Abstract: A radial gradient index lens system has a refractive index distribution. The refractive index decreases from an optical axis along a height. The lens system has two meniscus lens elements whose convex surfaces have a larger radius of curvature than concave surfaces. The meniscus lens elements are arranged symmetrically with respect to an aperture stop so that the convex surfaces thereof face an object side and an image side, respectively. The gradient index lens system is for use in a copying apparatus or as a reading optical system.

Abstract: A zoom lens system includes from one side to the other side: a first lens unit of a negative power having a negative lens element concave to the one side; a second lens unit of a positive power having a positive meniscus lens element convex to the one side, a biconcave lens element whose one side surface has a larger radius of curvature and a biconvex lens element; and a third lens unit of a negative power having a negative meniscus lens element concave to the other side. In order to perform zooming, the distance between the first lens unit and the second lens unit and the distance between the second lens unit and the third lens unit are varied, and the entire zoom lens system is moved along the optical axis.

Abstract: Disclosed is a hot dip coated steel sheet obtained by hot dipping a steel sheet in a hot-dip metal bath comprising zinc-based or zinc/aluminum based alloy, and a process for producing the same.The hot dip coated steel sheet has a film of oxides which are compounds of cobalt or iron, or both of these, with oxygen, and the film can prevent the hot dip coated steel sheet from undergoing color change into grayish black in the case where spangles are minimized, where a coating contains corrosion resistance-improving elements such as magnesium and aluminum, or where a chromate treatment is applied after the mechanical processings were carried out.Formation of oxide film on the surface of the hot dip coated steel sheet is carried out by a method in which an aqueous solution obtained by dissolving a salt of cobalt or a salt of iron or both of these is sprayed on the surface of a coating of the steel sheet when the temperature of the coating is 170.degree. C. or higher.