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"Smart glass" iris could bring greater quality and flexibility to smartphone cameras

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June 19, 2014

A 'smart glass' iris may provide much greater image quality in future smartphones

A 'smart glass' iris may provide much greater image quality in future smartphones

In a conventional camera lens, the iris consists of a set of overlapping mechanical blades that control the amount of light entering the camera. As efficient as this mechanical system is, it is too bulky and too difficult to miniaturize to be incorporated in smartphones and other compact mobile devices. To address this, a team of researchers has used "smart glass" to create a micro-sized electronic iris that may bring much greater image quality and flexibility to smartphone cameras.

The researchers, from Germany's University of Kaiserslautern, created their non-mechanical iris using an electrochromic material like that used in the View Dynamic Glass windows. In this case, the material consists of various polymer layers that turn opaque when a small electrical voltage is applied. Each of these layers is configured as concentric rings to provide varying degrees of aperture to simulate the behavior of a mechanical iris, with each of the two segments able to be controlled to produce four possible switching states. In effect, this provides a range of f-stops similar to that found in a mechanical iris lens.

"There is currently no technological solution available that meets all the demands of integrated iris apertures in smartphones," said lead author of the research Tobias Deutschmann. "Many of the proposed devices require the motion of a strong absorbing material to block the path of light. Electrochromic materials, as used in this study, remain stationary whilst they change their absorption, so there is no need for any actuation. This allows for much smaller casings to fit around the devices and thus enables the integration into tiny camera systems ... this is the decisive hardware parameter which determines the success of next-generation models in the smart phone business."

In addition, the team claims that each of the segments does not need a constant current applied to remain opaque, so power consumption is predicted to be very low (claimed to be approximately 30 μW); a feature that bodes well for future use in portable devices. And, according to the designers, by being able to precisely tune each segment in proportion to the voltage applied, the light transmitted through the iris is evenly distributed and tightly focused, thereby ensuring that images remain sharp and clear.

The only real drawback of using electrochromic material in the studies so far is that of reaction time – according to the researchers this is still in the region of seconds – which will need to be addressed before the "smart-glass" iris could be released as a commercial product. However, the researchers state that they also hope to decrease the switching time by eventually incorporating new electrochromic materials currently being developed.

Source: Journal of Optics

About the Author
Colin Jeffrey Colin discovered technology at an early age, pulling apart clocks, radios, and the family TV. Despite his father's remonstrations that he never put anything back together, Colin went on to become an electronics engineer. Later he decided to get a degree in anthropology, and used that to do all manner of interesting things masquerading as work. Even later he took up sculpting, moved to the coast, and never learned to surf.   All articles by Colin Jeffrey
4 Comments

The description talks of concentric rings and then calls them segments with four switching states, so I have no idea how this works in detail. I guess that some marriage of this technology with the sensor chip so that the f stop setting can be altered across the image will be possible, which would be better than simply copying the way an iris works.

Mel Tisdale
20th June, 2014 @ 03:18 am PDT

Iris serves TWO purposes not 1. One is as describes above, control the amount of light passing through the lens. But the second, which IMHO is more critical is to reduce the "circle of confusion" - translated read "depth of field". This second aspect needs study of optics in conventional photography sense which 99.999 % of smartphone snap-shooters would not understand.

pmshah
20th June, 2014 @ 08:49 pm PDT

@pmshah, you are quite right. However, with the small focal length lenses in smartphones, DOF control is not the same issue (or potential creative tool) as in "real" cameras. I suspect, too, that any significant stopping down could introduce diffraction problems.

My 'phone has Google "lens blur", artificial DOF simulation. I believe that has much more potential as an artistic tool, and a possible threat to large-sensor DSLRs. I look forward to phone/cameras with two lenses/sensors, designed specifically to exploit that concept.

Bottom line: I also don't think the electronic iris will be that big a deal.

splatman
22nd June, 2014 @ 01:55 am PDT

When this becomes fast, it may allow apertures and shutters to return to being in the middle of the lens. I think they may have some competition from LCD shutter technology, which is already very fast, but has had trouble with the transmissivity of the clear state. I've read that it's up to 95% now.

John Banister
29th June, 2014 @ 01:44 am PDT
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