JP2002529790A - Head-mounted display device for viewing images - Google Patents

Abstract

(57) [Summary] A head-mounted display device for transmitting an image to a user's eye using a switchable holographic element is provided. The apparatus is an optical system configured to transmit image light to a user's eye, the system comprising a first switchable holographic optical system configured to operate in an active or inactive state. The element and the first switchable holographic optical element are configured to diffract incident light when operating in the active state and transmit the incident light substantially unaltered when operating in the inactive state. The optical system includes an optical system and a casing that can be mounted on the user's head such that at least a part of the optical system is provided inside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] Technical Field The present invention relates to display systems, and more particularly the head mount display system.

[0002] By BACKGROUND fast computer systems and small display devices than is encountered, the head-mounted display device has come to be used increasingly common. Generally, a head-mounted display device transmits an image from an image generator to a user's eyes. Since the device is mounted on the user's head, the video is projected only to the user and not to the surroundings. Head mounted display devices are widely available for military, industrial, and recreational uses.

[0003] Head-mounted display devices are particularly useful for transmitting computer images and for three-dimensional applications. For example, three-dimensional applications typically require sending clear images to each user's eye. Each image will represent a two-dimensional image that, when associated with another image by the user's eyes, causes a three-dimensional image to appear in front of the user's eyes. It is difficult to produce such an image for a large audience. Many spectators need special glasses to create a three-dimensional image.

[0004] Many existing head mounted display devices include an image generation system that is installed directly in front of a user's eyes. Older head mounted display devices typically use an opaque video generation system. Such an image generation system hinders the user from observing the surroundings while watching the image. More recently, by using a translucent or transparent image generation system,
It is possible to see surrounding parts while watching the image generated by the image generator. Such systems typically require that the video generation system be placed in front of the user's eyes. Such elements tend to make the front of the display device heavy. A display device having a heavy front tends to make the user feel uncomfortable. Placing the image generation system in front of the display device tends to put pressure on the user's head and cause fatigue. Many users will find it uncomfortable to use such a device for a few hours.

In order to avoid such a problem, the head mounted display device uses an image generator installed at a position that does not directly enter the field of view of the user. Then, an optical system is constructed, and an image is transmitted from the image generator to the eyes of the user. In this way, the weight and some optics associated with the image generator can be better distributed through the display device and over the user's head. However, in order to project an image on the user's eyes, a large number of optical elements must be installed around and in front of the user's eyes. These numerous optical elements not only transmit images to the user's eyes, but also assist in chromatic aberration, monochromatic aberration and distortion such as astigmatism, spherical aberration, coma, pincushion distortion, barrel distortion, keystone, etc. To be reduced. Many aberrations occur when images are transmitted through the various optical elements of the system. While these display devices will be weighted more favorably than head mounted video generator display devices, the presence of these optical elements still places considerable weight on the top surface of the user's eye .

[0006] It is desirable to provide a head mounted display device that minimizes the weight distribution of the image generator and optical elements, especially at the front of the device. This reduces fatigue associated with the device and allows the user to use the device for an extended period of time.

[0007] Most of the (DISCLOSURE OF THE INVENTION) above outlined problem is solved by the head-mounted device for projecting an image, such as with switchable holographic optical elements. In some embodiments, the optical generator is configured to receive an image provided by the image generator, define an optical path, and transmit light along the optical path from the image generator to the user's eye. A system is given. The optical system includes at least one switchable holographic optical element. The switchable holographic optical element is configured to operate in an active or inactive state. In the active state, the switchable holographic optical element is shaped to diffract incident light. In the inactive state, the switchable holographic optical element is formed such that incident light can pass through the switchable holographic optical element without substantial change.

In some embodiments, the switchable holographic optical element includes a holographic recording medium. The holographic recording medium includes a liquid crystal element and a photopolymer. In some embodiments, the holographic recording medium includes:
Includes monomers, dipentaerythritol hydroxyacrylate, liquid crystals, bridging monomers, coinitiators, and photoinitiator dyes.

In one embodiment, the hologram is recorded on a holographic recording medium.
For a transmission-type switchable holographic diffraction element, the recorded hologram is a transmission-type diffraction grating. For a reflective switchable holographic diffraction element, the recorded hologram is a reflective diffraction grating. The polymer-dispersed liquid crystal material undergoes phase separation to create areas that are densified by the liquid crystal droplets and areas where optically clear photopolymer is dispersed by the areas that are densified by the liquid crystal droplets. Depending on the process undergoing, either type of hologram is recorded.

[0010] In some embodiments, the optical system includes two holographic optical elements. The first holographic optical element is a reflection holographic diffraction element. 2
The holographic optical element is a holographic diffractive element. The reflection holographic diffraction element is placed in front of the user's eye. The transmission holographic diffraction element is located on the opposite side of the reflection holographic diffraction element. The transmission holographic diffraction element is configured to receive and transmit light to the reflective holographic diffraction element. The at least one holographic optical element is a switchable holographic optical element. In some embodiments, the reflection holographic diffraction element and the transmission holographic diffraction element are both switchable holographic optical elements.

In one embodiment, the image is a color image. When a color image is transmitted,
The switchable holographic optical element includes three holographic layers, each functioning on a primary color (ie, red, green, blue light). In embodiments where two holographic optics are used, both holographic optics have three holographic layers that function on the primary colors. When the holographic optical element is a switchable holographic optical element, each of the three holographic layers is independently switchable between an active state and an inactive state.

[0012] The device may further include a shutter positioned in front of the user's eye. The shutter is switchable between a state of transmitting light and a state of blocking light. In a state where light is transmitted, the user can view through a shutter. This allows the user to view the surrounding and transmitted images simultaneously. With the light blocked, the user will not be able to see through the shutter and will only be able to see the transmitted image.

In one embodiment, the optics is enclosed in a casing. The casing is
Humans can put on their heads. The casing may be worn along one side of the head or it may be mounted on the top of the head. Alternatively, the casing may be in the shape of a helmet.

[0014] (Description of the Invention) 1: switchable holographic materials and equipment present invention, in certain embodiments, a monomer, a liquid crystal is dispersed, the crosslinking monomer, a coinitiator, A holographic optical element formed from a polymer dispersed liquid crystal (PDLC) material including a photoinitiator dye is utilized. These PDLC materials exhibit a distinct and orderly separation of the liquid crystal and the cured polymer, which has the advantage that the PDLC material is a high quality optical element. PDLC materials used in holographic optical elements can be formed in a single step. The holographic optical element has properties of the resulting diffraction grating, such as the size, shape,
Unique photopolymerizable prepolymer materials that allow in-situ control of density, ordering, etc. can also be used. In addition, the methods and materials disclosed herein can be used to make PDLC materials for optical elements that include switchable transmissive or reflective holographic gratings.

The polymer-dispersed liquid crystal material, method, and apparatus used in the present invention are RL
Sutherland et al. Bragg Gratings in an Acrylate Polymer Consisting of Periodi
c Polymer dispersed Liquid-Crystal Planes, Chemisrry of Materials, No. 5
, pp. 1533-1531 (1993); RL Sutherland et al. "Electrically switchable volu
me gratings in polymer dispersed liquid crystals, "Applied Physics Lette
rs, Vol. 64, No. 9, pp. 1074-1076 (1994); and TJ Bunning et al. "The Morpho
logy and Performance of Holographic Transmission Gratings Recorded in Po
lymer dispersed Liquid Crystals, "Polymer, Vol. 36, No. 14, pp. 2699-270
1 (1995) and the like, and all of these documents are incorporated herein by reference. "Switebable Volume Hologram Materials and
Nos. 08 / 273,436 and 5,698,343, entitled Devices, "and" Laser Wavelength Detection and Energy Dosimetry Badge, "are also incorporated herein by reference and are incorporated by reference. Discloses a background material used for forming a transmission type diffraction grating in a volume hologram.

The process by which the hologram is formed is largely controlled by the choice of components used to prepare a homogeneous starting mixture, and to a lesser extent by the intensity of the incident light pattern. Certain types of polymer dispersed liquid crystal (PDLC) materials used in the present invention produce switchable holograms in a single step. Certain types of PDLC materials are characterized by irradiation with a non-uniform and coherent light pattern, resulting in polymerizable monomers and second phase materials, especially liquid crystals (
LC) patterned anisotropic diffusion (or de-diffusion) is initiated.
Thus, well-defined channels of material that are enriched in alternating second phases, separated by well-defined channels of substantially pure polymer, can be created in a single process.

The resulting PDLC material may have phase-separated LC droplets that are anisotropically dispersed within the photochemically cured polymer matrix. Conventional PDLC materials created by a one-step process have been able to obtain only large LC bubble areas and smaller LC bubble areas in the polymer matrix. Large bubble sizes are highly dispersed, producing hazy looks and multiple orders of diffraction. In contrast, small LC bubbles of certain PDLC materials in well-defined channels of LC-rich material allow well-defined first and zero order diffraction. Theoretically well-defined, LC-rich channels and near-pure polymer channels in PDLC materials are possible with a multi-step process, but such processes require certain types of PDLC The morphological control of the LC-rich channel and LC width and size distribution and LC droplet size enabled by the material is not possible with high precision.

The same is made by coating the mixture between two tin-doped indium oxide (ITO) coated glass slides separated by spacers, usually having a thickness of 10-20 μm. Can be. The sample is placed in a conventional holographic recording setup. Diffraction grating is usually by using an argon ion laser of 488nm intensity of about 0.1~100mW / cm ^2, typically recorded with an exposure time of 30 to 120 seconds.
By changing the angle between the two beams and changing the interval between the intensity peaks, the interval between the diffraction gratings of the obtained hologram is changed. Photopolymerization is guided by a pattern of light intensity. A more detailed description of examples of recording devices can be found in RL Sutherland et al. "Switchabl
e holograms in new phoropolymer-liquid crystal composite materials, "Soc
society of Photo-Optical Instrumentation Engineers (SPIE), Proceedings Repr
int, Volume 2402, reprinted from Diffractive and Holographic Optics Tech
nology II (1995), which is hereby incorporated by reference.

The characteristics of PDLC materials are greatly influenced by the components used to prepare a homogeneous starting mixture, and to a lesser extent by the intensity of the incident light pattern. In one embodiment, the prepolymer material is a photopolymerizable monomer, a second phase material, a photoinitiator dye, a coinitiator.
, A chain extender (or crosslinker), and, if desired, a surfactant.

In one embodiment, the two main components of the prepolymer mixture are a polymerizable monomer and a second phase material, preferably intimately mixed. Highly functionalized monomers are preferred. Such monomers shrink to some extent to form a dense crosslinked network that tends to be extruded from the second phase material. As a result, the material of the second phase is anisotropically desorbed from the polymer region and separates into a well-defined polymer-poor region and a second-phase-rich region or domain. Highly functionalized monomers may also be preferred. The high degree of crosslinking associated with such monomers results in fast kinetics, which allows the hologram to be formed relatively quickly, such that the second phase material is present in domains less than about 0.1 μm in size. Because it becomes.

