Light is focused in a system for electro-optically scanning and reading bar code symbols by an aperture stop having a first optical portion for optically modifying a first part of a light beam to have a beam cross-section of a known size within a depth of field in which a symbol to be read is scanned by the first beam part, and a second light-transmissive, optical portion bounding the first portion and operative for optically modifying and directing a second part of the light beam away from the first part.