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Inspecting a LC display through acrylic glass

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Hello,

 

I need to inspect a LC display under a acrylic glas plate. The camera and the ring lightning are mounted perpendicular to the display. The problem are the reflections from the acrylic glass plate. P1234 (upper left) illustrates that. So I tried a polarization filter on the lens and could reduce the reflections only a little bit but got also distortion from the acrylic glass (P1234 upper right; ignore the foil on the acrylic glass). The next step was to put a additional polarization filter on my lightning. First I turned the filter on the lens so that I got the best contrast of the screen and subsequently turned the lightning with the second filter so that the reflections were minimal. The reflection was still too bright so that I can not inspect my screen.

 

Because of the perpendicular mount of the lightning I get the reflection. So I tried to hold the lightning at another position and could achieve better images (P1234 lower left) but also shadows because the display is mounted a few millimeter below the acrylic glas. P1234 (lower right) shows the LC display illuminated from two sides and I think that the result is quiet good. Do you think that a background correction could improve that result?  Or should I use another lightning system (dome with coaxial lightning)?

 

What can you suggest my to solve my problem?

 

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Solution
Accepted by topic author Andreas_Elster

Lighting from two sides should give good results, as long as the lights are off to the sides far enough.  The image looks good to me.

 

Another possibility is indirect lighting.  Put a large white diffusing surface about where the camera is, with a hole for the camera to look through.  Bounce the light off the white surface to light the LCD.

 

Bruce

Bruce Ammons
Ammons Engineering
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Hi Bruce,

 

lighning from two sides solved my problem. For indirect lightning I have not enough space.

 

Best regards

Andreas Groh

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