Fringe localization using focus measure

Abstract

A method for automated evaluation of fringe localization using focus measure is demonstrated experimentally. Dual-illumination digital holographic interferometry is used to generate phase difference maps (PDMs) of a rough test object. Focus measure values of the PDMs along the axial direction (increment: 10λ=6.33 μm) yield an inverted bell-shaped curve which, in turn, facilitates the characterizations of the plane and region of fringe localization. The method can be applied in the distance measurement of rough objects and in the optimization of fringe visibility.

Combining two focus measures to improve performance

“…The focus measure (FM) computes the focus level of an image, and it is used in many applications such as shape from focus [1], passive autofocus [2], multi-focus image fusion [3] and fringe localization [4]. The performance of the FM affects the identification of focused pixels, and it determines the application results of the above techniques.…”

Vibration detection using focus analysis of interferograms

“…Statistical focus measures have been applied in the analysis of spatially varying optical reconstructions. In digital holography, axial plots of reconstructed amplitude maps and phase maps have been processed for three-dimensional object localization [20][21][22], depth-of-field extension [23] and, recently, for the determination of the plane of fringe localization [24]. We believe there has been no reporting on the application of statistical focus measures in the analysis of time-varying optical interference patterns, specifically for vibration detection.…”

Automatic method for focusing biological specimens in digital lensless holographic microscopy

“…Some of these strategies were extended to the scenario of digital holographic microscopy (DHM) where the numerical recovering of the recorded image eases the application of self-focusing approaches. A large variety of methods has been applied or shows potential to have quantitative focusing of the reconstructed images [3][4][5][6][7] including phase difference imaging [8]; most of these techniques have been applied mainly in off-axis DHM. For the particular case of digital lensless holographic microscopy (DLHM), which is an in-line architecture, a self-focusing method based on the analysis of the evolution of the intensity along the direction of propagation has been also developed [9].…”