Comparative digital holography

We described a method for direct holographic comparison of the shape or the deformation of two objects when it is not necessary that both samples be located at the same place. In contrast to the well-known incoherent techniques based on inverse fringe projection, this new approach uses a coherent mask that is imaged onto a sample object that has a microstructure different from that of the master object. The coherent mask is created by digital holography to permit instant access to complete optical information on the master object at any wanted place. Transmission of the digital master holograms to the relevant places can be made with a broadband digital telecommunication network such as the Internet.