Abstract: This specification discloses a polarizing. element for dividing light into first and second polarized lights differing in polarized state from each other by a polarizing dividing surface, directing the first polarized light in a first direction, reflecting the second polarized light by a reflecting surface and directing it in the first direction, and varying the polarized state of at least one of the first and second polarized lights to thereby make the polarized states of the first and second polarized lights coincident with each other, characterized in that the polarizing dividing surface is disposed on one surface of a plane parallel plate and the reflecting surface is disposed on the other surface of the plane parallel plate, and the light enters obliquely from the one surface or the other surface. The specification also discloses a polarizing conversion unit provided with such polarizing element, and a projector provided with such polarizing conversion unit.

Abstract: An object is to provide an optical low pass filter that can achieve advantageous effects in spite of its simple structure, in reducing moire fringes and false color noise for a common subject that includes a two-dimensional pattern. An optical low pass filter according to the present invention includes a plane parallel plate composed of a biaxial crystal, wherein the plane parallel plate satisfies the condition 0°?|?|<20°, where ? is the angle formed by one of the optic axes of the biaxial crystal and the normal to the light incident surface.

Abstract: An optical imaging system suppresses the generation of red-toned ghosting in an image particularly when there is a background light or when a strong light source shines on the screen. The optical imaging system has a reflection-type infrared cut filter comprising a multi-layer film, color filters that selectively transmit light according to the wavelength, and an imaging element. Ghosting is suppressed to inconspicuous levels by adjusting the transmittance of the color filters and the infrared cut filter, and by setting the spectral characteristics of the color filters.

Abstract: An optical imaging system suppresses the generation of red-toned ghosting in an image particularly when there is a background light or when a strong light source shines on the screen. The optical imaging system has a reflection-type infrared cut filter comprising a multi-layer film, color filters that selectively transmit light according to the wavelength, and an imaging element. Ghosting is suppressed to inconspicuous levels by adjusting the transmittance of the color filters and the infrared cut filter, and by setting the spectral characteristics of the color filters.

Abstract: This specification discloses a polarizing element for dividing light into first and second polarized lights differing in polarized state from each other by a polarizing dividing surface, directing the first polarized light in a first direction, reflecting the second polarized light by a reflecting surface and directing it in the first direction, and varying the polarized state of at least one of the first and second polarized lights to thereby make the polarized states of the first and second polarized lights coincident with each other, characterized in that the polarizing dividing surface is disposed on one surface of a plane parallel plate and the reflecting,surface is disposed on the other surface of the plane parallel plate, and the light enters obliquely from the one surface or the other surface. The specification also discloses a polarizing conversion unit provided with such polarizing element, and a projector provided with such polarizing conversion unit.

Abstract: In a projection type display apparatus for illuminating a projection original image with light from a projection light source, and projecting light transmitted through the illuminated original image using a projection lens, light reflected by a projection surface is extracted from a position at an original image side of the projection lens or in the projection lens, and the extracted light is received by a focus detection unit.

Abstract: A retrofocus type lens having a plurality of lenses divided into three lens units, or, in the order from a screen, a first lens unit, a second lens unit and a third lens unit, wherein letting the focal length of the entire lens system be denoted by fT, and the distance from a lens surface on the side of an original image to the original image by SK,SK>0.7 fTis satisfied, and the second lens unit and the first lens unit or the third lens unit each is provided with at least one aspherical lens of which at least one of the lens surfaces is aspherical.

Abstract: An image stabilizing system includes a photographic lens device having a plurality of lens units, wherein for zooming at least one lens unit separation varies, a detecting circuit for detecting the jiggle of the system, and a drive device for driving at least one lens unit in a direction perpendicular to a photographic optical axis of the photographic lens device on the basis of an output of the detecting circuit to stabilize an image.

Abstract: A small-sized camera in which while the light emerging from a photographic lens having an optical axis parallel with a photosensitive plane is conducted by first and second mirrors to the photosensitive plane to form a photographic system, the first or second mirror is turned around a predetermined axis to conduct the light to an eyepiece lens to form a finder system. And, a structure of construction for efficiently removing the stray light of this camera is disclosed.

