertical illuminance detector, the photosensitive surface on the lower side of the reflective signal sensor, the emitting surface on the lower side of the signal transmitter, and the photosensitive surface on the lower side of the transmitting signal sensor are all on the same plane. The vertical surface illuminance detector is an illuminance acquisition component with a sampling frequency higher than 100Hz; The left, middle, and right cameras are on the same horizontal plane and fixed on a reference horizontal frame, facing the same direction; the external dimensions of the left, middle, and right cameras are the same; the sampling frequency of the left, middle, and right cameras is all k, and they can be triggered to shoot simultaneously; the middle camera is 1.5m above the ground; the axes of the left, middle, and right cameras are parallel to each other and on the same plane, forming an angle of 1° with the road axis, and the axes of the left, middle, and right cameras are horizontally downward relative to the road axis; The switch is a ring that is symmetrically divided into 8 equal parts. The transmittance of adjacent parts is different, while the transmittance of the parts that are separated by a certain distance is the same. The part with high transmittance has a transmittance of hn, and the part with low transmittance has a transmittance of ln. Under the control of the switcher controller, the switcher rotates around the switcher center point at a speed of v revolutions per second; k≥16v; The reference level and the support frame are connected, and the support frame is connected to the switch controller; the reference level is parallel to the road; The central axis of the switcher coincides with the central axis of the central camera; the inner diameter of the switcher is equal to the lens diameter of the central camera. The fields of view of the left and right cameras are directly blocked by the ring of the switcher.

2. The method of using the apparatus of claim 1, characterized in that: The ETC gantry lighting glare measuring device establishes internal spatial coordinates; with the midpoint of the lens of the central camera as point O, and the coordinates as (0, 0); with the line connecting the midpoints of the central camera lens, the left camera lens, and the right camera lens as the x-axis, and the direction from the left camera to the right camera as the positive direction; with the central axis of the central camera as the y-axis, the reference horizontal frame is parallel to the x-axis, and the direction from the central camera to the switcher is the positive direction; The internal spatial coordinates of the locator are (xd, yd); after each component is installed, its coordinates are measured, and the distance between the different components is calculated. The implementation process is as follows: (1) The supplementary light refers to the supplementary light device for automatic identification of vehicle license plate video on highways, or the supplementary light device for traffic technology monitoring imaging. The threshold increment of the two should be measured and calculated separately. That is, the corresponding supplementary light device needs to be selected for measurement, which can be called the selected supplementary light. When the supplementary light device for automatic identification of vehicle license plate video on highways is selected as the measurement object, the supplementary light mentioned below refers to the supplementary light device for automatic identification of vehicle license plate video on highways. When the supplementary light device for traffic technology monitoring imaging is selected as the measurement object, the supplementary light mentioned below refers to the supplementary light device for traffic technology monitoring imaging. (2) The measuring device for ETC gantry lighting glare needs to be calibrated before use; (3) First, calibrate the illuminance; place the ETC gantry lighting glare measuring device at a distance of more than 13.75m in front of the ETC gantry; (4) Adjust the switcher so that the part of the switcher with low light transmittance exactly blocks the front of the left and right cameras; install a light shield in front of the probe of the standard illuminance meter, the diameter of the light shield is the same as the diameter of the probe, and the length is 3 times the diameter of the probe; place the probe of the standard illuminance meter and the light shield in front of the left camera, and point the light shield at the selected fill light, and measure the reference illuminance value ZSL1; place the probe of the standard illuminance meter and the light shield in front of the right camera, and point the light shield at the selected fill light, and measure the reference illuminance value ZSR1; use the left and right cameras to capture the images at this time, and obtain the electrical signal values ​​of all pixels of the selected fill light part in the image as DL1 and DR1 respectively; adjust the switcher so that the part of the switcher with high light transmittance exactly blocks the front of the left and right cameras; place the probe of the standard illuminance meter and the light shield in front of the left camera, and point the light shield at the selected fill light, and measure the reference illuminance value ZSL2; place the probe of the standard illuminance meter and the light shield in front of the left camera, and point the light shield at the selected fill light, and measure the reference illuminance value ZSL2; place the probe of the standard illuminance meter and the light shield in front of the right ... In front of the right camera, with the light shield pointed at the selected fill light, the reference illuminance value ZSR2 is measured. Images are captured using both the left and right cameras, and the electrical signal values ​​of all pixels in the selected fill light area are obtained as DL2 and DR2, respectively. The left and right cameras are calibrated, and the relationship between the selected fill light illuminance value ZCL and the electrical signal DLn acquired by the left camera is recorded as follows: when the area in front of the left camera is a low-transmittance part of the switch, ZCL = DLn * ZSL1 / (DL1 / ln); when the area in front of the left camera is a high-transmittance