ECE/SAE Dual Functional Superpin Plus Curved Reflex Reflector By
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applied sciences Article ECE/SAE Dual Functional SuperPin Plus Curved Reflex Reflector by Use of New Structured Corner Cubes Hien-Thanh Le 1,2, Lanh-Thanh Le 1,2, Ming-Jui Chen 1, Thanh-Hong Lam 3, Hsing-Yuan Liao 1, Guo-Feng Luo 1, Yung-Cheng Li 4 and Hsiao-Yi Lee 1,5,* 1 Department of Electrical Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 80778, Taiwan; [email protected] (H.-T.L.); [email protected] (L.-T.L.); [email protected] (M.-J.C.); [email protected] (H.-Y.L.); [email protected] (G.-F.L.) 2 Department of Technology, Dong Nai Technology University, Bien Hoa 810000, Dong Nai, Viet Nam 3 Department of Computer Science, Vietnamese-German University, Thu Dau Mot 820000, Binh Duong, Viet Nam; [email protected] 4 Department of Materials Science and Engineering, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan; [email protected] 5 Department of Graduate Institute of Clinical Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan * Correspondence: [email protected] Received: 31 October 2019; Accepted: 2 January 2020; Published: 8 January 2020 Abstract: We propose and demonstrate, using optical experiments, a new reflex reflector structure called SuperPin Plus. The structure is composed of special pin groups with dihedral-angle offsets in corner cubes. One of the specular features brought by this new design is that it can comply with both the US SAE (US Society of Automotive Engineers) standard and the EU ECE (Economic Commission for Europe) standard, so that manufacturing costs of reflex reflector for both European and American automobile markets can be reduced. By using genetic algorithms for optimization, the angles and the positions of the pins, which are the building elements of corner cube reflectors, serve as the parameters to tune up the performance of the SuperPin Plus curved reflex reflector. Compared with conventional ECE flat regular retro-reflectors, we found that not only can we achieve a 41% higher retro-reflection efficiency with the ECE SuperPin Plus flat reflex reflector, but that SuperPin Plus can also act as a reflex reflector within SAE standards. In addition, we demonstrate that the retro-reflection efficiency is 30.5% higher (SAE standard) and 42.7% higher (ECE standard), and that a 32% increase in working area can be achieved if double pin groups are used to construct the corner cubes instead of a single pin arrangement, in a curved SuperPin Plus reflex reflector. Keywords: optics design; double pins with corner cubes; SuperPin Plus curved retro-reflector; EU ECE regulations (Economic Commission for Europe); US SAE regulation (US Society of Automotive Engineers) 1. Introduction A reflex reflector is an optical device that allows light to be reflected in a direction that is parallel to that of the source [1–3]. The corner cube array is the typically used structure and such an array can be built up through pin grouping to generate the expected retro-reflected light [4–6]. Reflex reflectors on cars or signage can increase visibility in the dark for safety [7,8], so they have been applied extensively in vehicle applications [9]. Due to their high tolerance to the direction of incident waves [10–12] retroreflectors have been used extensively in many applications instead of Appl. Sci. 2020, 10, 454; doi:10.3390/app10020454 www.mdpi.com/journal/applsci Appl. Sci. 2020, 10, x FOR PEER REVIEW 2 of 15 extensively in vehicle applications [9]. Due to their high tolerance to the direction of incident waves Appl.[10–12] Sci. 2020retroreflectors, 10, 454 have been used extensively in many applications instead of plane mirrors2 [13]. of 16 For instance, regular reflex reflectors [14–16], as shown in Figure 1a, can diverge the reflected energy planeinto multiple mirrors light [13]. beams For instance, with equal regular emitting reflex reflectorsangle intervals [14–16 [17–19],], as shown and inthese Figure are1 currentlya, can diverge the most the reflectedcommonly energy used intoretro-reflecting multiple light devices beams for with vehicles equal [2 emitting0,21]. In angle contrast intervals to regular [17–19 reflex], and reflectors, these are currentlySuperPin thereflex most reflectors commonly not only used reflect retro-reflecting light beams devices but also for vehiclesconcentrate [20, 21them]. In to contrast amplify to the regular light reflexintensity reflectors, of signals SuperPin for observers, reflex reflectors as shown not in only Figure reflect 1b [22]. light Owing beams butto the also highly concentrate effective them retro- to amplifyreflection the ability, light intensitySuperPin of retro-reflectors signals for observers, have been as shown replacing in Figure regular1b[ retroreflectors22]. Owing to thein vehicle highly eapplicationffective retro-reflection markets [17,21,23]. ability, SuperPin retro-reflectors have been replacing regular retroreflectors in vehicleAccording application to regulations markets [17 ,of21 ,the23]. US Society of Automotive Engineers (SAE) and EU Economic CommissionAccording for toEurope regulations (ECE), ofreflex the USreflectors Society for of vehi Automotivecles need to Engineers return light (SAE) to an and observer EU Economic located Commissionat 0.2 degrees for (SAE Europe regulations) (ECE), reflex and reflectors 0.33 degrees for vehicles (ECE needregulations) to return above light tothe an light observer source located [23], atrespectively. 