Abstract: The invention concerns a system for determining the topography of a diffusely reflecting curved surface, that comprises two telecentric projection branches that project fringe images of a Ronchi grating on the diffusely reflecting curved surface, and a viewing branch of which the optical system projects an image of the illuminated surface on its camera target, and comprises further a computer that receives the fringe images recorded by the camera target and calculates from these the topography of the anterior eye surfaces, in which system the projection sources are semiconductor diodes and the optical system of the viewing branch is two-sided telecentric.

Abstract: The invention concerns a system for determining the topography of a diffusely reflecting curved surface, that comprises two telecentric projection branches that project fringe images of a Ronchi grating on the diffusely reflecting curved surface, and a viewing branch of which the optical system projects an image of the illuminated surface on its camera target, and comprises further a computer that receives the fringe images recorded by the camera target and calculates from these the topography of the anterior eye surfaces, in which system the projection sources are semiconductor diodes and the optical system of the viewing branch is two-sided telecentric.

Abstract: 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.

Abstract: 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.

Abstract: An optical height measuring arrangement is described in which the radiation reflected from the surface to be measured is projected towards a position-dependent radiation-sensitive detection system via a lens system. The direction of the beam which is incident on the surface is varied at a high frequency and the amplitude of the output signal of the detection system is a measure of the distance to be measured. When two detection systems are employed it is also possible to measure the surface roughness.

Abstract: 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.

Abstract: An optical assembly comprises an elongate hollow body (11) of triangular cross-section, having three deformable side walls which adjoin each other and at least one optical element (1). Inside the body the optical element is secured without play to each of the side walls at a well-defined location and in a well-defined position by rigid local connections (15).

Abstract: An optical system which provides a collimated light beam, having a tubular holder, a semiconductor laser and a system of lenses incorporated in the holder, in which the semiconductor laser is positioned against an abutment in the axial direction of the holder and a resilient element is placed between the system of lenses and the abutment, while on the side of the system of lenses remote from the resilient element a locking element is present which, after axial adjustment in the holder, is fixed in such a location that the system of lenses, after moving in the axial direction against the pressure of the resilient element, is in the position in which its focus coincides with the laser element in the semiconductor laser.