Sumários
LIGO - overview
22 Abril 2024, 14:00 • José Manuel Rebordão
LIGO overview. GW observatories. Main subsystems.
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2D sampling
19 Abril 2024, 09:00 • José Manuel Rebordão
2D Sampling. Main equations of Shannon theory.
Artifacts in case of non-band-limited function or disrespect of Nyquist
frequency.
Superposition of periodic patters. Analysis in
direct and Fourier space.
Visual band: reference to the MTF and to the
Contrast Sensitivity Function.
Emergence of
low frequencies from linear combinations of pattern-related frequencies.
Stables and unstable superpositions.
Applications: Hidden indicia, printing, security.
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LIGO - introduction
Introduction to LIGO architecture.Wavefront metrology (class 2 in 3)
17 Abril 2024, 15:00 • 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. 2D Sampling
15 Abril 2024, 14:00 • José Manuel Rebordão
JWST - Overview of JWST critical
technologies made available for all types of optical instruments
Sampling in physics. Examples of artifacts on
sampled images oh known or unknown nature.
Modelling the sampling process.
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JWST cophasing
12 Abril 2024, 09:00 • José Manuel Rebordão
Zernike decomposition of phase distributions.
Review of phase retrieval methods, examples.
Characteristics of the different phases of the cophasing
process.
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