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: In a diffractive optical element, first and second diffraction gratings of 10 &mgr;m or less in thickness made from materials of respective different Abbe numbers are laminated through an air layer. The grating thickness of the first diffraction grating is made to be 7.5 &mgr;m, and the grating thickness of the second diffraction grating is made to be 6.54 &mgr;m. Glass of the Abbe number of 63.8 is used for the material of the first diffraction grating, and an ultraviolet curable polymer of the Abbe number of 23.0 is used for the material of the second diffraction grating. Accordingly, the diffraction efficiency of the diffractive optical element is improved to 97% or higher throughout the entire visible spectrum.

Abstract: A diffraction grating having more than two kinds of mediums of a different refractive index, has a refractive index difference between the mediums dependent on an incident polarized light direction. In a sectional plane perpendicular to the direction along a grating pattern, the structure has a boundary line between the mediums periodic for the direction perpendicular to the grating pattern in a grating plane or periodic while enlarging or shrinking to the direction perpendicular to the direction along with the grating pattern in the grating plane and in a limited part of a period, the boundary line does not have a symmetrical plane perpendicular to both of the grating and the sectional plane. Accordingly, a polarized light beam status of ±nth order diffracted light beams becomes different and there is provided a diffraction grating capable of obtaining a generation signal of a magneto-optical recording medium from a difference of an optical amount of a light beam received.

Abstract: In a diffractive optical element composed of three or more laminated layers and having a diffraction grating at each interface between adjacent layers, each even-number-th layer has a uniform thickness.

Abstract: A wide angle imaging system for providing a wide angle field of view of an area exteriorly of a vehicle comprises an outer negative or wide angle group of lenses for receiving the wide angle field of view and directing a virtual image toward a positive, converging or focusing group of optics, which further refract and focus the image and provide a focused image to an image capture device. The focusing group of lenses preferably comprises three plastic optic elements, which include a diffractive element and aspheric surfaces to correct for color, distortion and other aberrations in the wide angle virtual image received from the wide angle group of lenses. The wide angle group of lenses are also preferably formed of a plastic material, such as polycarbonate or acrylic, and include a diffractive element on one of the elements. The imaging system thus provides a low cost, light weight and compact wide angle focusing system which does not include expensive and fragile precision optic and/or glass elements.

Abstract: A diffractive-refractive achromatic lens includes a refractive lens system exhibiting longitudinal chromatic aberration that is substantially proportional to wavelength such that the back focus of the refractive lens system decreases as the wavelength becomes shorter and a diffractive grating for correcting the longitudinal chromatic aberration of the refractive lens system. The refractive lens having such a chromatic aberration includes a positive lens having relatively small dispersion and a negative lens having relatively large dispersion. Further, the following condition (1) should be satisfied: 0.005<f/fD<0.2 where f is a focal length of the entire lens system, and fD is a focal length of the positive diffractive grating.

Abstract: Stepped diffractive surfaces (13) are used to reduce variations in the optical properties of an optical system as a result of a change in the temperature of all or a portion of the system. Such surfaces have optothermal coefficients which differ from the optothermal coefficients of both kinoforms and refractive elements. Accordingly, stepped diffractive surfaces can be combined with such elements to achieve overall thermal control of optical systems employing such elements.

Abstract: Spatial light modulators (SLMs) can be amplitude-only modulated, phase-only modulated, or the pixel amplitudes can even be a function of phase. However, practical devices providing independently controllable values of phase and amplitude are not expected for some time. It has been possible to design modulation patterns for these limited range SLMs that do produce diffraction patterns similar to those possible from full complex SLMs, but hours of intensive iterative optimization usually have been required. Our approach instead develops and evaluates direct, pixel-by-pixel encoding algorithms that map the limited range modulation properties onto the entire complex plane. The advantage of these algorithms (generally recognized by the name pseudo random encoding) over iterative optimization is that designs can be performed in real-time making systems adaptable to rapidly changing situations.

