Abstract: Shape-wise thicknesses of a cover layer and first through (N?1)th intermediate layers of an optical recording medium having refractive indexes nr1, nr2 are converted into thicknesses t1, t2 of the respective layers having a predetermined refractive index which makes a divergent amount equal to a divergent amount of a light beam resulting from the thicknesses tr1, tr2, a difference DFF between the sum of a thickness “ti” through a thickness “tj”, and the sum of a thickness “tk” through a thickness “tm” is set to 1 ?m or more (where i, j, k, and m are each any positive integer satisfying i?j<k?m?N), and the thicknesses t1, t2 are calculated by products of a function f(n) expressed by the following formula (1), and the thicknesses tr1, tr2: f(n)=?1.088n3+6.1027n2?12.042n+9.1007??(1) in the formula (1), n=nr1, nr2, . . . , and nrN.

Abstract: In an optical head device which performs recording/reading of data in/from a high-density optical disc using an objective lens with a large NA, a saw-tooth shape diffraction element is used for also performing recording/reading of data in/from a conventional optical disc, such as DVD, CD, or the like. A step difference that produces an optical path length for blue light which is equal to or longer than the wavelength of the blue light and optical path lengths for red and infrared light which are shorter than the wavelengths of the red and infrared light is utilized so as to exert an inverse action on the blue light to those exerted on the red and infrared light. The effect of increasing the working distances for CD and DVD enables multiple compatibility. The optical element is integrally combined with the objective lens to perform a tracking servo following operation.

Abstract: An objective lens, an optical head, an optical disk apparatus and an information processing apparatus which can suppress deterioration of a focal spot caused by a drop in the diffraction efficiency. Inner and outer circumference areas converge a laser beam, out of laser beams having a wavelength ?1 which are diffracted by the inner and outer circumference areas, on a first information recording medium; the inner circumference area and a mid-circumference area converge a laser beam, out of the laser beams having a wavelength ?2 which are diffracted by the inner circumference area and the mid-circumference area, on a second information recording medium; and the diffraction efficiency of the laser beam having the wavelength ?2 is greater than the diffraction efficiency of the laser beam having the wavelength ?1.

Abstract: An optical recording medium having three or more information recording layers reduces crosstalk caused by multi-reflected beams and improves signal quality. In the optical recording medium having three or more information recording layers, the refractive index of a plurality of intermediate layers disposed between adjacent information recording layers is greater than the refractive index of a cover layer disposed between a light incident surface and an information recording layer being the closest from the light incident surface.

Abstract: An information recording medium includes a first information recording layer and a second information recording layer. The first information recording layer is formed at a laser beam entrance surface, and is configured so that information can be recorded thereupon and/or reproduced therefrom using a first objective lens having a numerical aperture NA1 and laser beam of a wavelength ?1. The second information recording layer is formed so as to have a distance to the laser beam entrance surface of 0.05 mm to 1.2 mm and is configured so that information can be recorded thereupon and/or reproduced therefrom using a second objective lens having a numerical aperture NA2 and laser beam of a wavelength ?2. When a diffraction limit ?2, determined by numerical aperture NA2 and wavelength ?2, is taken as ?2=0.61×?2/NA2, a track pitch Tp1 of a track formed on the first information recording layer is Tp1<?2.

Abstract: An objective lens element having excellent compatibility with optical discs having different base material thicknesses is provided. The objective lens element has optically functional surfaces on an incident side and an exit side. At least either one of the optically functional surfaces on the incident side and the exit side includes a diffraction portion which satisfies at least either one of the following formulas (1) and (2): ?1×?2<0 (“×” represents multiplication)??(1), (sin ?2)/?22=?(sin ?1)/?1??(2), where ?1 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength ?1, and ?2 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength ?2.

Abstract: A disclosed objective lens includes: a lens having an entrance surface and an emission surface; and an anti-reflection coat formed on the emission surface, wherein a transmittance T1—0 [%] of the anti-reflection coat when an incident angle of a first laser beam having a first wavelength ?1 (390 nm??1?430 nm) is 0°, and the transmittance T1—40 [%] of the anti-reflection coat when the incident angle of the first laser beam is 40° satisfy 0.95?T1—0/T1—40?1.05, and a transmittance T2—0 [%] of the anti-reflection coat when an incident angle of a second laser beam having a second wavelength ?2 (630 nm??2?680 nm) is 0° and a transmittance T2—40 [%] of the anti-reflection coat when the incident angle of the second laser beam is 40° satisfy 0.85?T2—0/T2—40?0.97.

