Abstract: From an object, a first lens that is a meniscus lens having a convex surface that faces an object, a second lens that faces a concave surface of the first lens, a third lens having a concave surface that faces the second lens, and a fourth lens that is a positive lens having a convex back surface, (1) ?3<?4, (2) 0.5<Ymax/f<0.8, and (3) ?d<1.5 f are satisfied, where ?3 is an Abbe number of the third lens, ?4 is an Abbe number of the fourth lens, Ymax is a maximum height of an image, f is a composite focal length, ?d is a distance between a first surface of the first lens and a second surface of the fourth lens, the first surface facing the object and the second surface facing an imaging plane, any one surface of the first lens and the fourth lens having a non-spherical surface.

Abstract: From an object, a first lens that is a meniscus lens having a convex surface that faces an object, a second lens that faces a concave surface of the first lens, a third lens having a concave surface that faces the second lens, and a fourth lens that is a positive lens having a convex back surface, (1) ?3<?4, (2) 0.5<Ymax/f<0.8, and (3) ?d<1.5f are satisfied, where ?3 is an Abbe number of the third lens, ?4 is an Abbe number of the fourth lens, Ymax is a maximum height of an image, f is a composite focal length, ?d is a distance between a first surface of the first lens and a second surface of the fourth lens, the first surface facing the object and the second surface facing an imaging plane, any one surface of the first lens and the fourth lens having a non-spherical surface.

Abstract: A zoom lens system of a relatively high zoom ratio about 2.5 to 3.5 ranging to a wide field angle such as 76 degrees is disclosed. The zoom lens system comprises, from the object to the image side, a first movable negative lens group, a second movable positive lens group, a third stationary negative lens group and a fourth movable positive lens group with a first to third variable air spaces formed therebetween, respectively.

Abstract: An automatic focusing device which compises a defocus amount detecting unit for detecting a defocus amount attributable to a first optical system of an interchangeable lens assembly and a second optical system of an AF convertor, a converting circuit for converting the defocus amount into a data corresponding to a focusing amount of the second optical system which varies in non-linear relationship to the defocus amount, and an optical drive unit for moving the second optical system on the basis of a data representative of the focusing amount supplied from the converting circuit.

Abstract: A zoom lens system of a relatively high zoom ratio about 2.5 to 3.5 ranging to a wide field angle such as 76 degrees is disclosed. The zoom lens system comprises, from the object to the image side, a first movable negative lens group, a second movable positive lens group, a third stationary negative lens group and a fourth movable positive lens group with a first to third variable air spaces formed therebetween, respectively.

Abstract: An automatic focusing device which comprises a defocus amount detecting unit for detecting a defocus amount attributable to a first optical system of an interchangeable lens assembly and a second optical system of an AF convertor, a converting circuit for converting the defocus amount into a data corresponding to a focusing amount of the second optical system which varies in non-linear relationship to the defocus amount, and an optical drive unit for moving the second optical system on the basis of a data representative of the focusing amount supplied from the converting circuit.

Abstract: A zoom lens system of a relatively high zoom ratio about 2.5 to 3.5 ranging to a wide field angle such as 76 degrees is disclosed. The zoom lens system comprises, from the object to the image side, a first movable negative lens group, a second movable positive lens group, a third stationary negative lens group and a fourth movable positive lens group with a first to third variable air spaces formed therebetween, respectively.

Abstract: A two group zoom lens system of an inverted telephoto type is provided wherein a first lens group of a negative refractive power consisted of a first negative component and a second positive component of a positive meniscus lens convex to the object side; and a second lens group of a positive refractive power located with a variable air space between the first and second lens groups, consisting of third and fourth positive components, a fifth negative component, and a sixth positive component; wherein the shortest focal length of the whole lens system is less than the length of the diagonal line of the image plane; and wherein the lens system fulfills the following conditions;2.3 fs<l<2.75 fs0.55 fs<.gamma..sub.3 <1.8 fswherein,fs represents the shortest focal length of the whole lens system,l represents the axial distance between the object side surface of the first component and the image plane, and.gamma..sub.

