Symbology reader wth reduced specular reflection
First Claim
1. A window for reducing specular reflections, mountable in a symbology reader, the symbology reader having an illuminating light source within a housing producing a beam of unpolarized light directed along a predetermined optical path toward a target object for illumination a symbology on the target object, and a detector assembly for receiving light reflected by the symbology in the optical path, comprising:
- a planar lens mountable to the housing, the lens including a first area and a second area, the first area being positioned in the optical path, and the second area being positioned between the target object and the detector assembly to receive light reflected from the target object when illuminated by the light source;
a first polarizer at the first area of the lens, the first polarizer being oriented to transmit light substantially of a first polarization; and
a second polarizer at the second area of the lens, the second polarizer being oriented to transmit light of a second polarization substantially orthogonal to the first polarization.
9 Assignments
0 Petitions
Accused Products
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.
315 Citations
12 Claims
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1. A window for reducing specular reflections, mountable in a symbology reader, the symbology reader having an illuminating light source within a housing producing a beam of unpolarized light directed along a predetermined optical path toward a target object for illumination a symbology on the target object, and a detector assembly for receiving light reflected by the symbology in the optical path, comprising:
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a planar lens mountable to the housing, the lens including a first area and a second area, the first area being positioned in the optical path, and the second area being positioned between the target object and the detector assembly to receive light reflected from the target object when illuminated by the light source; a first polarizer at the first area of the lens, the first polarizer being oriented to transmit light substantially of a first polarization; and a second polarizer at the second area of the lens, the second polarizer being oriented to transmit light of a second polarization substantially orthogonal to the first polarization. - View Dependent Claims (2, 3)
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4. A symbology reader for reading a symbology on a region of a target object, the symbology having a plurality of areas of different reflectance, comprising:
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an illuminating light source for producing light polarized in a first circular polarization direction, the light source being oriented to emit the circularly polarized light along an optical path toward the region of the target object; a first optical element positioned to receive light reflected from the region of the target object, the first optical element converting the reflected circularly polarized light to linearly polarized light polarized in a first direction; a first polarizer positioned to receive light from the first optical element, the first polarizer transmitting light linearly polarized substantially in the first direction and inhibiting the passage of light linearly polarized substantially in a second direction orthogonal to the first direction; and an optical detector assembly positioned to receive the light linearly polarized in the first direction transmitted by the first polarizer and producing electrical signals in response to light transmitted by the first polarizer wherein the illuminating light source includes; a light source for producing unpolarized light and oriented to emit unpolarized light along the optical path; a second polarizer in the optical path to receive the unpolarized light from the light source, the second polarizer transmitting light linearly polarized substantially in the first direction and inhibiting the passage of light polarized substantially in the second direction; and a second optical element positioned to receive linearly polarized light from the second polarizer, the second optical element converting the light linearly polarized in substantially the first direction to circularly polarized light polarized in the first circular polarization direction and transmitting the circularly polarized light to the region of the target object. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A symbology reader, comprising:
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a housing; a window for reducing specular reflections, mountable in the symbology reader; an illuminating light source within the housing producing a beam of unpolarized light directed along a predetermined optical path toward a target object for illuminating a symbology on the target object; and a detector assembly for receiving light reflected by the symbology in the optical path; wherein the window includes; a lens mountable to the housing, the lens including a first area and a second area, the first area being positioned in the optical path, and the second area being positioned between the target object and the detector assembly to receive light reflected from the target object when illuminated by the light source; a first polarizer at the first area of the lens, the first polarizer being oriented to transmit light substantially of a first polarization; and a second polarizer at the second area of the lens, the second polarizer being oriented to transmit light of a second polarization substantially orthogonal to the first polarization. - View Dependent Claims (11, 12)
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Specification