Flat lens - is this the breakthrough it seems to be?

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meanwhile
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Flat lens - is this the breakthrough it seems to be?
11 months ago

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

https://www.seas.harvard.edu/news/2012/08/flat-lens-offers-perfect-image

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Barrie Davis
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Re: Flat lens - is this the breakthrough it seems to be?
In reply to meanwhile, 11 months ago

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

https://www.seas.harvard.edu/news/2012/08/flat-lens-offers-perfect-image

For one wavelength only.

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meanwhile
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Re: Flat lens - is this the breakthrough it seems to be?
In reply to Barrie Davis, 11 months ago

What does "one wavelength" translate to in terms of the elements of a photograph?

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Sammy Yousef
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Re: Flat lens - is this the breakthrough it seems to be?
In reply to meanwhile, 11 months ago

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

https://www.seas.harvard.edu/news/2012/08/flat-lens-offers-perfect-image

First you really can't beat physics. What you can do is understand it better and use it differently to come up with a newer and better technology.

Secondly this is not a consumer imaging breakthrough (certainly not yet). It has to be tuned per wavelength. That to me implies chromatic abberation would either be horrible or the effect would potentially make it unusable for a multi-wavelength image...I don't know enough about it to know whether it can eventually be used in a consumer camera.

Thirdly all this sounds suspiciously like a "nano" version of a fresnel lens with a very very large number of microscopic ridges. However the mechanism for delaying/bending light may be different. On a Fresnel lens you compromise sharpness.

http://en.wikipedia.org/wiki/Fresnel_lens#Imaging

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Lee Jay
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Re: Flat lens - is this the breakthrough it seems to be?
In reply to meanwhile, 11 months ago

meanwhile wrote:

What does "one wavelength" translate to in terms of the elements of a photograph?

It works just like any other lens, provided your scene is illuminated with monochromatic light (LASER light, high pressure sodium, etc.).  If not, it's CA city.

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Lee Jay
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Lee Jay
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In reply to meanwhile, 11 months ago

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

Even if this lens worked perfectly for all wavelengths, it would only save length, not diameter.  You can't get around needing aperture.  Saving length would be nice, of course, but it's not the only dimension that matters.

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Lee Jay
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meanwhile
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Re: Flat lens - is this the breakthrough it seems to be?
In reply to Sammy Yousef, 11 months ago

"First you really can't beat physics"

Yeah, I know, was only kidding. Physics always wins.

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meanwhile
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Re: Flat lens - is this the breakthrough it seems to be?
In reply to Sammy Yousef, 11 months ago

"Thirdly all this sounds suspiciously like a "nano" version of a fresnel lens with a very very large number of microscopic ridges. However the mechanism for delaying/bending light may be different. On a Fresnel lens you compromise sharpness."

It does sound very similar, doesn't it. Perhaps sharpness wouldn't be effected given they are working at the "nano" level. Be interesting to see where it heads in the years (decades?) to come.

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alanr0
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As noted previously
In reply to meanwhile, 11 months ago

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

https://www.seas.harvard.edu/news/2012/08/flat-lens-offers-perfect-image

As discussed previously, physics still applies, and the technology is not quite ready for mainstream photographic applications.  As far as I can tell, the lens described is around 42 mm focal length, but only 1 mm diameter (so f:42).  As others have stated, it only works for a narrow band of wavelengths, and the silicon substrate will be opaque to visible light.

They have simulation results suggesting the technique can be applied to high numerical aperture microscope objectives.  However, it may be difficult to maintain low aberrations and high diffraction efficiency over a sufficiently wide field of view for more general purpose photography.

Cheers.

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meanwhile
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Re: As noted previously
In reply to alanr0, 11 months ago

Thank you Alan! Your technically detailed yet understandable descriptions and comparisons (often not an easy task) are wonderful.

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jayrandomer
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The key quote
In reply to alanr0, 11 months ago

alanr0 wrote:

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

https://www.seas.harvard.edu/news/2012/08/flat-lens-offers-perfect-image

As discussed previously, physics still applies, and the technology is not quite ready for mainstream photographic applications. As far as I can tell, the lens described is around 42 mm focal length, but only 1 mm diameter (so f:42). As others have stated, it only works for a narrow band of wavelengths, and the silicon substrate will be opaque to visible light.

