Finding a Display You Can Read in the Sun?

max3000 asks: "I'm currently building an embedded device that will be used outdoors, and the technology is pretty much nailed down at this point, except the display. Quite honestly, I'm confused and lost in all the display technologies out there: LCD (TFT, passive/active, and so forth), ChLCD, OLED, FED, AMLCD, EL, electrophoretic, ePaper like eInk, and more (some of which may overlap). Can you help a confused, fellow reader? What I need is (apparently) fairly complicated: an outdoor, sunlight-readable (at-a-glance readable, not squint-your-eyes readable), VGA/SVGA display. The display should have a 4-6 inch diagonal, capable of displaying at least 16 color grayscale, and it should be based on a technology with a roadmap to color in 2-3 years time. If not driveable directly from a PC, the display should come with a development kit that is." What small displays are out there that can meet these specifications?

Evident in the Palm and phones

[jbarr]

"Back in the day" my Pilot 1000, Palm iii, and Palm Vx PDA's all had monochrome, backlit displays that were very viewable in the dark, in normal office lighting, and in bright sunlight. No, they weren't color, but I NEVER had to worry about being able to read the screens. Now, over a decade later we have PDA's that rival small laptops, have amazing storage capacities, execute applications unheard of in the past,but are COMPLETELY USELESS in bright sunlight. Despite all of the advances, I sometimes long for the days of simpler designs. I would personally love to see the Palm Vx resurrected with some of today's features but a high resolution monochrome screen.

And the same holds true for cell phones. I have a typical LG phone from Verizon (provided by work, do I have no choice in the model) and it has a great battery life, the features are decent, and the voice quality is better than most, but in the sinlight, the internal screen is completely unusable. The monochrome external screen is amazingly clear in sunlight, but it is useless in that it doesn't match the internal screen. Thank, God for speed dials.

Cannot do

[thsths]

I think the main problem is that you want both colour and readability in direct sunlight. While transflective displays work very well in bright light, they do not usually come in colour (of if they do, they are very dark). Colour displays usually need a back light, and it is very likely that it cannot compete with direct sunlight.

The math is simple: direct sun light is about 1000 watts per square meter, or 13 watts on your display size. The back light has to be stronger, say twice as bright, but you loose about 50% of the light in the light bulb, in the light distribution, in the polariser and again in the colour filter. So you would need 400 watt of electrical energy to drive the back light!

Short version of the story: colour, good contrast and direct sunlight don't mix. Maybe some day with e-ink, but not right now.

Re:Cannot do

[cpaglee]

Gosh your math is wrong. The 1000 watts of light per square meter is based on the amount of light from a 1000 watt incandescent light bulb. The light from a CCFL fluorescent light bulb would use MUCH less energy. Of course it is possible! See the comments above.