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Browse Prior Art Database

Electrostatic Print Head for the Reproduction of Grey Scale

IP.com Disclosure Number: IPCOM000093847D
Original Publication Date: 1966-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Bennett, RM: AUTHOR [+2]

Abstract

Halftone reproductions achieve apparent grey scale by varying the size of spots, i.e., picture elements, placed on a well-defined rectangular matrix. Darker areas dictate larger spots and lighter areas dictate smaller ones. This technique achieves variable spot size in electrostatic printing by continuously oscillating the stylus.

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Electrostatic Print Head for the Reproduction of Grey Scale

Halftone reproductions achieve apparent grey scale by varying the size of spots, i.e., picture elements, placed on a well-defined rectangular matrix. Darker areas dictate larger spots and lighter areas dictate smaller ones. This technique achieves variable spot size in electrostatic printing by continuously oscillating the stylus.

In drawing A, a mechanical up-down oscillation characterizes recording 10 at right angles to horizontal scan 12 on paper 14. The amplitude of this motion plus the length in time of the fixed amplitude stylus impulse signal determines the size of the individual picture element spots 16, 18, 20, 22 in the matrix. The wave shape of the oscillation signal can be sinusoidal, rectangular, triangular, etc. Its amplitude is made proportional to the blackness of the pictures being scanned.

Three methods for mechanically oscillating the stylus are shown in drawings B, C, and D. In drawing B, stylus 24 is made of a magnetic material and is oscillated by electromagnetic head 26. It is mechanically attached at 30 to spring 28 and to mount 32 where it connects to a source of constant amplitude video signals. In drawing C, stylus 34 is deflected by magnetostrictive ribbon 36. The latter constricts in the presence of a magnetic field provided by coil 38. In an alternative, it can be attached to a magnetostrictive bar which is used as the fixed mount, thus eliminating spring 40. In drawing D, s...