Abstract: An optical system has an aperture stop, and an optical unit placed on the image side of the aperture stop. The optical unit consists of the following components in the order named from the object side: a first optical component with a reflective curved surface, for forming an intermediate image of an object, a second optical component with a reflective curved surface, for forming an image of the aperture stop with light from the intermediate image of the object, and a third optical component with a reflective curved surface, for forming a secondary image of the object with light from the image of the aperture stop. When fB1(&thgr;), fB2(&thgr;), and fB3(&thgr;) are focal lengths of the first optical component, the second optical component, and the third optical component, respectively, at an azimuth &thgr;, the focal lengths satisfy the following conditions in the azimuth range of 0<&thgr;<2&pgr;: fB1(&thgr;)>0, fB2(&thgr;)<0, fB3(&thgr;)>0.

Abstract: It is an object of this invention to provide a high-quality, high-precision, large-screen display apparatus which can obtain a sufficient light beam reception angle with respect to an image display unit, improve imaging performance, and obtain a thin structure. There is provided a display apparatus for obliquely projecting light from an image display unit onto a projection optical system, wherein the projection optical system includes a plurality of aspherical curved mirrors and projects an image without distortion (1.2% or less).

Abstract: With a view to provide a projection optical system using an oblique projection method which contrives the downsizing of an apparatus and yet secures a ratio of quantity of marginal light and which is high in the enlarging rate, and a projection type displaying apparatus using the same, a projection optical system for guiding a beam from an image display panel onto a screen surface inclined relative to a reference axis, and forming image information on the screen surface has a reflecting optical system which has a plurality of rotation-asymmetrical reflecting surfaces having curvatures, and in which the beam from the image display panel is reflected by the plurality of rotation-asymmetrical reflecting surfaces and is guided onto the screen surface, and a stop is provided between the plurality of rotation-asymmetrical reflecting surfaces of the reflecting optical system or between the reflecting optical system and the image display panel, and the stop is set so as to be imaged at a negative magnification by an

Abstract: An optical element has a plurality of reflective surfaces formed integrally so as to reflect light incident thereto successively and thereafter guide it out of the optical element. The optical element is provided with a member for preventing light of a predetermined wavelength band from emerging from the optical element.

Abstract: The optical system provided with a first optical part disposed most adjacent to the object side, the optical part having three or more optical surfaces, of which at least one is a reflecting surface, and an aperture stop disposed more adjacent to the image side than the first optical part, wherein when the spacing from the first optical surface to the third optical surface as counted from the object side of the first optical part is defined as D and the spacing from the first optical surface to the entrance pupil at an azimuth &xgr; degrees is defined as X(&xgr;), the following condition is satisfied: (X(0)+X(90))/2<D. The specification also discloses an optical apparatus provided with such optical system.