Abstract: This specification discloses a projection type display apparatus in which the lights of a plurality of display means forming images of different color component lights are reflected by or transmitted through a dichroic mirror to effect color synthesis and the synthesized lights are projected onto a screen by a projection lens. The astigmatism created by the lights being transmitted through the obliquely disposed dichroic mirror is suppressed to thereby obtain a good quality of image.

Abstract: An image stabilization optical system for use in the variable magnification optical system having a first lens group followed rearwardly by a zoom section comprising a plurality of lens groups is disclosed, wherein as at least one lens group in the zoom section is made to be a compensating lens group, the optical action of each lens group is properly specified so that if the tilting of the optical system is the same, the amount of compensation movement of the compensating lens group becomes always the same regardless of the image magnification varying position.

Abstract: A zoom lens includes, in succession from the greatly conjugate side to the little conjugate side, a first lens unit having negative refractive power, and a second lens unit having positive refractive power. Zooming from the wide angle side to the telephoto side is effected by at least the second lens unit being moved toward the greatly conjugate side. The zoom lens satisfies the following condition:bf.sub.w /f.sub.w >1.6,where f.sub.w is the focal length of the entire system at the wide angle end, and bf.sub.w is the distance from the last lens surface of the second lens unit to the little conjugate side.

Abstract: A focusing screen has a base plate with a planar surface. A plurality of unit regions are arrayed with a periodicity on the base plate planar surface. Each of the unit regions comprises (1) a first plurality of convex portions or concave portions having planar surfaces substantially parallel to the base plate planar surface and having a first height different from the base plate planar surface and having at least two different diameters, and (2) a second plurality of convex portions or concave portions having planar surfaces substantially parallel to the base plate planar surface and having a second height different from the base plate planar surface and having at least two different diameters.

Abstract: A projection display apparatus, which projects a magnified image onto a screen, comprises an image forming system, such as a display panel, a projector including a plurality of lenses for projecting the image onto the screen, and a decentering mechanism for decentering some lenses in the projector with respect to the optical axis. Even if the image is distorted by arrangement of the screen and the optical axis and so on, the distortion is compensated by decentering the lenses and producing a decentering distortion.

Abstract: A focusing screen suited to be used in the camera, having three plane portions of different heights in each of small areas, wherein the plane portion A, the plane portion B and the plane portion C are arranged in the order from the lowest height, and letting the height of the plane portion B measured from the plane portion A be denoted by d.sub.B, the height of the plane portion C from the plane portion A by d.sub.C, and the area ratios of the plane portions A, B and C to the entire area by S.sub.A, S.sub.B and S.sub.C (where S.sub.A +S.sub.B +S.sub.C =1) respectively, the following conditions are satisfied1.6<d.sub.C /d.sub.B <2.50.35<S.sub.B <0.5whereby the color tint is minimized for good optical performance.

Abstract: In an optical system comprising a plurality of lens units, one of which is used as a compensation lens unit capable of decentering to compensate for the image blur, an image magnification .beta.c of the compensation lens unit satisfies the following condition:-1.4<.beta.c<-0.

Abstract: A zoom lens comprising a plurality of lens units in which at least one of the air separations between the units is varied to effect zooming, whereby at least one of the plurality of lens units is included with at least one refractive index distribution type lens element on a common optical axis of the other elements.

Abstract: A zoom lens including at least two lens units of which the front one is of positive refractive power and the rear one is of negative refractive power, the units being axially movable to decrease their separation in zooming from the wide angle to the telephoto end. At least one of the lens units is provided with at least one refractive index distribution type lens arranged on a common optical axis of the other lenses in order to achieve a great advance in compactness.

Abstract: An optical system comprising, from front to rear, a first lens group of positive power, a second lens group of negative power and a third lens group of positive power, wherein deflection of an image is made by parallel decentering the second lens group.

Abstract: A refractive index distribution type meniscus-shaped single lens characterized in that it has a refractive index distribution in which the refractive index decreases along the optic axis thereof from a convex surface to a concave surface and the difference .DELTA.N in refractive index between the convex surface and the concave surface on the optic axis satisfies .DELTA.N.gtoreq.0.15.