Fuji Photo Optical Co., Ltd.

Fujinon Corporation

Other

Satoshi Yahagi

Tadashi Sasaki

Tetsuya Ori

Fumio Watanabe

Masao Wada

Masayuki Sugawara

Akiko Takatsuki

Hideaki Sugiura

Haruo Tominaga

Takami Hasegawa

Takashi Tanaka

Koshi Kuwakino

Shinobu Nakamura

Ryoji Kumaki

Tetsuji Inoue

Hiroyuki Horiguchi

An autofocus adapter is provided and includes an imaging adapter optical system placed on an optical axis of an imaging lens when the autofocus adapter is attached, and a focus state detection adapter optical system placed on an optical axis different from the optical axis of the imaging lens when the autofocus adapter is attached. The imaging adapter optical system has a light split prism for splitting subject light passing through the imaging lens into imaging subject light and the focus state detection subject light, a first lens group having a negative power as a whole and placed on the object side with respect to the light split prism, and a second lens group having a positive power as a whole and placed on the image side with respect to the light split prism. The focus state detection adapter optical system has a positive lens group having the same lens configuration as the second lens group in the imaging adapter optical system.

Autofocus adapter

The present invention provides a visible and infrared light photographing lens system. A color separating prism or the like divides an object light entering a photographing lens and then passing through a focus lens, into an object light in a visible light region and an object light in an infrared light region. A visible light image pickup element and an infrared light image pickup element are used to pick up images of the respective object lights. Further, a compensation lens can be used to adjust a position where an image of the object light in the infrared light region is formed. Consequently, visible light photographing and infrared light photographing can be simultaneously carried out by focusing on an object at the same distance.

Visible and infrared light photographing lens system

A focus detecting system for determining the focus state of an imaging lens, such as a camera lens, is disclosed. Object light not forming an image for image production is deflected along an optical axis through a relay lens to a focus state detection unit that includes image detecting elements with light receiving surfaces that are equidistant in front of and behind a position conjugate with a light receiving surface for image production. Either the relay lens or the focus state detection unit is moveable along the optical axis to vary how far the light receiving surfaces are out of focus. A diaphragm opening of the imaging lens determines if and by how much the relay lens and focus state detection unit are relatively moved. Evaluation values of the out of focus amount are compared in order to control focusing of the imaging lens.

Focus detecting system

The focusing state determining adapter is detachably mounted between an interchangeable taking lens and a camera body in a camera system. The focusing state determining adapter includes a focus-imaging element and a beam splitter, which divides the subject light entering through the taking lens into light entering the focus-imaging element and light entering the camera body. The focusing state determining adapter determines the focusing state of the taking lens according to an image captured by the focus-imaging element.

Focusing state determining adapter for taking lens

A beam splitter ( )for splitting light in a wavelength range of about 500 nm to about 600 nm is arranged in a relay optical system of a taking lens ( ). A green light beam reflected from the beam splitter ( ) is directed through a relay lens (R ) to a focusing state determination imaging unit ( ). The imaging unit ( ) comprises three imaging elements (A, B, C) for capturing the directed green light beam to determine the focusing state. Thus, a device for determining the focusing state of the taking lens is provided, in which the green light beam is separated as an object light for determining the focusing state from the object light entering the taking lens ( ), so that the focusing state can be determined with high accuracy on the basis of the high-frequency components of the image signal generated by capturing the green light beam by means of the imaging elements (A, B, C) having different optical path lengths.

Device for determining focused state of taking lens

An autofocus system for an imaging device that includes an image detecting element for image production at a focused image plane of an adjustable focus imaging lens that also includes four image detecting elements for focus detection arranged in pairs that are equidistant in front of, and behind, planes that are conjugate with the focused image plane. One pair of image detecting elements for focus detection are farther than the other pair from the conjugate planes and may be used alone for focusing based on the stop value or focal length of the adjustable focus imaging lens. Alternatively, the other pair of image detecting elements may be used for more accurate focusing after the one pair of image detecting elements is used. The use of two pairs of image detecting elements at different distances from the focused image plane provides accurate focusing over a wide range of object distances.

Autofocus system

An imaging optical system includes at least one ghost image prevention element. Ghost images are prevented even when the imaging optical system includes an optical element that has at least one planar surface that is generally orthogonal to an optical axis of the imaging optical system, and is located in a light flux area with at least a central portion of the light flux area being generally parallel to the optical axis. The ghost image prevention element is especially useful in video cameras and digital cameras that use an image sensor having a planar surface that exhibits a high coefficient of reflection. The ghost image prevention element includes one planar surface, that is &ldquo;tightly bound&rdquo; to the planar surface of the optical element, and another surface that is curved so as to satisfy a given condition. The curved surface diffuses light that would otherwise contribute to a ghost image.

Ghost image prevention element for imaging optical system

A zoom lens having both manual mode and auto focus mode of focus adjustment. The zoom lens includes, in order from the object side, a focus portion, a zoom portion, and a main portion. Zooming is accomplished by moving some or all of the lens elements in the zoom portion along the optical axis. What would otherwise be a fluctuation of the image surface with change of object distance is corrected in manual mode by manually moving some or all of the lens elements of the focus portion along the optical axis based on visual observation of the object through the zoom lens as the adjustment is made. In auto focus mode, what would otherwise be a fluctuation of the image surface with change of object distance is corrected by micro-vibrating some or all of the lens elements of a lens group in the light path following the focus portion. A signal that varies according to image quality variations caused by this micro-vibration is detected and the detected signal is used to automatically control the position of those lens elements in the focus portion that are manually moved in order to adjust focus in manual mode. At least one surface a lens element that is micro-vibrated in auto focus mode is aspherical, and at least one surface of a lens element that is micro-vibrated in auto focus mode includes a diffractive optical element having diffraction zones formed thereon.

