Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-06-30
2002-01-22
Lee, Susan S. Y. (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S134000, C347S137000, C347S241000, C347S244000, C347S258000
Reexamination Certificate
active
06340982
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure device and an image forming apparatus suitable for an electrophotographic apparatus.
2. Description of Related Art
FIG. 9
of the accompanying drawings schematically shows a side elevational view of an LED (light emitting diode) printer. An LED printer
14
′ is equipped with a paper cassette
15
, four printing units
17
′, a conveying belt
18
, a fixing unit
19
, and an outlet port
20
.
The LED printer
14
′ prints a color image on paper
16
using toners of four colors, yellow, magenta, cyan and black, and includes four printing units
17
′, which are substantially identical in construction, one for each of the four colors, and are arranged in series along the travelling path of the paper
16
.
The photosensitive drum
2
of the individual printing unit
17
′ is disposed so as to extend perpendicularly across the traveling path of the paper
16
. The charging unit
26
, the exposure unit
27
′, the developing unit
28
, the transferring unit
29
, the discharging unit
30
and the cleaning unit
31
are arranged on and around the circumference of the photosensitive drum
2
for performing the respective functions while the photosensitive drum
2
makes a single rotation.
The paper cassette
15
holds the paper
16
, which is not printed yet, to supply and deliver it to the printing units
17
′ as a demand arises, and the conveying belt
18
conveys the paper
16
to the individual printing units
17
′.
The fixing unit
19
fixes a toner image formed in the printing units
17
′, and the outlet port
20
allows the paper
16
, which has been printed in color, to be removed out of the LED printer
14
′.
Color-printing is performed on the LED printer
14
′ in the following manner. The paper cassette
15
delivers one sheet of the paper
16
at a time onto the conveying belt
18
. The conveying belt
18
then brings the paper
16
to the printing units
17
′ where the individual printing units
17
′ sequentially form toner images of colors of yellow, magenta, cyan and black.
In the individual printing unit
17
′, the charging unit
26
electrically charges the circumferential surface of the photosensitive drum
2
uniformly. Then the exposure unit
27
′ forms an electrostatic latent image on the circumferential surface of the photosensitive drum
2
in accordance with an original image to be printed. Then the developing unit
28
develops the latent image with toner, bringing the latent image into a visible image of the toner. After that, the transferring unit
29
transfers the toner of the visible image to the paper
16
, at which time the toner image on the paper
16
is not fixed yet.
After the toner image is transferred to the paper
16
, the discharging unit
30
discharges the circumferential surface of the photosensitive drum
2
, whereupon the cleaning unit
31
removes residual toner.
Subsequently in the first printing unit
17
′, the paper
16
to which toner image of the first primary color (yellow) transferred by the transferring unit
29
is conveyed to the second printing unit
17
′ on the conveying belt
18
. Then in the second printing unit
17
′, third and fourth printing units
17
′, toner image in the same printing process as in the first printing unit
17
′ is performed. Likewise, as a result, in each of the toner images of the other colors (magenta, cyan and black) are formed on the same paper
16
.
The paper
16
, with the color toner image formed on it by the four printing units
17
′, is transferred to the fixing unit
19
by the conveying belt
18
to be fixed and then is removed out of the LED printer via the outlet port
20
as color-printed paper.
FIG. 10
schematically shows a cross-sectional view of an exposure device which is applied to the LED printer of the related art. An exposure device
1
′ of
FIG. 10
is installed in the exposure unit
27
′ (
FIG. 9
) and has an exposure body
124
and an image forming lens
109
. The exposure body
124
is composed of an outer casing
122
and an inner casing
123
, which are generally C-shaped in cross section, the inner casing
123
being telescopically fitted in the outer casing
122
with their through-hole side facing each other to define a light-emitting space
121
inside the exposure body
124
.
On the bottom wall of the light-emitting space
121
(hereinafter called the light-emitting-space bottom wall
134
), a print board
112
is disposed on which a plurality of sets of light emitting diode microchips (hereinafter called the LED microchips
104
) and driver elements
105
are arranged in array in series perpendicularly to the drawing sheet of FIG.
10
.
The LED microchips
104
is circuits on which a plurality of light emitting diodes are mounted, and the driver elements
105
are driver circuits to energize the associated LED array
103
. The LED microchip
104
and the driver element
105
of each set are electrically interconnected via an upwardly arcuate wires
106
. Each light emitting diode of the LED microchip
104
is connected to a corresponding driver element
105
.
The wires
106
connect the LED microchips
104
and the driver elements
105
with or without a wire ball. The wire-ball-free connection is technically more difficult than the with-wire-ball connection.
A through-hole
125
is disposed above the LED microchip
104
in the light emitting space
121
, in which an image forming lens
109
is mounted in such a posture that the center line
109
A of the image forming lens
109
coincides with the center of beam intensity distribution outputs (hereinafter called the intensity-distribution-center line
107
) of the LED microchip
4
.
The rotation center
2
A of the photosensitive drum
2
is disposed on the upward extension of the center line
109
A of the image forming lens
109
. The beam output from the LED array
103
, through the image forming lens
109
, strikes the circumference of the photosensitive drum
2
to form a latent image on it.
However, in the exposure device
1
′, a local beam emitted from the LED array
103
reflects on the wires
106
(hereinafter, the beam reflects on the wire
106
is called the stray light
110
), which connect the LED microchips
104
and the driver elements
105
, and then tends to enter the image forming lens
109
since the beam-intensity-distribution center line
107
coincides with the center line
109
A of the image forming lens
109
.
The stray light
110
, as well as local part of the beam directly strikes the incidence surface
109
B of the image forming lens
109
output from the LED array
103
(hereinafter called the proper beam
108
), strikes the incidence surface
109
B of the image forming lens
109
. As a result, the stray light
110
forms an undesired latent image on the circumferential surface of the photosensitive drum
2
and becomes one cause for deterioration of the quality of a printed image.
SUMMARY OF THE INVENTION
With the foregoing problems in view, it is an object of the present invention to provide an exposure device and an image forming apparatus in which a more vivid printed image can be formed as possible stray light is prevented from the striking image supporting body.
According to a first concept of the present invention, there is provided an exposure device comprising: a driver element; a light emitting diode microchip connected to the driver element by wires and having a light emitting diode array for outputting light for exposure; and an image forming lens for directing the light output from the light emitting diode array of the light emitting microchip onto an image supporting body as exposure light; the image forming lens being disposed in such a posture that the center line of the image forming lens is out of axial alignment with the center line of intensity distribution of the light output from the light emitting diode array on an incidence surface of th
Houki Youji
Nagatomi Tsutomu
Nakayasu Hirofumi
Taira Yoshihiko
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Lee Susan S. Y.
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