## 2 Lighting Specification for Automotive Headlamps  
Concerning traffic safety, the regulation ECE R112 Revision 3 [29] requires that automotive headlamps produce enough illuminance on the road while not illuminating the driver of the oncoming vehicle so as to cause glare [30; 31]. Therefore, the headlamp must provide a clear cut-off line in the illuminated zone on the projection screen for vehicle inspection. Figure 1 shows the test points and zones on the projection screen for inspecting the light intensity of the headlamp. During the inspection, the automotive headlamp is 25 m away from the screen, and the screen needs to have enough space to display the light pattern illuminated by the headlamp. The cut-off line is horizontal on the left side of the vv line, and on the right side is the polyline formed by the points HV, H1, H2, and H3. The segment between HV and H1 has a 45\({}^{\circ}\) angle to the horizontal, and the segment between H2 and H3 has a 15\({}^{\circ}\) angle to the horizontal [29]. To maintain the uniform standard during the inspection, the LED lamp module applies 13.2 V. The ECE R112 regulation emphasizes the light intensity (cd) requirement of the passing beam measured on the screen, which requires the measuring points to comply with their respective specification. The intensity can be calculated from the illuminance on the screen as:  
\[I(h,v)=(h,v)r^{2}/cos\gamma \tag{1}\]  
In Equation (1), \(E_{\text{25m}}\) (\(h\),\(v\)) is the illuminance measured at the point on the screen; \(r\) is the distance between the headlamp and the measurement point; \(\gamma\) is the projection angle. Table 1 lists the intensity required for each measurement point on the screen to ensure that the corresponding area on the road has appropriate illuminance, according to Ref. [29]. In the test point angular coordinates, R and L means on the right side and left side of the vv line in Figure 1, respectively; U and D means on the upper side and downside of the hh line in Figure 1, respectively. The headlamp specification is classified into CLASS A and CLASS B, identified by particular photometric provisions. The asymmetrical LED headlamps currently apply to CLASS B. Zone I is the road area close to the vehicle. Zone IV is the farther area from the vehicle, so its minimum intensity must be above 2500 cd to ensure driving safety. Zone III is the area outside the cut-off line of light and dark, and its maximum intensity must not exceed 625 cd to avoid glare oncoming vehicles. Considering the safety of oncoming vehicles, the maximum intensity of 75L and 50L is limited to 10,600 cd and 13,200 cd, respectively. 75R and 50R are the key points of vehicle lighting, so the regulation requires that the two intensities must be at least 10,100 cd or more; the minimum intensity at 50 V must be greater than 5100 cd. The light aiming 25L  
and 25R doesn't directly illuminate the oncoming car. However, it needs to illuminate the wide area close to the car for the driver to see the road clearly, so their minimum intensities must be above 1700 cd. According to the above regulations, each area on the screen requires maximal or minimal intensities. In addition to the light shape and the cut-off line requirements, the intensity for each measurement point is important for the car headlamp design. Thus, the luminous flux output from the headlamp must be kept as stable as possible. When the luminous output of the LED chips decreases as the ambient temperature increases, the LED headlamps that originally complied with the regulations may not meet the requirements of the regulations. Therefore, this issue must be considered in advance for designing LED headlamps to ensure that the LED headlamps still comply with the regulations in practical use, which can improve the safety of vehicles.