Hunter SpectraProbe XE, Hardware User Manual, Page: 14 / 78

1-4 Introduction 11/02
The Sensor
The SpectraProbe XE sensor is rugged and designed for use in industrial applications. It is mounted
with the sensor window facing the product. The sensor monitors the product’s reflected light and sends
color information to the computer. The sensor is insensitive to ambient light and so does not need to
make direct contact with the product.
How the Sensor Works
Color measurements are taken at a rate of twenty readings per second using a xenon pulse lamp.
Depending upon the instrument configuration, the transmitted light illuminates an area of either 30 mm
(1.25” small area view) or 65 mm (2.5” large area view ) in diameter on the moving product at a 0°
(normal) angle. Reflected light from the product is viewed circumferentially at 45° through a ring of
nine symmetrically-spaced optical fibers. The reflected light is then directed into the polychromator
assembly where a holographic diffraction grating disperses the light into its spectral component
wavelengths. A 128-channel silicon detector array captures the diffracted light and converts the light
energy into electrical signals representing the reflectance of the product at 10 nm intervals from 400 to
700 nm wavelengths. The signals are amplified and processed by a digital signal processor (DSP) to
generate color values based on a user-selected illuminant, observer angle, and color scale.
The optics of the sensor are illustrated below.
Tile holder
Z-axis bellows
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