Abstract: A method and apparatus for multicolor detection employing the natural chromatic aberration of a diffractive microlens to detect two or more colors or light. In the preferred embodiment the diffractive microlens detects two colors in the VLWIR spectral region and is focused on a two-part detector having a central region to detect the shorter bandwidth and a concentrically disposed region to detect the long band, VLWIR radiation. These detectors are arranged in a multicolor focal plane array to allow imaging.

Abstract: An optical device for focusing a light beam. The device includes a Fourier diffractive element that can separate an incident beam into n beams along n directions which are symmetric about an optical axis. The device also includes a diffractive element including n Fresnel lenses capable of refocusing the n beams onto the optical axis. The device may be used with lasers and laser cutting devices.

Abstract: A large (10's of meters) aperture space telescope including two separate spacecraft—an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass “aiming” at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images.

Abstract: A method and apparatus for illuminating and imaging two-dimensional and three-dimensional objects located at various distances. The apparatus includes a non-monochromatic light source, a diffractive optical element having a strong chromatic aberration that focuses the light beam generated from the source at various focal distances at where the various objects are located. The light beams are then reflected by the various objects and are received through the diffractive optical element onto an imager.

Abstract: A wide angle imaging system for providing a wide angle field of view area exteriorly of a vehicle comprises an outer negative or wide angle group of lenses for receiving the wide angle field of view and directing a virtual image toward a positive, converging or focusing group of optics, which further refract and focus the image and provide a focused image to an image capture device. The focusing group of lenses preferably comprises three plastic optic elements, which include a diffractive element and aspheric surfaces to correct for color, distortion and other aberrations in the wide angle virtual image received from the wide angle group of lenses. The wide angle group of lenses are also preferably formed of a plastic material, such as polycarbonate or acrylic, and include a diffractive element on one of the elements. The imaging system thus provides a low cost, light weight and compact wide angle focusing system which does not include expensive and fragile precision optic and/or glass elements.

Abstract: An objective lens includes a refractive lens having a positive refractive power, and a diffractive grating having a plurality of concentric ring-shaped steps that are formed on at least one lens surface of the refractive lens. The objective lens is a biconvex plastic lens of which first and second surfaces are aspherical. A diffractive grating is formed on the first surface of the objective lens. The diffractive grating is similar to a Fresnel lens, it is formed as many concentric rings each of which has a wedge sectional shape. The boundary between the adjacent rings is a step to give a predetermined optical path difference. The diffractive grating has wavelength dependence such that spherical aberration varies in the undercorrected direction as wavelength of incident light increases.

Abstract: A two-focal-point pickup device capable of suppressing the generation of glitch or bump in reproduced signal. The optical pickup device irradiates a light beam emitted from a light source onto an optical recording medium to form a light spot on a track of a recording surface of the optical recording medium to read the optical recording medium while controlling the position of the light spot relative to the track of the recording surface. The optical pickup device includes a converging lens section coaxially disposed in an optical axis of the light beam to converge the light beam onto the recording surface; and a hologram lens section coaxially disposed in the optical axis of the light beam to diffract the light beam.

Abstract: A planar optical crossbar switch comprising two thin planar substrates, on each of which are recorded or attached two holographic lenses between which light propagates by means of total internal reflection. The first lens is a negative cylindrical lens, used to input the incident light signal to the substrate, and the second lens is a positive cylindrical lens. The two substrates are disposed at right angles to each other in such a way that the positive lenses are positioned one on top of the other with a spatial light modulator sandwiched between them or beneath them. A linear array of detectors collects the output signal from the negative lens on the second substrate.

Abstract: A zone plate having an aberration correcting function in a wavelength selecting manner and a diffraction grating substantially having a light shielding function in a wavelength selecting manner are formed, respectively, in a center region and a marginal region of a filter, whereby only a predetermined wavelength of light is converged or diverged by the zone plate and is diffracted sideways by the diffraction grating, whereby the luminous flux diameter of the irradiation light is changed while the aberration caused by a convergent lens is favorably corrected. The diffraction type filter 8A is constituted by a first region 11 comprising a central circular portion and a second region 12 comprising a marginal portion thereof. The first region 11 is provided with a zone plate 11A (diffraction grating formed like concentric circles) having such a wavelength selectivity that light at a wavelength of 635 nm is transmitted therethrough as it is and that light at a wavelength of 780 nm is converged thereby.

