The influence of mask-alignment errors on the fabrication of four-level binary lenses has been investigated. The pupil function was derived as a function of the amount of misalignment between the two mask patterns based on scalar diffraction theory. It was found that the phase term in the pupil function affects only the location of the point-spread function, whereas the uneven light transmittance degrades the image quality in the direction of the misalignment. The Strehl intensity was found to decrease almost linearly with respect to the amount of error. #1998 Optical Society of America OCIS codes: 050.1380, 050.1970, 110.3000.
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