Abstract: An eyepiece lens system having a large amount of allowable eccentricity. This eyepiece system forms a magnified virtual image of an observation object, and the eyepiece system has a horizontal angle of view of 40 degrees or more. The maximum amount of eccentricity S that makes the proportion of the amount of change, ? mm, in tangential field curvature in the amount of eccentricity, S mm, between the optical axis Ax and an observer's eye satisfy Condition (1), namely, ?0.25<?/S<0, at all image heights is 3 mm or more.

Abstract: An optical disk apparatus driving an optical disk includes a tilt-angle adjusting unit configured to adjust a tilt angle indicating the tilt of an optical axis of laser light emitted from a pickup to detect an optimal tilt angle at which a traverse signal has the maximum amplitude and a storing unit configured to store information about the optimal tilt angle. When the optical disk has multiple recording layers on one side, the tilt-angle adjusting unit adjusts the tilt angle with respect to each of the multiple recording layers to detect the optimal tilt angle and the storing unit stores information about the optimal tilt angle with respect to each of the multiple recording layers. The tilt angle with respect to each of the multiple recording layers is controlled in accordance with the information about the optimal tilt angle with respect to each of the multiple recording layers.

Abstract: There is provided a playback device including an adjustment portion that, based on a first data recording surface among a plurality of data recording surfaces of an optical recording medium, adjusts tilt with respect to the first data recording surface, an adjustment amount measurement portion that measures a first tilt adjustment amount from a result of the tilt adjustment, an acquisition portion that acquires a coma aberration of the playback device, and a calculation portion that, based on the first tilt adjustment amount and the coma aberration, calculates a second tilt adjustment amount to adjust tilt with respect to a second data recording surface that is different to the first data recording surface.

Abstract: An optical disk apparatus driving an optical disk includes a tilt-angle adjusting unit configured to adjust a tilt angle indicating the tilt of an optical axis of laser light emitted from a pickup to detect an optimal tilt angle at which a traverse signal has the maximum amplitude and a storing unit configured to store information about the optimal tilt angle. When the optical disk has multiple recording layers on one side, the tilt-angle adjusting unit adjusts the tilt angle with respect to each of the multiple recording layers to detect the optimal tilt angle and the storing unit stores information about the optimal tilt angle with respect to each of the multiple recording layers. The tilt angle with respect to each of the multiple recording layers is controlled in accordance with the information about the optimal tilt angle with respect to each of the multiple recording layers.

Abstract: An optical pickup including a light source for radiating a light beam, a diffraction element for separating a light beam radiated from the light source into at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a four-segment first light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions arranged on both sides of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium, and a calculation unit for generating a first tracking signal based on respective outputs of the first light receiving portion and for generating a second tracking signal based on outputs of the second and third light receiving portions.

Abstract: An optical pickup including a light source for radiating a light beam, a diffraction element for separating a light beam radiated from the light source into at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a four-segment first light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions arranged on both sides of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium, and a calculation unit for generating a first tracking signal based on respective outputs of the first light receiving portion and for generating a second tracking signal based on outputs of the second and third light receiving portions.

Abstract: An optical pickup including a light source for radiating a light beam, a diffraction element for separating a light beam radiated from the light source into at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a four-segment first light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions arranged on both sides of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium, and a calculation unit for generating a first tracking signal based on respective outputs of the first light receiving portion and for generating a second tracking signal based on outputs of the second and third light receiving portions.

Abstract: A laser diode applies a laser beam through a grating, a beam splitter, and an objective to a compact disc. A laser beam reflected by the compact disc is applied through the objective and the beam splitter to a photodiode. The objective has a large numerical aperture of 0.6 in order to be able of play back a digital video disc that has a thin substrate and contains information recorded at a high density. To prevent the photodiode from suffering aberrations caused due to the large numerical aperture of the objective, the photodiode has a relatively small photodetector unit having a normalized detector size ranging from 3 .mu.m to 16 .mu.m, for detecting only returning light up to a numerical aperture of 0.3 and not detecting light of greater numerical aperture values.

Abstract: An objective lens having at least two regions of different numerical apertures is configured for focusing a light beam through the regions of the different numerical apertures on two different signal recording surfaces of at least two optical discs having light transmitting layers of different thicknesses. Since the objective lens is integrally formed by at least two lens portions, a light beam outgoing from a common light source is focused on signal recording surfaces of at least two optical discs having the light transmitting layers of different thicknesses.

Abstract: A disc reproducing apparatus such ah as video disc players and compact disc players, etc., surely corrects skew of an optical disc and reproduces recorded information even though the recording density is high. The disc reproducing apparatus has a plate-like transparent member interposed in a focused light path of the light beam so as to tilt the transparent member and cancel any comatic aberration. A light spot correction means having the transparent parallel flat plate and at least a coil and a magnet changing the inclination of the flat plate is arranged in a light path of a light beam, thus comatic aberration due to skew of the optical disc is surely and simply corrected.

Abstract: A laser diode applies a laser beam through a grating, a beam splitter, and an objective to a compact disc. A laser beam reflected by the compact disc is applied through the objective and the beam splitter to a photodiode. The objective has a large numerical aperture of 0.6 in order to be able of play back a digital video disc that has a thin substrate and contains information recorded at a high density. To prevent the photodiode from suffering aberrations caused due to the large numerical aperture of the objective, the photodiode has a relatively small photodetector unit having a normalized detector size ranging from 3 &mgr;m to 16 &mgr;m, for detecting only returning light up to a numerical aperture of 0.3 and not detecting light of greater numerical aperture values.