Perfect colors, captured with one ultra-thin lens

http://www.seas.harvard.edu/news/2015/02/perfect-colors-captured-with-one-ultra-thin-lens

by porsupah • 11 years ago

108 39 11 years ago

seas.harvard.edu

altcognito• 11 years ago

Better images out of cell phones and SLRs, or is that not a logical application of this technology?

striking• 11 years ago

It's not just that the images will be better, it's that the sensors can get smaller. The silly bump that represents the camera on the iPhone6/Plus wouldn't be there if this existed. Google Glass could be far cheaper. Smaller SLRs, even! And everything will have far better quality than before. Truly revolutionary.

KeytarHero• 11 years ago

Do you mean lenses can get smaller, or is there some way this means the sensors can be smaller too?

olla2• 11 years ago

Id rather say that this means the sensors can get bigger for compact cameras and phones. Currently the only thing that limits us making pocketable full frame cameras with zoomable optics is the size of optics, not the size of sensor or other electrical components. Flat optics might make full frame camera phones even possible.

Houshalter• 11 years ago

We may also have super tiny lens free cameras that avoid these issues entirely: www.technologyreview.com/news/525731/lens-free-camera-sees-things-differently/

lutorm2• 11 years ago

Part of the bump must be there because you need a finite focal length system, and that won't change even if the lens itself is flat.

higherpurpose• 11 years ago

Actually, the bump on the iPhone 6 shouldn't be there now. There are phones that are just as slim and with just as big if not bigger sensors, and are perfectly flat. The problem is Apple decided not to change the sensor this year, and used an pretty old one, which hasn't gotten anymore compact, even though the phone's body has.

Watch Apple introduce a 13 or 16MP camera this year that has no bump. Why? Because this time it will actually use a cutting edge sensor, rather than a 3 year old one.

sp3323• 11 years ago

Sure, but also telescopes could be a lot smaller. The article mentions microscopes too.

semaphoreP• 11 years ago

This should only apply to refracting telescopes, and not reflecting telescopes I think.

qzw• 11 years ago

Forget cameras, I want the bionic eyes we were promised. I hope this gets us a step closer.

ljoshua• 11 years ago

I'd imagine (without knowing anything about it) that it would also have applications in fiber optics as well?

sp3323• 11 years ago

"Light shining on it bends instantaneously, rather than gradually, while passing through." I don't think light bends gradually going through a normal lens. It bends at the surface.

kenbellows2• 11 years ago

I don't think that makes sense; otherwise, why would the thickness of the lens matter at all?

vilhelm_s• 11 years ago

The shape of the lens puts the surface of the lens at the correct angle. You can make a thin lens by splitting it into many discontinuous parts, this is how a Fresnel lens works. See e.g. these two pictures:

http://upload.wikimedia.org/wikipedia/commons/9/97/Lens3b.sv... http://en.wikipedia.org/wiki/File:Fresnel_lens.svg

tomswartz073• 11 years ago

OP above is correct. The light will only bend at the interfaces between two mediums (air, glass).

sp3323• 11 years ago

It doesn't. Light can bend when it encounters a change in the index of refraction, e.g. air to glass or vice-versa. https://en.wikipedia.org/wiki/Refraction#Explanation Light travels in a straight line after it has entered the glass, and again after it exits. Only the angle and the difference in refractive index matters. That's why you can build a Fresnel lens which is, so to speak, all surface. https://en.wikipedia.org/wiki/Fresnel_lens#Description

acjohnson554• 11 years ago

They were being a bit imprecise with the terms. The important part is that refractive index is dependent on wavelength and so you get dispersion, which increases with the distance between surfaces. But in a regular lens, the distance is necessary in order to achieve overall deflection of the light beam's initial angle, which results in focusing. A flat piece of glass deflects light internally, but upon exiting, ever beam is parallel to how it entered, resulting in no focusing.

Being able to directly deflect at a flat, thin plane eliminates the need to consider dispersion. Well, as long as you can deflect all wavelengths at the same angle. They talk about demonstrating 3 wavelengths and seeking to extend this to more.

blt• 11 years ago

If this actually works, it's got to be one of the biggest technology advances of the past 20 years.

I'm guessing there's a catch, but I would love to be wrong.

simcop2387• 11 years ago

My guess on a catch would be that it'll focus ONLY the wavelengths that you select for. the others might be diffused or given wildly different focal points. This might mean that for certain types of photography you're limited in what you pick up (e.g. if you've lit a scene with mono-chromatic light that's not one of the selected wavelengths).

acjohnson554• 11 years ago

They did say in the article that they hope to produce devices that work for a range of wavelengths. This would be great because 3 wavelengths would not be sufficient for capturing natural images. We can approximate the cone responses of natural images with 3 wavelengths, which is why RGB encoding and display works for displaying images to humans. But in capture, you want to receive broad spectrum light at the detector, and then encode it to RGB.

djKianoosh• 11 years ago

so, no chromatic aberration. no lens flare either?

tomswartz073• 11 years ago

There's a link to another article at the bottom of this one that hints at other possible uses. http://www.seas.harvard.edu/news/2014/05/collaborative-metas...

What's really interesting about this is that the metasurface lenses might be very useful in other high-precision optics: for example, densely packed multicolor DVDs?

Perhaps even optical imaging of very, very small materials without the need for electron microscopy. Who knows?

Dylan168072• 11 years ago

Optical discs are generally using the smallest light they can manage, can colors even help?

Plus they're focusing on a single point, so I don't think chromatic aberration would be much of a problem in the first place.

If they can play fancy tricks to get a smaller focal point relative to wavelength, that would be a powerful improvement. But still probably monochrome discs.

MrLeap• 11 years ago

This reminds me of an explanation I read a long time ago for why FM radio is so much clearer than AM. This doesn't really approach your question of informational density, but I thought it was interesting.

If you're driving down the road and someone is shining two lights through the trees. One is white light and merely changes brightness, while the other rotates through three colors. Which light is easier for you to detect changing?

tomswartz073• 11 years ago

It could be something akin to holography.

To put it simply, they can have the same optical density, but re-write over it several times in other colors. The same lens can observe and read the exact point, interpreting the data in (for example) blue, green, and red.

soylentcola• 11 years ago

I admit that I'm biased toward personal interests and hobbies but my first thought was an Oculus Rift that fits more like a pair of shades than a pair of ski goggles.

And of course the ever-present dream of "smart" contact lenses that can adjust how incoming light is magnified on an adaptive basis or offer AR functionality without any headgear at all.

Obviously that sort of application is years away regardless of how this particular project works out. Still, this stuff does lead to some fun brainstorms and geeky fantasies.

_paulc• 11 years ago

This looks somewhat like the concept behind a fresnel zone plate [1] - in general these are highly dispersive (only work at one frequency) so it looks like they have done something to address this. Many (30+) years ago my final year project at university was trying to dynamically synthesise lenses using by electronically manipulating the phase response across a liquid crystal substrate - technology wasn't really there at the time but always thought that it would have been an interesting avenue to follow up on.

[1] http://en.wikipedia.org/wiki/Zone_plate

argimenes• 11 years ago

It sounds like an Apple marketer devised the article's title ... ;-)

chinpokomon• 11 years ago

The key part is that it has different refraction for specific wavelengths. This implies that you will still need filters to restrict the light to those wavelengths or you will still have chromatic aberration. Projecting light through such a lens wouldn't have quite the same problem as the source light could already be tuned.

In short, good for projection, but maybe still bad for capture.

Perfect colors, captured with one ultra-thin lens

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