Marco Van As

Variable-focus liquid lens for portable applications

The meniscus between two immiscible liquids can be used as an optical lens. A change in curvature of this meniscus by electrowetting leads to a change in focal distance. We demonstrate that two liquids in a tube form a self-centered tunable lens of high optical quality. Several properties were studied, such as optical performance, electrical characteristics and dynamic behavior. We designed and constructed a miniature camera module based on this tunable lens and show that it is very well suited for use in portable applications.

Variable liquid lenses for electronic products

The design, manufacturing and application of variable liquid lenses are discussed. The interface between the two immiscible liquids that forms the lens can be altered with a voltage. Results are presented of applying this lens in miniature autofocus and zoom cameras, in optical recording and in illumination systems.

Highly miniaturized prototype optical drive for use in portable devices

The realization of a prototype miniaturized 5 mm height optical drive and 28 mm media is reported here. Using the optical light path as a starting point, this presentation will highlight the high degree of miniaturization that is achieved in the field of the optical pickup, optical components and mechanics. Furthermore, the use of newly developed disc media is discussed.

Single Digital Video Recording/Digital Versatile Disk objective and plastic Digital Video Recording objective

A solution based on a catadioptric lens design to make the two-element digital video recording (DVR) objective with small free working distance compatible with digital versatile disk (DVD) is presented. The design makes use of a dichroic mirror: it is reflective for 405 nm wavelength and transparent for 650 nm wavelength. First experimental results have proven the concept. Apart from compatibility also cost, weight and size reduction of DVR objective is studied by making it (partly) out of plastic. Both theoretical and experimental results show that (partly) plastic DVR objectives with low temperature dependence are possible. Successful readout experiments with these plastic DVR objectives on a DVR tester were performed.

Photo Replication of Birefringent Phase Structures

Dual layer blu-ray disc (BD) and dual layer small form factor optical drive (SFFO) as well as BD / digital versatile disc (DVD) / compact disc (CD) compatible systems, require phase structures to cope with the different amount of spherical aberration for the various different operating modes. Birefringent phase structures open up to the possibility to cope with these different amounts of aberration in the various readout modes, but so far no manufacturing methods are known which lead to low cost and stable structures. A novel replication method, based on the photo-polymerization of a liquid crystalline monomer is presented to make birefringent phase structures. Apart from enabling mass production, the process allows a phase structure to be directly produced on top of an ordinary objective lens, allowing weight and size reduction of the compatible optical pick up.

Miniaturized high-NA blue objective

In order to enable optical storage in portable devices, a small optical drive building height and thus small sized objectives are needed. A small version of the DVR objective, having numerical aperture of 0.85 and operating wavelength (lambda) = 405 nm is required, in order to have sufficient storage capacity on a small sized disc. In this paper we present a miniaturised DVR objective made of plastic. It has a building height of only 1.335 mm, enabling optical storage for various mobile applications. Making the objective out of plastic eases the manufacturing and handling. Furthermore, the two element objective was designed to have low temperature dependence which was confirmed experimentally. Experiments with this objective showed that readout of a 25 GB RW 12 cm disc is possible. Furthermore, some considerations on the benefits and expected problems in miniaturizing the actuator are presented.