Abstract: An optical system for an optical head employed in an optical disc drive, which uses a plurality of kinds of optical discs having different thickness cover layers, is provided with a light source, an objective lens and a light receiving unit. A plurality of diverging light beams having different wavelengths are emitted from a plurality of light emitting points, respectively. One of the light emitting points is used depending on a thickness of a cover layer of a currently loaded optical disc. The objective lens is capable of converging each diverging beam on a data recording surface of the optical disc. The light receiving unit receives a beam reflected by the optical disc and generates electronic signals representing the recorded data. In this optical system, an image magnification M of the objective lens satisfies a condition: −0.144<M<−0.099.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: A recording and/or reproduction apparatus, for an information medium including a substrate having concave and convex portions and a plurality of recording layers, includes a light source for emitting a light beam; an optical system for diffracting the light beam emitted by the light source so as to output a first diffracted light beam and a plurality of second diffracted light beams; and a driving section for driving the optical system. The optical system outputs the first diffracted light beam and the second diffracted light beams, such that when one of the second diffracted light beams is converged to and reflected by one of the concave and convex portions, the first diffracted light beam is converged to one of the recording layers. The driving section drives the optical system, such that the one of the second diffracted light beams is converged to the one of the concave and convex portions.

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: An optical element comprises: a diffractive structure having a plurality of diffracting ring-shaped zones arranged around an optical axis on at least one optical surface; and an optical path difference giving structure arrranged on an optical surface of at least one of the plurality of diffracting ring-shaped zones, for giving a prescribed optical path difference to a prescribed light beam passing through the diffracting ring-shaped zone, wherein the optical surface of the diffractive structure is a structure having a diffracting function for setting L-th (L≠0) order diffracted light of the light beam having the first wavelength &lgr;1 to a maximum diffraction efficiency and for setting M-th (M≠0) order diffracted light of the light beam having the second wavelength &lgr;2 to a maximum diffraction efficiency in case of an assumption of no existence of the optical path difference giving structure.

Abstract: An optical pickup apparatus comprises first, second and third light sources to emit light fluxes of wavelength &lgr;1, &lgr;2 and &lgr;3 for conducting recording and/or reproducing information for first, second and third optical information recording mediums having respective protective substrates of thickness t1, t2 and t3 and a diffractive optical element located on a common optical path for the first, second and third light sources. A converged-light spot is formed on the first optical information recording medium with m-th order diffracted-light ray of the wavelength &lgr;1, on the second optical information recording medium with n-th order diffracted-light ray of the wavelength &lgr;2, and on the third optical information recording medium with k-th order diffracted-light ray of the wavelength &lgr;3 generated by the diffractive optical element respectively, wherein one of m, n and k is different from one of other two numbers.

Abstract: An optical system for an optical disc drive includes a light source, an objective lens and a collimator lens. The light source emits first and second light beams. The first light beam is for reproducing data from a digital versatile disc while the second light beam is for a compact disc. The objective lens is provided with a diffraction structure which is designed to focus the first light beam on a recording layer of the digital versatile disc and the second light beam on a recording layer of the compact disc. The collimator lens is disposed between the light source and the objective lens. The collimator lens adjusts the diverging/converging angle of the first and second light beams entering the objective lens. The change in spherical aberration of the first light beam caused by wavelength deviation from a design wavelength due to individual specificity of the light source is corrected by adjusting the diverging/converging angle of the first light beam emerging from the collimator lens.

Abstract: An optical pickup condenses a light emitted from a light source using an objective lens and irradiates the light on an optical recording medium to record data on the optical recording medium and/or to reproduce the data recorded on the optical recording medium. The optical pickup includes an optical element adjusting a convergence and/or a divergence of the light emitted from the light source and proceeded to the objective lens.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: An optical pickup apparatus for at least two kinds of optical information recording media, comprises a first light source; a second light source; an optical converging system; and a photo detector. An optical element of the optical converging system comprises a first region including an optical axis and a second region adjoining the first region and locating at the outside of the first region, the first region is a refractive surface and the second region is a diffractive surface. When a first light flux passes through the second region, the light amount of n-th order diffracted ray of the first light flux is larger than that of any other order diffracted ray of the first light flux, and when a second light flux passes through the second region of the optical element, the light amount of n-th order diffracted ray of the second light flux is larger than that of any other order diffracted ray of the second light flux, where n is an integer except 0.

