Zakharov Pavel
Opt Lett. 2017 Jun 15;42(12):2299-2301. doi: 10.1364/OL.42.002299.
The non-ergodicity problem of temporal averaging in the laser speckle contrast imaging (LSCI) is discussed both theoretically and numerically. We demonstrate that temporal speckle statistics assessed within a finite time window might differ from the statistics of the speckle ensemble. The dependence of temporal speckle contrast on sample dynamics is non-monotonic and demonstrates regimes of negative (ergodic), as well as positive correlations with dynamics (non-ergodic). The ergodic regime is similar to an ensemble (spatial) averaging case and is typically assumed for interpretation of LSCI measurements. The positive relation in the non-ergodic regime is an artifact of temporal statistics which we further quantify and describe the transition between two regimes.
从理论和数值两方面讨论了激光散斑对比成像（LSCI）中时间平均的非遍历性问题。我们证明，在有限时间窗口内评估的时间散斑统计量可能与散斑系综的统计量不同。时间散斑对比度对样本动态的依赖性是非单调的，表现出负相关（遍历性）以及与动态的正相关（非遍历性）状态。遍历性状态类似于系综（空间）平均情况，通常在解释LSCI测量时被假定。非遍历性状态下的正相关是时间统计的一种假象，我们进一步对其进行了量化，并描述了两种状态之间的转变。
