Status of current research on digital and analog photography

RobertP said:

Whew.....This reminds me of the experiments of a cloaking device that Einstien was supposingly working on. It was something like using magnetic fields to bend light waves or something along that line. I think it was called " The Philadelphia Experiment" or something like that. Then again maybe it was just a movie i saw.

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There was a movie of that title. I don't know if the movie spawned the rumors or the rumors spawned the movie, but there have been rumors about experiments along those lines. The whole thing has been pretty well debunked. The US Navy has a small Web page on the topic, and there's even a Wikipedia article on the subject. Googling turns up lots more.

srs5694 said:

There was a movie of that title. I don't know if the movie spawned the rumors or the rumors spawned the movie, but there have been rumors about experiments along those lines. The whole thing has been pretty well debunked. The US Navy has a small Web page on the topic, and there's even a Wikipedia article on the subject. Googling turns up lots more.

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This weeks Science News reports on cloaking devices using similar materials with a negative index of refraction.

PE

The original Pendry superlens only worked in the near field, roughly speaking, at a working distance that is of the same order as the free-space wavelength. I haven't followed all the developments since then, but the working versions I saw (for radio and microwaves) and planned optical frequency devices I read about all adhered to this rule.

Hands up all those who take macro images with a sub-micron working distance?

These sorts of superlenses have potential application for chip makers, but not for photographers. It is possible that they will also allow better diffractive elements to be designed and made, but again, the direct applications are in manufacturing and production engineering, not as end-user products.

A regular MW or LW radio has a detector that is substantially smaller than the wavelength of the radiation, so in principle that would work for light too. The big difference is that frequency specificity allows radio aerials to work at fantastically miniscule f numbers.

Radio aerials also aren't expected or required to form a high resolution image of the source. A sub-wavelength sensor is incapable of directionalizing its reception enough to form an image by scanning etc. Silver halide grains, BTW, are sub-wavelength detectors, but they form an image by individually detecting only intensity (and even that mostly in aggregate -- a higher percentage become developable with increased light levels), with spatial mapping of intensity (as modified by filtration and/or sensitivity curves, in the case of color films) forming the image across many-many detectors.

The application of superlens materials for conventional photography, if I've correctly understood what they are and how they work, would be as a thin plate directly in front of the sensor (i.e. emulsion), similar in operation to the film-contact rear element of the Minox Complan lens (which, I might add, was quietly replaced during routine service in almost all the cameras originally so equipped due to film scratching problems). This would be used to increase the effective resolution of an otherwise conventional lens, similarly to the way the silver metal film was used to increase the resolution of an X-ray lithography projection.

The applications I have seen either talk in terms of a phased-array of sub-wavelength detectors, where you recover the directional information from the relative phase of neighbouring pixels; or they use each single sub-wavelength detector behind an individually-angled shadow mask which selects a small incident angle. The idea in both cases is to dispense with the lens altogether, but you could adopt a half-way house if you wished.

For a Pendry lens, both the subject and the detector need to be in the near field. A plane wave from infinity is passed from one side of the slab to the other with no phase lag - which itself suggests interesting uses, but puts you back to figuring a surface if you want to make a lens.

Finally, the suggested and attempted implementations of superlenses for optical frequencies that I have seen all use Pendry's idea of a perforated metal film. Light energy propagates through the film as a localised collective excitation of the metal atoms, their surrounding electrons and the electromagnetic fields in the holes. Nobody expects a simple wavelength dependence.

I would love to be proved wrong, but I still think it unlikely that we will see this type of lens in an image capture device used in the way that digital and analogue cameras currently are.

Struan Gray said:

I would love to be proved wrong, but I still think it unlikely that we will see this type of lens in an image capture device used in the way that digital and analogue cameras currently are.

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If you read the original article, the purpose of these lenses is to focus electromagnetic energy with a small wavelength in order to fabricate finer digital devices such as smaller sized image sensors.

Currently, digital fabrication is limited due to the fact that the 'image' is always larger than the wavelength of electromagnetic energy used to produce it. Therefore, this process will be of great benefit to the digital fabrication process.

PE

Great stuff to share, thanks PE.

don