Colorimetry-based retardation measurement method with white-light interference

Abstract

A colorimetry-based retardation measurement (CBRM) method is presented. The specimen, between crossed polarizers, is illuminated with a white-light source. The retardation that is due to the birefringence of the specimen produces a white-light interference color. The x, y chromaticity coordinates of the color produced are measured with a spectrophotometer. The resulting x, y values are compared with a retardation x, y database that we obtained by measuring the retardation with an accurate Senarmont compensator and the x, y chromaticity values along the length of a 0-4-order quartz wedge. The technique was validated by the measurement of a variety of retardation plates. The retardation accuracy (mean error) of the CBRM method is shown to be 3.6 nm. The resolution is +/-0.2 nm, and the measurement range is 5-2150 nm. The method substitutes for a polariscope and eliminates errors associated with quarter-wave plates. The CBRM method does not utilize any moving parts and thus is fast and can be automated.

Photoinduced Bending Behavior of Cross‐linked Azobenzene Liquid‐Crystalline Polymer Films with a Poly(oxyethylene) Backbone

“…The retardation is defined by the follow equation: where R is the retardation of the film, and n e and n o are the refraction index of extraordinary ray and ordinary ray, respectively. Δ n means the birefringence of the film, and d is the film thickness.…”

Review of RGB photoelasticity

“…The model, illuminated in white light, is placed between two crossed polarizers. A spectrophotometer, however, is used in place of a colour camera [51].…”

Applicability evaluation of the stress-optic law in Newtonian fluids toward stress field measurements

“…To fulfill the requirements mentioned in Sec. II D, the so-called RGB photoelasticity (e.g., [32][33][34]) and the colorimetry-based retardation measurement method (e.g., [35]) would seem to offer plausible solutions because they use a single color camera and relatively simple optical settings. These methods measure n or from the color information, and the stress-optic law can be utilized if the photoelastic coefficient C is predetermined.…”