Abstract: One or more eyepiece lenses, one or more observation apparatuses and one or more imaging apparatuses are discussed herein. In at least one embodiment, an eyepiece lens comprises, in order from an object side to an observation side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens having a negative refractive power, and a fifth lens having a positive refractive power, wherein a focal length of the fifth lens is shorter than a focal length of the third lens, and the focal length of the third lens is shorter than a focal length of the first lens.

Abstract: Provided is a zoom lens including, in order from an object side to an image side: a first lens unit having a positive refractive power which does not move for zooming; a second lens unit having a negative refractive power which moves during zooming; and an N-th lens unit having a positive refractive power which does not move for zooming and is arranged closest to the image side. In the zoom lens, the N-th lens unit includes in order from an object side: a first sub-lens unit; and a second sub-lens unit which is movable, and a lateral magnification at a wide angle end of the N-th lens unit and a lateral magnification at a wide angle end of the second sub-lens unit of the N-th lens unit when an axial ray enters from infinity in a state in which focus is at the infinity are appropriately set.

Abstract: A zoom lens includes in order from object side to image side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during zooming; and a positive N-th lens unit that does not move for zooming, the N-th lens unit being arranged closest to the image side. The first lens unit includes, in order from object side to image side: a negative first sub-lens unit that does not move for focusing; a positive second sub-lens unit that moves along an optical axis during focusing; and a positive third sub-lens unit that does not move for focusing. Focal length of the first lens unit, focal length at wide angle end of the zoom lens, and lateral magnification at wide angle end satisfy predetermined conditions.

Abstract: An optical apparatus used for a 3D image pickup apparatus for taking two subject images having a disparity by using two lens apparatuses, each of which is directly connectable to an image pickup apparatus, and one image pickup apparatus, the optical apparatus including: a first attaching unit for detachably attaching a first lens apparatus; a second attaching unit for detachably attaching a second lens apparatus; a camera attaching unit for detachably attaching the image pickup apparatus, the image pickup apparatus including an image pickup portion; and a switch unit for alternately switching light rays from the first and second lens apparatuses to guide the light ray to the image pickup apparatus in a state that the first and second lens apparatuses and the image pickup apparatus are connected to the optical apparatus. Intermediate images are formed in the optical apparatus by the first and second lens apparatuses.

Abstract: A zoom lens includes in order from object side to image side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during zooming; and a positive N-th lens unit that does not move for zooming, the N-th lens unit being arranged closest to the image side. The first lens unit includes, in order from object side to image side: a negative first sub-lens unit that does not move for focusing; a positive second sub-lens unit that moves along an optical axis during focusing; and a positive third sub-lens unit that does not move for focusing. Focal length of the first lens unit, focal length at wide angle end of the zoom lens, and lateral magnification at wide angle end satisfy predetermined conditions.

Abstract: Provided is a zoom lens including, in order from an object side to an image side: a first lens unit having a positive refractive power which does not move for zooming; a second lens unit having a negative refractive power which moves during zooming; and an N-th lens unit having a positive refractive power which does not move for zooming and is arranged closest to the image side. In the zoom lens, the N-th lens unit includes in order from an object side: a first sub-lens unit; and a second sub-lens unit which is movable, and a lateral magnification at a wide angle end of the N-th lens unit and a lateral magnification at a wide angle end of the second sub-lens unit of the N-th lens unit when an axial ray enters from infinity in a state in which focus is at the infinity are appropriately set.

Abstract: A zoom lens includes, in order from an object side: a positive first lens unit that does not move for zooming and comprises a negative first sub-lens unit, a positive second sub-lens unit that moves during adjustment of a focal point, and a positive third sub-lens unit composed of at least one negative lens, and at least two positive lenses; a lens group including at least two lens units that move during zooming; an aperture stop; and a positive last lens unit that does not move for zooming. Focal lengths of the first lens unit, the first sub-lens unit, and the zoom lens at a wide angle end, imaging magnification of the last lens unit, average values of an Abbe constant for d-line of the at least one negative lens and of the at least two positive lenses are appropriately set.

Abstract: A zoom lens includes a first lens unit, a second lens unit, a third lens unit and a fourth lens unit that includes a 41 lens group and a 42 lens group. The 41 lens group includes a 411 lens group and a 412 lens group. A lens surface on a most image side of the 411 lens unit has a shape convex to the image side and a lens surface on the most object side of the 412 lens unit has a shape concave to the object side. A curvature radius r411 of the lens surface on the most image side of the 411 lens unit, a curvature radius r412 of the lens surface on the most object side of the 412 lens unit, and lateral magnification ?3w of the third lens unit at a wide-angle end are respectively appropriately set.

