Nikon Corporation

Keiji Moriyama

Kenzaburo Suzuki

Hiroshi Ohki

Masahiro Nakatsuji

An ocular optical system for a viewfinder in a camera for observing object image which is formed on focusing glass or its vicinity via eye point. The ocular optical system includes, in order from the focusing glass side, a negative meniscus lens, which has its convex surface facing the focusing glass side, and a positive lens. Visibility compensation is performed by moving the positive lens along the optical axis without moving the negative meniscus lens.

Ocular optical system for a viewfinder with variable visibility

A compact focus state detection device having a plurality of focus state detection areas at the center of and away from the center of the photo field. A first focus state detection optical system has focus state detection areas away from the center of the photo field and in a direction substantially perpendicular to the radial direction from the center point. The optical axis of each re-imaging lens of the first focus state detection optical system is decentered toward the optical axis of the shooting lens from the center of each corresponding aperture stop. Therefore, when focus state detection light rays pass through the re-imaging lens, the exit direction of the light rays deflects toward the optical axis of the shooting lens.

Focus state detection device

A focus state detection device includes a field mask aperture having a shape created from the overlapping portions of two areas. The first area is formed by the outermost perimeter of the cross-section of light rays passing through the field mask plane toward each of the arrays of photoelectric conversion devices from each of point of the conjugal images of the arrays of photoelectric conversion devices at the primary imaging plane. The second area is formed by line segments that are the projection onto the field mask plane of the boundary lines at the surface of each re-imaging lens on the side toward the arrays of photoelectric conversion devices. The use of this shape causes light to be directed within the boundary lines of the outer perimeter of each of the re-imaging lenses. Through the use of this shape, the creation of stray light and internal reflection in the focus state detection optical system are suppressed, and stable focus state detection precision is enabled.

Focus state detection device and method

With a focus detection device equipped with focus detecting optical systems with focus detection areas both on and outside the optical axis of the photographic surface, a focus detection device suppresses vignetting of the focus detection light fluxes through incompatibilities with the exit pupil of the installed objective lens and has stable focus detection accuracy. With a focus detection device equipped with at least two focus detecting optical systems and on each focus detecting optical system, which forms the image that comes through the objective lens for each focus detecting optical system as a second image on a set of photoelectric transforming element arrays, and which carries out focus detection of the objective lens through relative position of the second image, reverse projections through the condenser lens of the diaphragm openings opposite the focus detecting optical systems with focus detection areas outside the optical axis of the photographic surface face toward the optical axis of the objective lens and cross the optical axis.

Focus detecting device

A zoom lens having a four-unit lens construction with positive, negative, positive, and positive refractive powers. In an embodiment, the second lens unit is moved toward the image side during the magnification change from the wide angle end to the telephoto end, and the third lens unit is moved in a direction substantially orthogonal to the optical axis to effect image stabilization. The zoom lens satisfies the condition that .DELTA.Y=f.sub.4 /f.sub.3 .multidot..DELTA.S. In another embodiment, the first, third, and fourth lens units are moved toward the object side during the magnification change from the wide angle end to the telephoto end, and the second lens unit is moved in a direction substantially orthogonal to the optical axis to effect image stabilization. The zoom lens satisfies the condition that .DELTA.Y=(1-.beta..sub.2).multidot..beta..sub.34 .multidot..DELTA.S.

Zoom lens equipped with the image stabilizing function

A focus detecting apparatus for detecting the focus of a photo-taking lens comprises a condenser lens disposed near the predetermined image plane of an object formed by the photo-taking lens, and a plurality of focus detection systems. Each of the focus detection systems comprises pupil dividing means disposed rearwardly of the condenser lens in the direction of the optical axis thereof and having at least one pair of openings for dividing the pupil of the photo-taking lens, at least one pair of re-imaging lenses disposed rearwardly of the pupil dividing means correspondingly to the at least one pair of openings for forming at least one pair of secondary images, and a photoelectric conversion element array having picture elements for detecting the amount of deviation of the relative position of the secondary images. The area of a picture element of the photoelectric conversion element array in each of the focus detection systems is determined in conformity with the area of the openings in the pupil dividing means in that focus detection system.

