Abstract: An imaging optical system consists of, in order from a magnification side: a first optical system that forms an intermediate image on a position conjugate to a magnification side imaging surface; and a second optical system that re-forms the intermediate image on a reduction side imaging surface. The first optical system includes at least two focusing lens groups that move with different loci during focusing. The imaging optical system satisfies predetermined conditional expressions relating to the focusing lens groups.

Abstract: A first holding barrel, a first mirror bending a first optical axis of the first holding barrel at 90°, a second holding barrel, a second mirror bending a second optical axis of the second holding barrel at 90°, and a third holding barrel are disposed on an optical axis from a screen side to an image forming panel. A first connection member connects the first holding barrel including the first mirror to the second holding barrel to be rotationally movable in increments of 90°. A second connection member connects the second holding barrel and the second mirror to the third holding barrel to be rotationally movable in increments of 90°. An orientation of a display image of the image forming panel is changed based on rotational movement states of an optical axis of a first sensor and an optical axis of a second sensor to make an orientation of a projection image on the screen match an original image.

Abstract: The imaging optical system consists of, in order from a magnification side: a first imaging optical system that forms an intermediate image on a position conjugate to a magnification side imaging surface; and a second imaging optical system that re-forms the intermediate image on a reduction side imaging surface. The first imaging optical system consists of, in order from the magnification side, a first A lens group, a first optical path deflection unit that deflects an optical path, a first B lens group, and a second optical path deflection unit that deflects the optical path. In addition, the intermediate image is formed between the second optical path deflection unit and the second imaging optical system.

Abstract: A first optical system, a first mirror, a second optical system, a second mirror, and a third optical system are disposed in order on an optical axis from an image forming panel to a screen. A first optical axis of the first optical system, a second optical axis of the second optical system, and a third optical axis of the third optical system are formed in a U shape, and orientations of luminous fluxes of the first optical axis and the third optical axis are reversed. The first mirror, the second optical system, the second mirror, and the third optical system are held to make a second holding barrel with respect to the first optical system. The second holding barrel is rotationally moved in a rotational movement range of 45° with respect to a first holding barrel. In projecting portrait image instead of a landscape image, the second holding barrel is rotated in increments of 45° with respect to the first holding barrel.

Abstract: The imaging optical system consists of, in order from a magnification side: a catoptric system; and a dioptric system that includes a plurality of lenses. The dioptric system forms a first intermediate image between the dioptric system and the catoptric system on an optical path and at a position conjugate to a reduction side imaging surface, and the catoptric system re-forms the first intermediate image on a magnification side imaging surface. The catoptric system consists of, in order from the magnification side along the optical path, a first reflective surface having a positive power, a second reflective surface having a curved surface shape, and a third reflective surface having a positive power.

Abstract: In a cleaning device, a signal processing circuit determines that a foreign substance has adhered to a surface of a protection cover based on at least two pieces of information among a change amount of a resonant frequency when a vibration portion is driven at a first voltage, a change amount of a current value relating to an impedance detected by an impedance detector, and a temporal change of an image captured by an imaging portion, and cleans the surface of the protection cover by controlling the vibration portion in accordance with the determination.

Abstract: The imaging optical system forms a first intermediate image at a position conjugate to the magnification side imaging surface and a second intermediate image at a position closer to a reduction side than the first intermediate image on an optical path and conjugate to the first intermediate image. The imaging optical system consists of a first optical system, a second optical system, and a third optical system in order from a magnification side to the reduction side along the optical path. The imaging optical system is configured to be telecentric on the reduction side. The imaging optical system satisfies predetermined conditional expressions.

Abstract: The imaging optical system forms a first intermediate image at a position conjugate to the magnification side imaging surface and a second intermediate image at a position closer to a reduction side than the first intermediate image on an optical path and conjugate to the first intermediate image. The imaging optical system consists of a first optical system, a second optical system, and a third optical system in order from a magnification side to the reduction side along the optical path. The imaging optical system is configured to be telecentric on the reduction side. The imaging optical system satisfies predetermined conditional expressions.

Abstract: The imaging optical system forms a first intermediate image at a position conjugate to a magnification side imaging surface and a second intermediate image at a position closer to a reduction side than the first intermediate image on an optical path and conjugate to the first intermediate image. The imaging optical system consists of a first optical system, a second optical system, and a third optical system in order from the magnification side to the reduction side along the optical path. The imaging optical system does not include a reflective member having a power.

Abstract: A projection optical system is constituted by, in order from the reduction side, a first optical system for forming an image displayed by image display elements as an intermediate image, a first optical path bending means that bends an optical path with a reflective surface, and a second optical system for forming the intermediate image on a magnification side conjugate plane. The second optical system is constituted by, in order from the reduction side, a first lens group having a positive refractive power, a second optical path bending means that bends an optical path with a reflective surface, and a second lens group having a positive refractive power. Conditional Formulae (1) and (2) below are satisfied. 10.0<TL1/|f|<50.0??(1) 4.0<TL21/|f|<30.0??(2).

