Decomposition of biospeckle images in temporary spectral bands.

We present a method of analysis of images of dynamic speckle based on the filtering in frequency bands of the temporary history of each pixel. Butterworth filters are applied to the temporary evolution, and different images are constructed showing the energy in each frequency band. Different degrees of activity of the sample in study, presumably attributed to different origins, are found. The method is exemplified with images of bruising damage in fruits and of biological activity in germinating corn seeds. It is found that the activity in the bruised region of an apple differs from the activity of healthy regions in a certain characteristic frequency range. The activity of the embryo can also be distinguished from that of the endosperm in corn seeds during germination.

Speckle interferometry applied to pharmacodynamic studies: evaluation of parasite motility.

The work reported here describes the application of the optical technique known as dynamic speckle interferometry to evaluate the motility of nematode parasites exposed to different anthelmintic drugs. This technique, a well proven tool for assessing the time evolution of different phenomena, is here successfully used to quantify parasite motility in pharmacodynamic assays. The characterization of the pharmacological properties of anthelmintic drugs is critical to optimize their use in parasite control. Besides, the evaluation of nematode motility is a relevant indicator of the pharmacodynamic effect of anthelmintic drugs. The application of this approach to study the motility of Haemonchus contortus (used as a model of nematode parasites) larvae exposed to different drugs is presented, showing its usefulness.

Determination of the zero-order fringe position in digital speckle pattern interferometry.

A method for determining the position of the zero-order fringe in a metrological experiment with digital speckle pattern interferometry is proposed. It is based on an averaging procedure with shifted images obtained before and after a load is applied. This technique is a complement to the phase-shifting methods. Experimental examples are shown.

Sign ambiguity in speckle metrology.

We comment on the propagation of the sign ambiguity produced in the Burch experiment when out-of-plane movements are measured by use of several points of view. The existence of this problem in photogrammetry is also considered.

Light-in-flight digital holography display.

We present a digital speckle-pattern interferometric setup that can be operated at TV frame rates (30 ms) to display the locus of the points at which the optical-path difference between the reference and object beams is within the coherence length. Experimental results are shown.

Simultaneous multiple-viewpoint processing in digital speckle pattern interferometry.

Digital speckle pattern interferometry provides information on deformations equivalent to that given by image holography. Thus more than one viewpoint is necessary for the description of three-dimensional deformation vectors. We report the use of a diffraction-grating technique to process simultaneously the three or more required viewpoints of a digital holography experiment.

Three-dimensional speckle measurements with a diffraction grating.

A method to measure three-dimensional displacements through a speckle technique is proposed. This measurement is possible by adding a diffraction grating to the classical bidimensional Burch experimental setup. The principle is described and results are discussed.

Double-slit camera.

This Technical Note is a comment on the imaging properties of the double-slit camera. We show its application to the correction of geometrical distortions and propose some other possibilities.

Single-beam digital holographic contouring.

A method for digital holographic contouring that uses a diffraction grating to generate the reference beam and to introduce adequate phase delay in the object beam is described.

Optical dynamical processing: an approach using birefringent pupils.

A new technique is proposed to perform several image-processing operations with the same optical system. Each operation can easily be selected by properly loading a birefringent photoelastic plate, which acts as the spatial filter of the-system. Thus different pupil transmittance configurations can be achieved, each of which is associated with a certain image transformation.

Display of the complex degree of coherence due to quasi-monochromatic spatially incoherent sources.

A method for displaying the complex degree of coherence (CDC) of a quasi-monochromatic spatially incoherent source is proposed. The phase of the CDC is encoded in a method similar to that used in interferometric imaging with incoherent light. The method is based on Fourier analysis of the speckle pattern that appears when a diffuser is illuminated with the partially coherent field whose CDC is to be displayed. In addition, an intensity pattern that resembles the spatial distribution of the incoherent source can also be obtained.