Showing papers on "Holographic optical element published in 2000"

A forgettable near eye display

Abstract: This paper describes a very light wearable display so light that you can forget that you are actually wearing it. It is a virtual image display device which consists of a prism with two total internal reflection surfaces and a holographic optical element. The sophisticated display is only 3.4 mm thick, weighs 25 grams, and has high transparency, providing comfort to wear all day long. Also, its size and weight is small enough to be put on cellular phones. Optical design and experimental results are described.

Projection screen apparatus including holographic optical element

Abstract: A screen apparatus includes a holographic optical element and a diffuser. The holographic optical element may be constructed using standard techniques known in the field of holography. The holographic optical element may be used to replace a typical Fresnel lens used in projection screen apparatuses. In operation, the holographic optical element receives image light from an image engine or projector and redirects the image light to the diffuser for scattering. The holographic optical element can be designed to substantially collimate, converge, or diverge the image light. The combination of the holographic optical element and the diffuser provides improved illumination uniformity that can be perceived by a viewer as the viewer moves in directions transverse to the screen apparatus. The screen apparatus may be designed to provide improved illumination uniformity to optimized or optimal locations in a viewing region. The screen apparatus may be advantageously employed in display apparatuses.

Display device within finder

Abstract: PROBLEM TO BE SOLVED: To provide a display device within a finder whose cost is made low. SOLUTION: The finder display device performing display within a finder 4 is equipped with a diffraction optical element 1 (ESHOE: Electrically Switchable Holographic Optical Element) arranged near the scheduled image formed surface of an objective lens and capable of realizing electric switching, a light projecting part 3 projecting illuminating light toward the element 1, and a control part 2 electrically controlling the projecting part 3 and the element 1. The display device is constituted so that illuminating light projected by the projecting part 3 may be directed to the finder 4 as display light through the element 1 in accordance with the control of the control part 2.

Method and apparatus for positioning subjects using a holographic optical element

Abstract: A system and method of positioning an eye of a subject at a selected point in space uses a holographic optical element containing indicia. The indicia are selectively visible to a user when the user is outside a volume surrounding the selected point and direct the user toward the volume. This system can be used with a camera to take an image of the eye from which the subject can be identified.

Retinal projection display using holographic optical element

Abstract: We have already proposed that we could realize the see- through HMD by using the Holographic Optical Elements (HOEs). The HMD using HOE we proposed so far is used the Maxwellian View, which is the direct projection on the human retina. When we see something by the Maxwellian View, we don't need the focusing of the crystalline lens (ocular accommodation) because the depth field is extremely wide. We have been estimated the optical characteristics of this HOE by using still images on the slide mount. In this report, we will show the prototype of Retinal Projection Display, which can provide us the electrical dynamic images on the electrical spatial light modulator.

Optical Pickup Employing a Hologram-Laser-Photodiode Unit.

Abstract: In this paper we review the holographic optical element technology applied to compact disc (CD), digital versatile disc (DVD) and mini disc (MD) pickups. Using this technology, the number of optical components and the size and weight of a CD pickup are successfully reduced and its reliability is improved, because many functions of the optical components are integrated into a hologram-laser-photodiode unit. For DVD application, the focus detection for a dual-layer disk and the differential phase detection (DPD) method are realized by the hologram technology. Our unique two-segment DPD method shows more stable characteristics than the conventional DPD method. An integrated MD hologram pickup is also developed with an optical waveguide device that functions in magneto optical (MO) signal detection.

Development of Optical Pickup for Digital Versatile Disc Using Two-Wavelength-Integrated Laser Diode

Abstract: A digital versatile disc (DVD)-and compact disc (CD)-compatible optical pickup using a two-wavelength-integrated laser diode (TWIN-LD) has been developed. The TWIN-LD has two emission points in one chip, one for the red laser beam to read out signals from DVDs and the other for the IR laser beam to read out signals from CDs that are arranged along the active layer. With the application of a TWIN-LD to the optical pickup, the necessity for four optical components, namely, a laser diode, photodetector, holographic optical element and dichroic prism, is avoided in comparison with conventional optical pickups. This paper discusses some key points for designing an optical system using a TWIN-LD, and the results of the experiments appling the optical system to an optical pickup 7.3 mm in height.