Abstract: In an optical scanning device for scanning both a high-density, HD, record carrier (18) and a low-density, LD, record carrier (38), wherein a beam vergence-changing lens (34; 55) is arranged in the path of at least one of the LD (32) and HD beams (2) to adapt the vergence of the beam so that it has the required cross-section at the pupil of a conventional lens system (10, 14), this lens is made of plastics and has a focal length of between 6 and 9 mm. The temperature dependency of the scanning device is reduced thereby.

Abstract: An objective lens includes an aspherical lens facing a disk and having a predetermined first focal distance and a predetermined numerical aperture, and a holographic lens installed adjacent to the aspherical lens and having a second focal distance longer than that of the first focal distance and having a diffraction lattice to compensate for the chromatism due to a change in wavelength of laser light having a wavelength of 670 nm or less. Thus, during the shift between recoding and reproduction of a DVD or an HD-DVD, the change in wavelength due to the change in power of the laser light and chromatism according to the change can be effectively corrected. Also, since the objective lens is formed of one aspherical lens and one holographic lens, the material for each of the lenses can be easily selected and also the structure of the optical pickup using the objective lens according to the present invention can be simplified.

Abstract: An optical pickup apparatus for a first optical medium including a first transparent base plate having a thickness of t1 and a second optical medium including a second transparent base plate having a thickness of t2 (t2>t1), comprises a first light source to emit a first light flux having a wavelength of &lgr;1; a second light source to emit a second light flux having a wavelength of &lgr;2 (&lgr;1<&lgr;2); a converging optical system having an objective lens and a diffracting section and to converge the first light flux or the second light flux onto the first optical medium or the second optical medium; and an optical detector. When the converging optical system converges the second light flux onto the second information recording surface so as to conduct reproducing and/or recording the information of the second optical information recording medium, a spherical aberration has at least one discontinuous portion or at least one substantially discontinuous portion.

Abstract: An optical pickup includes a semiconductor laser for emitting light at a wavelength &lgr;1 and a semiconductor laser for emitting light at a different wavelength &lgr;2 from the wavelength &lgr;1. The light at the wavelength &lgr;1 transmitted through an objective lens forms a light-collecting spot on an optical disk to record/reproduce information thereon. The light at the wavelength &lgr;2 transmitted through the objective lens forms a light-collecting spot on an optical disk to record/reproduce information thereon, the two optical disks having different substrate thicknesses. Between the semiconductor laser and the objective lens is there provided a combination-type diffractive element fabricated by combining two raw materials having different refractive index behaviors in relation to wavelength at a combining plane shaped as a grating.

Abstract: An optical disc apparatus includes a fixed portion having a light source portion and a movable portion that holds an objective lens and moves along a radial direction of an optical disc. The fixed portion includes the light source portion for selectively emitting short and long wavelength laser beams, and a collimator lens for collimating the laser beams. The objective lens includes a positive refractive lens and a diffractive lens structure formed on a surface of the refractive lens. The diffractive lens structure has wavelength dependence such that spherical aberration varies in the undercorrected direction as wavelength of incident light increases. The objective lens converges the short wavelength laser beam of a predetermined diffraction order onto an informatlon layer of a thin cover type optical disc, and converges the long wavelength laser beam of the identical diffraction order onto an information layer of a thick cover type optical disc.

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 &lgr;1) and a DVD with a base thickness of about 0.6 mm for a red light beam (wavelength &lgr;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 optical reproducing apparatus that uses a hologram laser module and is applicable to a DVD Multi drive, wherein five sub spots of light in total that are most suitable to perform the differential push-pull tracking both for DVD-RAM and for DVD-R/RW are irradiated on the disk, respectively, and influence of several sub spots that are unnecessary in recording and reproducing a disk is canceled out by calculation, to realize an optical head that is compatible with the DVD Multi drive using a hologram laser module, and thereby providing a small-size, high-performance optical reproducing apparatus.

