Abstract: Methods and systems for measuring and/or inspecting a characteristic of an optical article are provided. In one example, a method includes illuminating an optical article with a focused beam of light, detecting the light with a sensor after interacting with the optical article, determining a deflection angle of the beam of light, and determining a characteristic of the optical article based on the deflection angle. In one example, a system includes a light source, an optical element, and a sensor. The optical element focuses light from the light source to a reference location, the sensor detects the light from the reference location and generates signals associated with the intensity and position of the light received. A processor may receive the signals from the sensor and thereby determine a deflection angle of the light from the probe path.

Abstract: In one aspect of the present invention, a device for sensing an absolute position of an encoded object, comprising: a position tracking module comprising: a track illumination module configured to illuminate the encoded object with one more light beams, and to detect one or more light beams resulting from said illumination of said encoded object; and an absolute position determinator configured to determine the absolute position of the encoded object based on said one or more light beams resulting from said illumination of said encoded object.

Abstract: A method of determining coordinates for a storage medium includes: determining diffraction data from a plurality of diffraction patterns corresponding to diffractive markers of the medium; and combining the diffraction data to determine composite coordinates for the medium. The composite coordinates may include three translational coordinates and three rotational coordinates. The act of determining diffraction data may include shining a plurality of beams on a selection of the diffractive markers, and measuring the corresponding diffraction patterns in one or more photodetectors to determine the diffraction data. In this latter case the photodetectors may be segmented. The act of combining the diffraction data to determine composite coordinates may include solving a matrix system that couples the diffraction data and the composite coordinates. Each diffractive marker may include a pit. The storage medium may include a holographic storage medium.

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 method of writing holograms includes: numbering sections in sequence, where each section has a spatial projection onto a holographic medium; and writing at least one hologram in each of the sections in sequence. Writing in two sections with adjacent spatial projections provides a substantially uniform exposure level for a sequentially subsequent section with a spatial projection that overlaps the two sections.

Abstract: A method of determining coordinates for a storage medium includes: determining diffraction data from a plurality of diffraction patterns corresponding to diffractive markers of the medium; and combining the diffraction data to determine composite coordinates for the medium. The composite coordinates may include three translational coordinates and three rotational coordinates. The act of determining diffraction data may include shining a plurality of beams on a selection of the diffractive markers, and measuring the corresponding diffraction patterns in one or more photodetectors to determine the diffraction data. In this latter case the photodetectors may be segmented. The act of combining the diffraction data to determine composite coordinates may include solving a matrix system that couples the diffraction data and the composite coordinates. Each diffractive marker may include a pit. The storage medium may include a holographic storage medium.

Abstract: A holographic storage apparatus is provided which comprise: a photorecording medium layer which includes a first side and a second side and which encompasses a plurality of volume holographic storage regions; a plurality of first surface structures disposed on the first side of the photorecording medium layer, respective first surface structures including respective first and second facets that upstand from the first side of the photorecording medium; and a corresponding plurality of second surface structures disposed on the second side of the photorecording medium layer, respective second surface structures including respective third facets that respectively upstand from the second side of the photorecording medium layer parallel to respective first facets of corresponding respective first surface structures; wherein each respective volume holographic storage region is disposed between a respective first surface structure and a respective corresponding second surface structure.

Abstract: A method of holographic recording includes: generating a first object beam and a first reference beam; using a first prism at a first surface of a holographic medium to adjust an external entry angle of the first object beam into the holographic medium; and using the first prism to adjust an external entry angle of the first reference beam into the holographic medium. An interference between the first object beam and the first reference beam records a first hologram in the holographic medium.

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 method of writing holograms includes: numbering sections in sequence, where each section has a spatial projection onto a holographic medium; and writing at least one hologram in each of the sections in sequence. Writing in two sections with adjacent spatial projections provides a substantially uniform exposure level for a sequentially subsequent section with a spatial projection that overlaps the two sections.

Abstract: A buried servo signal on tape is modulated to provide information. According to the modulation, each of a plurality of sets of cycles has at least a selected cycle modulated to represent at least two modulation values. The modulation of the selected cycles of a group of sets of cycles provides a string of modulation values. The modulation values formed identifiers of longitudinal physical location on tape or other tape identifying information (e.g., number of frames per track and cartridge type code).

Abstract: Method and apparatus are provided for re-recording of a frame on magnetic tape (22) when a first recording of the frame is determined to be defective. A frame whose first recording is defective is re-recorded at a spare or reserved location on the tape. The reserved location is dedicated to re-recording of frames, and otherwise cannot have data stored therein. The tape contains a defect map frame (326) which is used to pair physical locations of defective frames with the reserved location whereat the frame is re-recorded. In one embodiment, the reserved location whereat a frame is re-recorded is a reserved physical frame on the same track in which the defective frame is recorded. In another embodiment, the reserved location is on a reserved portion of a track (TG39R) which is not the original track (TG39) upon which the frame is recorded. For embodiments having multi-channel or multi-track frames, the reserved location employs a corresponding plurality of tracks.

Abstract: In serpentine recording on magnetic tape (32), a warning marker (CEW) is generated and recorded on tape in a write mode and is read in a read mode. The warning marker indicates that a head is approaching a boundary position on the tape at which the head must change tracks in order to continue recording or reading frames. The warning marker is preferably included in an auxiliary portion of at least some frames. In one embodiment, the warning marker has a value related to a number of frames that can yet be recorded on the track before the boundary position is encountered. Monitoring of the warning marker serves to apprise the drive of a potential need to cache data in anticipation of a change of track. Caching of data can occur either by sending a caching signal to the host, or can occur internally in the drive without taxing the drive's buffer. In the drive-internal caching, the relative speed between the tape and the head is adjusted in anticipation of the head being repositioned for a change of track.

Abstract: A magnetic tape drive dynamically adjusts a transport rate of tape (32) in accordance with a host data rate. The host data rate is assessed in relation to a data fill level of a buffer (116). A controller (130) of the drive compares the data fill level of the buffer with a buffer normalization value and generates an adjustment value for adjusting a signal indicative of the desired linear velocity of the tape. In one embodiment, the controller also dynamically changes the buffer normalization value to reflect e.g., historical performance of the host. In another embodiment the controller adjusts the transport rate when a head (100) is within a predetermined distance of a boundary point whereat the head must change tracks.

Abstract: A method of positioning the read/write head onto a desired data track in a multi-track recorder/player utilizes a plurality of registration stripes to find the central axis of a data track. In one embodiment, each registration stripe has associated with it a recorded identification pattern or tone which may be sensed and used for identification purposes. Then, based upon the read amplitude output of the read head, the appropriate edge of a registration stripe may be detected and, from there, the read/write head moved directly onto the desired data track without any subsequent open-loop movement. In an alternative embodiment, multiple edges are sensed and used in a calculation to determine the lateral displacement associated with the longitudinal centerline of a desired data track.

Abstract: In a multi-track magnetic tape recorder/player of the type used for data storage and retrieval, with at least one read head and one write head, both being displaceable laterally relative to the direction of tape travel, and a memory to store values representative of those lateral displacements with respect to a reference position, a method for exact positioning of the read head onto previously written data tracks. In the preferred method, the write head is used to record (or erase) a longitudinal stripe along the tape, and the read head is used to find one or more edges of the stripe relative to a reference position. The displacements used to write the stripes and the displacements associated with the edges are compared to generate an offset correction factor used for subsequent head positioning.