part of the switch, ZCL = DLn * ZSL2 / (DL2 / hn). Similarly, the relationship between the selected fill light illuminance value ZCR acquired by the right camera and the electrical signal DRn is recorded as follows: when the area in front of the right camera is a low-transmittance part of the switch, ZCR = DRn * ZSR1 / (DR1 / ln); when the area in front of the right camera is a high-transmittance part of the switch, ZCR = DRn * ZSR2 / (DR2 / hn). (5) Then, the position is calibrated; the distance JLS1 between the selected supplementary light and the camera on the ETC gantry is measured using a total station; the distance JLW1 between the selected supplementary light and the camera on the uncalibrated ETC gantry is obtained by using the image data collected by the left and right cameras. Distance calibration is performed, and the relationship between the calibrated distance measurement result JLYn and the uncalibrated calculation result JLWn is recorded as JLYn=JLWn*(JLS1 / JLW1); the height LEDh of the selected supplementary light on the ETC gantry ahead from the ground and the lateral deviation LEDw of the selected supplementary light on the ETC gantry ahead from the road centerline are measured using a total station; the image data is collected by the camera, and the number of pixels XSh of the selected supplementary light from the ground and the number of pixels XSw of the selected supplementary light from the road centerline are extracted from the image; coordinate calibration is performed, and the relationship between the calibrated height measurement result Lhn of the selected supplementary light and the number of pixels Xhn is recorded as Lhn=Xhn*(LEDh / XSh), and the relationship between the calibrated lateral deviation measurement result Lwn of the selected supplementary light from the road centerline and the number of pixels Xwn is recorded as Lwn=Xwn*(LEDw / XSw); (6) Recalibrate the brightness; first, use a standard-grade luminance meter to measure the reference brightness value LS of the ground below the ETC gantry; Next, the measuring device for the glare of the ETC gantry lighting is moved directly below the ETC gantry. The signal transmitter emits a modulated light beam with energy p0 and m2% passing through the transparent and reflective mirror group. After being reflected by the ground below the ETC gantry, the light is measured by the reflection signal sensor and demodulated by the reflection signal demodulator to obtain the reflected light beam energy p20. The light m1% is reflected by the transmissive and reflective mirror group, then enters the emission signal sensor, is demodulated by the emission signal modulator, and the corresponding beam energy p10 is obtained; then p0 = p10 / (m1%). The illuminance value E10 is measured by the vertical illuminance detector, the distance d0 from the ground is measured by the ground-based detector, and the distance h0 from the ETC gantry is measured by the off-frame detector. Therefore, the luminance value LW of the ground below the ETC gantry is p20(E10h0). 2 ) / (p10(h0+d0) 2 The ground brightness measurement result of the calibrated ETC gantry lighting glare measuring device is obtained: LJ = p20(E10h0). 2 ) / (p10(h0+d0) 2 )*LS / LW; that is, in subsequent measurements, the ground brightness measurement result is the actual measured value LC multiplied by the reference brightness value LS recorded during calibration and then divided by the measured value LW recorded during calibration. (7) When conducting on-site measurements, the measuring device for the glare of the ETC gantry lighting shall be moved from an area more than 50m away from the ETC gantry toward the ETC gantry; The central camera is located on a plane perpendicular to the road surface and including the road centerline. The switcher controller controls the switcher to rotate at a speed of v revolutions per second. The left, central, and right cameras face the ETC gantry and simultaneously trigger image capture at a sampling frequency k, where k ≥ 16v. Because the switcher is axially symmetrically divided into 8 equal parts, adjacent parts have different transmittance, while intervening parts have the same transmittance. The part with high transmittance has a transmittance of hn, and the part with low transmittance has a transmittance of ln. When the switcher rotates, the left and right cameras can capture images... Simultaneously, images obscured by parts with high light transmittance can also be captured by parts obscured by parts with low light transmittance. Using image data from the left and right cameras, the distance JLYn between the selected supplementary light on the ETC gantry and the central camera is obtained. Using image data from the central camera, combined with calibration, the height measurement result Lhn of the selected supplementary light and the lateral deviation measurement result Lwn of the selected supplementary light from the road centerline are obtained. Finally, the angle formed by the line connecting the center point of the central camera and the selected supplementary light with the axis of the central camera is calculated. The combined illuminance value ZCZ = (ZCR + ZCL) / 2 was measured using the left and right cameras. (8) When the measuring device for the glare of the ETC gantry lighting passes under the ETC gantry, the signal transmitter emits a modulated light beam with a beam energy of p,m2% passing through the transparent and reflective mirror group, being reflected by the ground under the ETC gantry, being measured by the reflection signal sensor, and being demodulated by the reflection signal demodulator to obtain the reflected beam energy p2. 2% of the light is reflected by the transmissive and reflective mirror group, then enters the emission signal sensor, is demodulated by the emission signal conditioner, and the corresponding beam energy p1 is obtained; therefore, p = 2 * p1; the illuminance detector on the vertical surface measures the illuminance value E1, the ground-based detector measures the distance d from the ground, and the distance h from the ETC gantry is measured by the off-grid detector. Therefore, the ground brightness measurement result is p2(E1h) 2 ) / (p1(h+d) 2 )*LS / LW; (9) Calculate the threshold increment of the selected supplementary light:

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