Measurement of in-plane deformations of microsystems by digital holography and speckle interferometry(Invited Paper)

The reliability of microsystems is an important issue and for their quality inspection, it is necessary to know the displacements or deformations due to the applied mechanical, thermal, or electrostatic loads. We show how interferometrical techniques like digital holography and speckle interferometry can be used for the measurement of in plane deformations of microsystems with nanometric accuracy and we give a description of the measurement uncertainties.

Measurement of out-of-plane deformation of curved objects with digital speckle pattern interferometry

Digital speckle pattern interferometry （DSPI） is a high-precision deformation t technique for planar objects. However, for curved objects, the three-dimensional （3D） shape information is needed in order to obtain correct deformation measurement in DSPI. Thus, combined shape and deformation measurement techniques of DSPI have been proposed. However, the current techniques are either complex in setup or complicated in operation. Furthermore, the operations of some techniques are too slow for real-time measurement. In this work, we propose a DSPI technique for both 3D shape and out-of-plane deformation measurement. Compared with current techniques, the proposed technique is simple in both setup and operation and is capable of fast deformation measurement. Theoretical analysis and experiments are performed. For a cylinder surface with an arch height of 9 mm, the error of out-of-plane deformation measurement is less than 0.15 μm. The effectiveness of the proposed scheme is verified.

Digital Speckle Technique Applied to Flow Visualization

Digital speckle technique uses a laser, a CCD camera, and digital processing to generate interference fringes at the television framing rate. Its most obvious advantage is that neither darkroom facilities nor photographic wet chemical processing is required. In addition, it can be used in harsh engineering environments. This paper discusses the strengths and weaknesses of three digital speckle methodologies. (1) Digital speckle pattern interferometry (DSPI) uses an optical polarization phase shifter for visualization and measurement of the density field in a flow field. (2) Digital shearing speckle interferometry (DSSI) utilizes speckle\|shearing interferometry in addition to optical polarization phase shifting. (3) Digital speckle photography (DSP) with computer reconstruction. The discussion describes the concepts, the principles and the experimental arrangements with some experimental results. The investigation shows that these three digital speckle techniques provide an excellent method for visualizing flow fields and for measuring density distributions in fluid mechanics and thermal flows.

New multiplexed system for synchronous measurement of out-of-plane deformation and two orthogonal slopes

We propose a novel system for synchronous measurement of out-of-plane deformation and two orthogonal slopes using a single camera. The linearly polarized reference beam introduced by an optical fiber interferes with the unpolarized object beam to measure the out-of-plane deformation. A modified Mach–Zehnder interferometer is used to measure the two orthogonal slopes of the out-of-plane deformation. One of the object beams of the Mach–Zehnder interferometer is an unpolarized beam, and the other object beam is split into two orthogonal linearly polarized object beams by a polarizing prism. The two beams are orthogonally polarized. Hence, they will not interfere with each other. The two polarized beams respectively interfere with the unpolarized beam to simultaneously measure the two orthogonal slopes of the out-of-plane deformation. In addition, the imaging lens and apertures are respectively placed in three optical paths to independently control the carrier frequencies and shearing amounts. The effectiveness of this method can be proved by measuring two pressure-loaded circular plates.