Beam scanning optical apparatus

Details Beam scanning optical apparatus Beam scanning optical apparatus

2000-07-28

2002-06-25

Spyrou, Cassandra (Department: 2872)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C359S204200, C359S216100

Reexamination Certificate

active

06411419

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a beam scanning optical apparatus for creating an image through beam scanning.
RELATED ART
Heretofore, a beam scanning optical apparatus has been used as an image writing means in an electrophotographing process, and has been incorporated in a laser printer as an output unit of a computer or a facsimile machine, a laser facsimile and the like. Recently, there has been raised a demand for a high speed color laser printer, and accordingly, there has been highly interested in a tandem type beam scanning optical apparatus for this high speed color laser printer.
Next, a beam scanning optical apparatus incorporated in conventional tandem type color image forming apparatus will be explained with reference to
FIGS. 6 and 7
.
FIG. 6
is a view for explaining a cooler image forming apparatus incorporating a conventional beam scanning apparatus, and
FIG. 7
is a plan view illustrating the beam scanning optical apparatus shown in FIG.
6
.
As shown in
FIG. 6
, four imaging stations are located in the cooler image forming apparatus, respectively comprising photosensitive drums (photosensitive media)
10
a
,
10
b
,
10
c
,
10
d
serving as image bearing media, and further, there are provided around the respective photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
, electrifiers
11
a
,
11
b
,
11
c
,
11
d
for uniformly electrifying the outer surfaces of the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
, development parts
12
a
,
12
b
,
12
c
,
12
d
for developing latent images, cleaning members
15
a
,
15
b
,
15
c
,
15
d
for removing residual toner, erasers
16
a
,
16
b
,
16
c
,
16
d
for initializing the surface potential of the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
, optical units
8
a
,
8
b
,
8
c
,
8
d
serving as beam scanning optical apparatuses for irradiating light beams which correspond to image data, onto the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d.
In this arrangement, the image stations create an yellow image, a magenta image, a cyan image and a black image, respectively, and the optical units
8
a
,
8
b
,
8
c
,
8
d
emit beams
9
a
,
9
b
,
9
c
,
9
d
as scanning beams, respectively corresponding to the black image, the yellow image, the magenta image and the cyan image. Further, these beams
9
a
,
9
b
,
9
c
,
9
d
form predetermined electrostatic latent images in surfaces
7
a
,
7
b
,
7
c
,
7
d
to be scanned on the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
, respectively.
As shown in
FIG. 7
, the optical units
8
a
,
8
b
,
8
c
,
8
d
respectively incorporate, beam emitters
1
a
,
1
b
,
1
c
,
1
d
, and deflectors
3
a
,
3
b
,
3
c
,
3
d
for deflecting beams emitted from the beam emitters
1
a
,
1
b
,
1
c
,
1
d
, scanning lenses
4
a
,
4
b
,
4
c
,
4
d
for focussing the deflected beams on the surfaces
7
a
,
7
b
,
7
c
,
7
d
to be scanned, mirrors
5
a
,
5
b
,
5
c
,
5
d
for leading the beams onto the surfaces
7
a
,
7
b
,
7
c
,
7
d
to be scanned, and synchronous detectors
6
a
,
6
b
,
6
c
,
6
d
for detecting synchronization among the beams.
An intermediate transfer belt (intermediate transfer medium)
13
in the form of an endless belt is laid below the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
, running through the respective imaging stations, and being supported by two rollers. The intermediate transfer belt
13
is turned around in a direction indicated by the arrow.
First transfer units
14
a
,
14
b
,
14
c
,
14
d
for transferring toner images created on the respective photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
onto the intermediate transfer belt
13
are provided in the vicinity of the respective photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
, the intermediate transfer medium being interposed therebetween.
It is noted that the toner images on the intermediate transfer belt
13
are transferred on to a sheet
17
fed from a stack of sheets stored in a paper feed cassette, by means of a second transfer unit
18
, and then, the sheet is discharged onto a discharge tray (which is not shown) by way of a fixing unit
19
.
In the cooler image forming apparatus having the above-mentioned structure, when a predetermined color image output signal is received, the rotation of the respective photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
and the intermediate transfer belt
13
is started. Further, the respective photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
are uniformly electrified by the electrifiers
11
a
,
11
b
,
11
c
11
d
at predetermined potentials.
Meanwhile, in the respective optical units
8
a
,
8
b
,
8
c
,
8
d
, the deflectors
3
a
,
3
b
,
3
c
,
3
d
deflect the beams from the beam emitters
1
a
,
1
b
,
1
c
,
1
d
. The image zones on the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
are scanned with the thus deflected beams, respectively, by means of the mirrors
5
a
,
5
b
,
5
c
,
5
d
so as to carry out exposure. Before scanning the image zones of the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
, the beams are synchronized with one another by means of the synchronous detectors
6
a
,
6
b
,
6
c
,
6
d
, and then, the beams are irradiated, corresponding to image data, with a predetermined timing.
After the exposure by the beams, the electrified potentials on the outer surfaces of the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
are lowered so that electric latent images corresponding to the image data are created thereon. Thus, the optical units
8
a
,
8
b
,
8
c
,
8
d
create the latent images on the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
for the respective colors in response to the image data corresponding respectively to black, yellow, magenta and cyan.
The electric latent images created on the photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
are developed with respective color toners by means of the developing parts
12
a
,
12
b
,
12
c
,
12
d
so as to be turned into color toner images. These toner images are transferred onto the intermediate transfer belt
13
by the first transfer units
14
a
,
14
b
,
14
c
,
14
d
so that the toner images having black, yellow, magenta and cyan are superposed with one another on the intermediate transfer belt
13
.
After the superposition of the four cooler toner images is completed on the intermediate transfer belt
13
, these four cooler images are transferred in a batch onto the sheet
17
fed from the paper feed cassette, by means of the second transfer unit
18
, and are then heated for fixing so that a full cooler image can be obtained on the sheet
17
.
It is noted that residual toner on the respective photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
is removed by the cleaning members
15
a
,
15
b
,
15
c
,
15
d
after completion of the transfer of the images, and then, the respective photosensitive drums
10
a
,
10
b
,
10
c
,
10
d
are electrically initialized by the erasers
16
a
,
16
b
,
16
c
,
16
d
in preparation for the successive image formation. Thus, the printing operation is completed.
Thus, the images having back, yellow, magenta and cyan can be formed in parallel with one another, and accordingly, a beam scanning optical apparatus which can cope with high speed color printing can be obtained.
However, in the conventional beam scanning optical apparatus as mentioned above, since the four optical units are arranged, not only the body of the image forming apparatus becomes large-sized, but also the weight thereof becomes higher, resulting in inclusion of a high cost.
BRIEF SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a compact beam scanning optical apparatus.
To the end, according to the present invention, there is provided a beam scanning optical apparatus comprising a first beam optical system composed of a plurality of optical blocks, in which beams emitted from beam emitters are deflected by deflectors and are then led to scanning lenses by means of mirrors so as to be focused on a surface to be scanned, an

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