Northern Telecom Limited

David R Baraff

Richard W Streater

Nur M Serinken

Carla J Miner

Steven Kos

Robert J Boynton

Vladimir F Drobny

Frederick Caldwell Livermore

William D Westwood

Hussein M Naguib

Blair K MacLaurin

John R Long

Lawrence H Hobbs

A matrix multiplexed field effect display has switch devices at matrix crosspoints to provide a turn-on threshold for the field effect material. The switch devices are thin film metal-insulator-metal (MIM) switches. The display is operated at low current so that the MIM switches, which may be deposited on glass, do not degrade rapidly in use.

Displays controlled by MIM switches of small capacitance

In known thin film switch controlled matrix multiplexed liquid crystal displays (LCD's), alternating pulses of an applied waveform are of reverse polarity. If the transient behaviour characteristic of the switches controlling the LCD is not saturated during application of a selection pulse, the selected pels may experience a relatively low RMS voltage in the ON state. To ensure that selected pels are fully turned on, the addressing waveform proposed consists of a series of pulses of one polarity followed by a corresponding series of pulses of opposite polarity. Transient effects are minimized by applying the series of unipolar pulses and the pels are consequently subjected to a high RMS voltage. However, net DC current through the LC is still zero as required in order to guard against irreversible electrochemical degradation of the LC. The higher RMS voltage can be used to improve contrast ratio or to increase the level of multiplexing.

Addressing scheme for switch controlled liquid crystal displays

A matrix multiplexed display cell has thin film switch devices at matrix crosspoints to provide a turn-on threshold for electrooptic liquid used in the cell. Each of the switch devices has two parallel branches of diodes, the diodes in one branch being of reverse polarity to those in the other. The cell is operated at low current so that the switch devices, which are deposited on glass, do not degrade rapidly in use.

LCDs (Liquid crystal displays) controlled by thin film diode switches

A photoconductive device for imaging a linear object has a plurality of photoconductive elements, extending in a line, on a substrate, with first and second patterns of electrical conductors, a pattern on each side of the line. Connections are made to the elements. The conductor patterns are formed as columns on one side of the line and as rows on the other side to provide connections between columns and elements and rows and elements such that the number of external connections is minimized. By applying a voltage to a column, and then connecting a detector current sequentially to each row, and repeating for each column, the current flowing through each element can be determined and a signal generated related to the illumination of each element. The elements can be a continuous bar of photoconductive material.

Photoconductor device for imaging a linear object

Any element of a thermal print bar of resistive material is heated by a current pulse passed across the bar between an appropriate conductor pairing. Certain conductors are deposited in two parts with a rectifying layer deposited between the parts to provide diode isolation of heating paths from one another.

Thermal printers

A matrix multiplexed display cell has thin film switch devices at matrix crosspoints to provide a turn-on threshold for the electro-optic liquid used in the cell. Each of the switch devices is a back-to-back pair of diodes. The cell is operated at low current so that the switch devices, which are deposited on glass, do not degrade rapidly in use.

Each thick film resistive print element of a thermal print bar operated in a scan mode is series connected to a thick film switch which sets a voltage threshold to isolate the element from periodic scan pulses unless coincident with an element selecting data pulse in which case the thick film undergoes joule heating which causes it to switch and its series-connected resistive element undegoes joule heating.

Each element of a display operated in a scan mode is series connected to a thick film switch which sets a voltage threshold to isolate the element from periodic scan pulses unless coincident with an element selecting data pulse in which case the thick film switches and the element, for example, a nematic liquid crystal cell, operates.

Displays using thick film switches to control individual display elements

Instead of imaging a line across a document by a lens system on to an imager, direct imaging is obtained by positioning the document in close proximity to but spaced a predetermined distance from a linear array of photo-detectors and illuminating the document by light from beneath the detectors, the light passing through spaces between detectors and being reflected back to the detectors. To prevent saturation of the dectectors by light direct from the illuminating means, opaque material is positioned beneath the detectors with gaps or apertures through which light can illuminate the document. The detectors can be spaced close together to give desired resolution, or spaced a predetermined distance apart and the detector head stepped laterally. More than one line of detectors can be provided.

Direct imaging apparatus for an electronic document transmitter

A thermal printing bar, as for a facsimile printer, has a pattern of associated conductors on each side thereof to produce two rows of hot spots in the printing bar. The hot spots in one row are offset relative to the other row. By suitably sizing the hot spots, the spots in one row will at least completely fill the gaps between the spots in the other row, or can even overlap. By this means, the one row is first printed on the paper; the paper moved by the distance between the centers of the rows and then the other row printed. This provides contiguous or overlapping spots on the paper, giving improved contrast.

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Ottawa, Canada

David R Baraff