The "lightbox" is the light source of the vidéoprojecteur.
I've choosen to use a HQI lamp (mercury vapor). Benefits are a very white light (movies will end with a perfect color), and it's a ponctual light source, perfect to align the focal of all the optical elements. Plus, this lamp has a life expectancy of 10.000 hours, way more than the ones from the market's VPs ; and when it dies, it costs only a few dozen bucks to replace.
Drawbacks : it heats as hell! So you have to make sure its support will handle the high temperature, and a sufficient fresh air flow.
Cutting the support in 1.5mm thick sheet metal... Top of the picture, the reflector that will come behind the lamp.
Folding the sheet...
Assembling the lightbox : lamp supports are made out of ceramic, and one of them is mounted loose to handle the lamp dilatation due to the temperature.
This is the most critical step of the construction : hacking the LCD screen. Do it in a quiet place, marking each plug, do never force on 'em... I used a Hyundaï L50s 17" that I got for a fair price. The benefit of a 17" screen is its 1024x768 resolution : not only I'll be able to watch movies, but also surf the internet, play video games, etc... Balancing drawback : the box will be large, therefore bulky... It's a matter of choices!
Unpacking the brand new screen, I plug it to check it works fine. No problems here, not even a dead pixel.
Removed the back part...
Dismantling goes on... I put a mark on each plug to make sure I'll be able to plug them back later at the right place.
And voila!
The LCD panel is naked, and plugged back "in the air" to check it is still working... Ooof, it does work!
You then have to manipulate the panel with extreme care, it's only a very fragile 2mm thick glass panel...
I wanted to make such a project when I discovered the excellent site allinbox.com.
After several months defining the ideal configuration, I do 3D plans of my future video projector, to verify that my focal point calculations are coherent with the box size...
hérents avec la taille de l'engin...
On the left, the lightbox (light source), followed with a borosilicate glass to limit the heat transmission toward the rest of the bow.
Then come F1 and F2, two Fresnel lenses to straighten up the light rays so they pass right through the LCD screen which is between. The resulting image goes trough a variable focal objective, and then finally is reflected to the screen by an optical mirror...