I am not quite sure what you mean, but I will have a go at an answer.
For rear projection, the optics are designed to focus the image on the screen the same as a front projection, except reversed of course. Light is transmitted through the screen, diffused a bit so it can be viewed from a certain range of angles. Early on I experimented a little bit with trying to make pure diffusion based RP screens, just using some stretched thin light grey shopping bag plastic glued to a more rigid piece of clear plastic. It worked all right, but it is not a patch on a professional screen.
The pro screens are made up of either one or two layers. The single layer screens are 'lenticular' and are made up of heaps of tiny cylindrical lenses designed to diverge the light over a particular viewing angle. The brightness of the screen when you are sitting directly in front of it is specified by a gain factor, either 1.0, 1.5, 2.5 etc. The higher the gain, the less wide angle the screen can be used at. The two layer screens also have a huge fresnel lens attached as well.
They also use very fancy dyes in the plastic of the screen to try and optimise the contrast etc.
These screens are very expensive to buy new I think. I happened to get one very cheap from a manufacturer that was moving factory. I have also heard that you can sometimes get them from repair places, with minor scratches etc. on them.
For rear projection, the optics are designed to focus the image on the screen the same as a front projection, except reversed of course. Light is transmitted through the screen, diffused a bit so it can be viewed from a certain range of angles. Early on I experimented a little bit with trying to make pure diffusion based RP screens, just using some stretched thin light grey shopping bag plastic glued to a more rigid piece of clear plastic. It worked all right, but it is not a patch on a professional screen.
The pro screens are made up of either one or two layers. The single layer screens are 'lenticular' and are made up of heaps of tiny cylindrical lenses designed to diverge the light over a particular viewing angle. The brightness of the screen when you are sitting directly in front of it is specified by a gain factor, either 1.0, 1.5, 2.5 etc. The higher the gain, the less wide angle the screen can be used at. The two layer screens also have a huge fresnel lens attached as well.
They also use very fancy dyes in the plastic of the screen to try and optimise the contrast etc.
These screens are very expensive to buy new I think. I happened to get one very cheap from a manufacturer that was moving factory. I have also heard that you can sometimes get them from repair places, with minor scratches etc. on them.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.