Abstract: A zoom lens system of a relatively high zoom ratio ranging from a telephoto to a wide field angle is provided. The zoom lens system comprises from the object to the image side a first lens group of a positive refractive power, a second lens group of a negative refractive power consisting of a first negative subgroup, a second positive subgroup located on the image side of the first negative subgroup with an air space and a third negative subgroup located on the image side of the second positive subgroup with an air space, and a third lens group of a positive refractive power, wherein at least the air space between the first and second lens groups and the air space between the second and third lens groups are changeable upon zooming. The focusing can be practiced by moving the first lens group with the other lens groups left stationary.

Abstract: A compact catadioptric lens system with a widened field angle is disclosed and characterized in that the axial distance L between the main-mirror element (M.sub.1) and the sub-mirror element (M.sub.2) fulfills the following condition in relation to the diagonal length D of the rectangular focal plane on which the image is projected:1.5D>L>0.5D ,and that the radius of curvature R.sub.5 of the image side surface of the sub-mirror element and the radius of curvature R.sub.

Abstract: A conversion lens system to be attached to an objective lens system at the image side thereof for converting the focal length of the objective lens system into a greater value is provided. The conversion lens system has a negative focal length and comprises seven single lens elements consisting of a first negative meniscus lens element convex to the object side, a second biconvex lens element, a third biconcave lens element, a fourth biconvex lens element, a fifth negative lens element having a concave front surface, a sixth positive lens element having a convex rear surface and a seventh biconcave lens element. All of the seven lens elements may be separated from the others, or alternatively, at least two of the second to fourth lens elements may be cemented to each other.

Abstract: A variable soft focus lens system particularly adapted for photography is disclosed. The lens system incorporates two lens groups, a first object side lens group having an image side, rearmost surface convex to the image side, and a second, image side lens group having an object side, foremost surface concave to the object side. An airspace separating the first and second lens group has a meniscus shape concave to the object side. A good quality soft tone image having undersirable aberrations well within tolerable limits, is attained by shifting at least the second lens group along the optical axis relative to the first lens group whereby the airspace separating the two lens groups and a spherical aberration of the entire lens system is varied. An image does not lose proper focus while the spherical aberration of the system is varied. The second lens group has a refractive power within specified limits in relation to the refractive power of the entire lens system.

Abstract: A wide angle zoom lens system having a compact configuration is provided for use with 35 mm single lens reflex cameras. The zoom lens system includes two lens groups that can be relatively displaced along the optical axis to provide variation in focal length. The first lens group has a negative refractive power and the second lens group has a positive refractive power. A wide field angle is provided while minimizing the number of optical lens elements that constitute the two group zoom lens system.

Abstract: A zoom lens system consisting, from the object to the image side, of a positive front focusing lens group, a negative variator lens group, a negative compensator lens group and a relay lens group is provided. The variator lens group has three single lens elements, in which a negative meniscus shaped air space is formed between the second and third single lens elements. The relay lens group is divided into first and second sub-groups with a relatively wide air space formed therebetween, each of the first and second sub-groups has a pair of separate lens elements.

Abstract: A wide angle zoom lens system having a front lens group of a positive refractive power with an extended zoom ratio. A second lens group is located adjacent the first lens group and has sufficient negative refractive power so that the combined refractive power of the first and second lens group is negative. The first and second lens groups are movable as a fixed unit for a zooming operation in a first zoom range defined between the shortest focal length and a medium focal length. These same lens groups are separable for a zooming operation in a second zoom range between the medium focal length and the longest focal length.

Abstract: A telephoto lens system having improved focusing capabilities is provided wherein a first lens group of an overall positive refractive power is mounted on the object side of a second lens group of an overall negative refractive power. The lens components of the second lens group are capable of providing a simplified focusing mode of operation. The second lens group can comprise a first negative lens component and an image side second positive lens component. The second positive lens component is movably mounted for focusing the entire lens system on relatively close objects as its translates toward the object side. The first lens group is spaced a distance from the second lens group having an absolute value greater than 0.15f wherein f is the focal length of the entire lens system. Additionally, the composite absolute values of the focal lengths of the front lens group and the negative lens component of the second lens group is greater than 1.2f.