See-through Overhead LCD

jdusablon · 02-13-2005, 03:15 AM

Got a hold of an lcd for use with overhead projectors in schools/University. When the fresnil lens is removed, it works great. My plan is to use it like a sun visor. Any one have any experience with these devices?

egeekial · 02-13-2005, 03:22 AM

I have no idea what you're talking about... do you have any pictures/links/whatnot?

Vchat20 · 02-13-2005, 03:28 AM

we had something close to this a while back. my algebra teacher had this for use with the TI graphing calculators.

egeekial, basically its an lcd screen, but its see through rather than opaque.

egeekial · 02-13-2005, 03:30 AM

Ohhh... I see. Yeah, a bunch of my teachers have had those TI projector thingies.

Don 944 LA · 02-13-2005, 02:11 PM

good for also making a homemade projector maybe...
why pay $2000 for video projector

Vchat20 · 02-13-2005, 10:14 PM

yeah. that'd be nice. good 80" high def flatscreen

mushin · 02-13-2005, 11:53 PM

Quote: Originally Posted by Vchat20

egeekial, basically its an lcd screen, but its see through rather than opaque.

All LCD screens are like that

.

I've seen at least one guy on the web who took the LCD from a laptop with a broken backlight and attached it on top of a property-dispo overhead projector, to make a dirt cheap LCD projector. Looked noisy, but definately slick.

NiN^_^NiN · 02-14-2005, 12:31 AM

Mushin is right

All LCD screens are made like this.

The white that your seeing is the back part of the LCD to direct the Light evenly through the LCD it also a reflection type material depending on the LCD

People have used these for cheap Home video projectors but the problems with thoese projectors is they are usually 640 x 480 res with 256 Colours

There are better one's but most people don't like the way it looks when projected as most of the old displays had bad refress rates.

I'm not sure how you could use this in the car tho....

jdusablon · 02-15-2005, 03:49 PM

I have in mind to use the thing like a sunvisor. I think it would be interesting to be able to flip the unit down and select songs while still being able to see the road. I don't know how safe this would be, but testing for this would obviously be done while stationary. Like an HUD (heads up display) for planes, etc.

My reason for using it? (or trying to...) It is just lying around and works. Also, it runs on 12V dc already. I thought for sure someone would have tried this!

The only problem with this scenario is using it at night, since there is no backlight.

hotponyshoes · 02-16-2005, 04:37 PM

what about putting it on top of the dash flat down with the backlight attached into the cars head lights. this should then reflect on the windshield just like a jet fighter?

VanMan69 · 02-16-2005, 04:47 PM

Quote: Originally Posted by mushin

All LCD screens are like that

.

I've seen at least one guy on the web who took the LCD from a laptop with a broken backlight and attached it on top of a property-dispo overhead projector, to make a dirt cheap LCD projector. Looked noisy, but definately slick.

Yeah, I did that with an old 15" LCD. Hard to work with since the controller and all that is connected by very short ribbon cables, which are configured for the controller to be behind the display, instead of next to it, and the bare LCD and the electronics around the edges are very fragile. It worked okay, but the screen had some lines on it, probably damage from disassembly and handling of the components/small ribbons.

wi77iam · 02-16-2005, 06:30 PM

Quote: Originally Posted by NiN^_^NiN

Mushin is right

All LCD screens are made like this.

....

Well not quite. There are 3 types of LCDs - transmissive, reflective and transflective as explained here.

The one you're talking about here is the transmissive type - normally used in laptops, Lilliputs, etc.

turbocad6 · 02-16-2005, 07:11 PM

I have played around with & built a heads up display off of the windshield & I can tell you from experience that during the day it is USELESS & at night it is way to bright while still being hard to read if you can picture that. a heads up dislay isn't good for multi color high resolution images. all hud's you will see are monochrome & simple, a high resolution hud isn't practical. I even played around with different films on the windshield & put alot of effort into this, only to realize that it just doesn't work.....no matter how you configure it you would be better of just looking at a lcd directly, seeing through it sucks.......I've done it & it sucks, there, I admitted it

mushin · 02-17-2005, 12:53 AM

Quote: Originally Posted by wi77iam

Well not quite. There are 3 types of LCDs - transmissive, reflective and transflective as explained here.

The one you're talking about here is the transmissive type - normally used in laptops, Lilliputs, etc.

You're talking about the material behind the liquid crystal panel. The panel itself is translucent in all cases. The 3 types of LCDs differ in how backlight is provided: an active light behind the LCD (transmissive), a mirror that reflects ambient light back through the LCD (reflective), or a combination thereof (transflective). Because liquid crystal is absorptive, not emissive, they fundamentally work by passing light through them.

mushin · 02-17-2005, 01:03 AM

Quote: Originally Posted by turbocad6

I have played around with & built a heads up display off of the windshield & I can tell you from experience that during the day it is USELESS & at night it is way to bright while still being hard to read if you can picture that. a heads up dislay isn't good for multi color high resolution images. all hud's you will see are monochrome & simple, a high resolution hud isn't practical. I even played around with different films on the windshield & put alot of effort into this, only to realize that it just doesn't work.....no matter how you configure it you would be better of just looking at a lcd directly, seeing through it sucks.......I've done it & it sucks, there, I admitted it

Yeah, blasted freakin' bright sun

. However, I think what the original poster is proposing is a little different than most HUDs; rather than reflecting the image off the windshield, he's talking about looking at the LCD directly, with the sky as the backlight. This *might* actually work, since in theory at least it sounds like it should be more efficient at utilizing the ambient light than a reflective LCD. Of course, to make it work at night then, you'd need to rig up some side-lighting LEDs and a diffuser or something.