directional diffuser

[sm_jamieson]

I have fitted a rigid sunpipe (300mm) in the roof of my extension to brighten a dark corner, which it is doing, but the diffuser that fits on the end of the tube is multi-directional - as you'd expect from a diffuser. The diffuser is polycarbonate with random angled facets to spread the light in all directions. Now, a diffuser is needed to protect the eyes when the sun is reflected directly in the tube (and to seal the bottom of the tube), but I'd like something that sends all the light in one broad direction, i.e. towards a 45 degree sector of the sphere, so no light is being sent back towards the windows and being "wasted". Anyone come across such a thing, such as on some fancy light fitting ? I could seal the end of the tube and have some mirror type arrangement below, but that would be inefficient and look ugly. Cheers, Simon.

[Andrew Gabriel]

Probably want some sort of fresnel panel (a sort of tiny portion from the edge of an imaginary giant fresel lense). I was a bit surprised a quick Google search tuned up nothing, but a harder search might do.

[NT]

The light that's come down the tube is exiting the tube at an assortment of angles. One simple way is to put some reflective sheet inside the interior diffuser such that the light all goes to one side of the diffuser. More exact control gets more complex, a fresnel lens won't do it because the light's multidirectional.

NT

[John Rumm]

The things designed to help high backed vehicles reverse that stick on the rear window might do the trick.

[sm_jamieson]

What you really need is a diffuser as I described before, but with all the little facets pointing in the same direction. I could just put a piece of tubing that extends beyond the bottom on one side. Trouble is, that would only catch shallow angle light. Simon.