Optical systems can benefit strongly from freeform surfaces; however, the choice of the right surface representation is not trivial and many aspects must be considered. In this work, we discuss the general approach classical globally defined representations, as well as the basic mathematics and properties of the most commonly used descriptions and present a new description developed by us for describing freeform surfaces.

New projection concepts based on OLED (organic light-emitting diode)-microdisplays will be presented. Up to now mostly all projection systems are based on reflective and/or transmissive microdisplays like digital micromirror devices (DMDs), nematic liquid crystals displays (LCDs) or liquid crystal on silicon displays (LCOS). But the size of necessary light source and illumination optics is a strong limitation for the miniaturization of the projection system itself or for system integration. Here we propose to use a high-brightness OLED-microdisplay as active element for image or pattern generation, giving the possibility to realize compact projection or imaging units. Optical parameters of the microdisplays are determined to get input data for optical system design. Based on these experimental results specially adapted optical systems are designed. First prototypes and realized projection systems for applications in optical 3Dshape detection are presented

An ultra compact projection system for mobile application based on OLED microdisplay has been developed. This OLED projection system will be integrated into a wearable optical system like mobile phone or PDA. System design and realized prototype of the projection lens will be presented.

For a lot of HMD application it is desirable to know where the user is looking at. For this purpose an ocular OLED‐HMD system with collinear eye‐tracking was developed. A viewing angle of 36° is realized in combination with an eye‐tracker FOV of 20mm. The system is desired for medical applications.

Optical systems can benefit strongly from freeform surfaces, however the choice of the right representation isn` t an easy one. Classical representations like X-Y-polynomials, as well as Zernike-polynomials are often used for such systems, but should have some disadvantage regarding their orthogonality, resulting in worse convergence and reduced quality in final results compared to newer representations like the Q-polynomials by Forbes. Additionally the supported aperture is a circle, which can be a huge drawback in case of optical systems with rectangular aperture. In this case other representations like Chebyshev-or Legendre-polynomials come into focus. There are a larger number of possibilities; however the experience with these newer representations is rather limited. Therefore in this work the focus is on investigating the performance of four widely used representations in optimizing two ambitious systems with very different properties: Three-Mirror-Anastigmat and an anamorphic System. The chosen surface descriptions offer support for circular or rectangular aperture, as well as different grades of departure from rotational symmetry. The basic shapes are for example a conic or best-fit-sphere and the polynomial set is non-, spatial or slope-orthogonal. These surface representations were chosen to evaluate the impact of these aspects on the performance optimization of the two example systems. Freeform descriptions investigated here were XY-polynomials, Zernike in Fringe representation, Q-polynomials by Forbes, as well as 2-dimensional Chebyshev-polynomials. As a result recommendations for the right choice of freeform surface representations for practical issues in the optimization of optical systems can be given