Abstract: An observation apparatus is configured to enable an observer to observe an image displayed on an image display surface. The observation apparatus includes an observation optical system that includes a half-transmissive reflective surface, and a reflective polarizer configured to transmit linearly polarized light in a first direction and to reflect linearly polarized light in a second direction orthogonal to the first direction, and an imaging optical system configured to guide light that has transmitted through the reflective polarizer to an image pickup apparatus configured to image an observation side. A transmittance at a wavelength of 850 nm of linearly polarized light in the second direction of the reflective polarizer is 30% or higher.

Abstract: An optical system is configured to form an enlarged image of a display surface of an image display element and includes, in order from a side of an exit pupil to a side of the display surface, a first half-transmissive reflective surface and a second half-transmissive reflective surface. The optical system has a first optical path on which light from the display surface transmits through the second half-transmissive reflective surface, is reflected by the first half-transmissive reflective surface, is reflected by the second half-transmissive reflective surface, transmits through the first half-transmissive reflective surface, and is guided to the exit pupil, and a second optical path on which light from the side of the exit pupil transmits through the first half-transmissive reflective surface, transmits through the second half-transmissive reflective surface, and is guided to an image sensor.

Abstract: An observation optical system for use in observing an image displayed on an image displaying surface, includes, in order from an observation surface side to the image displaying surface side: a first lens having a first transmission reflective surface and a first transmissive surface; and a second lens having a second transmission reflective surface and a second transmissive surface, in which the first lens and the second lens are arranged via an interval interposed therebetween; light from the image displaying surface transmits through the second lens, is reflected by the first transmission reflective surface, is reflected by the second transmission reflective surface, is transmitted through the first lens, and then travels toward the observation surface side; and a focal length of the first lens and a focal length of the observation optical system are appropriately set.

Abstract: A lens apparatus includes an optical system L0 including a plurality of lenses. The optical system L0 is changeable to a first state in which a focal length of the optical system L0 is a first focal length and a second state in which the focal length is a second focal length shorter than the first focal length, by changing one or some of the plurality of lenses. The maximum image heights and maximum angle of views in the first state and the second state are substantially constant and satisfy a predetermined condition.

Abstract: An observation optical system for use in observing an image displayed on an image displaying surface, includes, in order from an observation surface side to the image displaying surface side: a first lens having a first transmission reflective surface and a first transmissive surface; and a second lens having a second transmission reflective surface and a second transmissive surface, in which the first lens and the second lens are arranged via an interval interposed therebetween; light from the image displaying surface transmits through the second lens, is reflected by the first transmission reflective surface, is reflected by the second transmission reflective surface, is transmitted through the first lens, and then travels toward the observation surface side; and a focal length of the first lens and a focal length of the observation optical system are appropriately set.

Abstract: A lens apparatus includes an optical system L0 including a plurality of lenses. The optical system L0 is changeable to a first state in which a focal length of the optical system L0 is a first focal length and a second state in which the focal length is a second focal length shorter than the first focal length, by changing one or some of the plurality of lenses. The maximum image heights and maximum angle of views in the first state and the second state are substantially constant and satisfy a predetermined condition.

Abstract: A zoom lens including: a positive first lens unit; a negative second lens unit; and a positive rear lens group, an interval of adjacent lens units is changed during zooming, the rear lens group includes from an object side: a positive lens system; an aperture stop; and a negative partial lens system, the first lens unit and the aperture stop are positioned closer to the object side at a telephoto end than at a wide angle end, and a combined focal length of a front lens system between the first lens unit and the aperture stop at the wide angle end, an absolute value of a distance on an optical axis from a first lens surface to the aperture stop at the wide angle end, a focal length of the first lens unit, and a focal length of the zoom lens at the wide angle end is appropriately set.

Abstract: A zoom lens includes, in order from an object side to an image side, first to fifth lens units respectively having positive, negative, positive, positive, and negative refractive powers. The first lens unit does not move for zooming, and each of the distances between the lens units adjacent to each other is changed during zooming. Lateral magnifications ?2w and ?2t of the second lens unit at a wide angle end and a telephoto end, respectively, lateral magnifications ?3w and ?3t of the third lens unit at the wide angle end and the telephoto end, respectively, lateral magnifications ?4w and ?4t of the fourth lens unit at the wide angle end and the telephoto end, respectively, a focal length f5 of the fifth lens unit, and an amount of movement M5 of the fifth lens unit in zooming from the wide angle end to the telephoto end are appropriately set.

Abstract: In an image pickup apparatus including an optical system and an image pickup element, the optical system includes, in order from an object side to an image side, lens(es), an aperture stop, and lens(es). The lens arranged at the most image side in the optical system is a negative lens, and an infrared cut film is formed on at least one lens surface in the optical system. An optical axial distance from the exit pupil of the optical system to the image plane when focusing on an infinite object, an optical axial distance from the lens surface provided with the infrared cut film to the image plane when focusing on the infinite distance object, the curvature radius of the lens surface provided with the infrared cut film, and a radius of a circle circumscribed about an effective imaging area of the image pickup element are appropriately set.

Abstract: A zoom lens includes, in order from an object side to an image side, first to fifth lens units respectively having positive, negative, positive, positive, and negative refractive powers. The first lens unit does not move for zooming, and each of the distances between the lens units adjacent to each other is changed during zooming. Lateral magnifications ?2w and ?2t of the second lens unit at a wide angle end and a telephoto end, respectively, lateral magnifications ?3w and ?3t of the third lens unit at the wide angle end and the telephoto end, respectively, lateral magnifications ?4w and ?4t of the fourth lens unit at the wide angle end and the telephoto end, respectively, a focal length f5 of the fifth lens unit, and an amount of movement M5 of the fifth lens unit in zooming from the wide angle end to the telephoto end are appropriately set.

