A fibre optical system for reflectance measurement of plane surfaces

Abstract

A simple fibre optical design for reflectance measurements of plane surfaces has been developed and tested. The reflectance system was standardized with a PF10-03-P01-Plane mirror. Average reflectance from the plane mirror was 99.7%, 99.5% and 70.0% for the 1310 nm, 850 nm LED sources and 632.8 nm He-Ne laser respectively. Average reflectance decreased with decreasing wavelength. Steel and aluminium metal plates showed different trends in average reflectance values. The microscope slide and glass block depicted similar trends as compared to the plane mirror. Surface scans recorded showed variations in reflected intensity, which depicts irregularities on the surface. It was observed that reflectance of the Sony 700 MB CD-R was higher than the CD-WR samples and also it revealed that reflectance decreased abruptly at the boundary between a data recorded section and a non-data section on both CDs. Reflectance for new and expired pharmaceutical tablets showed great variance. The values for new tablets were on average, about 18% higher than for expired tablets. The general results also showed that light intensity depends on the varied longitudinal displacement of the samples as intensity falls off by 1/𝑒2. There is the suitability of the reflectance design to be used for quality control as reflectance is a unique property of any material. The optical design is reliable and versatile and can be adapted to quality controlled systems.