Analysis of surface quality during fabrication of automotive retroreflectors

Abstract

Due to their inherent functionality, retroreflective structures play a vital role in styling and safety that are typically associated with automotive lighting components. The optical performance of the automotive retroreflectors is strongly dependent on the quality of the functional facets that are involved in redirecting the incoming light. To date, virtually all automotive retroreflectors are fabricated through a conventional process commonly termed as “pin-bundling-electroforming” (PBE) or simply “pin-bundling” whose surface quality outcome is largely unknown despite the relatively venerable age of this manufacturing technology. To address this, the main goal of the present study was to perform a quantitative assessment of the quality characteristics associated with the three main phases of the PBE to be then contrasted with those of a newer and more versatile retroreflector fabrication technique called “ultraprecise single point inverted cutting” (USPIC). The results obtained showed that while the average areal roughness of PBE-generated inverted corner cube optical microstructures remains less than half than that of the USPIC-fabricated right triangular prism retroreflectors (9.2–9.5 nm vs 19.7 nm), their average waviness values remain comparable (29.9 nm vs. 32.9 nm). It is expected that the surface assessments presented in the scope of the present study will constitute a valuable baseline for future research efforts aiming to develop retroreflector-fabrication alternatives that are superior to PBE.