Optical filtering system for a laser bar code scanner having narrow band-pass characteristics with spatially separated filtering elements
First Claim
1. A laser symbol scanning system, comprising:
- a housing having a light transmission aperture through which light can enter and exit said housing;
a first optical filter element disposed in said light transmission aperture and along a laser light path extending through said light transmission aperture, and having wavelength-selective filtering characteristics, said first optical filter element function as a scanning window in said housing;
laser beam producing means in said housing for producing a laser beam characterized by a predetermined wavelength;
laser beam scanning means in said housing for projecting said laser beam through said scanning window and scanning said laser beam across a code symbol on an object located within at least a portion of a scan field defined external to said housing;
laser light detection means is said housing disposed in said laser light path, for detecting the intensity of laser light reflected off said code symbol; and
a second optical filter element in said housing, spatially separated from said first optical filter element and disposed along said laser light path between said first optical filter element and said laser light detection means, and having wavelength-selective filtering characteristics, said second optical filter element cooperating with said first optical filter element so as to form a band-pass optical filtering system having a narrow wavelength bandwidth positioned about said predetermined wavelength and passing light reflected off said code symbol having wavelengths only within said narrow wavelength bandwidth.
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Accused Products
Abstract
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 band-pass 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.
24 Citations
13 Claims
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1. A laser symbol scanning system, comprising:
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a housing having a light transmission aperture through which light can enter and exit said housing; a first optical filter element disposed in said light transmission aperture and along a laser light path extending through said light transmission aperture, and having wavelength-selective filtering characteristics, said first optical filter element function as a scanning window in said housing; laser beam producing means in said housing for producing a laser beam characterized by a predetermined wavelength; laser beam scanning means in said housing for projecting said laser beam through said scanning window and scanning said laser beam across a code symbol on an object located within at least a portion of a scan field defined external to said housing; laser light detection means is said housing disposed in said laser light path, for detecting the intensity of laser light reflected off said code symbol; and a second optical filter element in said housing, spatially separated from said first optical filter element and disposed along said laser light path between said first optical filter element and said laser light detection means, and having wavelength-selective filtering characteristics, said second optical filter element cooperating with said first optical filter element so as to form a band-pass optical filtering system having a narrow wavelength bandwidth positioned about said predetermined wavelength and passing light reflected off said code symbol having wavelengths only within said narrow wavelength bandwidth. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification