Point-source digital in-line holographic microscopy with numerical reconstruction is ideally suited for quantitative phase measurements to determine optical path lengths and to extract changes in refractive index within accuracy close to 0.001 on the submicrometer length scale. This is demonstrated with simulated holograms and with detailed measurements on a number of different micrometer-sized samples such as suspended drops, optical fibers, as well as organisms of biological interest such as E. coli bacteria, HeLa cells, and fibroblast cells.

In in-line holographic microscopy a pinhole illuminates an object and a CCD-detector directly records the hologram in a pixel-pitch-dependent distance. A rapidly calculating exact reconstruction technique using a reorganized hologram with a low number of pixels, the tile superposition technique, is presented. The algorithm is applied on imaging of a 2 microm bead cluster, and it is compared with other reconstruction techniques. The high-contrast image corresponds to an NA of 0.7. A full 4 megapixel reconstruction with a resolution approaching the diffraction limit is possible in less than a minute. The technique is a base for high-resolution wide-field imaging by multispot illumination.

For lensless digital in-line holographic microscopy a new state-of-the-art spatial resolution corresponding to an NA of 0.8 is shown based on the tile superposition propagation. The result is proved using a common glass sample carrier with a refraction index of 1.52. Single-shot high-resolution imaging is possible by suppression of coherent reflections in an optimized arrangement using partially coherent laser light illumination.

There are several applications known for years using laser speckles for optical characterization of human skin. Laser speckle contrast analysis (LASCA) for non-invasive monitoring of capillary blood flow is one of them. 1,2 Recent reports calling the technique laser speckle contrast imaging (LSCI) describe the detailed opportunities and limitations of this technique for non-invasive blood flow quantification, 3 for example, for wound healing research. 4 However, besides blood flow there is more in there using laser speckles. Surface roughness quantification is an application 5 recently found to be interesting for skin analysis as well 6 and the assessment of skin tumour perfusion. The laser speckle technique has already been used to assess the skin roughness and skin tumours. [7][8][9] The contactless optical and label-free method has decisive advantages, particularly in the medical environment. In addition to

In lensless digital in-line holographic microscopy, currently applied fast reconstruction techniques use approximations limiting the usable NA for optical resolution. The computational effort for an exact scalar reconstruction with straightforward algorithms depends on the relation between the desired resolution and the given pixel pitch of the detector. So there is a trade-off between achievable image resolution and required computation time. We present an exact reconstruction algorithm that guaranties optimum resolution with affordable computation time. Experimental results show a realized NA of at least 0.62. A 1 megapixel hologram was reconstructed in about 1.5 s.