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Spaceplates

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#1 boothg599

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Posted Yesterday, 02:59 AM

What do y'all think about a project using these things? https://www.nature.c...467-021-23358-8

#2 luxo II

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Posted Yesterday, 03:56 AM

That is so packed with buzzwords it was probably writtten by a buzzprose generator.

Anyway that definition of “spaceplate” is satisfied by solid glass - a solid optic could be 30% shorter than one full of air. Only snag is the weight.

Think I’ll file the at one in the round file, along with cold fusion and the mysterious fictitious magical “quantum telescope”
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#3 Gleb1964

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Posted Yesterday, 06:00 AM


 

Anyway that definition of “spaceplate” is satisfied by solid glass - a solid optic could be 30% shorter than one full of air.s magical “quantum telescope”

No, it is opposite to that - solid glass instead of air space would slow beam convergence and take 50% more space.
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#4 MitchAlsup

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Posted Yesterday, 03:51 PM

What kind of Eyepieces will we need to use at F/0.5 primaries ?


Edited by MitchAlsup, Yesterday, 03:51 PM.


#5 jimhoward999

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Posted Yesterday, 09:21 PM

If you put a plate of glass in an optical train it stretches the path by t(n-1)/n where t is the thickness of the plate.  To get compression of the path with a plate you need a negative index of refraction.  

 

Negative index materials have been theorized using "meta-materials"  and demonstrated in the microwave region.  But I don't think negative index meta-materials have ever been created in the optical domain. 

 

The authors of the article present some ideas on "spaceplate" materials they think might work.  I think these are just hypothetical ways to get at an optical meta-material with a negative index....they must be because that is the only way you get compression with a zero-power plate.  I am certainly not smart enough to analyze the presented concepts, which were difficult to follow.  But they seemed pretty fishy.



#6 TOMDEY

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Posted Today, 09:18 AM

It's mumbo-jumbo. Would take a nondispersive index of refraction of a thousand to even begin to get something that has a prayer of slightly working. Complete baloney.    Tom



#7 Gleb1964

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Posted Today, 09:27 AM

If you put a plate of glass in an optical train it stretches the path by t(n-1)/n where t is the thickness of the plate.  To get compression of the path with a plate you need a negative index of refraction.

Yes, that is correct formula.
So, to shrink the space you would need refraction index between 0 and 1. Why are you talking negative index? See in article used "a negative uniaxial birefringent medium", not a negative.



#8 MKV

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Posted Today, 11:05 AM

It's mumbo-jumbo. Would take a nondispersive index of refraction of a thousand to even begin to get something that has a prayer of slightly working. Complete baloney.    Tom

Lol, personally, I'm waiting for deferents and epicycles to enter the stage...it worked the last time they were introduced.  :o)

 

 

So, to shrink the space you would need refraction index between 0 and 1. 

How can a refractive index of a "medium" be less then unity, Gleb? Vacuum refractive index is 1. What's "medium" would it take to have one?

 

But, today, many things are "possible" and "real" if  you can just imagine it. :o)  

 

According to researchgate,

 

https://www.research...this-phenomenon

 

refractive index can not only have a value of less than 1 but it can also be negative! It's sort of like the geometric raytrace result of a paraboloidal mirror on-axis -- the image is a dimensionless dot. Sure. It may even depend on what day of the week it is. :o)

 

popcorn.gif



#9 Gleb1964

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Posted Today, 12:09 PM

How can a refractive index of a "medium" be less then unity, Gleb? Vacuum refractive index is 1. What's "medium" would it take to have one?

 

Mladen

 

Refraction index is related to phase velocity which can by any. If refracting index less then 1, phase velocity is above speed of light. That what is happened within absorption bands, for example. 

 

about phase velocity.jpg



#10 jimhoward999

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Posted Today, 12:58 PM

Yes, that is correct formula.
So, to shrink the space you would need refraction index between 0 and 1. Why are you talking negative index? See in article used "a negative uniaxial birefringent medium", not a negative.

yes you are right....brain fart on my part.  A negative index meta-material would actually increase the space even more than a plate of regular glass. 



#11 jimhoward999

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Posted Today, 01:49 PM

Here is a spaceplate configuration that does work...sort of

Slide2.JPG

 

You put a beamsplitter coating on both sides of a plate parallel plate and let the light bounce back and forth.  Of course the throughput with 4 bounces is only 1.5% and the remaining 98% of the light lives in horrible ghost images, but it still probably works as well as the hypothetical electro-optical devices in the paper.

 

You could also tilt the surfaces at 45° to regain the throughput

 

Slide3.JPG

 

oh look I've invented the Porro prism.

 

The point is there are conventional ways to shorten an optical system if you are willing to add components.



#12 MKV

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Posted Today, 06:37 PM

Refraction index is related to phase velocity which can by any. If refracting index less then 1, phase velocity is above speed of light. That what is happened within absorption bands, for example. 

I guess it all depends how how one defines it mathematically. When I was in school, refrective index = n/n'. All my optical programs still treat it that way.  




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