A lens system is provided. The lens system includes a positive first lens group, an aperture diaphragm, a positive second lens group, and a third lens group, disposed sequentially from a subject side. The first lens group includes at least three positive lenses and at least one negative lens. The second lens group includes four or more lenses including at least one cemented lens. A negative lens with a concave surface toward the subject side is disposed at the subject side. The third lens group includes three or more lenses including at least one positive lens and at least one negative lens. When focusing is moving from an infinity-distance subject to a short-distance subject, the first lens group, the aperture diaphragm, and the second lens group move integrally toward the subject side, while the third lens group is fixed with respect to an image surface.

A zoom lens includes in order from an object side, a negative first lens unit and a rear lens unit including one or more lens units, an interval between adjacent lens units being changed during zooming, in which the first lens unit and the one or more lens units can be set to first, second and third zoom states, in which angles of view at first and second image heights at the first zoom state are respectively 160° or larger, in which a distortion at the first image height at the third zoom state is −30% or more, and the first image height, the second image height, a total length of the zoom lens at a wide angle end, and a focal length at the wide angle end are appropriately set.

There is provided a lens system composed, in order from an enlargement side, of a first lens group with positive refractive power and a second lens group with positive refractive power, wherein when zooming from a telephoto end to a wide-angle end, a distance between the first lens group and the second lens group decreases and a distance between the second lens group and a conjugate plane on a reduction side increases. The second lens group includes, closest to an enlargement side thereof, a lens with a second end surface that is concave on the enlargement side, and the first lens group includes a lens with an effective diameter of a first end surface closest to the reduction side that is larger than a maximum diameter in the second lens group.

The imaging lens includes, successively in order from a position closest to an object side, a first lens group that has a positive refractive power and a second lens group that has a negative refractive power. During focusing, only the second lens group moves. The first lens group consists of a first A group, an aperture stop, and a first B group, in order from the object side. The second lens group includes at least one positive lens. The imaging lens satisfies predetermined conditional expressions.

A telephoto optical imaging system and zoom camera apparatus. The telephoto optical imaging system includes, sequentially from an object side to an image side along an optical axis, a first lens having positive refractive power, a second lens having negative refractive power, an optical path turning prism, and a triangular prism. Distance T from the object-side surface of the first lens to an imaging plane of the telephoto optical imaging system in a normal direction of the imaging plane and the total effective focal length F1 of the telephoto optical imaging system satisfy T/F1<0.6. The zoom camera apparatus includes the telephoto optical imaging system and a short-focus optical imaging system arranged in parallel with the telephoto optical imaging system. A total effective focal length F1 of the telephoto optical imaging system and a total effective focal length F2 of the short-focus optical imaging system satisfy F1/F2>5.

A zoom optical system (ZL) comprises, in order from an object: a first lens group (G1) having a positive refractive power; and a second lens group (G2) having a negative refractive power, wherein upon zooming, a distance between the adjacent lens groups changes. The zoom optical system further comprises an aperture stop (S) disposed closer to an image than the second lens group (G2, and satisfies the following conditional expression:

0.10<Df/Dr<0.90 where Df: a distance to the aperture stop from a lens surface of the zoom optical system closest to an object in a wide angle end state, and Dr: a distance from the aperture stop to a lens surface of the zoom optical system closest to the image in the wide angle end state.

The present invention relates to a reflective eyepiece optical system and a head-mounted near-to-eye display device. The system includes: a first lens group, a first optical element and a second lens group for transmitting and reflecting light from a miniature image displayer; the second lens group includes an optical reflection surface, and the optical reflection surface is the optical surface farthest from a human eye viewing side in the second lens group; the optical reflection surface is concave to human eyes; the first optical element reflects the light refracted by the first lens group to the second lens group, and then transmits the light refracted, reflected and again refracted by the second lens group to the human eyes.

The disclosure provides a combined zoom dual-camera lens assembly, which includes a first lens group and a second lens group, wherein a field of view of the second lens group is larger than a field of view of the first lens group, and a thickness of the second lens group is smaller than a thickness of the first lens group; and a total effective focal length f.sub.T of the first lens group and a total effective focal length f.sub.W of the second lens group meet f.sub.T/f.sub.W>9.00.

Pop-out lens systems for compact digital cameras, comprising an image sensor and a lens with a field of view FOV>60 deg and having i lens elements L1-Li starting with L1 from an object side toward an image side, each lens element Li having a respective focal length f.sub.i, the lens elements divided into two lens groups G1 and G2 separated by a big gap (BG), the lens having a pop-out total track length TTL<20 mm in a pop-out state and a collapsed total track length c-TTL in a collapsed state, wherein BG>0.25×TTL, wherein either G1 can move relative to G2 and to the image sensor for focusing or G1 and G2 can move together relative to the image sensor for focusing, and wherein a ratio c-TTL/TTL<0.7.

An infinity-corrected microscope objective lens has, arranged in order from the object side along an optical axis, a first lens group having a positive refractive power, and a second lens group having a positive refractive power, an intermediate image forming plane in which light from an object forms an image being positioned between the first lens group and the second lens group, and the microscope objective lens satisfying the condition below. −0.2<f×NA/TL <0.05, where f is the focal length of the microscope objective lens, NA is the object-side numerical aperture of the microscope objective lens, and TL is the distance on the optical axis from the lens surface of the microscope objective lens on the side thereof closest to the object to the lens surface of the microscope objective lens on the side thereof closest to the image.