A system for providing cost effective, secure key exchange from at least one first device to at least one second device through at least one proxy server is provided. The invention relates to a method and system comprising an image plane on which there is formed an image of the target observed by the optical system, a first optical component with an adjustable focal length, and a prism with an optical path that is adjustable to correspond to the focal length adjusted for the first optical component. If a wafer burn-in test operation is performed under the second power supply system, a DC current path formed by a latch-up phenomenon of a memory cell can be shut off.