Based on the recently developed ptychographical iterative engine (PIE), we suggest a lens assisted microscopy to realize quantitative phase imaging without using interferometry. The sample is imaged with a lens system; a pinhole on the image plane scans the image at a proper step interval; the diffraction pattern is recorded simultaneously by a CCD at Fresnel area. With a slightly changed PIE algorithm, the phase image of the sample can be accurately reconstructed from the recorded diffraction pattern. The main advantage of this suggested method lies in its capability to retrieve the phase information from the recorded intensity directly, and thus it has more flexibility over conventional interferometric techniques. The feasibility of the suggested method is verified by reconstructing the modulus and phase image of a biological sample from a set of 10 by 10 diffraction patterns, and the result matches the analysis well.