Research on Evaluation Method of Light Distribution Performance of Automobile Headlamp Based on Subjective Evaluation Experiment
Research on Evaluation Method of Light Distribution Performance of Automobile Headlamps Based on Subjective Evaluation Experiment
Wang Wei1, Lin Yandan2, Bu Weili1
(1. Shanghai Motor Vehicle Testing Center, Shanghai 201805; 2. Fudan University, Shanghai 200433)
Abstract: The CIE188 Technical Report introduced an objective calculation method for evaluating the light distribution performance of automotive headlamps, which allows for a quantitative assessment of this performance. A dedicated software was developed to assist in implementing this evaluation. To verify the applicability of this method in China, a subjective evaluation experiment was conducted on four sets of headlamps, aiming to explore the correlation between the results from the subjective evaluation and those calculated according to the CIE188 report. The experimental findings revealed that while the method can compare the light distribution performance of different headlamps, the correlation between the two methods was not significant.
Keywords: CIE 188 technical report; light distribution performance; quantitative evaluation; subjective evaluation
CLC number: TM923 Document code: A DOI: 10.3969∕j.issn.1004-440X.2015.02.023
Experimental Verification of Performance Method for Vehicle Headlighting Systems
Wang Wei1, Lin Yandan2, Bu Weili1
(1. Shanghai Motor Vehicle Inspection Center, Shanghai 201805, China; 2. Fudan University, Shanghai 201805, China)
The evaluation of the photometric performance of vehicle headlamps requires a standardized, accurate, and reliable method. The CIE 188 Technical Report outlines specific procedures for assessing the photometric performance of vehicle headlighting systems. This evaluation can be performed using self-developed software. Three subjective rating tasks were carried out to validate the rationality of the methods described in the report and their suitability for Chinese subjects. The comparison between the calculated results based on the CIE 188 report and the subjective ratings indicated no significant correlation between the two methods. Further research is necessary to refine these methods.
Keywords: CIE 188 Technical Report; photometric performance; evaluate; subjective rating
Introduction
There are strict requirements on the light distribution of automobile headlights across countries. China adopted the ECE system standard, and since 1993, it has established several national mandatory standards for automotive lighting [1]. Currently, there are three national standards related to the light distribution of automobile headlamps, including GB 4599-2007 “Filament Bulb Headlamps for Automobiles,†GB 21259-2007 “Gas Discharge Headlights for Automobiles,†and GB 25991-2010 “LED Headlamps for Automobiles†[2-4]. These standards define the illumination range within the safe braking distance, but they only allow for qualitative judgments of whether the headlamps meet requirements, not a quantitative evaluation of their advantages or disadvantages.
In 2010, the Fourth Division of the International Commission on Illumination (CIE) released the Technical Report No. 188, titled “Performance Assessment Method for Vehicle Headlighting Systems.†This report introduces a set of calculation methods for evaluating the light distribution performance of motor vehicle headlamp systems [5]. This method quantitatively evaluates the light distribution performance of headlamps from aspects such as road surface illumination and glare control, enabling comparisons between different headlamp systems. However, there is currently no open-source software available for performing calculations according to the CIE188 report. Manual calculations are inefficient and prone to errors, making the development of supporting software essential for research. Therefore, this study developed a dedicated software tool to implement the various calculation functions outlined in the CIE188 report. Additionally, due to the lack of research on the applicability of this method in China, this paper conducted a series of subjective evaluation experiments to examine the correlation between the results obtained using the CIE188 method and the subjective evaluations of participants.
1 Research Methods
1.1 Experimental Setup
This study consists of two parts. The first part involves verifying the accuracy of the software by comparing the ground illuminance values generated by the software with those simulated by LMT's fully automatic luminaire grading analysis system. In the second part, a subjective evaluation experiment was conducted on four sets of headlamp systems (designated as A, B, C, D). The results of the subjective evaluation were compared with the objective calculation results from the CIE188 report to assess the applicability of the method for evaluating the light distribution performance of headlamps.
1.2 Function of the Headlight Light Distribution Performance Calculation Software
The laboratory is equipped with LMT's automatic light distribution detection equipment, which is widely used by testing institutions around the world for scanning lamp light distributions. This device can measure the illuminance on the vertical plane 25 meters ahead of the headlamp with high precision (U rel = 5%, k = 2). The scanning method specified in the CIE188 report is used for capturing headlamp light distribution data.
