Abstract: A lens system for imaging includes, in order from the object side, a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, a stop, and a fourth lens group with positive refractive power. The third lens group includes, closest to the image plane side, a cemented lens on the object side of the stop and whose image plane-side surface includes a concave surface on the object side. The fourth lens group includes, closest to the object side, a cemented lens on the image plane side of the stop and whose object-side surface includes a concave surface on the image plane side. A radius of curvature g3er of the object side concave surface and the radius of curvature g4fr of the image plane side concave surface satisfy the following condition: 2.5?|g4fr/g3er|?4.0.

Abstract: In a projection optical system for projecting an optical image from a first image plane on a reduction side onto a second image plane on a magnification side, the system includes an achromatic lens including a positive lens and a negative lens separately arranged in this order from the reduction side toward the magnification side, and the negative lens having a refractive index of 1.7 or higher and an Abbe's number of 55 or less satisfies the following expression: 3.5?|R|/|f|??(1), where the radius of curvature of a light incident surface is R and the focal length of an entire projection optical system is f.

Abstract: A lens barrel has at least one movable lens group that can move in one direction and the other direction along the optical axis, the lens barrel comprising: a movable lens frame; a voice coil motor for driving a movable lens group and the movable lens frame along the optical axis; and a stopper mechanism brought into contact with the movable lens frame. The stopper mechanism includes a stopper member that moves between a retracted position where the stopper member does not touch the movable lens frame when the voice coil motor is energized, and an abutting position where the stopper member is brought into contact with the movable lens frame when the voice coil motor is not energized.

Abstract: A lens system (10) for image pickup includes, in order from an object side (11), a first lens group (G1) that has negative refractive power and is fixed during focusing, a second lens group (G2) that has positive refractive power and moves during focusing, a third lens group (G3) that has positive refractive power and is fixed during focusing, and a fourth lens group (G4) that has a stop disposed on the object side, is disposed closest to an image plane side, has positive refractive power, and is fixed during focusing. The first lens group includes a first lens (L11) with positive refractive power that is disposed closest to the object side.

Abstract: An optical diaphragm device includes: diaphragm blades each including a first fixing boss and a moving boss protruding from the other surface of a first planar plate toward a side in a second direction; light leakage prevention blades each having a second fixing boss and forming a pair with the diaphragm blade; a drive ring on which first cam grooves are formed; and a housing body capable of housing the diaphragm blades, the light leakage prevention blades, and the drive ring. A second cam groove is further formed in the light leakage prevention blade, the moving boss of the diaphragm blade is inserted into the second cam groove of the light leakage prevention blade, and is inserted into the first cam groove of the drive ring. The light leakage prevention blade has a light leakage prevention blade extending portion which extends toward the other side from the second fixing boss.

Abstract: A lens system (10) for image pickup includes, in order from an object side (11), a first lens group (G1) with positive refractive power that moves during focusing, a second lens group (G2) with positive refractive power that is disposed on an opposite side of a stop (St) to the first lens group and moves during focusing, and a third lens group (G3) with positive refractive power that is disposed closest to an image plane side (12) and is fixed. The third lens group includes, in order from the object side, a cemented lens (B31) composed of a lens with positive refractive power and a lens with negative refractive power. A combined focal length (f3) of the third lens group and a combined focal length (f12) of the first lens group and the second lens group satisfy a following condition: 2?f3/f12?200.

Abstract: A zoom lens system (10) for imaging, includes, in order from an object side (11); a first lens group (G1) with negative refractive power that moves at the time of zooming; a second lens group (G2) with a positive refractive power that moves at the time of zooming, the second lens group including an aperture stop (St); a third lens group (G3) with a positive refractive power, the position of which is fixed relative to the image plane. The second lens group includes: a first sub-lens group (S1) with a positive refractive power arranged on the object side and having the aperture stop; and a second sub-lens group (S2) with a negative refractive power arranged on the image plane side and configured to move independently of the first sub-lens group at the time of focusing.

