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As part of a DIY electronics project, I want to use LEDs to create a glowing effect with a crystal ball.

I found a perfectly clear crystal ball that looks exactly like this:

enter image description here

I tried combining it with an appropriately sized ring-shaped set of LEDs. The LED ring is big enough for the bottom of the ball to fit in it but not big enough for the ball to pass through it. The LEDs are controlled by an Arduino and can change color, intensity, etc. They look like this:

enter image description here

I was hoping to achieve a luminescent effect, i.e. I wanted the ball to glow. A little extra light shining off of the LEDs is fine, it doesn't have to be perfect. However, in my attempts thus far it seems like the light from the LED kind of lights up the surface / sides of the ball, but it doesn't look like the ball is glowing from within. Just the opposite. It looks like the ball is dark and there's a halo around it.

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    You may not be able to do that. You can create a stand to enclose around the lights right to the globe so that no light can reflect off the outside. However, a perfectly clear globe won't diffuse any of the light entering so that it radiates out all around and looks like a glow. It will act like a lens. Light from the LEDs will pass through and out the opposite side, probably with a little refraction, so it will look a different size on the top. You could try putting a curved diffuser between the globe and stand to scatter the light in all directions entering the globe.
    – fixer1234 ♦
    Aug 19, 2021 at 23:08
  • @fixer1234 Those are good points. A diffuser of some sort could work and I could also buy a cloudy ball instead of a crystal-clear one.
    – Hack-R
    Aug 19, 2021 at 23:43
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    @fixer1234 That sounds like a perfectly good answer (even though the outcome is uncertain)!
    – Joachim ♦
    Aug 20, 2021 at 4:31

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To get that glowing effect, light needs to radiate out in all directions. A perfectly clear ball won't diffuse any of the light entering it. It will act like a lens. Light from the LEDs will pass through and out the opposite side, probably with some refraction, so the LED pattern will look a different size on the top.

You could eliminate the bothersome reflections off the outside by putting the LED ring in a stand that encloses the lights right to the globe.

One idea that might produce the glow effect would be to put a curved diffuser between the globe and stand to scatter the light in all directions entering the globe. If that works, it would let you use the clear globe.

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  • +1 but I don't think your last paragraph will help, unless viewing from a position where the diffuser is what you see looking through the ball. Imagine a diffuser under the ball in that top picture - you wouldn't see it from the camera's position. A diffuse ball would work much better. The exception could be in a very dark room, where internally reflected light would dominate over the image of the background
    – Chris H
    Sep 2, 2021 at 14:19
  • @ChrisH, you wouldn't see the diffuser. The idea would be that the diffuser would scatter light from the LED ring in all directions so the light would exit the ball everywhere. But to be noticeable, it would probably need to be in a darkened room with no competing scenery visible through it. I originally posted it as a comment because I wasn't sure how effective it would be.
    – fixer1234 ♦
    Sep 2, 2021 at 17:51
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    exactly - without line of sight to it, it can't be much use. The light would exit the ball at all points, but only at angles that (including refraction) allowed sight of the diffuser. A test could be mocked up using a glass bowl full of water, with a torch underneath, and paper for a diffuser; a perfect sphere isn't all that special
    – Chris H
    Sep 2, 2021 at 17:54

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