Learn How to Project an Image on a CRT Monitor with a Small Projector

[smidhunraj]

I wish to build a small projector . how to project an image on my crt monitor on screen.Is it possible.

 

[CWatters]

It might be possible but it's one of those problems that are easier to solve by starting from somewhere else.

For an in focus image to be formed each point on the wall must only receive light from the relevant part of the image. Since a crt screen has a wide viewing angle light from almost any part of the CRT screen can arrive at any point on the wall. Any lens system used to solve this would have to be quite big.

In addition, crt screens aren't very bright. Any image produced ould be very dim compared to a dedicated projector.

 

[davenn]

Hi smidhunraj
welcome to PF :)

in commercial projectors ... that I have repaired many of during a "previous life" there are several type of projection methods. When I was in that work, the 2 main types were ...
1) using 3 LCD panels, one for each primary colour R,G,B a very bright light was shone through each panel ( ~ 3cm x 2cm in size) the 3 colours of light from each panel was then combined in a prism arrangement and then projected out via focussing lenses to the screen
2) DLP --- Digital Light Processing --- DLP used just one panel that the projector light shone through... have a look at this wiki link for background
http://en.wikipedia.org/wiki/Digital_Light_Processing

to go from your CRT monitor to the wall isn't likely to be possible, and the ways as described above would be very difficult to achieve with any reasonable efficiency.

It would be interesting to try a small LCD screen from a portable TV ...say a 5 cm to 7cm sized screen. setting it up in a box with a very bright light source ( you need ~ 700 lumnins and above for a respectable brightness) then having lenses in front of the panel to focus the image on a wall/screen
Something along those lines would be your best bet. you may have to consider inverting colours fed to the LCD panel as otherwise you might get a "negative" colour effect on the screen ... like looking through an old photographic film negative

You would have to strip the LCD screen out of its housing, getting rid of the fluro/other lamp back lighting, sheets of reflectors and diffusers etc so you just had the bare LCD panel and attached electronics

cheers
Dave