Depth of focus can be enhanced with cubic phaseplates located at the exit pupil of an optical system without significant loss of resolution. The enhancement factor is proportional to the strength of the phaseplate. The digital image is inversely filtered. The stronger the phaseplate is the stronger the inverse filter function must be. This causes increasing noise for high spatial frequencies in the restored image. Therefore, an optimum strength of the cubic phaseplate has to be chosen for the respective situation. A variable phaseplate system has been realized and tested. The performance of the setup has been experimentally studied. Applications and practical aspects are discussed in particular regarding barcode readers.

In the manufacturing process of aspheric glass lenses, the polishing step plays a key role with respect to the final quality of the lens as well as to the manufacturing costs. Due to the changing radius of curvature sub aperture tools are used for polishing aspherical lens elements. Even with small tools the changing radius has a significant influence to the wear function [1] [2]. This paper describes a method to calculate the removal based only on the surface shape and the material parameters of the tool.The described method can be used for any kind of surface, e.g. for freeform shapes.

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The variation of the friction coefficient in the polishing process is investigated comparing the results of a numerical simulation with polishing experiments. To improve the accuracy of the predicted wear in the simulation a method is presented to measure the friction coefficient in relation to the relative velocity using an offset tool.

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