Agatsuma, KazuhiroRabeling, DavidVan Beuzekom, MartinVan Den Brand, Jo2025-06-102025-06-10http://www.scopus.com/inward/record.url?scp=85011598934&partnerID=8YFLogxKhttps://hdl.handle.net/1885/733757963A preliminary experiment and usage of the phase camera is reported on here. The phase camera is a frequency selective wavefront sensor of the laser beam, which is utilized for observing phase-modulated laser beam (sidebands) in an interferometric gravitational wave detectors. The laser modulation/demodulation technique plays an essential role in readout of the mirror displacement for accurate position controls. The sideband signals in the power recycling cavity are easily degraded by mirror aberrations in the configuration of a marginally stable cavity. Recently, the phase camera is being applied for monitoring such aberrations in Advanced Virgo. The observed aberrations will be corrected by CO2 lasers and compensation plates.enPublisher Copyright: © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.201485011598934