HI,
I am an embedded electronics systems designer ...(I would like to beleive that)... and am not clear with optics
For one of the projects that we are dealing with we need to illuminate the suface.
Let us consider illuminating an 8 inch square or 200mmx200mm sqaure plate with as few sources as possible.
I tried using the principle used by LED back-lit LCDs but could not find the specialised gratings or prisms... What I learnt from being with my dad(well he is into the lighting industry..) is that acrylic and frosted glass can also be used as diffusers and light pipes(I understand that they are both different uses of the material.)
I tried to use the same. The resulting effects are promising but not quite what I intended.
I have chosen a 5mm thick, 200mmx200mm mirrored glass plate with the uncoated side, sand blasted.
When I place a high brightness LED (I shall try posting pics and the LED part number tomorrow) on the centre of the thin edge of the plate a triangular illumination pattern is observed. It is similar to an equilateral triangle (3 inch side or 75mm)with the one of the triangle vertices being at the contact point of the LED. Though this is interesting, it is nowhere close to what I need. I require total surface illumination. I tried the same with a one side frosted acrylic. But the results in glass were better. The Glass used is float glass with a relative index of 1.54
My Senior keeps telling me that I need to look into diffraction gratings and such. But I dont know if that would help or even if it did where and whom do I approach.
Please help me learn more about total internal reflection to enable me to design this surface illuminator.
I have a few questions:
1. When The light is passed through one of the thin sides of the plate such that the direction of the beam is parallel to the flat surface, Why does the light not get to illuminate the flat surface if the surface is not frosted (is the light still escaping through the surface or is it getting reflected internally). Help me explain the phenomenon to my senior. (I think that internal reflection takes place and hence we cannot see the point source)
2. Will it help if I have the other three thin sides mirrored?
3. Will it help if both the flat surfaces are mirrored and then one of the sides is frosted to also partially remove the mirror coating?
4. Is there a better way to achieve the results than tinkering with frostings. Do I really need to go ahead and search for gratings.
5. Help me calculate (guide me) the surface illumination intensity, given the relative index of material, intensity of source, surface area of illumination. Or please tell me what else I need to consider. Or is there a better way to go about it.
6. Would increasing the relative index help?
regards,
Vishal...
Light Pipe Based Surface Illumination
Re: Light Pipe Based Surface Illumination
