Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Origami lens' slims high resolution cameras

01.02.2007
Engineers at UC San Diego have built a powerful yet ultrathin digital camera by folding up the telephoto lens. This technology may yield lightweight, ultrathin, high resolution miniature cameras for unmanned surveillance aircraft, cell phones and infrared night vision applications.

“Our imager is about seven times more powerful than a conventional lens of the same depth,” said Eric Tremblay, the first author on an Applied Optics paper published February 1, 2007, and an electrical and computer engineering Ph.D. candidate at UCSD’s Jacobs School of Engineering. Eric is working with Joseph Ford, a professor of electrical and computer engineering at the Jacobs School who leads the camera project within UCSD’s Photonic Systems Integration Lab. Ford is also affiliated with the UCSD division of the California Institute of Telecommunications and Information Technology, Calit2.

“This type of miniature camera is very promising for applications where you want high resolution images and a short exposure time. This describes what cell phone cameras want to be when they grow up,” said Ford. “Today’s cell phone cameras are pretty good for wide angle shots, but because space constraints require short focal length lenses, when you zoom them in, they’re terrible. They’re blurry, dark, and low contrast.”

To reduce camera thickness but retain good light collection and high-resolution capabilities, Tremblay and colleagues replaced the traditional lens with a “folded” optical system that is based on an extension of conventional astronomical telescopes that employed mirrors, such as the Cassegrain telescope, which was developed in 1672.

“The folding idea was new in 1672, but they were doing it with two separate mirrors. We cut all of our reflective surfaces out of a single component and quadrupled the number of folds,” said Ford.

Instead of bending and focusing light as it passes through a series of separate mirrors and lenses, the new folded system bends and focuses light while it is reflected back and forth inside a single 5 millimeter thick optical crystal. The light is focused as if it were moving through a traditional lens system that is at least seven times thicker.

“When all is said and done, our camera will look a lot like a lens cap that can be focused and used as a regular camera,” said Ford.

“Traditional camera lenses are typically made up of many different lens elements that work together to provide a sharp, high quality image. Here we did much the same thing, but the elements are folded on top of one another to reduce the thickness of the optic,” said Tremblay. “Our ‘folded lens’ is not technically a lens, since it is reflective. I am guilty of calling it a lens sometimes, but I’m trying to control myself. ‘Imager,’ or ‘folded optic’ are more accurate.”

Folding the optic addresses performance issues facing today’s cell phone cameras by increasing the “effective focal length” – the zooming power of the camera – without increasing the distance from the front of the optic to the image sensor.

“The larger the number of folds in the imager, the more powerful it is,” said Ford.

On a disk of calcium fluoride – a transparent optical crystal – the engineers cut a series of concentric, reflective surfaces that bend and focus the light as it is bounced to a facing flat reflector. The two round surfaces with 60 millimeter diameters are separated by 5 millimeters of transparent calcium fluoride.

This design strategy forces light entering the ring-shaped aperture to bounce back-and-forth between the two reflective surfaces. The light follows a predetermined zigzag path as it moves from the largest of the four concentric optic surfaces to the smallest and then to the CMOS light sensor.

This kind of lens folding has not been widely implemented as a means to slim cameras down, but recent advances in the mechanical machining process of “diamond turning” are changing that. The engineers used a diamond tip to cut all the reflective surfaces onto a single calcium fluoride disk.

“You mount the optic once and the diamond machining tool cuts all the optical surfaces without having to adjust the setup,” explained Tremblay. Not having to realign the optic during the machining of the reflective surfaces reduced an important source of error and helped make folding a viable approach for camera slimming.

In mass production, diamond turning would be used to create a master for a molded-glass element, bringing the cost in line with the inexpensive molded glass aspheres found in current compact cameras.

In the laboratory, the engineers compared a 5 millimeter thick, 8-fold imager optimized to focus on objects 2.5 meters away with a conventional high-resolution, compact camera lens with a 38 millimeter focal length.

At best focus, the resolution, color and image quality are very similar between the two cameras, the authors report.

One initial drawback with the new folded camera was its limited depth of focus. Digital post-processing techniques and design changes were successfully implemented in the latest generation of the camera. The authors note that this latest generation of the technology will be covered in future publications.

The team is now designing variable-focus folded optical systems that have air between the reflective surfaces of the imager. Such imagers may be especially useful for lightweight, inexpensive infrared vision applications. The all-reflective systems also enable ultra-broad-spectrum imaging and thus may be useful for ultraviolet lithography – an emerging technique for squeezing more transistors onto silicon in order to create more powerful chips.

When asked about the likelihood of folded optics making their way into cell phone cameras, Tremblay said, “I don’t know, but I’m hopeful. I think it’s a good possibility.” Picking up a domino-sized, next-next-generation prototype 5 times smaller than the disk shaped imager described in the Applied Optics paper, he said, “You can see how much smaller this has gotten already. It’s going to keep shrinking.”

This work is part of a larger Multi-Domain Optimization research team led by Prof. Mark Neifeld at the University of Arizona, which includes a related UCSD research effort on nanophotonics led by Prof. Yeshaiahu Fainman, and researchers from CDM Optics and MIT. This research is funded by the U.S. Department of Defense Advanced Research Projects Agency (DARPA) through Dennis Healy’s MONTAGE program.

To create fully-functional prototype imagers, the UCSD engineers partnered with Ron Stack and Rick Morrison of Distant Focus Corporation an optical systems company that designed the camera’s electronic circuit boards and also developed the interface and control software.

Daniel Kane | EurekAlert!
Further information:
http://www.ucsd.edu

More articles from Power and Electrical Engineering:

nachricht Researchers take next step toward fusion energy
16.11.2017 | Texas A&M University

nachricht Desert solar to fuel centuries of air travel
16.11.2017 | SolarPACES

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>