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LCD error detection system
| Details |
Inventors: Young, Steve; Foster, Nigel;
Assignee: Apple Computer, Inc. (Cupertino, CA)
Primary Examiner: Eisenzopf; Reinhard J.
Assistant Examiner: Urban; Edward F.
Attorney, Agent or Firm: Blakely, Sokoloff, Taylor & Zafman
The present invention is an error detection system for liquid crystal display (LCD) devices. The system comprises a photo-scanning device coupled to a computer and a LCD display driver. Faulty LCD cells are detected by using the photo-scanner to produce two images. The first image is produced by displaying a predetermined pattern on the LCD device. This pattern is inverted to produce the second image. By analyzing these two images, faulty LCD cells are located. The results of the analysis give the location of the faulty LCD cells. |
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DETAILED DESCRIPTION OF THE PRESENT INVENTION The present invention describes a liquid crystal display (LCD) device error detection system.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention.
It will be obvious, however, to one skilled in the art that the present invention may be practiced without using these specific details.
In other instances, well-known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.
The present invention uses visual image scanning and computer image analysis to identify faulty LCD cells in an LCD device.
A scanning device similar to a facsimile machine is used to scan the LCD device and produce an electronically storable image.
The image is comprised of pixel data, with each pixel data element having an intensity value giving a measure of light intensity measured at the particular position in the image.
Black and white (or monochrome) LCD devices have an intensity value, indicating the shade of gray.
For color LCD devices, the intensity value will have three components indicating the shade of the three primary colors (red, green and blue).
After scanning, a computer then processes scan images.
The first step in processing the scan image is to balance it.
Balancing an image involves adjusting the intensity of pixels so a standardized contrast value appears from an image.
Specifically, the difference between the highest and lowest intensity values is adjusted to a predetermined constant.
With this information, the scan image is normalized.
The step of balancing is not absolutely essential to detect faulty LCD cells, but it greatly facilitates the further analysis.
Next, the location of faulty LCD cells is determined.
A third image is created by summing the gray values of corresponding positions in the scan image and the inverted image.
Analysis involving these three images determines the location of faulty LCD cells, using methods including thresholding and connectively analysis
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LCD 
