Semi-retroreflective scanners
First Claim
1. A system for reading indicia having areas of differing light reflectivity on a target, comprising:
- a light source for producing an outgoing light beam;
a scanning first optical element for receiving the light beam and producing a scanning outgoing light beam therefrom;
a second optical element for receiving the scanning light beam and redirecting the scanning beam in a direction towards the target so as to produce a scan across the indicia to be read;
a light detector having a field of view for detecting the light reflected from said indicia and producing electrical signals responsive to the light received;
the scanning first optical element receiving light reflected back from the indicia and directing such light to the detector, so that the detector images a field of view across the indicia.
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Accused Products
Abstract
A semi-retroreflective optical scanning system has an optical scanning element which directs a scanning light beam via a stationary holographic optical element in a scan path across indicia to be read. Light from the indicia is collected by an optical collector, such as a lens or a mirror, which focuses it onto a small optical detector via the scanning element. The field of view of the optical detector scans across the indicia in synchronization with the outgoing scanning beam from the holographic optical element. Since the incoming reflected light is not limited by the aperture of the scanning element, the signal-to-noise ratio remains high even when a small scanning element is used. In a further embodiment the light source, scanning element collector and detector are provided in a common plane, the collector and scanning element sharing a common optical axis and a light source being provided substantially off axis to allow reduction in the scanning element size. In a further aspect of the invention a solid state reader is provided capable of establishing the distance to the target by sensing the exact position on the detector at which the target is imaged. According to yet a further aspect of the invention the problem of specular blinding is overcome by providing a plurality of sensors activated in a dynamic on-off sequence, for example a random sequence.
45 Citations
34 Claims
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1. A system for reading indicia having areas of differing light reflectivity on a target, comprising:
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a light source for producing an outgoing light beam; a scanning first optical element for receiving the light beam and producing a scanning outgoing light beam therefrom; a second optical element for receiving the scanning light beam and redirecting the scanning beam in a direction towards the target so as to produce a scan across the indicia to be read; a light detector having a field of view for detecting the light reflected from said indicia and producing electrical signals responsive to the light received;
the scanning first optical element receiving light reflected back from the indicia and directing such light to the detector, so that the detector images a field of view across the indicia. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A scanner for reading indicia having areas of differing light reflectivity, the scanner comprising:
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a light source for producing a light beam; a scanning first optical element for receiving the light beam and producing a scanning outgoing light beam therefrom; a second optical element for receiving the scanning light beam and redirecting the scanning beam in a first direction to scan across an indicia to be read; and a light detector having a field of view; whereby light reflected back from the indicia in a second direction corresponding to the first direction is received at the scanning first optical element and is directed to the detector, thereby scanning the field of view of the detector across the indicia.
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27. A reader for reading indicia having areas of differing light reflectivity, comprising
a light source for producing an outgoing light beam; -
a scanning first optical element for receiving the light beam and producing a scanning outgoing light beam therefrom; a second optical element for receiving the scanning light beam and re-directing the scanning beam towards the indicia; a collector for collecting light reflected from the indicia and directing the collected light towards the first optical element; and a detector for detecting collected light reflected from the first optical element;
wherein the light source, first optical element and collector are provided in a common plane, the collector and first optical element being provided on a common optical axis and the light source being arranged to generate a beam at a substantial angle to the common optical axis. - View Dependent Claims (28, 29, 30, 31, 32)
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33. A reader for reading indicia having areas of differing light reflectivity on a target, comprising:
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a light source for producing an outgoing light beam; and at least two detectors spaced apart from one another for detecting light reflected from the target wherein the detectors are arranged to be switched on and off in a dynamic sequence. - View Dependent Claims (34)
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Specification