1.3 Subjective Evaluation Experiment Task
The experiment took place at night, from 19:00 to about 1 am the next day. All controllable lighting fixtures around the site were turned off to ensure ambient illumination was less than 0.1 lx. The experimental site was a 6-lane road simulating real conditions, with each lane being 3 meters wide and approximately 200 meters long. Due to space constraints, only low beam tests were conducted. The low beam lights were installed on a fixed platform according to actual loading parameters to simulate the actual lighting effect of the headlamps.
1.3.1 Experimental Task 1: Low Beam Illumination Distance Assessment
A dark gray cube with a surface reflectance of 5% and a side length of 400 mm served as the visual target. The task involved identifying the target at increasing distances until it could no longer be detected. The distance at which the target was last identified was considered the low beam illumination distance.
1.3.2 Experimental Task 2: Evaluation of the Width of the Low Beam Illumination
The width of the low beam illumination was evaluated by identifying visual targets placed at various distances (10m, 20m, 30m, 40m, 50m) on both sides of the lane. The distance of the detectable target from the lane's longitudinal axis was taken as the beam illumination width at that distance.
1.3.3 Experimental Task 3: Evaluation of the Glare of the Low Beam
Subjects stood 50 meters away from the lights and observed visual targets placed 10 meters in front of them through a screen, using the De Bore evaluation scale to rate the glare. The observation hole was set at three different heights to account for variations in driver eye positions.
1.3.4 Experimental Process
Before the experiment, the following steps were undertaken: scanning the light distribution data of the four headlamps, measuring and recording the actual loading parameters, calibrating the headlamps, marking the test points, installing the headlamps on the test bench, and ensuring the ambient illumination was below 0.1 lx. After preparation, the three evaluation tasks—irradiation distance, irradiation width, and glare—were completed by eight participants, who evaluated all four headlamps.
2 Experimental Results
2.1 Software Verification
One of the main objectives of this paper was to verify the correlation between the scores of indicators such as the distance and width of the headlights actually evaluated and the results calculated according to the CIE188 report. The accuracy of the software was verified by comparing its results with those from LMT's LIMES 2000 software. The results showed a good match, with differences in ground illuminance values mostly below 1 lx and an average difference percentage of about 6%.
2.2 Headlights Light Distribution Performance Calculation Results
Using the headlamp light distribution performance calculation software, the evaluation scores of the four sets of low beam lamps were calculated. The results showed significant differences among the four systems, with the scores ranked as C > D > A > B. The two sets of HID low beam lights performed better than the halogen sources, except for glare.
2.3 Subjective Evaluation of Experimental Results
The subjective evaluation results showed significant differences among the four systems, with the same ranking as the objective calculations. However, no significant difference was found in the glare scores, though there was a significant difference in glare evaluation scores between the three observed heights.
2.4 Correlation Analysis
A correlation analysis was conducted between the objective calculation results and the subjective evaluation results. While the two methods showed good agreement in terms of irradiation distance and width, the correlation was not statistically significant for most indicators, suggesting further research is needed.
3 Discussion
3.1 Software Verification
The software's accuracy was verified by comparing its results with those of the LMT software. While the light output was similar, some differences were observed in the ground illuminance values, possibly due to variations in algorithms and interpolation methods.
3.2 Correlation Between Objective Calculation Results and Subjective Evaluation Results
The purpose of this study was to validate the applicability of the CIE188 method in China through subjective evaluation. Although the method provides a way to calculate various indicators, it does not specify how to combine them into a comprehensive score. The results showed consistency in rankings but no significant correlation between the two methods, likely due to the small sample size.
4 Conclusion
The headlamp light distribution performance software developed in this study can effectively implement the method described in the CIE188 report, ensuring accurate results. The method allows for comparing the light distribution performance of different headlamps, and the results are consistent with subjective evaluations. However, the correlation between the two methods is not significant, indicating the need for further verification with a larger sample size.
References
[1] Huang Zuoxian. Modern Auto Lamps [M]. Beijing: Changhong Publishing Company, 2003: 290.
[2] General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, China National Standardization Administration Committee. GB 4599-2007 Filament Bulb Headlamps for Automobiles [S]. Beijing: China Standard Press, 2008.
[3] General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, China National Standardization Administration Committee. GB 21259-2007 Gas Discharge Headlights for Automobiles [S]. Beijing: China Standard Press, 2008.
[4] General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, China National Standardization Administration Committee. GB 25991-2010 LED Headlamps for Automobiles [S]. Beijing: China Standard Press, 2011.
[5] CIE Central Bureau. Performance Assessment Method for Vehicle Headlighting Systems [R]. Vienna: CIE, 2010.
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