Researchers create focus-free camera with new flat lens
phys.org
phys.org
So how does it break the laws of physics? Well it doesn't; it cheats by not preserving the phase of the light. In a normal lens, the phase of the light is preserved. Light that must travel further to reach the point of focus travels faster as it passes through less lens material (where it travels slower than the speed of light).
The lens is also made on a flat disc a little bit like a Fresnel lens. The difference with this lens is that it doesn't have a single point of focus, instead light is focused onto many planes, simultaneously with equal power of light focused onto each plane. In this paper the planes were chosen to be between 5 and 1200mm. A clever computer algorithm calculates the exact shape of the lens to get this distribution given a specific wavelength of light.
The end result is a lens which has amazing depth of field but the trade off of only operating well at a single frequency and poor efficiency. Most of the incoming light is being focused on a plane that the sensor isn't on. Indeed at 1200mm it has an equivalent f-number of 555 requiring some insanely bright lighting and long exposure time to get a good image.
I can't see many real world applications of this camera given the downsides but in a world of more computational photography this could be one part of a better imaging system.
This is very interesting indeed, but at an equivalent f/555 I don't see many practical applications for this either. For context, usual photography uses apertures from f/1.2 to f/11, with lower numbers letting being a larger aperture and thus more light in. It'd require a massive amount of light to get a usable image.
Maybe the images could be sharper with this lens, or have very good macro? As you stop down (increase the aperture number) images become sharper up to a point where the diffraction limit steps in and quality degrades; usually this happens at f/9 to f/11 (which is why I mentioned f/11 as the lower range of commonly used apertures; although almost all lenses can go smaller, for pixel-peeping quality you'd want to use an ND filter and f/11 aperture).
[edit: Wait, Wikipedia lists Horowitz and Andreesen as founders of Lytro? I thought they were just investors?]
How does this compare to a pinhole camera, which (ideally) has perfect depth of field and focuses all incoming light onto the plane of the sensor, but which achieves that at the cost of admitting very little incoming light? (Thus requiring insanely bright lighting and long exposures.)
It seems like the exact same tradeoff.
I'm don't think that's why the lens has such a high f-number at large focal lengths. Rather, it's simply because they only manufactured a very small (1.8mm diameter) lens. Given the exotic shape and manufacturing of the lens I'm not surprised it's so small, and I suspect scaling this to larger lenses would be a very serious barrier to practicality. It's also not clear why they chose that particular focal range, so there may be some other issues I didn't notice. But on the whole this is very interesting work!
The fundamental observation (not caring about the phase of light at the focal plane) that makes this work is more interesting to me tbh. The authors' previous work uses a similar technique to produce a thin, single element apochromatic lens -- something that normally takes 3 thick lenses and expensive glass formulations.
The paper: https://www.osapublishing.org/optica/viewmedia.cfm?uri=optic...
I've only skimmed it, but it looks super interesting.
I was expecting some kind of computational holography wizardry, but no, it's just a multilayer diffractive lens with circular symmetry which produces a beam with a really stretched-out waist.
Usually diffractive lenses are limited to a single wavelength — they're using 850 nm. Is there a way something like this can work over the whole visible spectrum? If not, this might be more like a lightsaber than a camera.
Not sure if they already have a full-spectrum version working though.
Up until a few years ago I would have said 'No way. The software isn't there yet, and it'd be prohibitive from a cost/processing power standpoint in mobile form factor.' But... see previous comment on iPhone 11 Pro.
Is this the type of tech the Lytro camera was based on? I thought that was an interesting concept. Imagine you'd be able to do something similar with this type of lens.
There are no statements regarding transmissivity, which leads me to believe that its actually lower than a typical lens wide open i.e. the incident irradiance (light on the sensor) is equivalent to a regular lens set to a narrow aperture. There is no free lunch in optics or physics usually.
Could the same glasses serve both as reading glasses and as long-distance glasses?
Low-level visual processing in our retinas and brains seems to be too specialized to learn new tricks.
No idea about deconvolution, but I doubt computers can do better job identifying things from blurry images than brains.
"Because the disalignments are often much smaller than the diameter and spacing of retinal receptors, vernier acuity requires neural processing and "pooling" to detect it."
I'm not under the impression that we could easily train the brain to follow some different, very specific, synthetic algorithm.
Worms use their brain to identify and manipulate objects, to taste objects if those objects are identified as food, and to sense aspects of their environment including temperature and humidity. Bees use their brains to see, to fly, to communicate directions, and to coordinate various behaviors with other bees. There is very little plasticity in these simple organisms: a bee that can't communicate will not find a different way to do so, it will simply die.
As animals get more complex we can see that plasticity becomes more important. A bird needs more complex processing to be able to adapt its hunting strategies for different environments. If environmental changes force a bird to move to a new habitat, we can hypothesize that they are smart enough to adapt their hunting strategies to the new habitat.
