Abstract: A fixed focal length, wide-angle lens includes, in order from the object side, a negative first lens group that includes a plastic negative lens element, a positive second lens group that includes a plastic positive lens element, a positive third lens group that includes a positive lens element joined on its image side to another lens element, and a positive fourth lens group. In the preferred embodiments, all lens groups except the third lens group are single lens elements that each include an aspheric lens surface. Also, the wide-angle lens preferably satisfies specified conditions that, together with the use of plastic lenses, joined lens elements, and aspheric surfaces, enables a high performance, compact, wide-angle lens of relatively simple construction to be produced.

Abstract: A polarizing illumination optical system includes a light source with a parabolic reflector with a light emitter at its focal point so that the light source emits substantially collimated light toward a polarization conversion optical system that separates the light into two polarizations, converts the light to a single polarization, and projects the light through an optical integrator that includes two integrating plates so as to provide a more uniform intensity light beam. The polarization conversion optical system satisfies the following condition: 4 f<D<7 f, where f is the focal length of the parabolic reflector, and D is the minimum width of the optical incidence aperture of the polarization conversion optical system. A projection display device uses the polarizing illumination optical system to illuminate modulators, such as LCDs, that provide different color image components that a projection lens projects on a screen to provide a full color image.

Abstract: An imaging lens of fixed focal length is formed of, in order from the object side, an aperture diaphragm, a first lens component having positive refractive power and having at least one aspheric lens surface, and a second lens component having positive refractive power and having at least one aspheric lens surface. The imaging lens satisfies two specified conditions so as to favorably correct distortion and curvature of field while providing a sufficient distance from the imaging lens to the exit pupil of the imaging lens. In addition, one or more of the lens components may each be formed of a single lens element.

Abstract: A projection optical system that is telecentric or very nearly telecentric on both sides is formed of four positive lens groups with a central diaphragm for achieving at least very nearly unity magnification. The second and third lens groups are movable along the optical axis of the projection optical system, preferably at the same rate and in the same direction, in order to vary the magnification of the projection optical system. The range of movement of the second and third lens groups includes a position where the first and second lens groups together are a mirror image about the plane of the diaphragm of the third and fourth lens groups together. A projection exposure device uses the projection optical system to form an image of an illuminating beam modulated by a mask pattern on a workpiece. An image magnification detector controls movement of the second and third lens groups.

Abstract: An illuminating optical system includes a light source that produces a light beam generally parallel to its optical axis toward a pair of fly-eye lenses in optical series for mixing light in the light beam in order to provide more uniform illumination. A condensing optical system converges and deflects the light from the fly-eye lens at an angle to a generally planar reflective display device, such as a liquid crystal display device. The fly-eye lenses and the reflective display device are parallel or nearly parallel to one another. The fly-eye lenses may be centered on the optical axis of the light source, and the optical axis of the light source may be parallel, or nearly parallel, to the direction that light from the reflective display device is reflected. A projection display device may include a projection lens that focuses the light from the reflective display device onto a screen.

Abstract: An autofocus system for an imaging device that includes an image detecting element for image production at a focused image plane of an adjustable focus imaging lens that also includes four image detecting elements for focus detection arranged in pairs that are equidistant in front of, and behind, planes that are conjugate with the focused image plane. One pair of image detecting elements for focus detection are farther than the other pair from the conjugate planes and may be used alone for focusing based on the stop value or focal length of the adjustable focus imaging lens. Alternatively, the other pair of image detecting elements may be used for more accurate focusing after the one pair of image detecting elements is used. The use of two pairs of image detecting elements at different distances from the focused image plane provides accurate focusing over a wide range of object distances.

Abstract: A zoom lens includes, in order from the enlarging side: a first lens group that has negative refractive power, is movable for focusing, and is stationary during zooming; second, third, and fourth lens groups that are movable for zooming; and a fifth lens group that is stationary during zooming. The second, third, fourth, and fifth lens groups have positive refractive powers. The second, third, and fourth lens groups move nearer the enlarging side when the zoom lens zooms toward the telephoto end. The ratios of the focal lengths of the first, first through third, fourth, and fifth lens groups to the focal length of the zoom lens satisfy four conditions. The fourth lens group is a biconvex lens element. A projection display device uses the zoom lens.