Abstract: An optical system (10) for image pickup includes a first refractive optical system (Si) disposed on an object side with respect to an aperture stop (St) and a second refractive optical system (S2) disposed on an image plane side with respect to the aperture stop. The first refractive optical system includes, in order from the object side (11), a first lens group (G1) with positive refractive power, a second lens group (G2) with positive refractive power, and a third lens group (G3) with negative refractive power. The second refractive optical system includes, in order from the object side (11), a fourth lens group (G4) with positive refractive power, a fifth lens group (G5) with positive refractive power, and a sixth lens group (G6) with negative refractive power. When focusing from infinity to a short distance, the second lens group and the fourth lens group move toward the object side.

Abstract: An optical system includes: a first lens group with negative refractive power at an object side of an aperture stop; a second lens group with positive refractive power at an image plane side of the aperture stop; and a third lens group with positive refractive power at the image plane side of the second lens group. The first lens group includes a first lens with negative refractive power and concave image plane side, a second lens of meniscus type, with negative refractive power, and convex image plane side, and a third lens with positive refractive power and convex object side. The second lens group includes a fourth lens with positive refractive power and convex image plane side; a fifth lens of meniscus type, with negative refractive power, and convex object side; and a sixth lens with negative refractive power and concave object side.

Abstract: An optical diaphragm device includes a plurality of diaphragm blades including a first fixing boss protruding from one surface of a first planar plate toward a side in a first direction; and a moving boss protruding from another surface of the first planar plate toward a side in a second direction. The optical diagram device includes a plurality of light leakage prevention blades including a second fixing boss protruding from one surface of a second planar plate toward the side in the first direction. The optical diagram device includes a drive ring including a plurality of first cam grooves; a housing body capable of accommodating the diaphragm blades, the light leakage prevention blades, and the drive ring. A second cam groove is in the light leakage prevention blade. The moving boss is in the second cam groove, and is in the first cam groove.

Abstract: A projection optical projects from a first image plane on a reducing side onto a second image plane on a magnifying side includes: a first optical system with a plurality of lenses that forms a first intermediate image on a first side of an optical axis inside the first optical system by light that is incident from the reducing side, into a second intermediate image on a second side of the optical axis at a position closer to the magnifying side than the first optical system. A second optical system includes a first reflective surface with positive power that is positioned closer to the magnifying side than the second intermediate image. The first optical system includes an intermediate lens. The first intermediate image is formed to be inclined to be closer to the reducing side as a distance from the optical axis increases so as to straddle the intermediate lens.

Abstract: A projection optical system (2) projects from a DMD (7) on a reducing side onto a screen (9) on an enlargement side, and includes: a first refractive optical system (10) that forms a first intermediate image (51) on the enlargement side using light incident from the reducing side; a second refractive optical system (20) that forms the first intermediate image (51) on the reducing side into a second intermediate image (52) on the enlargement side; and a first reflective optical system (30) including a first reflective surface (31a) with positive refractive power that is positioned on the enlargement side of the second intermediate image (52), wherein the second refractive optical system (20) includes a first focus lens group (61) that moves when focusing is carried out, and the first focus lens group (61) includes at least one lens (L13) included in the second refractive optical system (20).

Abstract: A projection optical system (1) that projects from a first image plane on a reducing side to a second image plane on an enlargement side, including a first refractive optical system (11) that includes eight lenses (L1) to (L8) and forms a first intermediate image (31) on the enlargement side using light that is incident from the reducing side, a second refractive optical system (12) that includes six lenses (L9) to (L14) and forms the first intermediate image (31) on the reducing side into a second intermediate image (32) on the enlargement side, and a first reflective optical system (20) that includes a first reflective surface (21a) with positive refractive power that is positioned closer to the enlargement side than the second intermediate image (32).