Abstract: A lens apparatus includes, in order from an object side: a first lens unit; an aperture stop; and a positive second lens unit. The first lens unit includes, in order from the object side, a first negative lens, a second negative lens having at least one aspheric surface, and a positive lens. The second lens unit includes at least one negative lens and at least two positive lenses. The first and second negative lenses of the first lens unit are meniscus lenses having a surface convex toward the object side. The focal length of the optical system, the focal lengths of the first and second lens units, the mean values of Abbe constants of the positive lens and the negative lenses of the first lens unit, and the mean values of Abbe constants of the positive lenses and the negative lenses of the second lens unit are appropriately configured.

Abstract: A 3D-image pickup optical system includes: a pair of optical systems each of which includes a magnification-varying lens unit, an aperture stop, a first lens unit and a first reflective member in a sequential order from an object side, the optical systems having optical axes offset from each other; a second lens unit that receives object light fluxes from the pair of optical systems; a second reflective member that guides the object light fluxes from the pair of optical systems to the second lens unit; and a switching unit that is disposed in an object side of the second reflective member, and alternately guides the pair of the object light fluxes respectively from the pair of optical systems to the second reflective member.

Abstract: A zoom lens includes a first lens unit, a second lens unit, a third lens unit and a fourth lens unit that includes a 41 lens group and a 42 lens group. The 41 lens group includes a 411 lens group and a 412 lens group. A lens surface on a most image side of the 411 lens unit has a shape convex to the image side and a lens surface on the most object side of the 412 lens unit has a shape concave to the object side. A curvature radius r411 of the lens surface on the most image side of the 411 lens unit, a curvature radius r412 of the lens surface on the most object side of the 412 lens unit, and lateral magnification ?3w of the third lens unit at a wide-angle end are respectively appropriately set.

Abstract: An image pickup optical system including: a first prism including: a first incident surface where subject beam enters; a division surface for dividing the beam from the first incident surface into image-pickup beam and focus-detection beam; and a first exit surface from which reflection beam reflected on the division surface, the image-pickup beam or the focus-detection beam, exits; and a second prism including: a second incident surface on which transmission beam passing through the division surface, the image-pickup beam or focus-detection beam, enters; and a second exit surface from which the transmission beam exits, wherein the reflection beam is reflected on the division surface, reflected on the first incident surface, and reflected on the division surface to reach the first exit surface, and satisfying 0.1<DA/DB<0.5, where DA and DB indicate beam diameters of beams toward the image pickup elements for focus detection and for image pickup.

Abstract: A zoom lens system including, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power; an aperture stop; and a fourth lens unit having a positive refractive power and including a front lens subunit and a rear lens subunit in which Abbe numbers of lenses in the rear lens subunit satisfy the following expression, 0.400<?m/(?rp??rn)<0.630, where ?m represents the Abbe number of the material of a first positive lens having the largest dispersion of the positive lenses included in the rear lens subunit, ?rp represents the average Abbe number of materials of positive lenses other than the first positive lens in the rear lens subunit, and ?rn represents the average Abbe number of materials of negative lenses in the rear lens subunit.

Abstract: A zoom lens system including, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power; an aperture stop; and a fourth lens unit having a positive refractive power and including a front lens subunit and a rear lens subunit in which Abbe numbers of lenses in the rear lens subunit satisfy the following expression, 0.400<?m/(?rp??rn)<0.630, where ?m represents the Abbe number of the material of a first positive lens having the largest dispersion of the positive lenses included in the rear lens subunit, ?rp represents the average Abbe number of materials of positive lenses other than the first positive lens in the rear lens subunit, and ?rn represents the average Abbe number of materials of negative lenses in the rear lens subunit.

Abstract: An image pickup optical system including: a first prism including: a first incident surface where subject beam enters; a division surface for dividing the beam from the first incident surface into image-pickup beam and focus-detection beam; and a first exit surface from which reflection beam reflected on the division surface, the image-pickup beam or the focus-detection beam, exits; and a second prism including: a second incident surface on which transmission beam passing through the division surface, the image-pickup beam or focus-detection beam, enters; and a second exit surface from which the transmission beam exits, wherein the reflection beam is reflected on the division surface, reflected on the first incident surface, and reflected on the division surface to reach the first exit surface, and satisfying 0.1<DA/DB<0.5, where DA and DB indicate beam diameters of beams toward the image pickup elements for focus detection and for image pickup.