Image reading apparatus which eliminates moire patterns by magni

Facsimile and static presentation processing – Facsimile – Recording apparatus

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Details

358285, 358293, H04N 1393, H04N 104

Patent

active

048129151

ABSTRACT:
Disclosed is an image reading apparatus wherein an image of a document is projected on an image sensor at an enlarged magnification of N times the normal magnification. This causes an electrical reduction circuit to reduce its input data by 1/N times the input. The data for determining the magnification N is stored in a memory from which the data corresponding to one of a plurality of levels selected by the operator is read out. The moire pattern due to a difference in phase between the dot pitch and the reading pitch is elminated by the optical enlargement. On the other hand, the moire pattern due to the periodic characteristics of dither processing is removed by the optical enlargement which eliminates a low-frequency component of the read data and by the electrical reduction which slightly alters the phase of read data.

REFERENCES:
patent: 4390235 (1983-06-01), Minoura
patent: 4673972 (1987-06-01), Yokomizo
patent: 4675727 (1987-06-01), Sekizawa et al.
patent: 4682243 (1987-07-01), Hatayama
patent: 4724330 (1988-02-01), Tuhro
patent: 4740844 (1988-04-01), Yoshimura
patent: 4751376 (1988-06-01), Sugiura et al.
patent: 4771473 (1988-09-01), Sugiura

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