powered depending on the filter chosen for the transmissive filters 21 stray light can be measurement or spectral accuracy verified if a time integrating optical detector measurement instrument such as a photo detector array based spectrograph is employed system linearity can be measured by deploying the white reference standard 7 and the illumination lamp 3 powered and the shutter filter wheel 18 positioning the open apertures 30 over the optical pickup fibers 4 then sampling the captured light at varying integration times set in the optical detector measurement instrument spectral resolution and accuracy can be measured by deploying the white reference standard 7 while the illumination lamp 3 is de powered the shutter filter wheel 18 positions the open apertures 30 over the optical pickup fibers 4 and the spectral line source 29 is powered light from the spectral line source 29 will reflect off the white reference standard 7 and a potion thereof is subsequently captured by the optical pickup fibers 4 the light captured by the optical pickup fibers 4 can be processed yielding both spectral accuracy and spectral resolution during material sampling the white reference standard 7 is retracted as shown in fig2 the illumination lamp 3 powered and the shutter filter wheel 18 positioned such that the open apertures 30 are over the optical pickup fibers 4 light from.