Abstract: An optical pickup apparatus compatible with at least two types of optical recording media, using light beams having respective different wavelengths for recording and reading information, the optical pickup apparatus including two laser light sources to emit light beams having the different wavelengths, a holographic lens including a holographic ring to transmit the light beams incident in an inner region of the holographic ring, and to diffract a specific light beam among the light beams emitted from the laser light sources incident in an outer region relative to the inner region, an objective lens to focus the light beams passed through the holographic ring lens on the respective information recording surfaces of the two types of the optical recording media, optical elements to alter optical paths of the light beams reflected from the information recording surfaces of the optical recording media to corresponding photodetectors.

Abstract: An objective lens for an optical pickup is configured such that, when a light beam having a wavelength corresponding to the optical disc requiring the higher NA is converged on the optical disc requiring the higher NA at the higher NA, the phase of light flux passed through the peripheral area is substantially the same as that passed through the central area. When a light beam having a wavelength corresponding to the optical disc requiring the lower NA is converged on the optical disc requiring the lower NA at the lower NA, the phase of light flux passed through a first annular region included in the peripheral area is different from that passed through the central area, and the phase of light flux passed through a second annular region, which is outside the first region, is substantially the same as that passed through the central area.

Abstract: An optical pickup apparatus having compatibility with a recodable compact disk (CD-R) and a digital video disk (DVD), which uses a wavelength of one of a first light beam and a second light beam according to the recording medium to be used. In the optical pickup apparatus, laser light sources emit a first light beam having a relatively shorter wavelength for the DVD and a second light beam having a longer wavelength for the CD-R, respectively. An objective lens has a predetermined focal length in accordance with the position of an information recording surface in the DVD. An optical path control unit controls the path of light beams so that the light beam emitted from one of the laser light sources is directed to the objective lens and the light output from the objective lens is directed to the optical detection unit.

Abstract: A recording reproducing optical system for an optical information recording medium is provided with a light source; an objective lens; and an aberration correcting optical element provided on an optical path between the light source and the objective lens. The objective lens includes an aspherical surface and one diffractive surface on which a diffractive structure structured by a plurality of concentric ring-shaped zonal steps is formed and the objective lens is a plastic lens structured in one element in one group. The aberration correcting optical element comprises at least one plastic lens on which a diffractive structure structured by a plurality of concentric ring-shaped zonal steps is formed. The following formulas are satisfied: PD1>0 (PD1 is a diffractive power (mm−1)), PD2<0 (PD2 is a diffractive power (mm−1)) and PR2>0 (PR2 is a refractive power (mm−1) as a refractive lens).

Abstract: An optical pick-up apparatus has a first light source, a second light source, and an optical system including an objective lens. An optical functional surface of the objective lens is divided into at least first and second concentric optical functional regions. The second functional region is provided with a diffractive structure to correct a spherical aberration of a converged light spot on an information recording plane to be regulated in a range where reproduction and/or recording information for a first optical information recording medium can be conducted when the refractive index of the optical element and the wavelength of the first light source vary due to a change of the working temperature of the optical system.

Abstract: A hybrid objective lens has a refractive lens and a diffractive optical element constructed by plural coaxial ring-shaped zones on at least one optical surface thereof.

Abstract: A diffraction optical element is configured such that a plurality of annular zones having minute steps extending in a direction of the optical axis therebetween are formed on a base element. The plurality of annular zones include narrow and wide zones respectively satisfying conditions (1) and (2): &Dgr;Z(i)<(1/2)·&Dgr;E(i)  (1), and &Dgr;Z(i)>(3/2)·&Dgr;E(i)  (2), wherein, i represents the order of the steps counted from the optical axis, &Dgr;E(i) represents an absolute value of an OPD provided by the i-th step, and &Dgr;Z(i) represents an absolute value of a difference between OPDs provided, with respect to a base curve, by an inner side end portion and outer side end portion of an annular zone between an i-th step and (i+1)-th step.