Abstract: A method for encoding zero-order phase-only holograms, and the holograms so encoded. The amplitude and phase of each point of a discrete mathematical transform, such as a Fourier transform, of an image to be encoded, are encoded as regions of a corresponding pixel of a transparent filter, with suitably selected fractional areas and optical path lengths. The various optical path lengths may be created by manipulating the filter's index of refraction, or by manipulating the thickness of the filter, preferably by etching. Various encoding schemes are presented, appropriate to etching systems with low lateral resolution, to etching systems with high lateral resolution but depth resolution limited to a discrete number of depths, and to etching systems with limited resolution both laterally and in depth.

Abstract: A two-focal-point pickup device capable of suppressing the generation of glitch or bump in reproduced signal. The optical pickup device irradiates a light beam emitted from a light source onto an optical recording medium to form a light spot on a track of a recording surface of the optical recording medium to read the optical recording medium while controlling the position of the light spot relative to the track of the recording surface. The optical pickup device includes a converging lens section coaxially disposed in an optical axis of the light beam to converge the light beam onto the recording surface; and a hologram lens section coaxially disposed in the optical axis of the light beam to diffract the light beam.

Abstract: A diffractive optical element including a stack of first, second and third optical regions or a stack of first, second, third and fourth optical regions, a first relief pattern formed between the first and second optical regions, and a second relief pattern formed between the second and third or between the third and fourth optical regions. The first and second relief patterns have substantially identical pitch distributions and are substantially aligned in a direction of an optical axis. Depths of the first and second relief patterns are set such that a wavelength dependency of diffraction efficiency can be decreased over a wavelength range to be used. It is possible to manufacture in a simple manner at a low cost a diffractive optical element in which undesired flares and ghosts are suppressed.

Abstract: An image-reading lens is formed of a two lens elements of meniscus shape, one with its convex surface on the most object-side of the image-reading lens and one with its convex surface on the most image-side of the image-reading lens. An intermediate lens element of negative refractive power may be optionally provided. A zone plate diffractive optical surface having different depth zones surrounding a vertex is formed on at least one aspherical surface of the two lens elements of meniscus shape so as to correct simltaneously for both lateral color and curvature of field. Another surface, preferably of the same lens element having the zone plate diffractive/aspherical surface, is made aspherical. Of the two lens elements of meniscus shape, one is made of plastic material and the other is made of non-plastic material. The image reading lens provides a high image quality having a small temperature dependence, despite one lens element thereof being made of plastic material.

Abstract: A scanner including a plastic focusing lens and thermal compensation element, integrally formed with the asphere or comprising a separate element, to replace the existing glass laser diode focusing lens. The combined optical system is thereby configured to provide overall temperature compensation for the system with reduced cost and improved performance.

Abstract: An objective lens for condensing a light beam, has at least one of annular grooves and ridges producing a phase difference. Each of the annular groove and ridge is formed concentrically on at least one of an incident surface which said light beam is introduced, and an emission surface which said light beam is emitted.

Abstract: A substrate having an optical element on an input surface thereof receives a light beam not having a desired beam shape and shapes the light beam into a predetermined intensity distribution. The substrate may further include a second optical element for providing a predetermined phase pattern to the light beam provided by the first optical element. The first optical element may, for example, circularize an elliptical light beam using a soft aperture for differential power attenuation or by altering the divergence of the light beam along the different axes of the light beam. When the divergence angles are altered and the collimating optical element is provided on the output surface, the thickness of the transparent substrate is determined in accordance with a resultant difference in the divergence and/or with the initial difference in beam size along each axis and with a required circularity.

