Illumination System to Provide Higher and Uniform Image Brightness in a Linear Scanner
Original Publication Date: 1991-Nov-01
Included in the Prior Art Database: 2005-Apr-04
Disclosed are methods to increase image brightness and uniformity in a linear scanner.
Illumination System to Provide Higher and Uniform Image
in a Linear Scanner
methods to increase image brightness and
uniformity in a linear scanner.
line converters are often used to geometrically
transpose light from circular sources, such as a halogen bulb, to a
line source. High N. A. (numerical aperture) fibers are used to
allow for higher light collection efficiency. This also results in
highly diverging light at the line (illumination) end.
illustrates the fiber position (with no lens), and shows
how the light diverges from the fibers. A document to be scanned is
located within the documentation location window defined by dotted
optics, when used in the form of a cylindrical lens
on the emitted light at the fiber bundle line end results in near
collimation of the light (Fig. 1), i.e., light beam is parallel
within 5 degrees. The fiber end is placed at the focal point of the
cylindrical lens. Two functions are achieved. The light divergence
is reduced, leading to brighter object illumination. Second, due to
near collimation of light, the light intensity is more uniform and
falls off at a much lower rate with document position (within the
beam area shown by dotted lines).
feature of this article is to introduce a
mechanical deflection in the lens (Fig. 2), thereby introducing a
variation in distance from the fiber line end to the...