Laser code symbol scanner employing optical filtering system having narrow band-pass characteristics and spatially separated optical filter elements with laser light collection optics arranged along laser light return path disposed therebetween

Claim 1

A laser code symbol scanning system, comprising: a compact housing having a light transmission aperture through which visible light can exit and enter said compact housing; a first optical filter element installed over said light transmission aperture disposed along a laser light return path extending through said light transmission aperture, and having wavelength-selective filtering characteristics in the visible band, said first optical filter, element functioning as a scanning window in said compact housing, and preventing light having wavelengths up to slightly below a predetermined wavelength in said visible band from passing from the outside of said compact housing, through said scanning window, and into said compact housing; and a scan data producing means disposed in said compact housing, for producing scan data indicative of the intensity of laser light reflected off a code symbol on an object located within at least a portion of a scan field defined external to said compact housing, said scan data producing means including a laser beam producing means for producing a visible laser beam characterized by said predetermined wavelength, a laser beam scanning means for projecting said visible laser beam and repeatedly scanning said visible laser beam through said scanning window and across said scan field and said code symbol, a laser light collection means for collecting along said laser light return path, laser light reflected off said code symbol and passing through said scanning window, and a laser light detection mean disposed along said laser light return path, for detecting the intensity of laser light reflected off said code symbol and collected by said laser light collection means, and automatically producing scan data indicative of the detected light intensity; a second optical filter element, spatially separated from said first optical filter element, disposed along said laser light return path between said first optical filter element and said laser light detection means, and having wavelength-selective filtering characteristics in said visible band, 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 only laser light reflected off said code symbol and having wavelengths within said narrow wavelength bandwidth; and a scan data processing means for processing produced scan data code indicative of said detected light intensity.