DIGITAL OFF-AXIS HETERODYNE HOLOGRAPHIC INTERFEROMETRY

摘要

The invention relates to a digital holography method for detecting the vibration amplitude of an object (15) having a vibration frequency ω, comprising: generating object illumination waves (Wt) and reference waves (WLO); acquiring interferograms between the reference wave (WLO) and a signal wave (W≯) by means of a bandwidth a s detector (19), the reference wave comprising two components ELO, ELO1 of frequencies ω1, ω2 that are respectively staggered in relation to the laser frequency ωL by a quantity δ1=γ1ω, and δ2=qω+γ2ωδ, where q is an integer and −0.5≦γ1, γ2≦0.5; and calculating the vibration amplitude of the object from the optical beats spectrum deduced from the complex amplitude of an interferogram.

主权项

1. A digital holography method for detecting an amplitude of vibration of an object at least one vibration frequency, comprising:
the generation of an object illumination laser wave of frequency and of a reference wave coherent with the illumination wave; the acquisition, by means of a two-dimensional optoelectronic detector of temporal bandwidth, of a set of interferograms resulting from the interference of the reference wave and of a signal wave from the object, the signal and reference waves exhibiting an angular shift, the field of the reference wave comprising a first component of frequency and at least one second component, of frequency, the frequencies and being offset from the frequency of the laser wave respectively by a determined quantity δ1, δ2, with δ1=γ1ωS and δ2=qω+γ2ωS, where q is a relative integer and −0.5≦γ1,γ2≦0.5; and the processing of the interferograms comprising:
the calculation of a hologram of the object from each interferogram, the hologram being defined by the complex amplitude of the signal wave in a given spatial field of a plane of the object;the calculation of the time-frequency Fourier transform of the complex amplitudes of said holograms, making it possible to obtain, at each point of the spatial field, a frequency spectrum of the optical beats between the frequency components of the reference wave and of the signal wave, the optical beats spectrum comprising at least two bands for frequencies equal to the frequency offsets δ1 and δ2; andthe calculation, for each point of the spatial field from the ratio of the amplitudes of the first band and of the second band, of the amplitude of the vibration of the object.