Self diagnostic and repair in matrix display panel

Abstract

A matrix access system having a plurality of columns, comprising a plurality of circuits each being adapted for selectively accessing one of said columns; an interface, communicating data with said plurality of circuits; at least one redundant circuit, adapted for selectively accessing each of said columns and communicating data with said interface; a test circuit, for comparing data communicated by a respective one of said circuits and said redundant circuit; and means for selectively logically replacing a respective circuit with said redundant circuit.

Description

FIELD OF THE INVENTION [0001] The present invention relates to the field of self-repair of matrix accessed integrated electronics systems, and more particularly to matrix display panels with integrated drivers capable of self-diagnostic and repair through the use of redundant driver circuitry. BACKGROUND OF THE INVENTION [0002] The integration of column drive circuits on a silicon display panel potentially reduces the cost of display systems, but may also reduce the panel fabrication yield substantially. This is the obvious result of the inclusion of sensitive small geometry active circuit elements on the substrate. [0003] One of the advantages of building a reflective active matrix projection display with liquid crystal on silicon is that the drivers can be integrated with the active matrix itself. This should improve performance and reliability, and lower the total system cost. By integrating the digital to analog conversion on the display panel, a purely digital interface can be ...

AI Technical Summary

Benefits of technology

[0009] The column drive circuitry for a matrix display consists mostly of a large number of identical circuits, one for every column. By providing at least one spare column driver and a control circuit within each block of drivers, the system can automatically detect and identify faulty column drivers, which are then functionally replaced with a spare driver. Thus, with the addition of a small amount of extra circuitry, the effective yield can be improved.

[0010] In one embodiment, the output of the normal column drivers are systematically compared with the output of a spare column driver, to detect flawed normal column drivers, for example during a power on self test or continuously during operation. In the event of detection of an error, the spare column driver substitutes its output for the output of the defective normal column driver. In a second embodiment, the output of each adjacent pair of column drivers are compared for the same input signal. The column driver under test is disconnected from its associated column, while the adjacent, and all “higher” column drivers are switched to be associated with the column of the “lower” adjacent column driver circuit. In the case of a difference, the “higher” column driver is presumed to be operative, and persistently substitutes for the “lower” column. If the column drivers both produce the same output signal (within a specified tolerance), the scan and test circuit proceeds to test the next adjacent pair of column drivers, with all column drivers “lower” than the column driver under test being connected to their associated column. A spare column driver circuit is provided at the “higher” end of the block, so that if one column driver defect is identified, each column is still provided with an operative driver circuit. In this way, a defective column driver per block does not impair overall device functionality.

Problems solved by technology

The integration of column drive circuits on a silicon display panel potentially reduces the cost of display systems, but may also reduce the panel fabrication yield substantially.

However, a large active circuit area may increase the chances for production defects substantially.

In addition, some pixel defects are generally acceptable as long as they result in dark point defects in the image.

Defects in the data conversion and driver circuitry, however, typically cause one or more rows or columns to fail, a result that is unacceptable.

Therefore, when the dense active circuit area for data conversion and drivers increases, the production yield may be adversely affected, which raises the cost.

This takes valuable time and the mechanics of the fuse programming may be difficult to implement.

Therefore, standard laser activated fuse programming is difficult to perform.

Another reason is that the blowing of a fuse may actually create damage to the die surface that can easily compromise the tight tolerances on the narrow gap of liquid crystal cell on top of it.

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