Light-in-Flight measurements by Digital Holography

摘要

Light-in-flight was introduced as method to record holograms with light of short coherence length: Only the short distance delivers a hologram where the object and the reference wave coincide to have the same optical path. Nils Abramson used pulses of picoseconds with coherent lengths of millimeter to demonstrate how light travels through a lens. The width of the holographic plate was his delay line for the reference wave. However, Fresnel holograms can be recorded directly on a CCD sensor, electronically stored and numerically reconstructed. The method is called Digital Holography. It has been applied to make comparable experiments to those mentioned before. The area of the CCD target was divided into several areas which were hid from the reference wave with changed optical path. The delays for the reference wave performed by glas plates with varying thickness. The different views of a wavefront can be reconstructed from the corresponding parts of one single holographic recording. This means that the temporal evolution of a wavefront can be observed by numerical methods. Experimental results are shown.