Abstract: A new halographic method for converting one wave into another wave by means of a hologram is disclosed. This method comprises mixing an object wave with a reference wave whose wave front in the hologram plane is different from that of the actual reconstruction wave in the same plane. The phases and possibly also the amplitudes of these two wave fronts are combined in such a way that compensation is obtained for imaging errors caused by mutual inconsistencies between the wavelength ratio, the hologram scaling and the object scaling, and a displacement of the reconstructed object relative to the hologram. The reference wave and the reconstruction wave are chosen so that the converted object wave field becomes "as equal as possible" to a wave field coming from another but geometrically similar object at a different wavelength. In an example concerning seismic holography a formular for choosing a proper synthetic reference wave is given.

Abstract: An arrangement for concentrating sea waves, includes a grid-like structure of stopping and/or delaying elements adapted to influence the amplitude and/or phase of the waves and located in such positions in the water that the elements in interaction with the incident sea waves form an interference pattern which gives a concentration of the wave energy in a limited area (concentration area). When the wave energy is to be utilized for power production, the grid-like element structure is designed to give a concentration of the wave energy in a concentration area located in the short-range field of the element structure. Preferably the elements in the structure are mainly situated in front of the concentration area with respect to the dominant wave incident directions. Moreover, the element structure may have an extension (aperture) which is substantially larger than the wave length of the dominant waves at the location.

Abstract: An arrangement for concentrating sea waves, includes a grid-like structure of stopping and/or delaying elements adapted to influence the amplitude and/or phase of the waves and located in such positions in the water that the elements in interaction with the incident sea waves form an interference pattern which gives a concentration of the wave energy in a limited area (concentration area). When the wave energy is to be utilized for power production, the grid-like element structure is designed to give a concentration of the wave energy in a concentration area located in the short-range field of the element structure. Preferably the elements in the structure are mainly situated in front of the concentration area with respect to the dominant wave incident directions. Moreover, the element structure may have an extension (aperture) which is substantially larger than the wave length of the dominant waves at the location.