Abstract: When information is recorded or reproduced on or from an optical information medium having three or more recording layers using blue light, interference by another layer light is reduced and, when information is reproduced from an optical information medium using red light, an S/N ratio is held excellently high.

Abstract: An optical head, an optical disc device and an information processing device are capable of suppressing the amount of third-order astigmatism created upon recording or reproducing information on or from a multi-layer optical disc including at least three information recording surfaces. An objective lens satisfies a relationship of tc>(t0+tn)/2 assuming that t0 denotes the thickness of a light transmitting layer from the outer surface of the multi-layer optical disc to an information recording surface having the largest light transmitting layer thickness, tn denotes the thickness of a light transmitting layer from the outer surface of the multi-layer optical disc to an information recording surface having the smallest light transmitting layer thickness and tc denotes the thickness of a virtual light transmitting layer at which the absolute value of a third-order spherical aberration is minimum when blue-violet laser light is incident as parallel light on the objective lens.

Abstract: The present invention provides an objective lens, an optical head apparatus, an optical information apparatus, and an information processing apparatus that improve focal position detection accuracy. In order to reproduce information from an optical disk (28), an objective lens (25) collects a diffracted ray (15X) having a longer focal length, out of two diffracted rays (15X, 15Y), on an information recording surface (28L) via a base (28S) of the optical disk (28), and a distance (DF3) between the focal positions of the two diffracted rays (15X, 15Y) when the diffracted ray (15X) having a longer focal length is collected on the information recording surface (28S) is longer than double the distance (WD2) between the surface (25A) of the objective lens (25) and the surface (28A) of the base (28S) along the optical axis.

Abstract: An optical disc type is determined by detecting focus error signals and an amount of returned light, while (i) emitting light having a wavelength maximizing a focal length and (ii) moving an objective lens in a direction of an optical axis. If an S shape and AS immediately after a surface are greater than those at the surface, the optical disc is determined to have a largest capacity. It is also determined whether there is a reflective layer at a depth equal or less than 0.1 mm, if not, then it is determined whether there is a reflective layer at a depth of 0.6 mm. If there is a reflective layer at the depth of 0.6 mm, then the type of the reflective layer is determined based on TE/RF signals, using blue light. If the blue light is not adaptable, red light is emitted to replay at a depth of 0.6 mm.

Abstract: An optical recording medium and an optical information device that improve the quality of a servo signal and a reproduction signal. In the optical recording medium, when shape-wise thicknesses tr1, tr2, tr3, and tr4 of a cover layer (42), a first intermediate layer (43), a second intermediate layer (44), and a third intermediate layer (45) are respectively converted into thicknesses t1, t2, t3, and t4 of the respective corresponding layers each having a predetermined refractive index “no”, a defocus amount with respect to a layer having a refractive index nr? and a thickness tr? (satisfying: 1???n (where ? is a positive integer and n is an integer of 4 or more)), and a defocus amount with respect to a layer having the refractive index “no” and a thickness t? (satisfying: 1???n (where ? is a positive integer and n is an integer of 4 or more)) are equal to each other.

Abstract: An optical disk driving apparatus includes an optical head device having a laser light source, a converging optical system converging a light beam emitted by the laser light source onto an optical disk, a photo detector receiving reflected light reflected by the optical disk, and an aberration correcting optical system controlling aberration of the converging optical system; a motor rotating the optical disk; and a control section receiving a signal from the photo detector, wherein the converging optical system has an objective lens formed using resin as a main material, the aberration correcting optical system has a spherical aberration correcting element correcting spherical aberration, and the control section evaluates quality of a reproduction signal for information in the optical disk by using the reflected light received by the photo detector, and utilizes a result of the evaluation to perform closed loop control on the spherical aberration correcting element.

