摘要:
A compatible optical pickup for recording and/or reproducing information on/from multiple kinds of optical discs having different thicknesses by selectively using source lights of respective different wavelengths corresponding to a kind of disc and using a common objective lens. At least one phase compensator, which compensates a phase of a light having a particular wavelength to correct for spherical aberration due to a thickness difference between the kinds of optical discs and/or chromatic aberration due to a wavelength difference between the required source lights, is positioned between the source lights and an entrance pupil of the objective lens. Each phase compensator compensates light of at least one wavelength and passes light of at least one other wavelength without significant relative phase alteration. By using two phase compensators, the optical pickup may be made compatible with at least three kinds of optical discs.
摘要:
A method of detecting a reproduction signal from an optical disc. A light beam reflected from a recording surface of an optical disc is divided into a central light beam portion and outer light beam portions in a direction corresponding to a radial direction of the optical disc. The central light beam portion and outer light beam portions are detected and a first detection signal from the central light beam portion and a second detection signal from at least one of the outer light beam portions are output. The amplitude of at least one of the first and second detection signals is adjusted and the reproduction signal is detected by subtraction between the first detection and second detection signals so that where reproduction is carried out on an optical disc having a varying track width the reproduction signal is improved.
摘要:
An optical recording medium having groove tracks and land tracks, first wobbles formed along both sidewalls of each of the groove tracks, second wobbles formed along both sidewalls of each of the land tracks and which are independent of the formation of the first wobble. A middle portion is formed at a predetermined position on each of the sidewalls between adjacent pairs of the land and groove tracks. This optical recording medium can significantly reduce the non-recordable area as compared to conventional optical recording media, resulting in a great improvement in recording density.
摘要:
A compatible optical pickup includes an optical disc, an objective lens, a diffractive device, and a divergent lens. The optical unit emits a short wavelength light beam corresponding to a high density optical disc and a long wavelength light beam corresponding to a low density optical disc. The objective lens forms a light spot on the high density optical disc and the low density optical disc and the diffractive device diffracts the short wavelength light beam to correct chromatism according to a change in a wavelength of the short wavelength light beam. The divergent lens refracts the long wavelength light beam toward the objective lens to increase a working distance with respect to the low density optical disc.
摘要:
A compatible optical pickup compatibly using a high density recording medium and at least one low density recording medium, includes an objective lens to form a light spot suitable for use on a recording surface of the high density recording medium by focusing a corresponding incident light beam with a high NA suitable for the high density recording medium and a light spot suitable for use on another recording surface of the low density recording medium by focusing another corresponding incident light beam, and an actuator provided to apply tilt to the objective lens. The light beam for the low density recording medium is incident on the objective lens as a divergent beam. When the objective lens is shifted in a radial direction, a tilt is applied to the objective lens corresponding to the shift.
摘要:
An optical disc apparatus and a wobble signal detection method in which a light beam projected onto an optical disc and reflected by the optical disc is divided into at least four light regions in the direction corresponding to the radial direction of the optical disc to detect the light regions, and a wobble signal is detected by performing a subtraction on first and second difference signals, the first difference signal obtained by performing a subtraction on detection signals for the inner light regions of the divided and/or detected light beam and the second difference signal obtained by performing a subtraction on detection signals for the outer light regions of the divided and/or detected light beam. Accordingly, when a wobble signal is reproduced from an optical disc manufactured by a wobble modulation manner, a wobble signal is prevented from being degraded due to the interference (cross talk) from the wobbles of adjacent tracks, even though the track pitch of the optical disc is reduced to improve the recording density.
摘要:
An optical pickup having a plurality of objective lenses. At least one of the plurality of objective lenses is configured so that a type of wavefront error mainly generated by a tilt of the at least one of the plurality of objective lenses is the same as a type of a wavefront error mainly generated by an angle at which light is incident upon the at least one of the plurality of objective lenses.
摘要:
A spherical aberration compensator for compensating for spherical aberration resulting from a thickness deviation of a recording medium. The spherical aberration compensator includes a central compensation which provides a phase distribution that is effective for compensating for spherical aberration resulting from the thickness deviation and a peripheral compensation portion which surrounds the central compensation portion and provides a phase distribution that is effective for reducing a worsening of the spherical aberration caused by axial displacement of an objective lens from the central compensation portion. The spherical aberration compensator effectively relieves an optical pickup having an objective lens of an NA of 0.7 or greater of worsening of the spherical aberration resulting from thickness deviation of the recording medium.
摘要:
A land/groove discriminating method and an optical recording and/or reproducing apparatus employing the method are provided. The land/groove discriminating method emits a light beam onto an optical disc having lands and grooves through an optical element capable of causing and varying an effect of thickness variation of the optical disc, detects a light beam reflected/diffracted from the optical disc by dividing the reflected/diffracted light beam into inner and outer light beam portions, and discriminates between a land and a groove of the optical disc by detecting variation in a difference signal between detection signals from the inner and outer light beam portions while varying the degree of the effect of thickness variation of the optical disc by driving the optical element.
摘要:
An optical pickup actuator having: a moving part on which an objective lens to focus an incident beam onto an optical recording medium is mounted, a magnetic driver that drives the moving part in track and focus directions of the optical recording medium, and a support element that movably supports the moving part and has a first support portion with a first predetermined stiffness and a second support portion with a second predetermined stiffness different from the first predetermined stiffness. A center of gravity of the moving part, a center of support of the support element, and a center of a force determined by arrangement of the magnetic driver are coincident.