Abstract: An optical data storage system includes a laser which is focused on an optical disk by an objective lens. A tracking actuator and a focus actuator move the objective lens about a tracking axis and focus axis respectively. The tracking and focus actuators respond to signals provided by a focus and tracking detector. The focus and tracking detector is formed by four photodetectors which are electrically isolated from one another. The third and fourth photodetectors are disposed about the outer peripheries of the first and second photodetectors, respectively, about an axis. Each photodetector emits an electrical signal representative of the radiation detected thereon.

Abstract: A file management system for interfacing a host computer application or operating system to a write once read mostly optical data storage system. The file management system causes a predetermined number of sectors on the optical disk to be reserved for a directory region, and causes files of information data to be written to consecutive sectors of an information region adjacent the directory region. Directory data associated with the files of information data is then written to consecutive sectors in the directory region. The information region is thereby allowed to expand to any necessary size until directory data associated therewith fills the adjacent directory region. These procedures are then repeated, resulting in a plurality of interleaved directory and information regions on the optical disk. The file management system causes directory data to be organized in a tree structure. Each file of information data is associated with a subdirectory.

Abstract: An optical disk drive of the type adapted to use an optical disk cartridge formed by an optical disk mounted about a hub within an enclosure. When inserted into the optical disk drive, the cartridge is received and supported by a pan. A control handle for controlling the disk drive can be rotated between a load position, a run position, a spin-down position, and an eject position. The handle is coupled to the pan by a linkage. When the handle is rotated to either its run or spin-down positions, the linkage positions the pan at a run/spin-down position at which the hub of the disk is engaged with a drive spindle. When rotated to either its load or eject positions, the linkage causes the pan to be in a load/eject position at which the cartridge can be inserted into or removed from the pan. The position of the handle is detected by optical sensors which provide signals representative thereof to control circuitry.

Abstract: An objective lens velocity control system for use in an optical data storage system. The optical data storage system includes an optical disk with servo tracks for storing data, an objective lens, and a tracking drive for driving the objective lens along the tracking axis in response to tracking drive signals. The tracking error detector is responsive to the objective lens and produces tracking error signals representative of the position of the objective lens along the tacking axis. The tracking error signal also defines measurement periods which are representative of an actual velocity of the objective lens. A velocity control is responsive to the tracking error detector and produces the tracking drive signals in a form tending to cause the objective lens to have a desired velocity. For each measurement period, the tracking control produces a first tracking drive signal during a first portion but for no longer than a time duration which is a function of the desired velocity.

Abstract: A focus initialization system adapted for use with an optical data recording system. Focus initialization is performed while a tracking servo loop is in an open loop mode, and an objective lens is fixedly positioned along a tracking axis. With a focus servo system in an open loop mode, the objective lens is cyclically driven along a focus axis about a neutral position and between offset positions. Displacement of the offset positions from the neutral position is increased with each successive cycle. After the objective lens has been positioned at each peak offset position, the focus servo loop is closed and track crossings resultant from eccentricity of the servo tracks on the record carrier are counted. Focus capture is recognized when at least a predetermined number of track crossings are counted during a predetermined time period.

Abstract: A single beam direct read during write and write protect system for use in an optical data storage system. The optical data storage system includes a reflective-type optical disk, a laser for producing a beam of radiation to write data onto the optical disk during write operations, and a radiation detector for producing write detect signals representative of radiation detected from the optical disk during the write operations. A slope detector produces verification signals indicative of the accuracy of the write operations as a function of a slope of the peaks of the write detect signals. A digital counter is enabled by the verification signals, and produces a write error signal when a predetermined number of inaccurate write operations are detected.