Real-time hybrid fringe pattern analysis using a linear digital phase locked loop for demodulation and unwrapping

Gdeisat, Munther; Burton, David R.; Lalor, Michael J.

doi:10.1088/0957-0233/11/10/309

Cited by 9 publications

(2 citation statements)

References 13 publications

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“…The conventional PLL method can be simply explained as a variant of the well known synchronous detection method, in which the measured and reference signals are multiplied, and a reference signal phase is tuned according to the measured signal phase to minimize the phase difference. The PLL method has been recently applied to a good-quality fringe analysis [8,9]. A few PLL method modifications are known [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The PLL method has been recently applied to a good-quality fringe analysis [8,9]. A few PLL method modifications are known [7][8][9][10]. In particular, it was proposed [9] to use the linear PLL for fringe signal demodulation, where measured and reference signals subtraction is used instead of multiplication in the phase detector in order to avoid the generation of a high-frequency component.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of spectral modulated interferograms using a Fourier transform and the iterative phase-locked loop method

Gurov¹,

Hlubina

Chugunov³

2002

Meas. Sci. Technol.

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Spectral modulated interference fringes are observed in the form of the periodical modulation of a broadband spectrum at the output of an interferometer provided with a subsequent spectrometer. The group optical path difference of interfering light waves corresponding to the distance from the surface to be measured is characterized by the spectral fringe phase function. To recover the phase functions, a standard, Fourier-transform method, or parametric methods like a phase-locked loop (PLL) method, can be used. In the former case, the Fourier spectrum in the wavelength domain is computed and filtered out to obtain the reference spectrum and the overall phase information using a phase-unwrapping algorithm. In the latter case, the fringe phase deviations are traced dynamically in the independent variable domain, i.e. in the wavelength domain when the PLL method is applied to spectral interferometry. The PLL method was used to demodulate spectral fringes iteratively. A spectral fringe signal with a priori unknown carrier fringe frequency is considered and at the first iteration step a fringe phase equal to zero is supposed. The second iteration takes the demodulated phase found from the first iteration etc. As a result, the unwrapped phase function of the spectral fringes is found.

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