Abstract: Disclosed is a scanning optical system, which is provided with a light source, a deflector, which deflects a beam emitted from said light source, and a scanning lens for converging the beam deflected by said deflector onto a surface to be scanned. The scanning lens has a positive power as a whole, and includes a plurality of refraction lens elements. Further, a diffraction lens structure is formed on at least one surface of one of the plurality of lens elements. Combination of the refraction lens elements and the diffraction lens structure compensates a lateral chromatic aberration caused by the refraction lens elements.

Abstract: A multifocal diffractive lens includes at least two annular zone lenses. Provided between adjacent annular zone lenses is an optical step. Each annular zone lens exhibits a refractive power profile D.sub.g,i (r) wherein i is any i-th annular zone lens and r is the distance between an axis of the diffractive lens and a point on a back surface of the lens. The lens is further characterized in that an average power of zones i,j . . . are given by D.sub.av,i, D.sub.avj . . . respectively, and optical path lengths of light rays extending from an object point to a conjugated image point are different by the optical step for light rays transmitting through adjacent annular zone lenses. The annular zone lenses are shaped and positioned such that all of the average refractive powers D.sub.av,i, D.sub.avj . . . are substantially equal to a single value, D.sub.av.

Abstract: A chromatic aberration correcting element that is a simple lens having at least one aspheric surface, the radius of curvature of which increases from the optical axis toward the periphery. At least one of the surfaces is formed as a diffraction lens surface that consists of annular segments that shift discretely in a direction in which the lens thickness increases as a function of the distance from the optical axis. Also disclosed is a chromatic aberration correcting device having annular segments formed in steps on either a light entrance face or a light exit face or both. The annular segments are composed of planes perpendicular to and concentric with the optical axis.

Abstract: An objective lens includes a refractive lens having a positive refractive power, and a diffractive lens structure having a plurality of concentric ring-shaped steps that are formed on at least one lens surface of the refractive lens. The objective lens is a biconvex plastic lens having first and second aspherical surfaces. A diffractive lens structure is formed on the first surface of the objective lens. The diffractive lens structure is similar to a Fresnel lens, it is formed as many concentric rings each of which has a wedge sectional shape. The boundary between the adjacent rings is formed as a step giving a predetermined optical path difference. The diffractive lens structure has wavelength dependence such that at least two light beams having different wavelength with an identical diffractive order form appropriate wavefronts for at least two kinds of optical discs respectively provided with cover layers having different thickness.

Abstract: An optical pickup device includes a light module, emitting light and receiving light reflected from a recording medium, and a solid immersion lens (SIL) member disposed in an optical path between the light module and the recording medium. The SIL has a planar surface facing the recording medium and a plurality of elliptically curved surfaces opposite the recording medium. The elliptically curved surfaces have different radii of curvature arranged symmetrical with respect to a central axis for focusing the incident light to form a tight beam spot on a recording plane of the recording medium.

Abstract: An optical viewfinder system comprising two optical elements, and a field stop or a reticle, to provide an image of a scene to a viewer, and further comprising a diffractive optical element to provide a clear, stationary image of the field stop or reticle to the viewer.

Abstract: Disclosed is a tunable multispectral optical apparatus for forming a spectrally processed image of a scene having finite angular extent or alternatively a point source of light, both of which may include multispectral components. A spatial filter is selectively positioned between a hybrid fore-optic and a hybrid reimaging optic, both of which include a diffractive optic. Spectral selectivity is obtained by proper positioning of the spatial filter relative to the intermediate image formed by the hybrid fore-optic before impinging on the hybrid reimaging optic. The tunable multispectral optical apparatus of the present invention may take the form of a bandpass filter or a bandstop filter depending only on the choice of spatial filter--blocking or passing selective wavelength components of the intermediate image.

Abstract: A triplet lens system composed of a first positive lens element, a second negative lens element and a third positive lens element. At least one lens surface is provided with a blazed zonal structure having a function of a positive diffractive lens.

