Leszek A. Salbut

New contra old wavefront measurement concepts for interferometric optical testing

Three new and modified wavefront analysis concepts for interferometric optical testing are presented, specifically a moire fringes version of a temporal phase-shifting method and spatial-carrier phase-shifting and Fourier transform methods. All of these techniques require working with a finite fringe observation field in the interferometer, therefore additional analysis of the imaging optics is necessary. The impact of the interferometer construction and the method of analysis on the measurement error is discussed. A detailed experimental and theoretical comparison of the techniques is presented to fulfill a wide range of user requirements.

Hybrid experimental-numerical concept of residual stress analysis in laser weldments

The concept, methodology and instrumentation for hybrid experimental-numerical residual stress analysis in a laser weldment are presented. Grating interferometry and digital speckle photography are applied as complementary experimental methods for the determination of the initial model of residual strains and of the material properties at the various zones of a laser weldment. These data inserted into a finite element model enable one to analyze the formation of the residual stress state of the object, which is compared and modified by means of experimental data in a closed iterative loop. This full hybrid approach is tested successfully on a laser-welded steel specimen in uniaxial tensile tests.

Combined measurement of silicon microbeams by grating interferometry and digital holography

In this paper the methodology and instrumentation for the investigation of the silicon microbeam behavior under tensile and bending loads are described. The tests are performed by means of Automated Grating Interferometry (AGI) and Digital Holography (DH). Both methods deliver a direct approach to a highly sensitive measurement of surface displacements. In combination with simulation tools (analytical or FEM models) the material parameters can be determined. Consequently the main aim of the measurements is to determine the three Cartesian components of the displacement vector.

Phase manipulation and optoelectronic reconstruction of digital holograms by means of LCOS spatial light modulator

Fresnel and Fourier holograms recorded by CCD/CMOS cameras can be numerically or optoelectronically reconstructed in order to provide visualization of 3D objects or to enable further manipulation of their phases and amplitudes. In the paper we propose to introduce into digital holographic (DH) setup Liquid Crystal on Silicon (LCOS) spatial light modulator as an active 2D optoelectronic element which facilitates performing a variety of operations at the recording and reconstruction stages. This includes introducing phase shifting digital holography, additional phase manipulation for object contouring and displacement measurements as well as for optoelectronic reconstruction of all types of digital holograms. The results of initial experiments performed with LCOS are presented and discussed. Also the future directions of development of active DH and DHI system are outlined.

Active microelement testing by interferometry using time-average and quasi-stroboscopic techniques

Increasing technological capabilities to produce active microelements (incl. microbeams, micromembranes and micromirrors) and their expanding areas of application introduce unprecedented requirements concerning their design and testing. The paper presents a concept of an optical measurement system and methodology for out-of-plane displacement testing of such active microelements. The system is based on Twyman-Green microinterferometer. It gives the possibility to combine the capabilities of time average and quasi-stroboscopic interferometry methods to find dynamic behavior of active microelements (e.g., resonance frequencies and amplitude distributions in vibration modes). For mapping the zero-order Bessel function modulating the contrast of two-beam interference fringes the four-frame technique is applied. The calibration of the contrast variation in time-averaged interferograms enables quantitative evaluation of the vibration amplitude encoded in the argument of the Bessel function. For qualitative estimation of the vibration amplitude sign a simple quasi-stroboscopic technique is proposed. In this technique, laser pulses have the same frequency as the signal activating the microelement under test. This self-synchronous system enables to visualize the shape of the tested element at maximum deflection. Exemplary results of measurements performed with active micromembranes are presented.

Three-channel phase stepped system for moire interferometry

A use of the multichannel phase stepped interferometry approach to automated fringe pattern analysis in moire interferometry is described. Polarization optics is used to implement the appropriate phase shifts in each channel. The channels are created by inserting a diffraction grating at the output of the interferometer. It is possible to work at one frame rate. This system enables studies in unstable environmental conditions and studies of time dependent events.

Multifunctional interferometric platform for on-chip testing the micromechanical properties of MEMS/MOEMS

We develop a multifunctional interferometric platform for testing MEMS/MOEMS, measuring 3-D out-of-plane deflections and providing both material properties and motion behavior of microdevices. Specific metrology procedures are demonstrated to determine respectively the residual stress of silicon membranes compressively prestressed by SiOxNy plasma-enhanced chemical vapor deposition (PECVD), the vibration modes of PZT microactuators, as well as the expertise of scratch drive actuators.

The optical measurement station for complex testing of microelements

Abstract The paper presents a concept of optical measurement station for complex testing of microelements including MEMS, MOEMS and electronic components and assemblies. The wide selection of examples proves that the specific measurement requirements are fulfilled by alternative usage of combined conventional and grating interferometers CI/GI (reflective surfaces), in-plane and out-of-plane ESPI (scattering surfaces) and digital holographic interferometry DHI (mixed surfaces) supported by thermovision. All these methods are realized by integrated microinterferometer (IWaM) based on a glass waveguide or air cavity waveguide arrangements. The air cavity IWaM allows to form a thermal output for combined thermovision CI/GI or ESPI measurements. IWaM has a compact design insensitive to mechanical vibrations and may be easily rearranged to work with the selected measurement techniques. It is also fully integrated with an optical microscope and it is designed to work both in laboratories and in production environments.

Polarization phase shifting method for moire interferometry and flatness testing

Described in this short paper is an implementation of the phase shifting technique for computer-aided processing of interference fringes obtained by the moire interferometry method for in-plane displacement measurements or in a similar arrangement used for out-of-plane displacement (flatness) determination. The polarized light approach was selected because of the common path propagation of the interfering beams. The experimental verification is presented.

Waveguide grating (moire) microinterferometer for inplane displacement/strain field investigation

Analysis of microelements requires a local approach to their mechanical behavior and material constants distribution. This requires modern full-field measurement tools, among which automated grating (moire) interferometry (GMI) is one of the best-suited measurement methods. A new type of grating microinterferometer is presented. It is based on the concept of an achromatic grating interferometer combined with a glass block waveguide and designed to work with standard optical microscopes. The various types of waveguide plates are presented and discussed. The interferogram obtained may be modified and design for analysis by means of carrier frequency phase shifting methods. The methodology of measurement is described. The usefulness of the microinterferometer is demonstrated by an example of in-plane displacement and strain distribution determination in the two-phase steel polycrystalline material. 0-