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The photometry of retroreflectors using a computer‐controlled four‐axis goniometer
Author(s) -
Johnson Norbert L.
Publication year - 1982
Publication title -
color research and application
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.393
H-Index - 62
eISSN - 1520-6378
pISSN - 0361-2317
DOI - 10.1002/col.5080070411
Subject(s) - goniometer , retroreflector , optics , photometry (optics) , calibration , computer science , computer vision , physics , laser , stars , quantum mechanics
A photometric range for measurement of retroreflectance using a computer‐controlled four‐axis goniometer for positioning the test specimen and a computer‐controlled observation‐angle drive is described. The four‐axis goniometer allows for positioning of all types of retroreflectors in the CIE (α, β 1 , β 2 , ϵ) geometric system and has the flexibility to provide direct angular positioning in other geometric systems. The observation‐angle drive allows accurate alignment of the observation angle at variable test distances. Included is a description of the calibration methods used to insure photometric accuracy and stability for the duration of the measurement. The control of both the photometric and geometric systems uses peripheral devices interfaced to a central computer. Computer programs are outlined that provide output in terms of selected sets of angles at which measurements are required to verify performance in user specifications. Also described are graphic outputs of retroreflectance versus angle which are used to characterize the intrinsic performance of retroreflective materials.