Abstract: In an image pickup apparatus including an optical system and an image pickup element, the optical system includes, in order from an object side to an image side, lens(es), an aperture stop, and lens(es). The lens arranged at the most image side in the optical system is a negative lens, and an infrared cut film is formed on at least one lens surface in the optical system. An optical axial distance from the exit pupil of the optical system to the image plane when focusing on an infinite object, an optical axial distance from the lens surface provided with the infrared cut film to the image plane when focusing on the infinite distance object, the curvature radius of the lens surface provided with the infrared cut film, and a radius of a circle circumscribed about an effective imaging area of the image pickup element are appropriately set.

Abstract: A zoom lens includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a rear lens group having one or more lens units. The first through third lens units and the rear lens group are disposed in this order from an object side to an image side. The first lens unit is stationary when zooming. A reflection member including a reflective surface configured to bend an optical path is disposed in an optical path of the first lens unit. The second lens unit moves in a direction having a component in a direction perpendicular to an optical axis when correcting image blurring. The lateral magnification ?2t of the second lens unit when being focused at infinity at a telephoto end is set appropriately.

Abstract: A zoom lens including: a positive first lens unit; a negative second lens unit; and a positive rear lens group, an interval of adjacent lens units is changed during zooming, the rear lens group includes from an object side: a positive lens system; an aperture stop; and a negative partial lens system, the first lens unit and the aperture stop are positioned closer to the object side at a telephoto end than at a wide angle end, and a combined focal length of a front lens system between the first lens unit and the aperture stop at the wide angle end, an absolute value of a distance on an optical axis from a first lens surface to the aperture stop at the wide angle end, a focal length of the first lens unit, and a focal length of the zoom lens at the wide angle end is appropriately set.

Abstract: A zoom lens includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power, disposed in order from an object side to an image side, and an aperture stop between a lens surface closest to the object side of the second lens unit and a lens surface closest to the object side of the third lens unit, the third lens unit is moved to the image side during a focusing operation from an infinite object to a short distance object, the first lens unit is configured by at most two negative lenses and one positive lens, the third lens unit is configured by a single lens or a cemented lens, and an appropriate conditional expression are met.

Abstract: A zoom lens consists of, in order from an object side to an image side, a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a third lens unit having negative refractive power. The first lens unit and the second lens unit move during zooming to make a distance between the first lens unit and the second lens unit larger at a telephoto end than at a wide-angle end. The third lens unit consists of, in order from the object side to the image side, a first lens subunit having positive refractive power and a second lens subunit having negative refractive power, and the second lens subunit moves toward the image side during focusing from an infinite-distance object to a near-distance object.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a reflecting unit for bending an optical path, and a rear lens group including two or more lens units, wherein, during zooming, the first and second lens units are moved and the reflecting unit is not moved, and wherein an amount of movement of the first lens unit during zooming from a wide-angle end to a telephoto end, a distance on an optical axis from a reflecting surface of the reflecting unit to an image plane, a distance on the optical axis from a lens surface of the second lens unit closest to the image side to the reflection surface of the reflecting unit at the wide-angle end, and a focal length of the second lens unit are appropriately set.

Abstract: The zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a rear unit including one or more lens units, a distance between every adjacent lens units varies during zooming, and an aperture diaphragm on the image side of the first lens unit, a combined focal length of the rear unit at a wide-angle end being positive. One lens unit LG on the object side of the aperture diaphragm is made of a solid material, and includes an optical element GnNL having a negative refractive power and another optical element having a positive refractive power, and the predetermined conditions are satisfied.

Abstract: A zoom lens includes, a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, a reflective element, and a rear lens group including two or more lens units and an aperture stop, in which the first lens unit, the second lens unit, and two or more lens units of the rear lens group are moved while the reflective element is stationary during zooming, wherein movement amounts M1 and M2 of the first and second lens units during zooming, a movement amount Ms of the aperture stop, and focal lengths fw and ft of the entire zoom lens at the wide-angle end and the telephoto end, respectively, lateral magnifications ?2w and ?2t of the second lens unit, a distance LSw from the first lens surface to the aperture stop at the wide-angle end are appropriately set.

Abstract: A zoom lens includes, in order from object side to image side, a positive first lens unit, a negative second lens unit, a positive third lens unit, a negative fourth lens unit, and a rear lens unit including, in order from object side to image side, a positive first lens subunit, a negative second lens subunit, and a positive third lens subunit. The relationship between the combined focal length of the first and second lens units at wide-angle end, the combined focal length of the third lens unit and the lens units on the image side of the third lens unit at wide-angle end, the focal length of the second lens subunit, and the focal length of the rear lens unit at telephoto end is appropriately set.

Abstract: A zoom lens includes first to fifth lens unit having negative, positive, positive, negative, and positive refractive powers, in an order from an object side to an image side, an interval of each lens unit is configured to be changed in zooming, the first lens unit, in order from the object side to the image side, consists of one or two negative lenses and one positive lens, the second lens unit consists of one lens component that moves to the image side in focusing on an object at an infinite distance to a short distance object, and an interval D23, combined focal lengths D23w, f23w, and f4Rw, and a length D2 are appropriately set.