Estimate of the minimal coherence length of probe optical radiation in interferometry

The minimal coherence length of probe optical radiation sufficient for formation of a homogeneous interference structure is estimated. The estimate is based on the analysis of the interference structure in the intensity distribution of the field scattered by rough surfaces and point objects and also formed in interferometers. Analysis was performed for the field intensity detected for the time T > 10τ_c (under the condition that the coherence time of the probe radiation is τ_c > 3/ω₀, where ω₀ is the central frequency of the emission spectrum). It is shown that the minimal coherence length L_c of the probe radiation, at which the homogeneous stratified interference structure of the scattered field can be still formed, is 8λ (λ is the central wavelength). The possibility of using this result for determining the maximal information content of the method of low-coherence optical tomography is analysed.