Zooming in on lenses

The University of Central Florida has signed a licensing agreement with Holochip Corporation for a portfolio of technologies that will allow zoom lenses, such as those used in digital cameras and camera phones, to be made a lot smaller without compromising clarity.
 
Shin-Tson Wu, provost-distinguished professor of optics, and his research team at UCF’s College of Optics and Photonics, have developed and patented technologies in the field of adaptive lenses, some of which closely replicate the working of the human eye.

Holochip, based in Albuquerque, New Mexico and San Francisco, supplies such specialised lenses to manufacturers of camera phones, digital still cameras, medical and military equipment and other products. Under the agreement with the UCF Research Foundation, Holochip gains exclusive worldwide rights to Wu’s adaptive lens patents, including five US patents and numerous foreign applications.

Conventional zoom lenses rely on mechanically moving groups of glass or plastic lenses in order to adjust focus, magnification and field of view. Adaptive lenses, however, offer the ability to change focal lengths while eliminating the need to mechanically change the location of the lens. And it is all done in miniature. The typical aperture size for a lens in a cell phone, for example, is one to two millimetres in diameter.

‘We have the ability to make these lenses from less than a millimetre to a couple of centimetres in size,’ Wu said. 

Wu, who joined UCF in 2001 after 18 years at Hughes Research Laboratories, is known for his advances in the fields of liquid crystal displays (LCDs) and liquid-crystal (LC) optics.

Wu was one of the first researchers to recognise the need for adaptive lenses, and he has directed research that resulted in two distinct approaches.

The first, LC lenses, is based on the ability of liquid-crystal materials to alter their refractive index in the presence of an external electric field. With the appropriate selection of LC materials, substrates and device architecture, lenses can be created that adjust their focal length upon an applied voltage.

The second approach, fluidic lenses, was inspired by principles of the human eye. The lens comprises a transparent optical fluid that is encapsulated within a flexible lens membrane and substrate. Upon compression of the lens body, the shape of the flexible lens membrane is modified, which results in an adjustment of the focal length of the lens.

Since this approach provides a wide range of focal power with almost no optical loss, it can be implemented in compact camera modules, making it attractive for size-limited applications such as digital cameras and cell phones. Likewise, the LC lens offers the ability to control high-order aberrations that can lead to blurriness, making it attractive in applications such as free-space optical communications, adaptive optics, corrective eyewear and cameras.

Holochip, a manufacturer of adaptive lenses, recently announced its flagship product, an adaptive polymer singlet lens, at the Conference on Lasers and Electro-optics (CLEO-2007) in Baltimore, Maryland.

This photo shows a tunable focus liquid lens in action. The lens replicates the function of the human eye. The lens pictured was built for demonstration purposes, so the aperture was expanded to 15 millimetres, or roughly the diameter of a penny. The lenses that are made for miniaturised applications, such as for cell phones, are one to two millimetres in diameter