Abstract: A reduced redundancy error correction and detection code is shown for memory organized with several bits of the data word on each chip. This package error correction and detection will correct all errors on any one chip and detect errors on more than one chip. A certain arrangement of an ECC matrix is first created for a symbol size code greater than the number of bits per chip. Thereafter certain columns of the matrix are removed to create the final code having a symbol size the same as the number of bits per chip. A specific example of an 80 bit code word is shown having 66 data bits and 14 check bits for a 4-bit-per-chip memory.

Abstract: A circuit means for detecting data errors in VLSI processing circuits at the earliest point such an error occurs in the processing stream or (in different modes) at any selected point therein, and for providing the prior operands and faulty (intermediate) output data together with an indication of what is wrong with the data. Described are registers and/or means for controlling the mode of the circuitry, error detection means (being, for example, parity check circuits), and an output means for providing the output in an organized way responsive to the controlling means and the output of the error detecton means. The method of using such a circuit is inherent in the disclosure.

Abstract: A two axis linear motor for carrying the objective lens for optical focusing and optical tracking in an optical recording system has a stationary structure for providing a magnetic field and a moving armature structure. The stationary structure may have two permanent magnets and several pole pieces to properly shape the field with respect to the armature. In one embodiment, a central elongated pole piece and two parallel adjacent elongated pole pieces which are associated with two permanent magnets to form flux gaps with the central pole piece. Flux returns to the magnets through a lower pole piece to which the central pole piece is attached. The central and lower pole pieces have an aperture through which the laser beam may pass on its way to and from the objective lens.

Abstract: A quarterwave retarder prism such as can be used in optical recording has a shape similar to a dove prism, and has three internal reflections, with the retarder prism designed to have the emerging light beam on the same axis or collinear with the entering light beam such that the accumulated phase retardation in the device is one quarterwave over a wide range of wavelengths of light.

Abstract: In an optical recording system for both reading and writing, the laser beam is projected to the media through a diffraction grating which generates a plus one and minus one order beam ahead of and behind the main zero order beam. The grating is driven by an oscillating driver so as to wobble in a fashion which leaves the zero order beam unaffected but causes the plus one and minus one order beams to move inwardly and outwardly, radially, with respect to the information track on the media in opposite fashions. The wobbling plus one and minus one order beams are used to generate differential signals from separate detectors and are passed through a band pass filter to generate a radial position error signal which may be used to drive the write/read head inwardly or outwardly to remain positioned over a particular information track.

Abstract: The voltage output of a differential amplifier is adjusted using an active feedback loop so that there is no direct current potential difference between the differential outputs of the differential amplifier. A potential difference at the differential output of a differential amplifier due to inherent bias or operating characteristics of the system is referred to as direct current offset voltage and the need to correct this condition may be referred to as differential output direct current offset voltage compensation. The feedback loop to accomplish this compensation consists of one or more stages of isolation and amplification driven by the output voltages of the differential amplifier and having a high input impedance to diminish loading of the amplifier outputs. A voltage peak detection system is used in order to isolate direct current voltage values from alternating current voltage values appearing at the differential amplifier output.

Abstract: In an optical recording system, a media disk for writing information has a plurality of information tracks with preformatted clock location indications written on the tracks. Writing is accomplished by making a written indication at a predetermined location between preformatted clock locations where the predetermined location is representative of the particular data to be written. Proper location of the preformatted clock location indicia on adjacent tracks provides for proper track crossing information when track addressing occurs as well as proper address location on particular tracks.