Yasuhiro Takaki

By Tatsuki Tahara, Reo Otani, Yasuhiko Arai and Yasuhiro Takaki

In this chapter, we introduce multiwavelength digital holographic techniques and a novel multiwavelength imaging technique. General multiwavelength imaging systems adopt temporal division, spatial division, or space-division multiplexing to obtain wavelength information. Holographic techniques give us unique multiwavelength imaging systems, which utilize temporal or spatial frequency-division multiplexing. Conventional multiwavelength digital holography systems have been combined with one of the methods listed above. We have proposed phase-shifting interferometry selectively extracting wavelength information, characterized as a multiwavelength three-dimensional (3D) imaging technique based on holography and called phase-division multiplexing (PDM) of multiple wavelengths. In PDM, wavelength-multiplexed phase-shifted holograms are recorded, and multiwavelength information is separately extracted from the holograms in the space domain. Phase shifts are introduced for respective wavelengths to separate object waves with multiple wavelengths in the polar coordinate plane, and multiple object waves are selectively extracted by the signal processing based on phase-shifting interferometry. Additionally, the system of equations needed to obtain a multiwavelength 3D image is solved with less wavelength-multiplexed images using two-step phase-shifting interferometry-merged phase-division multiplexing (2π-PDM), which makes the best use of 2π ambiguity of the phase and two-step phase-shifting method. The PDM techniques are reviewed and color 3D imaging ability is described with numerical and experimental results.

Part of the book: Holographic Materials and Optical Systems