- Joined
- Dec 18, 2013
- Messages
- 5,178
I have an interesting problem I need help with. I have an Opto Reflector that I need to detect the presence of a metal surface 50mm away. Circuit works fine, but if I put certain transparent objects in its path as a cover to protect it from dust it reflects of it.
Now you might think this is obvious but one of them is optical glass and the other is an IR acrylic lens. The IR material is rated to pass the 950nm IR.The glass should start attenuating at around 3 microns, the IR device transmits at 0.95 microns. The surface of the glass is very smooth and the surface of the IR lens has a roughish texture. Now this is the weird thing.
If I take an A4 protective wallet, you know the ones you put paperwork in to protect it which have an almost frosted look. I don't get a problem. If I take a component draw plastic insert, shiny on one side frosty on the other I again don't get a problem on either side shiny or frosted.
What do you think is happening? Total scattering (Lambertian diffuser) or the thickness of the material causing in phase reflection at that wavelength of light. This can happen if the material thickness is a multiple of the wavelength of the light. Or do you think it might just be the surface finishes of the material itself?
Thanks
Adam
Now you might think this is obvious but one of them is optical glass and the other is an IR acrylic lens. The IR material is rated to pass the 950nm IR.The glass should start attenuating at around 3 microns, the IR device transmits at 0.95 microns. The surface of the glass is very smooth and the surface of the IR lens has a roughish texture. Now this is the weird thing.
If I take an A4 protective wallet, you know the ones you put paperwork in to protect it which have an almost frosted look. I don't get a problem. If I take a component draw plastic insert, shiny on one side frosty on the other I again don't get a problem on either side shiny or frosted.
What do you think is happening? Total scattering (Lambertian diffuser) or the thickness of the material causing in phase reflection at that wavelength of light. This can happen if the material thickness is a multiple of the wavelength of the light. Or do you think it might just be the surface finishes of the material itself?
Thanks
Adam