Symbol reader using differentiating circuit for light beam focusing
AssigneeSumitomo Electric Industries, Ltd.
InventorShinya Takenaka
Life of this patent
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Abstract
A symbol reader for reading symbols on a symbol surface. An optical system including a laser, condensing lens and scanning mirror illuminate a symbol surface to be read with a laser beam, scanning across the symbol surface. A transducer measures the amount of light reflected from the symbol surface. A differentiating circuit develops a differential coefficient indicative of the change of light intensity as light scans the symbols being read. A control system adjusts the optical system illuminating the symbol surface so as to maximize the differential coefficient, thereby minimizing the diameter of the light beam to allow for adequate reading of the symbol surface at variable distances.
Claims15
A symbol reader for reading a symbol from a symbol surface, comprising:
- means for illuminating the symbol surface with a read beam of light, the illuminating means including:
- a light source,
- a first condensing lens for condensing light from the light source, and
- scan mirror means for scanning a symbol surface and symbols to be read with light transmitted through the first condensing lens;
- a transducing element for receiving light reflected from the symbols and symbol surface, and producing a read signal indicative of the intensity of reflected light;
- differential coefficient means, responsive to the read signal, for providing a differential coefficient indicative of intensity change in the reflected light;
- control means, responsive to the differential coefficient, for adjusting a distance between said first condensing lens and said light source to maximize the amplitude of the differential coefficient;
- and
- means for processing the read signal so as to interpret the scanned symbols.
Dependencies are inferred from the claim text.