Abstract: A method and apparatus for reading bar codes or other images while reducing or eliminating the need for self-generated illumination. An image reader is preferably embodied as a handheld unit and comprises an efficient optical collection system including an aperture with a high aspect ratio and/or a multi-focal lens or lenses. An optically transmissive spacer affixed to the front of the handheld unit allows ambient light to be collected at close range, and a diffuser may be used to reflect ambient light from the handheld unit to provide additional illumination at close range. A masked CCD detector with rectangular pixels receives collected light and is coupled to an adaptive exposure circuit for preventing saturation of the CCD detector at high illumination levels. A correlated double sampling circuit coupled to the adaptive exposure circuit rejects common mode noise and allows operation in lower light levels.

Abstract: A diffractive homogenizer is provided for receiving a beam of laser energy and producing a desired illumination pattern in a target plane. The homogenizer is made up of a plurality of diffractive sub-elements, each of which contributes to all or a portion of the desired image. By combining the contributions of many sub-elements to form the final image, a homogenizing effect is realized. In preferred embodiments, the sub-elements are designed to compensate for the finite spatial coherence of the incident laser beam and to control the numerical aperture distribution of the transmitted light. Each sub-element is composed of a large number of discrete pixels, each of which alters the phase of radiation passing therethrough by a selected amount. The pixel arrangement is chosen, using computer modeling and optimization techniques, such that the interference pattern created by the collective pixels in a sub-element makes up the desired image (or a portion thereof).

Abstract: An optical arrangement, in particular for use as a transmitting and/or receiving optical system in optoelectronic sensors, comprises at least one diffractive optical element integrated into transparent material, with the unit formed by the transparent material and the diffractive optical element having at least two different functions such as, for example, image forming functions, polarization, beam division, beam forming, beam shaping and/or the provision of a subaperture.

Abstract: A zoom lens system has the first and second lens units. During zooming from a wide-angle end to a telephoto end, the lens units are moved to decrease a distance therebetween. The first lens unit has a positive refractive power. The second lens unit has a negative refractive power. The zoom lens system is provided with at least one surface having a power to diffract light.

Abstract: An optical system that can be used in an optical imaging system and displays good imaging performance with corrected chromatic aberration without increasing the number of lenses is provided by employing a lens surface with a diffractive effect. The optical system uses a lens with a concave incident surface and positive refractive power. A grating element surface 40 with positive refractive power is formed on at least one surface of the lens. The surface on which the grating element is formed is an aspherical surface with a radius of curvature that becomes bigger with increasing distance from the optical axis.

Abstract: A free space imaging system utilizing a doublet form of optic. The doublet is configured with two large Fresnel lenses configured such that their echelon groove components are mutually oppositely disposed within the optical path of the system. The method includes an arrangement wherein the output focal plane deliberately is curved and generated with a relatively wide field of view to evoke an emulation of three-dimensionality.

Abstract: A two-focal-point pickup device capable of suppressing the generation of glitch or bump in reproduced signal. The optical pickup device irradiates a light beam emitted from a light source onto an optical recording medium to form a light spot on a track of a recording surface of the optical recording medium to read the optical recording medium while controlling the position of the light spot relative to the track of the recording surface. The optical pickup device includes a converging lens section coaxially disposed in an optical axis of the light beam to converge the light beam onto the recording surface; and a hologram lens section coaxially disposed in the optical axis of the light beam to diffract the light beam.

Abstract: A method and apparatus for reading bar codes or other images while reducing or eliminating the need for self-generated illumination. An image reader is preferably embodied as a handheld unit and comprises an efficient optical collection system including an aperture with a high aspect ratio and/or a multi-focal lens or lenses. An optically transmissive spacer affixed to the front of the handheld unit allows ambient light to be collected at close range, and a diffuser may be used to reflect ambient light from the handheld unit to provide additional illumination at close range. A masked CCD detector with rectangular pixels receives collected light and is coupled to an adaptive exposure circuit for preventing saturation of the CCD detector at high illumination levels. A correlated double sampling circuit coupled to the adaptive exposure circuit rejects common mode noise and allows operation in lower light levels.

Abstract: A lens system having a reduced number of injection-molded singlet lens elements with at least one diffractive surface to control axial and lateral chromatic aberrations is disclosed. In one embodiment, the diffractive surface is placed on the first surface of the third lens, which is closest to the image plane. An opaque spacer provides suppression of stray light from reaching the image plane.

