Spatially-separated optical filtering system for a laser bar code symbol scanner

摘要

A laser bar code symbol scanner employing a narrow band-pass optical filtering system of novel construction is disclosed. A first optical filtering element is installed in the light transmission aperture of a bar code scanner housing. A second optical filtering element is installed inside the scanner housing near the light detecting element. The first and second optical filtering elements have wavelength selective properties such that taken together they cooperate to form a narrow wavelength bandpass optical filtering system which allows only transmission of light at and around a certain predetermined wavelength into the photodetector element. The present invention also hides aesthetically unappealing electro-optical components mounted in the scanner housing from plain view and the optical filtering elements of the system can be easily and inexpensively manufactured without compromising the performance of the scanner.