Showing papers by "Richard Kowarschik published in 2015"
TL;DR: In this paper, an interferometric method was proposed to gain a theoretically infinite depth of field by measuring the complex coherence function using an image inverting interferometer, which yields an enhanced lateral resolution.
21 citations
TL;DR: It is demonstrated that aberrations symmetric to the optical axis do not impair the imaging quality of such a coherence imaging system and it is shown that it is possible to gain an almost complete correction of remaining aberration with the help of a reference measurement.
Abstract: We present an imaging method with the ability to correct even large optical phase aberrations in a purely numerical way. For this purpose, the complex coherence function in the pupil plane of the microscope objective is measured with the help of an image inverting interferometer. By means of a Fourier transform, it is possible to reconstruct the spatially incoherent object distribution. We demonstrate that aberrations symmetric to the optical axis do not impair the imaging quality of such a coherence imaging system. Furthermore, we show that it is possible to gain an almost complete correction of remaining aberrations with the help of a reference measurement. A mathematical derivation is given and experimentally verified. To demonstrate the ability of our method, randomly generated aberrations with peak-to-valley values of up to 8 λ are corrected.
12 citations
TL;DR: In this article, the authors described the deviation between the real and the measured object surface that occurs when a translucent object is scanned by an active triangulation system and discussed how the measurement error depends on the surface roughness, the measurement direction, and the scattering behavior of the material.
Abstract: In a previous article, we described the deviation between the real and the measured object surface that occurs when a translucent object is scanned by an active triangulation system. This error depends on the angle between the measurement direction and the object’s surface normal, the surface reflection behavior, which can be described by a bidirectional reflectance distribution function, and the light penetration behavior. In general, the error is small if the surface is perpendicular to the measurement direction; it increases if the surface is tilted and decreases again for flat angles. This error curve is additionally affected by the surface roughness. The angle dependence is more distinct for smooth surfaces. In order to predict and compensate for the error, it is necessary to understand the error-forming process. Therefore, Monte Carlo simulations of several measurements were performed. As the computational cost is very high for three-dimensional simulations, most of the simulations were performed in two-dimensional space. We present the results of these simulations and discuss how the measurement error depends on the surface roughness, the measurement direction, and the scattering behavior of the material.
9 citations
01 Jan 2015
TL;DR: In this paper, the Moire-effect was used to reconstruct object information from free space digital holograms, leading to an increase in the resolvable angle by a factor of 2 compared to phase shifting methods.
Abstract: In this paper we present a technique to reconstruct object information from free space digital holograms with the application of the Moire-effect leading to an increase in the resolvable angle by a factor of 2 compared to phase shifting methods. To do so the spatial frequencies causing the Moire-structures are repositioned in their proper position and this way increase the image quality.