Far-field speckle generated by weak scattering screen is a central bright spots, around which is a speckle structure similar to the normal speckle. According to the far-field speckle produced by weak scattering screen, it is assumed that the image plane speckle of weak scattering screen is the result of coherent superposition of both uniform background and normal speckle. However, there exists a discrepancy between the assumption and the actual image plane speckle. Based on the above circumstances, the statistical properties are studied about the image plane speckle fields produced by Gaussian correlation weak scattering screens in the 4f optical imaging system of high-pass filter. It is found that the above assumption is correct when the surface roughness of the weak scattering screen and the wavelength of the incident light wave are almost the same.