Author Topic: Inverted LCD backlighting?  (Read 830 times)

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Offline RyuKojiro

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Inverted LCD backlighting?
« on: March 19, 2017, 02:34:26 am »
I thought I had a good enough understanding of LCD backlight technology (there's a light and a matte in the back, and the LCD can block that flat light in order to produce a dark area). However, I've always been under the impression that devices which instead light up areas just had an opaque substance blocking the areas intended to always be dark, and instead drew the liquid crystal away from pixels/segments in order to light an area.

I recently found these pictures of an HP 3478A with a backlight "upgrade" that does inverted lighting, but I don't understand how that could work. I highly doubt they are making their own HP 3478A compatible LCDs. So, how are they doing this inverted style of backlighting? I'm assuming my previous understanding was wrong/incomplete, and I'd love to know how to do this myself!


Offline MrBungle

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Re: Inverted LCD backlighting?
« Reply #1 on: March 19, 2017, 04:18:11 am »
It is done with the polarising filters.
Back in the late 80's when I was in high school there was a brand of calculator(I think Casio, but could've been Sharp) that had loose polarising filters (today they are typicaly adhered to the glass) and one could easily swap the front and back filters to reverse the display.

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