Abstract: A medium magnification objective for video disks comprising three or four single lenses for which the number of lenses constituting the objective is small, the working distance is large and flatness of image is high.

Abstract: A medium magnification objective for video disks comprising a first, second, third and fourth lens components in which the first lens component is a negative lens, the second lens component is a positive meniscus lens with its concave surface positioned toward the object, the third lens component consists of one or two positive lenses, the fourth lens component is a negative meniscus lens with its convex surface positioned toward the object, and for which the number of lenses constituting the objective is small, the working distance is large, flatness of image is high and resolving power is also high.

Abstract: A medium magnification objective for video disks comprising four single lenses for which the number of lenses constituting the objective is small, the working distance is large and flatness of image is high.

Abstract: A copying objective lens system of four-component six-element lens configuration comprising a front and rear lens groups arranged symmetrically in respect to the stop positioned at the center, each of said front and rear lens groups comprising a negative cemented doublet lens and positive lens, said copying objective lens system being arranged so that uniform brightness of image can be obtained over the whole field.

Abstract: A reproducing objective for video disks comprising five single lenses for which the working distance is large and flatness of image and resolving power are high.

Abstract: An objective for video disks comprising six lens components of single lenses for which the numerical aperture on the recording surface side is large, working distance is large and aberrations especially spherical aberration and coma are corrected favorably.

Abstract: An objective for video disks comprising five lens components of single lenses for which the numerical aperture on the recording surface side is large, working distance is large and aberrations especially spherical aberration and coma are corrected favourably. Besides, said objective for video disks is arranged so that it can be used also for rays from infinite distance by varying an airspace between a second and third lens components.

Abstract: An objective for video disks of two-component three-lens configuration satisfying the following conditions and having high resolving power and large numerical aperture.(1) 1.25 .gtoreq. f.sub.1 /f .gtoreq. 0.85(2) 2 .gtoreq. .vertline.r.sub.2 .vertline./d.sub.1 .gtoreq. 1(3) n.sub.2 - n.sub.3 .gtoreq. 0.2(4) 1.1 .gtoreq. r.sub.4 /f .gtoreq. 0.82(5) 1 .gtoreq. d.sub.2 /f .gtoreq. 0.