Optical reading apparatus with automatic gain control circuit
AssigneeNippondenso Co., Ltd.
InventorsMasahiro Hara, Toshiyasu Sakai
Life of this patent
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Abstract
In an optical reading apparatus having a reading sensor for converting optically readable information into an electrical analog signal, an automatic gain control circuit is provided to maintain the amplitude of the electrical signal constant. The gain of the automatic gain control circuit is controlled such that the average or peak voltage of the electrical signal derived from the reading sensor is detected and held until next scanning effected by the reading sensor so that a variable impedance element included in the automatic gain control circuit will be controlled in accordance with the held voltage to maintain the amplitude of the electrical signal constant.
Claims11
An optical reading apparatus for converting information which is optically readable by an image sensor into an electrical signal, comprising:
- clock generator means for generating first and second pulses, and for applying multiple of said first pulses to said image sensor to thereby enable optical reading of said information, said multiple pulses constituting a scanning operation, and for generating one of said second pulses at the completion of one of said scanning operations;
- means for producing from said image sensor said electrical signal;
- means, responsive to said generated second pulses, for sampling the voltage amplitude of said electrical signal, and for holding said sampled voltage until a next scanning operation;
- automatic gain control circuit means, responsive to said sampled voltage, for automatically controlling the amplitude of said electrical signal.
Dependencies are inferred from the claim text.