Multi-laser scanning unit

Details Multi-laser scanning unit Multi-laser scanning unit

1999-10-26

2001-01-30

Spyrou, Cassandra (Department: 2872)

Optical: systems and elements

Holographic system or element

Using a hologram as an optical element

C359S015000, C359S016000, C359S017000, C347S118000, C369S103000

Reexamination Certificate

active

06181448

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-laser scanning unit (LSU) capable of diffracting and scanning light incident from a plurality of light sources, and more particularly, to a multi-LSU in which a plurality of scanning lines (rays) are directionally the same and incident onto an image of a photoreceptor.
2. Description of the Related Art
In general, a multi-LSU is adopted in a color printer and is used to form a plurality of latent electrostatic images required to develop a color image in combination with a plurality of colors including yellow (Y), magenta (M), cyan (C), black (K), and the like. In this case, a plurality of scanning lines scanned by the multi-LSU and incident onto a photoreceptor such as a photosensitive belt or photosensitive drum, must be parallel at predetermined intervals, such that scanning directions of the plurality of scanning lines are parallel each other.
Referring to
FIGS. 1 through 3
, a conventional multi-LSU capable of generating four scanning lines corresponding to the colors Y, M, C and K, includes a driving source
11
for providing a rotatory force, a deflection disk
15
having a plurality of sectors each with a hologram pattern
15
a,
and a light source unit
20
which is arranged facing one surface of the deflection disk
15
and which radiates light onto the deflection disk
15
. The light source unit
20
includes four light sources
21
,
23
,
25
and
27
, which irradiate light onto four incident points S
1
, S
2
, S
3
and S
4
, respectively, wherein each pair of points adjacent to each other form a right angle at the rotary center of the deflection disk
15
. Also, the four incident points S
1
, S
2
, S
3
and S
4
, are placed with equal radii from the rotary center of the deflection disk
15
.
The incident light lines are diffracted by the hologram patterns
15
a
by rotation of the deflection disk
15
and form scanning lines L
11
, L
21
, L
31
and L
41
in the directions indicated by the arrow (→). Here, the scanning lines L
11
and L
31
are parallel (to the Y-axis) and are opposite in direction. Also, the scanning lines L
21
and L
41
, perpendicular to the scanning lines L
11
and L
31
, are parallel (to the X-axis) and are opposite in direction.
Traveling paths of the scanning lines L
11
, L
21
, L
31
and L
41
are changed by a plurality of mirrors such that the centers of the scanning lines travel along the X-axis. That is, the scanning line L
11
is reflected by a mirror M
1
to travel in the X-axis direction, and the scanning line L
21
is reflected by a mirror M
21
toward the rotary center of the deflection disk
15
and then reflected again by a mirror M
22
positioned on the rotary center of the deflection disk
15
to travel in the X-axis direction. Also, the scanning line L
31
is reflected by a mirror M
3
to travel in the X-axis direction, and the scanning line L
41
is reflected by a mirror M
41
toward the rotary center of the deflection disk
15
and reflected again by a mirror M
42
positioned on the rotary center of the deflection disk
15
to travel in the X-axis direction.
Scanning directions of scanning lines L
12
, L
22
, L
32
and L
42
, scanning in the X-axis direction after being reflected by the mirrors M
1
, M
21
, M
22
, M
3
, M
41
and M
42
, are indicated by the arrow (→) in FIG.
2
. As shown in
FIG. 2
, the scanning lines L
12
, L
22
and L
42
, have the same scanning directions, but the direction of the scanning line L
32
is opposite to that of the scanning lines L
12
, L
22
and L
42
.
That is, in the case of using a plurality of mirrors and post-holographic optical elements to change the traveling path of the light, after being reflected by the mirrors M
1
, M
22
, M
3
and M
42
, the plurality of scanning lines are parallel in scanning directions for a photoreceptor, but the direction of the scanning line L
32
is still opposite to that of the others.
Thus, when forming an image on the photoreceptor, image information must be compensated for in the circuitry due to the different scanning directions. That is, the light source
25
providing the scanning line L
32
must transfer the image data in the opposite direction to match the image provided by the remaining light sources
21
,
23
and
27
. That is, there is a disadvantage in that the light sources
21
,
23
and
27
provide image information in the direction indicated by {circle around (X)} while the light source
25
provides image information in the direction indicated by ⊙ as shown in
FIG. 3
, so that image data processing is complicated.
SUMMARY OF THE INVENTION
To solve the above problem, it is an object of the present invention to provide a multi-laser scanning unit (LSU) in which a plurality of scanning lines formed by a deflection disk having the same scanning direction.
Accordingly, to achieve the above object, there is provided a multi-laser scanning unit (LSU) comprising: a driving source for providing a rotatory force; a deflection disk installed around a rotary shaft of the driving source having a plurality of sectors each with a hologram pattern for diffracting and deflecting incident light, for scanning light through rotation; a plurality of light sources installed facing one surface of the deflection disk for irradiating a plurality of light lines onto predetermined points of the deflection disk; and a light path changing means for changing traveling paths of the plurality of scanning lines formed by the rotation of the deflection disk, wherein the plurality of light sources are arranged such that two incident points which are the farthest from each other among the plurality of incident points formed on the deflection disk form 180° with the center point of the deflection disk.


REFERENCES:
patent: 4761046 (1988-08-01), Funato
patent: 5182659 (1993-01-01), Clay et al.

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