Two-wavelength in-line phase-shifting interferometry based on polarizing separation for accurate surface profiling

ArticleinApplied Optics 50(33):6153-61 · November 2011with14 Reads
DOI: 10.1364/AO.50.006153 · Source: PubMed
Abstract
We describe a configuration that can be used for two-wavelength phase-shifting in-line interferometry based on polarizing separation. The experiment is conducted on a sample with a step height of 1.34 μm nominally. In this paper, five- and seven-phase step algorithms have been compared for their effectiveness in reducing the noise in the phase maps. The noise is further reduced by the application of the flat fielding method. The recorded interferograms are processed using seven-phase step algorithm to obtain the phase map for each wavelength separately. The independent phase maps are subtracted and a phase map for the beat-wavelength is obtained and converted to height map. The results extracted from the seven-phase step algorithm have been compared with the results extracted from the single shot off-axis geometry and the results are in agreement.
    • "However, due to the demand for spatial spectrum separation of a real image from the unwanted dc term and the twin image, off-axis interferometry cannot make full use of the bandwidth of CCD or CMOS camera. Moreover, due to making fast Fourier transformation or Hilbert transformation, the off-axis interferometry has a systematic noise problem and heavier computation burden than the phase-shifting interferometry (PSI) [24,25]. On the other hand, the on-axis common-path interferometry is capable of making full use of the bandwidth of CCD camera and thus can capture finer sample spatial details20212223 . "
    [Show abstract] [Hide abstract] ABSTRACT: Parallel on-axis two-step phase-shifting reflective point-diffraction interferometry for holographic phase microscopy based on Michelson architecture is proposed. A cube beamsplitter splits the object wave into two copies within the two arms. The reference wave is rebuilt by low-pass filtering with a pinhole-masked mirror. Both object and reference waves are split into two beams by a grating in a 4f imaging system; thus, two interferograms with quadrature phase-shift can be acquired simultaneously with the aid of polarization elements. The approach has the merit of nanometers-scale phase stability over hours due to its quasi-common-path geometry. It can make full use of camera spatial bandwidth while its temporal resolution is as fast as the camera frame rate. Phase imaging on microscale specimen is implemented, and the experimental results demonstrate that the proposed approach is suitable for investigating dynamic processes.
    Full-text · Article · May 2013
    • "One of these methods is the phase-shifting technique. Phase shifting is an attractive and very robust technique for the analysis of fringe patterns [2]. Phase-shifting measures the phase of a pixel depending on the values of that pixel in different images. "
    [Show abstract] [Hide abstract] ABSTRACT: The purposes of the paper are threefold: (1) to show the possibility to perform parallel phase-shifting Fizeau interferometry by using a quarter waveplate with high flatness as a reference, (2) to present a comparative study between the phase-shifting algorithm and the off-axis geometry in surface microtopography measurement, and (3) to show the advantages of using the proposed common path Fizeau interferometry over the quasi-common path Michelson interferometry in terms of accuracy in measurement. The compelling advantage of the proposed parallel phase-shifting Fizeau interferometric technique is the long-term stability that leads to measuring objects with a high degree of accuracy.
    Full-text · Article · Jul 2012
  • [Show abstract] [Hide abstract] ABSTRACT: This paper presents a quantitative comparison between off-axis digital holographic microscopy (DHM) and on-axis phase-shifting interferometry (PSI) for surface micro topography measurement. The comparison has been applied on an object of a 1.34 lm nominal step height. The experimental results show that single shot, dual-wavelength, off-axis DHM surpasses on dual-wavelength, on-axis PSI in terms of accuracy and repeatability.
    Full-text · Article · Jul 2013
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