Browsing by Author "Bridges, Angus"

Now showing 1 - 6 of 6
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    Correction of periodic displacement non-linearities by two-wavelength interferometry
    (IOP, 2021-08-31) Bridges, Angus; Yacoot, Andrew; Kissinger, Thomas; Humphreys, David A.; Tatam, Ralph P.
    Non-linearities in interferometric displacement measurements commonly affect both homodyne and heterodyne optical interferometers. Unwanted back reflections (ghost reflections) or polarisation leakage introduce non-linearity terms at harmonics of the illuminating wavelength that cannot be fully corrected for with standard non-linearity correction techniques. A two-wavelength interferometric approach, operating at 632.8 and 785 nm, is presented here that is capable of correcting such non-linearities. Non-linearities are separated from the difference between two displacement measurements made at differing wavelengths with a Fourier approach. Compared to a standard Heydemann ellipse fitting correction, the proposed approach reduces estimated residual non-linearities from 84 to 11 pm in the case of a linear displacement profile. In particular this approach is applicable to the correction of higher order non-linearities that are caused by multiple reflections, and that are therefore very sensitive to alignment conditions.
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    Correction of periodic displacement non-linearities by two-wavelength interferometry - associated data
    (Cranfield University, 2021-08-23 10:26) Bridges, Angus; Yacoot, Andrew; Kissinger, Thomas; Humphreys, David; Tatam, Ralph
    Data associated with the publication "Correction of periodic displacement non-linearities by two-wavelength interferometry".
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    Multiple intensity reference interferometry for the correction of sub-fringe displacement non-linearities
    (IOP, 2021-12-06) Bridges, Angus; Yacoot, Andrew; Kissinger, Thomas; Tatam, Ralph P.
    Displacement measuring interferometers, commonly employed for traceable measurements at the nanoscale, suffer from non-linearities in the measured displacement that limit the achievable measurement uncertainty for microscopic displacements. Two closely related novel non-linearity correction methodologies are presented here that allow for the correction of non-linearities in cases where the displacement covers much less than a full optical fringe. Both corrections have been shown, under ideal conditions, to be capable of reducing all residual non-linearity harmonics to below the 10 pm level.
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    Multiple intensity reference interferometry for the correction of sub-fringe displacement non-linearities - associated data
    (Cranfield University, 2021-11-19 11:13) Bridges, Angus; Yacoot, Andrew; Kissinger, Thomas; Tatam, Ralph
    Data associated with the publication "Multiple intensity reference interferometry for the correction of sub-fringe displacement non-linearities".
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    Polarization-sensitive transfer matrix modeling for displacement measuring interferometry
    (Optical Society of America, 2020-09-01) Bridges, Angus; Yacoot, Andrew; Kissinger, Thomas; Tatam, Ralph P.
    The use of polarizing optics for both beam steering and phase measurement applications in displacement measuring interferometer designs is almost universal. Interferometer designs that employ polarizing optics in this manner are particularly sensitive to the effects of unwanted optical cavities that form within the optics due to polarization leakage and back reflections from material interfaces. Modeling techniques commonly employed in the design of such interferometers are poorly suited to the analysis of multiple passes through polarizing optics. A technique, along with an accompanying software implementation, is presented here that is capable of modeling the propagation of monochromatic plane waves through an arbitrary network of linear planar optical components.
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    strapy - scattering and transfer matrix model python
    (Cranfield University, 2020-04-01 11:22) Bridges, Angus; Yacoot, Andrew; Kissinger, Thomas; Tatam, Ralph
    strapy is python package implementing the combined transfer and scattering matrix modelling approach described in [1], jointly developed by the National Physical Laboratory and the Centre for Engineering Photonics at Cranfield University as part of an EPSRC funded iCASE studentship. The primary motivation to develop this software was to model the effects of multiple reflections and polarisation leakage within the optics of homodyne displacement measuring interferometers, however strapy is generally applicable to modelling the propagation of monochromatic light through networks of planar optical components. This archive record holds copies of strapy, along with the ctmm dependency and their respective documentation, as they were at the time of publication. For up to date copies of the software and documentation please refer to: - https://github.com/strapy-project/strapy - https://strapy.readthedocs.io - https://github.com/strapy-project/ctmm - https://ctmm.readthedocs.io If you find an interesting application for strapy please let us know. If you want to cite results found using strapy please cite the accompanying publication and the software DOI: A. Bridges; A. Yacoot; T. Kissinger; R. P. Tatam. 'Polarisation-sensitive transfer matrix modelling for displacement measuring interferometry', Cranfield University research data repository 10.17862/cranfield.rd.12001236