arXiv subjects

Jose M. Diazdelacruz

Publications and source records attributed to Jose M. Diazdelacruz.

3 recordsLinked to original sources

arXiv2014

Windowed defocused photographic speckle vibration measurement

The out-of-plane vibration of a rough surface causes an in-plane vibration of its speckle pattern when observed with a defocused optical photographic system. If the frequency of the oscillations is high enough, a time-averaged specklegram is recorded from which the amplitude of the vibration can be estimated. The statistical character of speckle distributions along with the pixel sampling and intensity analog-to-digital conversion inherent to electronic cameras degrade the accuracy of the amplitude measurement to an extent that is analyzed and experimentally tested in this paper. The relations limiting the mutually competing metrological features of a defocused speckle system are also deduced mathematically.

physics.optics↗

arXiv2005

Adaptive Aperture Defocused Digital Speckle Photography

Speckle photography can be used to monitor deformations of solid surfaces. The measuring characteristics, such as range or lateral resolution depend heavily on the optical recording and illumination set-up. This paper shows how, by the addition of two suitably perforated masks, the optical aperture of the system may vary from point to point, accordingly adapting the range and resolution to local requirements. Furthermore, by illuminating narrow areas, speckle size can be chosen independently from the optical aperture, thus lifting an important constraint on its choice. The new technique in described within the framework of digital defocused speckle photography under normal collimated illumination. Mutually limiting relations between range of measurement and spatial frequency resolution turn up both locally and when the whole surface under study is considered. They are deduced and discussed in detail.

physics.optics↗

arXiv2004

Multi-windowed defocused speckle photographic system for tilt measurement

Defocused speckle photography has long been used to measure rotations of rough surfaces. This paper explains how, by adding a suitably perforated mask, some measurement properties, such as range or lateral resolution, may be changed at wish. Particularly, the maximum measurable tilt can be significantly raised, although at the expense of poorer lateral resolution. Advantages over previously described techniques include independent tuning of speckle size and optical system aperture and more extended adaptability to different measuring needs. The benefits and disadvantages of the new and old techniques are thoroughly compared.

physics.optics↗