Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1994-03-21
1996-07-30
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250568, 250225, 235470, G06K 710
Patent
active
055414192
ABSTRACT:
A symbology reader which reduces the effects of specular reflection. A plurality of illumination sources emit light toward a target object. A first polarization filter receives the unpolarized light from the illumination sources and transmits only light polarized in a first direction. Light reflected from the target object travels back to the reader where it is received by a second polarizer which is oriented to block light polarized in the first direction and transmit only light polarized in a second direction orthogonal to the first polarization direction. Non-specularly reflected light reflected from the target object is largely transmitted by the second polarizer to a detector assembly within the symbology reader. In one embodiment the polarization filters are part of a window which covers an output aperture of the reader. The polarization filters are implemented as discrete pieces of laminar polarizing film attached to a transparent window base. In an alternative embodiment, a wavelength filter is employed to block ambient light at wavelengths other than the wavelength of the illumination sources to improve the sensitivity of the detector assembly to reflected illumination light.
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Allen Stephone B.
Intermec Corporation
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