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Optoelectronics/Displays??

Machine vision for automated LCD display testing

Posted: 17 Jun 2015 ?? ?Print Version ?Bookmark and Share

Keywords:dead pixels? LCD displays? sensors? Machine Vision? Vision Option?

In theory, one could calculate the optimum solution but this would require detailed knowledge of the physics and optics of the components so the practical approach of adjusting both variables to find a working solution was used and only took a week.

We initially thought that aligning the camera and the display in parallel would mean that there would be no Moir patterns but actually the best angle is 45 degrees. Combined with the optimal distance between the camera and the display and the Moir pattern disappears.

As a result, the automatic testing now only takes a couple of seconds per unit and is highly reliable as the human element is removed. Removing the cost of the human element is also important, as several people would have been required on a rotation basis to avoid eye fatigue.

Figure 2: Rotating by 45 degees removes Moir patterns.

Automating as many processes as possible is the key to being competitive in contract manufacturing. China is losing its edge of ultra cheap labour and customers are realising that highly automated production facilities can be price competitive with the advantages of being located nearby to ensure quality and a short distance and time for goods to be delivered to their markets.

About the author
Thomas Eschenmoser is Section Head Test Engineering at ESCATEC.


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