Microscopic TV shearography for characterization of microsystems.

We demonstrate a microscopic TV shearographic configuration for characterization of microsystems by measuring the slope under relatively large out-of-plane deformation. In the optical arrangement, a long working distance zoom imaging system is combined with a conventional Michelson shear interferometer. The experimental results on a microelectromechanical system pressure sensor subjected to external pressure load are presented.

Simple technique for obtaining photoacoustic spectra corrected for the spectral variation of the source in single scan.

A simple technique is presented to obtain normalized photoacoustic (PA) spectra corrected for the spectral variation of the source in a single scan. The input light beam is passed through the center of a dual slot chopper, which splits it into two chopped output beams at two different frequencies at a fixed ratio. The beams fall on the sample and the reference kept side-by-side in the same sample chamber. The PA signals are detected by a microphone and processed by two lock-in amplifiers tuned at two different frequencies. The technique is tested by recording the PA spectra of standard samples.

Use of spatial phase shifting technique in digital speckle pattern interferometry (DSPI) and digital shearography (DS).

Digital speckle pattern interferometry (DSPI) and digital shearography (DS) are well known optical tools for qualitative as well as quantitative measurements of displacement components and its derivatives of engineering structures subjected either static or dynamic load. Spatial phase shifting (SPS) technique is useful for extracting quantitative displacement data from the system with only two frames. Optical configurations for DSPI and DS with a double aperture mask in front of the imaging lens for spatial phase shifting are proposed in this paper for the measurement of out-of-plane displacement and its first order derivative (slope) respectively. An error compensating four-phase step algorithm is used for quantitative fringe analysis.

Heterodyne temporal speckle-pattern interferometry.

In temporal speckle-pattern interferometry deformation information is extracted by a Fourier transform technique from the speckle pattern that is recorded over a period of time as the object is deformed. A limitation of the experimental arrangements reported to date is that the direction of the deformation cannot be determined. We propose removing this limitation by using the heterodyne principle. Some experimental results that were obtained by use of a rotating half-wave-plate frequency shifter are presented.

Multiple-beam wedge-plate shear interferometer for collimation testing.

We describe a modification of the wedge-plate shear interferometer for collimation testing. The surface of the wedge plate is coated to increase the reflectivity such that multiple-beam interference takes place resulting in sharp fringes. In addition to sharpening the fringes also tend to split when the test beam is noncollimated. This splitting has been used as a test criterion for collimation testing. Experimental results are presented.

Modified double-wedge-plate shearing interferometer for collimation testing.

A modified configuration of the double-wedge-plate shearing interferometer for collimation testing is described. Results of the measurements to determine the setting sensitivity with this configuration are presented.

Collimation testing with linear dual-field, spiral, and evolute gratings: a comparative study.

A comparative study of the performance of linear dual-field, spiral, and evolute gratings for collimation testing with Talbot interferometry is reported.

Double-wedge-plate interferometer for collimation testing: new configurations.

Some new configurations of a wedge-plate interferometer are described that use two wedge plates for collimation testing with a built-in reference unlike a single wedge plate for which an external reference is required. Theory and measurement results are presented.

Talbot interferometry in noncollimated illumination for curvature and focal length measurements.

We describe a simple method for measuring the radius of curvature by using Talbot interferometry in a noncollimated light beam. This scheme can also be used to determine the focal length of the collimating lens employed in the setup. Results of the measurements are presented. A discussion of achievable accuracies and the proper choice of parameters is included.

Direct determination of focal length by using Talbot interferometry.

A new and simple technique for the determination of the focal length of positive lenses and concave spherical surfaces by Talbot interferometry is described. Results of measurements are presented. We show that high measurement accuracy can be achieved with this technique.

Universal digital speckle shearing interferometer.

A speckle shear interferometer is presented which can be used to yield lateral, radial, rotational, and inversion shear fringes in real time in conjunction with a digital image processing system. A modification of the optical arrangement yields reversal or folding shear as well. Experiments are conducted on an edge-clamped diaphragm with concentrated load. Unit contrast fringes have been obtained by resorting to nonlinear processing techniques such as level slicing. The results are presented for various types of shear.

Optical frequency shifter for heterodyne interferometry using counterrotating wave plates.

A method of optical frequency shifting for heterodyne interferometry based on counterrotating wave plates is described. It is possible with this technique to obtain a higher-frequency shift with fewer components.

Ellipsometer nulling: coupling and setting uncertainty.

During the nulling of an ellipsometer, coupling is experienced between its adjustable components. In this paper a criterion for coupling is reported, which is useful from a practical point of view. The criterion has been applied to known cases in generalized and conventional ellipsometry. The influence of coupling and detector sensitivity on the setting uncertainty of the adjustable components has been studied. A discussion of the choice of the nulling scheme has been included.