Abstract: A prism-type objective lens is provided for use in the pickup head of an optical disc drive capable of driving two types of optical discs such as a CD and a DVD. The prism-type objective lens allows the pickup head to be made more compact in size with reduced structural complexity, and also allows the pickup head to read data from two different types of optical discs. The prism-type objective lens includes a prism having a cross section substantially in the shape of a right triangle, a front aspherical plano-convex lens, and a rear aspherical plano-convex lens, where the planar surface of each lens is attached to one or the other of the leg sides of the prism. The hypotenuse side of the prism can be formed with two aperture areas where different reflective layers are coated. Alternatively, the hypotenuse side of the prism can be formed with a reflective HOE layer that allows the laser beam incident on it and reflected from it to be diffracted into two beams which are focused at different points.

Abstract: A method for designing an optimal bi-axial type of magnetic gear system that uses magnetic coupling for transmitting torque in order to be free from the defects caused by using a conventional mechanical gear system. A non-coaxial rather than a conventional coaxial type of magnetic gear design is considered for this invention. For the non-coaxial magnetic gear system, the size of torque will depend on the number of poles magnetized out of the strong magnetic material around the magnetic gear. Therefore, the optimum number of magnetized poles must be carefully selected for a set of specified conditions such that the largest torque can be obtained. An optimal magnetic gear system can be produced by the method in this invention.

Abstract: A new type of stator design and arc shaping method that is used in a diametrically wound and diametrical air gap type of brushless motor. After arc shaping, the stator of this brushless motor has an external profile composed of a central arc and two modified arcs located on each side of the central arc. The central arc subtends an angle twice that of angle A and the modified arcs each has a radius r, both angle A and r are given by the following formulae: ##EQU1## Through arc shaping the stator, the cogging torque is lowered while a certain standard value for the torque constant is still maintained. Thus, the overall efficiency of the brushless motor is raised.

Abstract: A prism-type objective lens is provided for use in the pickup head of an optical disc drive capable of driving two types of optical discs such as a CD and a DVD. The prism-type objective lens allows the pickup head to be made more compact in size with reduced structural complexity, and also allows the pickup head to read data from two different types of optical discs. The prism-type objective lens includes a prism having a cross section substantially in the shape of a right triangle, a front aspherical plano-convex lens, and a rear aspherical plano-convex lens, where the planar surface of each lens is attached to one or the other of the leg sides of the prism. The hypotenuse side of the prism can be formed with two aperture areas where different reflective layers are coated. Alternatively, the hypotenuse side of the prism can be formed with a reflective HOE layer that allows the laser beam incident on it and reflected from it to be diffracted into two beams which are focused at different points.

Abstract: A cyanine dye for using in high density optical disc recording medium, having the following structure: ##STR1## wherein R represents 4-methoxycarbonyl benzyl group, X.sup.- represents an acid anion, and n represents an integer of 1 or 2. This cyanine dye is suitable for use as a .lambda.=450 nm.about.650 nm visible light-absorbing organic dye useful as a high density optical disc recording medium.

Abstract: A spindle motor for a disc drive, such as a CD-ROM drive, is provided. This spindle motor is a brushless motor of a single-phase axial-winding and radial-gap type including a stator, a rotor coupled to said stator, and a driving circuit for supplying a driving signal to the stator to rotate the rotor. The stator includes a pair of upper and bottom salient-pole pieces formed with a plurality of tooth-like portions serving as salient-poles. The peak surface of each tooth-like portion is formed into a symmetrical convex shape, which minimizes the cogging torque of the motor. Further, the use of a phase-adjuster in the driving circuit allows the motor to produce large output torque at high speeds. The output characteristics of this spindle motor meet the requirements of high speed CD-ROM drives.

Abstract: A cyanine dye for using in optical disc recording medium, having the following structure: ##STR1## wherein R represents 4-methoxycarbonyl benzyl group, X.sup.- represents an acid anion, and n represents am integer of 2 or 3. This cyanine dye is suitable for use as a near infrared light-absorbing organic dye useful as an optical disc recording medium.

Abstract: An apparatus for coating a magneto-optical recording medium film onto a disk substrate are provided. For proceeding the sputtering processes, a sputtering target containing Tb, Fe, and Co composition is prepared and placed in a sputtering gun which is served as a sputtering source. Facing to the sputtering gun, a clamping mechanism having a plurality of clampers arranged around the clamping mechanism is provided for clamping disk substrate thereon. During sputtering processes, the clamping mechanism is rotated about its axial center, and at the same time each clamper of the clamping mechanism is rotated about its axial center respectively. The clamper is designed in a form of facing the plane of the sputtering gun at a proper tilt angle, preferably 15 degrees, so that the disk substrate may be sputtered with a uniform thickness and composition of magneto-optical recording medium film thereon.

Abstract: A magnetizing apparatus capable of magnetizing a magnetic roller having a length up to 30 cm is provided. The magnetizing apparatus is comprised of at least two split members, each of which is provided with magnetic heads employed for applying magnetic fields to a magnetic roller. The end face of each magnetic head is shaped in agreement with the profile of the magnetic roller so that there would be no air gap formed between the magnetic head and the magnetic roller when they come into contact with each other. The split members are separated first and then combined to accommodate the magnetic roller within the magnetizing apparatus. After magnetization, a magnetic force is induced between the magnetic head and the magnetic roller such that an external force stronger than the magnetic force is used to pull the split members apart to fetch out the magnetic roller.

Abstract: A method and apparatus of dynamic heat treating the ferromagnetic amorphous alloys by applying AC current or pulsed high current on the alloys in the form of a ribbon are disclosed. The amorphous ribbon is continuously passed through a pair of electrodes from which AC current is conducted on the amorphous ribbon to perform a Joule heating. A DC magnetic field is applied on the amorphous ribbon preferably along a length direction thereof to improve the soft magnetic properties of the amorphous alloys. The DC magnetic field can be applied on either the section of the amorphous ribbon between the pair of electrodes or the section that has already been heat treated. With the method and apparatus, ferromagnetic amorphous alloys with improved magnetic properties such as greater magnetic induction, lower coercivity and low hysteresis loss are resulted and the annealing embrittlement is avoided.

Abstract: A method of improving the magnetic properties of a ferromagnetic materials is disclosed. The method comprises a step of providing a specimen made of Fe, Ni or Co based amorphous alloys in a magnetizing field and a second step of applying an AC current or pulsed current on the specimen to improve its soft magnetic properties. The applied AC current has a frequency of 50 to 50K Hz, a wave form of either sine wave, triangular wave or square wave, and a current density of 10 to 500 A/cm.sup.2. The magnetic properties of the ferromagnetic materials are improved by a coercivity ratio less than 0.5, a magnetic induction ratio greater than 1 and a core loss ratio less than 0.3.