Abstract: The invention relates to a system comprising: a source for generating a light beam (B), an optical element (M) intended to receive said light beam (B), an actuator (AC) in which is mounted a plurality of objective lenses (OL0, OL1 . . . ), translation means for translating said optical element (M) so as to direct said light beam (B) toward a given objective lens taken among said plurality of objective lenses (OL0, OL1 . . . ).

Abstract: A switchable diaphragm (9) and a device for beam deflection (10) are placed in the servo branch of an optical drive, in a path of light beams of different diffraction orders. This permits redirection of light beam orders towards a detection means (8) on an individual basis and selection of light orders at a detection means (8) depending on requirements. The number of detectors in the device detection means (8) can thus be reduced, thereby also reducing additional components associated with those detectors and saving on cost and complexity. With such device functionality, new methods for measuring beam landing and spherical aberration are developed.

Abstract: The invention relates to an optical system comprising a fluid chamber 1 and a birefringent part. The fluid chamber comprises first and second fluids 10, 12 having different indices of refraction, the interface between the fluids forming a meniscus 14. The birefringent part is capable of varying characteristics of a first radiation beam 3b and a second radiation beam 3c, the first and second radiation beams having different polarisations. Variation in the configuration of the meniscus causes variation in the characteristics of the first radiation beam and the second radiation beam. Variation in the configuration of the meniscus may be controlled by electrowetting.

Abstract: The invention relates to a method and system comprising: a detector for obtaining first focus error signal (FESn,1) and second focus error signal (FESn,2) dependent on radiation in first and second zones in a cross-section of a radiation beam, respectively, processing means for subtracting said second focus error signal (FESn,2) to said first focus error signal (FESn,1) so as to generate a spherical aberration signal (SAESn), processing means for generating said second focus error signal (FESn,2) according to the formula: FES n , 2 = ? ? [ A 2 - B 2 A 2 + B 2 + C 2 - D 2 C 2 + D 2 ] wherein ? is a parameter, and A2, B2, C2 and D2 comprise output signals from a plurality of radiation detection sectors located in said respective second zone.

Abstract: An optical scanning device which is compatible with both multi-layer and single layer disc formats, and which alleviates lens design requirements by providing a dual lens system and by making, say, lens OL0 compatible with DVD (as well as layer L0 of the dual layer format) and lens OL1 compatible with CD (as well as layer L1 of the dual layer format). Thus the two lens designs only need to work at two different wavelengths, and the device achieves compatibility with three different optical record carrier formats, but the amount of spherical aberration in respect of each lens part only needs to be matched precisely with respect to two formats in one of a number of known ways.

Abstract: A method for radial tracking in an optical disc drive (1) is described. A DTD tracking error signal (S3) is derived from the wobble-induced signal components (WA, WB,WC, WD) of the optical detector signal (SR). This tracking error signal is relatively insensitive to beamlanding errors, and to differences in the signal amplitudes K of the output signal of individual detector segments. Further, the need for a 3-spot grating is eliminated. A distinction is made between on the one hand a situation where the track being followed is empty and on the other hand a situation where the track being followed is written. In case the track being followed is empty, a DTD tracking error signal is derived from the wobble-induced signal components of the optical detector signal, whereas, in case the track being followed is written, a DTD tracking error signal is derived from the datainduced signal components of the optical detector signal.

Abstract: Apparatus and method for measuring the depth of data record layers of an optical storage disc having a cover layer of thickness d, an entrance surface (S), and, for example, a first data layer (L0), a second data layer (L1) and a third data layer (L2). The optical apparatus comprises a spherical aberration compensator (SA), and an objective lens (OL) mounted in an actuator (AC), the actuator (AC) receiving a current I and being arranged and configured to move the objective lens (OL) in the z (axial) axis relative to the optical storage disc. Light incident on the objective lens (OL) is converged into a cone-like beam such that it is focussed on one of the data layers (D1). A control signal is used to keep the scanning spot focussed on the data layer (L1). This control signal is the focus error signal (FES) and is provided by the actuator drive (AC).

Abstract: The invention relates to an information carrier containing a non-clonable optical identifier (2) having an optical scattering medium (3) for being challenged by a light beam (5) and for scattering said light beam (5). In order to provide a secure information carrier (1), it is proposed that it further comprises a light absorbing means (3, 4) for reducing the intensity of said light beam (5) so that an integration time for obtaining a response signal by integrating the scattered light beam (8) is extended.

Abstract: The invention relates to an optical holographic device for recording a data page in a holographic medium (106). The device comprises means (100) for generating a signal beam, means (201) for modulating the phase of the signal beam so as to encode the data page and means (102, 107, 108) for interfering the modulated signal beam with a reference beam inside the holographic medium. The invention also relates to a corresponding holographic read-out device, to a method for reading out a phase-modulated data page and to a holographic medium comprising at least one phase-modulated data page.

Abstract: Optical pick-up apparatus for retrieving data stored on an optical storage disc having a plurality of record layers (6, 7), the radiation beam reflected back from the disc when a first layer (7) is irradiated comprising radiation reflected back from the first layer (7) and radiation reflected back from one or more of the other layers(6). A spatial filter (8) is provided which is arranged and configured to spatially filter the radiation beam so as to cause the radiation reflected by the first record layer (7) and the radiation reflected by any of the other record layers (6) of the optical storage disc to be spatially separated, such that at least a substantial portion of the radiation reflected back from the other layers (6) can be selectively eliminated from the radiation beam prior to retrieval therefrom of the data.

