Which LCD should I choose? C-STN or TFT? Or any other LCD? I know TFT are expensive and they consume more power, but they provide superior image quality. I need to choose color LCD which is clearly visible from 10mm glass.
We have used various monochrome STN and color TFT. No direct experience with the C-STN, but the mono STN have been quite noisy. Needed extra filtering on some control lines. This may also be a concern if a touch-screen is in use.
Depends on the color. Based on OSRAM's specs, yellow seems to have the longest lifetime, at 50k hours (that's 100% brightness, 100% of the time, until it drops to 50% lumens). Other colors are as low as
10k hours, or just over a year. Note that this is a fundamental of LEDs themselves, not just OLEDs, but you only really notice the problem when it appears as "burn-in" on the display.
However, note that some oled manufacturers are dropping their display lines. A lot of their oled matrix displays are either already obsolete, or will be out of production soon. Check with the manufacturer before designing them in.
OLEDs also cost more than LCDs; a 2.7" 128x64 monochrome (16 levels) display is $37 (qty 1).
If cost isn't an issue, also check out VFDs. They're even more expensive ($165 for that size) but, like OLEDs, they're emissive vs reflective (i.e. the elements themselves produce light, rather than blocking a backlight like LCDs do) so "off" is *really* off, and on is really on. This comes in handy when the display will be used in a dark room, as you don't get the "glowing grey rectangle" effect that a backlit LCD has.
50k hours is equivalent to most industrial CCFL LCD backlights - although you can change those!
I think one of the OLED application notes I saw gave a lifetime
*assuming a certain percentage* "on" time - so you have to be careful to read the small print.
It does seem like they are still very much niche products. Still much more expensive than LCD when I last looked (a few months ago).
I quite like VFD - the last time I had one was ~25 years ago in one of the early pocket calculators. Much nicer than the later LED and LCD displays. Funny they still have a role to play, considering the revolution in display technology since then.
I'll assume you mean _through_ 10 mm of glass. Well, that's a bit more than usual to put in front of an LCD panel, but no particular burden.
Let's see: size, resolution, op./non-op. thermal range, mechanical ruggedness, long-time stability, ambient brightness, update speed, available power --- and I'm quite sure I missed some important criteria.
If it's behind 10 mm of glass, I'd bet it's going into a hazardous area enclosure. Make sure it isn't too far behind the glass, or you can have parallax problems and glare. Make sure to try viewing the display under direct sun, and with polarized glasses on. I've come across some POS terminals that got the polarization "wrong", so the display is completely black with my shades on; I would have to bend my neck 90 degrees to read it.