Image reader

Details Image reader Image reader

1990-08-07

1993-03-02

Coles, Sr., Edward L.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358448, 358447, H04N 140

Patent

active

051914450

ABSTRACT:
There is provided an improved image reader. In the image reader, light from an object is converted into an analog signal by a photoelectric converter. The signal is quantized by an A/D converter on the basis of top and bottom reference voltages to produce a digital picture signal. A digital picture signal corresponding to a dark current flowing to the photoelectric converter is stored in a memory as a dark current data. Also a digital picture signal corresponding to the optical strength of predetermined level is stored in another memory as a white level data. Then, the top and bottom reference voltages are produced which correspond to the top and bottom quantization-threshold values on the basis of the dark current and white level data, respectively. The top and bottom reference voltages are then respectively applied to the A/D converter to produce the digital picture signal without signal distortion.

REFERENCES:
patent: 4511928 (1985-04-01), Colomb
patent: 4660082 (1987-04-01), Tomohisa et al.
patent: 5130822 (1992-07-01), Nagata et al.

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