Abstract: There is provided a device for use by a user who may wander that comprises an audio unit for generating a first output audible to the user in response to a determination that the user is within a predetermined safe area. The audible output preferably comprises music. There is also provided a method of operating a device that is to be worn or carried by a user, comprising generating a first output audible to the user using an audio unit in the device in response to a determination that the user is within a predetermined safe area.

Abstract: An optical wavefront modifier (27) is adapted for modifying a wavefront of an optical beam passing through the modifier. The modifier comprises a first and a second transparent electrode layer (42?, 43?) and a flat medium (46) for modifying the wavefront in dependence on electrical excitation and arranged between the electrode layers. The first electrode layer (42?) comprises three or more electrodes (51-55) of a transparent, conductive material. The electrode layer also comprises a series arrangement of resistors, comprising three terminals (48, 48?, 48?) connected to the electrodes and resistors (49, 49?) connecting the terminals. The resistors are made of the same transparent conductive material as the electrodes.

Abstract: The present invention provides a scanning device with the following features: the system is capable of writing data to record carriers of a first format because it is corrected for chromatic aberration resulting from fast wavelength variations during write operation; it has a diffractive element with a generally sawtooth-like pattern, such that it may for example be manufactured in a single-step replication process; the system has high efficiency for scanning first optical record carriers (e.g. DVDs) and acceptable efficiency for scanning second optical record carriers (e.g. CDs); and the lens provides limited spherochromatism and the system is thus able to cope with wavelength variations.

Abstract: An optical device scans record carriers with radiation of two wavelengths. The device has an objective lens with a diffractive part with a pattern of elements of stepped profile. The total of the step heights are substantially equal to multiples of height h1 with h 1 = λ 1 ( n - n 0 ) , where &lgr;1 is the first wavelength, n is the refractive index of the diffractive part, and n0 is the refractive index of an adjacent medium. The radiation of the first wavelength is transmitted through the diffractive part substantially without diffraction and the objective lens has a first focusing characteristic for the first wavelength.

Abstract: The present invention provides a scanning device with the following features: the system is capable of writing data to record carriers of a first format because it is corrected for chromatic aberration resulting from fast wavelength variations during write operation;

Abstract: An optical head scans the information layer (3) of an optical record carrier (1) by means of a radiation beam (13). Optical aberrations in the beam such as coma and spherical aberration, caused by tilt and thickness variations in the optical disc respectively, are compensated by an aberration compensator (27) arranged in the radiation beam. The tilt or thickness variation is measured by a detector (30) and used to control the aberration compensator. The radiation beam is focused onto the information layer by an objective system (11). A displacement of the objective system in the transverse direction (26) as used for radial tracking of the optical beam, causes a mismatch between the wavefront to be compensated and the wavefront introduced by the aberration compensator (27). The mismatch is reduced by using a position detector (33) for measuring the transverse position of the objective system and using the position signal (34) as input for the control of the aberration compensator.

Abstract: An optical wavefront modifier (27) is adapted for modifying a wavefront of an optical beam passing through the modifier. The modifier comprises a first and a second transparent electrode layer (42′, 43′) and a flat medium (46) for modifying the wavefront in dependence on electrical excitation and arranged between the electrode layers. The first electrode layer (42′) comprises three or more electrodes (51-55) of a transparent, conductive material. The electrode layer also comprises a series arrangement of resistors, comprising three terminals (48, 48′, 48″) connected to the electrodes and resistors (49, 49′) connecting the terminals. The resistors are made of the same transparent conductive material as the electrodes.

Abstract: An optical head scans the information layer (3) of an optical record carrier (1) by means of a radiation beam (13). Optical aberrations in the beam such as coma and spherical aberration, caused by tilt and thickness variations in the optical disc respectively, are compensated by an aberration compensator (27) arranged in the radiation beam. The tilt or thickness variation is measured by a detector (30) and used to control the aberration compensator. The radiation beam is focused onto the information layer by an objective system (11). A displacement of the objective system in the transverse direction (26) as used for radial tracking of the optical beam, causes a mismatch between the wavefront to be compensated and the wavefront introduced by the aberration compensator (27). The detrimental effects of the mismatch are reduced by compensating only part of the aberration. The degree of compensation depends on the maximum displacement of the objective system and the tolerable wavefront error.

