Automatic measurement of spectral bidirectional transmittance distribution function on translucent optical materials

•A measuring platform of spectral bidirectional transmittance distribution function is set.•Data acquisition and control software are integrated to realize automatic measurement.•The facility has a broad angle range, wide dynamic response and short collection time.•The measurement error is no more than 3.28%.•It provides a method for spectral and spatial transmission measurement.

A measurement platform of spectral bidirectional transmittance distribution function (BTDF) with a full three dimensional spatial coverage is developed based on a fiber spectrometer, a tungsten–halogen lamp and a 3D mechanical rotation angle system. The measurement software and the control software are integrated to realize the automatic measurement. The measurement equipment has a broad spectral coverage, a large angle range, a wide dynamic response and a short acquisition time. The measured spectral range is 380–760 nm with 0.04 nm spectral resolution. The measured angle range is 0–80° in zenith angle and 0–360° in azimuth angle with 0.01° angle resolution. The dynamic range is 107 and the minimal integration time is 1 ms. The measurement of spectral BTDF on translucent frosted glass is performed and a large amount of measured data is obtained with the measurement error no more than 3.28%. It provides a reliable description facility for spectral and spatial transmission characteristics of the translucent materials.