Abstract: Telecentric retrofocus lenses and projection systems comprising such lenses are disclosed. The lenses are compact and provide a wide field of view (>70.degree.) with effective distortion correction. The lenses comprise, in order from the image side, a first lens group G1, comprising an aspheric lens having a negative focal length, an aperture, and a second lens group having a positive focal length and having a lens that has maximum refractive power among the lenses of the second lens group. Conditions apply to the ratio of the focal lengths of the first and second lens groups and the distance between the aperture and the focal length of the lens within the second lens group having maximum refractive power. The conditions effectively provide compact, wide-field, low-aberration images. Projection systems using these lenses are also disclosed.

Abstract: A projection lens system has a wide angle with small value for back focus, superior telecentric characteristics, and small distortion. The projection lens system includes a first lens group having a negative refractive power and a second lens group having a positive refractive power. The focal length of the entire system, the focal length of the first lens group and the focal length of the second lens group satisfy conditional formulas.

Abstract: A variable-magnification image taking device comprising a phototaking lens for varying magnification, a solid-state image pickup device for receiving an object image formed by the phototaking lens and recording the image information of the object image, a moving device for axially moving the solid-state image pickup device, and a control device for controlling the moving device so as to position the solid-state image pickup device at the focus position of the object image, movable according to the magnification-varying operation of the phototaking lens.

Abstract: A zoom lens system for projecting an image of an object on a screen, comprises, sequentially from a screen side, a first lens group having a positive refracting power, a second lens group having a negative refracting power, a third lens group having a positive refracting power, a fourth lens group having a negative refracting power and a fifth lens group having a positive refracting power. The first lens group is so disposed as to be movable for focusing along an optical-axis direction. The second lens group is so disposed as to be movable for zooming along the optical-axis direction. The third lens group is so disposed as to be movable for correcting a fluctuation in image position due to the zooming. The fourth and fifth lens groups are fixed with respect to the optical-axis direction during the zooming. The third lens group has, sequentially from the screen side, a front lens unit having a negative refracting power and a rear lens unit having a positive refracting power.

Abstract: A re-imaging optical system for re-imaging a first image formed by an objective lens into a second image of desired size includes, in succession from the object side, a first lens unit which is a field lens constructing the exit pupil of the objective lens and the entrance pupil of the re-imaging optical system so as to be substantially conjugate with each other, a forward sub-unit of a second lens unit, the forward sub-unit having a negative refractive power, an optical member for making the second image formed by the re-imaging optical system erect, and a rearward sub-unit of the second lens unit, the rearward sub-unit having a positive refractive power.