Abstract: A device according to the invention is suitable for scanning an information carrier with tracks around an axis. The device has means for transferring information to/from a scanning spot on the information carrier. The device has tangential displacement means for moving the scanning spot in a tangential direction and radial displacement means for moving the scanning spot in a radial direction. The device has control means for controlling the radial displacement means and radial position measurement means for generating a radial position signal (cos(9&bgr;r), sin(9&bgr;r)) which is a measure of the instantaneous radial position of the scanning spot. The device has a scanning mode in which the scanning spot follows a track and a displacement mode in which tracks are crossed. The device according to the invention is characterized by tangential position detection means for generating a tangential position signal (S&agr;) which is indicative of the tangential position (&agr;) of the scanning spot.

Abstract: An optical head scans the information layer (3) of an optical record carrier (1) by means of a radiation beam (13). Optical aberrations in the beam such as coma and spherical aberration, caused by tilt and thickness variations in the optical disc respectively, are compensated by an aberration compensator (27) arranged in the radiation beam. The tilt or thickness variation is measured by a detector (30) and used to control the aberration compensator. The radiation beam is focused onto the information layer by an objective system (11). A displacement of the objective system in the transverse direction (26) as used for radial tracking of the optical beam, causes a mismatch between the wavefront to be compensated and the wavefront introduced by the aberration compensator (27). The mismatch is reduced by using a position detector (33) for measuring the transverse position of the objective system and using the position signal (34) as input for the control of the aberration compensator.

Abstract: An optical wavefront modifier modifies a wavefront of an optical beam passing through the modifier. The modifier comprises a first and a second transparent electrode layer and a flat medium for modifying the wavefront depending on electrical excitation of the medium and arranged between the electrode layers. The electrode layers are provide the electrical excitation to produce a first wavefront modification of a first order of a radius in the cross-section of the beam in the plane of the medium and simultaneously produce a second wavefront modification of a second order of the radius different from the first order.

Abstract: An optical device scans record carriers with radiation of two wavelengths. The device has an objective lens with a diffractive part with a pattern of elements of stepped profile.

Abstract: An optical scanning device for scanning a record carrier directs a radiation beam towards the record carrier. Two detection systems are arranged in the path of the beam reflected by the record carrier, one before and one after the focus of the beam. Output signals of the detection systems represent the intensity distribution of the beam in the plane of each detection system. The output signals are processed to form a signal representing an aberration of the reflected beam. The aberration may be coma or spherical aberration. The aberration signal is used to control a compensation element in the optical path of the radiation beam incident on the record carrier.

Abstract: An optical head scans the information layer (3) of an optical record carrier (1) by means of a radiation beam (13). Optical aberrations in the beam such as coma and spherical aberration, caused by tilt and thickness variations in the optical disc respectively, are compensated by an aberration compensator (27) arranged in the radiation beam. The tilt or thickness variation is measured by a detector (30) and used to control the aberration compensator. The radiation beam is focused onto the information layer by an objective system (11). A displacement of the objective system in the transverse direction (26) as used for radial tracking of the optical beam, causes a mismatch between the wavefront to be compensated and the wavefront introduced by the aberration compensator (27). The detrimental effects of the mismatch are reduced by compensating only part of the aberration. The degree of compensation depends on the maximum displacement of the objective system and the tolerable wavefront error.

Abstract: An optical wavefront modifier (27) is adapted for modifying a wavefront of an optical beam passing through the modifier. The modifier comprises a first and a second transparent electrode layer (42, 43) and a flat medium (46) for modifying the wavefront in dependence on electrical excitation of the medium and arranged between the electrode layers. The electrode layers are adapted to impress a first wavefront modification of a first order of a radius in the cross-section of the beam in the plane of the medium and to impress simultaneously a second wavefront modification of a second order of the radius different from the first order.