Abstract: In order to provide a projection lens barrel and a projection display device that are capable of correcting the optical characteristics of a plurality of lens groups, a projection lens barrel, comprising a lens optical system causing light from an image display element to be formed as a projected image on a screen, also comprises correction mechanisms that move each of at least two lens groups along an optical axis and correct the optical characteristics to be corrected, said lens groups each having different optical characteristics for correction in order to suppress reduction in image quality of a projected image caused by changes in optical characteristics caused by temperature changes in the projection lens barrel.

Abstract: An optical system (10) for image pickup includes a first refractive optical system (Si) disposed on an object side with respect to an aperture stop (St) and a second refractive optical system (S2) disposed on an image plane side with respect to the aperture stop. The first refractive optical system includes, in order from the object side (11), a first lens group (G1) with positive refractive power, a second lens group (G2) with positive refractive power, and a third lens group (G3) with negative refractive power. The second refractive optical system includes, in order from the object side (11), a fourth lens group (G4) with positive refractive power, a fifth lens group (G5) with positive refractive power, and a sixth lens group (G6) with negative refractive power. When focusing from infinity to a short distance, the second lens group and the fourth lens group move toward the object side.

Abstract: A zoom lens system includes: a primary image forming lens group that forms light from an object side into an intermediate image and a relay lens group that forms light from the intermediate image into a final image. The primary image forming lens group includes, in order from the object side, a first fixed lens group G1 with negative refractive power, a stop St, and a second fixed lens group G2 with positive refractive power, and the relay lens group includes, in order from the object side, a third fixed lens group G3 with negative refractive power, a first moving lens group G4 with positive refractive power, and a second moving lens group G5 with positive refractive power.

Abstract: A projection optical system (10) projects from a first image plane (5) on a reducing side to a second image plane (6) on an enlargement side. The projection optical system (10) includes a first optical system (11) that includes a plurality of lenses and forms a first intermediate image (51) formed inside the first optical system (11) by light incident from the reducing side into a second intermediate image (52) on the enlargement side of the first optical system; a second optical system (12) that includes a first reflective surface (M1) with positive refractive power which is positioned further to the enlargement side than the second intermediate image (52); and a glass block (30) that is disposed between the first optical system (11) and the first reflective surface (M1), the glass block (30) passing light rays from the first optical system to the second intermediate image.

Abstract: In a reflection mirror having a concave curved reflection surface, when a surface of the reflection mirror on the side where the reflection surface is formed is a front surface, a surface thereof opposite to the front surface is a rear surface, a direction parallel to an optical axis of the reflection mirror is a first direction, and a direction from the front surface toward the rear surface which is oriented to one side in the first direction is a second direction, the rear surface of the reflection mirror has a flat surface orthogonal to the first direction and a wall surface that rises from at least a part of a region around the flat surface toward the second direction.

Abstract: A lens unit includes a display member that is in a cylindrical shape, that rotates around an optical axis of the lens unit, and that has a scale indicating a photographing distance on an outer circumference surface thereof, and a window member that is provided over the display member, that exposes part of the outer circumference surface including the scale of the display member, and that hides the other part of the outer circumference surface of the display member. The photographing distance has first and second length units. The display member is movable along the optical axis between a first position and a second position. When the display member is in the first positon, the window member exposes the first length unit. Further, when the display member is in the second position, the window member exposes the second length unit.

Abstract: An optical diaphragm device includes: diaphragm blades each having a first fixing boss protruding from one surface of a first planar plate toward a side in a first direction and a moving boss protruding from the other surface of the first planar plate toward a side in a second direction; light leakage prevention blades each having a second fixing boss protruding from one surface of a second planar plate toward the side in the first direction and forming a pair with the diaphragm blade; a drive ring with cam grooves; and a housing body accommodating the diaphragm blades, light leakage prevention blades and drive ring. A second cam groove is formed on the light leakage prevention blade. The moving boss of the diaphragm blade is inserted into the second cam groove of the light leakage prevention blade, and is inserted into the first cam groove of the drive ring.