What is coherence?
Coherence is of two types: temporal and spatial. Temporal coherence is a measure of the correlation between the phases of a light wave at different points along the direction of propagation. Spatial coherence is a measure of the correlation between the phases of a light wave at different points transverse to the direction of propagation. Spatial coherence tells us how uniform the phase of the wave front is.
“Coherence” is a technical term referring to amplitude, periodicity, and spectral purity of the intrinsic autonomic nervous system rhythm, this rhythm manifesting as the rate at which the heart beat rate changes. “Coherence” of this rhythm is indicative of autonomic nervous system balance and resulting psycho-physiological condition.
