Speckle correlation is the basis of speckle-based optical measurements and imaging recovery technologies, which determines the resolution of the opitcal system. At present, the theoretical description of speckle size (granularity or resolution) is not accurate enough and lacks of experimental verification. The influencing factors of speckle pattern autocorrelation size were explored, compared it with the same numerical aperture objective, and the scattering lens properties of thin scattering medium were revealed. Through the multiple sets of measurements for speckle autocorrelation and lens focusing size, the results show that the apodization function will affect the resolution, and the Abbe criterion needs to be corrected according to the specific optical path, which has a certain reference value for speckle-based measurement and imaging technology.