Method for producing holographic optical element comprising primary and complementary holograms and associated methods for establishing authenticity of element used as security device

Abstract: A method is provided for producing a holographic optical element that is comprised of at least one primary hologram (as defined herein) and at least one complementary hologram (as defined herein). The holographic optical element is useful as a security device, since it is relatively easily produced and yet is uncopyable in total. Also disclosed are methods for establishing the authenticity of the holographic optical element.

Projection display employing switchable holographic optical elements

Abstract: The present invention relates to an optical system for use in a projection display system. The optical system, in one embodiment, includes a first electrically switchable holographic optical element (ESHOE) and a light deflector. The first ESHOE operates between active and inactive states and includes oppositely facing front and back surfaces. In the inactive state, the first ESHOE transmits first bandwidth light received on the front surface without substantial alteration. In the active state, the first ESHOE diffracts first bandwidth light received on the front surface, the diffracted first bandwidth light emerging also from the front surface. The light deflector receives first bandwidth light diffracted by the first ESHOE. In response, the light deflector deflects this diffracted first bandwidth light. The first ESHOE and the light deflector are positioned such that first bandwidth light transmitted through the inactive first ESHOE without substantial alteration can illuminate a first surface area while first bandwidth light diffracted by the active first ESHOE and subsequently deflected by the light deflector can illuminate a second non-overlapping.

Beam-shaping elements for holographic applications

Abstract: Recording holographic optical elements usually requires a good illumination uniformity as well as a spherical or plane phase. To fulfill the uniformity demand, an expansion of the Gaussian beam is necessary. This leads to a loss of intensity connected with an essential extension of the recording time. Alternatively, the recording efficiency can be increased by using a beam transformation the beam from a Gaussian into a top hat intensity distribution. We designed, realized and tested a setup for a more efficient hologram recording which can be used for full color application. The heart of the setup is a refractive beam shaping element fabricated by a gray tone lithography and proportional transfer into quartz glass. The beam shaping element shows a conversion efficiency of $GTR99,5% (like a refractive lens) in the whole visible spectral range and an intensity uniformity <5%RMS.

Remote detection of Raman scattering by use of a holographic optical element as a dispersive telescope.

Abstract: We describe the retrieval of nighttime lidar profiles by use of a large holographic optical element to simultaneously collect and spectrally disperse Raman-shifted return signals. Results obtained with a 20-Hz, 6-mJ/pulse , frequency-tripled Nd:YAG source demonstrate profiles for atmospheric nitrogen with a range greater than 1 km for a time average of 26 s.

Application Specific Integrated Lenses and filters for microdisplays using Electrically Switchable Bragg Grating technology

Abstract: A new solid state optical device technology - Electrically Switchable Bragg Grating (ESBG) technology - based on holographic polymer dispersed liquid crystal (H-PDLC), is being applied in Application Specific Integrated Lenses (ASILs) and Filters (ASIFs). These devices, also referred to as E-Lenses and E-Filters, are essentially stacks or laminates of intrinsically thin ESBGs encapsulated using transparent substrates. ASILs and ASIFs provide a basic colour sequential switching technology that directly challenges optical mechanical solutions such as color wheels. ASILs and ASIFs have no moving parts; they are completely solid state and silent in operation. They offer the benefits of holographic optical elements in terms of being able to compress conventional optical systems into compact and lightweight form factors. Since their switching speed is fast enough for colour sequential operation, colour dispersion can be controlled. They will have a major impact on the complexity and cost of a broad gamut of microdisplay applications, including projection and near-eye. The paper reviews the role of ASILs and ASIFs in both areas, with reference to design concepts currently in development.

Planar-integrated interferometric sensor with holographic gratings

Abstract: Planar integration of various optical systems appears for some years as a way to reduce alignment problem and to build small size, robust and monolithic devices. An original planar integrated interferometric sensor is presented in this paper. It is based on the separation and control of polarization states in a substrate mode holographic system in order to obtain the optical path difference between two scanning spots. A unique planar system is used for projection of the spot and for recombination of probe beam reflected on the tested surface. The monolithicity and the differential nature of the element lead to a very good insensitivity to external vibrations. The sensor is a multilayered structure composed of a reflective polarizing holographic element sandwiched between two planar substrates. Probe beams are coupled in and out of the system by diffraction on a reflective Substrate Mode Hologram that constitutes a fourth layer. These two types of holographic elements are recorded in high index modulation photopolymer: OmnidexTM HFR-600 from DuPont. Design, realization and application are demonstrated and discussed.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Adaptive systems in speckle-pattern interferometry

Abstract: The concept of adaptivity in television holography is discussed, and various realizations of adaptivity are presented. In one possible variation, functions of the components of the optical arrangement may be changed to adapt them to measurement conditions. An additional peculiarity of the technique is that reference waves are produced by holographically reconstructed virtual images. A method, believed to be new, is introduced for synthesizing the phase front of the master object beam that is produced by a simple holographic optical element and is used as a smooth or a speckled reference beam in the electronic speckle-pattern interferometer. An adaptive interferometer is presented as a measuring device for various measuring tasks. Selected applications are shown, demonstrating different aspects of adaptivity.

Apparatus and method for receiving optical telecommunication transmissions by using a holographic optical element

Abstract: A holographic optical element (HOE) device useable for an optical receiver system has a first element having first and second surfaces, with the first surface being positionable to face incident light rays. The incident light rays can comprise laser light having data modulated thereon. An emulsion material is disposed over the second surface of the first element and has a recorded interference pattern that diffracts the incident light rays that pass through the first element. A second element overlies the emulsion material and is structured to pass resulting light rays derived from the incident light rays and diffracted from the recorded interference pattern. A plurality of reflective elements are positioned adjacent to the first and second elements. The reflective elements fold the resulting light rays within the second element, thereby allowing a reduction in separation length between the emulsion material and receiver electronics.

Multiviewpoint autostereoscopic 3d display system based on volume holographic optical element

Abstract: PURPOSE: A multiviewpoint autostereoscopic 3D display system based on VHOE(volume holographic optical element) is provided to synthesize MSI(multiplexed stripe images) in realtime and to realize an ultra fast realtime random access. CONSTITUTION: A beam splitter(20) splits a laser beam from a laser into a reference beam and an object beam. A first SLM(spatial light modulator)(24) is positioned on an optical path of the reference beam, forms a mixture shape of multiviewpoint images by the radiation due to the reference beam to form spatial multiplexed strip pattern optical modulated images under the state that input patterns of light strength modulation shape corresponding to MSI are formed for display with parallax barrier shape. A second SLM(25) is positioned on an optical path of the object beam, forms a mixture shape of multiviewpoint images by the beam radiation to perform spatial multiplexing for the mixed shape under the state that lattice shape patterns corresponding to the multiviewpoint images are formed for display with parallel barrier shape. A first reflector(31) is positioned between the beam splitter(20) a first focusing lens(41) for orienting the beam toward the beam splitter. A second reflector(32) is positioned between a second focusing lens(42) and an optical refraction recording medium(50). A third reflector is rotatably positioned between the second SLM(25) and a third focusing lens group(43,44). A rotator(60) for the third reflector provides rotation force for rotating the third reflector(33). A phase converter(23) converts vertical deflection wave from the beam splitter(20) and the laser into horizontal deflection waves.

