Lensless digital-holographic interferometry for the measurement of large objects

A method for the recording of digital holograms of large objects on electronic sensors is presented. An aperture is located between the object and the charge coupled device (CCD) sensor. A reference point source is located close to the aperture. The distance between the aperture and the CCD, its size and the location of the point source are chosen in order to permit the sensor to record the spatial frequencies of the interference pattern between the reference and the object light going through the aperture. The reconstruction is done digitally by performing a Fourier transform of the recorded intensity and filtering in the Fourier plane in order to get the complex amplitude of the object wavefront in the plane of the aperture. The imaging of the object in a plane is done by simulation of the propagation wavefront. (C) 1999 Elsevier Science B.V. All rights reserved.