Abstract: An optical system includes a first lens having negative refractive power, a stop, a second lens having positive refractive power, an aperture stop, a third lens having positive refractive power, a fourth lens having negative refractive power, a fifth lens having positive refractive power, and a sixth lens having positive refractive power, with the lenses sequentially arranged from the magnifying side toward the demagnifying side. The third and fourth lenses are bonded into a doublet, which has negative refractive power. One of the fifth and sixth lenses is made of plastic and has aspherical surfaces on opposite sides, and the other is made of glass. The portion on the demagnifying side of the sixth lens is a telecentric portion. Conditional Expression (1) below is satisfied, SD12/SD2<0.9??(1) where SD12 represents the effective radius of the stop, and SD2 represents the effective radius of the second lens.

Abstract: A projection system includes a first optical system and a second optical system disposed on an enlargement side of the first optical system. The first optical system includes a first lens group having positive power, a second lens group disposed on the enlargement side of the first lens group and having negative power, and an optical path deflector disposed between the first lens group and the second lens group. The second optical system includes a reflection member having a concave reflection surface. The second lens group includes three aspherical lenses. Conditional Expression (1) below is satisfied, 0.25<|F|×FNO/Ymax<0.5??(1) where F represents the focal length of the entirety of the projection system, FNO represents the F number of the projection system, and Ymax represents a maximum image height in a reduction-side conjugate plane.

Abstract: A projection system has a zooming function and is configured that light rays from a telecentric system enter. The projection system is formed of seven lens groups. The first and seventh lens groups are fixed when the projection magnification is changed, and the second, third, fourth, fifth, and the sixth lens groups move along the optical axis when the projection magnification is changed. The second lens group is formed of one positive lens. The third lens group is formed of one positive lens. The fourth lens group is formed of one or two positive lenses and one negative lens having the center of curvature located at the magnifying side. The fifth lens group is formed of one negative lens having a magnifying-side aspheric surface and a demagnifying-side aspheric surface with each of the surfaces having the center of curvature located at the demagnifying side.

Abstract: A projection system includes a first optical system and a second optical system. The second optical system includes a first lens group disposed on an enlargement side of an intersection position where a chief ray of an off-axis beam having a maximum angle of view intersects with an optical axis of the projection system in the second optical system, a second lens group disposed on the reduction side of the intersection position and having negative power, and a third lens group disposed on the reduction side of the second lens group and having positive power. The second lens group includes a first lens having positive power, a second lens disposed on the reduction side of the first lens and having positive power, and a third lens disposed on the reduction side of the second lens and having negative power. The third lens group includes two lenses each having positive power.

Abstract: A projection system including seven lens groups sequentially arranged from an enlargement side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, a fifth lens group having positive refractive power, a sixth lens group having positive refractive power, and a seventh lens group having positive refractive power, wherein ?dR that is a dispersion value of a lens that forms the seventh lens group out of the seven lens groups and is closest to a reduction side and ?dF that is a dispersion value of a lens that forms the first lens group out of the seven lens groups and is closest to the enlargement side satisfy a following conditional expression: 5<?dR??dF<30.

Abstract: A projector projects image light generated by an image generation unit, as an enlarged image via a projection system. The incident position of the image light on the projection system is moved by a lens shift mechanism. The projection system forms an intermediate image in the course of the optical path. A light-shielding mask is provided at an image forming position of the intermediate image. A light-shielding area by the light-shielding mask includes an area that does not overlap the intermediate image within a range of an effective image forming area at the image forming position of the intermediate image. For example, the light-shielding area is an area on the side opposite to the side to which the intermediate image is shifted, of the effective image forming area.

Abstract: In a projector, a first fixation section and a second fixation section are formed at two places located at a distance in an optical axis direction in a lens barrel of a projection optical system. A holding member has contact with the first fixation section from an optical axis direction-rear side, and is fixed, an optical component housing of an illumination light guide optical system has contact with the holding member from the optical axis direction-rear side, and is fixed. A light modulating/combining optical system for generating image light has contact with the second fixation section from the optical axis direction-rear side and is fixed. In other words, the light modulating/combining optical system is directly fixed to the lens barrel without the intervention of the holding member for fixing the illumination light guide optical system to the lens barrel.

