Abstract: A variable magnification optical system projects an image onto a screen with a sufficient magnification without requiring a large-sized mirror. The variable magnification optical system includes a first optical system through which a light beam modulated with an image signal corresponding to the image is passed; a second optical system disposed downstream of the first optical system in a direction of travel of the light beam along an optical axis; and a reflective optical element having a magnification power that is configured to reflect the light beam from the second optical system toward the screen. A magnification of the image projected on the screen is changed by moving the reflective optical element relative to the object plane, thus changing a distance between the screen and the reflective optical element, while an incident angle of the light beam on the screen is maintained substantially constant.

Abstract: Disclosed is an image reading device configured to read information of an object, including an imaging optical system configured to image an image of an object and an image-capturing device configured to image-capture at least a portion of the image imaged by the imaging optical system, wherein the imaging optical system includes a first optical system configured to image an intermediate image of the object and a second optical system configured to image the imaged image of the intermediate image.

Abstract: A disclosed reflective screen is configured to display an image projected from a projection device located within a short distance. The reflective screen comprises a first reflective surface configured to reflect, in a substantially same direction, projection light beams projected from a first position, and a second reflective surface configured to reflect, in the substantially same direction, projection light beams projected from a second position different from the first position.

Abstract: A projection optical system, in which a plurality of light flux emitted from one conjugate plane enters another conjugate plane and an image formed on the one conjugate plane is projected on the other conjugate plane, includes: a first optical system including at least one lens; and a second optical system which includes at least two reflecting surfaces with optical power, a normal line of the other conjugate plane from a center of an image projected on the other conjugate plane has no intersection with any space of the first optical system, or the second optical system, or a space between the first optical system and the second optical system, and when a plane defined by a vertical direction of the image projected on the other conjugate plane and an extending direction of the normal line is set as a YZ plane, from the first optical system to the other conjugate plane an optical path intersects only once on the YZ plane.

Abstract: A disclosed projection optical system for projecting and forming an enlarged image of an image displayed in a planar manner as an object includes: a lens system including, from an object side, at least a lens group providing telecentricity to an object space side, a lens group controlling divergence of angles of view, a diaphragm, a lens group converging the angles of view, and a lens group converging and subsequently enlarging the angles of view; and a catoptric system disposed on an image side relative to the lens system and including a mirror having negative power. Each lens group of the lens system and the mirror having negative power share an optical axis and the optical axis is shifted relative to a center of an object surface.

Abstract: A wide-angle lens is disclosed that includes a front lens group and a rear lens group that are arranged in order from an object side to an image side with an aperture being arranged between the front lens group and the rear lens group. The front lens group includes at least two lenses arranged toward the object side that have positive powers, and at least one lens arranged toward the image side that has a negative positive power. One of the lenses of the front lens group arranged second in order from the object side has a lens face that is arranged into an aspheric surface. The front lens group, the aperture, and the rear lens group make up an image forming system having an angle of view greater than 180 degrees.

Abstract: A disclosed projection optical system for projecting and forming an enlarged image of an image displayed in a planar manner as an object includes: a lens system including, from an object side, at least a lens group providing telecentricity to an object space side, a lens group controlling divergence of angles of view, a diaphragm, a lens group converging the angles of view, and a lens group converging and subsequently enlarging the angles of view; and a catoptric system disposed on an image side relative to the lens system and including a mirror having negative power. Each lens group of the lens system and the mirror having negative power share an optical axis and the optical axis is shifted relative to a center of an object surface.

Abstract: Disclosed is a projection optical system including a projection surface configured such that an image conjugate to an object is projected, plural optical elements having a refractive power, and a deflecting element having no refractive power configured to deflect an optical path of a light beam and to pass the light beam having a deflected optical path between the plural optical elements, wherein a normal line of the projection surface at a center of the projection surface does not pass through the plural optical elements or between the plural optical elements.

Abstract: A disclosed reflective screen is configured to display an image projected from a projection device located within a short distance. The reflective screen comprises a first reflective surface configured to reflect, in a substantially same direction, projection light beams projected from a first position, and a second reflective surface configured to reflect, in the substantially same direction, projection light beams projected from a second position different from the first position.

Abstract: A projection optical system including a first optical system configured to form a second image conjugate to a first image and a second optical system configured to include a reflective optical element which reflects light from the second image and to project a third image conjugate to the second image onto a projection surface is provided, wherein the first optical system has a Petzval sum with a sign opposite to a sign of a Petzval sum of the second optical system.

Abstract: A projection optical system including a first optical system configured to form a second image conjugate to a first image and a second optical system configured to include a reflective optical element which reflects light from the second image and to project a third image conjugate to the second image onto a projection surface is provided, wherein the first optical system includes a stop and at least one optical element with a positive refractive power and at least one optical element with a negative refractive power which are provided between the stop and the second image, and an optical element with a strongest positive refractive power in the at least one optical element with a positive refractive power is provided between the stop and an optical element with a strongest negative refractive power in the at least one optical element with a negative refractive power.

Abstract: A disclosed projection optical system for projecting and forming an enlarged image of an image displayed in a planar manner as an object includes: a lens system including, from an object side, at least a lens group providing telecentricity to an object space side, a lens group controlling divergence of angles of view, a diaphragm, a lens group converging the angles of view, and a lens group converging and subsequently enlarging the angles of view; and a catoptric system disposed on an image side relative to the lens system and including a mirror having negative power. Each lens group of the lens system and the mirror having negative power share an optical axis and the optical axis is shifted relative to a center of an object surface.