Trichromatic laser interferometry uses three monochromatic lines (red, green, and blue) as the light source for an interferometer. The optical technique combines the advantages of differential interferometry using a white source (for measuring small path-length differences), a unique central white fringe (zero path-length difference), and separate-reference interferometry (measuring large path-length differences). The time variation of the mass density field can be reconstructed by taking several instantaneous interferograms in succession.
Optical Setup
Innova Spectrum 70 laser (mixed argon and krypton), 4.2 W power in multi-line mode
Parasitic lines filtered out by birefringent grating and Glan-Thomson polarizers
100 mW in red, green, and blue lines each
Laser polarization rotated by achromatic semi-wave grating
50 µm slit added for better interference fringe contrast
Laser implanted as Onera interferometer light source
Laser implanted as Onera interferometer light source