Browse Prior Art Database

Characterizing and Tracking Liquid Crystal Display Panel Defects

IP.com Disclosure Number: IPCOM000106601D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 122K

Publishing Venue

IBM

Related People

Cromar, C: AUTHOR

Abstract

Liquid crystal displays (LCD) have direct electrical addressability to each individual pixel, which is utilised in this disclosure to access LCDs for defective picture elements (pixels or dots) on a manufacturing test line. The concept has applications in other areas such as misconvergence and purity errors in displays.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Characterizing and Tracking Liquid Crystal Display Panel Defects

      Liquid crystal displays (LCD) have direct electrical
addressability to each individual pixel, which is utilised in this
disclosure to access LCDs for defective picture elements (pixels or
dots) on a manufacturing test line.  The concept has applications in
other areas such as misconvergence and purity errors in displays.

      Described is a processing method of identifying each pixel
defect on an LCD panel using the actual LCD panel being assessed as
the display media.  It categorises each of any defects on the LCD
panel and stores the coordinates and categories of the LCD defects to
file.  The method also encrypts the coordinates and categories of
defects which are stored.  When required it can decrypt defect
coordinates from storage and present the complete defect
characterisation as it was described at the original identification
stage.

      Displayed on the screen of an LCD display is a dot/pointer
which can be moved around the screen using cursor keys, a touch
screen or a mouse.  Any defects on the LCD panel are located by
moving the dot/pointer to the exact coordinate position of the
defect.  When positioned over the defective pixel, an input is made
causing the coordinates of the dot/pointer to be logged to file (Fig.
1).  A series of queries are then invoked to which an operator
responds allowing the defect(s) to be categorised; e.g., sharp, dull,
light or dark.  When coordinates and error codes for each defect are
stored to file, a software program is run which compresses the
coordinate and categorisation data to ensure that the minimum size of
ASCII string is used for storage.  From the ASCII characters
generated by this data compression program, a barcode label is
printed.  This label should be affixed to the LCD panel or may be
appended to the serial number label.

      Later on using the technique described, any operator equipped
with the decryption program (Fig. 2) and a barcode reader, in the
repair centre or a customer's office can scan the barcode label to
produce a full pictorial analysis, on the LCD panel itself, which
will highlight each defect as described at the assessment stage.
Analysis takes the form of a series of marker icons on the LCD
display on test.  Each icon is chosen to represent the type of defect
as given by the response to the original query for that particular
defect ref KEY in Fig. 3.  Each icon is placed exactly in the
position of the defect.  Using the cursor keys, a touch screen or a
mouse, the operator can toggle the icon to reveal any defect they
choose.  Since the error codes were included as part of the ASCII
string, the operator can obtain a pop-up window which c...