Abstract: A compatible optical pickup device includes a single light source to emit a light having a wavelength longer than 650 nm, an objective lens having a near axis area, a ring type annular lens area, and a far axis area to focus the light to form light spots suitable for a first relatively thin optical disk and a second relatively thick optical disk to form a first light spot having an FWHM (full width at half maximum) of 0.72 ?m or less for the first optical disk and a second light spot having an FWHM of 0.8 ?m or more for the second optical disk, an optical path changer to change a proceeding path of incident light, and a photodetector to receive light reflected by the optical disk and having passed through the objective lens and the optical path changer and to detect an information signal and/or an error signal.

Abstract: A compatible optical pickup device includes a single light source to emit a light having a wavelength longer than 650 nm, an objective lens having a near axis area, a ring type annular lens area, and a far axis area to focus the light to form light spots suitable for a first relatively thin optical disk and a second relatively thick optical disk to form a first light spot having an FWHM (full width at half maximum) of 0.72 &mgr;m or less for the first optical disk and a second light spot having an FWHM of 0.8 &mgr;m or more for the second optical disk, an optical path changer to change a proceeding path of incident light, and a photodetector to receive light reflected by the optical disk and having passed through the objective lens and the optical path changer and to detect an information signal and/or an error signal.

Abstract: A video tape playback device in which heads are tracking-controlled according to a predetermined tracking control value, in order to accomplish automatic tracking so that noise is not regenerated on the screen during an abnormal speed playback.

Abstract: A mode discriminating device for an image signal processing system for discriminating between various operating modes of the image signal processing system. The mode discriminating device includes a microcomputer, a cam switch having a connecting element, and a voltage divider having an output terminal coupled to an input of the microcomputer. The voltage divider is composed of impedance elements and connecting taps, and is arranged at a position opposed to the connecting element. The connecting element makes simultaneous contact with the one of connecting taps and the output terminal according to the rotation of the cam switch. The output terminal supplies a corresponding voltage to the microcomputer which, by comparing the output voltage to reference data, discriminates between various operating modes of the system.

Abstract: A method for setting tracking data of variable speed modes in a video tape recorder having an automatic tracking circuit includes the steps of detecting current tracking data at a normal speed reproducing mode after performing an automatic tracking, and then determining a tracking data variation value by subtracting initial tracking data at a normal speed reproducing mode from the current tracking data, and setting a data variation function depending on the tracking data variation value, corresponding to an other speed reproducing mode, and detecting initial tracking data at said other speed reproducing mode and adding the data variation function to the initial tracking at said other speed reproducing mode, to transmit current tracking data at said other speed reproducing mode to a servo motor.