Abstract: A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels &xgr;=d/h, the local number of phase levels &xgr; per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels &xgr;=&xgr;(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.

Abstract: A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels &xgr;=d/h, the local number of phase levels &xgr; per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels &xgr;=&xgr;(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.

Abstract: A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels &xgr;=d/h, the local number of phase levels &xgr; per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels &xgr;=&xgr;(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.

Abstract: The invention provides a near-field photochromic device for a supra-density optical memory, comprising a scanner carrying a data storage medium, an optical head having a tip, to be used for recording, readout and erasing, and located in close proximity to the data storage medium, and at least two lasers, alternatingly optically alignable with the optical head, wherein the data storage medium is a film consisting of a photochromic compound and wherein the distance between the tip and the data storage medium is within the limits of the near field of the optical head.

Abstract: This invention discloses an optical resonator (24) including at least one spiral optical element (44) operative to change the angular phase distribution of modes in the optical resonator (24), thereby to generally eliminate undesirable modes.

Abstract: A triangulation optical system and method for determining at least one coordinate of a surface of an object, along at least one coordinate axis which is substantially transverse to the surface. The method includes the steps of providing incident light of a substantially wide wavelength bandwidth propagating along the axis. Passing the light through an axially dispersing optics so that the light of different wavelengths is focussed at different locations relative to the axis. The different locations defining a multi-colored measuring area and a distance between extreme locations along the axis defining a depth of measuring range. Further, off-axis imaging of the measuring area, detecting intensity of the image and determining the coordinate of the intersection of the surface with the measuring area.

Abstract: A multilayer optical disk system, which includes an optical disk unit having a number of connected optical disks. A number of light sources, such as diode lasers, are used to provide a number of light beams of different wavelengths. A wavelength multiplexer combines the light beams into a single beam which is then axially dispersed so that light of different wavelengths are simultaneously focuses onto the different optical disks. A wavelength demultiplexer splits light reflected from the optical disks according to wavelength to produce separate beams which are then separately detected.

Abstract: A method of designing a holographic optical element (diffractive grating) that transforms a set of waves into another set of waves in order to minimize aberrations in the phase of the output wavefront, includes the steps: (a) define continuous input parameters that characterize the propagation vector components of the incoming wavefront and the desired output wavefront; (b) formulate integral equations for the optimal grating vector components; and (c) solve the integral equations for the optimal grating vector components to minimize the difference between the actual and desired output wavefronts.