A new wide-angle lens for video surveillance
If you're a photographer, chances are high that you bought one day a wide-angle lens, commonly called a 'fisheye' lens. And if you're like me, you might have used it to take a dozen of pictures before putting definitively the lens into a drawer because of the excessive visual distortions. But now, South Korean researchers have designed and built a new kind of optical lens that collects light from a large area and produces a virtually distortion-free wide-angle image. This inexpensive lens -- you can buy it online for $105 per unit -- could be used to improve indoor security systems or as a robot navigational aid.
Wide-angle lenses exist for a long time and offer -- for a limited time -- images that you can find 'funny' because of their distortions. But they are almost useless when used in surveillance cameras. There are other commercial lenses, called 'rectilinear' lenses, which can produce images without too much distortion, but these models have a limited field of view (FOV) -- typically less than 120 degrees -- and are very expensive, costing more than $1,000.
According to the recent Optical Society of America news release, the South Korean researchers, led by Gyeong-il Kweon from Honam University, have developed a lens which is better and cheaper.
An elegant piece of optics technology, the new lens looks like a snow globe in the shape of the U.S. Capitol dome. Light from a large area enters the dome of the lens and encounters a v-shaped mirror. This reflective lens then redirects the light rays to a second lens that resembles the slender statue atop the Capitol dome. This "refractive" lens produces a sharp image of the large area at the exact location of the image sensor within the bullet camera.
Below is a photo of this new wide-angle catadioptric lens (Credit: Gyeong-il Kweon, Honam University). And here is a link to a larger version, thanks to Newswise.
Here are some more details about this lens.
This new design delivers straightforward, practical wide-angle images, producing a "field of view" (FOV) of 151 degrees. The FOV from this technology can be increased to 160 degrees by adding a little more complexity, Kweon says. [...] By comparison, the human eye has a field of view of approximately 46 degrees.
Below is an example of the picture you could obtain with this lens. This is a wide-angle image of a university bookstore, as captured by the new lens (Credit: Gyeong-il Kweon, Honam University). And here is a link to a larger version, thanks to Newswise.
And how much will cost these lenses? Surprisingly, you can buy them today, from a company named Nanophotonics Co., Ltd. and you can even order them online. The item is called 'catadiopric rectilinear wide-angle lens' and you can buy one for $105.00. But don't forget the 10% sales tax and a $50.00 shipping charge.
Of course, this lens is not really designed for mass markets. Instead, here are some of the applications envisioned for it.
One possible application, Kweon says, is to use the lens as an ingredient of intelligent security systems. In this scenario, the new catadioptric lens would capture a large swath of space, and a camera with "pan-tilt" ability would zoom in on the region of interest (ROI), such as the location of an intruder. This can be more effective, Kweon says, than a multitude of cameras watching their respective ROIs.
[Another] possibility, he says, is as a robot navigational aid. "When this lens is installed on a ceiling, the room is captured in a perspectively correct manner. In other words, the captured image is a scaled version of the room. Therefore it is easier to estimate distances and object sizes, and it can help home robots to effectively navigate the room," he says.
The latest research work about this lens has been published by Applied Optics under the name "Wide-angle catadioptric lens with a rectilinear projection scheme" (Vol. 45, Issue 34, pp. 8659-8673, December 1, 2006). Here is a link to the abstract.
This lens will also been presented during ODF'06, the 5th International Conference on Optics-photonics Design & Fabrication which be held in Nara, Japan, on December 6-8, 2006, in a paper about "A wide-angle catadioptric lens for video surveillance."
And for more information, you should read "Catadioptric Panoramic Lens with a Rectilinear Projection Scheme," a previous paper published by the Journal of the Korean Physical Society (Vol. 48, No. 4, April 2006, Pages 554-563). Here is a link to this paper (PDF format, 10 pages, 1.44 MB). Just be sure to look at the last page to discover how such a lens could be used for indoor security.
Sources: Optical Society of America news release, via EurekAlert!, November 30, 2006; and various websites
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