Abstract: A projection optical device includes a first lens group with a plurality of lenses arranged on a first optical axis, and which light emitted from a reduction side conjugate plane enters, a first reflecting element configured to reflect the light emitted from the first lens group to fold an optical path, a second lens group with a plurality of lenses arranged on a second optical axis, and which the light emitted from the first reflecting element enters, a second reflecting element configured to reflect the light emitted from the second lens group to fold an optical path, and a third lens group with a plurality of lenses arranged on a third optical axis, and which transmits the light emitted from the second reflecting element to emit the light toward an enlargement side conjugate plane, wherein defining an angle formed between the first and second optical axis as ?[°], ??90°.

Abstract: A projection system has a zooming function and is configured that light rays from a telecentric system enter. The projection system is formed of seven lens groups. The first and seventh lens groups are fixed when the projection magnification is changed, and the second, third, fourth, fifth, and the sixth lens groups move along the optical axis when the projection magnification is changed. The second lens group is formed of one positive lens. The third lens group is formed of one positive lens. The fourth lens group is formed of one or two positive lenses and one negative lens having the center of curvature located at the magnifying side. The fifth lens group is formed of one negative lens having a magnifying-side aspheric surface and a demagnifying-side aspheric surface with each of the surfaces having the center of curvature located at the demagnifying side.

Abstract: A projection system including seven lens groups sequentially arranged from an enlargement side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, a fifth lens group having positive refractive power, a sixth lens group having positive refractive power, and a seventh lens group having positive refractive power, wherein ?dR that is a dispersion value of a lens that forms the seventh lens group out of the seven lens groups and is closest to a reduction side and ?dF that is a dispersion value of a lens that forms the first lens group out of the seven lens groups and is closest to the enlargement side satisfy a following conditional expression: 5<?dR??dF<30.

Abstract: A projection system includes a first lens group that does not move when the projection magnification is changed with the aid of the zoom function, and the first lens group includes a correction lens group that is moved in the direction of the optical axis to correct worsened astigmatism. The projection system satisfies the following conditional expressions (1) and (2): |?BF20|<P×FNO×?2??(1) 1.5<|f1/f|??(2) where P represents the pixel pitch in an image displayed by liquid crystal panels, FNO represents the F number of the entire lens system, ?BF represents the amount of movement of the back focus position in a case where the correction lens group is moved by the amount of movement for correction of the aberration that changes when the temperature changes by 20° C., f represents the focal length of the entire lens system, and f1 represents the focal length of the correction lens group.

Abstract: A projection optical system includes a first lens unit and a second lens unit interposing an intermediate image therebetween. The first lens unit includes two aspherical lenses (a first lens unit first lens and a first lens unit ninth lens), and a first lens unit cemented lens. The projection optical system satisfies the following Conditional Expressions (1) and (2) when the number of lens elements of the first lens unit and the number of lens elements of the second lens unit are set to be Num1 and Num2, respectively. In addition, refractive indexes and Abbe numbers of three lenses constituting the first lens unit cemented lens satisfy a predetermined conditional expression. Num2?7??(1) 1.5?Num1/Num2?2.

Abstract: A projection optical system includes a first lens unit adapted to make a enlargement-side imaging surface and an intermediate image conjugate with each other, a second lens unit adapted to make the intermediate image and a reduction-side imaging surface conjugate with each other. The first lens unit has positive power, and the second lens unit has negative power. Defining a focal distance of the first lens unit as fU1, a focal distance of the second lens unit as fU2, a total lens length of the first lens unit as LLU1, and a total lens length of the second lens unit as LLU2, the following expression (1) and expression (2) are satisfied: ?0.3<fU1/fU2<?0.005??(1) 0.5<LLU1/LLU2<0.9??(2).

