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ArcticMyst Security by Avery

Project Question.

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Wade

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I posted over in the Tutorials, Help & Repairs... and got no responses.... so I was going to post here and see if you guys can help, it is mostly an optics question.

Still looking at using multiple LDs but I don't want to culminate them now.  I want a wide bright beam.  Would I be best to use 2 lens to get a solid beam or use a diffuser on each diode and then combine the diffused beams into a solid one?

If I want to use the 2 lens option, has anyone tried a concave mirror?  If the mirror is uniform, and the diodes set in a ring, then they should all reflect into a single point in front of the mirror.  I should then be able to get by just using a single diffusing lens to produce the beam? (image below)

This should create a closed circuit and trap the light, correct?
 

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Jimmymcjimthejim

Jimmymcjimthejim

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Your picture will not work. I really don't want to go into details here, but here's my interpretation on what will happen.
Again, I'm not 100% sure that this is what will happen, but only what I think.
diode_array_001.jpg
 
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Wade

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Ok, thanks, that is a start. Do I need to add a culminating lens first and the diffusing lens?
 
Jimmymcjimthejim

Jimmymcjimthejim

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Here's what you can do, and has been done by a few members before. I think you've got the idea, just take a look at this picture.
diode_array_001-1.jpg

Since concave lenses are not as available, it is recommended to use convex.
 
Morgan

Morgan

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Hi Wade and Jimmy,

Could this idea be condensed by looking at a similar setup to a reflecting telescope? Forgive any naivety but doesn't it do the same thing? Gather a large amount of light and focus it?

Morgan

(I have now updated my gender to the one I was born! Male! Didn't see that icon!)
 
Jimmymcjimthejim

Jimmymcjimthejim

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Morgan said:
Hi Wade and Jimmy,

Could this idea be condensed by looking at a similar setup to a reflecting telescope? Forgive any naivety but doesn't it do the same thing? Gather a large amount of light and focus it?

Morgan

(I have now updated my gender to the one I was born! Male! Didn't see that icon!)
Click to expand...
It could be possible, but what I can tell you is that it won't be nearly as portable as using one of the methods above. Doesn't hurt to try ;)
 
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Wade

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Ok, I have seen the double lens before. The issue is that I need to get a closed system, I want to get the light to go down and come back without being a danger to the diodes. That is why I was looking at the concave mirror to reflect and culminate. Has anyone used a concave mirror for anything?
 
Switch

Switch

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Wade said:
Ok, I have seen the double lens before.  The issue is that I need to get a closed system, I want to get the light to go down and come back without being a danger to the diodes.  That is why I was looking at the concave mirror to reflect and culminate.  Has anyone used a concave mirror for anything?
Click to expand...

I don't get it...You don't want to have an exiting beam? :-/ Theoretically , the mirror could replace the first concave lens.If you would have a hole where the flat mirror is , then you'd have an exiting beam (an big ugly beam that would actually be lots of parallel beams).If you have a flat mirror there, and it's alligned corectly (perpendicular to the beam) then the light is going to go back into the diodes.If everything is alligned perfectly your diodes will blow. :-/
 
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Wade

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You are correct, the application I am looking for requires a closed system... no exit beam.  So if I understand you correctly feeding the wide beam back through the diffusing lens is going to result in the original 5 beams and they should reflect back and blow the diodes.  The logic is there, but I tend to think reality may have a slightly different result.  I expect that the wide beam going back through the diffuser should get expanded again and then be reflected back off the concave lens... the result should be harmless to the diodes and be pretty close to just ambient light.


Just a theory... Can't seem to find all the parts I need to actually test it.  Any idea where to pick up a small concave mirror or even some of the flexible mirror stuff like in a fun house so I can test degrees of concavity?
 
Hemlock_Mike

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What do you mean by culminuate ?? I've seen that here but I don't know what it means. I use beam expanders to focus a beam to a point. A beam expander works like a telescope.

Mike
 
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Wade

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Culminate:  To bring to the point of greatest intensity or to completion.

Though I'm not looking to bring the beams to a single narrow beam, not anymore anyway.  They have to be culminated at a point to get the diffusing lens to produce the correct result, I want a wide beam about an inch or inch and half.
 
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steve001

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I thought he wanted to collimate too, but I see he wants a finite conjugation.
 
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Wade

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Well on a good note I checked with a contact of acquaintance and I will be able to borrow some supplies to do the testing I need. I should be able to post results (and maybe pictures) by the weekend or early next week.
 
Switch

Switch

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Wade said:
You are correct, the application I am looking for requires a closed system... no exit beam.  So if I understand you correctly feeding the wide beam back through the diffusing lens is going to result in the original 5 beams and they should reflect back and blow the diodes.  The logic is there, but I tend to think reality may have a slightly different result.  I expect that the wide beam going back through the diffuser should get expanded again and then be reflected back off the concave lens... the result should be harmless to the diodes and be pretty close to just ambient light.


Just a theory... Can't seem to find all the parts I need to actually test it.  Any idea where to pick up a small concave mirror or even some of the flexible mirror stuff like in a fun house so I can test degrees of concavity?
Click to expand...

You are forgeting that the wide beam is actually more beams.The beams are collimated before the concave mirror, then they are spreaded by the mirror, then they are collimated again by the big concave lens, reflected back into the lens, spreaded out by the lens, collimated by the concave mirror and straight back into the diodes, collimated like they left.Now taking divergence into account the beams are gonna be a little wider when they return, but if your system is small enough and divergence is low enough the diodes are still gonna get overloaded.

Also I would like to clear some terms: when you say diffuser do you mean the concave lens? because when I hear diffuser I think of something translucid like frosted glass that just spreads light in all directions. :-/
And collimation != culmination. Collimation is bringing the beam to the lowest divergence possible.The word is derived from "column", as in bringing the fascicle of light into a column. :p
 
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Wade

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Sorry for the grammatical errors... I am still new to the scene. For the testing I am planning on using a concave mirror and one or two bi-convex lens. I hope that is clear enough now. I follow what you are saying about the spreading and reflecting. I have some cheap laser pointers around to do the testing (3 of them), so if I blow them no loss. Thanks for the info again and I hope to have a real test answer soon.
 
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