When coherent light from a laser beam is passed through a transparent reduction of a variable-density or variable-area record section, the seismic signal acts as an optical grating to produce a diffraction pattern which is the two-dimensional Fourier transform of the section itself. With suitable lenses the diffraction pattern can be converted back into an image of the original section. By obstructing portions of the pattern corresponding to particular frequencies or dips on the section, one can remove such frequencies or dips from the reconstructed image. The equipment developed is described. Applications include removal of multiple reflections, elimination of noise which consists of traveling events having different apparent velocities from the reflections, removal of diffractions or their enhancement to delineate faults, and attenuation or elimination of ringing in marine shooting.

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