Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1997-09-04
2000-08-29
Patidar, Jay
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
3241581, 382149, G01R 3102
Patent
active
061114243
ABSTRACT:
An in-process method for testing an active plate of a flat panel display, such as a liquid crystal display (LCD), is disclosed. An infrared thermal analyzer, including an infrared (IR) camera and an image analyzer, is preferably utilized for recording and analyzing heating response characteristics of the active plate upon application of an appropriate electric signal. An active plate is tested during the fabrication process using IR thermography techniques to evaluate the IR emission of the active plate when an electric voltage uniformly powers the array of pixels in the active plate. The testing technique of the present invention exhibits minimal invasiveness, as only the shorting bars of the active plate are electrically assessed. The heating response characteristics of the active plate are preferably not evaluated until the active plate reaches a stable operating temperature. In the absence of defects, each pixel in the array heats up uniformly, and upon detection by an infrared camera, a uniform IR image is obtained across the plate. If there are defects in the active plate, however, such as one or more open lines, short circuits, or other non-uniform electric parameters, the various pixels in the active plate do not heat up uniformly and will reach different operating temperatures. A defective plate will dissipate IR energy in a non-uniform manner, and upon detection by an infrared camera, a non-uniform image of the active plate is obtained, providing a map of any defects on the plate. The heating dynamics of the active plate can be time-resolved as the pixels of the active plate heat up in response to an applied electric signal. The reliability of an active plate can be evaluated by applying a voltage having a higher magnitude than the typical operating voltage of the flat panel display device.
REFERENCES:
patent: 5309108 (1994-05-01), Maeda et al.
patent: 5406213 (1995-04-01), Henley
patent: 5740272 (1998-04-01), Shimada
"Liquid crystals plot the hot spots."; Electronic Design, pp. 71-79, Sep. 1967.
J. A. Castellano, Handbook of Display Technology (Academic Press, 1992, Ch. 8, Section 8.1.3) pp. 186-196.
Lucent Technologies - Inc.
Patidar Jay
LandOfFree
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