Extension of the measuring range in deformation measurement using artificial phase compensation

Compensation or comparative measurement is a natural way to overcome the limited measuring range of TV holography or digital holography. In this case the resultant displacement field is the difference of the actual deformation and a known deformation pattern. The compensation can be digital, because these measuring techniques operate with images recorded with digital camera. Development of Spatial Light Modulators (SLM) enables the application of active holographic optical elements in coherent optical metrology. These modulators are capable to reconstruct digital holograms optically; therefore they can be used as active holographic optical elements. The goal of the project was to perform adaptive comparative measurements, where an optically reconstructed image of a recorded or simulated single or double exposure hologram is used for holographic illumination of another object. In this paper conventional TV holographic or digital holographic arrangement with holographic object illumination applied for comparative displacement measurement with adaptive features. Measurement setups were built, containing devices performing feedback, which is capable to project the real image of the master object - using its previously recorded or computer simulated digital holograms - onto the test object to calculate the difference deformation directly.