English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Existing holographic techniques (holography, speckle interferometry) [1] enable the measurement of surface displacements or material strains that are due to mechanical, thermal or vibration stresses. The measurement range is mainly determined by the wavelength of the laser used by such techniques; e.g. typically 500-600 nm for visible lasers. Therefore typical displacement dynamic range capabilities are between 10 nanometers to 20 micrometers. Visible laser based holographic interferomety is well established at CSL and has been used in previous projects for the characterization of submillimetric reflectors [2], or thermo-mechanical behaviour of space structures [3]. Expertise gained from these and other applications in (ESA) space projects has led to the following conclusions. First, ESA often demands the (non-contact) measurement of structural deformations or displacements during thermal vacuum cycling over large temperature ranges. In many cases the displacements are too large to be measured by coherent optical techniques employing visible wavelength sources. Second, due to their inherent sensitivity (visible wavelength) optical techniques require opto-mecahnical stabilities, which are typically fractions of a wavelength. They are then also very sensitive to environmental perturbations and require specially adapted operational environments. Based on this a GSTP activity was launched with the aim of developing a technique based on digital holography at 10.6 μm wavelength (LWIR range), associating CO2 lasers with thermal infrared imagers.

Development of digital holography in the long wave infrared range for assessment of space reflectors