An inspection system and a method of using the same are disclosed. The inspection system comprises an illumination source configured to emit an extreme ultraviolet (EUV) illumination beam for illuminating a sample, one or more first multi-cell detectors configured to generate a first illumination intensity distribution signal based on a first photocurrent, one or more second multi-cell detectors configured to generate a second illumination intensity distribution signal based on a second photocurrent, a detector assembly configured to receive the illumination beam and generate images, and a controller configured to: receive the images from the detector assembly, calibrate the second illumination intensity distribution signal to the images by mapping distortions in the second illumination intensity distribution signal to distorted pixels in the images, increase or decrease intensities of the distorted pixels in the images to generate corrected images, and detect defects on the samples.