0.2 degrees Therefore, (SAE regulations) corner cube and arrays 0.33 composed degrees (ECE of pins regulations) need to be designed above the and light produced source with [23], respectively.different specification Therefore, for corner the cuberequirements arrays composed of ECE and of pins SAE need reflex to bereflectors, designed respectively. and produced In with this dipaper,fferent a specificationnew reflex reflector for the requirementsstructure called of ECESuperP andin SAE Plus reflex is proposed reflectors, for respectively. fitting both Inthe this ECE paper, and aSAE new regulations, reflex reflector shown structure in Figure called 1c. SuperPin SuperPin Plus’s Plus isprinciple proposed is based for fitting on the both structure the ECE of SuperPin and SAE regulations,[24], which was shown developed in Figure by1c. the SuperPin difference Plus’s in the principle value of is dihedral based on angle. the structure of SuperPin [ 24], whichThe was reflex developed reflector by can the switch difference its function in the value from of ECE dihedral to SAE angle. or SAE to ECE just by rotating pins groupThe 45° reflex in structure, reflector so can one switch type itsof pin function is enou fromgh to ECE handle to SAE the or production SAE to ECE of justECE by and rotating SAE reflex pins reflectors. Flat SuperPin Plus reflex reflectors and curved SuperPin Plus reflex reflectors with the new group 45◦ in structure, so one type of pin is enough to handle the production of ECE and SAE reflex reflectors.corner cube Flat structure SuperPin Plusare proposed reflex reflectors and anddemons curvedtrated SuperPin to meet Plus the reflex ECE/SAE reflectors dual with function the new cornerrequirements cube structure through are experiments. proposed and By demonstrated using genetic to algorithms meet the ECE for /optimization,SAE dual function we use requirements the angles throughand the experiments.positions of Bythe using pins genetic serving algorithms as the buildi for optimization,ng elements we of usecorner the anglescube andreflectors the positions as the ofparameters the pins servingto enhance as the the building performa elementsnce of the of SuperPin corner cube Plus reflectors curved reflex as the reflector. parameters Compared to enhance with theconventional performance regular of the retro-reflectors, SuperPin Plus curvedit is foun reflexd that reflector. not only Compared can 41% with higher conventional retro-reflection regular retro-reflectors,efficiency be achieved it is found with thatthe ECE not onlySuperPin can 41% Plus higher flat reflex retro-reflection reflector, but e ffitheciency SuperPin be achieved Plus can with also theact as ECE a SAE SuperPin reflex Plusreflector. flat reflex It is shown reflector, that but a 32 the% SuperPin larger working Plus can area also can act be as achieved a SAE reflex if double reflector. pin Itgroups is shown are thatused a to 32% construct larger workingcorner cubes area instead can be achievedof the single if double pin arrangement pin groups arein a usedcurved to constructSuperPin cornerPlus reflex cubes reflector. instead of the single pin arrangement in a curved SuperPin Plus reflex reflector. (a) (b) Figure 1. Cont. Appl. Sci. 2020, 10, 454 3 of 16 Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 15 (c) FigureFigure 1.1.The The formulaformula ofof retro-reflectedretro-reflected lightlight byby ((aa)) thethe EUEU EconomicEconomic CommissionCommission forfor EuropeEurope (ECE)(ECE) regularregular inin ([([16],16], FigureFigure1 ),1), ( (bb)) the the ECE ECE SuperPin SuperPin inin ([([24],24], Figure Figure1 ),1), and and ( c(c)) the the ECE ECE and and US US Society Society ofof AutomotiveAutomotive Engineers Engineers (SAE) (SAE) SuperPin SuperPin Plus Plus reflex reflex reflector, reflector, an an extension extension of of SuperPin SuperPin [24 [24].]. AccodingAccoding toto thethe standardsstandards ofof SAESAE andand ECE,ECE, thethe coecoefficientfficient ofof luminous luminous intensityintensityR RI I shouldshould bebe higherhigher thanthan thethe thresholdthreshold valuesvalues withinwithin thethe 2020°◦ angle angle ofof lightlight