Abstract: An optical pickup device preventing damage or performance degradation of a second optical system. The optical pickup device includes first laser light source emitting a first light beam having a first wavelength, a first optical system guiding the first light beam emitted from the first laser light source to a first optical disc. Further, the optical pickup device includes a DVD integration unit emitting a second light beam having a second wavelength different from the first wavelength, a second optical system guiding the second light beam emitted from the DVD integration unit to a second optical disc different from the first optical disc, and a filter disposed at a position blocking incident light, of an unwanted light beam having the first wavelength and derived from the first optical system, from entering into the second optical system, so as to block the first light beam having the first wavelength.

Abstract: A lens surface (22) of an objective lens (20) includes an optical surface (221) formed of a plurality of annular optical surfaces (22a, 22b, 22c, and 22d) which include an approximately stair-shaped cross section and which are annularly partitioned centered around an optical axis (OA) of the objective lens (20), and a plurality of connecting surfaces (251) that connect the plurality of mutually adjacent annular optical surfaces to each other. The plurality of connecting surfaces (251) include cylindrical connecting surfaces (25b and 25c) formed of a cylindrical surface centered around the optical axis (OA) and a conical connecting surface (26a) formed of a conical surface centered around the optical axis (OA), and the conical connecting surface (26a) connects the annular optical surface (22c) and the annular optical surface (22d).

Abstract: In an optical head device which performs recording/reading of data in/from a high-density optical disc using an objective lens with a large NA, a saw-tooth shape diffraction element is used for also performing recording/reading of data in/from a conventional optical disc, such as DVD, CD, or the like. A step difference that produces an optical path length for blue light which is equal to or longer than the wavelength of the blue light and optical path lengths for red and infrared light which are shorter than the wavelengths of the red and infrared light is utilized so as to exert an inverse action on the blue light to those exerted on the red and infrared light. The effect of increasing the working distances for CD and DVD enables multiple compatibility. The optical element is integrally combined with the objective lens to perform a tracking servo following operation.

Abstract: A complex objective lens composed of a hologram and an objective lens, capable of realizing stable and high-precision compatible reproducing/recording of a BD with a base thickness of about 0.1 mm for a blue light beam (wavelength ?1) and a DVD with a base thickness of about 0.6 mm for a red light beam (wavelength ?2). In an inner circumferential portion of the hologram, a grating is formed, which has a cross-sectional shape including as one period a step of heights in the order of 0 time, twice, once, and three times a unit level difference that gives a difference in optical path of about one wavelength with respect to a blue light beam, from an outer peripheral side to an optical axis side. The hologram transmits a blue light beam as 0th-order diffracted light without diffracting it, and disperses a red light beam passing through an inner circumferential portion as +1st-order diffracted light and allows it to be condensed by an objective lens.

Abstract: An objective lens unit according to the present invention includes a first objective lens 41; and a first lens holder 2 for supporting the first objective lens 41. The first lens holder 2 is formed of a material which transmits ultraviolet. Preferably, the first lens holder 2 includes a through-hole, having first and second openings 2a and 2b, through which light incident on the first objective lens 41 passes, and an opening limiting section 3 provided along a circumferential direction of the through-hole and projecting toward a central axis of the through-hole. The first objective lens 41 is supported so as to block the first opening 2b. The opening limiting section 3 guides light incident thereon from the second opening 2a in a direction away from an optical axis of the first objective lens.

Abstract: A compound objective lens, an optical head device, an optical information device, and an information processing device that can inhibit the occurrence of aberration even when a light beam source wavelength shifts from the designed value. A diffraction structure having a sawtooth or stepwise cross section is formed in the region (R10) and region (R20). The height of the sawtooth or stepwise cross section formed in the region (R10) provides a light beam, which has a predetermined wavelength, with a difference in optical path length of N times the predetermined wavelength, as compared with a case of propagation in air. The height of the sawtooth or stepwise cross section formed in the region (R20) provides the light beam, which has the predetermined wavelength, with a difference in optical path length of J times the predetermined wavelength, as compared with a case of propagation in air.

Abstract: In an optical head device responding to optical disc of different track pitches, an effect of both obtaining the tracking error signal by the optimum DPP method using a single diffractive element and suppressing the lowering amount in the amplitude of the tracking error signal in a state the object lens is moved by track following is obtained. In the optical head device, the grating phase of left and right regions of a sub-beam generating diffractive element differ from each other by 180 degrees. A central region of the sub-beam generating diffractive element has a grating pattern different from the left and right regions, and is divided into a plurality of regions to form different gratings different from each other.