They have simulation results suggesting the technique can be applied to high numerical aperture microscope objectives. However, it may be difficult to maintain low aberrations and high diffraction efficiency over a sufficiently wide field of view for more general purpose photography.

Cheers.

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Alan Robinson

“Our flat lens opens up a new type of technology,” says principal investigatorFederico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS. “We’re presenting a new way of making lenses. Instead of creating phase delays as light propagates through the thickness of the material, you can create an instantaneous phase shift right at the surface of the lens. It’s extremely exciting.”

That's the interesting part of the work.  As mentioned above its applicability to photography isn't immediate or technically feasible yet, in large part because the phase delay mechanism (little metal resonators) is extremely wavelength dependent.  The intended application (at the end of communication fibers) is much less demanding than imaging, though, so it's a very neat solution.

I think the real issue with optical wavelengths isn't the substrate (I'm sure glass or sapphire wafers could be substituted with some work) but rather the fabrication--visible wavelengths probably require pattern sizes smaller than what they can reliable generate.  The article mentions scaling from the near-infrared to the Terahertz, suggesting visible wavelengths are probably (at least for now) out of reach.

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photoreddi
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In reply to Lee Jay, 11 months ago

ljfinger wrote:

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

Even if this lens worked perfectly for all wavelengths, it would only save length, not diameter. You can't get around needing aperture. Saving length would be nice, of course, but it's not the only dimension that matters.

Saving length would be more than nice. Assuming the unlikely, that it worked perfectly for all wavelengths, a 200mm f/2 or a 400mm f/2.8 with flat lens elements might have the same very wide front elements, but the glass itself might weigh mere grams, not kilograms, and could be shot hand held all day long.

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tko
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ya can't trust those scientists
In reply to meanwhile, 11 months ago

They tell you about the cool stuff, but not about the bad. Yes, it seems like a nano-fresnel lens good for one frequency.

Their talk about fish-eye effect is pure nonsense. The fish comes from projected a wide image plane onto a flat rectangular area. It's a map making problem, not something physics can overcome.

In 1976 they had flat holographic lenses. Have you seen one in your camera recently?

http://www.sciencedirect.com/science/article/pii/0030401876903527

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meanwhile
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Re: ya can't trust those scientists
In reply to tko, 11 months ago

I asked one of the researchers about the comparison to Fresnel lenses and he disagreed, with explanations as to why. Waiting to hear back whether it's OK to post that reply here.

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CFynn
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Re: Flat lens - is this the breakthrough it seems to be?
In reply to meanwhile, 11 months ago

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

https://www.seas.harvard.edu/news/2012/08/flat-lens-offers-perfect-image

"focuses telecom wavelengths without distortion" - sounds to me like the application of this is fibre-optics, not photography.

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photoreddi
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Re: ya can't trust those scientists
In reply to meanwhile, 11 months ago

meanwhile wrote:

I asked one of the researchers about the comparison to Fresnel lenses and he disagreed, with explanations as to why. Waiting to hear back whether it's OK to post that reply here.

If you look at an illustration of a section of a fresnel lens you'll see that it basically doesn't change any properties of a lens, it just produces a much lighter lens by removing glass from the interior. I'd guess that the greater number of edges would increase the severity of edge effects, reducing image quality, but the lens would weigh a lot less if the lenses being replaced were large and thick.

Fresnel lenses were originally designed for lighthouses to efficiently focus the lighthouse's beams, where image quality wasn't as concern.

http://en.wiktionary.org/wiki/Fresnel_lens

Lighthouse fresnel lens at Point Arena Lighthouse Museum

A Fresnel lens (pronounced /freɪˈnɛl/ fray-NEL or /ˈfrɛznəl/ FREZ-nel) is a type of compact lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses.[1]

The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. A Fresnel lens can capture more oblique light from a light source, thus allowing the light from a lighthouse equipped with one to be visible over greater distances.

http://en.wikipedia.org/wiki/Fresnel_lens

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