Method and apparatus for holographic data storage

Apparatus for holographic recording of information, wherein:

• a) the apparatus comprises a lens or lens system, to be referred to as the FT lens, so situated that:
• light from an object beam enters the FT lens after being modulated by an object having pixels, and light leaving the FT lens impinges on a recording medium situated at a Fourier transform plane of the object with respect to the FT lens;
• b) the apparatus further comprises a phase element effectively juxtaposed with the object and having a correlation length greater than a maximum side length of the object pixels;
• c) the phase element has a spatially varying pattern of phase modulation effective for at least partially redistributing illuminant intensity of the object beam in the Fourier transform plane;
• and
• d) the phase element has the property that when the FT lens has focal length F, the object beam has wavelength λ, and the object beam is modulated by a random binary spatial light modulator having pixels of length Δ:
• (i) there falls in the Fourier transform plane a redistributed intensity pattern having an intensity envelope and at least one principal direction;
• and
• (ii) said envelope remains at no less than 50% of its peak value from the center of said pattern to a radius of 1.5×λF/Δ in any direction.

A method for holographic recording of information using a Fourier transform lens or lens system of focal length F, to be referred to as the FT lens, wherein an object beam of wavelength λ is modulated by an object comprising an array of pixels of length Δ and then passed through the FT lens, and then combined with a reference beam on a recording medium situated at a Fourier transform plane of the object with respect to the FT lens, the method further comprising:

• passing the object beam through a phase element effectively juxtaposed with the object and having a correlation length greater than the length Δ, such that illuminant intensity of the object beam is redistributed in the Fourier transform plane by spatial variations of phase delay in the phase element,
• wherein the phase element has the property that when the object beam is modulated by a random binary pattern:
• (i) there falls in the Fourier transform plane a redistributed intensity pattern having an intensity envelope and at least one principal direction;
• and
• (ii) said envelope remains at no less than 50% of its peak value from the center of said redistributed intensity pattern to a radius of 1.5×λF/Δ in any direction.