A noncontact optical system using high speed image analysis to measure local tissue deformations and axial strains along skeletal muscle is described. The spatial resolution of the system was 20 pixels/cm and the accuracy was±0.125mm. In order to minimize the error associated with discrete data used to characterize a continuous strain field, the displacement data were fitted with a third order polynomial and the fitted data differentiated to measure surface strains using a Lagrangian finite strain formulation. The distribution of axial strain along the muscle-tendon unit was nonuniform and rate dependent. Despite a variation in local strain distribution with strain rate, the maximum axial strain, E{sub}xx = 0.614±0.045 mm/mm, was rate insensitiveand occurred at the failure site for all tests. The frequency response of the video system (1000 Hz) and the measurement of a continuous strain field along the entire length of the structure improve upon previous noncontact optical systems for measurement of surface strains in soft tissues.
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机译：描述了使用高速图像分析来测量沿骨骼肌的局部组织变形和轴向应变的非接触式光学系统。系统的空间分辨率为20像素/ cm，精度为±0.125mm。为了最小化与用于表征连续应变场的离散数据相关的误差，将位移数据与三阶多项式进行拟合，并使用拉格朗日有限应变公式对拟合数据进行微分以测量表面应变。沿肌腱单元的轴向应变分布不均匀且与速率有关。尽管局部应变分布随应变率而变化，但最大轴向应变E {sub} xx = 0.614±0.045 mm / mm对速率不敏感，并且在所有测试中均出现在失效部位。视频系统的频率响应（1000 Hz）和沿结构整个长度的连续应变场的测量比以前用于测量软组织中表面应变的非接触式光学系统有所改善。
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