Abstract: A single focus lens is disclosed that is formed of only three lens components. In order from the object side, these are: a first lens component that has positive refractive power and includes a first lens element; an aperture diaphragm; a second lens component that has positive refractive power, at least one aspheric lens surface, and includes a second lens element made of plastic; and a third lens component that has positive refractive power, at least one aspheric lens surface, and includes a third lens element made of plastic. The following condition is satisfied: 1.0<f1/f<5.0 where f1 is the focal length of the first lens component, and f is the focal length of the single focus lens.

Abstract: A zoom lens includes, in order from the enlarging side, a first lens group that has negative refractive power, is movable for focusing, and is stationary during zooming, second, third, fourth, and fifth lens groups that are movable for zooming, and a sixth lens group that is stationary during zooming. The second, fourth, and sixth lens groups have positive refractive power and the fifth lens group has negative refractive power. The second and fourth lens groups move nearer the enlarging side when the zoom lens zooms toward the telephoto end, and the fifth lens group is nearer the enlarging side at the zoom lens telephoto end than at the zoom lens wide-angle end. The ratios of the focal lengths of the first, third, and fifth lens groups to the focal length of the zoom lens satisfy three conditions. A projection display device uses the zoom lens.

Abstract: A reference lens for an interferometer is constructed so that light transmitted by a partially reflecting reference spherical surface may be converged, toward a focal point that coincides with the center of curvature of the reference spherical surface, and reflected from a subject spherical surface that also has its center of curvature at the focal point. Measurement of the shape of the subject spherical surface is possible based on the interference of two light beams, one reflected by the subject spherical surface and one reflected by the reference spherical surface. The reference lens, which may include five or six lens components or lens elements, includes a negative meniscus lens component, a positive lens group, and a positive lens component. Specified conditions are satisfied to provide a reference lens that has favorable correction of aberrations, is compact, and can measure the surface accuracy of a wide range of convex spherical surfaces.

Abstract: An imaging lens includes, in order from the object side, a positive meniscus first lens component with its convex lens surface on the object side, a positive meniscus second lens component with its convex lens surface on the image side, and a negative third lens component with its concave lens surface on the image side. At least both lens surfaces of the negative third component are aspheric, and all six lens surfaces of the three lens components may be aspheric. The negative refractive power of the third lens component gradually decreases from the center of the third lens component toward the periphery of said third lens component and the peripheral region of the third lens component, outside 70% of its radius, has positive refractive power. The imaging lens may consist of only three lens components or elements. A diaphragm is positioned between the first and second lens components.

Abstract: A retrofocus wide-angle lens is formed of only three lens groups, in order from the object side, a first lens group of negative refractive power, a second lens group that includes a stop, and a third lens group of positive refractive power. The first lens group is at the object end of the retrofocus wide-angle lens and includes, in order from the object side, a plurality of negative lens components and a plurality of positive lens components. The first lens group includes three lens groups with particular lens features, the first of which, from the object side, also includes two lens groups with particular features. Various combinations of lens elements satisfy two conditions for ratios of absolute values of focal lengths for the various combinations of lens elements that assist in achieving excellent imaging.

Abstract: An imaging optical system includes at least one ghost image prevention element. Ghost images are prevented even when the imaging optical system includes an optical element that has at least one planar surface that is generally orthogonal to an optical axis of the imaging optical system, and is located in a light flux area with at least a central portion of the light flux area being generally parallel to the optical axis. The ghost image prevention element is especially useful in video cameras and digital cameras that use an image sensor having a planar surface that exhibits a high coefficient of reflection. The ghost image prevention element includes one planar surface, that is “tightly bound” to the planar surface of the optical element, and another surface that is curved so as to satisfy a given condition. The curved surface diffuses light that would otherwise contribute to a ghost image.