Abstract: The imaging optical system consists of, in order from a magnification side, a first optical system and a second optical system. The first optical system consists of, in order from the magnification side, a first A lens group having a positive refractive power and a first B lens group having a positive refractive power with the maximum air gap interposed between the lens surfaces in the first optical system. The second optical system consists of, in order from the magnification side, a second A lens group having a positive refractive power and a second B lens group having a positive refractive power with the maximum air gap interposed between the lens surfaces in the second optical system.

Abstract: A projection optical system is constituted by, in order from the reduction side, a first optical system for forming an image displayed by image display elements as an intermediate image, a first optical path bending means that bends an optical path with a reflective surface, and a second optical system for forming the intermediate image on a magnification side conjugate plane. The second optical system is constituted by, in order from the reduction side, a first lens group having a positive refractive power, a second optical path bending means that bends an optical path with a reflective surface, and a second lens group having a positive refractive power. Conditional Formulae (1) and (2) below are satisfied. 10.0<TL1/|f|<50.0??(1) 4.0<TL21/|f|<30.0??(2).

Abstract: The imaging lens includes at least one positive lens that satisfies predetermined conditional expressions (1) to (3) indicating conditions in which dispersion is relatively low and refractive index is high while having a negative rate of change of the refractive index. In a case where a lens that satisfies a conditional expression (4) meaning a low dispersion material is included, the lens that satisfies the conditional expression (4) satisfies a predetermined conditional expression (5).

Abstract: In the imaging optical system that consists of a first optical system and a second optical system in order from a magnified side, and has an intermediate image formed between the first optical system and the second optical system, a focus group moving during focusing is included between a most magnified side of the first optical system and a position at which a principal ray of light having a maximum angle of view and an optical axis of the first optical system intersect each other, and a predetermined conditional expression relating to the focus group is satisfied.

Abstract: The zoom lens consists of, in order from an object side: a first lens group (G1) that remains stationary during zooming and has a positive refractive power; and a subsequent section that consists of five or more lens groups including at least four movable lens groups. The first lens group (G1) is set as an A constituent section (SA), and a lens closest to the object side in the A constituent section (SA) has a negative refractive power. A lens group having a stop is set as a C constituent section (SC), and the C constituent section (SC) moves to the object side during zooming from a wide-angle end to a telephoto end, and then moves toward an image side. A spacing between the A constituent section (SA) and the C constituent section (SC) is set as a B constituent section (SB), and the B constituent section (SB) consists of one or two the movable lens groups, and has a negative refractive power. In addition, the zoom lens satisfies predetermined conditional expressions.

Abstract: The imaging optical system consists of, in order from a magnification side: a catoptric system; and a dioptric system that includes a plurality of lenses. The dioptric system forms a first intermediate image between the dioptric system and the catoptric system on an optical path and at a position conjugate to a reduction side imaging surface, and the catoptric system re-forms the first intermediate image on a magnification side imaging surface. The catoptric system consists of a first reflective surface, a second reflective surface, and a third reflective surface in order along the optical path from the magnification side. The first reflective surface and the third reflective surface are formed on one member and have the same surface shapes.

Abstract: An imaging optical system consists of, in order from a magnification side: a first imaging optical system that forms an intermediate image on a position conjugate to a magnification side imaging surface; and a second imaging optical system that re-forms the intermediate image on a reduction side imaging surface. The second imaging optical system consists of a plurality of lens groups including at least two movable lens groups which move during zooming. The imaging optical system satisfies predetermined conditional expressions.

Abstract: A projector includes a projection lens and a projector body. In the projection lens, a U-shaped optical path is formed by optical axis to optical axis. A lens barrel is a U-shaped barrel. A housing of the projector body includes a storage section. The projection lens is supported rotatably about the optical axis with respect to the housing, in an up-down direction and a right-left direction of the housing perpendicular to the optical axis, between a first position where the projection lens is stored inside a storage section provided in the housing and a second position where the projection lens is protruding from the housing.

Abstract: A first optical system, a first mirror, a second optical system, a second mirror, and a third optical system are disposed in order on an optical axis from an image forming panel to a screen. A first optical axis of the first optical system, a second optical axis of the second optical system, and a third optical axis of the third optical system are formed in a U shape, and orientations of luminous fluxes of the first optical axis and the third optical axis are reversed. The first mirror, the second optical system, the second mirror, and the third optical system are held to make a second holding barrel with respect to the first optical system. The second holding barrel is rotationally moved in a rotational movement range of 45° with respect to a first holding barrel. In projecting portrait image instead of a landscape image, the second holding barrel is rotated in increments of 45° with respect to the first holding barrel.

Abstract: A first holding barrel, a first mirror bending a first optical axis of the first holding barrel at 90°, a second holding barrel, a second mirror bending a second optical axis of the second holding barrel at 90°, and a third holding barrel are disposed on an optical axis from a screen side to an image forming panel. A first connection member connects the first holding barrel including the first mirror to the second holding barrel to be rotationally movable in increments of 90°. A second connection member connects the second holding barrel and the second mirror to the third holding barrel to be rotationally movable in increments of 90°. An orientation of a display image of the image forming panel is changed based on rotational movement states of an optical axis of a first sensor and an optical axis of a second sensor to make an orientation of a projection image on the screen match an original image.