Better photos from your mobile

Because of their small aperture, they already offer reasonable sharpness, but poor light can make it difficult to take pictures indoors, and the results are often out of focus. In the future, some mobile telephones will be equipped with two cameras, and we can also see a trend in the direction of functions such as autofocus and zoom becoming more and more common.

The Horton company Ignis Display saw interesting possibilities in this area, and it contacted SINTEF, which had some ideas about how this functionality could be transferred from ordinary camera to mobile telephones. A project is already under way, and as well as being able to focus extremely rapidly, the new lens will also be inexpensive and be of good optical quality.

“Eye-blink”

The idea is based in principle on the way that the eye functions with its own autofocus mechanism. In human beings, as in all mammals, the lens consist of a soft transparent substance. Round the lens is a muscle that controls the thickness of the lens according to the distance on which we wish to focus. For objects close to us, the muscle relaxes, so that the lens becomes thicker in the middle, while it contracts and the lens becomes thinner when we focus on objects at greater distances. Ignis Display’s new lens is also made of soft material, a low-density polymer that can be easily formed and that can change its shape almost like a muscle. The polymer is installed on a silicon circuit together with piezoelectric elements which convert electrical signals to mechanical forces and give the polymer whatever lens shape is required.

The scientists started by building a demonstration version of the lens with nuts and bolts and wires in order to demonstrate that the principle would work.

“Our first prototype will soon be ready for testing, and we will continue to improve and miniaturise it. This has been an interdisciplinary project in which our ceramics scientists have developed a robust and stable piezoelectric element, while the plastics scientists have been working on the polymer,” says senior scientist Dag T. Wang of SINTEF ICT.

Production

The next stage will be that scientists at Ignis Display and SINTEF – in collaboration with other partners – will continue the process of miniaturisation and the development of a suitable manufacturing technology.

The technology employed in making the lenses involves producing not just one lens or chip, but between one hundred and a thousand items at a time, depending on the size of the silicon wafer used. This approach is essential if Ignis Display is to compete on the international market with a reasonably priced product.

“We deposit material on silicon wafers that have space for a large number of chips. Then we place a mask over the wafer, create the pattern of the circuit on it by photolithography and etch it. We produce large numbers of identical circuits every time. What makes our production of micro-sized structures possible is the fact that we have been working on ceramics and piezoelectric materials in SINTEF for many years,” says Wang.

The people at Ignis Display bring together several wafers and install the polymer, before integrating the tiny lens module with the necessary electronics and other lens elements.

Growing market

Today, virtually all mobile telephones have at least one camera. Many people in the industry believe that it is only a matter of time until telephones will be equipped with two; one on each side, for conferences and presentations via mobile telephone. Given the steady increase in the number of mobile telephones sold, and a doubling of the number of cameras in each unit, there is obviously a lot of money to be made in this field.

Ignis Display ‘s technology has aroused a great deal of interest both in Norway and abroad. Although the company has several competitors, Ignis Display believe that it is likely that millions of mobile cameras will be taking photographs with its lenses within a few years.

By Jan Helstad/Åse Dragland.