System for scanning halftoned images

Details System for scanning halftoned images System for scanning halftoned images

1989-09-18

1991-01-22

Coles, Sr., Edward L.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358454, 358456, 358458, H04N 140

Patent

active

049874969

ABSTRACT:
A process for scanning halftoned images with a sampled or electronic imaging system includes the steps of first optically low-pass filtering the scene, then oversampling the scene at a rate several times that required for display bandwidth, and finally putting the resulting data through an electronic or digital low-pass filter/resampling operation to reduce the system data load. The oversampling advantageously shifts unwanted aliasing between the halftone and sampling frequencies to frequencies above the display bandwidth, so that the aliasing may then be filtered out without affecting signals within the bandwidth of the display.

REFERENCES:
patent: 3588224 (1971-06-01), Pritchard
patent: 4515193 (1986-03-01), Greivenkamp, Jr.
patent: 4616266 (1986-10-01), Hennig
Joseph Shou-Pyng Shu et al., "Moire Factors and Visibility in Scanned and Printed Halftone Images," Optical Engineering, Jul. 1989, vol. 28, No. 7, pp. 805-812.
Yao-Ming Chao, "An Investigation Into the Coding of Halftone Pictures", D.Sc. Thesis, Massachusetts Institute of Technology (1982).
"Reduced Moire-Effect Charge Coupled Device", IBM Tech. Disc. Bull., vol. 20, No. 9, Feb. 78, pp. 3752-55.

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