Monitoring microstructural material changes in paper through microscopic speckle correlation rate measurements

• Published in: Optics and lasers in engineering Vol. 42; no. 2; pp. 193 - 201
• Main Authors: Sjödahl, M., Larsson, L.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2004; Elsevier
• Subjects: Correlation; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Experimental Mechanics; Experimentell mekanik; Fundamental areas of phenomenology (including applications); Imaging and optical processing; Materials science; Materials testing; Microscopy; Microstructure; Nondestructive testing: optical methods; Optics; Physics; Speckle and moire patterns; Speckles; Speckles; Correlation; Microscopy; Microstructure; CCD camera; Measurement systems; Printing paper; CW lasers; Experimental study; Optical set up; Spatial resolution
• ISSN: 0143-8166; 1873-0302; 1873-0302
• DOI: 10.1016/j.optlaseng.2003.08.004

A system for real-time digital speckle correlation rate measurements is developed and applied on printing paper in the micro-scale. The system consists of a continuous laser and a CCD camera connected to a PC. To measure on objects in the micro-scale the system is connected to a stereomicroscope where one of the channels is used for imaging and the other channel is used for illumination of the object surface. The system is evaluated through measurements on printing paper over an area of 1 mm 2 and with a spatial resolution of 30 μm on the object. The results show that the system is able to monitor the dynamics in paper during both wetting and drying in real-time over a time scale ranging from one-tenth of a second to several hours.