Active metrology by digital holography

Holography provides the possibility to record and to reconstruct the complete information of optical wave fields. Recording holograms directly on CCD targets allows the numerical reconstruction of phase and intensity by the computer. Interferometric techniques such as 3d-displacement analysis and 3d-contouring can be implemented in this way easily and with high flexibility. In addition to the numerical reconstruction, the digitally recorded holograms can be transmitted via telecommunication networks and optically reconstructed at any desired place using LCD displays or DMDs. This possibility opens new experimental approaches with respect to the investigation of similar objects at different places by using principles of comparative holography. Moreover, the direct access to all relevant components of the digitally stored wave front allows the application of principles of active vision to coherent metrology. In this article the principles of digital holography are explained shortly. After that the combination of digital holography with principles of active metrology are discussed. Finally some practical examples are given to illustrate this combination.