Bar code reading apparatus with multifocal length optical system

摘要

A bar code reader is provided which comprises a photodetector responsive to light reflected from a bar code to provide a signal indicative of bar code information, a lens assembly including a near range focus lens and a long range focus lens having different focal lengths, and a liquid crystal filter assembly. The liquid crystal assembly includes a near range focus filter and a long range focus filter and selectively allows only light emerging from one of the near range focus lens and the long range focus lens to reach the photodetector according to the distance to the bar code.