Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein in zooming from a wide-angle limit to a telephoto limit, the lens units move respectively along an optical axis in such a manner that an interval between the first lens unit and the second lens unit decreases while an interval between the second lens unit and the third lens unit changes so that variable magnification is achieved, the first lens unit comprises one object side negative lens element and one image side positive lens element with a convex surface facing the object side, which have an aspheric surface, and the conditions: n12>1.88 and ?12<26 (n12 and ?12 are refractive index and Abbe number, respectively, of the image side positive lens element of the first lens unit) are satisfied.

Abstract: There is provided a compact, strong and high-performance catoptric optical system. This catoptric optical system has plural optical curved reflective surfaces. A gap between a pair of reflective surfaces, through which light incident upon said catoptric projection optical system passes, is the same gap between a pair of reflective surfaces, through which light exited from the catoptric projection optical system passes.

Abstract: A projection optical system having a plurality of reflecting surfaces is disclosed in which a sufficiently large angle is provided between an incident side reference axis and an emerging side reference axis while tilt angles of the respective reflecting surfaces can remain small. The projection optical system projects luminous flux from an image forming element which forms an original image onto a projection surface. The incident side reference axis and the emerging side reference axis of the projection optical system are oblique to each other. The projection optical system has a plurality of reflecting surfaces each having a curvature. The reflecting surfaces are arranged such that the reference axis has at least one intersection in the projection optical system.

Abstract: A projection optical system which can project a bright image with less distortion and a small projection distance without causing aberration or an increase in size of reflective surfaces is disclosed. The projection optical system projects luminous flux from an original image onto a projection surface which is oblique to a central principal ray which is a principal ray of luminous flux traveling from the center of the original image to the center of a projected image. The projection optical system comprises a refractive optical system which includes a plurality of refractive optical elements through which the luminous flux from the original image passes through, and a reflective optical system which includes a plurality of reflective surfaces each having an optical power and guides the luminous flux emerging from the refractive optical system to the projection surface.

Abstract: An image display apparatus is provided, which includes a first image display element corresponding to a first color light, a second display element corresponding to a second color light different from the first color light, and a projection optical system having at least one reflective surface and projecting image lights from the first and second display elements onto a projection plane.

Abstract: A projection optical system which has a short projection distance and a compact structure, and allows oblique projection. The projection optical system projects luminous flux from an image forming element for forming an original image onto a projection surface which is oblique to a central principal ray which is a principal ray of luminous flux traveling from the center of the original image to the center of a finally formed image. The system includes a plurality of reflecting surfaces each having a curvature. In addition, the projection optical system satisfies a predetermined expression (1).

Abstract: There is provided a compact, strong and high-performance catoptric optical system. This catoptric optical system has plural optical curved reflective surfaces. A gap between a pair of reflective surfaces, through which light incident upon said catoptric projection optical system passes, is the same gap between a pair of reflective surfaces, through which light exited from the catoptric projection optical system passes.

Abstract: A projection optical system having a plurality of reflecting surfaces is disclosed in which a sufficiently large angle is provided between an incident side reference axis and an emerging side reference axis while tilt angles of the respective reflecting surfaces can remain small. The projection optical system projects luminous flux from an image forming element which forms an original image onto a projection surface. The incident side reference axis and the emerging side reference axis of the projection optical system are oblique to each other. The projection optical system has a plurality of reflecting surfaces each having a curvature. The reflecting surfaces are arranged such that the reference axis has at least one intersection in the projection optical system.

Abstract: A projection optical system which has a short projection distance and a compact structure, and allows oblique projection. The projection optical system projects luminous flux from an image forming element for forming an original image onto a projection surface which is oblique to a central principal ray which is a principal ray of luminous flux traveling from the center of the original image to the center of a finally formed image. The system includes a plurality of reflecting surfaces each having a curvature. In addition, the projection optical system satisfies a predetermined expression (1).

Abstract: A projection optical system which can project a bright image with less distortion and a small projection distance without causing aberration or an increase in size of reflective surfaces is disclosed. The projection optical system projects luminous flux from an original image onto a projection surface which is oblique to a central principal ray which is a principal ray of luminous flux traveling from the center of the original image to the center of a projected image. The projection optical system comprises a refractive optical system which includes a plurality of refractive optical elements through which the luminous flux from the original image passes through, and a reflective optical system which includes a plurality of reflective surfaces each having an optical power and guides the luminous flux emerging from the refractive optical system to the projection surface.

Abstract: In a projection apparatus, a light beam emitted by a light source is guided to a modulation element for forming an image. The light beam emerged from the modulation element is projected onto a screen by a projection lens. An image of the light source is formed as a first light source image by a first optical system. The light beam from the modulation element illuminated with light emanating from the first light source image is imaged by a second optical system as a second light source image at a potion in the vicinity of an aperture of a stop of the projection lens. A peripheral portion of the first light source image is intercepted by another stop located at a potion conjugate with the stop of the projection lens.

Abstract: In a projection apparatus, a light beam emitted by a light source is guided to a modulation element for forming an image. The light beam emerged from the modulation element is projected onto a screen by a projection lens. An image of the light source is formed as a first light source image by a first optical system. The light beam from the modulation element illuminated with light emanating from the first light source image is imaged by a second optical system as a second light source image at a potion in the vicinity of an aperture of a stop of the projection lens. A peripheral portion of the first light source image is intercepted by another stop located at a potion conjugate with the stop of the projection lens.