Abstract: A projection optical system receives light from a display device surface and enlarges and projects a display image thereon onto a screen surface. The projection optical system includes one or more reflective surfaces having an optical power between the display device surface and the screen surface, moves at least one optical device having an optical power to adjust focus and satisfies the following conditional formula: ?0.02<{(?1??2)?2}/{(?1+?2)?1}<0.

Abstract: A variable-power optical system includes, in order from an object side thereof: a first lens group with a negative optical power; a second lens group with a positive optical power; a third lens group with a negative optical power; and a fourth lens group with a positive optical power. An interval between the first lens group and the second lens group decreases when a power of the variable-power optical system varies from a wide-angle end to a telephoto end. The second lens group includes at least one aspheric surface. The variable-power optical system satisfies the predetermined conditional expressions.

Abstract: A variable-power optical system includes, in order from an object side thereof: a first lens group with a negative optical power; a second lens group with a positive optical power; and a third lens group with a negative optical power, where an interval between the first lens group and the second lens group decreases when a power of the variable-power optical system varies from a wide-angle end to a telephoto end. The first lens group comprises a negative lens and a positive lens. The second lens group consists of a positive lens and a negative lens, and includes at least one aspheric surface. The variable-power optical system satisfies the predetermined conditional expressions.

Abstract: Provided is a microminiaturized zoom optical system capable of sufficiently correcting aberration. The zoom optical system (100) includes a first lens group (101) having a negative optical power, a second lens group (102) having a positive optical power, and a third lens group (103) having a positive or negative optical power in this order from the object side. The zoom optical system is configured in such a manner that the interval between the first lens group (101) and the second lens group (102) is decreased in zooming from the wide angle end to the telephoto end. A positive lens element in the third lens group (103) or in a lens group closer to the image side than the third lens group (103) satisfies the following conditional expression: vp<40 where vp is the minimum value of the Abbe number of the positive lens element.

Abstract: A variable-power optical system includes, in order from an object side thereof: a first lens group with a negative optical power; a second lens group with a positive optical power, moving when the power of the variable-power optical system varies; and a third lens group with a positive or negative optical power. The first lens group includes two or more lenses including one positive lens and one negative lens which include at least two or more lenses made of a plastic material. The variable-power optical system satisfies the predetermined conditional expressions relating to is a focal length of the first lens, a focal length of the second lens, a composite focal length of the total optical system, and an image-forming magnification of the second lens group at a telephoto end.

Abstract: An ultra wide angle imaging optical system includes, in order from an object side, a first lens group, an aperture stop, and a second lens group. The first lens group includes, in order from the position closest to the object side, a negative meniscus lens element convex to the object side, a negative lens element, and a negative lens element. The second lens group includes a plurality of positive lens elements. The first lens group and the second lens group each includes at least one anamorphic surface having different optical powers with respect to a first section extending in a first direction on a flat plane substantially orthogonal to an optical axis, and with respect to a second section extending in a second direction substantially orthogonal to the first direction. The first lens group includes the lens element satisfying the following conditional formula (1): ?0.6<(Ph?Pv)*(fh+fv)<?0.

Abstract: A projection optical system that receives light from a display element to project an image displayed by the display element onto a screen with enlargement at a varying magnification achieved by varying the projection distance to the screen has: a refractive optical system composed of one or more refractive lenses and having a positive optical power; and a concave-surfaced mirror disposed to the screen side of the refractive optical system and having a plane-symmetric reflective surface. The projection optical system includes at least one optical element designed to be movable for focusing. The projection optical system forms an intermediate image between the refractive optical system and the concave-surfaced mirror. Moreover, a prescribed conditional formula is fulfilled.

Abstract: A super-wide-angle optical system for forming an optical image of an object on an image pickup surface of an image sensing device that converts the optical image into an electrical signal is provided with, in order from the object side, a first negative lens, a second negative lens and a positive lens. The first negative lens has a meniscus shape convex to the object side. The second negative lens is positioned next to the first negative lens. The positive lens has an aspherical surface. At least one of four lens surfaces of the first and second lenses is an aspherical surface. A prescribed condition is fulfilled.

Abstract: A wide angle of view optical system, suitable for monitor cameras such as an in-vehicle camera and a security camera, having a reduced optical entire length and aberration correction for forming an optical image on light-receiving surfaces of an imaging element having a first lens having a negative optical power and a group of lenses each having a positive optical power, which are serially disposed from an object side. The first lens comprises at least one aspherical surface, and has a concave surface centered around an optical axis in vicinity of the optical axis on an image-side surface thereof. Further, an optical entire length T in millimeters (mm) of the entire system, a half angle of view ?, and a focal distance ftot of the entire system, also in millimeters, satisfy the conditional expressions.

Abstract: A projector has a projection optical system unit, which has a positively powered optical system and a curved-mirror optical system. In the projector, a first curved mirror and a second curved mirror of the curved-mirror optical system are so arranged that the optical path that the base ray travels to reach the first curved mirror crosses the optical path that the base ray travels to leave the second curved mirror. Moreover, the second curved mirror has a negative optical power.

Abstract: A projector is loaded with a projection optical system unit having a refractive optical system, a curved mirror optical system, and a light travel change mirror optical system. Then, the projector has a first curved mirror and a second curved mirror of the curved mirror optical system arranged so that an optical path of a base ray reaching the first curved mirror and an optical path of a base ray leaving the second curved mirror do not intersect with each other, and also has the first curved mirror located between the second curved mirror and a screen surface. Furthermore, an angle of incidence of the base ray on the screen surface is within a predetermined range.

