2 August 2004 Double-source interferometry for reducing spurious noise fringes
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A new technique of double-source interferometry is proposed, which can suppress spurious noise fringes arising from the interference with unwanted lights reflected from a surface that is not under test. Two collimated beams from a pair of mutually incoherent monochromatic sources are introduced into an interferometer to generate two sets of interference fringes, each of which is a superposition of signal fringes and noise fringes. The key idea is to choose the angle between the two beams in such a manner that the noise fringes generated by one beam become 180 degree out of phase from those generated by the other beam; thereby the noise fringes are canceled out while the signal fringes are maintained. The technique is also suited to the measurement of an optical parallel plate where noise fringes are unavoidable because of reflection from the rear surface. Experimental results are presented that demonstrate the validity of the proposed principle.
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Zhiqiang Liu, Takeshi Gemma, Saori Udagawa, Mitsuo Takeda, "Double-source interferometry for reducing spurious noise fringes", Proc. SPIE 5531, Interferometry XII: Techniques and Analysis, (2 August 2004); doi: 10.1117/12.560335; https://doi.org/10.1117/12.560335

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