Optical: systems and elements – Holographic system or element – Using a hologram as an optical element
Reexamination Certificate
1999-03-19
2001-01-09
Chang, Audrey (Department: 2872)
Optical: systems and elements
Holographic system or element
Using a hologram as an optical element
C359S018000, C359S196100, C347S241000, C347S243000, C347S263000
Reexamination Certificate
active
06172780
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser scanning apparatus, and more particularly, to a laser scanning apparatus in which a beam emitted from an optical source is deflected by a scan disk having a plurality of diffraction patterns formed thereon, and projected onto a scanning object such as a photoreceptor drum via a light path changing unit.
2. Description of the Related Art
FIG. 1
shows a laser scanning apparatus adopted in a conventional electrophotographic printer. The laser scanning apparatus includes an optical source
11
and a scan disk
14
. Reference numeral
12
denotes a cylindrical lens, and reference numerals
13
,
15
and
16
denote optical elements for changing a light path and controlling the size of a beam. The scan disk
14
is segmented into a plurality of areas on which diffraction patterns for deflecting an incident beam are formed.
A beam emitted from the optical source
11
is deflected by the scan disk
14
which is rotated by a motor (not shown), and projected onto a photoreceptor drum
17
via the optical elements
15
and
16
. The light beam repeatedly scans the photoreceptor drum
17
corresponding to the diffraction patterns formed on the scan disk
14
.
In the laser scanning apparatus, the scan disk
14
deflects an incident beam in a desired direction, but transmits or reflects some of the incident beam in an undesired direction. The traveling path of the beam emitted from the scan disk
14
in the undesired direction may be changed and finally reach the photoreceptor drum
17
in the laser scanning apparatus. This causes an image forming error.
High-speed rotation of the scan disk
14
is required to increase the scanning speed, which generates noise.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a laser scanning apparatus including means for absorbing and blocking abnormal beams not diffracted to a normal light path by a scan disk.
Accordingly, to achieve the above objective, there is provided a laser scanning apparatus comprising: an optical source installed on a main frame; a scan disk which is rotatably installed on the main frame and has diffraction patterns formed thereon for deflecting a beam emitted from the optical source in a predetermined direction to achieve a normal light path; and a means for shielding an abnormal beam that is emitted from the optical source and diffracted or reflected off the normal light path by the scan disk.
The light shielding means includes an optical absorbing member for absorbing and blocking the abnormal beam.
The light shielding means further includes a shielding plate on which a window is formed to pass only a beam deflected to the normal light path by the scan disk.
According to another aspect of the present invention, the light shielding means includes a shielding cap which is installed over the main frame to seal the optical source and the scan disk and has a window for passing only a beam deflected to the normal light path by the scan disk.
REFERENCES:
patent: 4165464 (1979-08-01), Ikeda et al.
patent: 5064258 (1991-11-01), Inokuchi et al.
Chang Audrey
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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