The evolution of humans has involved many factors that would favor this kind of plasticity: roaming over diverse landscapes, predator spotting, group hunting, tool use, language, and social communities. The resulting large cerebral cortex that we have from these evolutionary trends also gives us the ability to re-wire sensory pathways in the way you pointed out. But when I say "brain" I think of much more than just the cerebral cortex.
What I can't see evidence for is any notion that the brain was less flexible then became more flexible over time. Would it be incorrect to assert that it essentially began flexible, as a result of the appearance of nervous systems, and that's its primary property? Of course complexity increased with time. But did the flexibility also increase?
Similar to how a signal transduction process mediates between molecular receptors on cell membrane and cell behaviors, the neural complex mediates between stimuli and response at the level of the organism.
But at the same time I can see why you are thinking about flexibility as some sort of "primary property" because they seem to be inherently flexible in some way. I'm locating _plasticity_ more narrowly to the cortex part of the animal brain, but perhaps the cortex is just an amplification of some simpler lower-level flexibility. At this point my knowledge of the subject falls short.
Edit: thank you for the interesting discussion, you have sparked me to dig more deeply into these topics!
https://www.theguardian.com/education/2012/nov/12/improbable...
If all objects are at or beyond the hyperfocal distance, one can focus the lens to infinity and be done with it. All objects will remain in focus regardless of the size of the aperture as all rays incident on the lens from a given object are quasi-parallel.
EDIT: Quasi-parallel from the object, not quasi-parallel to the optic axis.
It depends on the focal length, the chosen aperture, and to some extent on the resolution of the camera.
What I want to say is, if these new lenses transmit light at a high rate (let's say 1:2.8) while being hyperfocal from 0 mm to infinity all the time, you could take pictures at night more easily without having to focus or stop down to get larger scenes fully in focus.
Thus being actually useful in traditional photography.
Landscape photography could be another application.
For example http://www.infinityoptics.com.sg/who-we-are/
Not sure if this is a bit too directly commercial for HN, asking re: optics not the whole solution.
Assuming a celllphone-ish sensor in terms of scale and cost (assuming lenses are free) how well can one do in theory? Particularly for iris?
How feasible is it to have iris scanners we don't need to shove our faces into?
Joking aside, I wouldn't doubt this creeping into the film industry or other professional photography. Everything already goes through so much post processing, color correction, etc etc.
I wouldn't call myself anything serious as a photographer; OTOH some serious photographers whom I follow start turning more into 3D artists or videographers.
Photography as a profession seems to be in a crisis: not that it's not needed, it's that many adjacent things (3D, video, design, marketing) are also needed, not unlike in programming: there's almost no such thing as a senior (e.g.) Python developer, there are senior Web, Data, etc. developers which primarily use Python along with other tools (JS, sql, etc).
Amateur astrophotography is a good example of where software is utilized to fill in gaps in the hardware all of the time. Color correction and focus stacking are often done in software, star tracking mounts are using software, and so on.
But yes, the best photographers are generally trained to spot exactly the right framing and composition from the moment the moment the photo is snapped.
Remember when "personal" computers weren't fashionable among "serious" programmers? Or GUIs, or scripting languages, or the web?
Whenever the choice is "software that's only 80% as good" or "more expensive hardware", the former will win every time.
Hardly. It's namely portraiture that benefits from thin DoF, or similar applications where figure/ground relationship can be improved by keeping OOF elements blurry.
There are a great variety of situations where you do want as much in focus as possible. Landscape and macro photography are the most notable examples, where most high-level images utilize focus-stacking composites to simulate extreme DoF.
Certainly focus depth is a creative tool, but don't confuse expensive wide-aperture lenses for what is necessarily good.
And yes, it's a electrically tunable lens are a thing. Optotune is one company I've heard of making hardware for the industrial space, there are probably others.
Phone cameras are already twice as good as they need to be.
Visual impairments is pretty broad, and this approach is using collimated light so not general purpose - but things in this direction could plausibly have applications in the area.
Bokeh is the effect of blurring out the background. Its important because it lets you isolated the subject, like a human face, from the background.
Still, if it does one thing better than other lenses, it will be useful.
In that case, we truly woulnd't miss it.
Depth of field is incredibly important for managing a viewers focus. Imagine a picture of a coffee in a coffeeshop with the background out of focus - you can clearly see a coffee cup. That same photo but with everything in focus will be much more confusing - what should I be looking at, it's too busy, etc.
Bokeh is the effect of blurring out the background.
In other words, bokeh is fundamentally an aesthetic characteristic.
here's an extremely in depth look at what that means.
It explains what people mean by "soft bokeh" (~= bokehlicious!), apodized lenses, and the "cat's eye" shit you find sometimes.