Optical pickup for use with a recording medium

Abstract: An optical pickup is provided which includes a light source and an objective lens for converging incident light from the light source onto a recording medium. The objective lens is arranged to be movable in radial and vertical directions of the recording medium. A holographic optical element (HOE) for changing a traveling path of the incident light is positioned along an optical path between the light source and the recording medium, and has first and second diffraction plates which are divided along a first boundary line and have different diffraction patterns. A photodetector has first and second divided plates which are divided along a second boundary line which is perpendicular to the radial and vertical directions of the recording medium. The first and second divided plates receive light passed through the first and second diffraction plates after being reflected from the recording medium. The first boundary line of the HOE is arranged at a predetermined angle with respect to the radial direction of the recording medium, such that the amount of light received by the first and second divided plates is equal to each other when the center of the objective lens is properly located on the optical path, and amount of light received by the first and second divided plates is different from each other when the center of the objective lens is deviated from the optical path.

Diffractive focusing lens for infrared detector

Abstract: A focussing element (50) is incorporated in an infrared detector, the focussing element (50) being in the form of a series of grooves (54) which form one or more diffractive optical elements. The diffractive optical elements may have spatial filtering properties and may also be arranged to correct chromatic aberrations. Alternatively, the focussing element may comprise a holographic optical element.

Method and apparatus for correcting aberrations in photon collection devices

Abstract: A cover plate on a holographic optical element (HOE) device corrects for aberrations, such as spherical aberrations. The HOE device includes an emulsion material, having a recorded interference pattern that can perform diffraction, sandwiched between a first element and a second element, wherein the second element functions as the cover plate. One of the surfaces of the second element is aspheric to correct for aberrations. The aspheric shape of the surface adds approximately equal and approximately opposite aberrations associated with light rays diffracted by the recorded interference pattern, thereby substantially improving focus.

Color multiplex imaging 3D display system using holographic optical element

Abstract: The authors propose new 3D display system using Holographic Optical Element (HOE) without glasses. The proposed HOE is used as holographic screen in this system. The HOE of proposed method can reconstruct white light in white illumination light. Namely, this HOE can reconstruct color images. The HOE has diffraction efficiency issue. However, we solved this issue, because we considered the Bragg condition when we made the HOE.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Daytime holographic Raman lidar system

Abstract: We present a holographic Raman lidar system, which can provide temperature profiles of the atmosphere. The Raman lidar has the potential to operate continuously over a 24 hr period, with a predicted accuracy of 1% at altitudes greater than 20 km. The distinguishing feature of our lidar that allows 24 hr measurements is the holographic optical element. The holographic optical element can resolve individual rotational Raman lines at high efficiency. Furthermore, this high resolution substantially increases the signal to noise of the lidar system, thereby allowing daytime measurements with out appreciable increase in error.

System and method for controlling the selectivity of a holographic memory system

Abstract: A system and method for controlling the selectivity function in a holographic memory system that permits more rapid location and retrieval of holographically stored data The system and method direct a reference beam through a filter such as, for example, an aperture, to bandwidth limit the beam before the beam illuminates a holographic optical element having stored therein a hologram of a reference beam

Dual-Layer Volume Holographic Optical Elements for Three-Wavelength Optical Disk Pickup

Abstract: A dual-layer volume holographic optical element is proposed as a beam-splitting element for a three-wavelength (?=0.4 ?m, 0.65 ?m and 0.8 ?m) optical disk pickup. We fabricated it for normal incidence using photopolymer film via an inexpensive laminate process. It is demonstrated that it exhibited excellent wavelength selectivity (extinction ratio ?~100) with a high diffraction efficiency of 99.7%. This element could be a key device in a next-generation multi wavelength optical disk pickup.

Polarized diffractive optical element design for a multibeam optical pickup head

Abstract: This paper addresses the design and construction of an interesting polarization-switched diffractive optical element (DOE) that generates multiple beams incident on the disk and acts as a beamsplitter and servo-generating element for light returning from the disk. In this way, data speed is increased proportional to the number of beams on the disk, and, by combining three functions into a single optical element, allows a more compact and lightweight pickup to be realized. The polarization-switched DOE is constructed as a sandwich of two pieces of some birefringent material, with one rotated by 90 degrees relative to the other so that the ordinary and extraordinary axes are interchanged, and with a common index-match layer between them. A diffractive pattern is etched into each of the two birefringent pieces. Linearly polarized light traveling from the laser towards the disk is diffracted into multiple beams by one of the diffractive patterns while experiencing no diffraction from the other. Travelling the roundtrip from the DOE to the disk and back to the DOE, the light traverses a quarter-wave retarder two times thereby rotating its polarization direction by 90 degrees. It now experiences no diffraction from the multiple beam diffraction layer, but is diffracted by the second diffraction layer, which steers it onto the photodetectors and alters the beam to create useful focus and tracking error signals. This design is important in that it provides a way for two diffractive surfaces, each acting independently with high efficiency on orthogonal polarizations of light, to be combined into a single element. Implementation and application to a multiple-beam holographic pickup head module are presented.

54.5: Holographic Screens for 3 Dimensional Image Projection

Abstract: color transmission type holographic screen having a size of 40cm X 60cm are developed recently at Korea Institute of Science and Technology. This screen can be operated in reflection mode by adding a mirror at its back. This operation extends viewing angle of the screen to be more than 30degree. This wide viewing angle permits the screen to be operated in viewer tracking regime. By mosaicking the screens, a 120cm X 80cm screen is made. The mosaicked screen shows a good image performance. Introduction screen has been developed to use as an image projection screen for forming viewing zones for the projected images(1). It is a kind of holographic optical element(HOE)s which has the properties of a spherical mirror or a lens + a diffuser. Since HOE is basically a spectral selective component, full color images can not be projected on the holographic screen(2), unless a specific optical recording set-up is used or a special development process is developed. One good example of the screen is the image combiner in Head Up Display for airplanes(3). It is tuned to have the maximum diffraction efficiency for the spectral range corresponding to that of the image display device used for the Display, i.e., CRT. This means that the screen has an uniform period fringe structure. To make the screen has a wide spectral response comparable to visible spectral range, it is necessary to make the screen have a variable period fringe structure. Based on this concept, Korea Institute of Science and Technology(KIST) developed a full color transmission type holographic screen with use of a long slit type diffuser as an object(4). The screen creates a full color viewing zone for images projected from a projector by making the reconstructed diffuser image for each spectral com ponent of the images overlap partially in space. The viewers can perceive the full color images displayed on the screen through the viewing zone. The advantages of the holographic screen compared with popularly used optical plates to form viewing zones, such as Lenticular, Parallax Barrier and Integral Photography plates and Fresnel lens(5) are such that resolution and depth of the viewing zone of the screen are higher and more, respectively. However, making larger size screen with full color capability is difficult due to problems related with optimizing the recording set-up to minimize aberrations and exposition time, and changing viewing zones following to the viewer's movement. It found that the problems could be solved by mosaicking smaller size screens and by operating the screen in a reflection mode. This reflection mode operation allows the angular selectivity of the screen to be two times of that of transmission mode. In this paper, some features of the full color transmission type holographic screens developed at KIST are described.

Inspection device containing a switchable holographic optical element

Abstract: An inspection device (10) is disclosed that employs a switchable holographic optical element (SHOE) (28). In one embodiment, the inspection device, or a portion thereof, may include a tube (24) extending between first and second ends, a SHOE (28), and a conductor (38) coupled to the SHOE. The SHOE is switchable between active and inactive states. When in the active state, the SHOE diffracts a bandwidth light incident thereon. When in the inactive state, the SHOE transmits a bandwidth light incident thereon without substantial alteration. The conductor, a portion of which is contained within the tube between the first and second ends thereof, transmits control signals or voltages to the SHOE.