Digital holography for microscopic imaging and 3D shape measurement

Digital holography is used for a wide range of applications. A lot of techniques deal with holographic microscopy or the 3D shape measurement of objects. We present our approaches to these applications. To increase the resolution of a microscopic imaging system a method for aperture synthesis is applied, where the spatial frequency shift, the global phase differences and the amplitude ratios of the individual sections of the Fourier spectrum are measured by using an overlap between them. It is shown that this method can be performed out including sub-pixel accuracy. The experimental holographic setup uses tilted illumination beams realized by an LCoS SLM, which can be easily adapted to the numerical aperture of the microscope objective. For the 3D shape measurement of arbitrary diffuse-reflecting macroscopic objects a novel approach is demonstrated, which uses common digital holographic setup together with a second CCD and an LCoS to modulate the object wave. Our idea is to capture a series of holograms from multiple positions and to apply concepts of structured light photogrammetry, which deliver more accurate depth information. The method yields a dense 3D point cloud of a scene.