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A few questions about unusual lenses ???

Accutronitis

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I have two lenses that have some unusual properties to them and I'm curious about what these unusual properties do.

The first is a double concave lens but one side is curved more than the other, What does this do ?

And the other is a doublet lens with two lenses glued together, Why ? And the lens surface in the middle is curved more than both of the outside surfaces, What does that do ?

 
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steve001

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Speak with someone at Edmund Optics. Take a look at the site too. Much information you will find. They it will be helpful. I've not seen a bi-concave lens like you describe. I would imagine it spreads light out faster than a lens with equally curved surfaces. The other I've seen and you will find it there.
 

vortish

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I agree with steve. Look at edumond optics, mellis , or thor they can help you
 

Alaskan

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The concave lens will have a negative focal length, used for expanding the light through it, one side more negative than the other, but both adding together for a total amount. The lenses glued together are likely achromatic, helping to keep different visible wavelengths in focus together, otherwise you get noticeable blurring of colors which are extremely noticeable at the edges of objects much like you can see when the light from a prism spreads the wavelengths out, but in very small amounts. On the lens on the right, I believe that is a bi-concave lens, both sides curved in, correct?

I have a lot of questions about optics I need answered myself.
 
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Accutronitis

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The concave lens will have a negative focal length, used for expanding the light through it, one side more negative than the other, but both adding together for a total amount. The lenses glued together are likely achromatic, helping to keep different visible wavelengths in focus together, otherwise you get noticeable blurring of colors which are extremely noticeable at the edges of objects much like you can see when the light from a prism spreads the wavelengths out, but in very small amounts. On the lens on the right, I believe that is a bi-concave lens, both sides curved in, correct?

I have a lot of questions about optics I need answered myself.
Yes both sides are curved in but one side is much more than the other.

The lens on the right being achromatic makes total sense because it came out of a camera lens !
 

WizardG

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Doublets like that will work fine at the output end of a beam expander but can be ruined by a tightly collimated beam. The glue holding the individual lenses together can handle only so much optical power.
 

Accutronitis

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Doublets like that will work fine at the output end of a beam expander but can be ruined by a tightly collimated beam. The glue holding the individual lenses together can handle only so much optical power.
Thanks for the warning !

I finally found some info about the bi-concave lenses like mine which is a asymmetrical bi-concave lens "Biconcave asymmetrical lenses are used to minimized spherical aberration".....

And the convex lens has what's call a "meniscus" lens glued to a convex lens....

It's always a good day when you learn something new !
 
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Alaskan

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The reason for two pieces of glass glued together, instead of one can be for different reasons, I still expect one reason was to make achromatic.
 

Accutronitis

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The reason for two pieces of glass glued together, instead of one can be for different reasons, I still expect one reason was to make achromatic.
I'm sure your right about that, From what I have read so far that is the main reason they are made.....
 




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