Abstract: A multiple data layer optical disk drive system has fixed aberration correction and uses a disk with maximum interlayer spacing for reduced interlayer crosstalk. In one embodiment the multiple data layer disk has a substrate with a thickness that is reduced by approximately one-half the thickness of the spacer layer that separates the first and last data layers. The disk is designed to operate with a lens that has spherical aberration correction to compensate for the thickness of a conventional single data layer disk. This allows the disk drive to handle multiple data layer disks as well as to be backward compatible and thus handle conventional single data layer disks. The thickness of the substrate material plus one-half the thickness of the spacer layer material (which may have a different index of refraction than the substrate material) is equivalent, for purposes of spherical aberration correction, to the thickness of the substrate material used in the conventional single data layer disk.

Abstract: A mask is used to remove substantially all of the first order diffraction components of a reflected light beam which are generated as the beam crosses grooved data tracks in an optical media. The mask may comprise a transparent substrate with an opaque layer having a pair of circular apertures or a bow-tie shaped aperture. The apertures are located outside the regions of interference between the diffracted components and the undiffracted component. The layer may be made of a reflective material for reflecting diffracted components of the reflected beam to a tracking error sensor. The layer may be made of a holographic material for deflecting the diffracted components to a tracking error sensor.

Abstract: An optoelectronic system for controlling laser drive current to produce a power level at the target independent of changes in the transmissivity of a beamsplitter positioned in the optical path between the laser source and the target. A second beamsplitter with transmissivity and reflectivity factors matched to the first beamsplitter is used to direct portions of light to two photodetectors. The two photodetectors are connected to circuits which produce a signal proportional to the power transmitted by the first beamsplitter divided by the power reflected by the second beamsplitter, that quotient multiplied by the sum of the photodetector signals to produce a final detection signal which is used as input to the servo control of laser drive current.

Abstract: A holographic mirror is used in an optical storage head to diffract a laser beam perpendicularly to the optical medium and also to focus the beam onto the optical medium. The mirror can also function to cause circularization of a collimated laser beam of elliptical cross-section.

Abstract: An apparatus and process for determining focus correction for a lithographic tool are provided. A periodic surface relief structure containing focus information is illuminated so that diffraction beams are generated. An object is translated orthogonally to the periodic structure to cause a change in the intensity of the diffracted beams. Focus correction is determined based upon the changes in the intensity of the diffracted beams.

Abstract: An apparatus forming a wedge shaped mirror tunnel makes the intensity distribution across a light beam uniform. A light beam is directed along a predetermined path through a cylindrical lens to focus the beam to a line at a particular point P. A plane mirror is placed along the predetermined path near point P so that the beam is folded onto itself. A plurality of cascaded optical means of this type, each stage of which comprises a focusing lens and a reflective surface, is used to achieve the beam uniformity needed for the chosen application. In each of the cascaded stages, the reflective surface is positioned at the appropriate angle to fold the beam upon itself.

Abstract: A laser light source for a high resolution projection lithography system and transforming optical apparatus which transforms the laser light into an optically equivalent self-luminous curved line source. The transforming optical apparatus comprises a two-dimensional array of fly's eye lenses positioned to intercept light from the light source and to produce a series of point sources having a selected numerical aperture. An optical fiber array is positioned so that the imput end of each fiber receives the light output from one of the lenses in the array. The position of the fibers is chosen so that light from the lenses underfills the fibers to preserve the numerical aperture. The output ends of the fibers are arranged in position to produce a curved line source of a desired shape. Alternate embodiments are described in which lens arrays can be selectively positioned to change the numerical aperture of the transforming optical apparatus.

Abstract: Apparatus for producing a line source of a desired shape from a radiation source such as a laser comprising means for directing the radiation source along a predetermined path as a playback beam to impinge upon a hologram at a predetermined angle to produce a continuous self-luminous source of the desired shape. The hologram is recorded upon a substrate coated with a photosensitive material by interference between recording and object beams derived from the same source of coherent radiation. The recording beam is directed toward the substrate at an orientation and angle so that the playback beam is a conjugate of the recording beam. The object beam is directed to the substrate over a path which includes a diffuser plate covered with an opaque material in all areas except for a continuation area which defines the desired shape. The part of the object beam which impinges upon the substrate is limited by an aperture comprising a sector of an annulus which defines the numerical aperture of the radiation source.

Abstract: In those high speed laser scanning systems, particularly those used in printing, employing an acousto-optical modulator driven at two or more carrier frequencies for scanning with a plurality of focussed beams simultaneously in order to reduce the required deflection scan rate and to better the rise and fall times of the waveforms, unwanted intermodulation effects arise. These undesirable intermodulation effects can be reduced or largely eliminated by increasing the difference in the carrier frequencies such that the diffracted beam spacing is increased considerably and utilizing either a scan line interlace scheme or a staggered beam scheme to maintain the required scan line spacing. In the latter case, the modulator is situated with the direction of propogation of the acousto-waves between zero and 90 degrees to the direction of image pattern scanning. The angle is made sufficiently large as to make one light beam spot in one scanning line lag a corresponding spot in the adjacent line.