Re: [CAD_CAM_EDM_DRO] LCDs and UV

Graham Stabler wrote:

>Does anyone know if a standard LCD screen can be used with UV light.
>The idea being that you create a strong UV backlight, then have the
>LCD screen acting as a spatial modulator for this light.
>

No. The rotation angle of light by the crystal is wavelength specific.
Probably LCDs
don't pass ANY UV, anyway, unless you are talking very near UV.

> You then
>image what is seen on the screen on to UV cureable resin, cure the
>image and add a layer and so on and so forth. I'm assuming a small
>screen such as those used in 2.5" monitors and small parts.
>
>Rhino can section parts and a script could create bitmap images I
>should think, I could use the parallax propeller to load these from a
>USB drive and syncronize the lowering of the platform etc.
>
>There is an actual SLA system that does something very like this but
>it uses TI's DLP mems mirror based technology.
>
>
>

Yup, and for very good reason. With a quartz window, the DLPs can go
down to
200 nm or beyond. Also, if you can keep it cool, the DLP can handle a
LOT of
light -- like a 1000 W Xenon arc lamp focussed on a thumbnail. The
trick is the
DLP shines the mirror spots on the target, or on a black beam dump. The LCD
absorbs the light not wanted. Turn the "screen" black, and it has to absorb
the entire 1000 W in the polarizers! Poof!

Jon