Artificial Sunlight (official topic)

My current setup is using a 150W 5600K Luminus LED, with 95 CRI. The LED outputs about 12,500 lumens.

I just picked up another Luminus LED that’s twice the power and lumens output (280W, 25,000 lumens) and I’m looking forward to trying that. I have a much larger dish sitting in my garage, and I’m thinking of getting a Luminus CVM-45 to test with it—that model goes up to 600W and 57,000 lumens, and is available for around $145 USD here in Canada.

One idea I mulled around but never pursued—sunlight makes your skin feel warm, which LEDs don’t do. I was considering whether I could simulate this with an additional infrared LED placed next to the primary LED, but haven’t pursued the idea. I’m not really sure if it would be safe? It’s been a while since I looked into it but I remember getting the impression that it might risk eye damage. I’m curious if anyone else has had this idea, or if anyone has any thoughts on it?

Where are we at on getting to a solution for an artificial sunlight that can be hang from a wall instead of requiring a large volume to set lights up? Is that even physically feasible?

Also, instead of using a 6000k light and a blue film to filter out and spread the blue light, would it be possible to use a 5000k light directly and simulate the bounced blue light with a secondary blue fill light? That’s more of a lighting solution than a physically accurate one, but it might simplify the final product.

Thoughts?

@moment  I doubt you'd get something hanging on a wall. Artificial sun beams need a lot of space in a DIY set up. I think a combination of two routes is best to nail down artificial daylight in a room. One being something like this: https://lightglasslighting.com which on further digging is very similar to the DIY Perks smashed tvs video. Use this as a fill, then combine it with this for soft beams:

I have this set up in my north facing office currently on its own, and it's ok, but not amazing. The shadows are verrrrry blue, and the light is a bit too yellow, which is quite a depressing experience imo. But I think balanced out with a good white daylight panel, it might feel nicer.

@moment Saying that, what you're looking for has been done, it's just really expensive to produce according to this guy after reaching out to him.

Posted by: @bigfield

↑

@moment  I doubt you'd get something hanging on a wall. Artificial sun beams need a lot of space in a DIY set up.

I agree that we’re unlikely to get anything small enough to fit on a wall. But I’m convinced that a large, shelf-top sun light is possible using similar techniques to rear-projection flatscreen TVs. I haven’t yet put the time and money into investigating in depth, but if you look at rear-projection TVs from right before the industry transitioned to LCD, they can be quite shallow for their size.This 42-inch TV for example has a diagonal width of 107cm, but the depth is only 30cm! At its most basic, this is accomplished with a fresnel lens at panel, an angled mirror in the back, and a projector lens at the bottom. It may be that the optics of the most “modern” rear-projection TVs are more complicated, but I haven’t seen anything to confirm that and haven’t yet gotten around to finding one and dismantling it.

Posted by: @timdmackey

↑

At its most basic, this is accomplished with a fresnel lens at panel, an angled mirror in the back, and a projector lens at the bottom.

Here are some different optical schematics for rear-projection TVs. As you can see, some of them use multiple mirrors, while the shallowest appears to use just one mirror.

Hello folks, I've been looking at the Coelux patent and it appears they use a compound parabolic concentrator (CPC) to generate the virtual sun. @DIY Perk, was your first project able to mimic the sun in such a way that it looked like the ones from Coelux etc., or was it actually just the linear light effect?

Posted by: @hans23

↑

Hello folks, I've been looking at the Coelux patent and it appears they use a compound parabolic concentrator (CPC) to generate the virtual sun. @DIY Perk, was your first project able to mimic the sun in such a way that it looked like the ones from Coelux etc., or was it actually just the linear light effect?

-- attachment is not available --

 

I thought about this concept before myself. Funny that that it is patented. Anyway i saw multiple problems with this setup which is why i did not further pursue it.

1. If the observer stands near to the sunlamp and has direct sight onto the emitting light source he will obviously see the light source but also the reflections of the parabolic mirrors on both sides thus giving the impression of multiple suns.

Now one could say alright. We only need to make the parabolic mirrors flat enough such that at an appropriate distance one will only see the emitting light source if one does not see the reflection from the parabolic mirrors and the reflection on one of the sides if one does not see the reflection on the other side or the light source directly. While this is true this leads to following impression then:

2. If the parabolic mirrors are rather flat and/or the observer stands far away from the sunlamp the observer will see that there are multiple disjoint light spots such that if he walks past the sunlamp he will see the first sun illusion, then nothing, then the second sun illusion which corresponds to direct line of sight to the light source, then again nothing and then the last sun illusion.

So we should not make the mirror flat to avoid 1. either. But one of those problems must occur as far as i understand it. Either these regions of reflections or whatever one wants to call them overlap, then we see multiple suns or they are disjoint. It will only be perfect at one fixed distance it seems to me. Furthermore one more note on 1. We also actually want theta_max to be rather small right? But as it get smaller the distance at which 1. does not happen will also grow.

This is why i discarded this setup but if i am missing something i would be glad to be corrected.

1. @purple did you end up buying the sheets from 1688?

@nolo any news on your projekt?

 Here's my crack at this project. I'm actually pretty happy with how it looks. It's a Nanlite LED + Fresnel shining up at a ceiling-mounted mirror covered with waterproof transparency sheets. The diffusion could be a bit bluer, but overall not bad! Thanks to all the folks in this thread for the inspiration!

Let me know if anyone wants the BOM.

Hello again,
I got some pictures of a system that works pretty well. As they haven´t made that system puplic yet, I can´t show it here. But I think some of you guys could help with finding the principle. I don´t know if it is possible to make a private Discord group or something like that to get a faster way to respond to each other! Because I thin if we could make a group call or something, we could fasten up the process! I also orderer a panel that produces a artifical skylight and would like to share it with youu as soon it is here! Just let me know.

And again the question, does the parabolic mirror and that one LED allready creates that Sun and Sky effect and we are just trying to make it smaller, or is it only for the parallel light?

@hans23 ooo what did you order? Would love to see what you've made too