ABSTRACT
A copying lens is one used to transfer, with minimum loss, information from one permanent or transient image, i.e. the subject, to another image plane for recording in permanent form at the same or altered size. Facsimile recordings are often needed. Common examples are scanners, film writers, microdocumentation, same-size and reduction cine film copying, phototypesetting, recording of cathode ray tube (CRT) screens and office copiers. A CRT phosphor screen is a typical curved subject and can be spherical or cylindrical with various radii of curvature and thicknesses. The copy lens may accordingly be computed to give a flat field from a curved screen image at a given object conjugate. Apart from its topography the copy subject may have other important features which influence lens choice or design. Most camera systems feature a ‘macro’ lens that is eminently suited to copying applications rather than true photomacrography at magnifications greater than 1.0.
