568results about "Hologram recording material" patented technology

One embodiment provides an apparatus for displaying an image comprising: a first optical substrate comprising at least one waveguide layer configured to propagate light in a first direction, wherein the at least one waveguide layer of the first optical substrate comprises at least one grating lamina configured to extract the light from the first substrate along the first direction; and a second optical substrate comprising at least one waveguide layer configured to propagate the light in a second direction, wherein the at least one waveguide layer of the second optical substrate comprises at least one grating lamina configured to extract light from the second substrate along the second direction; and the at least one grating lamina of at least one of the first and second optical substrates comprises an SBG in a passive mode.

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.

A hologram has a hologram element 3 containing a photopolymer and a cover film 22 and cover plate 21 which cover its surfaces. An adhesive 1 is used for bonding the cover film to the hologram element and the cover plate to the hologram element. The hologram has excellent humidity resistance, chemical resistance, solvent resistance and heat resistance, prevents coloration, can maintain its holographic properties and allows easy repositioning of the hologram element.

A holographic recording medium exhibiting a high recording sensitivity without execution of reduction treatment. A system records information on the holographic recording medium by using a gating light within a wavelength band causing less optical damage to the holographic recording medium. The holographic recording medium includes a single crystal of lithium niobate (LiNbO₃) or lithium tantalate (LiTaO₃) containing Mn as a dopant.

A method for the production of a holographic sensor wherein the holographic recording material forming the sensitive element is a polymer matrix, which comprises diffusing into the matrix one or more soluble salts that undergo reaction in situ to form an insoluble sensitive precipitate; and recording a holographic image. This method allows the production of a holographic sensor wherein the holographic recording material forming the sensitive element is an insoluble polymer film.

Holographic storage media including a substrate and a dye material capable of undergoing a photo-induced change are disclosed. Data may be written into the holographic storage media using light of one wavelength and read using light of a different wavelength.

The objective of the present invention is providing a method for fabricating high quality diffractive waveplates and their arrays that exhibit high diffraction efficiency over large area, the method being capable of inexpensive large volume production. The method uses a polarization converter for converting the polarization of generally non-monochromatic and partially coherent input light beam into a pattern of periodic spatial modulation at the output of said polarization converter. A substrate carrying a photoalignment layer is exposed to said polarization modulation pattern and is coated subsequently with a liquid crystalline material. The high quality diffractive waveplates of the present invention are obtained when the exposure time of said photoalignment layer exceeds by generally an order of magnitude the time period that would be sufficient for producing homogeneous orientation of liquid crystalline materials brought in contact with said photoalignment layer. Compared to holographic techniques, the method is robust with respect to mechanical noises, ambient conditions, and allows inexpensive production via printing while also allowing to double the spatial frequency of optical axis modulation of diffractive waveplates.

Holographic and diffractive security devices and documents carrying security devices as well as system, apparatus, and method for making and using security devices. Security devices provide at least one type of security feature in form of secret, hidden, or covert security feature, not visible to a normal unaided human eye. Covert security features may be any graphic or symbolic representation. One or multiple security features may be provided on any single security device in any combination. Covert feature is revealed either when a decoder device is used with the security device, or when the security device is oriented and viewed in predetermined manner. Embodiments may provide a second overt or non-covert security device in the form of a diffractive or holographic image or graphic that is visible to the unaided eye without use of any decoder or special viewing conditions.

Transmission and reflection type holograms may be formed utilizing a novel polymer-dispersed liquid crystal (PDLC) material and its unique switching characteristics to form optical elements. Applications for these switchable holograms include communications switches and switchable transmission, and reflection red, green, and blue lenses. The PDLC material of the present invention offers all of the features of holographic photopolymers with the added advantage that the hologram can be switched on and off with the application of an electric field. The material is a mixture of a polymerizable monomer and liquid crystal, along with other ingredients, including a photoinitiator dye. Upon irradiation, the liquid crystal separates as a distinct phase of nanometer-size droplets aligned in periodic channels forming the hologram. The material is called a holographic polymer-dispersed liquid crystal (H-PDLC).

A method for preparing electro-optical polymer-liquid crystal photonic crystals, comprising: disposing between at least two optically transparent electrode plates, a polymer-dispersed liquid crystal material that comprises, before exposure:

• • (a) a polymerizable monomer comprising at least one acrylate;
  • (b) a liquid crystal;
  • (c) a chain-extending monomer;
  • (d) a coinitiator;
  • (e) a photoinitiator; and
  • (f) a long chain aliphatic acid;
  • and exposing this polymer-dispersed liquid crystal material to light in an interference pattern.

A holographic recording apparatus having a source of illumination, a master hologram containing at least one hologram lamina overlaying, a copy substrate containing a holographic recording medium, and a voltage generator for applied a voltage across at least one of the master hologram and the copy substrate. The master hologram diffracts the illumination light into zero order light and diffracted light which interfere in the copy substrate to form a copy of the master hologram. The source of illumination is applied for a predefined exposure time during which the voltage varies the refractive index modulation of at least one of the master hologram and the copy hologram.

A method of producing a hologram element is disclosed that is able to prevent spread of a polymerization reaction and light leakage during exposure with interference light, and improve productivity in mass production. The hologram element is for transmitting, reflecting, diffracting, or scattering incident light, and includes a pair of substrates, an isolation member between the substrates that forms an isolated region, and a photo-sensitive recording material sealed in the isolated region. The hologram element includes a periodic structure formed by exposing the recording material to interference light. The interference light is generated by two or more light beams, or by using a master hologram. The recording material is formed from a composite material including a polymerized polymer or a polymerized liquid crystal. The periodic structure is formed by exposing the recording material to the interference light to induce the polymerization reaction and phase separation in the composite material.

Iterating an optical phase conjugation of ultrasonically-modulated diffuse light emitted by a scattering medium includes illuminating the scattering medium with a light beam from a coherent light source, modulating the diffuse light transmitted through the scattering medium with an ultrasonic wave focused on a region of interest within the scattering medium, fixing a hologram, retro-reflectively illuminating the scattering medium using a phase-conjugated copy of the diffuse light that was ultrasonically modulated, moving the ultrasonic focus, and iterating until light is focused on the final target.