Patent ID: 8118228

Claim:
A laser scanner for reading a symbol target, comprising: a housing; a laser generator disposed in the housing and operative to generate a laser beam that is focused to a focal distance d f, ; an output window supported by said housing and being positioned to receive the laser beam at an output window tilt angle θ t , a scanning mechanism for scanning said laser beam through and across a scanning region of said output window having a nominal thickness t nom , and across a scanning field defined external to said housing where a symbol target is present within said scanning field; and a photodetector for detecting the intensity of light energy from said laser beam as said laser beam is scanned through said output window, reflected and/or scattered off said symbol target, and collected by light collection optics and focused onto said photodetector during laser beam scanning operations; wherein said output window has front and rear surfaces and vertical and horizontal axes, and is optically transparent to allow said laser beam to be transmitted through said output window and towards said symbol target within said scanning field; wherein said output window includes a small vertical wedge angle, α, between the front and rear surfaces of said output window; wherein said small vertical wedge angle is oriented substantially parallel to the vertical axis, aligned perpendicular to the direction of scanning of said laser beam through said output window, and is approximated by the equation: α > 2 ⁢ θ t ⁢ t nom d f wherein θ t is said output window tilt angle defined between the normal to the surface of said output window and said laser beam being directed from said laser beam generator through and across the scanning region of said output window; wherein t nom is the nominal thickness of said output window across said scanning region; d f is the focus distance of said laser beam measured from said output window; and wherein said small vertical wedge angle (a) is generally less than 1 degree, (b) does not significantly modify the direction of propagation of said laser beam as said laser beam is scanned across said scanning region of said output window, and (c) significantly reduces the power level of signal noise at said photodetector, by eliminating optimum interference conditions between the following laser beam components within the scanning region of said output window: (i) the laser beam incident upon and transmitted through said output window; and (ii) the reflected laser beam reflecting off of the front and rear surfaces of said output window and transmitted out into said scanning field.