Testing Of Micro-optics Research Articles

Characterization of microlenses by digital holographic microscopy

We demonstrate the use of digital holographic microscopy (DHM) as a metrological tool in micro-optics testing. Measurement principles are compared with those performed with Twyman-Green, Mach-Zehnder, and white-light interferometers. Measurements performed on refractive microlenses with reflection DHM are compared with measurements performed with standard interferometers. Key features of DHM such as digital focusing, measurement of shape differences with respect to a perfect model, surface roughness measurements, and optical performance evaluation are discussed. The capability of imaging nonspherical lenses without any modification of the optomechanical setup is a key advantage of DHM compared with conventional measurement tools and is demonstrated on a cylindrical microlens and a square lens array.

Micro optics and lens arrays

Micro optics and lens arrays have been the focus of biennial meetings held at the National Physical Laboratory since 1991, organized with the help of the Optical Group of the Institute of Physics. The subject and its associated community have evolved over the years and micro optics is well established as an important field. Applications range from coupling and switching of light from fibres to controlling illumination in displays and generating 3D images. Microstructured surfaces are used to depixellate images in microdisplays, concentrate light in semiconductor devices and to shape laser beams. In particular, micro optics has enabled the development of compact optical systems with novel properties and hybrid electro-mechanical systems such as MOEMS. After a break in the pattern of biennial meetings in 1999, it was decided to continue the spirit of that series with a one-day meeting on fabrication, applications and testing of micro optics, held at the Institute of Physics in London on 14 September 2001. The result was an international programme of 11 papers, 3 poster papers and a small equipment exhibition, attended by more than 60 delegates, 15 of whom came from overseas. Unfortunately, unforeseen events meant that some of the American authors could not travel to present their papers but reserve papers and discussion filled the gap. Thanks are due to all those who contributed to the meeting and to the Institute of Physics for arranging the venue and other administration. Selected papers from the meeting are published in this issue of Journal of Optics A: Pure and Applied Optics. Richard Stevens National Physical Laboratory, Teddington, UK Guest Editor