In some embodiments, a mixture of penta-acrylates in combination with di-, tri-, and / or tetra-acrylates to optimize both functionalization and viscosity of the polymeric material Can be used. Suitable acrylates, for example, triethyleneglycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetra-acrylate, pentaerythritol pentaacrylate (Pentaerythritol penta-acrylate) or the like can be used. In one embodiment, a mixture of triacrylate and pentaacrylate of about 1: 4 promotes uniform mixing and provides a mixture suitable for forming a 10-20 μm coating on an optical plate. I understood.

The selected second phase material is liquid crystal (LC). This also allows for an electro-optical response to the resulting hologram. The concentration of LC used should be high enough to allow sufficient phase separation to occur in the cured sample, but high enough that the sample is impermeable or very hazy. Should not be concentration. At less than about 20% by weight, phase separation hardly occurs, and the diffraction efficiency is low. If it exceeds about 35% by weight, the degree of dispersion of the sample increases, and both the diffraction efficiency and the transmittance decrease. Good diffraction efficiency and optical clarity are generally obtained with samples made at a concentration of about 25% by weight. In prepolymer mixtures using surfactants, by adjusting the amount of surfactant,
The LC concentration can be increased to 35% by weight without compromising optical performance. Suitable liquid crystals for use in the practice of the present invention include cyanobiphenyls mixture, commercially available from Merck under the product name E7, 4'-n-pentyl-
4-cyanobiphenyl (4'-n-pentyl-4-cyanobiphenyl), 4'-n-heptyl-4-cyanobiphenyl, 4'-octoxy-4-cyanobiphenyl (4'-octaoxy-4-cyanobiphenyl), 4'-pentyl-4-cyanoterphenyl (4'-pentyl-4-cyanoterphenyl), α-methoxybenzylidene-4'-butylaniline (α-methoxybenzylidene-4'- butylaniline) and the like. Other second phase components can also be used.

The polymer-dispersed liquid crystal material used in the practice of the present invention includes (for example, Polysc
dipentaerythritol hydroxypentacrylate (available from iences, Inc. Warrington, Pennsylvania)
, (Cyanobiphenyl marketed by Merck under the product name E7)
s) A mixture, also available from BDH Chemicals, Ltd, London, England) 10-40% by weight of liquid crystal E7, (Aldrich Chemical Company, Milwaukee, Wis.)
N-vinylpyrrolidinone (N-viny), a chain extension monomer available from consin
lpyrrolidinone) ("NVP"), (Aldrich Chemical Company, Milwaukee, Wisconsi
N-phenylglycine (available from n)
NPG "), (commercially available under the product name RBAX from Spectragraph, Ltd Maumee, Ohio) and the photoinitiator dye rose bengal ester, ie, 2,4,5,7-tetraiodo-3 ', 4 ', 5', 6'-tetrachlorofluorescein-6-acetate ester (2,4,5,7-tetraiodo-3 ', 4', 5 ', 6'-tetrachlorofluorescein-6-aceta
te ester) can be formed from a polymeric material that is a homogeneous mixture of polymerizable monomers. Rose bengal is also available from Aldrich Chemical Company as rose bengal sodium salt (but must be esterified for solubility). This system has a very fast cure rate, which results in the formation of small sized liquid crystal microdroplets.

The mixture of the liquid crystal and the prepolymer material is homogenized by a suitable means (eg, ultracentrifugation) into a viscous solution, usually using a spacer having a thickness of 15 to 100 μm, preferably 10 to 20 μm. Tin-doped indium oxide (IT
Spread between glass slides coated with O). ITO is conductive and serves as an optically transmissive electrode. Preparation of the prepolymer material, mixing, and transfer to a slide glass are preferably performed in a dark place because the photosensitivity of the mixture is very high.

The sensitivity of the prepolymer material to light intensity depends on the photoinitiator dye and its concentration. When the concentration of the dye is high, the photosensitivity increases. However, in many cases, the solubility of the photoinitiator dye limits the concentration of the dye, which in turn limits the photosensitivity of the prepolymer material. However, in many typical applications, to achieve the desired sensitivity and to completely bleach the dye in the recording process to obtain a final, uncolored sample, 0.2 to 0.2. Photoinitiator dye concentrations in the range of 4% by weight have been found to be sufficient. Photoinitiator dyes that can be used to produce PDLC materials include Rose Bengal Ester (2,4,4).
5,7-tetraiodo-3 ′, 4 ′, 5 ′, 6′-tetrachlorofluorescein-6-acetate ester); Rose Bengal sodium salt; Eosin; Eosin sodium salt;
4,5-diiodosuccinylfluorescein; camphorquinone;
Methylene blue and the like. Depending on these dyes, nominally 400-700
Sensitivity to recording wavelengths over the visible light spectrum of nm is obtained. Further, it has been found that suitable near-infrared dyes, for example, cationic cyanine dyes containing a trialkylborate anion that absorbs light of 600 to 900 nm, and merocyanine dyes derived from spiropyran can also be used in the present invention. .

The co-initiator used in the practice of the present invention controls the rate of cure in the free radical polymerization reaction of the prepolymer material. Optimal phase separation and resulting PDL
Optimal diffraction efficiency in C material is a function of cure rate. The favorable result is 2
It has been found that this can be achieved by using coinitiators in the range of 〜3% by weight. Suitable coinitiators include N-phenylglycine; triethylamine; triethanolamine; N, N-dimethyl-2,6-diisopropylaniline and the like.

Other suitable dye and coinitiator combinations suitable for the practice of the invention, particularly in the visible region, include eosin and triethanolamine.
nolamine); camphorquinone and N-phenylglycine (N-
phenylglycine); fluorescein and triethanolamine (
triethanolamine; methylene blue and triethanolamine or N-phenylglycine; erythrosin B and triethanolamine
Indolinocarbocyanine and triphenyl borate; indobenzospiropyran and triethylamine.

[0028] The chain extender (or crosslinker) used in the practice of the present invention may help to increase the rate of polymerization as well as increase the solubility of the components of the prepolymer material. The chain extender is preferably a small vinyl monomer as compared to pentaacrylate, and by using a small vinyl monomer, it is difficult to access a nearby pentaacrylate monomer due to steric hindrance. It can easily react with the position of the acrylate in the acrylate monomer. Thus, the reaction between the chain extender monomer and the polymer increases the propagation length of the growing polymer. In typical applications, a range of 10 to 18% by weight of chain extender has been found to maximize performance in terms of diffraction efficiency. In one embodiment, a suitable chain extender is N-vinylpyrrolidinone.
none), N-vinyl pyridine, acrylonitrile, N-vinyl carbazo
le) and the like.

It has been found that by adding a surfactant material, ie, octanoic acid, to the prepolymer material, the switching voltage can be reduced and the diffraction efficiency can be increased. Specifically, the switching voltage of a PDLC material containing a surfactant is significantly lower than the switching voltage of a PDLC material made without a surfactant. While not intending to be bound by any particular theory, these results indicate that the polymer and the phase separated LC
It is considered that the anchoring force between the droplets is weakened. S
EM studies have shown that the size of the droplets in the surfactant-containing PDLC material can be reduced to 30-50 nm and the dispersion becomes more uniform.
In such materials, smaller droplets occupy a larger proportion, which reduces random scattering and increases diffraction efficiency. Thus, the shape of the droplet is closer to a sphere than when a surfactant is present, which results in lower switching voltage.

For more general applications, samples containing only 5% by weight of surfactant have been found to have significantly lower switching voltages. Also, when optimizing for low switching voltages, the concentration of surfactant can vary up to about 10% by weight (often determined by the LC concentration), which results in very high diffraction efficiencies. And increased switching voltage (perhaps due to reduced total phase separation of the LC). Suitable surfactants include octanoic acid; heptanoic acid; dodecanoic acid, and the like.

In the sample using octanoic acid as a surfactant, it is presumed that the cause is the presence of a free carboxyl group (COOH) in octanoic acid, but it was observed that the conductivity of the sample was increased. . As a result, the sample has a higher frequency (
(2 KHz) for a long time, the temperature rises. Therefore, it is desirable to add a surfactant to reduce high conductivity without sacrificing high diffraction efficiency and low switching voltage. A suitable electrically switchable diffraction grating is vinyl neononanoate, a polymerizable monomer commercially available from Aldrich Chemical Co. in Milwaukee, Wisconsin.
It was found that ( "VN") may be formed from _{C 8 H 17 CO 2 CH =} CH 2. Favorable results were also obtained when the chain extender N-vinylpyrrolidinone ("NVP") and the surfactant octanoic acid were replaced by 6.5% by weight of VN. VN also acts as a chain extender due to the presence of reactive acrylate monomer groups. In these changes, optical quality samples with about 70% diffraction efficiency were obtained, and the resulting grating could be electrically switched by applying an electric field of 6 V / μm.

The PDLC material used in the present invention may be formed using a liquid crystal bifunctional acrylate (“LC monomer”) as a monomer. The LC monomer is highly miscible with low molecular weight nematic LC materials and has a high concentration of low molecular weight L
It is superior to conventional acrylate monomers in promoting the formation of C and creating a sample with high optical quality. The presence of high concentrations of low molecular weight LC in PDLC materials reduces the switching voltage (eg, to 〜2 V / μm). LC
Another advantage of using monomers is that the weak AC during recording the hologram
Alternatively, the desired orientation and configuration of the nematic director in the LC droplet can be obtained by pre-aligning the host LC monomer and low molecular weight LC by applying a DC electric field. The chemical formulas of some suitable LC monomers are as follows:

[0033]

Embedded image

Semifluorinated polymers exhibit weaker anchoring properties and are known to have significantly lower switching fields. Therefore,
Semi-fluorinated acrylate monomers that are difunctional liquid crystals are considered suitable for use in the present invention.

Referring now to FIG. 1, an electrically switchable hologram 31 formed of an exposed polymer dispersed liquid crystal material made in accordance with the description herein.
0 is shown in cross section. A layer 312 of polymer dispersed liquid crystal material comprises a pair of tin-doped indium oxide coated glass slides 314 and spacers 316.
It is sandwiched between. Inside the hologram 310 is a Bragg transmission grating 318 formed when the layer 312 is exposed to an interference pattern generated by two intersecting coherent laser light beams. The exposure time and light intensity can be varied depending on the desired diffraction efficiency and liquid crystal domain size. The size of the liquid crystal domains can be controlled by varying the concentration of photoinitiators, coinitiators, and chain extenders (or crosslinkers). As the diffraction grating is recorded by applying an external electric field across the ITO electrode, the direction of the nematic director can be controlled.

The scanning electron micrograph shown in FIG. 2 of the cited document Applied Physics Letters, which is incorporated herein by reference, shows that a sample loaded with 36% by weight of liquid crystal had 95 mW / c.
It is a photograph of the recorded surface of the diffraction grating with the light of 488nm argon ion laser m ^2. The size of the liquid crystal domain is about 0.2 μm, and the spacing between the diffraction gratings is about 0.54 μm. This sample, about 20 μm thick, diffracts light according to Bragg's law.

