Interconnection and addressing scheme for LCDs

• US 4,506,955 A
• Filed: 05/06/1983
• Issued: 03/26/1985
• Est. Priority Date: 05/06/1983
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: AT&T, Inc.
• Inventors: Kmetz, Allan R.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Gallivan, Richard F.
• Application Number:
  US06/492,458
• Time in Patent Office: 690 Days
• Field of Search: 350/333, 350/336, 340/784, 340/802
• US Class Current: 345/87
• CPC Class Codes: G01R 13/408 Two or three dimensional representation of measured values
• CPC Class Codes: G02F 1/134336 Matrix

Abstract

Liquid crystal elements are interconnected in an array of rows and columns, which are not independent of one another, and are addressed by pulsed signals which together reduce the number of leads N required to operate the display. The interconnection scheme includes connecting together the last column to the second row, the penultimate column to the third row, etc., and the first column to the last row. In one embodiment for randomly accessing the display, the addressing scheme divides a row-select signal and a column-select signal into two time-wise sequential subsets: a first subset which includes pulses of one polarity in the time slots corresponding to the elements in that row, and a second subset which includes pulses of either polarity depending on which elements in that column are to be turned on and which off. The coincidence of two pulses of opposite polarity applied to an element from the row-select and column-select signals in sufficent to turn on that element. Different addressing schemes are utilized in other embodiments for use as pseudo-analog pointer displays and bargraph displays.

Claims

1. Display apparatus comprising:

a planar liquid crystal device including a plurality of (N-1) row electrodes on one side thereof and a plurality of (N-1) column electrodes on an opposing side thereof, said row electrodes overlapping said column electrodes in different spatial planes so as to define an array of M liquid crystal elements;

said row electrodes being interconnected with said columnn electrodes so that said array is addressable via N row electrodes, where M=(N-1)N/2,

the n-th row and n-th colum of said array each containing (N-n) of said elements and one element in common, where n=1,2, . . . (N-n),

the x-th column electrode (x=1,2, . . . N-1) being connected to the y-th row electrode, where y=N+1-x, and

signal means connected to said N row electrodes for addressing said elements.

2. The display of claim 1 wherein said device is an rms-responding device.

3. The display of claim 1 for addressing element (x,y) corresponding to the overlap of the x-th column electrode with the y-th row electrode wherein said signal means applies to one of said N row electrodes a pulsed row-select signal and to another of said row electrodes a pulsed column-select signal, each having M time slots per frame and each time slot being uniquely associated with a separate element, each frame containing (N-1) pulses divided into two subsets, said row-select signal being applied on the y-th row electrode and containing a first subset of (N-y) pulses of one polarity in the time slots corresponding to the (N-y) elements in the y-th row and second subset of (y-1) pulses one or more of which may have the opposite polarity, and said column-select signal being applied on the (N+1-x)th row electrode and containing a first subset of (x-1) pulses of one polarity and a second subset of (N-x) pulses of either polarity in time slots corresponding to the (N-x) elements in the x-th column, the y-th pulse of said second subset of (N-x) pulses being of opposite polarity if element (x,y) is to be turned on and of the same polarity if (x,y) element is to be off.

4. The display of claim 3 wherein said signal means repeats said row-select and column-select signals in the next frame, each with opposite polarity compared to the prior frame.

5. The display of claim 1 for use as a pointer display wherein

said column electrodes are arranged essentially along a line and said row electrodes follow a meander pattern, and

said signal means applies to each of said N row electrodes a voltage waveform which is a unique member of a set of orthonormal functions, and to turn on an element (x,y) corresponding to the overlap of the x-th column with the y-th row said signal means applies a waveform on the y-th row electrode and an essentially identical waveform on the (N+1-x)th row electrode.

6. The display of claim 5 wherein said signal means applies an orthonormal set of phase-shifted pulse waveforms to said row electrodes.

7. The display of claim 1 for use as a bargraph display wherein

said elements are arranged essentially along a line, and

said signal means applies to each row electrode a pulsed signal having N time slots per frame, m time slots corresponding to m=0,1, . . . (N-1) columns containing only on elements, each of said time slots containing a pulse of one polarity applied to the (N+1-m)th row electrode and pulses of opposite polarity applied to all other electrodes, and in a (m+1)th time slot said signal means applies to the m row electrodes, to which pulses of said one polarity were applied, simultaneously pulses of said opposite polarity and said signal means applies simultaneously to the remainder of said row electrodes, to which pulses of said opposite polarity were applied, pulses of said one polarity, and in a (m+2)th time slot said signal means applies to any mixed column having both on and off elements a pulse of said one polarity to the (N+1-x)th row electrode and simultaneously pulses of said opposite polarity to row electrodes corresponding to on elements in said mixed column and applies a reference voltage simultaneously to row electrodes corresponding to off elements, and in a (m+3)th time slot said signal means repeats the pulses of the (m2)th time slot but with reversed polarity.