Non-destructive testing of carbon reinforced plastics by means of phase retrieval

We present an approach to inspect carbon reinforced plastic components which is based on phase retrieval using a liquid crystal spatial light modulator (SLM). The SLM is located in the Fourier domain of a 4f-imaging system and is used to modulate the incident light with the transfer function of propagation. This configuration allows for the recording of consecutive intensity measurements, with the wave field scattered by the investigated object in various propagation states across a common recording plane. In contrast to existing phase retrieval approaches, the measuring time is considerably reduced, since the switching time of the SLM is less than 50ms. This enables non-destructive testing under thermal load. Experimental results are presented which demonstrate that the approach can be used to assess structural properties of technical components made from carbon reinforced plastics.