Phase contrast microscopy, is a technique that can be used to produce high-contrast images of transparent objects. The
technique employs a phase mask, at the object Fourier transform plane, to create a synthetic reference wave that
interferes with the object wave at the image plane. However, the fabrication and alignment of these masks is an
expensive and delicate process. In this work, we present a nonlinear phase contrast microscope that can be implemented
with a conventional optical microscope using a low power CW coherent light source to illuminate the specimen. An
intensity dependent refractive index material is used to photoinduce the filter. Therefore, the aligning procedure is
greatly simplified. The nonlinear material is a thin cell of dye doped liquid crystal where it is possible to produce a
tunable phase delay depending on the incident light intensity, the light polarization, and the temperature. Due to these
characteristics the resulting setup is relatively inexpensive, easy to implement, and extremely robust.
Many problems in metrology and optical tomography have to recover information from the wrapping phase. In most of the cases, phase, that is associate to a physical magnitude, is continuous and generally, varies smoothly. Therefore, we can say that the problem in these cases is reduced to find a continuous phase. Considering this, many solutions to this kind of problems have been proposed, from the use of local planes to the implementation of most robust algorithms. However, these methods are also very slow. That is why the unwrapping problem is an open subject research in optics. We propose a phase unwrapping method based on finite differences that is fast and robust. In addition, it is easy to program.
Flow visualization refers to a method used for qualitatively obtain information in the field of fluid mechanics. In this work, we show a simple single lens system using laser light illumination to observe flow dynamics using a setup similar to the schileren setup. As we will detail, it is based on a phase contrast technique in which the filter is made of a nonlinear optical material, therefore it is self-aligned and depends mainly on the illuminating intensity. Due to these characteristics, the resulting setup is extremely robust and builds up within a few milliseconds.
Flow visualization refers to a method used for qualitatively obtain information in the field of fluid mechanics. In this work, we show a simple single lens system using laser light illumination to observe flow dynamics using a setup similar to the schileren setup. As we will detail, it is based on a phase contrast technique in which the filter is made of a nonlinear optical material, therefore it is self-aligned and depends mainly on the illuminating intensity. Due to these characteristics, the resulting setup is extremely robust and builds up within a few milliseconds.
The nonlinear common path interferometer is a simple and robust single lens optical processor using an intensity dependent medium placed on its geometrical focal plane to observe deformed wavefronts. It is described either as a nonlinear inteferometer or as an image processor. We demonstrate that this system requires excess surrounding illumination beyond the geometrical boundaries of the disturbance to operate. We discuss recent progress on this setup. In particular, the effect of large phase changes in the filter and the dynamics of the filter formation.
In this work, we show a simple single lens system using laser light illumination to observe flow dynamics. It is based on a phase contrast technique in which the filter is made of a nonlinear optical material, therefore it is self-aligned and depends mainly on the illuminating intensity. Due to these characteristics, the resulting setup is extremely robust and builds up within a few milliseconds.
In this paper we demonstrate a novel phase contrast system that employs a BR film. Since the filter is optically induced by the Fourier transform of the phase object, no alignment is necessary at the filter plane making it extremely robust. Due to the optical properties of BR films the phase filter can be induced with low light intensity levels. The material response allows operation at video frame rates, processing of high spatial resolution objects, and the use of relatively inexpensive laser sources. Such characteristics and the fact that BR films can be produced at a low cost makes the system simple to implement, relatively inexpensive and extremely robust. The effects of varying the illuminating area beyond the phase object area and filter saturation are also analyzed.
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