Abstract: An optical head of a type useable in a optical disk reader/writer is provided. One of the optical elements is provided in a fashion that one or more optical parameters or characteristics of the system are invariant, regardless of whether the one optical element is used, or not. In one embodiment the optical element is a beamshaper. In order to provide the desired invariant property, the surfaces of the optical element are preferably formed with high accuracy. One manner of economically achieving high accuracy is to measure errors or imperfections in a first formed, preferably etched, surface and adjust the shape or position of a second aligned etched surface so as to at least partially compensate for the errors or imperfections.

Abstract: A method and system are presented for use in recording/reading data from an array of data units within a three-dimensional storage medium. Exciting radiation is provided in the form of first and second light beams of first and second different wavelengths, respectively. The first and second light beams are concurrently directed and focusing onto desirably distanced from each other sites in the medium and excited light of a third wavelength coming from the excited site is collected to form and excited light beam to be directed towards a detector assembly, while correcting for chromatic and spherical aberrations of the light focusing and collection.

Abstract: A system for recording and reading out holograms in a storage medium including a pattern encoder, a first fourier transform lens with a focal length f1, a second fourier transform lens with a focal length f2, a detector array, and a first and second prism. The first prism is located between the pattern encoder and the first fourier transform lens, wherein the optical length between the pattern encoder and the first fourier transform lens through the first prism is equal to a back focal length BFL1. The second prism located between the second fourier transform lens f2 and the detector array, wherein the optical path length between the second fourier transform lens and the detector array through the second prism is equal to a back focal length BFL2.

Abstract: A method of recording holograms includes: generating a first signal-beam from a signal-beam source and a first reference beam from a reference-beam source; recording a first hologram in a holographic medium from an interference between the first signal beam and the first reference beam; shifting the reference-beam source after the act of recording the first hologram; generating a second signal beam from the signal-beam source and a second reference beam from the reference-beam source after the act of shifting the reference-beam source following the recording of the first hologram; and recording a second hologram in the holographic medium from an interference between the second signal beam and the second reference beam.

Abstract: A system for recording and reading out holograms in a storage medium comprising a pattern encoder, a first fourier transform lens with a focal length f1, a second fourier transform lens with a focal length f2, a detector array, and a first and second prism. The first prism is located between the pattern encoder and the first fourier transform lens, wherein the optical length between the pattern encoder and the first fourier transform lens through the first prism is equal to a back focal length BFL1. The second prism located between the second fourier transform lens f2 and the detector array, wherein the optical path length between the second fourier transform lens and the detector array through the second prism is equal to a back focal length BFL2.

Abstract: A method of recording holograms includes: generating a first signal beam from a signal-beam source and a first reference beam from a reference-beam source; recording a first hologram in a holographic medium from an interference between the first signal beam and the first reference beam; shifting the reference-beam source after the act of recording the first hologram; generating a second signal beam from the signal-beam source and a second reference beam from the reference-beam source after the act of shifting the reference-beam source following the recording of the first hologram; and recording a second hologram in the holographic medium from an interference between the second signal beam and the second reference beam.

Abstract: An optical head of a type useable in a optical disk reader/writer is provided. One of the optical elements is provided in a fashion that one or more optical parameters or characteristics of the system are invariant, regardless of whether the one optical element is used, or not. In one embodiment the optical element is a beamshaper. In order to provide the desired invariant property, the surfaces of the optical element are preferably formed with high accuracy. One manner of economically achieving high accuracy is to measure errors or imperfections in a first formed, preferably etched, surface and adjust the shape or position of a second aligned etched surface so as to at least partially compensate for the errors or imperfections.