FIG. 2 is a graph showing normalized net transmittance and normalized net diffraction efficiency versus the root mean square (Vrms) of a hologram made in accordance with the present specification. It is. Δη is the change in first-order Bragg diffraction efficiency. ΔT is the change in the zero-order transmittance. FIG. 2 shows that as the voltage is increased, the energy shifts from the primary beam to the zero order beam. About 22
At 5 Vrms, there is a true minimum in diffraction efficiency. The peak diffraction efficiency can be determined by appropriately adjusting the thickness of the sample according to the wavelength of the probe beam and the polymerization.
00% can be approached. The minimum diffraction efficiency can be approached to 0% by slightly adjusting the parameters of the PDLC material to make the refractive index of the cured polymer equal to the ordinary refractive index of the liquid crystal.

By increasing the frequency of the applied voltage, the switching voltage for minimum diffraction efficiency can be significantly reduced. This is shown in FIG.
FIG. 3 shows both the threshold root mean square voltage 20 and the fully switched root mean square voltage 22 required for a switching program created in accordance with the description herein to obtain the minimum diffraction efficiency for the frequency of the root mean square voltage. It is a graph. The threshold and the full switching mean square voltage at 10 kHz are 20
Vrms and down to 60Vrms. It is estimated that the higher the frequency, the lower the value.

As the size of the liquid crystal droplets becomes smaller, there arises a problem that a switching voltage for switching their directions becomes higher. As explained in the previous paragraph, using a high frequency alternating current switching voltage helps to reduce the required switching voltage. As shown in FIG. 4, adding a surfactant (eg, octanoic acid) to the prepolymer material in an amount of about 4-6% by weight of the total mixture results in 1-2 k
A sample hologram with a switching frequency of about 50 Vrms at a low frequency of Hz is obtained. As shown in FIG. 5, it was also found that reducing the size of the droplet using a surfactant shortened the switching time of the PDLC material. Therefore,
Samples made with surfactants can switch in about 25-44 microseconds. While not intending to be bound by any theory, surfactants
It is believed that the switching voltage is lowered by reducing the anchoring of the liquid crystal at the interface between the liquid crystal and the cured polymer.

The thermal control of the diffraction efficiency is shown in FIG. FIG. 5 is a graph showing normalized net diffraction efficiency versus temperature and normalized net transmittance of a hologram made in accordance with the description herein.

It has been demonstrated that the polymer dispersed liquid crystal materials disclosed herein can be used to record volumetric holograms of certain compositions of such polymer dispersed liquid crystal systems.

As shown in FIG. 7, a PDLC reflective diffraction grating is created by placing several droplets of a mixture of prepolymer material 112 on a glass slide 114 a coated with tin-doped indium oxide. Next, the second tin-doped indium oxide coated slide 114b is pressed against the first slide so that the prepolymer material 112 fills the area between the slides 114a and 114b. By using a preferably uniform spacer 118,
Maintain the slide spacing at about 20 μm. The operation of preparing the prepolymer material and transferring it to a slide glass is preferably performed in a dark place. After assembly, a mirror 116 can be provided behind glass plate 114b. Preferably, the distance from the sample to the mirror is substantially shorter than the coherence length of the laser. The PDLC material preferably has a strength of about 0.1 when spread over the entire surface of the glass plate.
About 100 mW / cm ² of 488 nm argon ion laser light, generally 30 to
Exposure is for 120 seconds. The constructive and destructive interference in the diverging beam creates a periodic intensity distribution through the thickness of the coating.

In one embodiment, the prepolymer material used to make the reflective grating comprises a monomer, a liquid crystal, a crosslinking monomer, a coinitiator, and a photoinitiator dye. The reflection type diffraction grating is a dipentaerythritol hydroxypentaacrylate (di
In addition to monomers containing pentaerythritol hydroxypentacrylate) (DPHA), 3
5% by weight of cyanobiphenyl (commercially available under the trade name E7)
s) Liquid crystal composed of a mixture, 10% by weight of N-vinylpyrrolidone
inone) ("NVP"), 25% by weight of the co-initiator N-phenylglycine ("NPG"), and ^10-5 to ^10-6 gram moles of rose bengal ester. ester) can be formed from a polymeric material that includes a photoinitiator dye. It is further believed that the addition of a surfactant, as in the case of transmission gratings, provides the same beneficial properties as described above in connection with transmission gratings. It is also contemplated that similar ranges and modifications of the prepolymer starting material can be readily applied to forming a suitable reflective grating.

The low voltage, high resolution scanning electron microscope ("LVHRSEM") confirmed that the resulting material contained a fine diffraction grating with a diffraction vector perpendicular to the surface and with a period of 160 nm. Therefore, as schematically shown in FIG.
Polymer channel 130a and PDLC channel 130b extending parallel to 34
Having a periodic surface. The spacing associated with these periodic surfaces of the diffraction grating is relatively constant over the entire thickness of the sample from the air-coating interface to the coating-substrate interface.

While interference is utilized to create both transmission and reflection gratings, the shape of reflection gratings is significantly different. More specifically, it was confirmed that, unlike the case of the transmission type diffraction grating having the similar liquid crystal concentration, the liquid crystal droplets hardly aggregated. Furthermore, very few droplets having a diameter of 50 to 100 nm were present in the material. Furthermore,
Unlike the transmissive diffraction grating, where the area rich in liquid crystal is usually less than 40% of the diffraction grating, the liquid crystal rich area of the reflective grating is very large. Since the period of the reflection type diffraction grating is very short, that is, the interval between the gratings is very narrow (〜0.2 μ), the time until the end of curing in the region of low light intensity and the time to the end of curing in the region of high intensity are high. And the difference is considered very small. Also, as is evident from the small diameter of the droplets, the polymerization at a fast rate significantly reduces the percentage of liquid crystals in the matrix during gelation, which results in the growth of large droplets or a larger area of smaller droplets. It is considered that the distribution to

Analysis of the reflection notch in the absorption spectrum (reflection break) supports the conclusion that a periodic index change exists throughout the thickness of the coating. In PDLC materials formed with a 488 nm argon ion laser, the reflective notch typically has a relatively narrow bandwidth and about 472 n for normally incident light.
m of the reflected light wavelength. The difference between the wavelength of writing and the wavelength of reflection is small (about 5
%) Indicates that shrinkage of the coating is not a problem. Furthermore, the performance of such a grating has been found to be stable over a period of several months.

In addition to the materials used in the above examples, suitable PDLC materials include triethyleneglycol diacrylate,
Trimethylolpropanetriacrylate
, Pentaerythritol triacrylate,
Examples thereof include pentaerythritol tetracrylate and pentaerythritol pentaacrylate. Similarly, other coinitiators such as triethylamine (
triethylamine, triethanolamine, and N, N-dimethyl-2,6-diisopropylaniline (N, N-dimethyl-2,6-diisopropylaniline) are also alternatives to N-phenylglycine Can be used.
A preferred photoinitiator dye for use with argon ion lasers at wavelengths of 458 nm, 476 nm, 488 nm, and 514 nm is rose bengal sodium salt.
alt), eosin, eosin sodium salt, fluorescein sodium salt (f
luorescein sodium salt) and the like. When using a laser having a wavelength of 633 nm, methylene blue is often used. Also, other liquid crystals, for example, 4'-pentyl-4-cyanobiphenyl
It is considered that 4'-heptyl-4-cyanobiphenyl and the like can also be used.

Referring again to FIG. 8 a, there is shown a three-dimensional view of a reflective diffraction grating 130 according to the present invention with a periodic plane of polymer channels 130 a and PDLC channels 130 b disposed parallel to the front surface 134 of the diffraction grating 130. Have been. The symmetry axis 136 of the liquid crystal domain is formed perpendicular to the periodic channels 130a and 130b of the diffraction grating 130 and perpendicular to the 134 of the diffraction grating 130.
Thus, when an electric field E is applied, the axis of symmetry 136 is already in a low energy state that matches the electric field E and is re-oriented, as shown in FIG. 8b. Therefore, the reflection type diffraction grating according to the present invention is not usually switchable.

In general, reflective gratings tend to reflect a narrow range of wavelengths so that they can be used as reflective filters. However, in some embodiments, the reflective grating is formed to be switchable. Specifically, a switchable reflective grating is formed using a negative dielectric anisotropy LC (or LC having a low crossover frequency), an applied magnetic field, an applied shear stress field, or a tilted grating. Can be done.

It is known that a liquid crystal having a negative dielectric anisotropy (Δε) turns in a direction perpendicular to an applied magnetic field. As shown in FIG. 9 a, the axis of symmetry 136 of the liquid crystal domain formed of liquid crystal having a negative Δε is perpendicular to the periodic channels 130 a and 130 b of the diffraction grating 130 and perpendicular to the front surface 135 of the diffraction grating. Orientation. However, when an electric field E is applied across such a grating, the axis of symmetry of the negative Δε liquid crystal is distorted, as shown in FIG. 9b, perpendicular to the periodic plane of the grating and the coating. Is reoriented in a direction perpendicular to the strong electric field E. As a result, the reflection type diffraction grating can be switched between a reflection type state and a transmission type state. FIG. 9c illustrates a negative Δε that may be used in the methods and apparatus described herein.
And other liquid crystals having the formula:

Liquid crystals can have either positive or negative Δε in nature (or when synthesized). Thus, it is possible to use an LC that has a positive Δε at low frequencies but becomes negative at high frequencies. The frequency at which the sign of Δε changes (of the applied voltage) is
It is called a crossover frequency. The crossover frequency varies depending on the composition of the LC, and generally has a value in the range of 1 to 10 kHz. Therefore, by operating at an appropriate frequency, the reflection type diffraction grating can be switched. It is believed that low crossover frequency materials can be made from a combination of positive and negative dielectric anisotropic liquid crystals. Positive dielectric liquid crystals suitable for use in such combinations include tetracyclic esters as shown in FIG. 9d. Strong negative dielectric liquid crystals suitable for use in such a combination are made from pyridazine as shown in FIG. 9d. Both liquid crystal materials are from LaRoche & Co., Switzerla
Commercially available from nd. By varying the ratio of the positive and negative liquid crystals in this combination, a crossover frequency of 1.4-2.3 kHz at room temperature is obtained. Other combinations suitable for use in this example include p-pentylphenyl-2-
Chloro-4-benzoate (p-pentylbenzoyloxy) benzoate (p-penty
lphenyl-2-chloro-4- (p-pentylbenzoyloxy) benzoate) and benzoate (benzo
ate). These materials are available from Kodak Company.

More specifically, a switchable reflective diffraction grating can be formed using a positive Δε liquid crystal. As shown in FIG. 10a, such a diffraction grating is formed by exposing the PDLC starting material to a magnetic field during the curing process. This magnetic field can be generated by using a Helmholtz coil (as shown in FIG. 10a), using a permanent magnet, or using other suitable means. Preferably, the magnetic field M is applied in a direction parallel to the front of the glazing (not shown) used to form the diffraction grating 140. As a result, the axis of symmetry 146 of the liquid crystal is oriented along the magnetic field while the mixture is a liquid. At the end of the polymerization, the magnetic field is removed and the orientation coincident with the axis of symmetry of the liquid crystal is maintained (see FIG. 10b). When an electric field is applied, the liquid crystal of positive Δε is reoriented in the direction of the electric field, as shown in FIG. .

FIG. 11 a shows the oblique transmission type diffraction grating 148, and FIG. 11 b shows the oblique reflection type diffraction grating 150. A holographic transmission diffraction grating is considered to be oblique when the direction of the vector G of the diffraction grating is not parallel to the surface of the diffraction grating. In a holographic reflection diffraction grating, it is said that the diffraction grating vector G is inclined when the diffraction grating vector G is not perpendicular to the surface of the diffraction grating. Oblique diffraction gratings have many of the same uses as non-oblique diffraction gratings, such as display devices, mirrors, line filters, optical switches, and the like.

First, the direction of the diffracted beam is controlled using an oblique holographic diffraction grating. For example, in a reflection hologram, an oblique diffraction grating is used to separate the surface reflection of the coating from the diffracted beam. For PDLC holographic diffraction gratings, oblique diffraction gratings have more advantages. The oblique type allows the modulation depth of the diffraction grating to be controlled by an electric field when using a liquid crystal oriented in either the tangential direction or the homeotropic direction. This is because this diagonal direction
This is because the electric field component is supplied in both the tangential direction and the vertical direction with respect to the diffraction grating vector. More specifically, in the case of a reflective diffraction grating, the axis of symmetry of the LC domain is oriented in a direction along the diffraction grating vector G, and is oriented in a direction perpendicular to the plane of the thin film by an electric field E applied in the longitudinal direction. Can be switched. This is a common geometry for switching the diffraction efficiency of an oblique reflection grating.

When recording on an oblique reflection type diffraction grating, it is desirable to place a sample between the oblique sides of two perpendicular glass prisms. The density filter can then be placed in optical contact with the back surface of the prism using a fluid with a matched refractive index to avoid back reflections which would also cause a diffraction grating to be recorded. The incident laser beam is split by a conventional beam splitter into two beams, which are then directed to the front of the prism and overlap at the desired angle at the sample. Thus, these beams will be incident on the sample from opposite sides. This prism coupling technology allows light to strike the sample at a larger angle. The resulting tilt of the grating is determined by the angle at which the prism assembly is turned (ie, the angle between the direction of one incident beam and the normal to the front of the prism at the point where the beam enters the prism). You.

As shown in FIG. 12, a switchable reflective grating can be formed in the presence of an applied shear stress field. In this method, a shear stress is applied along the direction of the magnetic field M. This can be achieved, for example, by applying equal and opposite tensile forces to two ITO-coated glass sheets sandwiching the prepolymer mixture while the polymer is in a soft state. This shear stress distorts the LC domain in the direction of the stress, with the resulting LC domain symmetry axis oriented primarily along the direction of the stress, parallel to the PDLC plane and perpendicular to the direction of the electric field applied for switching. .

A reflective diffraction grating made according to this description can be used as a color reflective display,
It can be used for applications such as a switchable wavelength filter for laser protection and a reflection type optical element.

In some embodiments, PDLC materials can be made to exhibit a property known as birefringence. Due to birefringence, polarized light transmitted through the diffraction grating will have altered polarization. Such gratings are subwavelength gratings (subwatts).
Known as avelength gratings, they behave like negative uniaxial crystals such as calcite, potassium phosphate, or lithium niobate, with the optical axis perpendicular to the PDLC plane. Referring now to FIG. 13, a transmission grating 200 made in accordance with the description herein having a surface perpendicular to the front surface 204 of the diffraction grating 200, where the polymer surface 200a and the PDLC surface 200b are periodically present. Is shown. The optical axis 206 is perpendicular to the polymer surface 200a and the PDLC surface 200b. Each polymer surface 200a has a thickness _{t p} and the refractive index _{n p,} the PD
The LC surface 200b has a thickness t _PDLC and a refractive index n _PDLC .

Here, the composite thickness of the PDLC plane and the polymer plane is the optical wavelength (ie, (t _PDLC +
Generally smaller than t _P ) << λ), the diffraction grating exhibits birefringence. As described later, the magnitude of the polarization shift is proportional to the length of the diffraction grating. Therefore, by carefully selecting the length L of the diffraction grating below the wavelength for a given light wavelength, it is possible to rotate the plane of polarization or to produce circularly polarized light. Therefore, it is possible to design such a sub-wavelength diffraction grating to function as a half-wave or quarter-wave plate, respectively. Thus, the advantage of this process is not dependent on the birefringence of any given material at that wavelength, but rather the birefringence of the material can be adjusted by simple design parameters to optimize for a particular wavelength That is.

To form a half-wave plate, the retardance of the subwavelength grating must be equal to half the wavelength (ie, delay = λ / 2), and the quarter-wave plate To form, the delay must be equal to one quarter of the wavelength (ie, delay = λ / 4). Delay net birefringence | [Delta] n | related to, it is the difference between the ordinary refractive index n _o and extraordinary refractive index n _e of wavelength less than the diffraction grating as the following equation. Delay = | Δn | L = | n e -n o | L Thus, the half-wave plate (i.e., a delay equal to half the wavelength), the length of a wavelength less than the diffraction grating may be selected as follows. L = λ / (2 | Δn |) Similarly, for a quarter-wave plate (ie, the delay is equal to / 4 of the wavelength), the length of the sub-wavelength grating can be selected as . L = λ / (4 | Δn |) As shown in FIG. 14A, for example, when the incident polarization is at an angle of 45 ° with respect to the optical axis 210 of the half-wave plate 212, the plane polarization is preserved but the plate is Outgoing wave polarization is 90 °
Can shift. Thus, incident light is transmitted as shown in FIGS. 14b and 14c, which are located between the polarizers 214 and 216 with the combined half-wave plate 212. When an appropriate switching voltage is applied as shown in FIG. 14d, the polarization does not rotate and the light is blocked by the second polarizer.

In the case of a quarter-wave plate, the polarization is converted to circular polarization. Thus, the reflected light is reflected by the beam splitter 218, as shown in FIG. When an appropriate switching voltage is applied as shown in FIG. 15b, the reflected light passes through the beam splitter and is reflected back along the incident beam.

FIG. 16 a shows the front surface 234 of the diffraction grating 230 recorded by the method described above.
PDLC channel 230b and polymer channel 230a arranged perpendicular to
A three-dimensional view of the sub-wavelength diffraction grating 230 having a periodic plane of FIG. As shown in FIG. 16 a, the axis of interest 232 of the liquid crystal domain is arranged parallel to the surface 234 of the grating and perpendicular to the periodic channels 230 a and 230 b of the grating 230. Thus, when an electric field E is applied to the diffraction grating, as shown in FIG. Parallel to channels 230a and 230b. As a result, the subwavelength diffraction grating 230 can switch between a state in which the incident polarization is changed and a state in which the polarization is not changed. While not intending to be bound by any theory, the orientation of the symmetric axis 232 of the liquid crystal domain is also due to the surface tension gradient resulting from the anisotropic dispersion of monomer and liquid crystal during the recording of the diffraction grating. It is believed that the gradient directs the axis of interest of the liquid crystal domain perpendicular to the periodic plane.

As disclosed in Born and Wolf, Principles of Optics, 5th Ed., New York (1975), incorporated herein by reference, the birefringence of a subwavelength grating is It is given by:

[0064]

(Equation 1)

Where n _o = the _sub -wavelength _sub -wavelength ordinary ray refractive index ne _e = extraordinary light refractive index n _PDLC = the refractive index of the PDLC plane n _p = the refractive index of the polymer plane n _LC = the liquid crystal seen by the incident light The effective refractive index of f _PDLC = t _PDLC / (t _PDLC + t _p ) f _p = t _p / (t _PDLC + t _p ) Therefore, when n _PDLC = n _p , the birefringence of the _sub -wavelength diffraction grating is zero. is there.

The effective index of refraction n _LC of the liquid crystal is a function of the applied electric field that takes a maximum value E _MAX when the electric field is zero at some value of the electric field and is equal to the value n _p of the polymer. It has been known. Thus, the application of an electric field can change the refractive index n _{LC of the} liquid crystal and thus the refractive index of the PDLC plane. Using the above relationship, the net birefringence of the subwavelength grating is minimal when n _PDLC is equal to n _p (ie, n _LC = n _p ). Therefore, if the refractive index in the PDLC plane matches the refractive index in the polymer plane by applying an electric field (ie, n _PDLC = n _p ), then the birefringence of the subwavelength grating may disappear.

[0067] From equation Born and Wolf (supra), the net birefringence _{(i.e., | Δn | = | n e} -n o |) for equation becomes:.

[0068]

(Equation 2)

Where n_AVG= (n_e+ N_o) / 2 Further, as shown by the following equation, the refractive index n_PDLCIs the liquid crystal seen by the incident light
Effective refractive index n_LCAnd the refractive index n of the surrounding polymer plane_PRelated to N_PDLC= n_P+ f_LC[n_LC−n_P] Where f_LCIs the volume fraction of the liquid crystal dispersed in the polymer in the PDLC plane, and f _LC = [V_LC/ (V_LC+ V_P)].

For example, typical values for the effective refractive index of a liquid crystal in the absence of an electric field are n _LC = 1.7 and n _P = 1.5 for a polymer layer. For a grating where the thickness of the PDLC plane and the polymer plane are equal (ie, t _PDLC = t _P , f _PDLC = 0.5 = f _P ) and f _LC = 0.35, the net birefringence Δn of the sub-wavelength grating is It is about 0.008. Therefore, the incident light
If it has a wavelength of 0.8 μm, the wavelength of the sub-wavelength diffraction grating is 50 μm for the half-wave plate.
m, which is 25 μm for a quarter-wave plate. Further, by applying an electric field of about 5 V / μm, the refractive index of the liquid crystal matches the refractive index of the polymer, and the birefringence of the half-wavelength diffraction grating can be eliminated. Therefore, the switching voltage V _n for the half-wave plate is about 250V, the switching voltage for the quarter-wave plate is about 125 volts.

By applying such a voltage, the plate can be switched between an on state and an off state (zero lag) on the order of microseconds. By way of comparison, current Pockels cell technology can be switched in nanoseconds at voltages of about 1000-2000V, and bulk nematic liquid crystals can be switched in milliseconds at voltages of about 5V.

In another embodiment, as shown in FIG. 17, the switching voltage of the sub-wavelength grating can be reduced by stacking the sub-wavelength gratings 220a-220e together and electrically connecting them in parallel. it can. For example, it is known that a stack of five diffraction gratings, each having a length of 10 μm, produces the required thickness of a half-wave plate. Note that the length of the sample is somewhat larger than 50 μm, since each grating includes a tin-doped indium oxide coating that functions as a transparent electrode. However, the switching voltage for such a stack of plates is only 50V.

The above-mentioned sub-wavelength diffraction gratings are used not only in tunable filters for telecommunications, colorimetry, spectral analysis, laser protection, etc., but also in the field of polarizers and optical switches for displays and laser optics. It is expected that suitable applications will be found. Similarly, electrically switchable transmission gratings have many uses where light is deflected or holographic images are switched. Such applications include fiber optic switches, reprogrammable NxN optical interconnects for optical coupling, beam steering for laser scalpels, beam steering for laser radar, holographic image recording and retrieval, digital zoom optics (Switchable holographic lens),
Graphic technology and entertainment are included.

In a switchable hologram, the diffraction efficiency of the hologram is changed by the application of an electric field, and the hologram can be switched from a completely on state (high diffraction efficiency) to a completely off state (low diffraction efficiency or 0). In a static hologram, its properties remain fixed independently of the applied electric field. According to the present invention, a hologram in a high contrast state can be generated. In a variant, the hologram is recorded as described above. The cured polymer film is then briefly immersed in a suitable solvent at room temperature and finally dried. In the case of liquid crystal E7, methanol shows sufficient adaptability. Other possible solvents include alcohols such as methanol, hydrocarbons such as hexane and heptane, and the like. Drying the material produces a high contrast hologram with high diffraction efficiency. Since the second layer domain is replaced by empty gaps (air) (n ~ 1), the high diffraction efficiency is
This is the result of large index modulation at Δnn0.5).

Similarly, according to the present invention, a high birefringent static subwavelength waveplate (subwavelength w
ave-plate). Since the refractive index of air is sufficiently lower than that of most liquid crystals, the thickness of the corresponding half-wave plate can be reduced. Waveplates synthesized in accordance with the present invention can be used in many applications where polarizers are not available for suitable birefringent materials, where the appropriate wavelength is particularly expensive or too bulky.

The terms “polymer-dispersed liquid crystal” and “polymer-dispersed liquid crystal material” include solutions in which monomers have not been polymerized or cured, solutions in which some polymerization has occurred, and fully polymerized solutions. One skilled in the art will recognize that the term polymer-dispersed liquid crystal (the grammatical term refers to a liquid crystal dispersed in a fully polymerized substrate), a term that is commonly used by those skilled in the art, is more grammatically correct polymer-dispersed liquid crystal material or grammatically It will be understood that it is meant to include some or all of the starting materials of the correct polymer dispersed liquid crystal material.

2: Head Mounted Device for Viewing Video FIG. 18 shows an embodiment of a head mounted device for viewing video. The device includes a casing 10 formed to be mounted on the user's head (1 in FIG. 18).
1 schematically). In one embodiment, the casing extends generally vertically, such as extending along the user's head 11, and along the user's adjacent eye 14 from the front end of the vertical portion 12. And a curved front portion 13. The image generator 15 can be arranged in the rear adjacent vertical section 12, and the image generator 15 includes a display screen 16 on which images are displayed. The optics are located within the remainder of casing 10 and serve to transmit light along the optical path from the image generator to the user's eyes.

In one embodiment, the optical system transmits light from the display screen 16 to the first portion 18, a portion located in front of the user's eye 14. And a second portion 17. The first part 18 comprises at least one switchable holographic optical element. Examples of switchable holographic optical elements have been described in detail in the previous section. Generally, switchable holographic optical elements include holographic recording media. In the holographic recording medium, a hologram of a thick phase or a thin phase is recorded. The holographic recording medium consists of a photopolymer dispersed liquid crystal mixture.
The photopolymer-dispersed liquid crystal mixture undergoes phase separation during the hologram recording process,
Create stripes consisting of areas densified by liquid crystal microdroplets, such as those scattered by clear photopolymer areas. The resulting phase volume hologram shows very high diffraction efficiency. However, when an electric field is applied using an electrode coupled to the holographic recording medium, the intrinsic direction of the liquid crystal droplet changes, reducing fringe modulation. As a result, the efficiency of the hologram diffraction pattern is reduced to a very low level, thereby erasing the hologram. Thus, a switchable holographic optical element has two active and inactive states.
Can exist in two states. An active state is defined as a state in which a hologram appears on a holographic recording medium. The inactive state is a state where the hologram is effectively erased by applying an electric field to the holographic recording medium.

In one embodiment, the front portion includes a diffractive element 20 and a reflective element 19. Light from the second portion 17 of the optical system passes through the element 20 and then the element 19 reflects the individual light towards the user's eyes. Element 19 to casing part 13
The shutter 22 is arranged in front of the window 21 (see FIGS. 18 and 21) in front of. Either the reflective element 19 or the diffractive element 20 can be formed from a switchable holographic optical element. Another component of the optical system can form a standard optical component. Examples of standard optical components include, but are not limited to, non-holographic diffraction gratings, lenses, mirrors, Fresnel lenses, and non-switching holographic diffraction gratings or lenses. Thus, in one embodiment,
The diffractive element 20 may be formed using standard optical components, and the reflective element 19 may be formed using a switchable holographic optical element. Alternatively, it is possible to form the diffractive element 20 from a switchable holographic optical element and form the reflective element 19 from a standard optical component. Note that optical components of the optical system other than the diffractive element 19 and the reflective element 20 may be formed from switchable holographic optical elements. Also, while holographic optics are shown as planar elements, it should be understood that curved holographic optics may be used. The curved optical element facilitates correcting aberrations and increasing the optical efficiency of the system. The formation and use of curved switchable holographic optical elements is described in detail in U.S. patent application Ser. No. 09 / 416,076, which is hereby incorporated by reference.

The reflection element 19 can be a reflection-type switchable holographic diffraction element. Reflective switchable holographic diffraction elements include holographic recording media on which holograms are recorded. For reflection-type switchable holographic diffraction elements, the hologram is a reflection-type diffraction grating. A reflective switchable holographic diffractive element, such as element 19,
Mimics the function of a mirror. That is, the incident light is reflected toward the user's eyes. The switchable holographic diffraction element of the reflection type can be operated both in an active state and in an inactive state. In the active state, the reflective switchable holographic diffraction element reflects incident light. In the inactive state, the reflective switchable holographic diffractive element changes to the transmissive state, allowing incident light to pass through the element without substantial change. The inactive state is induced by applying an electric field by electrodes mounted on the holographic recording medium. FIG. 20 shows a switchable holographic diffraction element 19 of the reflection type to which an electrode is applied. The electrodes are coupled to controller 35.
The controller is configured to control the application of an electric field to the reflective switchable holographic diffraction element.

The diffraction element 20 can be a transmission-type switchable holographic diffraction element. Transmission type switchable holographic diffraction elements include holographic recording media in which holograms are recorded. For transmission-type switchable holographic diffraction elements, the hologram is a transmission-type diffraction grating. The transmissive switchable holographic diffraction element is operable in both active and inactive states. In the active state, a transmissive switchable holographic diffraction element diffracts incident light as it passes through the element. In the inactive state, the hologram recorded in the transmissive switchable holographic diffractive element is effectively erased, allowing incident light to pass through the element without substantial change . The inactive state can be induced by applying an electric field with an electrode attached to the holographic recording medium, as described above.

In one embodiment, reflective element 19 and diffractive element 20 comprise holographic diffractive elements that are both switchable. The reflection element 19 is a reflection-type switchable holographic diffraction element. The diffraction element 20 is a transmission type switchable holographic diffraction element. The combination of two or more switchable or non-switching diffractive elements increases the color variations and off-axis aberrations that each balanced diffractive element produces.

[0083] In some embodiments, the image generator is configured to generate a color image. Generally, a color display device emits red, blue and green light to generate a color image. In many cases, the pixels of a color display device are composed of red, blue, and green sub-pixels. Alternatively, the pixels may be formed to emit red, blue, and green sequentially. The image generator may be based on any technique of transmission, reflection, diffraction, or self-emission. For example, the input video display can be manufactured based on emissive technology, examples of which include an electroluminescent panel or a miniature CRT. Manufacturing based on diffraction techniques is also possible, such as Si, California.
Grating Light Valve manufactured by licon Light Machines.

In one embodiment, as shown in FIG. 19, the image generator is provided with an array of light emitting diodes (LEDs) 30 above the polarizing beam splitter cube 31, and the LED and the beam splitter cube An array 32 of Fresnel lenses is inserted between them. Light from the LEDs 30 is first collimated by the Fresnel lens array 32 and then reflected by the junctions 33 of the cube 31 toward the display screen 16. In one embodiment, screen 16 is LE
The light from D30 displays a monochrome image, and the resulting image is transmitted through cube junction 33 toward second portion 17 of the optical system. The display screen 16 can be any suitable shape and can take the shape of a miniature reflective silicon backplane device or LCD panel.

Although not shown, the image generator 15 also includes a quarter-wave plate and an LED 30
, Each including a three color interference filter that filters light into three narrow bandwidths centered on the red, green, and blue peak wavelengths. There are other devices where the image generator 15 includes either or both optical integrated circuits and holographic optical elements. Still other devices may utilize solid-state lasers as light sources so that the image generator emits essentially narrow wavelengths and does not require bandwidth filtering.

FIG. 19 illustrates the use of a reflective LCD panel for an image generator. In another embodiment, the LCD panel can be illuminated incident off-axis at a sufficiently large angle of incidence so that light reflected by the LCD panel is not incident. Therefore, there is no need to use a beam splitter cube.

In another embodiment, a rear-illuminated transmissive LCD panel can be used. Thus, an image is generated on the LCD panel and is illuminated by a light source behind the LCD panel.

The holographic optical element 19 which can be switched so that a color image is transmitted
Is formed of a stack of three holographic layers, 19a, 19b, and 19c, and the optical element 20 comprises three holographic layers, 20a, 20b, and 20c.
Formed in a stack. The three holographic layers can be formed as independent layers separated by a glass plate. Alternatively, the three holographic layers can be formed in one holographic recording medium. The following description applies only to element 19 and holographic layers 19a, 19b and 19c. However, holographic layers 20a, 20b and 20c are
It should be understood that only the holographic images formed and recorded in the layers are similar.

The switchable holographic optical element 19a has a hologram recorded therein and optimizes it to diffract red light. The switchable holographic optical element 19b has a hologram recorded within itself and is optimized to diffract green light. The switchable holographic optical element 19c has a hologram recorded within itself and optimizes to diffract blue light. Switchable holographic optical elements 19a, 19
b and 19c each have a set of electrodes configured to apply various voltages to the respective switchable holographic optical elements. Element 1
Since 9 is a reflective switchable holographic optical element, the hologram is optimized to reflect light of a suitable bandwidth.

As described above, the image generator can be configured to sequentially generate the red, green, and blue components of a color image. In one embodiment, emulsion 19a,
Voltage can be applied to the set of electrodes corresponding to 19b and 19c at any time. When a voltage is applied to the electrodes, a selected amount of light diffracts into the first command form of the hologram and is directed to the user, while light in the zero command form is directed to the user invisible. . So that the selected amount of red, green and blue light is directed to the user,
A voltage is sequentially applied to each electrode of the three holograms. If the speed at which the holograms are sequentially activated is faster than the response time of the human eye, the hologram 19a
, 19b, and 19c, the monochromatic images of red, green, and blue are integrated and appear as a color image to the human eye.

The holographic optical elements 19a, 19b and 19c are switched in cooperation with the light emitted from the image generator. For example, if red light is emitted from the image generator, the holographic optics corresponding to green light and blue light are deactivated, substantially transmitting incident light. However, because the holographic optical element 19a remains active, the incident red light is diffracted towards the user. Similarly, when green light is emitted from the image generator, holographic optics 19a and 19c are deactivated, but holographic optics 19a and 19c are deactivated.
b is active. Finally, when blue light is emitted from the image generator, holographic optics 19a and 19b are deactivated, while holographic optic 19c is active.

As described above, two or more diffractive elements can be combined to balance the extreme chromatic dispersion and non-axial chromatic aberration caused by each diffractive element. In this regard, it is particularly advantageous to use separate components for red, green and blue. This is because the optics can be optimized for each of the colors red, green and blue.
In conventional color display systems that do not have separate diffraction elements for each color, the optics needed to be optimized for the entire visible bandwidth. Such optimization can be difficult in systems including holographic / diffractive elements.

In one embodiment, the second part 17 of the optical system comprises four lens elements 23, 24, 25 and 26 (in order from the image generator along the optical path), a reflective element (mirror)
27, including another two lens elements 28 and 29. In each lens element, the surface facing the image generator is suffixed with a and the surface on the opposite side is suffixed with b.
The surface of the mirror 27 is designated as 27a. Each of these optical elements constitutes an optical system,
Transmit the light generated by the image generator to the first portion. A small optical system is formed to address light aberrations and scattering as the light travels to the second portion. 18 and FIG.
Although a particular number of independent optical elements are shown, it should be understood that small optics may have more or fewer optical elements depending on the design of the application. Although many elements are shown as standard lenses and mirrors, it should be understood that holographic optics (static or switchable) can be used in small optics. Further, other types of standard optical elements, such as Fresnel lenses, can be used.

In the embodiment described with reference to the drawings, the small optical system is connected to the first condensing system (elements 23, 2
4, 25, and 26), a reflective element (element 27), and a second light collection system (including elements 28 and 29). The first and second light collection systems are each optimized to transmit image light from the input image display source to the reflective element or from the reflective element to the first portion using standard optical design techniques. Is done. Both light collection systems include optical elements to reduce light scattering as the light passes through the system. This optical element is designed to suppress chromatic aberration and monochromatic aberration when light passes through the second portion. Monochromatic aberrations include spherical aberration, coma, astigmatism, field curvature, and geometric distortion.

The small optical system described above is configured such that a visible image appears only in the input image panel 16 and the final output of the display. However, in another embodiment,
An intermediate image can be formed on the scattering screen at some location in the light path. This intermediate image can be a new effective input image for elements 19 and 20. Thereby, a large exit pupil can be used.

The combination of the holographic optical elements 19 and 20 is formed to suppress light scattering and aberration. Elements 19 and 20 are optimized such that their chromatic and monochromatic aberrations and distortions are compensated. In particular, element 20 is used primarily to achieve a favorable field of view because element 20 focuses light primarily to avoid monochromatic aberrations. However, large angles of incidence can result in off-axis aberrations (especially
Due to the increase in astigmatism, geometric distortion, keystone), the main purpose of each element of the part 17 of the optical system is to compensate for these distortions.

The system described above has the advantage that a switchable holographic optical element is used and a light optical element can be used near the eye. A typical head-mounted display system requires a number of optical elements near the eye to compensate for aberrations that occur when images are sent from off-axis positions to the eye. Usually, a large aperture image is needed near the eye to compensate for aberrations. The use of switchable holographic optics can reduce the weight of devices, especially near the eyes.

[0098] The aperture may include an aperture stop that determines the limit aperture. This aperture is preferably
It is located at or near the surface 26a of the lens element (that is, the central aspheric surface closest to the mirror 27), and has an oval shape. The aperture may be formed as a separate element (e.g., a plastic or metal plate with an appropriately sized opening) added to the system, or may be painted on the back of the element.

The above-described device has several advantages, including reduced size and reduced number of components in front of the user's eyes, and the weight of the device (for top-of-the-head type). Most of the time falls on the top of the user's head rather than the user's temporal. That is, while the projection optics are extremely off-axis, scattering and chromatic aberrations are minimized through the use of holographic diffraction elements that are capable of switching scattering and chromatic aberrations. If conventional optics were used instead of switchable holographic optics, a tilted off-axis aspheric lens, prismatic element,
And the addition of conventional optical elements, such as cylindrical elements. Additional optics that perform the function of a reflective eyepiece need to be large and heavy.

Although the device has been described using one eye of the user, a similar device can be attached to the other eye. In this case, each display screen uses either the exact same image or a stereoscopic pair of images. It is also possible to connect the casings 10 of both devices into an integrated headset. The integrated headset can take on a helmet-like shape. Alternatively, the integrated headset can be spectacle-shaped.

In addition to the video generated by the video generator 15, it is also possible to watch surrounding video. In this case, the surrounding image can be superimposed on the generated image, or only the surrounding image can be viewed. The shutter element 22 is located behind the reflective element 19 in front of the user's eyes. In order to see the surroundings, the shutter 22 is switched so as to transmit light rather than block light. In devices where the generated images cannot be viewed simultaneously, the holographic diffraction elements 19 and 20 are switched off. Alternatively, the shutter can be opened and the image can be projected to the user such that the image generated by the image generator overlaps the surrounding image.

FIG. 23 shows an embodiment of the optical system of the display device. This optical system comprises an image generator 15, an optical subassembly 17, and two diffractive elements 19
And 20. Element 20 is a transmissive element and element 19 is a reflective element. At least one of the element 19 and the element 20 is a holographic optical element. As the element other than the holographic optical element, a standard optical element such as a non-switching holographic optical element / diffractive optical element, a Fresnel optical element, a refractive optical element, or a reflective optical element can be used. The transmissive element 20 is formed such that a virtual image is generated only at the final output of the display. Alternatively, element 20 can be a transmissive diffusion screen. The small optical system 17 is configured such that the element 20 forms an actual intermediate image. This actual image is sent to the reflection element 19 through the screen, and becomes the final virtual image of the user. Alternatively, the system of FIG. 23 is configured to produce a direct view video. In this embodiment, the reflection element 19 can be a reflection diffusion screen. The final image is formed on the screen element 19 and sent to the opposite user as a virtual image.

In contrast to the system shown in FIG. 23, the system of FIG. 24 includes two reflection diffraction elements.
Elements 19 and 20 can both be reflection diffraction elements. Either element 19 or element 20 is a switchable holographic optical element. As the other element, a standard optical element such as a non-switching holographic optical element / diffractive optical element, a Fresnel optical element, a refractive optical element, or a reflective optical element can be used. The reflective element 20 is formed such that a virtual image is generated only at the final output of the display. Alternatively, element 20 can be a reflective diffuser screen. The small optical system 17 is configured such that the element 20 forms an actual intermediate image. This actual image is reflected from the screen to the reflective element 19 to provide the user with a final virtual image. Alternatively, element 19 can be a reflective diffusing screen and element 20 can be a reflective switchable holographic diffraction element. The final image is formed on the screen element 19, and the virtual image is sent to the opposite user.

In another embodiment, shown in FIG. 25, a switchable holographic optical element is used to form another layer on the switchable element 20 to generate a tiled image, Tile another image that can form a composite image. In order to achieve this, the transmissive elements are divided into two stacked transmissive elements 20a and 20a.
0b. The reflection elements are also two reflection elements 19a and 19b.
Can be formed from The reflective element is formed such that incident light is directed to the user's eyes. The transmissive elements are formed to diffract incident light from one reflective element to another. The transmissive diffraction element 20 can be a switchable element such that only one element transmits incident light at a time. By quickly switching the two elements alternately from active to inactive and from inactive to active,
It is possible for two different images to be visible to the user overlapping. This method of forming a tiled image is described in U.S. Patent No. 09 / 388,944, which is hereby incorporated by reference.

Alternatively, the device can be used as a device that combines imaging and display. Such a device is described in U.S. Patent No. 09 / 313,431, which is hereby incorporated by reference.

The device may comprise an eye tracker device comprising a plurality of emitters 2 arranged around the periphery of the element 19. Emitter 2 is formed to project radiation onto a wide range of liquid portions of eye 6. The projected radiation is reflected by the eye and travels to the detector 4. The signal from the detector 4 is processed in the processing device 20 to measure changes in the position of the eye 6 and sends data corresponding to those changes back to the video generator 15. In response, the image viewed by the observer moves in the direction of the observer, as the image generator 15 changes the image displayed by the device.

As the detector 4, a small two-dimensional detector array, a crossed one-dimensional detector array, or a peak intensity detector (such as a position sensing detector) can be used. In addition, the various elements of the eye tracker device and the wavelength of the radiation are selected such that they can be optimized to enable easy recognition and tracking of certain characteristics of the eye 4.

(Optical System Elements) The optical elements described below were used in the configuration of the display device shown in FIGS. These optical elements show examples of elements that can be attached to the head for image observation, but the present invention is not limited to these described elements, and the spirit and the spirit of the present invention are not limited thereto. It should be understood that various modifications and equivalent configurations are possible without departing from the scope. Also note that the elements of the optical system shown in FIG. 22 can be truncated by removing unused portions of the optical element when the optical element is located within the casing. FIG. 18 shows a similar optical element, but with the unused portion of the lens removed and provided in a more streamlined manner relative to the casing.

Optical Element 23 The optical element 23 is a spherical / aspherical lens made of an acrylic resin material. The lens has two surfaces, surface 23a facing the image generator and surface 23b
Faces in the direction opposite to the image generator (see FIG. 18). The acrylic resin material used to manufacture the lens has the following refractive index at the wavelength indicated. n (656.27 nm) = 1.488394 ± 0.0006 n (587.56 nm) = 1.491002 ± 0.0006 n (486.13 nm) = 1.496978 ± 0.0006 The surface 23b is a concave spherical surface having a radius of curvature of 204.375 mm. Surface 23
a is a polynomial asphere surface. Surface 23a is convex and has a radius of curvature of 16.927 mm. The deviation ("Sag (z)") of surface 23a from a spherical surface along the optical axis (defined as the z-axis) of the lens is defined by the following equation. Sag (z) = [(1 / R) * h ² ] / [1 + sqrt (1- (h / R) ² )] + Ah ⁴ + Bh ⁶ + Ch ⁸ where sqrt () is in parentheses Represents the square root of the value of. h ² = x ² + y ² , where x and y are equal to the Cartesian coordinates along the x and y axes of the lens element. R = −16.992694 A = 0.551681 × 10 ⁻⁴ B = 0.170580 × 10 ⁻⁶ C = 0.310 160 × 10 ^{−9 The} lens element 23 has a central thickness of 4.624 mm. 19.80 diameter from end to end
0 mm. When placed inside the casing, the effective aperture of the placed lens is 17.
4 mm.

Optical Element 24 The optical element 24 is a flat / aspherical lens made of an acrylic resin material. The lens has two surfaces, surface 24a facing the image generator and surface 24a.
b faces in the opposite direction to the image generator (see FIG. 18). The acrylic resin material used to manufacture the lens has the following refractive index at the wavelength indicated. n (656.27nm) = 1.488394 ± 0.0006 n (587.56nm) = 1.491002 ± 0.0006 n (486.13nm) = 1.496978 ± 0.0006 The cylindrical surface 24b is convex along the x-axis and has a radius of curvature of 25.63731mm . Surface 24a is a polynomial aspheric surface. Surface 24a is convex and has a radius of curvature of 68.952 mm. Surface 2 from a spherical surface along the optical axis of the lens (defined as the z-axis)
The deviation of 4a (“Sag (z)”) is defined by the following equation. Sag (z) = [(1 / R) * h ² ] / [1 + sqrt (1- (h / R) ² )] + Ah ⁴ + Bh ⁶ where sqrt () is the value in parentheses Represents the square root. h ² = x ² + y ² , where x and y are equal to the Cartesian coordinates along the x and y axes of the lens element. R = −68.95221 A = 0.156537 × 10 ⁻⁴ B = −0.167323 × 10 ^{−6 The} lens element 24 has a central thickness of 4.461 mm. End-to-end diameter is 23.00
0 mm. When placed inside the casing, the effective aperture of the placed lens is 20.
600 mm.

Optical Element 25 The optical element 25 is a spherical / aspherical lens made of an acrylic resin material. The lens has two surfaces, surface 25a facing the image generator and surface 25b
Faces in the direction opposite to the image generator (see FIG. 18). The acrylic resin material used to manufacture the lens has the following refractive index at the wavelength indicated. n (656.27 nm) = 1.488394 ± 0.0006 n (587.56 nm) = 1.491002 ± 0.0006 n (486.13 nm) = 1.496978 ± 0.0006 The surface 25b is a convex spherical surface having a radius of curvature of 138.955 mm. Surface 25a
Is a polynomial aspherical surface. Surface 25a is convex and has a radius of curvature of 11.813 mm. The deviation of the surface 25a from the spherical surface along the optical axis (defined as the z-axis) of the lens ("Sa
g (z) ") is defined by the following equation. Sag (z) = [(1 / R) * h ² ] / [1 + sqrt (1- (1 + K) * (h / R) ² )] + Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ here And sqrt () represents the square root of the value in parentheses. h ² = x ² + y ² , where x and y are equal to the Cartesian coordinates along the x and y axes of the lens element. R = −1.181344 K = −1.807381 A = −0.285278 × 10 ⁻⁴ B = 0.209903 × 10 ⁻⁶ C = −0.502354 × 10 ⁻⁹ D = 0.425282 × 10 ^{−12 The} lens element 25 has a center thickness of 14.000 mm. Have. End to end diameter 36.8
00 mm. When placed inside the casing, the effective aperture of the placed lens is 34
It is .400mm.

Optical Element 26 The optical element 26 is a spherical / aspherical lens made of an acrylic resin material. The lens has two surfaces, surface 26a facing the image generator and surface 26b
Faces in the direction opposite to the image generator (see FIG. 18). The acrylic resin material used to manufacture the lens has the following refractive index at the wavelength indicated. n (656.27 nm) = 1.488394 ± 0.0006 n (587.56 nm) = 1.491002 ± 0.0006 n (486.13 nm) = 1.496978 ± 0.0006 The surface 26 b is a convex spherical surface having a radius of curvature of 101.398 mm. Surface 26a
Is a polynomial aspherical surface. Surface 26a is convex and has a radius of curvature of 145.335 mm. Deviation of surface 26a from a spherical surface along the optical axis of the lens (defined as the z-axis) ("
Sag (z) ”) is defined by the following equation. Sag (z) = [(1 / R) * h ² ] / [1 + sqrt (1- (h / R) ² )] + Ah ⁴ + Bh ⁶ + Ch ⁸ where sqrt () is in parentheses Represents the square root of the value of. h ² = x ² + y ² , where x and y are equal to the Cartesian coordinates along the x and y axes of the lens element. R = 101.39766 A = −0.351519 × 10 ⁻⁴ B = −0.501521 × 10 ⁻⁶ C = 0.363217 × 10 ^{−8 The} lens element 26 has a central thickness of 3.000 mm. 13.80 end-to-end diameter
0 mm. When placed inside the casing, the effective aperture of the placed lens is 11.
4 mm.

Optical Element 27 The optical element 27 is a flat / cylindrical mirror made of glass. The mirror has two surfaces, surface 27a facing in the direction of the image generator and surface 27b facing in the opposite direction to the image generator (see FIG. 18). The surface 27a is a flat surface. Surface 27a is covered with a highly reflective coating that has a maximum reflectance at 460-628 nm. Surface 27b is cylindrical along the x-axis and has a convex 69.000 mm radius of curvature. Mirror 27 has a central thickness of 4.000 mm. The diameter from end to end is 26.000 mm. When disposed in the casing, the effective diameter of the disposed mirror is 23.600 mm.

Optical Element 28 The optical element 28 is a spherical / aspherical lens made of an acrylic resin material. The lens has two surfaces, surface 28a facing the image generator and surface 28b
Faces in the direction opposite to the image generator (see FIG. 18). The acrylic resin material used to manufacture the lens has the following refractive index at the wavelength indicated. n (656.27 nm) = 1.488394 ± 0.0006 n (587.56 nm) = 1.491002 ± 0.0006 n (486.13 nm) = 1.496978 ± 0.0006 The surface 28b is a convex spherical surface having a radius of curvature of 60.612 mm. Surface 28a is a polynomial aspheric surface. Surface 28a is convex and has a radius of curvature of 25.510 mm. Deviation of surface 28a from a spherical surface along the optical axis (defined as the z-axis) of the lens ("Sag (
z))) is defined by the following equation. Sag (z) = [(1 / R) * h ² ] / [1 + sqrt (1- (h / R) ² )] + Ah ⁴ + Bh ⁶ + Ch ⁸ where sqrt () is in parentheses Represents the square root of the value of. h ² = x ² + y ² , where x and y are equal to the Cartesian coordinates along the x and y axes of the lens element. R = 25.51037 A = −0.155134 × 10 ⁻⁴ B = 0.288638 × 10 ⁻⁶ C = −0.569516 × 10 ^{−8 The} lens element 28 has a central thickness of 13.365 mm. End-to-end diameter is 43.0
00 mm. When placed inside the casing, the effective aperture of the placed lens is 40
It is .600mm.

Optical Element 29 The optical element 29 is a cylindrical / aspherical lens made of an acrylic resin material. The lens has two surfaces, surface 29a facing in the direction of the image generator and surface 29a.
b faces in the opposite direction to the image generator (see FIG. 18). The acrylic resin material used to manufacture the lens has the following refractive index at the wavelength indicated. n (656.27nm) = 1.488394 ± 0.0006 n (587.56nm) = 1.491002 ± 0.0006 n (486.13nm) = 1.496978 ± 0.0006 The surface 29b is cylindrical along the x-axis and has a convex radius of curvature of 47.13109mm. The surface 29a is a polynomial aspheric surface. Surface 29a is convex and has a radius of curvature of 54.966 mm. Surface 2 from a spherical surface along the optical axis of the lens (defined as the z-axis)
The deviation of 9a (“Sag (z)”) is defined by the following equation. Sag (z) = [(1 / R) * h ² ] / [1 + sqrt (1- (h / R) ² )] + Ah ⁴ + Bh ⁶ + Ch ⁸ where sqrt () is in parentheses Represents the square root of the value of. h ² = x ² + y ² , where x and y are equal to the Cartesian coordinates along the x and y axes of the lens element. R = −54.96615 A = 0.215568 × 10 ⁻⁴ B = −0.18402 × 10 ⁻⁷ C = 0.280821 × 10 ^{−10 The} lens element 29 has a central thickness of 3.000 mm. 31.60 diameter from end to end
0 mm. When placed inside the casing, the effective aperture of the placed lens is 29.
2 mm.

While the invention has been described with respect to particular embodiments, it is to be understood that the embodiments are illustrative only and are not limiting upon the scope of the invention. Those skilled in the art will be able to make any changes, modifications, additions and improvements to the above-described embodiments without departing from the scope of the claims herein.

[Brief description of the drawings]

FIG. 1. Exposed polymer dispersed liquid crystal (PLDC) made according to the instructions disclosed herein.
FIG. 4 is a cross-sectional view of a hologram made of a material and capable of being electrically switched.

FIG. 2 shows the normalized net transmittance and normalized net diffraction efficiency of a hologram made according to the instructions disclosed herein (without adding a surfactant) to the rms voltage applied to the hologram. The graph shown with respect to FIG.

FIG. 3 is a graph of minimum diffraction efficiency vs. rms voltage frequency showing the threshold and full switching rms voltage required to switch holograms made in accordance with the instructions disclosed herein.

FIG. 4: PLDC material using 34% by weight of liquid crystal in the presence of surfactant and 29
5 is a graph of normalized diffraction efficiency as a function of applied electric field for PLDC material using% liquid crystal as well as 4% by weight surfactant.

FIG. 5 is a graph showing switching response time characteristics of a diffracted beam for the PLDC material containing the surfactant of FIG.

FIG. 6 is a graph showing the normalized net transmittance and normalized net diffraction efficiency of a hologram.

FIG. 7 is a three-dimensional view showing a typical configuration for an experiment for recording a reflective diffraction grating.

FIG. 8a is a three-dimensional view of a reflective grating having periodic surfaces of polymer channels and PLDC channels parallel to the front surface, with no applied electric field, made according to the instructions disclosed herein. The liquid crystal used in the construction of the diffraction grating has a positive dielectric anisotropy.

FIG. 8b is a three-dimensional view of a reflective grating having a periodic plane of polymer channels and PLDC channels parallel to the front surface, with an applied electric field, made according to the instructions disclosed herein. The liquid crystal used in the construction of the diffraction grating has a positive dielectric anisotropy.

FIG. 9a is a three-dimensional view of a reflective grating having a periodic plane of polymer channels and PLDC channels parallel to the front surface of the grating, with no electric field applied, as indicated by the instructions disclosed herein. The liquid crystal used in the construction of the diffraction grating manufactured according to the above has negative dielectric anisotropy.

FIG. 9b is a three-dimensional view of a reflective diffraction grating having a periodic plane of polymer channels and PLDC channels parallel to the front surface of the grating, with an applied electric field, showing the instructions disclosed herein. The liquid crystal used in the construction of the diffraction grating manufactured according to the above has negative dielectric anisotropy.

FIG. 9c is a chemical formula of a liquid crystal material.

FIG. 9d is a chemical formula of a liquid crystal material.

FIG. 10a is a three-dimensional view of a reflective grating made in accordance with the instructions disclosed herein and disposed within a Helmholtz coil.

FIG. 10b is a three-dimensional view of the reflective diffraction grating shown in FIG. 10a with no electric field applied.

FIG. 10c is a three-dimensional view of the reflective diffraction grating shown in FIG. 10a with an electric field applied.

FIG. 11a is a side view of an oblique transmission grating showing the direction of the grating vector G in the periodic plane of the polymer and PLDC channels.

FIG. 11b is a side view of an oblique reflection type diffraction grating showing the direction of a grating vector G of a periodic surface of a polymer channel and a PLDC channel.

FIG. 12 is a three-dimensional view of a reflective diffraction grating made according to the instructions disclosed herein with a shear stress field applied.

FIG. 13 shows a polymer channel and PL arranged orthogonal to the front face of the diffraction grating
FIG. 2 is a three-dimensional view of a sub-wavelength grating made according to the instructions disclosed herein, such as having a periodic face of a DC channel.

FIG. 14a is a three-dimensional view of a sub-wavelength grating made according to the instructions disclosed herein, acting as a half-wave plate such that the polarization direction of the incident light rotates 90 degrees.

