The EUV optical image is significantly altered by secondary electron blur (modeled as a Gaussian with 1/e distance = sigma). Since in reality blur does not follow a cleanly characterized distribution with fixed sigma, the natural variation of the distribution results in significant random dose errors, shown by the deviations from the original optical image, which ultimately affect the resolution of the image. The optical image is defined by a cosine-squared wave. The image is then convoluted with the Gaussian blur function given by exp(-x2/sigma2) to represent the effect of secondary electron blur. After the convolution is performed, the result is normalized so that the half-pitch is resolved at the same threshold (normalized dose of 0.5) as the original optical image.