Abstract: Disclosed is such an optical pickup controlling an aberration even if optical axes of an objective lens and another optical system are shifted from each other.

Abstract: An optical disk device has an aperture of an objective lens in an incoming path of a beam from a semiconductor laser to an optical disk formed larger than an aperture in a return path from the optical disk or an aperture is varied in recording and in reproduction. This configuration improves recording/reproducing ability since light is focused on an optical disk with high numerical aperture. In addition, since reflected light from the optical disk is detected with low numerical aperture, margins for tilt and defocus are not reduced. Furthermore, since unnecessary signal components contained in the reflected light can be eliminated, a S/N (signal-to-noise ratio) of an information signal also increases. Thus, a high-performance optical disk device can be obtained. Alternatively, by varying the aperture of an objective lens in recording and in reproduction, an optical disk device in which recording density and recording quality are increased without deteriorating reproduction quality can be obtained.

Abstract: An optical pickup apparatus conducts recording or reproducing information for an information recording plane of a first or second optical information recording medium and comprises a first light source and a second light source mounted on a same base board; a converging optical system; and a coupling lens. The converging optical system comprises an objective lens to converge a first or second light flux having passed through the coupling lens on a first or second optical information recording medium; and a diffractive structure to change a focal length in accordance with a wavelength of a light flux emitted from the first light source or the second light source.

Abstract: An optical head device that converges first and second laser beams having different wavelengths on recording surfaces of first and second optical recording media through a single light converging optical system including an objective lens for recording or reproducing data on the recording surfaces. A refracting surface of the objective lens is divided into two regions, i.e., a central refracting surface region with an optical axis thereof being as a center and an outer circumferential refracting surface region that surrounds an outer circumference of the central refracting surface region. A diffraction grating is formed generally entirely over the central refracting surface region. When recording or reproducing data on the first optical recording medium using the first laser beam, a beam spot is formed with a diffracted beam obtained by the central refracting surface region.

Abstract: The present invention relates to an optical device with a variable numerical aperture (NA), which utilizes special optical properties of a liquid crystal medium. Through the design of external electrodes and a circuit control unit, the refraction index of the liquid crystal medium can be modulated by the external voltage so that the beam passing through the LCD produces diffraction. An optical device with a variable focal point is thus formed by combining this LC diffractive device and an objective lens. So the present invention provides an optical device with focal points of different numerical apertures by varying the external voltage, whereby the device can read optical disks of all specifications.

Abstract: An optical head device includes a focusing optical system for focusing a laser beam emitted from a semiconductor laser light source on an optical information medium with an objective lens. A chromatic aberration correction element for correcting chromatic aberration occurring in the objective lens is provided between the semiconductor laser light source and the optical information medium. A light distribution correction element in which the transmittance increases with the distance from the center of the aperture surface of the objective lens is provided so as to correct a reduction of the intensity of the light incident on the aperture surface of the objective lens with the distance from the center of the aperture surface.

Abstract: It is to provide an objective lens for being provided in an optical pickup device for carrying out at least one of a record of information on at least two types of optical information storing media and a reproduction of information from the optical information storing media. In the optical pickup device comprising the first and second light sources, a third-order spherical aberration component of the wavefront aberration caused in a first region that a numerical aperture on the side of the optical information storing medium is not more than NA2 which is required for the record/reproduction, is over. When the standard deviation value of an absolute value thereof is WSA2rms·&lgr;2, the inequality 0.015≦WSA2rms≦0.06 is satisfied. The light transmitted in the second region that a numerical aperture on the side of the optical information storing medium is over NA2, becomes a flare light.

Abstract: An objective lens comprises at least inner and outer optically functional regions arranged in a direction perpendicular to an optical axis and each of the inner and outer optically functional regions has a diffractive structure. The objective lens comprises a light amount reducing structure to reduce an amount of the light flux passing through a region of the objective lens other than the inner optically functional region when recording or reproducing is conducted for CD.

Abstract: Disclosed is an objective optical system for an optical pick-up that converges a light beam whose wavelength is shorter than F-line onto an information layer of an optical disc. The objective optical system consists of a refractive lens on which the diffractive lens structure is formed and satisfies the following condition (1); 1/(&ngr;3×&lgr;×10−6)<0.0045  (1) where &ngr; is an Abbe number and &lgr; is a working wavelength (unit: nm). At least one surface of the refractive lens is formed as an aspherical surface whose radius of curvature increases as a height from the optical axis becomes large. The diffractive lens structure has a plurality of concentric ring-shaped steps to correct chromatic aberration caused by the refractive lens.

Abstract: An optical recording and pickup head having a flat plate lens of a staircase type diffraction grating structure is compatible with a DVD and a CD-RW.

Abstract: A read head optical system capable of reading either CD or DVD disks is provided. A monolithic molded hollow plastic block includes three lenses integrally molded into its exterior surfaces. A 780 nm laser diode is aligned with the first lens for reading CD disks, a 655 nm laser is aligned with the second lens for reading DVD disks and a detector for providing signal, focus and tracking data is aligned with the third molded lens. The hollow plastic block has an interior cavity adapted to support optical elements to receive and transmit the output of the laser diodes to the disks and to the detector. The three lenses are formed in the hollow plastic block in various embodiments.

Abstract: The present invention relates to an optical pickup apparatus enabling to reproduce/record data of different kinds of disks in different thicknesses, using one single optical pickup. The optical pickup apparatus includes two objective lens, in which one objective lens has an incident plane and an outgoing plant formed of a flat plane at a designated radius domain from an optical axis, thereby preventing spherical aberration caused by the difference of the thickness between different kinds of disks.

Abstract: Light emitted from a semiconductor laser is separated by a diffractive optical element into a main beam, first sub beams, and second sub beams. The distribution of the intensity of each of the first sub beams is the same as the distribution of the intensity of the main beam. The distribution of the intensity of each of the second sub beams is different from the distribution of the intensity of the main beam. The sum of the focusing error signals relating to the main beam and the first sub beams is a final focusing error signal. The difference between the tracking error signal relating to the main beam and the tracking error signal of each of the first sub beam is a final tracking error signal. The deviation of the thickness of the substrate of the disk and the radial tilt thereof are detected on the basis of the deviation of the zero crossing points of the focusing error signal and the tracking error signal relating to the main beam and each of the second sub beams.

Abstract: Disclosed is an objective lens of an optical pick-up that converges light beams of two different wavelengths onto recording layers of optical discs of two different recording densities, respectively. The objective lens includes a refractive lens whose one surface is divided into a common area through which a light beam of a low NA, which is necessary and sufficient for an optical disc having low recording density, passes and a high NA exclusive area through which a light beam of a high NA, which is necessary only for an optical disc having high recording density, passes. A diffractive lens structure is formed in both the areas. The diffractive lens structure in the common area maximizes the diffraction efficiency of the first order and that in the high NA exclusive area maximizes the diffraction efficiency of the second or third order at the wavelength corresponding to the optical disc having high recording density.

Abstract: An objective lens of an optical pickup apparatus converges a divergent light flux onto an information recording surface.

Abstract: An optical recording and pickup head having a flat plate lens of a staircase type diffraction grating structure is compatible with a DVD and a CD-RW.

Abstract: A device for reading and/or writing a record carrier (13), the device comprising converging means (35, 45, 47, 106, 108) for focusing a radiation beam (27, 101) originating from a radiation source (25) on the record carrier (13). The converging means comprises polarization means (103) and a diffraction grating (107) of birefringent material. Dependent on the direction of polarization, the radiation beam (101) is focused on one of two possible surfaces corresponding to DVD and DVR, respectively. A diffraction grating (107) is present in a central area of the radiation beam (101) and causes diffraction of a first order for one direction of polarization of the radiation beam (101) and diffraction of a second, higher, order for a second direction of polarization of the radiation beam (101). The diffraction grating (107) is made of birefringent material.

