Already in 1967 J. W. Goodman und R. W. Lawrence established the Digital Holography. E. N. Leith und N. Abramson already dealt with the short pulse holography in 1960th and 1970th years.
A lens less short coherence holographic set-up with a laser of limited coherence length makes it possible to reconstruct an optical section from a hologram of an object at the optical path difference zero. The multi-level sectioned image of the object is obtained by digital reconstructing and processing a sequence of holograms recorded during stepwise shifting of a mirror in the reference arm of the holographic set-up.
Principle of the frequency comb holography
A femtosecond frequency comb laser features a periodical temporal coherence function. By use of a Michelson interferometer with frequency comb light, this coherence function delivers a contrast maximum of interference not only at the optical path difference zero, but also at every position representing an integer multiple of pulse distance Y, see Fig. 1. By choice of a frequency comb laser convenient for the source may be used for multi-level optical sectioning. The object shape is obtained by digitally reconstructing and processing a sequence of holograms recorded during stepwise shifting of a mirror in the reference arm. Experimental results are presented.
Short coherence digital holography may be used as well for depth sectioning, in this case the interference between the object and reference wave is observed only when their optical path lengths are matched within the coherence length of the laser.
- K. Körner, G. Pedrini, I. Alexeenko, T. Steinmetz, R. Holzwarth, W. Osten: “Short temporal coherence digital holography with a femtosecond frequency comb laser for multi-level optical sectioning”, Opt. Express, Vol. 20, Ausgabe 7, S. 7237-7242 (2012). http://dx.doi.org/10.1364/OE.20.007237
- K. Körner, G. Pedrini, I. Alexeenko, W. Lyda, T. Steinmetz, R. Holzwarth, W. Osten, "Multi-level optical sectioning based on digital holography with a femtosecond frequency comb laser", Proc. SPIE 8430, 843004 (2012).
- K. Körner, G. Pedrini, C. Pruss, and W. Osten: „Verfahren und Anordnung zur Kurz-Kohärenz-Holografie“, Deutsches Patent DE 10 2011 016 660 B4.
- K. Körner, G. Pedrini, C. Pruss, and W. Osten: „Verfahren und Anordnung zur Kurz-Kohärenz-Holografie“, WO 2012/136238 A1.
- K. Körner, G. Pedrini, C. Pruss, and W. Osten: “Method and Arrangement for Short Coherence Holography” (wird 2014 veröffentlicht unter United States patent application number 14/110,100).