Project light visibly on glass to create images?

[AlbertRenshaw]

I'm not sure which category of physics best suits light rays and what not so I just stuck this under general physics, many thanks to anyone who can help me with my problem!

I want to project some words onto glass with a projector... What projector do I need? I was assuming something with lasers but I have no clue what will project onto glass? I also need to to not go through the glass as much as possible but to just hit the glass and stop the laser/light ray right there.
Also, would it be possible to project at an angle onto the glass, like the projector is reall close to one end of the glass and projects almost parallel with the glass so that it will hit the glass int he center and create the text on the glass? This way I can put the projector kind of on the glass and not on the other side of the room? Thanks!

 

[schip666!]

Whatever you use as a screen needs to disperse the light being projected. Think of the difference between nice clean dry air and a smoky room. Glass that's usually used for a projection screen is called "ground" as it has a translucent surface made, originally, by grinding up the surface...like with a piece of sandpaper. You can get plexiglas that has similar properties now as well, or even sand your own clear Plexi. It won't really matter if you use an old Carousel projector or a fancy high powered laser, you still need to disperse the light at the image plane so it hits the user's eyes.

Any time you project "off-axis" like (i think) you are trying to describe, you are going to get distortion of the image, just like parallax or perspective drawings. The more off axis, the more distortion. You can somewhat correct for this by opposite-pre-distorting the projected object or using a special lens system, but YMMV.

 

[sophiecentaur]

If you want to see stuff which appears to be positioned in the middle of a room I suggest that you consider using a 'Pepper's Ghost' type of illusion. It may not be practical but it could give what you want. Pepper's Ghost involves a semi reflecting glass screen placed diagonally on a stage and an illuminated image, off-stage in the wings, will appear in the room / stage set. You need to get the lighting right so you see the image and the background at the right brightness. Google it and you will see many links with diagrams. If it useful for your purpose then that's great. If it's not then it will be worth looking at anyway. It's how a lot of Victorian stage illusions were achieved and also many Head-Up Displays on vehicles and planes.

 

[AlbertRenshaw]

I'd like to keep the current glass I have without damaging my house's value haha! What if I dropped the glass idea all together? Can I project in air? Not literally off the air but if I set up two lasers and had them shine onto each other, would the midpoint where the lasers hit each other light up? Kind of like a cross section? What if I had one laser shine one light wave and the other laser shine the inverted light wave, that way where they hit it will be a duality sort of and give them both something to bounce off of? I don't know, I've never studied this stuff, I have a basic understanding of waves from programming and chemistry... no physics /: