Abstract: A first HOE and a second HOE are respectively arranged on two opposite faces of an optical waveguide member. The first HOE diffracts light incident from the outside on the optical waveguide member such that the light is then totally reflected inside the optical waveguide member and is thereby directed to the second HOE. The second HOE diffracts, according to the diffraction efficiency thereof, part of the light incident thereon after being guided inside the optical waveguide member such that this part of the light is then emitted to the outside substantially parallel to the light incident on the optical waveguide member, and the second HOE simultaneously totally reflects the rest of the light incident thereon. The second HOE repeats such emission and total reflection. The first and second HOEs each have interference fringes with n different pitches (where n is a natural number equal to or greater than two) to diffract light of n different wavelengths at substantially equal angles.

Abstract: Variation of the wavelength of the light emitted from a light source is reduced by a wavelength variation reduction mechanism. Hence, wavelength deviation of the intensity peak of the light emitted from the light source from the diffraction-efficiency peak of a hologram optical element is reduced. Thus, even when a high-brightness light source is used, the light emitted therefrom can be diffracted with the hologram optical element efficiently. Moreover, the heat generated by the light source is efficiently rejected through the surface of a land portion of a flexible printed circuit, is then, via an insulating layer of the flexible printed circuit, efficiently absorbed through the surface of a heat absorbing member, and is then, via a shield conductor, led out of a casing, so as to be thereby expelled.

Abstract: A hologram optical element is formed on a substrate so as to make an optical device. The hologram optical element is formed in an area smaller than an irradiation area of a beam for reproduction such as image light or object light on the substrate. Supposing that the beam for reproduction is made of a center beam having intensity higher than 50% of center intensity and other peripheral beam, the hologram optical element is formed on the substrate in a size for diffracting only the center beam so that a flare or a ghost can be relieved without using additional optical elements such as a shading plate.

Abstract: The light directed from a light source to a concave mirror and the light directed from a display device to an eyepiece optical system are intersected by each other in a layout. This allows the light source, the concave mirror, and the display device to be arranged in compactness adjacent to the eyepiece optical system without increasing the optical power of an illumination optical system. As the result, the apparatus can easily be minimized in the thickness or the overall size. A hologram optical element is provided where the relationship between the wavelength range ??1 at half of the diffraction efficiency of each of the three primary colors of the light in the hologram optical element and the wavelength range ??2 at half of the intensity of each of the three primary colors of the light emitted from the light source is defined by ??1<??2.

Abstract: An arrangement of the invention includes a base block 16, a cylindrical cam 14, as a rotary member, which is rotatably supported on the base block 16, and includes a contact portion on an outer periphery thereof for outputting a rotating force, a drive gear 21, as an oscillatory ring, which includes a contact portion on an inner periphery thereof, and is oscillated on a plane perpendicular to a rotation axis of the cylindrical cam 14 in contact with the contact portion of the cylindrical cam 14, parallel springs 23 through 26, as a position retainer, for retaining the position of the drive gear 21, and three or more shape metal alloy actuators (SMA) wires 35 through 38, as expandable and contractible actuators, with both ends of the each SMA wire being fixed to the base block 16 for contact with the drive gear 21.

Abstract: A drive for operating a movable part with respect to a fixed part includes: a driving member having a linear shape and being made of a shape-memory alloy; and a crimp terminal for holding one end of the driving member at the fixed part or the movable part. At least a part to which the driving member is crimped in the crimp terminal is made of stainless steel.

Abstract: In an image display apparatus, two light sources emit illumination light having different wavelengths, with which a liquid crystal display device is illuminated. By modulating the illumination light, the liquid crystal display device produces a first and a second image light having different wavelengths. Two holographic optical elements respectively reflect the first and second image lights and direct them to the user's eye so that virtual images of the images represented by the first and second image lights are formed at different positions. As the light source from which to obtain the illumination light is switched between the two, the dioptric power with which to present an image is changed.

Abstract: An I image display apparatus has a display portion that displays an optical image, a combiner that reflects light from said display portion to thereby enlarge an optical image represented by the light, and transmits light from an ambient object; and a display unit including a transparent plate-form holding member that holds said combiner. The image display apparatus is used with the combiner situated in front of a user's eye, and provides an enlargement of the optical image displayed by the display portion, so as to be superimposed on an optical image of the ambient object. And the transparent plate-form diopter adjusting member is provided that has an optical power and is attached to the display unit so as to be situated between the eye and the holding member.

Abstract: An image display apparatus has a reflective display element for displaying a two-dimensional image on a display plane, a light source for emitting illuminating light for illuminating said display plane, a magnifier optical system for magnifying and projecting said two-dimensional image, and an optical member which is composed of a medium having a refractive index greater than or equal to unity and has at least three optical planes of a first plane, a second plane, and a third plane. The magnifier optical system is substantially in concentricity with said display plane; the illuminating light from said light source passes through said first plane and then through said second plane, thereby illuminating said display plane; and the reflected light from said display plane passes through said second plane and is then reflected in said first plane, thereby passing through said third plane and being incident on said magnifier optical system.

Abstract: A bilaterally conjugate telecentric optical system has, sequentially from one conjugate side, a first lens unit in the form of an afocal optical system including sequentially from one conjugate side a first subunit having positive optical power and a second subunit having positive optical power, and having an aperture stop fixed in the optical axis direction at the focal position on the back side of the first subunit; and a second lens unit in the form of an afocal optical system that is movable in the optical axis direction to adjust the focus while maintaining a telecentric state.

Abstract: An image display apparatus has a reflective display element for displaying a two-dimensional image on a display plane, a light source for emitting illuminating light for illuminating said display plane, a magnifier optical system for magnifying and projecting said two-dimensional image, and an optical member which is composed of a medium having a refractive index greater than or equal to unity and has at least three optical planes of a first plane, a second plane, and a third plane. The magnifier optical system is substantially in concentricity with said display plane; the illuminating light from said light source passes through said first plane and then through said second plane, thereby illuminating said display plane; and the reflected light from said display plane passes through said second plane and is then reflected in said first plane, thereby passing through said third plane and being incident on said magnifier optical system.

Abstract: An I image display apparatus has a display portion that displays an optical image, a combiner that reflects light from said display portion to thereby enlarge an optical image represented by the light, and transmits light from an ambient object; and a display unit including a transparent plate-form holding member that holds said combiner. The image display apparatus is used with the combiner situated in front of a user's eye, and provides an enlargement of the optical image displayed by the display portion, so as to be superimposed on an optical image of the ambient object. And the transparent plate-form diopter adjusting member is provided that has an optical power and is attached to the display unit so as to be situated between the eye and the holding member.