We report on a simple self-starting diode-pumped passively mode-locked Er-doped fibre laser based on two semiconductor saturable absorber mirrors (SESAMs), generating sub-picosecond stable optical pulses. Pulses duration between 350 and 650 fs (FWHM) was observed for pulses central wavelengths ranging between 1540 nm and 1570 nm. The cavity basic frequency was 3.7 MHz, and stable operation up to the third harmonic (11.1 MHz) was observed when the output power of the 980 nm diode pump was increased to its maximum value of ~300 mW. The maximum average output power was 19.45 mW, which corresponded to a pulse energy of ~4 nJ. Noise characterization of the mode-locked laser source was performed, in order to estimate the phase noise of the output pulses in terms of timing jitter. All the fiber components in the cavity were polarization maintaining in order to increase long-term stability of the laser operation.
Soft tissues of the body are composite, typically being made up of collagen and elastin fibers with high water contents. The strain measurement in soft tissues has proven to be a difficult task. The digital speckle method, combined with the image processing technique, has many advantages such as full field, noncontact, and real time. We focus on the use of an improved digital speckle correlation method (DSCM) and time-sequence electric speckle pattern interferometry (TSESPI) to noninvasively obtain continual strain measurements on cartilage and vessel tissues. Monoaxial tensile experiments are well designed and performed under constant temperature and the necessary humidity with smart sensors. Mechanical behaviors such as the tensile modulus and Poisson ratio of specimens are extracted based on the deformation information. A comparison of the advantages and the disadvantages of these techniques as well as some problems concerning strain measurements in soft tissues are also discussed.
Soft tissues of human and animals are composite, typically being made up of the collagen and elastin fibres with high water contents. The strain measurement in soft tissues has proven to be a difficult task. Digital Speckle Method, an optical measurement method combining with computer image processing technique, has many advantages like full-field, non-contact and high measuring accuracy. Two main techniques, the Digital Speckle Correlation Method (DSCM) and Electric Speckle Pattern Interferometry (ESPI), have been developed and applied on many aspects. Using these two methods, the strain measurements caused by the continual deformation of soft tissues under pure tensile loading are completed and presented in this paper. Experiments are performed under the conditions of constant temperature and necessitate humidity with smart sensor. After capture a series of speckle patterns in continual time period, the displacement and strain distribution of soft tissues can be obtained by two improved techniques (Improved DSCM and Time-Sequence ESPI). Thus, the tensile modulus and Poisson ratio of soft tissues will be extracted.
Two kinds ofsmart force sensors for the force distribution measurements are presented in this paper. The force distribution testing technique is widely used in intelligent control of robot and biomechanics. Usually a sensor matrix that includes hundreds to thousands micro sensor elements is adopted and that will provides the precise force distribution information for the different requirements. Two kinds of sensor material the piezoelectric ceramic, PVDF and piezo-resistance sensor conducting rubber are introduced in this paper. The requirements ofthe smart structure and the signal processing technique are discussed. Three smart force sensor systems are developed for the robot and biomechanics applications. Some image processing techniques are developed for the signal analysis and data processing.
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