Holger Brünner

Ray tracing through a schematic eye containing second‐order (quadric) surfaces using 4 × 4 matrix notation

Ray tracing is used in ophthalmology for evaluation of the optical properties of the eye. We demonstrate an algebraic method for tracing a bundle of rays through the optical system of an eye containing aspheric surfaces. Restricting to second‐order surfaces (quadric surfaces) such as ellipsoids, paraboloids or hyperboloids, a surface is described by a 4 × 4 matrix. In this case, the normal vector can be derived analytically and the ray‐surface intersection is calculated by solving a quadratic equation. We applied this straightforward matrix‐based strategy to the spherical 4‐surface Le Grand schematic eye, and the Le Grand eye modified by Kooijman containing four aspheric surfaces. We calculated the spot diagram for the focal plane as well as a pre‐ and post‐focal plane for both model eyes, and found that the optical quality of the aspheric model characterized by the ray scatter in the spot diagram at the focal plane is much better than that of the spherical model. This calculation strategy may be helpful for evaluating the image distortion of decentred or tilted spherical or aspheric artificial intra‐ocular lenses.

CCD-based projectional imaging of fluorescent probes in tissue-like media: experimental setup and characterization.

In this article, a non-contact imaging setup for the acquisition of multiple 2D projections of fluorescent probes in tissue-like phantoms is described. The setup basically consists of a high-sensitivity CCD camera for the detection of fluorescence and a rotating broad-beam light source for the continuous illumination of a rotatable phantom located in the rotation center. This allows for imaging of various projections in a full angular projection range of 360°. Beside the detailed description of the system layout, important key characteristics of the setup are outlined. The setup is demonstrated with projectional measurements of a tissue-like phantom and the results are verified by comparison of the projection-dependent fluorescence intensity distributions with corresponding 2D simulations. It is shown that the instrument is suitable for the sensitive detection of fluorescence emanating from fluorescent objects in tissue-like phantoms. Such setup could facilitate the collection of large projection data sets as they are used in optical fluorescence tomography of small animals.

[Erratum to: Effect of transparent yellow and orange colored contact lenses on color discrimination in the yellow color range].

Dr. M. Schürer Medizinische Optik, Institut für Medizinische Physik Universität Erlangen-Nürnberg Erlangen michael.schuerer@oncoray.de M. Schürer1,5 · A. Walter2,5 · H. Brünner3,5 · A. Langenbucher4,5 1 OncoRay – Nationales Zentrum für Strahlenforschung in der Onkologie, Technische Universität Dresden, Dresden, Deutschland 2 Steiner-Optik GmbH, Bayreuth, Deutschland 3 VisioCraft GmbH, Erlangen, Deutschland 4 Experimentelle Ophthalmologie, Universität des Saarlandes, Homburg (Saar), Deutschland 5 Medizinische Optik, Institut für Medizinische Physik, Universität Erlangen-Nürnberg, Erlangen, Deutschland

Impact of colored contact lenses on color vision

This paper presents a new measurement setup aimed at determining the change in colour perception due to the use of colored contact lenses. These lenses are promoted as having the effect of improving color contrast vision in certain, sports-related activities, but this claim lacks objective confirmation by means of proper measurement techniques. The color matching method described herein is of objective nature, based on the works of MacAdams, employing so-called discrimination ellipses, fitted on colour discrimination thresholds on axis in the two-dimensional space of visible color coordinates. The ellipse centers are transformed to the origin of the coordinate system to compare the ellipse parameters with and without tinted contact lenses. The measurement of the change of color perception by the examination of the change of the smallest distinguishable color differences in presentation tests can be considered as an objective method without influences of luminescence differences or pattern presentation features.