Double pulse-electronic speckle interferometry (DP-ESPI)

The double-pulsed speckle interferometry method is very much simpler than the double pulse holographic interferometry and allows a quick analysis of the interferograms without the development of films and hologram reconstructions. It is thus well suited to be used in an industrial environment. Using 3 cameras and three illumination directions (in order to have three sensitivi ty vectors) it is possible to measure 3-D deformations

Double pulse-electronic speckle interferometry

The double-pulsed speckle interferometry method is very much simpler than the double pulse holographic interferometry and allows a quick analysis of the interferograms without the development of films and hologram reconstructions. It is thus well suited for industrial applications. The system can be extended to determine the three components of the deformation by illuminating the object from three directions and by observing with three cameras. Double-pulsed ESPI can be used to measure rotating objects with an optical derotator which compensates the rotation of the object optically

Hyperspectral phase imaging based on denoising in complex-valued eigensubspace

A new denoising algorithm for hyperspectral complex domain data has been developed and studied. This algorithm is based on the complex domain block-matching 3D filter including the 3D Wiener filtering stage. The developed algorithm is applied and tuned to work in the singular value decomposition (SVD) eigenspace of reduced dimension. The accuracy and quantitative advantage of the new algorithm are demonstrated in simulation tests and in the processing of the experimental data. It is shown that the algorithm is effective and provides reliable results even for highly noisy data

Opposed-view dark-field digital holographic microscopy

Scattering and absorption belong to the major problems in imaging the internal layers of a biological specimen. Due to the structural inhomogeneity of the specimen, the distribution of the structures in the upper layers of a given internal structure of interest is different from the lower layers that may result in different interception of scattered light, falling into the angular aperture of the microscope objective, from the object in each imaging view. Therefore, different spatial frequencies of the scattered light can be acquired from different (top and bottom) views. We have arranged an opposed-view dark-field digital holographic microscope (DHM) to collect the scattered light concurrently from both views with the aim to increase the contrast of internal structures and improve the signal-to-noise ratio. Implementing a DHM system gives the possibility to implement digital refocusing process and obtain multilayer images from each side without a depth scan of the object. The method is explained and the results are presented exemplary for a Drosophila embryo

Derivatives obtained directly from displacement data

Two flexible shearing methods taking the derivative information directly from the data for displacement measurement are reported. The displacement information is obtained using a holographic recording directly on a CCD (charge-coupled-device) chip. Besides the advantage of taking the displacement information and the derivative information from a same set of data, other characteristics of these methods are that the derivative sensitivity can be controlled after recordings and displacement derivatives along arbitrary directions can be chosen easily. One method is based on the electronic recording which keeps the complex amplitudes of the wave fronts in a computer. The other needs only the phase modulo 2π of the displacement

Contouring by electronic speckle pattern interferometry employing divergent dual beam illumination

For contouring of large object surfaces by means of electronic speckle pattern interferometry divergent illuminations were used. A method to shift dual illumination beams was employed to obtain contour fringes. The relationship between the fringes and object depth does not have the same form as in the case of collimated illuminations. It shows that the original measurement data can be corrected. Theoretical analysis and experimental results are presented which are in agreement with each other

Double pulse-electronic speckle interferometry

In this paper we describe a double-pulsed electronic speckle interferometry system. Two separated speckle patterns are recorded within few microseconds using a charge-coupled device camera, the two images are then stored in a frame grabber and the subtraction method is applied. A quantitative analysis of the fringes using the spatial-carrier phase-shift method is presented. The results show that this method is well suited to study transient vibrations

Scatter-plate microscopy with spatially coherent illumination and temporal scatter modulation

Scatter-plate microscopy (SPM) is a lensless imaging technique for high-resolution imaging through scattering media. So far, the method was demonstrated for spatially incoherent illumination and static scattering media. In this publication, we demonstrate that these restrictions are not necessary. We realized imaging with spatially coherent and spatially incoherent illumination. We further demonstrate that SPM is still a valid imaging method for scatter-plates, which change their scattering behaviour (i.e. the phase-shift) at each position on the plate continuously but independently from other positions. Especially we realized imaging through rotating ground glass diffusers