Door viewer device - has front convex lens provided with front concave surface and rear convex surface to correct chromatic aberration

摘要

A door viewer includes two prisms of rectangular isosceles triangle shape in cross section whose hypotenuse surface abut horizontally, a front convex lens and a piano-convex eyepiece lens. The front convex lens has a front concave surface and a rear convex surface to correct chromatic aberration. The convex surfaces of the front and eyepiece lens are positioned face to face with each other to correct barrel distortion. The view casts an image onto a ground glass section formed on or provided abutting the eyepiece lens.