Abstract: The invention has for its object to reduce the overall length of a single lens using a diffractive optical element, and provides a diffractive optical element applicable to an optical system for cameras such as silver salt cameras, and electronic cameras, in which both surfaces of the single lens are constructed of diffractive surfaces, are plane surfaces or have curvature, and comprise diffractive surfaces having, in order from a subject side thereof, positive power and positive power, positive power and negative power, and negative power and positive power.

Abstract: An optical instrument is described in which a diffractive element (25) is located at a focal or image plane (3) of the instrument and the diffractive element (25) is effective to produce an array (6) of a plurality of exit pupils at a viewing position for the instrument and thereby to form an enlarged exit pupil for the instrument.

Abstract: The laser transfer machining apparatus comprises a shaping unit for shaping the laser beam so that the laser beam has a beam pattern which corresponds to a desired pattern to be machined in the object to be machined and a generating unit disposed separately from the shaping unit for simultaneously generating a plurality of laser beams each having the beam pattern from the laser beam shaped by the shaping unit. The generating unit is adapted to emit the plural laser beams while simultaneously defining a plurality of radiation directions of the generated plural laser beams to the object to be machined. The laser transfer machining apparatus can provide a high efficiency of utilization of light and reduce the time required for machining. Furthermore, the laser transfer machining apparatus can utilize a laser with a relatively low spatially coherence such as an eximer laser.

Abstract: A soft aperture allows gradual attenuation of a light beam dependent upon its location away from the center of a diffractive optical element. Such an optical element may be provided by decreasing a number of phase levels, increasing a number of phase levels, increasing a density of metal patches or diffractive gratings, or decreasing a blaze height and/or duty cycle, all radially from the center. Alternatively, the soft aperture may be defined by a photolithographic process. Such a soft aperture is particularly useful in aiding circularizing of an elliptical light beam. The soft aperture may be used alone or integrated with other optical elements.

Abstract: An illumination system that comprises a light source, and, disposed in an optical path between the light source and the surface, converging imaging optics, and a diffractive array generator. The diffractive array generator preferably includes a two-dimensional periodic array of multi-level topological features.

Abstract: A binary-type optical diffraction device having the excellent capability of antireflection includes a step structure by which lens elements of a Fresnel lens are approximated. The surface of the steps formed on a substrate is entirely covered with a thin film having a flat surface. The height of each step and the refractive index of the thin film are selected so that the antireflection conditions for the respective steps are satisfied and thus the intensity of the reflected light rays is minimized.

Abstract: A zoned lens comprises at least two adjacent zones (16) formed such that the differences between the optical path lengths between an object point and a pixel of light beams extending through these two adjacent zones (16) of the lens (15) are at least equal to half the coherence length of the light used, preferably at least equal to the coherence length of the light used.

Abstract: An improved endoscope comprises an objective including a diffractive optical element juxtaposed to a solid-state imaging element at the distal tip of the endoscope. An inexpensive halogen lamp at the proximal end of the endoscope is employed as the illumination source. A fiber-optic bundle carries light to the distal tip of the endoscope, where diffractive optical elements are provided to disperse light, illuminating the field of view.

Abstract: The invention provides a compact yet high-zoom-ratio zoom lens system for use with lens shutter cameras, which is well corrected for aberrations albeit being made up of a small number of lenses. The zoom lens comprises a first lens group G1 of positive refracting power, a second lens group G2 of positive refractive power and a third lens group G3 of negative refracting power. The lens groups move for zooming from the wide angle side to the telephoto side, with a separation between the first and second lens groups becoming wide and a separation between the second and third lens groups becoming narrow. At least one lens group has a diffractive surface therein, and satisfies 1.8<.beta..sub.T /.beta..sub.W <4.0 where .beta..sub.T and .beta..sub.W are transverse magnifications of the lens group having a diffractive surface at the wide-angle end and the telephoto end of the lens system.