FIG. 14b is disposed between polarizers that intersect each other to transmit incident light
3D is a perspective view of the switchable half-wave plate shown in FIG.

FIG. 14c shows a switchable half-wavelength shown in FIG. 14b in which a voltage is applied to the half-wave plate so that the polarization direction of the incident light does not rotate and the incident light is blocked by a second polarizer. The side view which shows a plate and the polarizer which crosses mutually.

FIG. 14d shows a switchable half-wavelength shown in FIG. 14b in which a voltage is applied to the half-wave plate so that the polarization direction of the incident light does not rotate and the incident light is blocked by a second polarizer. The side view which shows a plate and the polarizer which crosses mutually.

FIG. 15a: the sub-wavelength diffraction grating functions as a quarter-wave plate so that plane-polarized light is transmitted through the sub-wavelength diffraction grating, retroreflected by a mirror, and reflected by a beam splitter; FIG. 4 is a side view of a subwavelength diffraction grating made according to the instructions disclosed herein.

15b is a side view of the switchable quarter-wave plate shown in FIG. 15a, wherein applying a voltage to the quarter-wave plate prevents the polarization state of the light from changing; This indicates that the reflected light has passed through the beam splitter.

FIG. 16a: polymer channels and PL arranged orthogonal to the front face of the diffraction grating
FIG. 4 is a three-dimensional view of a transmission grating having a DC channel periodic surface and no applied electric field, wherein the liquid crystal used in the construction of the grating made according to the instructions disclosed herein is positive. Having a dielectric anisotropy of

FIG. 16b: polymer channels and PL arranged orthogonal to the front face of the diffraction grating
FIG. 4 is a three-dimensional view of a transmission grating with a DC channel periodic surface and an applied electric field, wherein the liquid crystal used in the construction of the grating made according to the instructions disclosed herein is positive. Having a dielectric anisotropy of

FIG. 17 is a side view of a sub-wavelength diffraction grating in which the diffraction gratings are stacked and electrically connected in parallel so that the switching voltage of the sub-wavelength diffraction grating is reduced.

FIG. 18 is a cross-sectional view of a device for viewing an image.

FIG. 19 is a schematic side view of one embodiment of an image generator.

FIG. 20 is a perspective view of a switchable holographic optical element of the device.

FIG. 21 is a perspective view of a casing of the device.

FIG. 22 is a schematic diagram of a switchable holographic optical element of the device, showing ray tracing through the optical element.

FIG. 23 is a schematic diagram of one embodiment of an apparatus for viewing an image that includes transmissive and reflective optical elements.

FIG. 24 is a schematic diagram of one embodiment of an apparatus for viewing an image that includes two reflective optical elements.

FIG. 25 is a schematic diagram of one embodiment of an apparatus for viewing tiled video.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/1334 G02F 1/1334 G03H 1/02 G03H 1/02 H04N 5/64 511 H04N 5/64 511A ( 81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG , BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT , RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Walder, Jonathan Dee, 94024 Los Altos Hills Old Ranch Road, California, USA 1491 (72) Inventor Street, John G. Nottinghamshire Eng. 8, UK 2 2SB Wolaton Charle Cotedra Eve 66 F term (reference) 2H049 CA01 CA05 CA09 CA15 CA22 CA28 CA30 2H087 KA07 KA23 LA11 RA05 RA07 RA12 RA13 RA45 RA46 TA01 TA04 UA01 UA09 2H089 HA04 HA40 QA11 QA13 RA04 TA09 TA11 UA00 2K008 AA03 BB04 BB04 DD05 HH12 HH13 HH14 HH18 HH20 HH26 HH27

Claims (25)

[Claims] An optical system configured to transmit image light to a user's eye, the optical system configured to operate in an active state or an inactive state. A holographic optical element, wherein the first switchable holographic optical element is configured to diffract incident light when operating in the active state, and substantially diffract incident light when operating in the inactive state. An apparatus comprising: an optical system that transmits light without any change; and a casing that is provided inside at least a part of the optical system and that can be mounted on the head of the user. 2. The optics further comprising a second switchable holographic optical element configured to operate in an active state or an inactive state, wherein the second switchable holographic optical element is 2. The apparatus of claim 1, wherein the apparatus is configured to diffract incident light when operating in the active state, and transmit the incident light substantially unchanged when operating in the inactive state. Equipment. 3. The first switchable holographic optical element has a first surface, the first surface configured to receive incident light, wherein the first switchable holographic optical element is configured to receive incident light.
3. The apparatus of claim 2, wherein incident light diffracted by said switchable holographic optical element emerges from said first surface. 4. The holographic optical element of claim 2, wherein the optical system is configured to operate in an active state or an inactive state, and wherein the optical system is configured to operate in the active state. A second switchable holographic optical element configured to diffract wide-band incident light and transmitting the second-bandwidth incident light substantially unaltered when operating in the inactive state. A third switchable holographic optical element configured to operate in an active or inactive state, wherein the third switchable holographic optical element is configured to diffract third incident light when operating in the active state. Transmitting a third bandwidth of incident light substantially unchanged when operating in the inactive state. Further comprising: a switchable holographic optical element, wherein the first switchable holographic optical element is configured to diffract first bandwidth incident light when operating in the active state; 2. The apparatus of claim 1 wherein the third bandwidth incident light is transmitted substantially unaltered when operating in. 5. The system of claim 1, wherein the optical system is configured to diffract the first bandwidth incident light when operating in the active state, and substantially diffract the first bandwidth incident light when operating in the inactive state. A fourth switchable holographic optical element, characterized in that it transmits without any change, and a fifth switchable holographic optical element, configured to operate in an active or inactive state. Wherein the second bandwidth incident light is configured to diffract when operating in the active state and transmit the second bandwidth incident light substantially unchanged when operating in the inactive state. A fifth switchable holographic optical element, characterized in that the fifth switchable holographic optical element is configured to operate in an active or inactive state. Six switchable holographic optical elements, configured to diffract third incident light when operating in the active state, and for diffusing third bandwidth incident light when operating in the inactive state. 5. The apparatus according to claim 4, further comprising a sixth switchable holographic optical element characterized by transmitting substantially unchanged. 6. The first, second, and third switchable holographic optical elements, wherein each of the first, second, and third switchable holographic optical elements has a first surface. Each configured to diffract incident light received at the first surface, wherein incident light diffracted by the first switchable holographic optical element emerges from the first surface;
Incident light diffracted by the second switchable holographic optical element emerges from the first surface, and incident light diffracted by the third switchable holographic optical element emerges from the first surface. The device according to claim 4, characterized in that: 7. The holographic recording medium according to claim 1, wherein the first holographic optical element has a holographic recording medium for recording a hologram, wherein the holographic recording medium comprises: a monomer dipentaerythritol hydroxypentaacrylate; a liquid crystal; The device of claim 1, comprising an agent and a photoinitiator dye. 8. The apparatus of claim 1, wherein said first switchable holographic optical element comprises a thick phase hologram recorded in a holographic recording medium. 9. The apparatus of claim 1, wherein said first switchable holographic optical element comprises a thin phase hologram recorded in a holographic recording medium. 10. The first switchable holographic optical element has a holographic recording medium, a hologram is recorded in the holographic recording medium, and a polymer dispersed liquid crystal is occupied by liquid crystal droplets. The hologram is formed during the hologram recording process by undergoing phase separation to create areas and to create areas of transparent photopolymer interspersed by areas occupied by liquid crystal droplets. The device according to claim 1, characterized in that: 11. The apparatus of claim 1, further comprising an image generator configured to generate the image light therein. 12. The apparatus according to claim 11, wherein the image generator generates a color image. 13. The image generator further comprising an image generator configured to generate image light, wherein the image generator has a light source and a display screen, wherein the light source generates light from the light source. 2. The device according to claim 1, wherein the device is arranged to illuminate the image generated above. 14. The apparatus of claim 13, wherein said light source comprises an array of lasers. 15. The apparatus according to claim 13, wherein said display screen comprises a liquid crystal display panel. 16. The device of claim 13, wherein said display screen comprises a reflective silicon backplane device. 17. The optical system includes a small optical system (Optical Subassembly) configured to receive the image light, wherein the small optical system is configured to reduce dispersion of the image light, and the small optical system is configured to receive the image light. The apparatus according to claim 1, wherein the apparatus is configured to reduce optical aberrations in the image light. 18. The optical system includes a first light-collecting system, a second light-collecting system, and a reflection optical element, wherein the first light-collecting system receives image light and reflects the image light. The reflective optical element is configured to reflect the image light received from the first condenser system to the second condenser system, and the second optical system is configured to reflect the image light received by the first condenser system to the second condenser system.
18. The apparatus according to claim 17, wherein the light condensing system is configured to receive and transmit image light provided by the reflective optical element. 19. The apparatus of claim 1, wherein the casing is configured to be worn along a side of the user's head. 20. The apparatus of claim 1, wherein the casing is configured to be mounted on an upper part of the user's head. 21. The second switchable holographic optical element has a second surface, the second surface configured to receive incident light, and diffracted by the second switchable holographic optical element. Apparatus according to claim 3, wherein the incident light emerges from its second surface. 22. The second switchable holographic optical element has opposing first and second surfaces, the first surface of the second switchable holographic optical element for receiving incident light. 4. The apparatus of claim 3 wherein the incident light configured and diffracted by the second switchable holographic optical element emerges from the second surface thereof. 23. The optical system further comprising a first non-switching holographic optical element configured to operate only in an active state,
The apparatus of claim 1, wherein the non-switching holographic optical element is configured to diffract incident light. 24. An optical system configured to transmit light emitted from an image toward a user's eye, wherein the optical system has first and second portions, and wherein the first portion is provided. Is provided at one end of the optical system on a side close to the eye of the user so that light transmitted from the first portion is transmitted to the eye of the user when used, An optical system, wherein a portion of the optical system is connected to the first portion, and the second portion is configured to receive the light transmitted from the image and transmit the light to the first portion. A casing mountable on the head of the user having the optical system therein, wherein the first portion comprises a first switchable holographic optical element and a second switchable holographic optical element. Having The first and second switchable holographic optical elements are both configured to operate in an active state or an inactive state, and when the first switchable holographic optical element operates in an active state, to diffract incident light. And configured to transmit incident light without substantial diffraction when operating in the inactive state, and to reflect the incident light when the second switchable holographic optical element operates in the active state; The first switchable holographic optical element receives light from the second portion and transmits the incident light without substantial reflection when operating in the inactive state and the second switchable holographic optical element. A second switching device arranged to direct the light to a holographic element. A holographic element capable of receiving light from the first switchable holographic optical element and reflecting the light to the eye of the user, wherein the second portion has small optics. The small optical system is configured to transmit through the second portion, the small optical system is configured to reduce dispersion of light passing through the second portion, and the small optical system is configured to transmit the light through the second portion. An apparatus configured to reduce optical aberrations in a projected image. 25. The image processing apparatus further comprising: an image generator configured to generate the image, wherein the image generator is connected to the second part, the image generator has a light source and a display screen, 25. The apparatus of claim 24, wherein light generated by a light source illuminates the image generated on the display screen and the light source is arranged to be reflected to the optical system.