Zoom lens

A zoom lens having only five lens groups of positive, negative, negative, positive and positive refractive power, respectively, in order from the object side. The focal distance is varied by shifting the second and third lens groups, in order from the object side, along the optical axis, and a middle sub-assembly in the first lens group is shifted along the optical axis in order to correct for what otherwise would be a shifting in the image plane as the distance to the object is varied. The first lens group is formed of three sub-assemblies, with the sub-assembly nearest the object side having negative refractive power and being fixed in position, the middle sub-assembly having positive refractive power and shifting as discussed above, and the sub-assembly nearest the image-side having positive refractive power and being fixed in position. The second lens group, in order from the object side, is formed of two sub-assemblies having negative and positive refractive power, respectively, and the spacing between these two sub-assemblies is varied with a change in focal distance in order to correct for aberrations. Preferably, one or more lens element surfaces in the second lens group is aspherical.

Zoom lens for television camera

A compact zoom lens having only four lens groups is provided which changes power by shifting a second lens group from the object side along the optical axis, and stabilizes the image plane position by shifting a fourth lens group from the object side along the optical axis. By satisfying three prescribed conditions, magnification of the image is prevented from decreasing for objects at very near distances, and aberrations are favorably corrected so as to provide for high quality imaging over the entire range of zoom for all object distances. At least one lens element has an aspherical surface.

An inexpensive, high performance zoom lens includes, as measured from the object side, a negative first lens group and a positive second lens group. The overall length of the zoom lens is reduced by making one of the lens element surfaces of the first lens group G.sub.1 aspherical. A lens element in the second lens group is designed to be a biconvex lens with the same absolute value of radii of curvature, to thereby make the zoom lens inexpensive to produce and assemble.

Two-group small zoom lens

A second lens group is divided into a negative second A lens group and a positive second B lens group, and the distance between the second A and B lens groups is made variable so as to correct a fluctuation in aberration caused by a change in focal length, thereby reducing the size and weight of the whole lens system, while the fluctuation in performance is kept low in the whole zoom range and whole focus range. The second lens group is constituted by the second A lens group having a negative refracting power and the second B lens group having a positive refracting power. Upon a change in focal length, the distance between the second A and B lens groups is altered so as to suppress the fluctuation in aberration mainly in a middle range. Namely, in the second lens group having the highest refracting power, a surface spacing highly sensitive to the change in aberration is altered, whereby the aberration can be corrected with a favorable balance. Specifically, as indicated by the moving loci in FIG. 1, during the movement from the wide angle end to the telephoto end, the second A and second B lens groups are moved such that the distance therebetween is narrowed in the middle range.

A zoom lens comprising five lens groups is configured such that the total moving amount of the second lens group from the wide angle end to the telephotographic end is changed according to the object distance and that the fourth lens group is moved so as to correct zooming and focusing, whereby the imaging magnification is prevented from decreasing at the time of zooming even when the object distance changes. It comprises five lens groups respectively having positive, negative, negative, positive, and positive refractive powers. At the time of zooming, the first, third, and fifth lens groups (G1, G3, and G5) are fixed, while the second and fourth lens groups (G2 and G4) are made movable. The second lens group (G2) is moved in the optical axis direction so as to change the focal length of the whole system, while the fourth lens group (G4) is moved in the optical axis direction to correct fluctuation in the imaging position and to correct change in the imaging position caused by change in the object distance. The moving amount of the second lens group (G2) at the time of zooming is made larger when the object is placed at a close telephotographic position than when the object distance is at an infinite telephotographic position.

In five constituent lens groups, the fourth lens group from the object side is made as a negative lens. This fourth lens group is moved in order to correct zooming and focusing, while predetermined conditional expressions are satisfied, thereby yielding a zoom lens which can attain a wide angle, a large zoom ratio, and favorable aberrations. This zoom lens has five groups respectively composed of positive, negative, positive, negative, and positive lens groups. At the time of zooming, the first, third, and fifth lens groups G1, G3, and G5 are fixed, while the second and fourth lens groups G2 and G4 are made movable. As the second lens group G2 is moved in the optical axis direction, the focal length of the whole system is changed. As the fourth lens group G4 is moved in the optical axis direction, fluctuation in imaging position is corrected while change in the imaging position due to change in object distance is corrected. This zoom lens is further configured so as to satisfy the following conditional expressions (1) to (3):

A zoom lens system includes first to fifth lens groups arranged in this order from the object side. The first, third and fifth lens groups are fixed. The second lens group is moved in the direction of the optical axis of the zoom lens system when zooming the zoom lens system and the fourth lens group is moved in the direction of the optical axis to correct change in the image position due to the zooming and to correct change in the image position due to change in the object distance. The first lens group has a positive refracting power, the second lens group has a negative refracting power, the third lens group has a negative refracting power, the fourth lens group has a positive refracting power and the fifth lens group has a positive refracting power.

Growing community of inventors

Fuchu, Japan

Satoshi Yahagi