Abstract: A zoom optical system capable of selecting different focusing methods is disclosed. This zoom optical system includes a variable power unit that performs a variable power operation while moving during zooming; a first focusing unit positioned in front of the variable power unit; a second focusing unit positioned at the back of the variable power unit; a sensor that detects the position of the first focusing unit; and a memory that stores movement information of the second focusing unit during zooming according to the position of the first focusing unit. Herein, the second focusing unit changes in the moving locus thereof during zooming, based on the position information about the first focusing unit detected by the sensor and the information from the memory.

Abstract: A zoom optical system capable of selecting different focusing methods is disclosed. This zoom optical system includes a variable power unit that performs a variable power operation while moving during zooming; a first focusing unit positioned in front of the variable power unit; a second focusing unit positioned at the back of the variable power unit; a sensor that detects the position of the first focusing unit; and a memory that stores movement information of the second focusing unit during zooming according to the position of the first focusing unit. Herein, the second focusing unit changes in the moving locus thereof during zooming, based on the position information about the first focusing unit detected by the sensor and the information from the memory.

Abstract: A zoom lens of the rear focus type is disclosed, whose back focal distance is increased to accommodate a three-color separation prism and other optical elements, comprising, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, the second lens unit and the fourth lens unit being moved to effect zooming and the fourth lens unit being moved to effect focusing, wherein the third lens unit has a negative lens disposed closest to the object side and having a concave surface facing the object side and has a positive lens disposed closest to the image side, and a lens surface on the image side of the positive lens has a refractive power which is stronger than that of a lens surface on the object side of the positive lens.

Abstract: A zoom lens of the rear focus type is disclosed, whose back focal distance is increased to accommodate a three-color separation prism and other optical elements, comprising, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, the second lens unit and the fourth lens unit being moved to effect zooming and the fourth lens unit being moved to effect focusing, wherein the third lens unit has a negative lens disposed closest to the object side and having a concave surface facing the object side and has a positive lens disposed closest to the image side, and a lens surface on the image side of the positive lens has a refractive power which is stronger than that of a lens surface on the object side of the positive lens.

Abstract: A zoom lens includes, from front to rear, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power and a fourth lens unit having a positive refractive power, at least the second and fourth lens units being moved to effect zooming, wherein the maximum image angle is increased while the diameter of the first lens unit is extremely reduced.

Abstract: A zoom lens of the rear focus type including, from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power having a stop, and a fourth lens unit of positive refractive power. During zooming from a wide-angle end to a telephoto end, the second lens unit is moved toward the image side, the third lens unit and the stop are moved in unison in a locus convex toward the object side, and the fourth lens unit is moved in a locus convex toward the object side. During focusing, the fourth lens unit is moved, and the following condition is satisfied: -0.3<M3max/.phi..sub.1 <-0.04, where M3max is a maximum value of an amount of axial movement of the third lens unit and the stop from the wide-angle end (a moving direction to the object side being taken as "-"), and .phi..sub.1 is the outer diameter of a frontmost lens of the zoom lens.

Abstract: A zoom lens includes, from front to rear, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power and a fourth lens unit having a positive refractive power, at least the second and fourth lens units being moved to effect zooming, wherein the maximum image angle is increased while the diameter of the first lens unit is extremely reduced.

Abstract: A zoom lens of the rear focus type comprising, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, wherein the second lens unit and the fourth lens unit are moved to effect zooming and the fourth lens unit is moved to effect focusing, wherein the third lens unit includes a positive first lens and a negative second lens of meniscus form convex toward the image side, and the fourth lens unit includes a negative first lens of meniscus form convex toward the object side and a positive second lens, and wherein an aspheric surface is applied to the third lens unit or the fourth lens unit.

Abstract: A rear focus type zoom lens including, in succession from the object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power having a stop, the third lens unit having at least two positive lenses and a negative lens which is most adjacent to the image plane side, and a fourth lens unit of positive refractive power consisting of a positive lens and a negative lens, the second lens unit and the fourth lens unit being moved to effect zooming, the fourth lens unit being moved to effect focusing.

Abstract: A focus detecting device is disclosed including an image sensor, a phase control plate for causing image forming positions of light incident on a plurality of areas in an imaging plane of the image sensor to differ from each other, and a focus detecting circuit for computing the image signals corresponding to the plurality of areas of which the image forming positions are different to detect a focusing state. A solid-state image sensor is also disclosed including a plurality of photoelectric conversion element rows and a phase control plate positioned on a photoelectric conversion plane of the photoelectric conversion element rows to cause image forming positions of incident light to differ at intervals of integer times the interval in the photoelectric conversion element rows.

Abstract: A zoom lens comprising a first lens group having a positive refractive power; a second lens group having a negative refractive power that moves for zooming; a third lens group movable to correct image surface movement; and a fourth lens group stationary during zooming. The fourth lens group consists of six lenses. The first lens reduces divergence of a light beam. Further, if the overall focal length of the system at the wideangle end is F.sub.W ; the focal length of the second lens group is F.sub.2 ; the focal length of the combination of the second to sixth lenses is F.sub.42 ; and the focal length of the combination of the second to fourth lenses is F.sub.A, then the conditions: ##EQU1## are satisfied.

