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The primary purpose of the 0:45 reflectometer is to disseminate color standards to the color and appearance community. The instrument was designed to provide calibrated reflectance color standards with a color difference, ΔE*ab, between two color samples being less than 0.5. Particular attention was given to the inherent properties of the instrument such as stray light, band pass error, random noise, and wavelength uncertainty.
The 0:45 reflectometer consists of a source section, a sample section, and a detection section. The illuminator provides a monochromatic, polarized influx beam centered on the sample compartment of the sample wheel with a triangular spectral bandwidth of 5 nm at full width half maximum (FWHM). The illuminator consists of a dual-source illuminator, filter wheel, double monochromator, telecentric aperture, light chopper, ellipsoidal and flat mirrors, beam-splitting silica window, monitor diode, and polarizer. The source illuminator holds a 150 W Xe arc lamp used for wavelengths of 460 nm or shorter and a 100 W quartz-tungsten-halogen (QTH) incandescent lamp used for longer wavelengths. The radiant flux reflected from the silica window and a folding mirror is measured with a monitor receiver equivalent to the sample receiver. The illumination at the sample plane is 10 mm by 12 mm with a 5 nm spectral bandwidth and polarization either parallel (0°) or perpendicular (90°) to the plane of illumination.
The sample section consists of a rotating sample holder that holds and positions the sample and standards in the incident beam. The sample wheel is custom-made and is mounted on a computer control rotation stage. The wheel is 81 cm in diameter, fabricated from one piece of aluminum, and has 20 sample compartments. Each sample compartment can be individually aligned. Samples with widths from 3 cm to 10 cm and heights from 3 cm to 20 cm can be accommodated.
The receiver consists of a lens, telecentric aperture, silicon photodiode, and current-to-voltage and lock-in amplifiers. A computer is used for automated data acquisition, control, and analysis.
Comparisons and check standards ensure that instrument is operating within its uncertainties on a measurement-to-measurement basis while periodic realizations of the scales are used to maintain the traceability of the instrument.