Abstract: In the described method of producing a plurality of bodies bearing equal imprints of a stamp as optical structures, a stamp (13) is initially produced, by attaching particles (14) to a surface (15) of an auxiliary body (16); than, the stamp (13) is used to produce an imprint (11) on a plurality of bodies (10). Optical structures can be irradiated, producing on a screen a speckle pattern indicative of a key. It is substantially impossible to clone a given optical structure with current technological means. Optical structures represent physical One-Way Functions, easy to compute in the forward sense but unfeasible to reverse. Thus, they can be used to build an access/copy protection system of user information contained in an information carrier associated with the body 10. The reproducibility of the optical structures makes this method suitable for optical disks.

Abstract: The invention comprises an optical record carrier comprising a data track, the data track including a sequence of marks and spaces of a plurality of different lengths. The marks and spaces form symbols encoding data. The length of each symbol comprises an integral multiple of a standard bit length, and an offset The offset of each symbol varies according to the nominal length of the symbol, and the nominal length of the neighboring symbol.

Abstract: An optical arrangement of at least a coherent light source (1), a strongly scattering object (5) (the PUF), and a pixe-lated photo-detector (6), wherein the pixels are comparable in size with the bright and dark patches of the speckle pattern produced by coherent radiation traversing the scattering object (5). Quantitively, the pixel size should be roughly ?/NA, where ? is the wave-length, and (i) NA=a/z for free-space geometry, with a being the beam radius and z being the distance between the exit surface of the PUF (5) and the pixelated detector (6), or (ii) NA is the numerical aperture of a lens (7) in an imaging geometry. In a preferred embodiment of the invention, there are tentative requirements that the pixels should be at least smaller than ?max?NA and preferably larger than ?max?/NA, where (in an exemplary embodiment) ?max=5 and ?min=0.05, say.

Abstract: A method and device for measuring the tilt in an optical disc drive (1) is disclosed. The optical disc drive (1) comprises two lasers (31, 41) generating two laser beams (32, 42) having mutually different optical characteristics. One of these laser beams (32) is continuously ON, and is used for writing or reading data to or form the disc. The other laser beam (42) is repeatedly switched ON and OFF. Tilt is measured by comparing a normalized error signal (RED(ON)) during the ON-phase (TON) with a normalized error signal (RED(OFF)) during the OFF-phase.

Abstract: A variable focus lens comprising a first fluid (A) and a second, non-miscible, fluid (B) in contact over a meniscus. A first electrode (2) separated from the fluid bodies by a fluid contact layer (10), and a second electrode (12) in contact with the first fluid to cause an electrowetting effect whereby the shape of the meniscus is altered. The fluid contact layer has a substantially cylindrical inner wall.

Abstract: This apparatus comprises an optical head having the following elements: a light source for illuminating the optical carrier, a light detector for analyzing the light reflected from the optical carrier, an objective lens for focusing the light onto the optical carrier, and a grating device placed at the vicinity of said objective lens. The main optical elements are fixed together so that this disposal improves, the ability of the tracking of the head. DVD reader and recorder.

Abstract: The invention relates to an optical pickup apparatus comprising a photodetector (302) which comprises a first segment (A) and a second segment (B), and an optical element (301) intended to receive an incident light beam, said optical element (301) comprising:—a first portion (L) comprising diffraction means for generating a first 0th diffraction order light beam (A(0)) on said first segment (A), and a first non-0th diffraction order light beam (B(+1)) on said second segment (B),—a second portion (R) comprising diffraction means for generating a second 0th diffraction order light beam (B(0)) on said second segment (B), and a second non-0th diffraction order light beam (A(+1)) on said first segment (A) Use: Optical pickup apparatus

Abstract: An optical scanning device including an optical element (12) having at least two portions, including a body portion (14) having relatively low birefringence and a wavefront aberration generating portion (16) having a relatively high birefringence, the body portion having an attachment surface on which the wavefront aberration generating portion is formed. The wavefront aberration generating portion (16) has a first surface facing the body portion and a second surface facing away from the body portion, the first and second surfaces being of a different shape so that the thickness of the wavefront aberration generating portion, measured parallel to the optical axis, varies along a direction perpendicular to the optical axis. The thickness of the wavefront aberration generating portion at the optical axis is less than half the thickness of the body portion at said optical axis.

Abstract: Tracking system for guiding an optical beam on tracks on an optical disc, said tracking system comprising a photodetector (A1, A2) for detecting optical beams derived from said optical beam, said photodetector generating a first output signal (A) and a second output signal (B), said tracking system comprising first processing means for generating a first differential signal (PP(DC)) corresponding to the low-frequency part of a difference between said first and second output signals. The tracking system comprises second processing means for generating a tracking error signal (PP(AC/DC)) defined by the addition of said first differential signal (PP(DC)) to a second differential signal (PP?(AC)), said second differential signal corresponding to a fraction of the difference in amplitude of the high-frequency components of said first and second output signals. Use: Optical disc player/writer.

Abstract: A dual-stack optical data storage medium (20) is described for read out using a focused radiation beam (29) with a wavelength of 400-410 nm and a Numerical Aperture (NA) of 0.84-0.86. The medium has a substrate (21) and a first stack of layers named L0 (22) comprising a first information layer and a second stack of layers named L1 (23), comprising a second information layer. A radiation beam (29) transparent spacer layer (24) is present between L0 and L1. A transmission stack named TS0 with a thickness dTS0 and an effective refractive index nTS0 contains all layers between L0 and an entrance face (26) of the medium (20). A transmission stack named TS1 with a thickness dTS1 and an effective refractive index nTS1 containing all layers between L1 and the entrance face (26). The spacer layer (24) has a thickness selected from the range 20-30 ?m, the thickness dTS0 in dependence on the refractive index nTS0 and the thickness dTS1 in dependence on the refractive index nTS0 are within a specified area.