Abstract: A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t1 with a laser beam having a wavelength ?1 and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t2 with a laser beam having a wavelength ?2. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t3 with a laser beam having a wavelength ?3.

Abstract: A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t1 with a laser beam having a wavelength ?1 and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t2 with a laser beam having a wavelength ?2. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t3 with a laser beam having a wavelength ?3.

Abstract: A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t1 with a laser beam having a wavelength ?1 and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t2 with a laser beam having a wavelength ?2. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t3 with a laser beam having a wavelength ?3.

Abstract: An objective lens optical system includes a light beam splitting element and an objective lens and is configured to focus a light beam with a wavelength ? on an information recording surface of a first optical recording medium as a dual/double layer disc having a transparent substrate with a thickness t1 and to focus a light beam with a wavelength ? on an information recording surface of a second optical recording medium as a dual/double layer disc having a transparent substrate with a thickness t2 (t1<t2). The light beam splitting element is sectioned into regions that are designed to focus a light beams on an information recording surface of either one of the first optical recording medium and the second optical recording medium. Either one region has a negative or positive power so that a light focus position of a light beam having passed through the first region by the objective lens and a light focus position of a light beam having passed through the second region by the objective lens are different.

Abstract: An objective lens optical system focuses a light beam with a wavelength ?1 on an information recording surface of a first optical recording medium including a transparent substrate with a thickness t1, a light beam with the wavelength ?1 on an information recording surface of a second optical recording medium including a transparent substrate with a thickness t2, and a light beam with a wavelength ?3 on an information recording surface of a third optical recording medium including a transparent substrate with a thickness t3, by using a refraction action. Sectioning the area of the objective lens optical system is applied to a compatible technique for the same wavelengths, and generating an aberration for canceling a chromatic aberration caused by a difference in wavelength ? of the light beam is applied to a compatible technique for different wavelengths.

Abstract: There is provided an optical pickup system which includes a first light source emitting first light having a wavelength ?1, a second light source emitting second light having a wavelength ?2 longer than the wavelength ?1, a third light source emitting third light having a wavelength ?3 longer than the wavelength ?2, and an objective lens focusing the first light on an information recording surface of a first optical recording medium, focusing the second light on an information recording surface of a second optical recording medium, and focusing the third light on an information recording surface of a third optical recording medium. In the optical pickup system, at least one lens surface of the objective lens is divided into a plurality of concentric sections with an optical axis, having a step at each boundary between the sections, each of the sections has a different aspherical shape and m1>m2>0 and ?0.060?m3??0.

Abstract: An information-recording medium of write once or rewritable type designed to have narrow tracks is provided, in which the wobble signal amplitude is scarcely fluctuated by crosstalk. The medium includes recording tracks formed in a spiral form and meandering at a predetermined wobble cycle T, and a plurality of zones constituting each of the recording tracks, each of the zones having a principal area formed to have a predetermined wobble phase. A relationship of T>80b holds between the wobble cycle T and a channel bit length b of recording data. The wobble phase of one of the recording tracks is adjusted so that an average phase difference d is d>?/2 between the wobble phase in the principal area in the zone and a wobble phase of an area in the recording track disposed adjacently on an inner circumferential side or an outer circumferential side of the principal area, in relation to all of the recording tracks disposed adjacently in the radial direction.

Abstract: A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t1 with a laser beam having a wavelength ?1 and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t2 with a laser beam having a wavelength ?2. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t3 with a laser beam having a wavelength ?3.