Abstract: A projection optical system that projects, while enlarging, an image displayed on an image display surface includes in order from an enlargement side: a first negative refractive power lens group; a second negative refractive power lens group; at least one positive or negative refractive power lens group; a stop; and a first positive refractive power lens group. The projection optical system causes magnification variation by varying distances between lens groups. The at least one positive or negative refractive power lens groups disposed between the second negative refractive power lens group and the stop is movable during the magnification variation. The first positive refractive power lens group is an only lens group that is positioned closer to a reduction side than the stop and is also movable during the magnification variation.

Abstract: A projection optical system that projects, while enlarging, an image displayed on an image display surface includes in order from an enlargement side: a first negative refractive power lens group; a second negative refractive power lens group; at least one positive or negative refractive power lens group; a stop; and a first positive refractive power lens group. The projection optical system causes magnification variation by varying distances between lens groups. The at least one positive or negative refractive power lens groups disposed between the second negative refractive power lens group and the stop is movable during the magnification variation. The first positive refractive power lens group is an only lens group that is positioned closer to a reduction side than the stop and is also movable during the magnification variation.

Abstract: A variable magnification projection optical system includes, in order from a magnification conjugate side to a reduction conjugate side, a first lens group, a second lens group, a third lens group, a fourth lens group, a fifth lens group, a sixth lens group, and an optical stop which is arranged at any position from a front of a lens arranged closest to the magnification conjugate side in the fourth lens group to a front of a lens arranged closest to the magnification conjugate side in the fifth lens group, wherein the fourth lens group is configured to include, in order from the magnification conjugate side, two or more negative lenses and a positive lens, and wherein the following condition expressions (1), (2) and (3) are satisfied: |Et/ft|?10??(1) |EW/fW|?15??(2) 0.87?23?T/23WT?1.15??(3).

Abstract: A variable magnification projection optical system includes, in order from a magnification conjugate side to a reduction conjugate side, a first lens group, a second lens group, a third lens group, a fourth lens group, a fifth lens group, a sixth lens group, and an optical stop which is arranged at any position from a front of a lens arranged closest to the magnification conjugate side in the fourth lens group to a front of a lens arranged closest to the magnification conjugate side in the fifth lens group, wherein the fourth lens group is configured to include, in order from the magnification conjugate side, two or more negative lenses and a positive lens, and wherein the following condition expressions (1), (2) and (3) are satisfied. |ET/fT|?10??(1) |EW/fW|?15??(2) 0.87??23T/??23W?1.

Abstract: A variable-focal-length lens system for projection which achieves focusing by movement of the entire system has a second to a fourth lens group as focal-length-varying lens groups and a first lens group as a distance-compensation lens group. The second to fourth lens groups individually move in the optical axis direction to vary the group-to-group distances so as to vary the focal length of the entire system. During focusing, the first lens group moves in the optical axis direction such that, as the projection distance varies from a remote distance to a close distance, curvature of field varies to the under side.

Abstract: A variable-focal-length lens system for projection which achieves focusing by movement of the entire system has a second to a fourth lens group as focal-length-varying lens groups and a first lens group as a distance-compensation lens group. The second to fourth lens groups individually move in the optical axis direction to vary the group-to-group distances so as to vary the focal length of the entire system. During focusing, the first lens group moves in the optical axis direction such that, as the projection distance varies from a remote distance to a close distance, curvature of field varies to the under side.

Abstract: Provided is a magnified-projection optical system, which can retain a considerably long back focus although a focal length is short and which has a small chromatic aberration. The optical system comprises a projecting optical system, a relay optical system and a display element, which are sequentially arrayed from a screen side along the optical axis. The projecting optical system enlarges and projects the image, which has been linearly focused by the relay optical system, on the screen, and includes a negative group and a positive group arrayed sequentially from the screen side and having a negative optical power and a positive optical power, respectively. The optical system satisfies the following conditional relations of |Fb/F|>10 and 0.5<|F/Fp|<2.

Abstract: Provided is a magnified-projection optical system, which can retain a considerably long back focus although a focal length is short and which has a small chromatic aberration. The optical system comprises a projecting optical system, a relay optical system and a display element, which are sequentially arrayed from a screen side along the optical axis. The projecting optical system enlarges and projects the image, which has been linearly focused by the relay optical system, on the screen, and includes a negative group and a positive group arrayed sequentially from the screen side and having a negative optical power and a positive optical power, respectively. The optical system satisfies the following conditional relations of |Fb/F|>10 and 0.5<|F/Fp|<2.

Abstract: An optical system includes a first prism having a first surface and a second surface forming an acute angle therebetween, and a second prism having a third surface. The first prism and the second prism form an air gap between the second surface and the third surface. The air gap formed by the second surface and the third surface has a cross section perpendicular to the first surface and the second surface which is a wedge shape which is wide at a part thereof near the first surface and narrower at a part thereof more distant from the first surface.

