Security envelope detectable for foreign substances

Abstract

A security envelope that allows a mail handler or recipient to inspect its contents for potentially harmful granular/powder substances without ever opening the envelope is provided. The envelope comprises a front see-through window and a rear see-through window that are registered, such that an observer of the envelope can view through the envelope to examine its contents. A security background may, in place of, or in addition to, the rear window, be provided on the inside of the envelope, such that the observer can additionally verify that the envelope was sent from a trusted source. In this case, the security background will be registered with the front window. The security background may be composed of nano-structures that appear as a standard background when viewed with the naked eye, but reveal identifying elements when viewed under magnification. These nano-structures may additionally be distorted or diffused in the present of any granular/powder substance, thereby alerting the observer of a potentially harmful substance. Additional features, such as coating the inside of the windows with the particle-attracting substance, or printing the security background with a particle attracting ink, may also be provided to increase detection of any granular/powder substance within the envelope.