## 3 Experimental Setups and Analysis
The measured coefficients of luminous intensity \(\mathbf{R_{I}}\) of the SuperPin Plus CCR are all higher than the regulation requirement of ECE and SAE, shown in Table 1. Based on the data shown in Figure 8, we can conclude that the retro-reflection efficiency of the SuperPin Plus CCR is 41% higher comparing to the ECE regular one, and can have the same regulation level as the SAE regular one, respectively. Figure 6: The flat SuperPin Plus corner cube retro-reflector (CCR) sample built by pin array. Figure 7: Experimental setup for testing samples (flat and curve). In order to extend the ECE/SAE dual functional advantage from a flat SuperPin Plus CCR to a curved SuperPin Plus CCR, the SuperPin Plus pin elements are connected side by side with their tips touching the curved plane of a commercial curved CCR, serving as the initial design of the curved SuperPin Plus CCR. The commercial curved regular CCR made of PMMA (polymethyl methacrylate) shown in Figure 9 provided by OWL LIGHT AUTOMOTIVE MFG. CORP (Lukang, Chunghua, Taiwan) is used as the reference to design a SuperPin Plus curved retro-reflector. The commercial curved regular CCR and the initial SuperPin Plus curved CCR design are shown in Figure 9,b, respectively. The cross section working surface of the design is 146 mm \(\times\) 34 mm. Through TracePro software simulation, the anterior, central, and posterior regions of the ECE (SAE) SuperPin Plus curved CCR result in their retro-reflected light intensity distributions for an incident beam in the driving direction, as shown in Figure 10. The locations of the probing regions and the car's driving direction of the CCRs are presented in Figure 11. As the simulation results are shown in Figure 10, the anterior and the central regions areas can reflect light up to 0.2\({}^{\circ}\) and up to 0.33\({}^{\circ}\), but the posterior area can not. Therefore, we conclude that it is difficult for the posterior area to meet ECE or SAE regulation requirements. Figure 8: Comparison of the coefficient of luminous intensity \(\mathbf{R_{I}}\) between the flat regular CCR and the flat SuperPin Plus CCR. Figure 11: The areas for testing of SuperPin Plus curve (each area is 520 mm\({}^{2}\)). Figure 10: The \(\mathbf{R_{I}}\) and intensity distributions on anterior, central, and posterior regions, which are shown in: (**a–c**) SAE SuperPin Plus curved; (**d–f**) ECE SuperPin Plus curved. Figure 5:0 (**a**) The commercial regular curved reflex reflector sample. (**b**) The pin and the primary curved SuperPin Plus reflector design composed of pins. In order to remedy the ineffective posterior working area of the commercial design, two groups of pins were connected as the double pins group to compose the SuperPin Plus curved CCR, as shown in Figure 5:1 Fifteen pieces of double-pin groups were arranged in parallel to the car driving direction to form the primary curved CCR; one pin group touches the curve reference surface, and the other one is free to translate in the car driving direction. The height difference between the neighboring pins in a group of double pins and the double pin group are named \(\mathrm{d_{i}}\) and \(\mathrm{D_{i}}\), respectively. The object function \(f\) defined by Equation (8) was determined in the optimization process. The optimization process encompassed three fragments. Object function: The equation that describes the value of the object function of the optimization program established by genetic algorithms is as follows:  
Figure 5:2  
where \(w_{i}\) is the weight parameter of the object function, \(m_{i}\) is the value of the measured target, which is determined by the intensity sensor through each optimal loop when running the program, and \(t_{j}\) is the optimization target defined with a value corresponding to the retro-reflective light intensity on the retroreflector plane.