Abstract: A projection system that is capable of providing a high-performance projection system and producing a high contrast projection image by using an optical modulation element, which can be positioned a predetermined distance away from an illumination optical system and a projection optical system. The optical modulation element is capable of modulating light received from the illumination optical system and projecting the modulated light to a projection optical system in the direction of a projection surface.

Abstract: An illumination optical system has a light source, an integrator for making the intensity distribution of the light from the light source even, and a relay optical system for imaging the light from the integrator on a plane conjugate with the exit surface of the integrator. The relay optical system includes a rear lens unit of which the refractive power is asymmetrical in one direction so that the plane on which the light is imaged is inclined relative to the optical axis of the relay optical system. This makes it possible to direct light to an inclined surface with an even intensity distribution and with minimum loss of the illumination light.

Abstract: An illumination optical system has a light source, an integrator for making the intensity distribution of the light from the light source even, and a relay optical system for imaging the light from the integrator on a plane conjugate with the exit surface of the integrator. The relay optical system includes a rear lens unit of which the refractive power is asymmetrical in one direction so that the plane on which the light is imaged is inclined relative to the optical axis of the relay optical system. This makes it possible to direct light to an inclined surface with an even intensity distribution and with minimum loss of the illumination light.

Abstract: In a projector optical system provided with a DMD having minute mirror devices regularly arranged on one plane so as to correspond to the pixels of an image and selectively reflecting illuminating light in the direction of the optical axis of a projection optical system or in a direction different from the direction of the optical axis by bringing the mirror devices into an ON state or an OFF state according to the input video signals, and a prism disposed between the DMD and the projection optical system and having a first surface reflecting the illuminating light to be directed to the DMD and transmitting the light reflected at the DMD, the prism has a second surface transmitting, of the light transmitted by the first surface, light reflected at the mirror devices in the ON state and reflecting light reflected at the mirror devices in the OFF state.

Abstract: A projection optical apparatus has a light source for emitting light, an illumination optical system for emitting as illumination light the light radiated from the light source, a Digital Micromirror Device™, having a plurality of micromirrors, for separating the illumination light into signal light and unnecessary light by varying, in accordance with a signal, the angles at which the individual micromirrors reflect the illumination light shone thereon, a total internal reflection prism composed of a first prism for totally reflecting and thereby directing the illumination light exiting from the illumination optical system to the Digital Micromirror Device™ and a second prism for transmitting the signal light reflected from the Digital Micromirror Device™, and a projection optical system for projecting the signal light transmitted through the second prism onto a projection surface.

Abstract: A projection system that is capable of providing a high-performance projection system and producing a high contrast projection image by using an optical modulation element, which can be positioned a predetermined distance away from an illumination optical system and a projection optical system. The optical modulation element is capable of modulating light received from the illumination optical system and projecting the modulated light to a projection optical system in the direction of a projection surface.

Abstract: In an optical system includes a first prism having a first surface and a second surface forming mutually acute angles, and a second prism having a third surface. The first prism and the second prism forms an air gap between the second surface and the third surface. The air gap formed by the second surface and the third surface is a cross section perpendicular to the first surface and the second surface having a wedge shape which widens at a part near the first surface and narrows at a part distant from the first surface.

Abstract: A projection optical system has, from the enlargement side to the reduction side, a first, a second, and a third lens unit, and an aperture diaphragm. The negatively-powered first lens unit includes only a negative lens element and has at least one aspherical surface. The positively-powered second lens unit includes at least one positive lens element. The positively-powered third lens unit includes a lens element. The aperture diaphragm is disposed at the front focal point of the third lens unit. The lens element of the third lens unit is made of a material of which anomalous partial dispersibility and Abbe number are defined.

Abstract: A variable magnification optical system for projecting images from a small-sized, high-resolution display device consists of, from the projection side, a first lens unit having a positive optical power, a second lens unit having a negative optical power, a third lens unit having a negative optical power, and a fourth lens unit having a positive optical power and kept in a fixed position during magnification adjustment. The optical system achieves magnification adjustment by moving at least the second and third lens units along the optical axis, and has at least one negative lens element in the second lens unit, at least one negative lens element in the third lens unit, and at least one positive lens element in the fourth lens unit made of lens materials having predetermined anomalous dispersions and predetermined Abbe numbers.

Abstract: A variable magnification optical system includes, from the projection side, a negative first lens unit, a positive second lens unit and a positive third lens unit. The magnification is varied by moving the first and second lens units along the optical axis. A lens element in the first lens unit and a lens element in the third lens unit are aspherical lens elements of which aspherical deviation is defined. A positive lens element in the third lens unit is made of a material of which anomalous partial dispersibility and Abbe number are defined.

Abstract: An illumination optical system has a light source unit, a first array having a plurality of two-dimensionally arranged cells which deflect a incident light from the light source unit and a second array having a plurality of cells two-dimensionally arranged in a vicinity of a focal plane of the first array, wherein at least one of the first array and the second array is formed as a reflection array.