Abstract: An ultra wide angle imaging optical system includes, in order from an object side, a first lens group, an aperture stop, and a second lens group. The first lens group includes, in order from the position closest to the object side, a negative meniscus lens element convex to the object side, a negative lens element, and a negative lens element. The second lens group includes a plurality of positive lens elements. The first lens group and the second lens group each includes at least one anamorphic surface having different optical powers with respect to a first section extending in a first direction on a flat plane substantially orthogonal to an optical axis, and with respect to a second section extending in a second direction substantially orthogonal to the first direction. The first lens group includes the lens element satisfying the following conditional formula (1): ?0.6<(Ph?Pv)*(fh+fv)<?0.

Abstract: An oblique projection optical system for leading rays of light from a display surface on which an image is displayed to a projection surface in such a way that the ray of light from the center of the display surface is obliquely incident on the projection surface in order to project a magnified image of the image displayed on the display surface onto the projection surface includes a plurality of reflecting surfaces having a power. At least two of the reflecting surfaces have a free-form curved surface, and, of all the reflecting surfaces, the one closest to the projection surface has a negative power and at least one of the other has a positive power. Alternatively, in a rear projection optical system having a projection optical system for projecting an image displayed on a panel display surface onto a screen surface, the projection optical system includes at least four curved-surface reflecting mirrors.

Abstract: An image-taking optical system for forming an optical image of an object on the light-receiving surface of an image sensor includes a plurality of optical blocks. The optical blocks each have a prism unit provided with a curved surface and an optical unit composed of a member different from a member composing the prism unit. The prism unit uses the curved surface as a total reflection surface and also as a transmission surface. The optical unit has near the curved surface a curved surface identically or substantially identically shaped therewith.

Abstract: In a zoom optical system for forming an optical image of an object onto a light receiving plane of an image sensor for converting the optical image into an electrical signal, and performing zooming by varying distances between a first lens group and a second lens group, and between the second lens group and a third lens group in an optical axis direction, the zoom optical system includes: the first lens group having a negative optical power; the second lens group having a positive optical power; and the third lens group having a positive optical power, wherein the first lens group is composed of two or more lens elements including at least one positive lens element and at least one negative lens element, the second lens group is composed of two or more lens elements including at least one positive lens element and at least one negative lens element, and all the lens elements in the first lens group are made of a plastic material.

Abstract: An oblique projection optical system for leading rays of light from a display surface on which an image is displayed to a projection surface in such a way that the ray of light from the center of the display surface is obliquely incident on the projection surface in order to project a magnified image of the image displayed on the display surface onto the projection surface includes a plurality of reflecting surfaces having a power. At least two of the reflecting surfaces have a free-form curved surface, and, of all the reflecting surfaces, the one closest to the projection surface has a negative power and at least one of the other has a positive power. Alternatively, in a rear projection optical system having a projection optical system for projecting an image displayed on a panel display surface onto a screen surface, the projection optical system includes at least four curved-surface reflecting mirrors.

Abstract: An optical system having a wide angle of view for forming an optical image of a photographic subject on light-receiving surfaces of an imaging element that converts the optical image into an electrical signal comprises a first lens having a negative optical power and a group of lenses each having a positive optical power, which are serially disposed from an object side. The first lens comprises at least one aspherical surface, and has a concave surface centered around an optical axis in vicinity of the optical axis on an image-side surface thereof. Further, an optical entire length T (mm) of the entire system, half angle of view ?, and focal distance ftot (mm) of the entire system satisfy the following conditional expressions. 10 mm<T×sin ?<30 mm 7<T/ftot<20 Thereby, the wide-angle optical system achieving a wide angle of view, reducing the optical entire length and capable of favorably correcting an aberration can be obtained.

Abstract: An image-taking optical system for forming an optical image of an object on the light-receiving surface of an image sensor includes a plurality of optical blocks. The optical blocks each have a prism unit provided with a curved surface and an optical unit composed of a member different from a member composing the prism unit. The prism unit uses the curved surface as a total reflection surface and also as a transmission surface. The optical unit has near the curved surface a curved surface identically or substantially identically shaped therewith.

Abstract: An oblique projection optical system for leading rays of light from a display surface on which an image is displayed to a projection surface in such a way that the ray of light from the center of the display surface is obliquely incident on the projection surface in order to project a magnified image of the image displayed on the display surface onto the projection surface includes a plurality of reflecting surfaces having a power. At least two of the reflecting surfaces have a free-form curved surface, and, of all the reflecting surfaces, the one closest to the projection surface has a negative power and at least one of the other has a positive power. Alternatively, in a rear projection optical system having a projection optical system for projecting an image displayed on a panel display surface onto a screen surface, the projection optical system includes at least four curved-surface reflecting mirrors.

Abstract: An image display apparatus forms illumination light from a light source into image light by using a reflective display device, and directs the image light through an eyepiece optical system to an eye to present a virtual image of the image carried by the image light. To realize an image display apparatus of this type that is compact, affords a sufficiently long eye relief, and offers wide-field, high-quality images, a combiner for making the optical path of the illumination light from the light source overlap with that of the image light is disposed inside the eyepiece optical system, a positive lens is provided in the rear potion of the eyepiece optical system between the display device and the combiner, a concave reflective surface is provided in the front portion of the eyepiece optical system between the combiner and the observation point, and the eyepiece optical system is designed to be overtelecentric as a whole.