Abstract: A multilayer optical element comprises a plurality of layers arranged along an optical axis, each layer having a plurality of nanostructures, wherein a size of—, and a spacing between—, the nanostructures is selected to provide a resonant response to an optical field at different wavelengths for different layers.

Abstract: [Object] To provide (i) a two-lens optical system, (ii) a beam combining module, (iii) a projector, and (iv) a method for assembling a two-lens optical system each of which allows for an improved lens positioning sensitivity [Means to Attain the Object] A two-lens optical system (100) includes a first lens (1) for use in collimation adjustment, the first lens being configured to move along only an optical axis of light emitted from a light source; and a second lens (2) for use in beam steering, the second lens being configured to move along only two axes perpendicular to the optical axis.

Abstract: An optical disk reproducing device includes a division element that divides a reflected light reflected and diffracted by an optical disk into a light flux in a central region and light fluxes in end regions; a photodetector that has a central light receiver that receives the light flux in the central region and at least two end light receivers that receive the light fluxes in the end regions, and outputs a light amount signal corresponding to a light amount of each of the received light fluxes; a non-linear processor that receives each of the light amount signals from the central light receiver and the end light receivers, and outputs linear signals and non-linear signals obtained by processing the light amount signals by linear and non-linear arithmetic operations; an equalization processor that receives the linear signals and the non-linear signals and outputs signals each amplified with a predetermined gain; an adder that adds the amplified signals and outputs an equalization signal; a reproduction signal

Abstract: A recording head has a near-field transducer proximate a media-facing surface of the recording head. The near-field transducer extends a first distance away from the media-facing surface. A waveguide overlaps and delivers light to the near-field transducer. Two subwavelength focusing mirrors are at an end of the waveguide proximate the media-facing surface and extend a second distance away from the media-facing surface that is less than the first distance. The subwavelength mirrors are on opposite crosstrack sides of the near-field transducer and separated from each other by a crosstrack gap. The subwavelength focusing mirrors each include a first material at the media-facing surface; and a second material facing away from the media facing surface and in contact with the first material. The second material includes a plasmonic material, and the first material is more mechanically robust than the second material.

Abstract: A pulse width controller for a thermal processing system is disclosed. Pulsed electromagnetic radiation is directed through a rotatable wave plate to a polarizing beam splitter, which reflects and transmits according to the phase angle of the wave plate. Radiation transmitted by the polarizing beam splitter is directed into an optical circuit that returns the radiation to the polarizing beam splitter after a transit time. A second rotatable wave plate is positioned in the optical circuit. The polarizing beam splitter reflects and transmits the returned radiation according to the phase angle of the second rotatable wave plate. A second pulse width controller may be nested in the optical circuit, and any number of pulse width controllers may be nested.

Abstract: An image pickup module includes a frame, two or more than two image pickup devices including electric circuit board and plural affixing gel layers. The frame includes two or more than two image pickup openings, and each of the image pickup devices is disposed in one of the image pickup openings. Each of the image pickup devices is adhered to an inner edge of one of the image pickup openings through one of the affixing gel layers, so as to affix the image pickup devices to the frame. A manufacture method of an image pickup module is also provided.

Abstract: Described herein are catheters for use with Optical Coherence Tomography (OCT) that include an optical fiber core having a first refractive index and an interface medium having a second refractive index, where the first and second refractive indexes are mismatched such that receiving electronics configured to receive optical radiation reflected from the reference interface and the target operate in a total noise range that is within 5dB of the shot noise limit. These OCT catheters may include a silicon die mirror having a reflective coating that is embedded in the interface medium. The optical fiber can be fixed at just the distal end of the catheter, and may be managed within a handle that is attached to the proximal end of the catheter body, and is configured to allow rotation of both the catheter body and the optical fiber relative to the handle.

Abstract: According to an embodiment, a recording/reproducing apparatus includes a diffraction grating and a light-receiving element. The diffraction grating divides return light from the guide layer in accordance with areas. The areas include a first area and a second area that does not overlap the first area. The light-receiving element includes (i) a first detecting cell group which receives a zero-order beam to which astigmatism is imparted, (ii) a second detecting cell group which receives at least one of a positive and negative first-order beam, which passes the first area and made astigmatic, and (iii) a third detecting cell group which receives at least one of a positive and negative first-order beam, which passes the second area and made astigmatic.

Abstract: An ultra-broadband photonic integrated circuit platform that combines at least two types of waveguides that each transmit in different, but overlapping, spectral bands on a single chip. By combining the multiple waveguides, the bandwidth of the platform can be extended beyond the bandwidth of either waveguide alone. In an exemplary embodiment, an ultra-broadband photonic integrated circuit includes a nitride-on-insulator (NOI) waveguide configured to transmit optical beams in a first spectral band and a silicon-on-nitride-on-insulator (SONOI) waveguide configured to transmit optical beams in a second band, where the same material serves as the core material in the NOI waveguide and as the cladding material in the SONOI waveguide. In some embodiments, light-emitting devices are bonded to an upper surface of the waveguides. In some embodiments, the circuit includes beam-combining elements so that a single beam combining all of the input wavelengths is output from the circuit.

Abstract: An optical information processing apparatus includes: a unit that radiates light onto an optical disc and detects the reflected light to output a reproduced signal; a unit that corrects spherical aberration of the light; a unit that adjusts a focus position of the light based on a focus adjustment value; and an adjustment unit that measures a characteristic of the reproduced signal at each of at least three positions on each of at least three straight lines on a plane with coordinate axes representing an amount of spherical aberration correction and focus adjustment value, obtains, from the measurements, as estimated positions, at least five positions on the plane at which the characteristic has substantially the same value, performs an ellipse approximation on the estimated positions, obtains a center of the ellipse, and determines the amount of spherical aberration correction and focus adjustment value based on the center of the ellipse.

Abstract: A clear image of a target to be measured is obtained by suppressing influence of a reflected beam from the surface of the target or a measurement target holding unit. A laser beam emitted from a light source is split into a signal beam, reference beam, and control beam. The signal beam is focused onto the target with an objective lens, so the target is irradiated with the signal beam. The amount of defocus of the control beam is controlled with a defocus control unit, and the phase of the control beam is controlled with a phase control unit. A signal beam reflected or scattered by the target is combined with the control beam to generate a controlled signal beam, and the controlled signal beam is combined with the reference beam. A plurality of interference beams with different phases are generated with interference optics, and phase diversity detection is performed.

Abstract: A hologram recording apparatus is provided, including: a coherent light source; a beam splitter which splits a beam emitted from the coherent light source into a signal beam and a reference beam; a signal beam forming unit including a first optical element which splits the signal beam into a plurality of sub signal beams and deflects the plurality of sub signal beams in different directions. The signal beam forming unit further directs the plurality of sub signal beams onto a hologram recording medium. The recording apparatus also includes a reference beam forming unit which directs the reference onto a location on the hologram recording medium which overlaps with locations on the hologram recording medium on which the plurality of sub signal beams are incident.

Abstract: A microscope system includes: a wavefront modulator that modulates a wavefront of light from a light source; an objective that irradiates a sample with light whose wavefront has been modulated by the wavefront modulator; a spherical aberration corrector that corrects spherical aberration caused by a difference between a refractive index of a medium between the objective and the sample and a refractive index of the sample; a refractive index calculator that calculates, for each wavelength of the light from the light source, an average refractive index of a medium between the objective and a condensing position of light emitted from the objective on the basis of an amount of the corrected spherical aberration; and a controller that controls the wavefront modulator to correct chromatic aberration calculated on the basis of the calculated average refractive index for each wavelength.

Abstract: The invention features a scrolling thin film magnifier that is integrated into a composition and can be extended and retracted when used, compositions that include the scrolling thin film magnifier, methods of using the scrolling thin film magnifier to magnify printed indicia, and methods of manufacturing the scrolling thin film magnifier.

Abstract: Provided is an exposing device capable of enhancing usage efficiency of light and preventing degradation of imaging property due to a misalignment with a photosensitive drum. The exposing device includes: a laser array including multiple lasers arranged in a predetermined direction; and an optical system guiding light emitted from the each of the multiple lasers to a photosensitive member and focusing the light on the photosensitive member, in which the optical system includes multiple phase modulation elements to decrease an added phase lag in proportion to distance from a center axis that is defined by a principal light beam emitted from the each of the multiple lasers.

Abstract: A varifocal lens including a first liquid crystal layer; a second liquid crystal layer disposed below the first liquid crystal layer; a common electrode disposed between the first liquid crystal layer and the second liquid crystal layer; a first electrode disposed above the first liquid crystal layer and having a curved shape; and a second electrode disposed below the second liquid crystal layer and having a curved shape.

Abstract: Provided is an optical disc device capable of correcting a value of a control parameter during an operation of reading information from an optical disc medium. The optical disc device for reading the information recorded on the optical disc medium under an operation condition corresponding to a value set with respect to a predetermined control parameter corrects the value of the predetermined control parameter by repeatedly executing, while an operation of reading the information from the optical disc medium is being performed, processing of: acquiring, with respect to two values of the predetermined control parameter, evaluation values indicating accuracy of the reading of the information from the optical disc medium, respectively; and updating the value of the predetermined control parameter based on the two acquired evaluation values.

Abstract: Provided is an optical pickup device that compensates for an aberration caused by a beam splitter. When a beam of light is reflected from a disc and proceeds towards a beam splitter, the beam splitter is designed to allow the reflected beam to pass therethrough. However, the beam splitter can cause an astigmatism in the reflected beam due to diffraction. According to various aspects herein, an optical pickup device may include a compensation device that generates an inverse astigmatism to compensate for the astigmatism generated by the beam splitter.

Abstract: In one embodiment of the present invention, an optical pickup for writing and reading data on an optical storage medium comprises a diffractive element for diffracting a light beam to split it into multiple light beams. The diffracted light beams includes a zero-order diffracted light beam for writing data on a track of the land or the groove of the optical storage medium and non-zero-order diffracted light beams for reading the data from the track. The diffractive element has first and second diffraction gratings that have mutually different grating vector directions and pitches. The first diffraction grating forms light beam spots on the same track by the non-zero-order and zero-order diffracted light beams. The second diffraction grating forms a light beam spot to extend to both sides of said track, or forms a light beam spot on one side of said track, by the non-zero-order diffracted light beams.

Abstract: Disclosed is an optical disc device that provides a stable servo signal with a simple configuration during the use of an objective lens showing significant color aberration. At time T0, which is before the start of a write operation (time T2), a defocus application circuit 111 generates a defocus signal DF1 to be added to a focusing error signal FES. A tracking signal gain control circuit 113 changes a tracking signal gain correction amount to be given to a tracking error signal TES to TG1. The defocus signal generated from the defocus application circuit terminates at substantially the same time the write operation starts (time T2). After the focusing error signal FES is no longer offset (at time T3), the tracking signal gain correction amount generated from the tracking signal gain control circuit 113 is restored to a reference value.

Abstract: An optical information processing method and apparatus performs a light irradiating and receiving step, a signal processing step, and an adjusting step of a spherical aberration and a focus offset on the basis of shift amount of first and second control devices and a performance evaluation value. The performance evaluation values for first, second, third and fourth points in an x and y coordinate system are detected, in which an x-coordinate is one of the shift amount of the first control device and the shift amount of the second control device and a y-coordinate is the other, the first point, second and third points having the same y-coordinate and different x-coordinates with each other, the fourth point being provided on a first straight line passing through the first point and being different from the first point.

Abstract: Provided is a lens driving unit for an optical pickup and an optical disc drive employing the lens driving unit. First and second driving coils are directly wound around a coil winding unit included in the lens frame, which is different from a conventional lens frame in which a driving coil is manufactured as a separate element and is separately attached to a lens frame.

Abstract: The present invention provides a method for determining what group a given multilayer optical disc belongs to. The disc is one of a number of multilayer optical discs, which are designed so that information stored is retrievable from any of the discs by irradiating the disc with a light beam having the same wavelength and which have been classified into multiple groups. According to this method, performed first is Step (A) of measuring either a distance from a first one of multiple information layers of the given multilayer optical disc to a second one thereof, which is located adjacent to the first information layer, or a distance from the first information layer to the surface of the optical disc. Next, Step (B) of determining, by the distance measured, what group the given multilayer optical disc belongs to is performed.

Abstract: A focus servo control device includes a first detector, first controller, second detector, and second controller. The first detector detects a first focus error signal. The first controller controls the objective lens based on the first focus error signal, so that a focal point of the first laser agrees with the guide layer. The second detector detects a second focus error signal. The second controller changes a relative distance between the focal point of the second laser and the focal point of the first laser, so that the focal point of the second laser agrees with a target recording/reproducing layer.

Abstract: A method for servoing when reading out a recorded holographic disk or recording in a preformatted disk includes detecting a primary signal of a reflected primary beam from a target data track of a target data layer of the disk, wherein the primary beam of radiation has a first wavelength; comparing a power measurement of the primary signal with a threshold value of power; detecting a tracking signal of a reflected tracking beam from a reference layer of the disk in an event that the power measurement of the primary signal is below the threshold value, wherein the tracking beam of radiation has a second wavelength; generating a servo error signal based upon the primary signal or the tracking signal; actuating an optical sub-system based upon either of the primary servo error signal or the tracking servo error signal such that the primary beam focuses on the target data layer.

Abstract: In a diffractive element, its grating pattern is so configured that a diffraction angle of a diffracted light beam of a light source that is subject to the first-order diffraction in a diffraction area is matched with an angle of a light beam passing through the diffractive area emitted from a light source and a light source position is matched with a light originating point of the light source that emits a light beam to be transmitted, and the center of light intensity distribution is matched with that of the light source passing through the diffractive element by inclining an optical axis of the light source. A position of the diffractive element is adjusted based on an electric current value generated when a reflected return path light beam of the light source is diffracted by the diffractive element and enters the light source.

Abstract: An optical system for optical pickup includes a magnification conversion optical element moving along an optical axis direction in accordance with each of optical recording medium recording surfaces, and an objective lens element converging a light beam incident through the magnification conversion optical element, to form a spot on a corresponding one of the recording surfaces, and satisfies the following formula: 4.0×10?4<Mn/(tn?tc)×f<6.0×10?4. Here tc is the thickness [?m] of a recording-medium base material at which a third-order spherical aberration occurring when a parallel light beam is incident on the objective lens element is the minimum, f is the focal length [mm] of the objective lens element, and Mn is the imaging magnification of the objective lens element when a spot is formed through a thickness tn [?m]of the base plate.

Abstract: Provided is an optical pickup device that suppresses a fluctuation of a tracking error signal caused by stray light when recording/reproducing information on/from an optical disc including a plurality of recording layers and attains size reduction. It includes a laser diode emitting laser light of about 405 nm in wavelength, an objective lens irradiating the optical disc with an optical beam emitted from the laser diode and having a numerical aperture of about 0.85, and a detector including a detection part receiving the optical beam reflected from the optical disc. An optical magnification from the optical disc to the detector is set within a range from about 10× to 15×.

Abstract: A method for determining a type of an optical disk includes following steps. A laser beam of a first type is focused on a disk to generate a first optical reflection signal. A first spherical aberration estimate is generated according to the degree of dispersion and strength of the first optical reflection signal. A laser beam of a second type is focused on the disk to generate a second optical reflection signal. A second spherical aberration estimate is generated according to the degree of dispersion and strength of the second optical reflection signal. The type of the disk is determined based on the first spherical aberration estimate and the second spherical aberration estimate.

Abstract: A recording/reproducing apparatus having an optical pickup device which is efficient in light use having little spherical aberration.

Abstract: An optical head capable of recording or playing back optical discs is provided. The optical disc comprises a light source to emit a beam, an objective to focus the beam on an optical disc, a beam dividing element having a plurality of divided areas with which to divide a cross section of the beam reflected from the optical disc, and a light detector to receive the beams divided by the beam dividing element, wherein the beam dividing element has in at least one of the plurality of areas an aberration imparting function of imparting an astigmatism or defocus aberration to a beam passing through that area.

Abstract: In an optical disk having multiple layers for which a correction of spherical aberration is required, a spherical aberration correcting element is set to a predetermined spherical aberration correction amount; a laser light source is turned ON; an objective lens is swept; when it is discriminated that the optical disk has two or more layers, or has more than two information recording planes, the spherical aberration correction amount is changed into a spherical aberration correction amount suitable for information recording planes of three, or more layers; and the objective lens is again swept so as to discriminate a total layer number thereof.

Abstract: When an optical pickup used for an optical disk device is formed, the optical pickup includes a stepping motor which drives a lens used to correct for spherical aberration, and the stepping motor is mounted in such a manner that the stepping motor is exposed at a surface (upper part) where the stepping motor faces the optical disk. In addition, the stepping motor is mounted in such a manner that the stepping motor is exposed at a surface (lower part) opposite the surface where the stepping motor faces the optical disk. Consequently, the optical pickup used for an optical disk device is adapted to cool a built-in stepping motor without using expensive components when the optical pickup is formed, the optical pickup being configured to make the optical pickup itself thinner and making the operation of the stepping motor stable.

Abstract: Provided is an objective lens manufactured well by using a mold and an optical pickup apparatus including the same. The objective lens of the present invention includes a first region that focuses laser beams of a BD, DVD, and CD standards, a second region that focuses the laser beams of the DVD and CD standards, and a third region that focuses the laser beams of the BD and the DVD standards are provided in this order from a center portion of the objective lens. A first annular zone step provided in the first region has a step amount larger than step amounts of annular zone steps provided in other regions.

Abstract: An optical disk device is configured such that when an optical disk including three or more recording layers on one side is inserted into the optical disk device, a movable lens position adjustment device performs adjustment using as an index a tracking error signal provided with a limit to an amount of movement of a movable lens for spherical aberration correction at start-up of the optical disk device and sets an upper limit to the number of retries of the adjustment at the recording layer farthest away from the side on which the laser beam is incident to 1 or more.

Abstract: Provided is an objective lens, which is provided in an optical pickup including a spherical aberration correction mechanism which performs a spherical aberration correction with respect to laser light applied to a recording layer of an optical recording medium, having the recording layer on which information can be recorded at a plurality of positions in a depth direction, via the objective lens, and a tilt correction unit which varies a lens tilt angle which is a tilt angle of the objective lens, thereby performing a tilt correction.

Abstract: Before tracking control is turned on, there is determined a correction formula for correcting a balance value of a tracking error signal depending on a position of a movable lens for spherical aberration correction. Then, after the tracking control has been turned on, using an RF signal as an index, the adjustment of the position of the movable lens for spherical aberration correction is performed, while the balance value of the tracking error signal is corrected by use of the correction formula. An adjustment value for adjusting the balance value of the tracking error signal at a time point of completing the adjustment of the position of the movable lens for spherical aberration correction is stored.

Abstract: An optical element which has optical steps each providing a phase difference to transmitted light and has low light amount loss and a high efficiency is provided. The optical element includes a symmetry axis, a plurality of optically functional surfaces which are ring-shaped regions around the symmetry axis, and a plurality of wall regions connecting the optically functional surfaces to each other. The optically functional surfaces and the wall regions constitute the optical steps. On a cross-section taken by, as a cutting plane, a plane including the symmetry axis, the contour line of each wall region is substantially parallel to a light beam which is incident on the optically functional surface on the outer side and passes near the wall region. The maximum value of the angle between the symmetry axis and the light beam passing near the wall region is equal to or more than 25 degrees.

Abstract: An object of the invention is to provide an optical disc device, an optical head, and an information processing device that enable to advantageously record or reproduce information with respect to an information recording medium having three or more information recording surfaces with light transmissive layers of different thicknesses from each other.

Abstract: Provided is an objective lens that allows securing of a long working distance for a laser beam with a long wavelength and has a predetermined thickness or larger, and an optical pickup apparatus including the objective lens. In an objective lens of the present invention, a first region that focuses laser beams of a BD, DVD, and CD standards, a second region that focuses the laser beams of the DVD and CD standards, and a third region that focuses the laser beams of the BD and the DVD standards are provided in this order from a center portion of the objective lens. An optical super resolution with the laser beam of the BD standard is achieved by preventing a portion of the laser beam of the BD standard transmitted through the second region from contributing to spot formation.

Abstract: Provided is an optical pickup device which suppresses the decrease of light amount and performs conversion to circular polarization light, wherein the optical pickup device includes a beam splitter and a raising mirror on each of which a layered member is formed, and the optical pickup device satisfies conditional expressions relating to intensities of S-polarized light and P-polarized light with respect to the beam splitter of a laser beam emitted from a semiconductor laser element, reflectances of S-polarized light and P-polarized light on the beam splitter, a reflection phase difference obtained by subtracting a phase of S-polarized light from a phase of P-polarized light after the reflection, reflectances of S-polarized light and P-polarized light on the raising mirror, and a reflection phase difference obtained by subtracting a phase of S-polarized light from a phase of P-polarized light after the reflection.

Abstract: An astigmatism element converges laser light in a first direction for generating a first focal line, and converges the laser light in a second direction perpendicular to the first direction for generating a second focal line. A light separating element guides the laser light entered into two first areas and into two second areas to four respective positions different from each other, and guides the laser light entered into a third area to a position different from the four positions. When an intersection of two straight lines extending in parallel to the first direction and the second direction and intersecting with each other is aligned with an optical axis of the laser light, the third area is disposed at the intersection of the two straight lines.

Abstract: An optical pickup includes a light source, an objective lens, a diffraction grating that divides an optical beam reflected from a predetermined information layer, into a plurality of optical beams, and a detector having a plurality of photo-receivers to receive a plurality of optical beams. The diffraction grating has a predetermined region for dividing from a signal light beam a region including a central portion of a spot which the signal light beam will form on the diffraction grating. A distance from a central section of the detector to that of a spot center photo-receiver on the detector, the spot center photo-receiver being provided to receive the optical beams formed by division in a predetermined region of the diffraction grating, is equal to or greater than a spot radius of the unwanted light beams entering the predetermined region of the diffraction grating, on the detector.

Abstract: A lens pull-in method is used in a near-field optical accessing system. When a lens is in a far-field range, the lens is driven to approach a surface of an optical disc in an open loop control state. If the lens enters a near-field range, a first GES level is inputted as a set value and the lens is driven in a close loop control state. When the gap error signal decreases to the first GES level, the set value is changed to a second GES level, which is higher than the first GES level. When the gap error signal increases to the first GES level, the set value is changed to a target GES level, so that the gap error signal is maintained at the target gap error signal.

Abstract: An optical-pickup apparatus includes: a three-wavelength-laser diode including first-, second-, and third-laser elements to emit first-, second-, and third laser beams having first, second, and third wavelengths, respectively, the three laser elements housed in the same case; an objective lens to focus the three laser beams onto first- to third-optical-disc-signal-recording layers, respectively; a first photodetector to be irradiated with first-return light reflected from the first-optical-disc-signal-recording layer, a second photodetector to be irradiated with second- and third-return lights respectively reflected from the second- and third-optical-disc-signal-recording layers; a polarizing-beam splitter to reflect the three laser beams toward the lens, and allow the three return lights having passed through the lens to pass therethrough; a semitransparent mirror on which the three return lights having passed through the polarizing-beam splitter are incident, and which guide the first-return light toward th

Abstract: In one embodiment, the optical read/write apparatus includes a plurality of optical pickups arranged to cross tracks of an optical storage medium and a control section. On finding the data that has been written by any of those optical pickups inaccurate or on detecting any defect at a location where data is going to be written by any of the optical pickups, the control section instructs another one of the optical pickups to write that data on a different track from a track on which the data should have been written.

Abstract: A reproducing method includes: irradiating a laser spot for servo to which astigmatism making up a generally 45-degree angle in the tangential direction of an information recording track has been applied, and one or more laser spots for reproduction, onto a recording medium where a track group is formed with multiple information recording tracks adjacent with a narrower track pitch than a track pitch equivalent to optical cut-off, and also where a track group pitch is wider than the track pitch equivalent to optical cut-off; and subjecting one or more laser spots for reproduction to on-track control as to one of the information recording tracks by taking a tangential push pull signal obtained from reflected light information of the laser spot for servo as a tracking error signal, and performing tracking servo control using this tracking error signal, and reproducing data from the reflected light information thereof.

Abstract: A method for controlling layer changes for an optical disk drive is provided, where a focus of a laserbeam emitted by a pickup head of the optical disk drive is moved from a current data layer of a disk to a target data layer of the disk. First, a position of a collimator lens of the pickup head is adjusted for spherical aberration correction. The objective lens is then lowered to a low position to move the focus of the laserbeam off the surface of the disk. The objective lens is then raised towards the disk. A focusing error signal is generated while the objective lens is being raised. Whether a target S-curve corresponding to the target data layer is present in the focusing error signal is then started to be detected. If the target S-curve is detected, the focus on operation on the target data layer of the disk is successful.

Abstract: An astigmatism element converges laser light in a first direction for generating a first focal line, and converges the laser light in a second direction perpendicular to the first direction for generating a second focal line. A light separating element guides the laser light entered into two first areas and into two second areas to four positions different from each other. The light separating element imparts a light separating function to the laser light entered into the first two areas in directions identical to each other and with magnitudes different from each other, and imparts a light separating function to the laser light entered into the two second areas in directions identical to each other and with magnitudes different from each other.

Abstract: A recording and reading system for a multi-layered optical recording medium includes: a multi-layered optical recording medium including a plurality of recording layers and a single servo layer; and an optical head. The optical head includes a recording and reading objective lens of a signal recording and reading optical system and a servo objective lens of a servo signal detection optical system that are disposed on a common actuator. The recording and reading objective lens is mounted on the common actuator through a minute-drive apparatus so as to be minutely driven in a focusing direction relative to the servo objective lens. When the servo objective lens is focused on the servo layer, a reading light beam is quickly focused on a target one of the plurality of recording layers.