Abstract: An optical disk apparatus includes: an optical pickup unit for reading out information recorded on an optical disk; a demodulation circuit for demodulating digital data from an output signal of the optical pickup unit; and a controller for performing a servo control based on the output signal of the optical pickup unit. When performing a focus/tracking control in a recess and a protrusion of a guide groove of the optical disk, the controller obtains a focus control gain difference between the recess and the protrusion by comparing focus offsets with respect to variations in amplitudes of signals from the optical disk for the recess and the protrusion, respectively.

Abstract: An optical disk apparatus including: a light source; an objective lens for converging light emitted from the light source toward an optical disk; a first photodetection device for detecting reflected light from the optical disk and outputting a first signal; a signal processing section for receiving the first signal and generating a signal containing information recorded on the optical disk; a second photodetection device for detecting a portion of the light emitted from the light source and outputting a second signal; a light source driving section for receiving the second signal, and based on the second signal, driving the light source so that output power of the light source equals a target value; and an amplitude fluctuation detection section for detecting an amplitude fluctuation amount of the second signal, and if the amplitude fluctuation amount exceeds a predetermined value, changing driving characteristics of the light source driving section.

Abstract: An optical pickup device, a signal processing method for the optical pickup device, and an optical disk drive unit are provided which are capable of eliminating or lessening the influence on the RF signal by a variation in the emission power of a laser, without changing the structure of the laser or varying reproduction power. A signal processing circuit 19 of an optical pickup device 2, which converges light emitted from a laser 11 upon an optical disk through an objective lens and executes recording and reproduction of information on the optical disk, comprises: a photo-detector 18 which receives reflected light from the optical disk; a former-light detector 17 which receives a part of emitted light from the laser 11; a division circuit 22 which divides an RF signal outputted from the photo-detector 18 by a former-light signal outputted from the former-light detector 17; and an RF detection circuit 23 which detects an RF signal from the signal obtained by a division of the division circuit 22.

Abstract: An optical pickup has a light source that emits a light beam having a far field pattern being elliptical in cross section; a collimator lens that converts the light beam from the light source into a substantially parallel light beam; a beam shaping element that performs beam shaping by changing a substantial aspect ratio of the far field pattern of the light beam from the collimator lens; light condensing means of condensing the light beam shaped by the beam shaping element on an optical information recording medium; and light detecting means of detecting a light beam reflected at the optical information recording medium. wherein the beam shaping element makes the cross section of the light beam having been shaped close to a circle by compressing the light beam substantially in a direction of a major axis of the elliptical cross section of the far field pattern, and reflects the light beam from the collimator lens to the light condensing means.

Abstract: An optical pickup has

Abstract: In an optical recording and reproducing apparatus, two light sources such as a laser diode of different wavelengths from each other are provided, and photosensors receive the light emitted by the light sources and reflected by the optical recording medium. Before recording or reproduction is started, the type of optical recording medium having a different wavelength dependent reflectance is discriminated. Because two wavelengths are used, the difference of the outputs is large, and the type of the optical recording medium is discriminated reliably according to the outputs of the photosensors. Then, the operation of the apparatus is stabilized according to the type of the optical recording medium by optimizing the laser power, the gain of the controller, the revolution number of the medium or the like.

Abstract: An improved drafting instrument is provided and consists of a base board and a slide member. The instrument is so constructed that various geometrical figures, such as squares, rectangles, right-angled isosceles triangles and regular triangles, are accurately drafted in the various dimensions between a minimum and maximum dimension without using conventional frame rules. The base board is provided with one or more openings, and guide rails along which the slide member is slid and positioned for drawing. By displacing the slide member along one of the guide rails and positioning against the guide rail, a figure having a desired dimension is formed and drafted.