U.S. Philips Corporation

Other

Christiaan H Velzel

Henricus M Kessels

Peter Ferdinand Greve

Giok D Khoe

Willem G Opheij

Gijsbertus Bouwhuis

Joseph Louis Horijon

Cornelis S Kooijman

Robert Masselink

Hans Hermann Schreier

Method and interference microscope for microscoping an object in order

The height of a surface (25) along an axis (4) is determined by measuring the axial position of an irradiated spot (31) formed on the surface at the intersection of the surface and the axis. Radiation reflected by the surface and collected by a lens (8) forms an image spot (32) on the axis (4). The position of the image spot is determined by measuring the intensity of the radiation at at least three positions along the axis by means of a detection unit (35). The output signals (44, 44') of the detection unit are processed in an electronic means (43) for determining the position of the highest radiation intensity and for supplying a signal (43') whose magnitude represents the axial position of the image spot (32), hence, of the irradiated spot (31 ).

Optical height detector with coaxial irradiation and image axes and

An optical scanning device for scanning an information plane (2) having tracks is described, which device comprises a radiation source (4) supplying a scanning beam (3) and an objective system (5) for focusing the scanning beam to a scanning spot on the information plane (2). To obtain two tracking spots, two grating parts located at both sides of the scanning beam and capturing border rays from the radiation source are used.

Device for optically scanning an information plane detecting border

An apparatus for optically scanning a surface, such as the information surface of an optical record carrier. An error in focus of the scanning spot on the surface is detected by providing two gratings in succession in the path of the beam reflected from the surface. The grating periods of the two gratings are related in accordance with the nominal beam divergence at zero focus error, and the grating strips thereof are parallel but offset with respect to each other. A bounding line between detectors in a composite radiation-sensitive detection system extends parallel to the grating strips. An interference pattern of light and dark bands is projected by the second grating on the detection system, such pattern having an intensity distribution which varies with variations in focus error and can be enhanced by an appropriate value of the offset between the two gratings.

Optical scanning apparatus which detects scanning spot focus error

Apparatus for scanning the information surface of an optical disc record carrier with a radiation beam. Errors in beam focus on such surface are detected by providing two optical gratings in succession in the path of the radiation reflected from the record carrier. The gratings have a constant grating period, which may be equal or in a fixed ratio, the directions of the grating strips of the two gratings intersecting each other at a relatively small angle, thereby forming a Moire interference pattern in the radiation emergent from the two gratings which rotates due to changes in beam focus. This changes the relative amounts of radiation received by an assembly of radiation detecting elements adjacent the second grating, producing a focus error control signal which can be employed for correcting beam focus.

Optical record carrier scanning apparatus with scanning beam focus error

An optical fiber (5) is coupled to an end face (5) of a semiconductor laser diode and the other end face is coupled to one end of a monomode optical waveguide. The other end of waveguide is terminated in a reflecting manner, e.g. by mirror, to reduce the coherence length of the laser. Thus, so-called 'speckle patterns' are only produced in the transmission fiber over a short distance from the laser and modal noise further on in the transmission fiber can be prevented by avoiding the use of non-ideal fiber couplings or other connections having a spatial filter effect within this short distance from the laser.

Optical transmission system having reduced modal noise

An apparatus is described for reading a record carrier on which information is stored in an optically readable reflecting structure. By projecting two radiation spots one before and one behind the plane of the information structure, it is possible to ascertain whether a read beam is properly focussed on the information structure. An optical wedge-field lens combination extends the range of operation of the focus correction device.

Apparatus for optically reading a record carrier and correcting focus

An apparatus for reading a record carrier on which information is stored in an optically readable structure of trackwise arranged areas and intermediate areas where at least one of the surfaces of the record carrier body has periodic surface undulations along the track direction. A focussing error signal is derived by reflecting a focussed light beam on the record surface and by measuring the amplitude and phase of the portion of the reflected beam that corresponds to the surface undulations.

Apparatus for reading an optically recorded record carrier provided with

An apparatus is described for reading a record carrier on which information is stored in an optically readable reflecting structure. By projecting two radiation spots one before and one behind the plane of the information structure, it is possible to ascertain whether a read beam is properly focussed on the information structure.

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Eindhoven, Netherlands

Christiaan H Velzel