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Laser speckle photometry (LSP) is an innovative, non-destructive monitoring technique based on the detection and analysis of thermally or mechanically activated speckle dynamics in a non-stationary optical field. With the development of speckle theories, it has been found that speckle patterns carry information about surface characteristics. Therefore, LSP offers a great potential for the characterization of material properties and monitoring of manufacturing processes. In contrast to the speckle interferometry method, LSP is very simple and robust. The sample is illuminated by only one laser beam to generate a speckle pattern on the surface. The signals obtained are directly recorded by a CCD or CMOS camera. By appropriate optical solutions for the beam path, typically, resolutions of less than 10 μm are reached if larger areas are illuminated. LSP is definitely a contactless, quick and quality relevant material characterization and defect detection method, allowing process monitoring in many industrial fields. Examples from online biotechnological monitoring and laser based manufacturing demonstrate further potentials of the method for process monitoring and controlling.

Monitoring is indispensable for the optimization and simulation of biotechnological processes. Hairy roots (hr, plant tissue cultures) are producers of valuable relevant secondary metabolites. The genetically stable cultures are characterized by a rapid filamentous growth, making monitoring difficult with standard methods. This article focuses on the application of laser speckle photometry (LSP) as an innovative, non‐invasive method to characterize Beta vulgaris (hr). LSP is based on the analysis of time‐resolved interference patterns. Speckle interference patterns of a biological object, known as biospeckles, are characterized by a dynamic behavior that is induced by physical and biological phenomena related to the object. Speckle contrast, a means of measuring the dynamic behavior of biospeckles, was used to assess the biospeckle activity. The biospeckle activity corresponds to processes modifying the object and correlates with the biomass growth. Furthermore, the stage of the cultures’ physiological development was assessed by speckle contrast due to the differentiation between active and low active behavior. This method is a new means of monitoring and evaluating the biomass growth of filamentous cultures in real time. As a potential tool to characterize hairy roots, LSP is non‐invasive, time‐saving, can be used online and stands out for its simple, low‐cost setup.

The Laser Speckle Photometry is a newly developed non-contact non-destructive testing method which is based on the detection and analysis of thermal or mechanical activated characteristically speckle dynamics. The determination of the material damaged state is based on the understanding of structural changes on different scaling levels given by the physical mesomechanics. The hierarchical behavior of the mesomechanical structures (meso-structures) leads to the hypothesis of the fractal nature of the deformation structure. The fractal dimension DF is a suitable parameter to characterize the fatigued material state. In the case of the laser speckle photometry method the modified auto-correlation function from the pixel intensity changes of the speckles images was used for the computation of Parameter DF. The hardness or porosity of materials is defined by micro-structural variation and is combined with several thermal properties of the material. Therefore the speckle thermal diffusivity parameter K was determined using thermal conduction equation from the pixel intensity of speckle images changes during thermal activation. Afterwards correlation between the norm K and hardness and porosity, respectively was found. Results of this research will be presented in the present contribution.

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The damage and stress conditions of large industrial components have to be tested continuously. Especially welding processes in the field of coal production demand a nondestructive monitoring of internal stresses under an external load. In a first step, a new optical method, Laser Speckle Photometry was used during laboratory welding experiments under tensile and bending loads at high strength construction steels. Laser Speckle Photometry is a fast and contactless method for measuring spatial-temporal dynamics of speckle field with high temporal resolution after local heat excitation. The thermally induced change in the material structure causes changes in the speckle-field, which is formed by a probing laser. The shift of the speckle-field is analyzed by statistical methods, using correlation functions. The result of processing is the two-dimensional distribution of thermal diffusivity coefficient correlated to porosity, materials strain or hardness [1-3]. Here, the results of the welding experiments under load are presented. It is shown, that the Laser Speckle Photometry is a suitable technique for nondestructive monitoring and characterization of internal material stresses under external load

In this paper the investigation of r.f.‐sputter‐deposited Ta, Ta‐N and Ta‐N‐O thin films is presented. Using atomic force microscopy in combination with sheet resistance measurements, Auger electron spectroscopy and x‐ray diffraction, the thin film properties and microstructure are examined. Two crystalline modifications of Ta (tetragonal β‐Ta and bcc α‐Ta) are reported. By incorporation of nitrogen and/or oxygen into the Ta films, nanocrystalline and quasi‐amorphous structures can be achieved. Finally, the usefulness of the films as diffusion barriers in Cu‐based metallization systems is described.© 1997 John Wiley & Sons, Ltd.

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