Image reading apparatus for producing high quality images based

Details Image reading apparatus for producing high quality images based Image reading apparatus for producing high quality images based

1991-06-18

1993-08-17

Coles, Sr., Edward L.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358462, 358467, 358448, 358443, 358500, H04N 140, H04N 146

Patent

active

052374319

ABSTRACT:
An image reading apparatus including an A/D converter for converting an analog detection signal read by an image reading sensor to a digital signal, a logarithmic converter, in which density levels to be converted are divided into a plurality of regions, for converting an output of the A/D converter to a logarithmic value, a decoder for judging a density region of the logarithmic converter based on the output of the A/D converter, and a bit shifter for converting an output of the logarithmic converter to a density signal in accordance with a judgment made by the decoder. The image reading apparatus as constructed above can maintain the tone level of an 8-bit signal, thereby producing high-quality images. Further, 10-bit signals can be subjected to shading correction while using an inexpensive 8-bit memory.

REFERENCES:
patent: 4553160 (1985-11-01), Yamamoto et al.
patent: 5132786 (1992-07-01), Ishiwata

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