We show how a sinusoidal fringe pattern can be obtained by using a single cube beam splitter based on the Gates’ interferometer configuration. When an expanded and collimated laser beam hits the binding edge of a nonpolarizing cube beam splitter parallel to the splitter coating, it generates interference fringes at the exit due to the internal reflections and refractions of the laser beam passing through the cube. Unlike common digital projection systems, the proposed optical arrangement generates a perfectly sinusoidal and continuous fringe pattern, minimizing the problems associated with the discretization of a synthetic digital signal. The fast Fourier transform and phase-shifting techniques are used to demodulate the captured fringe patterns. Experimental results are presented for the three-dimensional shape reconstruction of the relief of a coin and of a spherical indentation on a piece of aluminum with a maximum height of about 150 μm. In addition, we evaluate the accuracy and resolution of the proposed measuring device: shape reconstruction accuracy is about 1.4% and axial resolution is 0.15 μm. Due to its simple and compact setup, the proposed system is particularly suited to be miniaturized.
A simple strategy based on wavefront propagation in the Fresnel regime to reduce a ringing effect by using an ideal filter in off-axis digital holography (DH) is presented. In addition, we demonstrate a better focusing capacity by using this ideal filter than Butterworth and Gaussian methods. It also provides a way to increase the visibility of the refocused plane by reducing the influence of the out-of-focus planes. We also use the unique feature of the refocusing capability of DH in the reconstructed and enhanced image, which is obtained from the averaging operation between the image at the focused image plane (z=zhd0) and the first Talbot distance order (z=zhd1). This distance is determined by the periodic ringing. Reductions of 50% of these anomalies are computed in simulation and 30% is obtained experimentally (nearly 2 nm). Also a numerical simulation shows that the focusing resolution is directly related to the filter size and shows a 0.8 mm focus zone with an ideal filter. Numerical simulations and experimental results are carried out to validate the proposal.
In this work we present a different method to reduce shot noise in phase imaging from digital holograms. An averaging
process of phase images reconstructed with different reconstruction algorithms of the complex amplitude of a phase
object in digital holographic microscopy. We obtain an improved phase image reaching a 29% of shot noise reduction.
We use a single object complex amplitude that is needed to perform our proposal. Also show the corresponding
simulations and experimental results. As phase sample test we used a micro-thin film step surface made at home of 100
nm high of TiO2 on a glass substrate of 4.7 mm thickness, our system was calibrated and traceable to an Atomic Force
Microscope results.
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