GB1411540A - Colourimeters - Google Patents

Abstract

1411540 Photo-electric colorimeters PAINT RESEARCH ASSOCIATION 24 Nov 1972 [27 Aug 1971] 40373/71 Heading G1A [Also in Division G2] In a colour measuring apparatus in which light reflected from a surface being monitored is gathered by a plurality of light guides 14, the light issuing from each light guide is divided into a number of portions (36), Fig. 3 (not shown), each portion is incident upon a different wavelength filtering part of a filter 50 whose absorption wavelength varies across its width, and the light passing through the filter is incident upon a photo-cell 60 whose output is indicative of the colour of the surface. The divided light guide ends (36) are directed to the slits (42) in a mask 40, each slit corresponding to a band-width of about 20nm for a filter 50 whose absorption wavelength varies from 400 to 700 nm. Thus each slit receives light from all the light guides and directs this light to the corresponding portion of the filter 50. Between the mask and the filter is located an arrangement 44 of parallel neutral filters, one for each slit in the mask 40. The density of each neutral filter is chosen so that the output from photo-multiplier 60 represents one of the three primary stimuli X, Y, Z of the C I E standard observer, or some other colour function. To derive the other two stimuli, two different neutral filter arrangements 44 are used. The filter arrangement 44 may be replaced by an array of adjustable slits, and the intensity at each wavelength may be monitored in turn by employing a shutter with a slit. The ultraviolet fluorescence properties of samples may be monitored.