Research on the coherence of light source using biprism

The spatial coherence of expanded light source is due to the correlation between different lightening parts, and the temporal coherence is due to the correlation between the values of a wave at two different times. Starting from the visibility of interference fringe, an analysis is made for the coherence in biprism coherence experiment, and the coherence length and critical width formula are derived. The experimental methods for measuring the coherence length and critical width of expanded light source and estimating the monochromaticity of light filter are given.