Abstract: A projection lens includes a plurality of lens groups each formed of at least one lens, and a lens barrel adapted to support each of the lens groups from an outer circumferential side. The lens barrel includes a first temporarily holding mechanism allowing the first lens group located at an end on a enlargement side to be displaced in a direction perpendicular to the optical axis, a first adhesive applied to the first temporarily holding mechanism to fix the first lens group so as to be unable to be displaced, a second temporarily holding mechanism allowing the seventh lens group located at an end on a reduction side to be displaced in a direction perpendicular to the optical axis, and a second adhesive applied to the second temporarily holding mechanism to fix the seventh lens group so as to be unable to be displaced.

Abstract: A projector projects image light generated by an image generation unit, as an enlarged image via a projection system. The incident position of the image light on the projection system is moved by a lens shift mechanism. The projection system forms an intermediate image in the course of the optical path. A light-shielding mask is provided at an image forming position of the intermediate image. A light-shielding area by the light-shielding mask includes an area that does not overlap the intermediate image within a range of an effective image forming area at the image forming position of the intermediate image. For example, the light-shielding area is an area on the side opposite to the side to which the intermediate image is shifted, of the circular effective image forming area.

Abstract: A projection system that can be incorporated in a projector includes a first lens unit that makes a screen (enlargement-side image formation plane), which is located on the enlargement-side, conjugate with an intermediate image and a second lens unit that makes the intermediate image conjugate with a reduction-side image formation plane, which is located on the reduction side. The first lens unit has positive power, and the second lens unit has negative power. A second-lens-unit intermediate-image-side first lens, which is provided in the second lens unit and closest to the intermediate image, has positive power. The following expression is satisfied: ?0.3?fU1/fU2<0 where fU1 denotes the focal length of the first lens unit, and fU2 denotes the focal length of the second lens unit.

Abstract: A projection lens includes a plurality of lens groups each formed of at least one lens, and a lens barrel adapted to support each of the lens groups from an outer circumferential side. The lens barrel includes a first temporarily holding mechanism allowing the first lens group located at an end on a enlargement side to be displaced in a direction perpendicular to the optical axis, a first adhesive applied to the first temporarily holding mechanism to fix the first lens group so as to be unable to be displaced, a second temporarily holding mechanism allowing the seventh lens group located at an end on a reduction side to be displaced in a direction perpendicular to the optical axis, and a second adhesive applied to the second temporarily holding mechanism to fix the seventh lens group so as to be unable to be displaced.

Abstract: A projection optical system includes a first lens unit and a second lens unit interposing an intermediate image therebetween. The first lens unit includes two aspherical lenses (a first lens unit first lens and a first lens unit ninth lens), and a first lens unit cemented lens. The projection optical system satisfies the following Conditional Expressions (1) and (2) when the number of lens elements of the first lens unit and the number of lens elements of the second lens unit are set to be Num1 and Num2, respectively. In addition, refractive indexes and Abbe numbers of three lenses constituting the first lens unit cemented lens satisfy a predetermined conditional expression. Num2?7??(1) 1.5?Num1/Num2?2.

Abstract: A projection system includes a first lens group that does not move when the projection magnification is changed with the aid of the zoom function, and the first lens group includes a correction lens group that is moved in the direction of the optical axis to correct worsened astigmatism. The projection system satisfies the following conditional expressions (1) and (2): |?BF20|<P×FNO×?2??(1) 1.5<|f1/f|??(2) where P represents the pixel pitch in an image displayed by liquid crystal panels, FNO represents the F number of the entire lens system, ?BF represents the amount of movement of the back focus position in a case where the correction lens group is moved by the amount of movement for correction of the aberration that changes when the temperature changes by 20° C., f represents the focal length of the entire lens system, and f1 represents the focal length of the correction lens group.

Abstract: In a projector, a first fixation section and a second fixation section are formed at two places located at a distance in an optical axis direction in a lens barrel of a projection optical system. A holding member has contact with the first fixation section from an optical axis direction-rear side, and is fixed, an optical component housing of an illumination light guide optical system has contact with the holding member from the optical axis direction-rear side, and is fixed. A light modulating/combining optical system for generating image light has contact with the second fixation section from the optical axis direction-rear side and is fixed. In other words, the light modulating/combining optical system is directly fixed to the lens barrel without the intervention of the holding member for fixing the illumination light guide optical system to the lens barrel.