Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2000-02-29
2003-04-01
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S239000
Reexamination Certificate
active
06542177
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed generally to light modulators, and more particularly to a light modulator for spatially modulating a light beam that, without scanning, illuminates an elongate region of a photosensitive surface in a device such as a laser printer.
2. Description of the Related Art
Conventional laser printers use mechanical scanners and complex optics to scan a laser spot onto a photosensitive surface. Typical scanning optics include a multifaceted mirror that spins at high speed for scanning laser light. Such scanners require a predetermined time to spin up to operating speed prior to a first page, and the spinning speed inherently limits how fast the scanner can scan. The mechanical nature of this scanning mechanism is thus disadvantageous and also leads to increased operating noise and maintenance costs.
SUMMARY OF THE INVENTION
Briefly, a laser printing system is provided for illuminating an elongate region of a photosensitive surface. The laser printing system comprises a laser source to generate a light beam in a light path and a light modulation assembly that includes an n×m array of elements, wherein the n×m array has an aspect ratio of at least 1:100. The laser printing system additionally comprises an expansion assembly disposed in the light path between the laser source and the light modulation assembly to expand the light beam and impinge the light beam simultaneously on substantially all of the element in the n×m array of elements.
In one aspect of the present invention, the light modulation assembly comprises a liquid crystal coating over an n×m element array of substrate elements.
In a further aspect of the present invention, the elements are reflector elements.
In another aspect of the present invention, the elements are transmissive elements.
In a further aspect of the present invention, the light modulation assembly modulates the polarization of the light beam to generate a polarization-modulated light beam, and the system additionally comprises a polarization filter disposed to receive the polarization-modulated light beam from the light modulation assembly and to convert the polarization-modulated light beam to a light beam with an amplitude pattern.
In yet a further aspect of the present invention, a light directing assembly is provided for expanding the light beam received from the light modulation assembly and directing the light beam onto the photosensitive surface.
In a further aspect of the present invention, the n×m array of elements comprises elements of different shapes.
In a yet further aspect of the present invention, the elements in the n×m array of elements are interdigitated.
In a further aspect of the present invention, at least some of the light beam impinges on the n×m array of elements at an angle that is not 90 degrees.
In a further aspect of the present invention, the expansion assembly additionally comprises a polarizing beam splitter disposed to direct the expanded light beam onto the n×m array of elements at an angle of substantially 90 degrees and operating to pass light of a predetermined polarization from the n×m array of elements to the photosensitive surface.
In a further aspect of the present invention, the n×m array of elements has an aspect ratio of at least 1:1000.
In a further aspect of the present invention, the n×m array of elements has an aspect ratio of at least 1:5000.
The present invention additionally provides a method for illuminating an elongate region of a surface with a modulated illumination pattern. The method comprises forming a polarized light beam with an aspect ratio of at least 1:100, spatially modulating the light beam to generate a spatially-modulated light beam and directing the spatially-modulated light beam onto a surface.
In a further aspect of this embodiment, forming the polarized light beam comprises generating a laser light beam and expanding the laser light beam to the aspect ratio.
In a further aspect of the present invention, spatially modulating the light beam comprises impinging the expanded laser light beam on an n×m array of modulating elements having different shapes.
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Hewlett--Packard Company
Pham Hai
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