## 3 Experimental Setups and Analysis  
In order to demonstrate the performance of the SuperPin Plus CCR, the pin element for corner cubes with 2.75 mm cross sectional size and dihedral angles \(\delta\)1 = 0.12\({}^{\circ}\); (\(\alpha\) = 90.12\({}^{\circ}\)); \(\delta\)2 = 0.12\({}^{\circ}\); (\(\beta\) = 90.12\({}^{\circ}\)); and \(\delta\)3 = 0.01\({}^{\circ}\) (\(\gamma\) = 90.01\({}^{\circ}\)) are made by CNC process and bundled as a flat array testing CCR sample, as shown in Figure 6. In optical testing processes, the sample is tested for ECE regulation verification first, and then it is rotated 45\({}^{\circ}\) for SAE regulation measurement. For comparison, one flat SAE regular CCR and one flat ECE regular CCR are also put in an optical setup to test. The optical setup for reflex reflector regulation testing is established, as shown in Figure 7, with a 633 nm diode laser operated with a 5 mW output acting as the light source, and the distance between the laser and the curved reflex reflector set to 30.5 m to measure the reflected light spot. Based on the laser spectrum specification, its coherence length is calculated to be about 0.5 mm, which is less than the corner cube dimension of 2.75 mm in the experiments. Therefore, the retro-reflected output spots were spatially incoherent, and the laser can be considered as an incoherent light source for the following retro-reflector testing experiments. Figure 5: **(a)** The orientation of the corner cube reflector for EU Economic Commission for Europe (ECE) regulations. **(b)** The reflected intensity distribution accomplished by the corner cube reflector for ECE regulations. **(c)** The orientation of the corner cube reflector for US Society of Automotive Engineers (SAE) regulation, which is the 45\({}^{\circ}\) rotated corner cube reflector for ECE regulations. **(d)** The reflected intensity distribution accomplished by the corner cube reflector for SAE regulations. The laser light had an incident angle of 0\({}^{\circ}\) with respect to the car driving direction, as it shone on the tested CCR with a spot area of 520 mm\({}^{2}\). As a result, several retro-reflected light spots can be found on the black screen located 30.5 m away from the test sample. A Minolta T10 illuminance meter was used to measure the illuminance of the sample and of the retro-reflected light spot in order to get the incident light illuminance (in lux) and the retro-reflected light intensity (in candela). The coefficient of luminous intensity \(\mathbf{R_{I}}\) and retro-reflection efficiency \(\mathbf{R_{A}}\) of the test sample can be obtained through calculation of the measured data to ensure that the tested CCRs can pass US SAE regulations and EU ECE regulations. The testing output light patterns of the ECE SuperPin Plus CCR, the SAE SuperPin Plus CCR, the flat ECE regular CCR, and the flat SAE regular CCR are shown in Figure 8a-d, respectively. Based on the measured data in Figure 8, comparing the light reflection performance of \(\mathbf{R_{I}}\) between the regular CCRs and the SuperPin Plus CCR, the results show that the light reflection performance of the new design is higher than that of the regular ones. In detail, the \(\mathbf{R_{I}}\) values of the flat SuperPin Plus sample under ECE working conditions at 0\({}^{\circ}\), 10\({}^{\circ}\)U, 10\({}^{\circ}\)D, 20\({}^{\circ}\)L, and 20\({}^{\circ}\)R are 20,002 millicandela (mcd)/lux, 10,214 mcd/lux, 7863 mcd/lux, 7318 mcd/lux, and 8871 lux/mcd, respectively, shown in Figure 8e The \(\mathbf{R_{I}}\) values of the flat SuperPin Plus sample under the SAE working mode at 0\({}^{\circ}\), 10\({}^{\circ}\)U, 10\({}^{\circ}\)D, 20\({}^{\circ}\)L, and 20\({}^{\circ}\)R are 12,318 mcd/lux, 6227 mcd/lux, 4442 mcd/lux, 4586 mcd/lux, and 4904 lux/mcd, respectively, shown in Figure 8f.