Proyecto de Investigación: SPACE SOLAR PHYSICS: PHI FOR SOLAR ORBITER AND IMAX AND SP FOR SUNRISE
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ESP2016-77548-C5-5-R
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Advanced iterative algorithm for phase calibration of spatial light modulators integrated in optical instrumentation in a vibration environment
(Optica Publishing Group, 2020-07-30) Silva-López, Manuel; Uribe Patarroyo, Néstor; Álvarez-Herrrero, Alberto; Agencia Estatal de Investigación (España)
We present a method to obtain the phase modulation characteristic curve of a spatial light modulator (SLM) under severe vibration conditions. The procedure is based on the well-known advanced iterative algorithm (AIA), which allows wavefront extraction from unknown phase-shifted interferograms. Generally, AIA is used to determine the wavefront and the determined phase shifts are of little interest. In contrast, in our method, the main goal of using AIA is to determine the unknown phase shifts induced by an SLM during the calibration procedure. Using a segmented approach to calibration, AIA enables successful calibration even in the presence of additional random phase shifts due to environmental changes. This method has the potential to calibrate SLMs integrated in complex optical instruments with little to no modifications to the optical setup, no matter the environmental conditions. We demonstrate our technique by calibrating an SLM under vacuum conditions (10−5 mbar) in a common-path configuration compatible with usage of an SLM as a wavefront modulator at the pupil plane of an instrument. Our technique compensates for the vibrations produced by the vacuum pumps and reduces an order of magnitude the root-mean-squared error of the calibration curve evaluated with vibration errors. Our technique enhances the potential use of SLMs in complex optical systems, including aerospace optical instrumentation.
Fine tuning method for optimization of liquid crystal based polarimeters
(Optica Publishing Group, 2018-04-18) Álvarez-Herrrero, Alberto; García Parejo, Pilar; Silva-López, Manuel; Ministerio de Economía y Competitividad (MINECO)
Liquid crystal variable retarders (LCVR) based polarimeters perform temporal polarization modulation by applying a sequence of driving voltages to introduce different optical retardances. However, even after a careful design and fabrication, manufacturing tolerances (i.e., slight optical axis misalignments, instrument residual polarization, optical activity in the LCVRs...) or the final system configuration (i.e., LCVRs in a convergent optical beam, thermal gradient across the clear aperture...) produce deviations from the ideal setup. As a consequence, all of these effects can reduce the polarimetric modulation efficiency of the device and, therefore, its signal-to-noise ratio. Hence, the voltage sequence applied according to the LCVR calibration curves may not be suitable to reach the optimal theoretical polarimetric efficiencies. In this work, a systematic fine tuning method for the LCVRs driving voltages is described an experimentally demonstrated.
