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Holo effect?

RedCowboy

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I am waiting for some beam expanders I have ordered to arrive and was just testing spot size at 50 - 70 feet, the good old 7875 is still a solid diode and looks like about a 10 x 50mm bar at 50 feet so with a 10x expander it should focus to a 1 x 5mm bar in theory ?

Anyway I can see the spot on a leaf and my laser is securely clamped down, but when looking through binoculars it looks as if the lasers spot/bar is floating out in the air a foot ahead of the leaf, no there's no spider web or branch, I walked out and checked that the spot is on the leaf very slowly making a brown rectangle on the leaf, but through the binoculars it has a holographic effect.

I know this is to do with the mechanics of light and lenses but this holographic type effect is inspiring to see first hand.

ALWAYS PROTECT YOUR EYES, IF YOU ARE NOT SURE IT'S SAFE THEN WEAR YOUR LASER SAFETY GLASSES THAT ATTENUATE THE WAVELENGTH YOU ARE WORKING WITH.
 
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ElectricPlasma

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I am waiting for some beam expanders I have ordered to arrive and was just testing spot size at 50 - 70 feet, the good old 7875 is still a solid diode and looks like about a 10 x 50mm bar at 50 feet so with a 10x expander it should focus to a 1 x 5mm bar in theory ?

Anyway I can see the spot on a leaf and my laser is securely clamped down, but when looking through binoculars it looks as if the lasers spot/bar is floating out in the air a foot ahead of the leaf, no there's no spider web or branch, I walked out and checked that the spot is on the leaf very slowly making a brown rectangle on the leaf, but through the binoculars it has a holographic effect.

I know this is to do with the mechanics of light and lenses but this holographic type effect is inspiring to see first hand.

ALWAYS PROTECT YOUR EYES, IF YOU ARE NOT SURE IT'S SAFE THEN WEAR YOUR LASER SAFETY GLASSES THAT ATTENUATE THE WAVELENGTH YOU ARE WORKING WITH.
Try zooming in with a phone/camera, my bet's on the binoculars causing the effect. It could be two things within the binoculars, the image combination between your eyes or the optics overlap in each barrel (or both). Binoculars (depending on the quality) use various prisms and two main lenses, those two being the objective lens and the ocular lens (eyepiece). You may not have the correct focus from the binoculars to the leaf, also possibly bypassing the light's focus point and overlapping in the optics. Maybe, maybe not. Managed to get any pictures of it?
 

RedCowboy

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I tried closing one eye and adjusting the binoculars parallax but it still did it, it may be the binoculars lens, they are cheap ones, I have better pairs, I should switch binoculars and see if I still get it.

I'm trying to adjust my cylindrical pair so I can use the 10x expander I have coming, but if the exit lens is 36mm and the beam in is more than 3.6mm them I may have an issue, I may have to go down to 4x pairs to use the 10x expander so the input line width won't cause clipping.

I think the 3X from podo should work, I have one of those on the way as well.
Right now my corrected beam is 4.0 - 5.5mm wide depending on how I set my G2 and my pair, I went back with podo's G2 and got a 75 foot bar that looks like what a 7875 with a 3 element focused is. That's not bad for a nubm44. Also with a real G2 I can run converging to 7 feet then diverging again from there, that will play in some to helping the expander work I hope with a input beam diameter slightly greater than 1/10 the exit lens diameter. These expanders do not use a relay lens as far as I know.

If I can get it into that 10x without much clipping I will be in business....I wonder if I clip 20% if the expander will soak it up, should be metal lens rings, it's a Jet Lasers 10x.
 
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paul1598419

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This effect is cause by the difference in wavelengths of light and the refractive properties of the binocular lenses. I've seen it through my glasses as I have pretty severe myopia and with different wavelengths the colors are staggered in space.
 

RedCowboy

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That makes sense, I have seen before with cheap rifle scopes that you can get a RGB triple image if not focused in at the distance just right, that's why expensive optical systems, telephoto camera zoom lenses, projection televisions, ect... have all those seemingly extra lenses.

It's also why so much more power is needed to get more lumens out of a projector, to compensate for parasitic lens losses that are necessary for a decent image quality under variable adjustments.
 
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paul1598419

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That's right. Much of the optics in higher priced optical equipment is to compensate for the chromatic aberrations of the lenses. If you use the binoculars to look at a blue and red laser at the same time, you might see this "holographic" effect to a more pronounced degree.
 




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