Abstract: An optical pickup apparatus comprises: a laser light source for emitting a laser beam; a collimating optical system, having a first optical axis and a predetermined unsatisfied degree of a Abbe's sine condition, for collimating the laser light beam; an objective lens, having a second optical axis, for focusing the laser beam from the collimating optical system on an information holding plane of an optical disc; a detection portion for detecting an amount and a direction of a tilt of the optical disc from a reference; and a control portion for changing the first optical axis with respect to the second optical axis in accordance with the detected amount and direction of the tilt. A lens system of the collimating optical system is made to have an unsatisfied Abbe's sine condition to a predetermined degree and the optical axis of the lens system is tilted or shifted to compensate the comma aberration developed due to the tilt of the optical disc.

Abstract: An optical disc-like recording medium has on one surface of its transparent substrate a ROM region where a plurality of pits are formed in correspondence with a predetermined information signal, and a RAM region where a plurality of guide grooves for tracking are formed and where an information signal is capable of being recorded. The optical disc-like recording medium transparent substrate is formed with a recording film made of an organic material and arranged to have a light-absorbing effect. Its refractive index is varied in response to illumination of laser light with a predetermined wavelength. Further formed on the recording film is a reflection film made of a metal which reflects light incident thereon. The physical depth of the pits is arranged to be equal to the physical depth of the guide grooves. The optical depths of the pit and guide groove have predetermined values which result from adjusting the thicknesses of the respective portions of the recording film present on the pit and guide groove.

Abstract: A reflective optical rotary encoder device detects an angular speed or position of a rotatable member with a light beam applied to and reflected from a reflective optical encoder disc. The reflective optical rotary encoder disc has an annular encoder track for reflecting the light beam, the encoder track being composed of an annular pattern of angularly spaced pit units each including a plurality of radially spaced arcuate pits, and a pit-free annular focus servo track for focusing the light beam onto the encoder track, the focus servo track extending along and being disposed radially substantially centrally in the annular encoder track.

Abstract: An optical detection system for detecting a displacement amount of a movement device with an optical encoder movable in accordance with a movement of the movable device has on a light-reflecting layer a plurality of pits successively strung in a predetermined direction. An optical pickup optically picks up the pit information by irradiating the optical encoder with light beams and receiving reflected light beams from the optical encoder. The optical pickup comprises a light-division device for dividing the light beam from a light-emitting device into three light beams so that the divided three light beams are directed to the pit string to apply three light spots to the pit string. The light-division device is adapted to be rotatable with respect to the optical encoder so that a light passing through the three light spots intersects the pit string at a predetermined angle.

Abstract: A recording disc comprises a substrate having a tracking servo groove of spiral or concentric pattern on one surface thereof. The servo groove has a constant depth and a variable width which varies to allow generation of a position indicating signal. An eraseable recording layer is deposited on the surface of the substrate to store information signals. The recording disc is fabricated by a method involving modulating the intensity of a laser beam with a permanently stored signal and directing it to the surface of a photoresist layer on a master blank placed on a rotating turntable. The beam penetrates the full thickness of the layer. The optically excited portion of the layer spreads in lateral directions by an amount proportional to the energy. The turntable is moved relative to the laser to expose a portion of the photoresist layer in spiral or concentric pattern to the directed beam. The exposed portion is then etched to form the tracking servo groove.

Abstract: A film thickness measuring apparatus comprises a light source for impinging light on a measuring plate with a predetermined incident angle .theta..sub.0, where the measuring plate comprises a transparent film on top of a transparent substrate and the transparent film has a film thickness which is to be measured by the film thickness measuring apparatus, a light receiving system for receiving and detecting light which is impinged on the measuring plate and is reflected thereby, and an analyzer system responsive to an output of the light receiving system for measuring an angle .DELTA. of the phase difference between two polarized light components of the reflected light from the measuring plate and for calculating the film thickness of the transparent film from the angle .DELTA. of the phase difference. The incident angle .theta..sub.0 of the light from the light source with respect to the measuring plate is selected equal to or approximately equal to a polarizing angle .theta..sub.

Abstract: A rotating analyzer type ellipsometer comprises a rotating analyzer for receiving light which is impinged on a sample with a predetermined incident angle and reflected by the sample, a rotary phase detecting apparatus provided so as to rotate unitarily with the rotating analyzer for generating a rotary phase signal as the rotary phase detecting apparatus rotates, a rotating mechanism for rotating the rotating analyzer and the rotary phase detecting apparatus, a photodetector for producing an output responsive to light which is passed through the rotating analyzer, and a computer for obtaining a phase difference between the rotating analyzer and the rotary phase detecting apparatus from a phase difference .phi..sub.o with which a difference between an output I.sub.p of the photodetector and a theoretical value I.sub.o becomes a minimum or substantially zero by entering into the computer the output I.sub.p of the photodetector and calculating the theoretical value I.sub.