[npunt]

Seems like this idea could scale very well with more LEDs of lower wattage, like a local dimming array in TVs. That way

1. heat would be more evenly distributed reducing the need for large heatsinks

2. smaller fresnel lenses could be positioned much closer to the light reducing thickness

3. with a lot of LEDs there'd be a less noticeable grid at the edges of each fresnel lens from chromatic aberration.

I'd totally buy a 'sunlight window' product like this.

[crazygringo]

Do they make "directional" or "angled" Fresnel lenses?

Because you also really want the light to come out of the vertical window at something like a 45° angle downwards.

The physics of it should be fine, I've just never heard of them being manufactured.

And then just add a translucent blue diffusing layer on top.

It seems highly commercializable.

[skykooler]

I suppose you could buy a big Fresnel lens and then cut out a square near the side, and only use that; it would focus the light but also change the angle.

[corty]

There are flat sheets of prisms, that do what you need there. You probably know them from pictures you had as a child that change what they display depending on the angle you are looking under.