An optical imaging lens system includes four lens elements arranged along an optical axis. The optical imaging lens system satisfies the relations 2.13°≤HFOV/Fno≤8.75°; 3.85≤TTL/T1≤7.00; and 0.8≤AC34/T3, where a half field of view of the optical imaging lens system is defined as HFOV, an F number of the optical imaging lens system is defined as Fno, a distance measured from the object-side surface of the first lens element to an image plane along the optical axis is defined as TTL, a thickness of the first lens element along the optical axis is defined as T1, an air gap between the third and fourth lens elements along the optical axis is defined as AC34, a thickness of the third lens element along the optical axis is defined as T3.

An observation device according to the present invention includes an image display element displaying an image, and a finder optical system used for observing the image displayed on an image display surface of the image display element. The finder optical system includes a positive first lens, a negative second lens, and a biconvex positive third lens arranged in this order from the image display surface side to the observation side. A focal length of the second lens, a focal length of the finder optical system, a curvature radius of a lens surface of the second lens on the image display surface side, a curvature radius of a lens surface of the second lens on the observation side, a diagonal length of the image display surface, and a curvature radius of a lens surface of the third lens on the image display surface side are appropriately set.

An observation device according to the present invention includes an image display element displaying an image, and a finder optical system used for observing the image displayed on an image display surface of the image display element. The finder optical system includes a positive first lens, a negative second lens, and a biconvex positive third lens arranged in this order from the image display surface side to the observation side. A focal length of the second lens, a focal length of the finder optical system, a curvature radius of a lens surface of the second lens on the image display surface side, a curvature radius of a lens surface of the second lens on the observation side, a diagonal length of the image display surface, and a curvature radius of a lens surface of the third lens on the image display surface side are appropriately set.

A four-piece optical image capturing system. In order from an object side to an image side, the optical image capturing system along the optical axis includes a first lens with positive refractive power; a second lens with refractive power; a third lens with refractive power; and a fourth lens with refractive power; and at least one of the image-side surface and object-side surface of each of the four lenses are aspheric. The optical image capturing system can increase aperture value and improve the imagining quality for use in compact cameras.

A four-piece optical image capturing system. In order from an object side to an image side, the optical image capturing system along the optical axis includes a first lens with positive refractive power; a second lens with refractive power; a third lens with refractive power; and a fourth lens with refractive power; and at least one of the image-side surface and object-side surface of each of the four lenses are aspheric. The optical image capturing system can increase aperture value and improve the imagining quality for use in compact cameras.

A folded camera that includes two light folding elements such as prisms and an independent lens system, located between the two prisms, which includes an aperture stop and a lens stack. The lens system may be moved on one or more axes independently of the prisms to provide autofocus and/or optical image stabilization for the camera. The shapes, materials, and arrangements of the refractive lens elements in the lens stack may be selected to capture high resolution, high quality images while providing a sufficiently long back focal length to accommodate the second prism.

A folded camera that includes two light folding elements such as prisms and an independent lens system, located between the two prisms, which includes an aperture stop and a lens stack. The lens system may be moved on one or more axes independently of the prisms to provide autofocus and/or optical image stabilization for the camera. The shapes, materials, and arrangements of the refractive lens elements in the lens stack may be selected to capture high resolution, high quality images while providing a sufficiently long back focal length to accommodate the second prism.

An optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a first focus lens unit having a negative refractive power, and a second focus lens unit having a positive refractive power. The first lens unit is fixed during focusing. The first focus lens unit and the second focus lens unit move so that a distance between the first focus lens unit and the second focus lens unit changes during focusing. The first lens unit includes a single lens which is disposed closest to an object and has a negative refractive power. A predetermined condition is satisfied.

An optical imaging system includes a lens unit including at least three lenses; an image sensor that moves along an optical axis direction and receives light that has passed through the lens unit; and a reflective member disposed on an object side of the lens unit and having a reflective surface to change a path of light. The optical imaging system satisfies 0<(SAS/f)/OD<0.15, where SAS is a moving distance of the image sensor along the optical axis direction, f is a total focal length of the lens unit, and OD is an object distance.

An observation optical system includes a display element and an eyepiece lens arranged on an eyepoint side of the display element. The eyepiece lens consists of a first lens having positive refractive power, a second lens having negative refractive power, and a rear side lens group including two or more lenses consecutively in order from a side closest to the display element to the eyepoint side. In a case where a half value of a longest diameter of a display region in the display element is denoted by H, and a focal length of the eyepiece lens is denoted by f, the observation optical system satisfies a conditional expression represented by 0.3<H/f<0.5.