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Ergodic and non-ergodic regimes in temporal laser speckle imaging
Optics Letters
|June 15, 2017
Summary
Laser speckle contrast imaging (LSCI) temporal averaging has a non-ergodicity problem. This study reveals non-monotonic contrast dependence on dynamics, showing both ergodic and non-ergodic regimes, impacting LSCI interpretations.
Area of Science:
- Biomedical optics
- Image analysis
- Non-invasive imaging techniques
Background:
- Laser speckle contrast imaging (LSCI) is widely used for dynamic biological tissue imaging.
- Interpretation of LSCI data typically assumes ergodic (ensemble) averaging.
- Temporal averaging in LSCI can introduce non-ergodicity, affecting measurement accuracy.
Purpose of the Study:
- To investigate the non-ergodicity problem in temporal averaging within LSCI.
- To analyze the theoretical and numerical implications of finite time windows on speckle statistics.
- To characterize the relationship between temporal speckle contrast and sample dynamics.
Main Methods:
- Theoretical analysis of temporal averaging in LSCI.
- Numerical simulations to assess speckle statistics.
- Quantification of speckle contrast dependence on sample dynamics.
Main Results:
- Temporal speckle statistics in a finite window differ from ensemble statistics.
- Speckle contrast shows non-monotonic dependence on sample dynamics.
- Identified ergodic (negative correlation) and non-ergodic (positive correlation) regimes.
Conclusions:
- The non-ergodic regime in LSCI temporal averaging is an artifact of finite time statistics.
- Understanding these regimes is crucial for accurate LSCI data interpretation.
- Characterizing the transition between ergodic and non-ergodic states improves LSCI methodology.