Abstract: A projection-type image display device includes a light source, converging optics, a rod integrator having a first optical axis, a light deflecting structure, and a light beam separating structure. The light beam separating structure directs light to a digital micromirror device and modulated light from the digital micromirror device along a second optical axis of a projection lens that projects an image formed by the modulated light on a screen. The rod integrator is between the light beam separating structure and the projection lens in the direction of the second optical axis and is outside the optical path of the modulated light beam from the digital micromirror device. The rod integrator may include a solid rod member and a leaky ray shielding member at least at one of the entrance end, the exit end, and around the solid rod member. The converging optics may include a parabolic reflector and an aspheric lens.

Abstract: A three-group zoom lens includes, in order from the object side, a first lens group of negative refractive power, and second and third lens groups, each of positive refractive power. The first and second lens groups include negative and positive components and the third lens group is a single lens component. All but one lens component may be a single lens element. When zooming from the wide-angle end to the telephoto end, the first and second lens groups move closer together while the second lens group moves farther from the third lens group. The third lens group remains stationary during zooming but moves for focusing. The second lens group includes a diaphragm on its object side. Aspheric lens surfaces are disclosed. The zoom lens satisfies certain conditions for the focal lengths of the zoom lens and a component of the zoom lens, and for Abbe numbers of two lens elements.

Abstract: A five-group zoom lens is formed of, in order from the enlarging side of the zoom lens, a negative first lens group that is movable for focusing and that is stationary during zooming, a positive second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group that is stationary during zooming. The second lens group, the third lens group, and the fourth lens group move relative to one another and relative to the first and fifth lens groups during zooming. The second lens group includes a negative lens component that has a concave lens surface on the reducing side of the zoom lens. The zoom lens satisfies various conditions and may be used in a projection display device or an image pickup device such as a camera.

Abstract: A mount for optical elements includes a frame and a holder for holding optical elements such as lenses and/or an image detecting element such as a CCD. The frame and holder are cylindrical. The diameter of an interior screw of the holder is smaller than the diameter of a mating exterior screw of the frame so that backlash between the frame and the holder at the screw connection is substantially eliminated as the frame is rotated relative to said holder to tighten the inner surface of the holder against the outer surface of the frame. In one embodiment, at least one notch extends in a longitudinal direction of the holder to assist in elastic deformation of the holder. In another embodiment, a tightening ring formed in a C-shape is mounted around the exterior surface the holder to constrain elastic deformation outwardly when the screw connection is tightened.

Abstract: A lens apparatus includes four lens groups and a plurality of barrels with grooves that guide and drive the lens frames of the four lens groups in order to achieve a high zoom ratio and retraction of the lens apparatus into a camera body when the lens apparatus is not in use. Two sets of three guide grooves in a fixed barrel and three cam grooves in a cam barrel are unequally spaced around the circumference of the barrels so as to provide more room for an additional groove in the cam barrel. Some of the lens frames are fully supported by pins in the grooves and some of the lens frames are partially supported by guide rods in the lens apparatus. A single guide rod helps support two lens frames in order to save space in the lens apparatus.

Abstract: A presentation system for a presenter to safely point out parts of an image projected from a projector onto a screen with laser light projected from a laser pointer held by the presenter is disclosed. The presentation system includes one or more infrared light receiving units on the laser pointer that selectively receive infrared signals from sending units that are mounted on the projector or on walls in order to control emission of laser light from the laser pointer. Arrangements of the sending and receiving units are designed to allow emission of the laser light from the pointer only when the laser pointer is pointed toward the projection screen. A control unit in the laser pointer may determine if the laser pointer is pointed correctly or a gravity operated shutter may further assist in preventing unsafe projection of laser light from the laser pointer.

Abstract: A retrofocus wide-angle lens includes a first lens group of negative refractive power, a diaphragm, and a second lens group of positive refractive power. The first lens group includes an object-side lens group, a middle lens group, and an image-side lens group. The object-side lens group includes a plurality of negative lens components and a positive meniscus lens component with its convex surface on the image side. The middle lens group satisfies a particular focal length condition and includes a negative lens component at the object side. The image-side lens group includes a negative lens element and a positive lens element. The first and second lens groups include lens elements of opposite refractive power that are made of anomalous dispersion glass so as to provide chromatic aberration correction and to compensate for variations in refractive index with temperature change that would otherwise cause the focal length to vary with temperature.