An improved optical encoder uses an optical pick-up unit that provides for degrees of freedom in the tracking and focus axes that are unavailable in conventional optical encoders thereby improving the encoders' performance. In an embodiment the encoder employs an optical disc marked with pits and lands which may be arranged in a spiral pattern. The optical disc is mounted on the shaft whose motion is to be monitored by the optical encoder. The encoder may be arranged to read the markings on the optical disc using the three-beam pickup method.

An improved optical encoder uses an optical pick-up unit that provides for degrees of freedom in the tracking and focus axes that are unavailable in conventional optical encoders thereby improving the encoders' performance. In an embodiment the encoder employs an optical disc marked with pits and lands which may be arranged in a spiral pattern. The optical disc is mounted on the shaft whose motion is to be monitored by the optical encoder. The encoder may be arranged to read the markings on the optical disc using the three-beam pickup method.

An optical information recording apparatus and method thereof for recording information in a holographic medium. The apparatus includes a laser source which generates a reference beam and a signal beam to record the information in the holographic medium, a sensor which detects a vibrational amplitude over a time period applied to the optical information processing apparatus for recording the information, an operational circuit which calculates from the vibrational amplitude at least one statistical measure of the vibrational amplitude; and a processor programmed to control a recording mode such that the processor evaluates the calculated statistical measure to determine continuation of a recording operation to the holographic medium.

The optical information recording device includes a light source configured to emit a laser beam, an optical element configured to divide the laser beam into the reference beam and the signal beam, an angle control unit configured to control an angle of incidence of the reference beam on the optical information recording medium, and a phase control unit configured to control a phase of at least one of the signal beam and the reference beam in a recording period, wherein the angle control unit controls an angle interval so that a position of a 1st null of an adjacent page of the signal beam is fixed, and wherein the phase control unit controls the phase of the signal beam or the reference beam so that a phase difference between the adjacent pages is a predetermined value.

The optical information recording device includes a light source configured to emit a laser beam, an optical element configured to divide the laser beam into the reference beam and the signal beam, an angle control unit configured to control an angle of incidence of the reference beam on the optical information recording medium, and a phase control unit configured to control a phase of at least one of the signal beam and the reference beam in a recording period, wherein the angle control unit controls an angle interval so that a position of a 1st null of an adjacent page of the signal beam is fixed, and wherein the phase control unit controls the phase of the signal beam or the reference beam so that a phase difference between the adjacent pages is a predetermined value.

A two-dimensional interleaving method is provided. The two-dimensional interleaving method includes dividing a first page having N.sup.2N.sup.2 pixels, N being a natural number, into a plurality of blocks, wherein each of the plurality of blocks includes NN pixels, rearranging each of the plurality of the blocks of the first page into a second page, wherein each of two index located at same position in two adjacent block of the first page, respectively, is rearranged to have at least a dispersion distance D in the second page, and relocating an index pixel located at same position of each of the plurality of the blocks of the first page into a k-th block of the second page.

A two-dimensional interleaving method is provided. The two-dimensional interleaving method includes dividing a first page having N.sup.2N.sup.2 pixels, N being a natural number, into a plurality of blocks, wherein each of the plurality of blocks includes NN pixels, rearranging each of the plurality of the blocks of the first page into a second page, wherein each of two index located at same position in two adjacent block of the first page, respectively, is rearranged to have at least a dispersion distance D in the second page, and relocating an index pixel located at same position of each of the plurality of the blocks of the first page into a k-th block of the second page.