US 4,232,342 A · Multiplexing for facsimile systems

Abstract

Facsimile systems, having a plurality of uniformly spaced scanning and printing elements in a linear array along their direction of advance, are coupled by time division multiplexed signals comprising a first component representing a sequence of light levels along an image line which are sampled cyclically, a second component representing completion of one sampling cycle and beginning of another as the scanning elements advance, and a third component representing a fixed reference position which each of the scanning elements pass. Apparatus for generating the signal includes a cyclical circuit which is illustrated by a rotary switch operated by a stepping motor having one contact for each photodetector to generate the first component and one contact to generate the second component which may also be used for the third component. The three signal components are distinguished by pulse width which is determined by dwell time on the contacts. A facsimile receiver includes a serial to parallel register to accumulate first signal components and to release them to control printing elements when a second component is received. The second component also provides a synchronous driving frequency for the printing elements. The third component is used to generate an error signal for correcting printing element position.

Claims13

Dependent claims

A method for controlling a graphic receiver by a remote graphic transmitter through a time division muliplexed signal, said grahic receiver having a plurality of uniformly spaced printing elements in a linear array advancing at the same speed along a line parallel to the printing elements and said graphic transmitter having a corresponding plurality of uniformly spaced scanning elements in a linear array advancing at the same speed along a line parallel to the scanning elements comprising the steps of

detecting at each of the scanning elements a level of light reflected from a document to generate a corresponding signal amplitude,
sampling sequentially in a predetermined order the signal amplitude from each of the scanning elements to generate a sequence of first signal components,
advancing the scanning elements to adjacent elemental areas of the document, generating a second signal component at a time separate from the first signal components to represent a complete sampling of the signal amplitudes,
repeating the previous steps and generating a third signal component at a time separate from the first signal component when a scanning element advances to a reference position,
transmitting to a remote receiver through a single channel a representation of the first, second, and third signal components in a time sequence of their generation,
separating the first, second, and third signal components in the receiver,
accumulating the first signal components in a predetermined order following a second signal component to provide serial to parallel conversion of the first signal components,
transferring said accumulated first signal components in response to the second signal component to control the printing elements in the predetermined order of scanning so that an image is formed on a receiving surface in the same order as the detected light levels on the document surface,
advancing the printing elements to adjacent elemental areas of the receiving surface to form an image in response to the first and second signal components,
detecting a printing element at a reference location and measuring a time difference between said detection at the reference location and the third signal component, and
changing the rate of advance of the printing elements to eliminate said time difference thereby synchronizing the position of the printing elements with the scanning elements.

8 more elements

Apparatus for generating a time division multiplexed signal in a facsimile system to control a plurality of simultaneously operating printing elements in a linear array comprising

a linear array of scanning elements grouped to correspond to a plurality of contiguous segments of a document line,
means to project an image of elemental areas of the document line upon the scanning elements,
means to select one of the elemental area images of each segment of the document line to develop a corresponding amplitude at each of the groups of scanning elements,
means to sample sequentially in a predetermined order the amplitude at each of the groups of scanning elements, and
means to transform the sequence of amplitudes into a corresponding cyclical first signal component representing in each cycle an elemental area from each of the segments for transmission through a channel for transformation in a graphic receiver to control the simultaneously operating printing elements.

2 more elements

Dependencies are inferred from the claim text.

Multiplexing for facsimile systems

Life of this patent

Multiplexing for facsimile systems

Life of this patent

Abstract

Claims13