Wide-range absolute angle measurement based on a broadband solid etalon fringe using a mode-locked femtosecond laser

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A wide-range absolute angle measurement method based on a broadband interference fringe of a Fabry-Pérot solid etalon using a mode-locked femtosecond laser is investigated. A novel method for interference order determination, which utilizes the inherent sequential correlation of interference orders between multiple fringe peaks, is proposed to enable wide-range angle measurements without phase ambiguity problem. To ensure absolute angle measurement accuracy, the dispersion formula of the solid etalon corresponding to its nominal thickness is derived using an angle scanning method to determine accurate angle measurement parameters. Measurement experiments using a constructed optical setup are conducted to validate both the proposed interference order determination technique and measurement performances using derived dispersion formula.