Focus detecting apparatus

A focusing detection apparatus has at least a focusing detection area on an optical axis of a photographing lens and a focusing detection area off the optical axis of the photographing lens in a photographing field and has a focusing detection optical system including at least a pair of apertures and a pair of refocusing lenses provided one set for each of the focusing detection areas. The focusing detection optical systems are arranged such that a positional relation between centers of the pair of aperture corresponding to the off-axis focusing detection area and optical axes of the pair of refocusing lenses is different from a positional relation between the centers of the pair of apertures corresponding to the on-axis focusing detection area and the optical axes of the pair of refocusing lenses.

Focusing detection apparatus

In a focus detecting apparatus provided with a focus detecting optical system comprising a field mask provided at the predetermined image plane position of a photo-taking lens and having an opening corresponding to a focus detection area, a condenser lens provided rearwardly of the field mask and positioned near the predetermined image plane of the photo-taking lens, a pair of stop masks provided rearwardly of the condenser lens and dividing the pupil of the photo-taking lens into two areas by a pair of openings therein, and a re-imaging lens system having a pair of re-imaging lenses corresponding to the openings in the stop mask, the image by the photo-taking lens being re-formed as secondary images on a pair of photoelectric conversion element arrays by the focus detecting optical system, the focus adjusted state of the photo-taking lens being detected from the relative positional relation between the secondary images, a plurality of focus detecting optical systems are disposed so that they have at least two focus detection areas about a position off the optical axis of the photo-taking lens and the directions of detection of these focus detection areas differ from each other, and the center positions of the pairs of openings in the stop masks of the focus detecting optical systems are set to different positions.

Focus detecting apparatus with multi-directional off axis detection areas

A focus detecting apparatus has a condenser lens provided near a primary image of an object formed through an objective lens, and a plurality of focus detecting optical systems, each detecting deviation between the relative positions of a pair of secondary images. Each focus detecting optical system has a pair of stop openings provided rearwardly of the condenser lens for dividing a marginal area of the exit pupil of the objective lens into a pair of divided pupil areas that are symmetrically disposed with respect to the optic axis of the objective lens. A pair of re-imaging lenses is disposed rearwardly of each pair of stop openings for forming a pair of secondary images. The directions of deviation of the pairs of secondary images differ from each other. The interval between the centers of the stop openings of each pair of stop openings is substantially the same for all the pairs of stop openings, but the radii of circles that circumscribe respective pairs of stop openings differ from each other.

Multidirectional divided-pupil focus detecting apparatus

A lens system capable of close-up photographing comprises, in succession from the object side, a first lens group having a positive refactive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power. The first lens group and the second lens group are moved relative from each other for focusing to infinity to a close distance so that the spacing between the first lens group and the second lens group is reduced and the spacing between the second lens group and the third lens group is enlarged. The first and second lens groups are designed to satisfy the following condition:

Lens system capable of close-up photographing

A focus state detecting optical system is provided with a condenser lens positioned in the vicinity of or behind a primary image formed by the light coming from an object and transmitted by an objective lens, pupil dividing means positioned behind the condenser lens and adapted for dividing the pupil of the condenser lens symmetrically with respect to the optical axis, and re-imaging lenses positioned parallel to and corresponding to thus divided pupils and symmetrically with respect to the optical axis thereby forming secondary images, wherein the focus state is detected from the relative positional aberration of said secondary images. Each of the re-imaging lenses is composed of a positive lens with two convex faces of which at least one is an aspherical shape.

Optical system for focus state detection

A telephoto zoom lens comprising, in succession from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, the lens groups being moved independently of each other during zooming. The telephoto zoom lens meets certain conditions, including a condition that prescribes the amount of change in spacing between the first and second lens groups by zooming, so that the spacing increases at the telephoto end. The telephoto ratio is large, and the lens is relatively compact at the wide angle end. The burden borne by each lens group regarding correction of spherical aberration is reduced, and correction of spherical aberration is relatively easy, so that the degree of freedom in lens design is enhanced.

Growing community of inventors

Yokohama, Japan

Keiji Moriyama