Whole 3D-digital holographic measurements of vibrating objects

An optoelectronic system based on digital holography is used to measure the three dimensional vector components and object shape of a vibrating object. Pulses from a ruby laser, with a separation in the range from 1 to 1000 microseconds, are used to record holograms on CCD sensors, which are later digitally reconstructed. Three different illumination directions are used to get the deformation along three different sensitivity vectors, that are afterwards combined into a 3D resultant deformation. To measure the shape of the object the two-wavelength method is used. The wavelength change is produced by changing the distance between the plates of the laser output etalon, thus obtaining the shape by subtracting the phases of the wavefronts recorded at those wavelengths. The data sets for the shape and SD-deformation are combined and graphically shown. Finally, by using a non linear crystal (BBO) it was possible to double the frequency of the radiation emitted by the ruby laser allowing to get two wavelengths (694 nm and 347 nm) simultaneously and thus to record digital holograms with different sensitivities.