Abstract: Provided is a read signal offset during write verify which prevents the false detection of amorphous pips from an optical disk recorder. Amorphous pips are the signals caused by the drop in reflection from an optical disk after the laser has caused the surface material to change from its crystalline state to an amorphous state, but not to a hole. When a hole is not formed in the material, the amorphous material later recrystallizes, the drop in reflection no longer occurs and information is lost.

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: This invention relates to the field of radiant energy information storage devices and provides for a low reading level, an intermediate level and a high writing level of power from the radiation source so as to lower the overall power requirements of the radiation source and increase availability and accuracy of the verification read directly after or during writing, without causing unwanted damage to the information recording media. A circuit is described to accomplish this. The circuit basically employs two power sources, one for reading power, one for writing power and an intermediate ("Pedestal") circuit to employ a portion of the writing power source's power to provide the step-up in power to the intermediate level.

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.

Abstract: Disclosed is an apparatus for detection of write protect data written on an optical disk by simultaneously reading the data during writing using differential detection and disabling further writing if write protect data is present. The write protect data is the same format as other data written on the optical disk and is written as the first byte of data on all data fields. The data is written in a fixed-block format defining a symbol having a predetermined number of symbol positions and a predetermined number of holes which may be written at the symbol positions, an equal number of holes at odd and at even positions. The write protect symbol has holes written at symbol position numbers two and five. During the writing of a write protect symbol, the laser is operated at read power before it is operated at write power and a signal associated with the hole associated power of the reflected beam is sampled at position number eight of the previous symbol and at position number one of the write protect symbol.

Abstract: A circuit is shown for rapidly enabling and disabling a high current laser diode through a coaxial cable responsive to a data signal received at the circuit input. At the circuit input are two switching transistors, one or the other of which is forward biased while its counterpart is reverse biased, depending upon the level of the incoming data signal. The output of one of the switching transistors is fed to the base inputs of two emitter follower transistors, one PNP and the other NPN. The emitter terminals of the follower transistors are connected to the gate terminal of an enhancement mode VMOS field effect transistor. When the VMOS FET is enabled, current flows in the laser diode to energize it. The voltage level at the input to the follower transistors determines the voltage to the gate input of the FET. When the incoming data signal is low, the gate-to-source potential difference is near zero, thus preventing the FET from conducting current.