251 results about "Volume hologram" patented technology

PCT No. PCT/US95/02155 Sec. 371 Date Dec. 22, 1997 Sec. 102(e) Date Dec. 22, 1997 PCT Filed Feb. 21, 1995 PCT Pub. No. WO95/22804 PCT Pub. Date Aug. 24, 1995A method and ultra-compact system has been developed for illuminating and detecting the surface topography of an object such as the finger (4) of an individual. The system (8) is capable of producing high-contrast images which can be electronically transmitted in real-time, or stored using electronic or photographic recording devices. Light traveling within a light transmitting substrate (2) is redirected by a slanted-fringed light diffractive grating preferably embodied within a volume hologram (3). The volume hologram (3), either of the reflection or transmission type, is attached to the light transmitting substrate (2). and functions to diffract light striking thereupon and illuminate an object having topographical surface structure. After being spatially and intensity modulated in accordance with topographical details of the illuminated object, the insulated light passes back through the light transmitting substrate (2) and the volume hologram (3), onto an image detection array. for subsequent analysis. Each of the disclosed embodiments has a compact geometry suitable for use in diverse object identification applications.

There is provided an optical device including an optical waveguide upon which a group of parallel light beams different in traveling direction from each other are incident and from which the group of parallel light beams go out after propagated by repeated total reflection through it. The optical waveguide includes a first reflection-type volume hologram grating, and a second reflection-type volume hologram grating. The pitches of interference fringes on the hologram surfaces of the first and second reflection-type volume hologram gratings are equal to each other. In at least the second reflection-type volume hologram grating, the angle formed between the interference fringes and hologram surfaces are varied continuously or stepwise within the hologram in relation to the main incident light beam so as to meet the Bragg condition. Therefore, it is possible to reduce the unevenness of color and brightness due to angles of view.

An optical device includes a light guide plate, and first and second reflective volume hologram diffraction grating members. The first member has interference fringes extending from therewithin towards surfaces thereof and arranged at an equal pitch. Each interference fringe and each surface of the first member form an inclination angle therebetween. The first member has the following conditions. (a) In an outer region positioned farther away from the second member than a minimum inclination angle region having a minimum inclination angle, the inclination angles of the interference fringes increase with increasing distance from the minimum inclination angle region. (b) In an inner region positioned closer to the second member than the minimum inclination angle region, the inclination angles of the interference fringes include a maximum inclination angle in an inner area disposed adjacent to the minimum inclination angle region and decrease with increasing distance from the minimum inclination angle region.

A new photopolymerizable material allows single-step, fast recording of volume holograms with properties that can be electrically controlled. Polymer-dispersed liquid crystals (PDLCs) in accordance with the invention preferably comprise a homogeneous mixture of a nematic liquid crystal and a multifunctional pentaacrylate monomer in combination with photoinitiator, coinitiator and cross-linking agent. Optionally, a surfactant such as octancic acid may also be added. The PDLC material is exposed to coherent light to produce an interference pattern inside the material. Photopolymerization of the new PDLC material produces a hologram of clearly separated liquid crystal domains and cured polymer domains. Volume transmission gratings made with the new PDLC material can be electrically switched between nearly 100% diffraction efficiency and nearly 0% diffraction efficiency. By increasing the frequency of the switching voltage, switching voltages in the range of 50 Vrms can be achieved. The optional use of a surfactant allows low switching voltages at lower frequencies than without a surfactant. In an alternative embodiment, a PDLC material in accordance with the invention can be utilized to form reflection gratings, including switchable reflection gratings. In still further embodiments, a PDLC material in accordance with the invention can be used to form switchable subwavelength gratings. By further processing, static transmission, reflection, and subwavelength PDLC materials can be formed. In addition, PDLC materials in accordance with the present invention can be used to form switchable slanted transmission gratings suitable for switchable optical coupling and reconfigurable optical interconnects.

An observation optical system includes an image display element b 5, a relay optical system 6 having a plurality of lenses 4 and a first reflection-type volume hologram element (HOE) 8, and an eyepiece optical system having a second reflection-type HOE 9. The observation optical system is arranged along the face to the side head of the observer. The first reflection-type HOE 8 has a power and is configured to compensate for chromatic aberrations. The plurality of lenses is configured to compensate for decentered aberrations and chromatic aberrations. The second reflection-type HOE 9 is configured to exert power on bundles of rays and to compensate for chromatic aberrations. A light-transmitting plate 3 is sandwiched between the first reflection-type HOE 8 and the second reflection-type HOE 9. The light-transmitting plate 3 is configured so that light from the first reflection-type HOE 8 causes total reflection inside the light-transmitting plate 3 odd-numbered times equal to or greater than three times. These features provide an observation optical system that is so compact and lightweight as to be applicable to a head-mount-type virtual image observation apparatus, that provides a bright image with high resolution, and that is easily assembled.

An observation optical system comprises an image display element 5 and an eyepiece optical system which introduces an image formed by the image display element 5 to a center of an eye of an observer without forming an intermediate image, so as to allow the observer to observe the image as a virtual image. The eyepiece optical system is constructed and arranged to bend the optical axis using reflecting surfaces so as to be compact. The optical axis lies in a plane, with respect to which the optical system is formed symmetric. The optical system includes a prism 3 having an entrance surface 33, a plurality of curved reflecting surfaces 31, 32 and an exit surface 31. The reflecting surface 32 is provided with a volume hologram (HOE) 4. Whereby, it is possible to provide an image observation optical system which can be made compact enough to be usable as an image display unit for a cellular phone or a portable intelligent terminal, and which can achieve high image definition and wide field angle while controlling chromatic aberration of magnification to be small.

Provided is a photosensitive composition for volume hologram recording capable of forming a volume hologram recording medium that less shrinks upon curing in hologram recording (in hologram formation) and resists cracking. The photosensitive composition for volume hologram recording contains an alicyclic epoxy compound (A) represented by Formula (I); a thermal acid generator (B); a radically polymerizable compound (C); a radical polymerization initiator (D); and at least one epoxy compound (E) selected from the group consisting of compounds represented by Formula (1), epoxidized fatty acid esters, and epoxidized conjugated diene polymers.

A virtual image display apparatus includes an organic EL device that outputs light having one kind of wavelength band, a light guide member, and a reflection-type volume hologram that is disposed on a first face of the light guide member and diffracts and reflects light of a predetermined wavelength band of the light that has entered. The organic EL device includes an optical resonance structure that causes the above-mentioned light of one-kind wavelength band to resonate.