Detection of an one-way mirror transmittance by line spectrometry

The paper describes a system for light spectrum detection of an one-way mirror transmittance by line spectrometry. The system is composed of a focusing lens, a dispersion device and a monochromatic camera. The focusing lens system determines the Region Of Interest (ROI), consisting of a slight rectangular area that can be considered as a linear array of adjacent cells, and sent the light emitted by the region to the entrance slit of the dispersion device. The light rays emerging from the dispersion device hit the area sensor of the camera, that produces an image composed by the spectra of the elementary cells of the ROI. The paper reports a processing procedure for transforming raw data produced by the camera into transmittance or reflectance data. The system allows to measure spectra in the range 380-780 nm, with spectral resolution of about 5 nm. The spatial resolution, that is the dimension of the cells of the ROI, can be set by the imaging lens. The paper describes also an application realized to determine the spectral transmittance of transparent or semi-reflective mirrors and plates.