# laser pointer hard to see on tv screen



## lv6l (Feb 8, 2007)

i have a class and the professor uses a laser to point onto a very large computer screen mounted in the wall. its one of those projection screen but the screen i believe is glass and the projector is being projected from somewhere behind the wall not on a ceiling like most projector. overall i believe its just the bright light through glass that is causing the laser to be unseeable. when she points it on walls its ok but once it hits the screen its very hard to see. to make a long story short i want to know is there a laser out there that can cure the problem because its hard for the myself and the rest of the class to see and i'm turning to CPF to help me out here. thanks for any inputs.


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## iemand (Feb 8, 2007)

probably the screen is just plain glass and the laser is just going through it?


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## stevetexas (Feb 8, 2007)

What is the output of the pointer. Some <5 mw (aka 1-2 mW) pointers will do what you describe. Try pointing the laser at the screen when it is off to see if it is a property of the screen reflectivity or of the fact that the TV light is brighter than her laser. Earn some brownie points and mod her laser... :laughing:


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## lv6l (Feb 8, 2007)

i think all you guys could be right. i dont know which laser she has. i'm guessing its not so much of a high end laser just a basic one that she picks up at office depot or staples. i dont know much about laser to mod together one for her. if i know how or you guys show me links i will give it a try or show me links to which one to buy.


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## stevetexas (Feb 8, 2007)

can you see the laser on the screen when it is off?


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## lv6l (Feb 8, 2007)

she never tried that before so i dont know. but i think with it off it'll still be kind of hard to see. the brightness compare to a regular wall is a big difference. when she shines it on the screen it's like shining it through glass, sometime she'll hit somthing dark or black picture on the screen, that helps and is a bit easier to see but compare to a regular wall its still very hard. what seems to be the problem here?


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## ted_park (Feb 8, 2007)

I think that most screens are designed to reflect as little light as possible, so that contrast is good if there's lots of ambient light.


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## soapy (Feb 8, 2007)

A lot of the light will go right through, and not reflect back. Also, the mirror smooth front surface ensures most of the beam gets sent off as a neat reflection, rather than scattered like a bit of wall would do. And it is a very bright surface, too.

Worst of all aspects, really. It's like trying to see it on a mirror from an off angle. Even a ten times power boost will only make it a tiny amount brighter since most of the power is not going where you want it. And anyone hit by the direct reflection might have issues.


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## k00zk0 (Feb 8, 2007)

What I've noticed is that green is very hard to see with lots of ambient light. A cheap red pointer can be seen easier than the green dot from a 10mW modded laser I had, when pointed on bright lit up sidewalk outside. If it is a glass screen then theres not much you can do, but if its a white sheet with the projector behind it, try using a cheap red pointer; much more visable.

The comment about the screens being non-reflective.. If the screen didnt reflect or refract the light at all, it would be invisable to both the eye and the projector light, wether it comes from the front or back. As in the light form the projector would also go right through.


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## allthatwhichis (Feb 8, 2007)

They are still made to reflect as "little" light as possible. I bet if they could, TV screens would "be" invisible, we're just no there yet.

Also, you may want to be careful with the reflection you are getting. Watch where it's going in your audience... :candle:


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## PhotonWrangler (Feb 8, 2007)

It sounds like she needs a plain old mechanical pointer for use with that screen. Increasing the laser power would only increase the danger of catching high-power glints off of reflective surfaces.


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## lv6l (Feb 8, 2007)

thanks for all the inputs guys. lots of new info i learn. i guess i'll just in the mean time try to see whatever i can.


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## k00zk0 (Feb 9, 2007)

allthatwhichis said:


> They are still made to reflect as "little" light as possible. I bet if they could, TV screens would "be" invisible, we're just no there yet.




If the projector screen didnt reflect light, you wouldn't see projected image at all!


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## allthatwhichis (Feb 9, 2007)

:huh2: You know what I mean... :touche: The glass type...  The fabric or painted on the wall "screen" types are white or the reflective silver/white which HAS to reflect everything, or approximatly everything back...


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