Double beam systems for forming improved holograms

A system, for forming a hologram, comprising means for producing first and second primary coherent beams, a recording medium positioned between first and second cover plates with an index matching fluid included between said first and second cover plates, the first and second beams each passing to one of said first and second cover plates,

• first means for varying the phases at said recording medium of the primary beams and beams reflected from said cover plates;
• and
• first and second phase shifting means for cancelling the phase variations of the primary beams to maintain a constant relative phase therebetween while said reflected beams retain a phase variation in relation to the constant relative phase of said first and second primary beams.

A system, for forming a hologram, comprising means for producing first and second primary beams, a recording medium positioned between first second cover plates with an index matching fluid maintained between said first and second cover plates, means for continually varying at a first rate the phases of said first and second primary beams at said recording medium during a recording period and for varying, at a second rate greater than said first rate, the phase of beams reflected from a cover plate after passing through said recording medium;

• and means to vary the phase, at said first rate, of said first and second primary beams prior to passing to one of said cover plates and with a phase variation rate to cancel the phase variation of said first and second primary beams, while retaining a phase variation of said reflected beams equal to the difference between said first and second rates.

A system, for forming during a recording period a hologram from first and second primary beams received from first and second sources while eliminating spurious hologram recordings from being formed, comprising:

• a recording structure which has a recording medium and an index matching fluid positioned in spaces between first and second cover plates, and means for varying the phases at said recording medium of rays reflected from at least one of said first and second cover plates.

A system, for forming during a recording period a hologram from first and second primary beams received from first and second sources while eliminating spurious hologram recordings from being formed comprising:

• a recording structure which has a recording medium and an index mtching fluid positioned between first and second cover plates, and means for varying the phases at said recording medium of rays of the primary beams versus rays reflected from at least one of said first and second cover plates.

A system, for forming during a recording period a hologram from first and second primary beams received from first and second sources and applied to a recording structure which has a recording medium and an index matching fluid positioned in spaces between first and second cover plates while eliminating spurious hologram recordings from being formed from rays reflected from said first and second cover plates, comprising:

• first means for varying the phases at said recording medium of said reflected beams and for varying the phases of said primary beams;
• and
• second means for varying the phases of said primary beams so that the primary beams have constant phases at said recording medium.

A system for forming a hologram comprising a recording structure including a recording medium positioned between first and second cover plates, means for producing first and second primary beams applied to said first and second cover plates respectively, said beams partially passing through said plates and partially reflecting therefrom, and means for varying the path length of said reflected beams between the cover plates and the recording medium.

A system for forming a hologram comprising a recording structure including a recording medium positioned between first and second cover plates, means for producing first and second primary beams applied to said first and second cover plates respectively, said beams partially passing through said plates and partially reflecting therefrom, and means for moving said recording structure during a recording period.