Abstract: A wide angle zoom lens includes sequentially from the object side, a first lens group having a negative refractive power overall and three lenses, including first to third lenses, having a negative refractive power and disposed farthest on the object side; a second lens group having a positive refractive power overall and one or more sets of cemented lenses; and a third lens group having a negative refractive power. This ultra wide angle zoom lens varies intervals between the first lens group, the second lens group, and the third lens group on the optical axis to zoom from the wide angle end to the telephoto end and satisfies given conditions to thereby enable a high zoom ratio, large diameter, and high resolution.

Abstract: A wide angle zoom lens includes sequentially from the object side, a first lens group having a negative refractive power overall and three lenses, including first to third lenses, having a negative refractive power and disposed farthest on the object side; a second lens group having a positive refractive power overall and one or more sets of cemented lenses; and a third lens group having a negative refractive power. This ultra wide angle zoom lens varies intervals between the first lens group, the second lens group, and the third lens group on the optical axis to zoom from the wide angle end to the telephoto end and satisfies given conditions to thereby enable a high zoom ratio, large diameter, and high resolution.

Abstract: Disclosed is a back focus adjusting system for an infrared camera including a lens unit having a lens group to be mounted on the camera main body. The camera main body includes an infrared detector disposed in a vacuum chamber and has a detecting surface that detects the infrared rays; a memory means that stores a position information on the detecting surface obtained by measuring a position in an optical axis direction of the detecting surface of the infrared detector; and a transmitting means that transmits the position information on the detecting surface to the lens unit. The lens unit includes a receiving means that receives the position information on the detecting surface transmitted from the transmitting means of the camera main body and focal position adjusting means that adjusts a position in the optical axis direction of the lens group.

Abstract: A wide angle lens includes sequentially from the object side, a first lens group having a negative refractive power; an aperture stop; and a second lens group having a positive refractive power, where the first lens group includes sequentially from the object side, a negative first lens having on the object side, a convex surface; a negative second lens having on the image side, a concave surface; a negative third lens; and a positive fourth lens. The second lens group includes sequentially from the object side a cemented lens having a positive refractive power and formed by a fifth lens and a sixth lens; a positive seventh lens; and a negative eighth lens having on the image side, a concave surface.

Abstract: An imaging optics capable of compensating for chromatic aberration is provided with a light shielding means in a surface peripheral area of a certain lens element in a lens system so as to block a light flux of a specified wavelength range, thereby eliminating chromatic aberration in halo of the light flux of the specified wavelength range when it passes the periphery of the lens system. Thus, the invention provides the imaging optics that, without an increase in the number of pieces of lens elements and without a use of an expensive specified low-dispersion glass material, in contrast with the prior art imaging optics of the same optical performances, well compensates for chromatic aberration, especially, in halo.

Abstract: An imaging optics capable of compensating for chromatic aberration is provided with a light shielding means in a surface peripheral area of a certain lens element in a lens system so as to block a light flux of a specified wavelength range, thereby eliminating chromatic aberration in halo of the light flux of the specified wavelength range when it passes the periphery of the lens system. Thus, the invention provides the imaging optics that, without an increase in the number of pieces of lens elements and without a use of an expensive specified low-dispersion glass material, in contrast with the prior art imaging optics of the same optical performances, well compensates for chromatic aberration, especially, in halo.