Daniel Englisch

Variable ultrabroadband and narrowband composite polarization retarders

We propose and experimentally demonstrate novel types of composite sequences of half-wave and quarter-wave polarization retarders, permitting operation at either ultrabroad spectral bandwidth or narrow bandwidth. The retarders are composed of stacked standard half-wave retarders and quarter-wave retarders of equal thickness. To our knowledge, these home-built devices outperform all commercially available compound retarders, made of several birefringent materials.

Mesopic increment detection sensitivity, Part 2: Modelling mesopic detection sensitivity

This paper deals with the modelling of the mesopic detection sensitivity data described in Part 1. The modelling is based on a linear combination of the spectral sensitivity templates of four retinal mechanisms (long + medium wavelength sensitive cones, rods, short wavelength sensitive cones and long - medium wavelength sensitive cones opponency) to describe the experimental data on mesopic detection sensitivity and to provide a practically usable model. Model parameters representing the weighting of these mechanisms are analysed as a function of target eccentricity and background luminance.

Mesopic increment detection sensitivity, Part I: Phenomenological analysis

Mesopic threshold detection sensitivity was investigated by projecting quasi-monochromatic incremental targets with 22 centroid wavelengths between 422 nm and 652 nm onto different backgrounds. Every detection target was observed by at least nine subjects under eight different viewing conditions: two mesopic luminance levels (0.1 cd/m2; 1 cd/m2) and four eccentricities of target appearance off the visual axis (0°, 2.65°, 10° and 20°). Results were expressed in terms of absolute detection sensitivity values, i.e. inverse increment radiance values for each target at the detection threshold in sr·m2·W−1 units. In this part, the experimental method is described, and the dataset is analysed in terms of retinal mechanisms.