Holographic contouring and its limitations in nearly specularly reflecting surface measurement

Abstract

The applicability of the digital holography to grinded surfaces shape measurements is experimentally examined with regard to the surface micro-roughness of brittle materials (optical glass). Multi-wavelength phase shifted digital holographic interferometry (holographic contouring) is used and its performance is analyzed. Holographic contouring is a great candidate for the precise shape measurement technique, which can be applied to the iterative manufacture process of optical elements. Optical surface artifacts with different radii of the spherical (convex and concave) shapes were prepared with different micro-roughness. Their optical surfaces were then holographically recorded using a designed setup. Two different measures were selected to estimate the quality of the holographic recording: first, the intensity profile of the reconstructed surface deviation as a consequence of the micro-roughness decrease, where the shape of the intensity profile develops as the surface is altering from strongly diffusive to almost specular; second, the correlation of the phase fields (surfaces shapes), which were holographically recorded using two light beams of different wavelengths. In this situation, the correlation function decreases with an increase in the noise amount in data. The presented preliminary results indicate that the multiwavelength holographic contouring can be used for surface measurements of high-quality polished and nearly specular surfaces. On the other hand, the application of holographic contouring to polished surface measurement still represents a challenging task and remains unresolved even with the multidirection illumination.

Correlation-coefficient based auto-focusing algorithm for focus detection in shape measurement using two-source digital holographic interferometry

“…This modulation is directly correlated with the correlation of the two speckle wave fields E 1 (z) and E 2 (z). Generally, the speckle CC between two speckle fields is calculated to describe this modulation, which will also be used in our paper; the standard speckle CC γ(z) corresponding to different reconstruction dis tances can be expressed as [16]…”

Digital Holographic Interferometry for the Measurement of Symmetrical Temperature Fields in Liquids

“…There is a vast field of applications of DHI and other interference based methods including: entertainment display [8], imaging heat transfer and mass transfer [7,[9][10][11][12][13], research in free convection [14,15], visualization of the 3D velocity vector field in turbulent boundary layer [6], analysis of supersonic jets [6], biological (living cell imaging) [6,16], environmental applications [6,17], precision measurements [8,18,19], small displacements [20], thermomechanical analysis and non-destructive testing [6], microscopy and high-resolution volume imagery [21,22], vibrometry [23,24], topography [25,26], process monitoring [7], computerized tomography [7,27], and so on. This paper aims at investigating heat transfer problems.…”