Abstract: An objective lens system of a quite simple construction with fewer lenses cyomplying with a continuous variation in thickness of the disk. The system records and reproduces information on a high-density and mass storage optical information medium while providing excellent performance. The system comprises a single positive lens element, a positive objective lens element and a disk arranged in that sequence from the side of a light source, in which the single positive lens is moved on an optical axis to improve the aberration that has increased as a result of a variation in thickness of the disk and the objective lens is moved by a slight distance on the optical axis to be in-focus state in response to the movement of the image point resulting from the variation in the thickness of the disk.

Abstract: A zoom lens including a wide angle and having a zoom ratio of approximately two, in which a two-group zoom composed of a negative front group and a positive rear group is increased in a refracting power to make both the two-group zoom compact. With this, correction of aberrations is difficult to make, and therefore, the positive rear group is separated into two components so that in zooming, different moving amounts may be imparted to the respective components. The zoom lens according to the present invention is composed, from the front side, a first negative unit, a second positive unit and a third positive unit, whereby in zooming, the first unit lens is first moved toward an image along an optical axis and then toward an object, the second unit lens is moved toward the object, and the third unit lens is likewise moved toward the object so as to gradually widen a space between the third unit and the second unit.

Abstract: This invention relates to a lens system which can convert a focal length by adding a converter lens. A rear converter lens having a positive refractive power is added between an image surface rearwardly of a standard or tele-lens system to obtain a wide angle lens. At this time, it is necessary to make the full length of the converter lens small and to prevent an increase in positive Petzval's sum of the converter lens and in negative distortion aberration. In this invention, in case of a wide angle lens, a rear converter lens is used which is composed of three to five lenses having an angle of view, 63.4.degree. and a magnification ratio, more than 1.4.

Abstract: This invention relates to a four-group-lens zoom lens which is small in size and has a high magnification changing rate of which zoom ratio is 4. The zoom lens comprises a magnification changing system in which a first group, a second group and a third group have positive, negative and positive refractive powers, respectively, and a fourth group in the form of a relay lens. It is advantageous to make the focal length of lenses in the first group small in order to miniaturize the magnification changing system. In addition, it is advantageous that the relay lens be made small in the focal length and made small in telephone ratio, in order to miniaturize the whole zoom lens.

Abstract: In a triplet photographic lens wherein a diaphragm is arranged forwardly of a lens, an asymmetry of arrangement with respect to the diaphragm has been remarkable to make it difficult to provide a wide angle.According to the present invention, principally a second lens L.sub.2 and a third lens L.sub.3 are bended so as to come closer to a centripetal shape about the diaphragm to make small the full length and a spacing between lenses thereby providing compensation of aberrations and increasing relative illumination, thus providing a wide angle lens having an angle of view of 70.degree..

Abstract: A small size zoom lens comprises a front and a rear group. The front group of lenses is of a diverging nature and includes three lenses disposed on an object side, while the rear group is of a converging nature and includes three lenses disposed on an image side. The lenses, from the object side, include a negative meniscus lens, having its convex surface directed toward the object side a negative lens having its concave surface directed toward the image side, a positive lens having its convex surface directed toward the object side, a positive lens, a positive meniscus lens having its convex surface directed toward the object side, a negative lens having its concave surface directed toward the image side, and a positive lens.From the object side, the radius of curvature of an i-th lens surface is represented as r.sub.i (i=1 to 14), the j-th axial separation between the lens surfaces as dj (j=1 to 13), the refractive index of each lens with respect to the d-line of the spectrum by n.sub.1, n.sub.2, . . . n.

Abstract: A wide angle zoom lens contains, in order from an object side, a first group having a negative focal length, a second group having a positive focal length and a third group having a negative focal length as well as a fourth and a fifth group each of which have a positive focal length. When the lens is moved to effect zooming from the side having a short focal length to a side having a long focal length either the first group is first moved toward the final image plane on an optical axis in a first movement phase and then moved toward the object in a second phase of movement or the first group is moved toward the image with each of the movements being executed in a non-linear fashion to correct variation of a focal length.

Abstract: Improvement in a small-size wide angle lens having a refractive power arrangement of so-called telephoto type, which has been demanded to meet the need of miniaturization of cameras. The lens of this type is composed of a front group having a positive refractive power and a rear group of negative meniscus lenses wherein a convex surface thereof is directed towards the image and greatly curved. In accordance with the present invention, there is provided a small-size wide angle lens wherein said rear group comprises two negative meniscus lenses, and the specific conditions are imposed on the lenses of said rear group to thereby make the aperture ratio small and provide well-corrected various aberrations, particularly, coma aberration.

Abstract: A camera lens system is disclosed having a long back focal distance and a large aperture ratio. This enables the camera system to sufficiently correct for various aberrations including the spherical aberration of colors of the camera lens system.

Abstract: A telephoto zoom lens comprises a first, a second, a third and a fourth group which are sequentially disposed beginning from an object side. The first group is a focusing lens group and remains stationary during a zooming operation, but is movable during a focusing operation and as a whole has a positive refractive power. The second group is a variator lens group and generally has a negative refractive power. The second group moves along the optical axis during a zooming operation, and is principally used for converting the focal length. The third group is a compensator lens group which generally has a positive refractive power and which moves along the optical axis during a zooming operation to maintain an image plane at a given location as it varies with a movement of the second group. The fourth group is a relay lens system which remains stationary during a focusing or a zooming operation.