shows the schematic of the proposed II display. The planoconvex lens is denoted as lens 1, the plano-convex lens with flatpanel is denoted as lens 2. Conveniently, we assume that lens 1 and
lens 2 display real images simultaneously. The front principle plane
H2 of lens 2 moves a distance of l relative to the front principle
plane H1 of lens 1. The distance l is given by