i am trying to build a light screen in which a bank of 4 ir lasers will be reflected by 90 degree prisms mounted to 3 posts and then back to the transmitter/receiver. the problem im running into is that i need twelve .75 inch prisms in all. all the ones i am finding are around 80$ but that's out of the budget for this project. does anybody know of a source for cheap ones? like the ones I remember taking out of cheap binoculars as a kid
prism
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buds224
Enlightened
If you're not worried about quality and truly are willing to go cheap:
http://www.fasttech.com/products/0/10000293/1033200-creative-high-definition-bed-prism-lazy-glasses
This ad always makes me laugh. Unfortunately, there are no specs on the dimensions of the actual prisms.
http://www.fasttech.com/products/0/10000293/1033200-creative-high-definition-bed-prism-lazy-glasses
This ad always makes me laugh. Unfortunately, there are no specs on the dimensions of the actual prisms.
bshanahan14rulz
Flashlight Enthusiast
Why can't you use mirrors? What wavelength IR?
i guess i could use mirrors. 880nm
bshanahan14rulz
Flashlight Enthusiast
880nm is starting to get on the long side, but I bet a normal mirror would be fine. You might try to find first-surface mirrors, though. Most mirrors like in bathrooms and such are rear-surface, meaning there is glass between the reflecting surface and the image. This can cause things like doubled dots due to partial reflections.
With an optical first-surface mirror, it won't be as efficient at trying to reflect IR, but it's relatively short IR so I can't imagine losses being too terrible.
The hardest part of it all will be aligning everything. I don't know the best way to make adjustable mounts on the cheap, but I'm thinking something like gluing the mirror onto a metal back for support, and gluing the metal back onto a central column, and gluing the column on a base plate, and having screws thread into the base plate that touch the metal mirror support and can be used to "bend" the mirror via the "bendy-ness" of the central column. Not that I've ever built such a thing. Maybe you'll be able to find soemthing better.
With an optical first-surface mirror, it won't be as efficient at trying to reflect IR, but it's relatively short IR so I can't imagine losses being too terrible.
The hardest part of it all will be aligning everything. I don't know the best way to make adjustable mounts on the cheap, but I'm thinking something like gluing the mirror onto a metal back for support, and gluing the metal back onto a central column, and gluing the column on a base plate, and having screws thread into the base plate that touch the metal mirror support and can be used to "bend" the mirror via the "bendy-ness" of the central column. Not that I've ever built such a thing. Maybe you'll be able to find soemthing better.
Steve K
Flashlight Enthusiast
Interesting problem... the alignment issues give me some concern too. You might get around this somewhat by having a large lens to collect the light prior to the detector itself. You'll want to mount the mirrors to something solid and substantial. There will be a need to tweak the mirror rotation in two planes.
Any plans to modulate the laser in order to improve the ability to reject ambient IR?
for reference, there are industrial items of this sort produced. The industry term is "light curtain", usually involving a number of parallel light beams for the purpose of detecting if something crosses a boundary or gets near a machine.
Other thoughts that stray off topic... you could use a rotating laser radar (lidar) to measure the distance to everything nearby and determine if something has moved into the area. Something like the Velodyne LIDAR, perhaps...
http://velodynelidar.com/lidar/lidar.aspx
It's not cheap, but it is cool.
Other thought.. instead of a rotating laser, maybe you could check the distance to nearby objects with a single beam of light that shines up from the ground and hits a conical mirror surface such that it causes the light to propogate horizontally in all directions. Then you just have to detect the delay from the transmission of the light to the reception of the reflections, and you'll know the distance to the nearest object. Piece of cake, eh?
Any plans to modulate the laser in order to improve the ability to reject ambient IR?
for reference, there are industrial items of this sort produced. The industry term is "light curtain", usually involving a number of parallel light beams for the purpose of detecting if something crosses a boundary or gets near a machine.
Other thoughts that stray off topic... you could use a rotating laser radar (lidar) to measure the distance to everything nearby and determine if something has moved into the area. Something like the Velodyne LIDAR, perhaps...
http://velodynelidar.com/lidar/lidar.aspx
It's not cheap, but it is cool.
Other thought.. instead of a rotating laser, maybe you could check the distance to nearby objects with a single beam of light that shines up from the ground and hits a conical mirror surface such that it causes the light to propogate horizontally in all directions. Then you just have to detect the delay from the transmission of the light to the reception of the reflections, and you'll know the distance to the nearest object. Piece of cake, eh?
FRITZHID
Flashlight Enthusiast
Use the flat beam lens out of a laser level, then take the mirrors out of an old junked laser printer scanner head, they are ment for IR
