Some embodiments provide techniques for determining a set of Abbe's kernels which model an optical system of a photolithography process. During operation, the system can receive optical parameters (e.g., numerical aperture, wavelength, etc.) for the photolithography process's optical system. Next, the system can use the optical parameters to determine a point spread function for an Abbe's source. Note that the point spread function for the Abbe's source can be determined either by discretizing the optical system's light source using a set of concentric circles, or by discretizing the optical system's light source in an orthogonal fashion. The system can then determine a correlation matrix from the point spread function. Next, the system can determine the set of Abbe's kernels by performing an eigen decomposition of the correlation matrix using principal component analysis. The system can then use the set of Abbe's kernels to compute image intensity.