Fig. 1. Diagram of optical path of projection imaging system used to study speckle characteristics

Fig. 2. Schematic diagram of number of coherent elements of scattered light wave contained in resolution primitive of imaging lens on scattering screen

Fig. 3. Functional relationship between parameters N, M and composite speckle contrast ratio C

Fig. 4. Speckle contrast C as a function of observation distance z₂ and spot diameter d. (a) Dependence of speckle contrast ratio C on observation distance z₂ for different spot diameters; (b) dependence of speckle contrast ratio C on spot diameter d at different observation distances

Fig. 5. Speckle contrast ratio C as a function of observation distance z₂ and aperture diameter D of projection objective lens. (a) Dependence of speckle contrast ratio C on observation distance z₂ under different projection apertures; (b) dependence of speckle contrast ratio C on projection aperture D at different observation distances