Phase retrieval

12 Maio 2023, 12:00 • José Manuel Rebordão

The phase in optical fields.

Zernike functions. Generation of modified Zernike basis for arbitrary shape pupils

Phase retrieval concepts: curvature sensing and iterative methods

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Parametroc methods. Phase Diversity

Wavefront metrology (1 in 3)

10 Maio 2023, 11:00 • Alexandre Pereira Cabral

A Shack-Hartmann wavefront sensor was built based on an array of lenses that divide / sample the incoming wavefront into small sub-apertures, focusing independently the light from each lens in a 2D sensor that captures the focal plane pattern. This pattern was processed in order to obtain the position of each focus point from each individual lens.

 An incident plane wave was created using a spatial filter and a collimated lens to produce a grid of equidistant focal points, the reference position, while several distorted waves (corresponding to a point source from an optical fibre in controlled positions) result in an uneven distribution of points that were referenced to the ideal plan wave situation in order to determine with the sensor the position of the fibre tip, using the Shack-Hartman sensor to measure an unknown wavefront based of the focus shifts from the calibration.

JWST - MIRI

8 Maio 2023, 10:00 • José Manuel Rebordão

Pick-off Mirrors in JWST; the special case of MIRI POM.

Presentation of Nuno Covas: JWST – the MIRIS instrument (3^rd part): the Mid-resolution Spectrometer (MRS)

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JWST - MIRI

5 Maio 2023, 12:00 • José Manuel Rebordão

Presentation of Nuno Covas: JWST – the MIRIS instrument (2^st part): input optics and calibration, imager, Low resolution spectroscopy (slit and slitless)

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JWST – MIRI

Holography (2 in 2)

3 Maio 2023, 11:00 • Alexandre Pereira Cabral

Setup of a Denisyuk configuration, consisting of a volume-reflection holography technique. As a recording medium, a silver halide emulsion on a glass plate will be used (a matrix of cohesive silver crystals in a transparent medium). During exposure, the reference wave and the waves reflected from the object result in an interference structure that was recorded within the emulsion.

Students produced their own objects that will be exposed in a 50 mm x 50 mm plate.

Students performed several exposures using different types of objects (including lenses or mirrors to generate holographic optical elements known as HOE.