Avian Technologies LLC
P.O. Box 716
Sunapee, NH 03782-0716
603-526-2420 (office), 603-526-2729 (fax)
The GCMS-3B system is designed for measuring gonio-apparent materials. These are materials that change color appearance depending on the viewing and illumination angles. Examples are pearl-mica coating surfaces and interference pigments. For these types of materials, this gonio-spectrophotometric color measurement system can measure its color by measuring the spatial distribution of reflected (or transmitted) light at user-selectable angles of illumination and detection.
Based on the precise control on the incident and acceptance angle, the measurement of the spectral distribution of every pair of illumination and detection angles are performed individually. After calibration and mounting of the samples, the settings for measurement conditions are made. Once the measurement begins, the operations of the instrument are completely automatic, and color system proceeds to capture spectral reflectance data at each angle pair selected. Measurement states can be saved to file and retrieved for repeating the same sets of angle pairs.
The data achieved by this kind of measurement can be widely used as the basic data in the development of gonio-apparent material matching. The data can also be applied as the input to computer graphics rendering models.
The GCMS-3B can make measurements of a wide variety of gonio-chromatic applications including:
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The sample to be measured (5) is clamped into place on the sample stage with manually-adjustable tilt (“flop”) angle (3). This stage accepts samples up to 195 x 220 mm and has a broad aperture to allow a wide range of incident and viewing angles. Fine adjustment of the flop angle can be made by the micrometer assembly (4). During calibration, the sample is replaced by a barium sulphate-coated white standard plate.
The reference white plate (6), also barium sulphate-coated, is positioned in its receptacle and remains in place throughout routine reflectance measurements.
The entire sample platform (2) rotates in accordance with the parameter settings made in the software, between limits of -80° and +80° from the normal (perpendicular to the sample plane).
The lamp housing (1) incorporates a single tungsten halogen source lamp which is divided into two identical beams via mirrors, lenses and heat filters. The sample beam (1S) and reference beam (1R) exit through apertures. The lamp housing rotates on the same axis as the sample platform to provide a variable incident angle, again within the range of ± 80° from the normal.
The light reflected from the sample, and that from the reference white plate enter the sample receptor (7S) and reference receptor (7R) respectively. Each beam is directed to the fixed detection system via a mirror and through a beam chopper assembly. The chopper alternately directs the reference beam and the sample beam to the monochromator via a lens system.
The light from the monochromator is dispersed into each wavelength via a diffraction grating and then is photoelectrically converted by the elements of a photodiode array. The electrical signals are amplified by a wavelength-independent amplifier, transformed to digital signals by an A/D converter, and then transmitted to the PC via a GP-IB IEEE interface for processing into the user-selected colour scales and displays.
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