Abstract: A zoom lens comprising a first lens unit of positive power, a second lens unit of negative power as the variator, a third lens unit of negative power as the compensator, and a fourth lens unit of positive power stationary during zooming, the fourth lens unit being composed of a bi-convex first lens, a positive second lens, a negative third lens of strong concave curvature at the front, a positive fourth lens, a fifth lens of strong concave curvature at the rear, and a positive sixth lens, and satisfying the following condition:0.5<D/Fw<1.5where D is the air separation between the fourth and fifth lenses, and Fw is the shortest focal length of the entire lens system.

Abstract: A zoom lens comprising, from front to rear, a first group of positive power for focusing, a second group of negative power for varying the image magnification, a third group of negative power for compensating for the image shift, a fourth lens group of positive power in the form of a bi-convex lens whose rear surface is stronger in curvature than the front surface, a stop, and an image forming fifth group, the fifth groug being divided into two parts of which the front part comprises a bi-convex first lens, a negative second lens having a concave front surface and a positive third lens of stronger front curvature and the rear part comprises a negative fourth lens having a concave rear surface, a bi-convex fifth lens and a positive sixth lens of stronger front curvature, and the zoom lens satisfying the following conditions:3.9<f4/fw<4.53.8<f51/fw<4.21.05<R5,2/R5,3<1.21.25<D51-52/fw<1.

Abstract: A zoom lens comprising, from front to rear, a positive first group for focusing, a negative second group as the variator, a negative third group as the compensator, a positive fourth group and a fifth group as the relay lens, the fourth group in the form of a bi-convex singlet and the fifth group in two parts with a widest spacing therebetween, of which the front part comprises a bi-convex first lens, a negative second lens whose front surface is concave toward front, and a positive third lens whose front surface is of strong curvature, and the rear part comprises a negative lens whose rear surface is concave toward rear, a bi-convex lens and a positive lens whose front surface is of strong curvature, satisfying the following conditions:3.9<f4/fw<4.53.7<f5F/fw<5.21.0<R5,2/R5,3<1.61.4<(D5F-D5R)/fw<1.

Abstract: A zoom lens comprising a positive first lens unit for focusing, a negative second lens unit as the variator, a negative third lens unit as the compensator, a positive fourth lens unit for making afocal the diverging light beam from the third unit in travelling thereacross, and an image forming or fifth lens unit having six lenses, satisfying the following conditions:0.7<.vertline.R.sub.4,2 /F.sub.4 .vertline.<0.851.05<.vertline.f.sub.5,2 /F.sub.5 .vertline.<1.50.6<.vertline.f.sub.5,4 /f.sub.5,5 .vertline.<1.550<(.nu..sub.5,1 +.nu..sub.5,6)/2 59where R.sub.4,2 is the radius of curvature of the second surface counting from front of the fourth lens unit, F.sub.4 and F.sub.5 are the focal lengths of the fourth and fifth lens units respectively; f.sub.5,2, f.sub.5,4, and f.sub.5,5 are the focal lengths of the second, fourth and fifth lenses in the fifth lens unit, and .nu..sub.5,1 and .nu..sub.

Abstract: A zoom lens comprising, from front to rear, a first lens unit of positive power for focusing, a second lens unit of negative power as the variator, a third lens unit of negative power as the compensator, an afocal fourth lens of positive power, and a fifth lens unit for image formation, the fifth lens unit including, from front to rear, a bi-convex first lens whose front surface is of stronger curvature, a negative meniscus second lens of forward concavity, a positive third lens whose front surface is of stronger curvature, a negative meniscus fourth lens of forward convexity, a bi-convex fifth lens whose rear surface is of stronger curvature, and a positive sixth lens whose front surface is of stronger curvature, wherein the following conditions are satisfied:1.45<F.sub.1 /F.sub.4 <1.652.5<F.sub.4 /Fw<2.80.75<.vertline.f.sub.5,4 /F.sub.5 .vertline.<1.30.47<D.sub.5,6 /F.sub.5 <0.65where F.sub.1, F.sub.4 and F.sub.

Abstract: A zoom lens comprising, from front to rear, a first lens component for focusing having a positive refractive power, a second lens component for variation of the image magnification having a negative refractive power, a third lens component for compensation to move in unison with the second lens component, and a rear lens part having a positive refractive power, wherein the first lens component includes, from front to rear, a cemented lens I.sub.1 of two elements of negative and positive powers and a meniscus-shaped lens I.sub.2 of forward convexity having a positive refractive power, and the zoom lens satisfies the following conditions:0.095<.vertline..beta..sub.IIW .multidot..beta..sub.IIIW .vertline./.sqroot.Z<0.106where .beta..sub.IIW <0, .beta..sub.IIIW >0,2.15<.vertline.F.sub.I1 /F.sub.I2 .vertline.<2.8where .beta..sub.IIW and .beta..sub.IIIW are the magnifications of the second and the third lens components respectively, Z is the zoom ratio, and F.sub.I1 and F.sub.