Abstract: A beam irradiation apparatus includes a beam generation source (41) for generating at least either of an optical beam, an electron beam and an ion beam, and a focusing lens (48) for focusing a beam emitted from the beam generation source (41). The beam irradiation apparatus includes at least first and second focus control mechanisms (71) and (72) each controlling a focus position of the beam with respect to the same lens system forming the focusing lens, so as to focus the beam onto an irradiation object (40) by using the focusing lens (48), whereby it possible to obtain a minute beam spot and to conduct a reliable, and stable focus control.

Abstract: An objective lens comprises a single objective lens adapted to a finite system having first and second aspherical surfaces and a hologram is formed on at least one of said aspherical surfaces. The light of the positive 1st order or that of the negative 1st order of the hologram is subjected to optimal correction of spherical aberration under actual operating conditions. When a semiconductor laser is used as light source, the change in the spherical aberration caused by the change in the refractive index arising as a result of the change in the environmental temperature of the medium between the first surface and the second surface is substantially offset by the change in the spherical aberration of the hologram attributable to the change in the oscillation wavelength of the semiconductor laser of the light source caused by the change in the environmental temperature so that, if the objective lens has a numerical aperture greater than 0.

Abstract: A high-density focusing objective lens having a high numerical aperture (NA), which can be easily manufactured by an existing technique, and an optical pickup using the objective lens for high-density recording.

Abstract: An optical system for an optical head of an optical disc drive is capable of using first and second discs, protective layer of the second disc being thicker than that of the first disc, a data density of the second disc being lower than that of the first disc. A light source selectively emits first and second laser beams having first and second wavelengths, respectively. An objective lens converges the first and second beams on the first and second discs, respectively. The second beam is incident on the objective lens as diverging light, and the first beam is incident on the objective lens as a beam of which degree of divergence is smaller. A diffraction lens structure is formed in the high NA exclusive area, which compensates for aberrations of a portion of the first laser beam, and causes aberrations to a portion of the second laser beam passed therethrough.

Abstract: The invention provides a pickup head used in an optical data storage system. The pickup head contains a diffractive optical element (DOE) stack on a semiconductor substrate. The DOE stack includes multiple diffractive lenses for providing several diffractive surfaces and a middle layer serving as a beamsplitter and servo-generating element for a light reflected from an optical storage medium. The middle layer is sandwiched by the diffractive lenses that are located on both outer parts of the DOE stack. The semiconductor substrate includes at least a laser source and several photodetectors. The middle layer serving its function preferably includes a polarization-selective DOE and a quarter-wave retarder oriented to rotate a polarization state of the laser source, so that only the light reflected from the optical storage medium is diffracted by the polarization-selective DOE.

Abstract: An optical pickup includes a light source for emitting more than two light beams whose wavelengths are different from each other, and an objective lens including a first lens and a second lens. The first lens is a lens for collecting each light beam onto a recording medium. The second lens is a lens for compensating chromatic aberration in the light beams. The second lens is placed on the first lens in contact and is located across the optical path of each light beam. The absolute value of the difference between the Abbe number of the first lens and the Abbe number of the second lens is greater than 10.

Abstract: An optical pickup apparatus for reproducing information from one of different kinds of optical information recording medium, each having a transparent substrate in different thickness, or for recording information onto one of the different kinds of optical information recording medium, the optical pickup apparatus includes: a light source for emitting light flux; a converging optical system having an optical axis, a ring-zonal diffraction section, and a refracting surface including a first divisional portion, a second divisional portion and a third divisional portion. The third divisional portion is farther from the optical axis than the first divisional portion, and the second divisional portion is provided between the first divisional portion and the third divisional portion.

Abstract: An optical pickup apparatus compatible with at least two types of optical recording media, using light beams having respective different wavelengths for recording and reading information, the optical pickup apparatus including two laser light sources to emit light beams having the different wavelengths, a holographic lens including a holographic ring to transmit the light beams incident in an inner region of the holographic ring, and to diffract a specific light beam among the light beams emitted from the laser light sources incident in an outer region relative to the inner region, an objective lens to focus the light beams passed through the holographic ring lens on the respective information recording surfaces of the two types of the optical recording media, optical elements to alter optical paths of the light beams reflected from the information recording surfaces of the optical recording media to corresponding photodetectors.