An objective lens of large relative aperture comprising, from front to rear, a first lens component of positive power, a second lens component of positive power and a third lens component of negative power, the first and third lens components being moved forward as a unit, while the second lens component is simultaneously moved forward by a smaller amount than that of the movement of them to effect focusing from infinity to shorter object distances. The focal lengths of the first, second and third lens components, the calculations of the constituent lenses, and the glass materials of which the lenses are made up are properly chosen so as to achieve a high grade imaging performance throughout a focusing range from infinity to very short object distances.
A lens system enabling close distance photographing has an excellent image forming performance for a wide focussing range from infinite distance to equi-magnification distance while employing a relatively simple lens composition. The lens system has a basic composition including a 1st group of positive refractive power, a 2nd group of positive refractive power and a 3rd group of negative refractive power arranged in this order from the object side and in focussing from infinite distance to closest distance, the 1st group and the 2nd group move to the object side away from the 3rd group, which is fixed relative to the image plane, while expanding the space between the 1st and the 2nd groups, the 3rd negative group has a positive lens and a negative lens arranged in this order from the object side.
A lens system comprising a front lens group consisting of a first, second and third lens components respectively of positive meniscus lenses with the convex surfaces on the object side and a fourth lens component of a negative meniscus lens and a rear lens group consisting of a fifth lens component of a positive or negative cemented meniscus lens with the convex surfaces on the image side and a sixth lens component of a positive lens. In this lens system, the entire lens system is moved along an optical axis to focus and an airspace between the fourth and fifth lens component and an airspace between the fifth and sixth lens components are respectively varied non-linearly to correct the collapse of aberrations. The front lens group may consist of a first lens component of a positive lens, a second lens component of a negative lens and a third lens component of a positive lens and the rear lens group may consist of a fourth lens component of a negative lens and a fifth lens component of a positive lens. In this case, an airspace between the third and fourth lens components and an airspace between the fourth and fifth lens components are respectively varied non-linearly to correct the collapse of aberrations.
A standard lens system composed, in order from the object side, of a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power: the first lens unit being composed of at least one positive meniscus lens component which has a convex surface on the object side, and at least one doublet which consists of a positive meniscus lens component and a negative lens component; the second lens unit being composed of at least one cemented doublet which consists of a negative lens element and a positive lens element, and a positive lens component; and the third lens unit being composed of at least one positive lens component and a negative lens component or at least one negative lens component.
A camera lens barrel for a camera includes first, second, third and fourth lens groups with a diaphragm located between the second and third lens groups. The second and third lens groups are connected, while the first, third and fourth lens groups can move relative to each other along the optical axis of the camera lens barrel. A diaphragm driver is positioned radially outside of the second lens group, while a lens shift driver device, including the horizontal and vertical lens shift drivers, is positioned radially outside of the third lens group. The diaphragm driver and the lens shift driver device are connected to a control unit via a flexible printed circuit. A power transmission extends from the diaphragm driver to the fourth lens group. The power transmission is connected to the diaphragm driver via a pin. When the pin is rotated, the angular rotation of a pin is transmitted to the fourth lens group to focus the camera lens barrel. Thus, the overall diameter of the camera lens barrel is reduced.
A zoom lens comprises a plurality of lens elements arranged into three lens units. More specifically, there is a first lens unit of positive refractive power, a second lens unit of negative refractive power, and a third lens unit of positive refractive power. The third lens unit is located between the first and the second lens units. The plurality of lens elements provide: (i) a zoom ratio greater than 1.5, (ii) an F/number in the telephoto position of less than F/5 and an F/number in the wide angle position of less than F/3.6, (iii) and an overall compactness ratio L.sub.v /f.sub.t <1.0, where L.sub.v is the distance from a front vertex of the zoom lens to the image plane in a telephoto position, and f.sub.t is the focal length of the zoom lens in the telephoto position.
