Thomas P. Brody

A 6 × 6 inch 20 lines-per-inch liquid-crystal display panel

An integrated 14 000 picture element 36-in2flat screen display panel has been constructed by a combination of thin-film transistor and nematic liquid-crystal technology. The design, fabrication, and present performance of the panel is discussed. The design of the peripheral circuits, which permit the presentation of low resolution off-the-air TV pictures on the panel is described in another paper.

A transformation with invariance under cyclic permutation for applications in pattern recognition

The paper describes a transformation that can be used to characterize patterns independent of their position. Examples of the application of the transform for the machine recognition of letters are discussed. The program succeeded in a recognition rate of 80–100% for letters having different position, distortions, inclination, rotation up to 15° and size variation up to 1:3 relative to a reference set of 10 letters. Results with a program for the autonomous learning of new varieties of a pattern (using a learning matrix as an adaptive classifier) are given. When executed on a digital computer, this transform is 10–100 times faster than the fast Fourier transform (depending on the number of sampling points).

The thin film transistor—A late flowering bloom

The thin film transistor was the first solid-state amplifier ever patented, but has found no practical application until quite recently. The history of this device is traced from the early and unsuccessful Bell Labs experiments, through its brief resurgence in the 1960s as a competitor to the MOSFET; its second disappearance from public view followed by years of hibernation at Westinghouse Labs; its emergence in the 1970s as a candidate for forming very large area integrated circuits for flat panel displays, leading to the present era of intensive, worldwide exploitation as a device which has at last found a suitable problem to solve. The present state of the art of TFTs made of CdSe, poly- and amorphous silicon is reviewed, particularly as it pertains to their current predominant use in high resolution/high performance liquid crystal displays, followed by some views on the future for TFTs in active matrices and, possibly, in other human size or macro-electronic components and systems.

A 6 × 6-in 20-lpi electroluminescent display panel

Over the last two years, we have been working on a solution of the solid-state display addressing problem which consists of building the addressing circuits (and eventually, also scanning or decoding circuits) directly on the panel, and fully integrated with the particular display medium. The technique utilized for this approach is that of a vacuum-deposited thin-film transistor matrix. In this paper, we report on the design, construction, and performance of a 12 000 element EL panel, suitable for alphanumeric, vectorgraphic, and monochrome TV image presentation. The basic circuit, repeated at every picture element, consists of an X-Y-addressed logic transistor, a power transistor, and a storage capacitor. The entire circuit was fabricated through multiple evaporations in a multisource system using one pumpdown cycle. The finished thin-film circuit is covered with a sprayed EL-phosphor. An evaporated Au/PbO layer forms the continuous top electrode. The entire display panel is finally sealed with a glass cover plate. Reproducible fabrication of good-quality displays was achieved, with >99 percent of the elements operational. Excellent alphanumeric displays with very few defects were demonstrated. Contrast ratios >50:1 (ON:OFF under dark ambient) were obtained. Power consumption under typical alphanumeric display conditions was below 1 W, with a peak brightness of 40 fL.

A 350 character TFT-EL display

In this paper we report the extension of the resolution to 30 lpi so that the 6 x 6 inch plate now consists of ~28,000 individually addressable elements. In addition, a significantly increased lit area per element is reported as well as major improvements in device performance.

When — If ever — Will the CRT be replaced by a flat display panel?

Solid-state components have replaced vacuum tubes across the entire field of information processing, with the significant exception of the cathode ray tube, which looks unassailable. The only other field where vacuum tubes have retained a foothold is that high power transmission. The CRT is in a seemingly anomalous position — it handles information, not power, so why has it not been replaced yet? This article is an attempt to find some basic clues to this paradox, and to utilise these clues in an indirect attack strategy which might work.

Integrated Electrooptic Displays

By an integrated display we understand a subsystem in which a significant or major portion of the display electronics is assembled or fabricated on a common substrate which itself forms the display surface. As the number of display elements increases and approaches that of a cathode-ray tube, the extension of the concepts and techniques of large-scale integration to the display field becomes mandatory, for both technical and economic reasons. Matrix addressing is employed in most attempts to build higher resolution displays. Passive matrix addressing schemes however present many problems, particularly with display materials having a slow response to electrical excitation. This paper reviews the work so far carried out on integrated nonemissive displays, with particular emphasis on recent work involving the use of “active matrices”. Such matrices contain gain-producing, switching and/or memory elements at every mesh point, and represent the most ambitious thrust to date toward full display integration. An attempt is made to establish the scope and limitations of the various schemes employed, and the direction of probable future developments are indicated.

Performance of a 350 character TFT-LC display panel

The problems encountered in increasing the resolution of a 6 × 6 TFT addressed liquid crystal display from 20 lpi to 30 lpi are described, together with the solutions developed. The major problem relates to the reduced capacitance of the LC element resulting in a lack of frame period storage. Two approaches were utilized: the first consisted of a systematic effort to analyze the factors that influence off leakage current in the TFT. As a consequence of this a TFT with leakage current of less than one nanoampere was achieved. The alternate approach was to incorporate an extra 5 pF capacitor in each display element. A layout of the matrix circuit was developed which incorporated the capacitor under the gate bus bar, thereby avoiding a sacrifice in the active area of the display element. Both approaches were successful and good quality displays fabricated. Electrical design considerations, TFT fabrication principles and performance of the resulting 6 × 6 30 lpi TFT-LC panel will be presented.

Thin film transistor arrays for parallel optical logic: The image negator

Thin film transistor (TFT) arrays have significant potential for parallel optical processing applications. The design fabrication and operation of 128×128, 1 sqins, TFT-photoconductor-electroluminescent array is described. It performs the logical NOT function at every picture point and also provides amplification.