Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-02-18
2001-04-03
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S234000, C347S235000, C347S250000
Reexamination Certificate
active
06211898
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus used in a laser printer in which image forming is performed by irradiating a laser beam which has been modulated based on image information through a scanning mirror onto a surface of a photosensitive body.
2. Description of the Prior Art
A known optical apparatus for scanning light such as a laser beam through a scanning mirror is used in a laser printer in which an image is formed by electrophotographic method in which a laser beam modulated based on an image data is scanned onto a photosensitive body surface. As shown in
FIG. 8
in the interior of a main body
101
of the laser printer, a laser beam irradiated by a laser irradiating unit
123
is transmitted onto a surface of a photosensitive body drum
108
through a scanning mirror
121
and reflecting mirrors
122
a
to
122
c.
The photosensitive body drum
108
is supported in an approximately central portion of the main body
101
so as to be rotatable. The scanning mirror
121
is driven by a mirror motor
120
so as to rotate, and scans the laser beam irradiated by the laser irradiating unit
123
in a main scanning direction of the photosensitive body drum
108
, that is, a direction parallel to a rotating axis of the photosensitive body drum
108
. The surface of the photosensitive body drum
108
is uniformly charged with electric charge of single polarity by an electrification unit
114
prior to the transmission of the laser beam, and forms an electrostatic latent image through a photoconductive phenomenon by the laser beam modulated based on the image data. Toner in a developing vessel
116
is supplied to this electrostatic latent image from a developing roller
115
whereby the electrostatic latent image is clarified into a toner image.
On the other hand, in the interior of the main body
101
is formed a paper delivery path
113
which extends from a paper feeding tray
117
through an interval between the photosensitive body drum
108
and a transferring roller
109
and through a fixing device
110
to a paper discharge tray
118
. There are arranged, within this paper delivery path
113
, a paper feeding roller
103
, a paper sensor
107
, delivery rollers
111
, and paper discharge rollers
112
. Paper
102
stacked in the paper feeding tray
117
is fed into the paper delivery path
113
by the rotation of the paper feeding roller
103
. The fed paper
102
is detected by the paper sensor
107
. The toner image of the photosensitive body drum
108
is transferred onto the surface of the paper
102
when the laser irradiating unit
123
irradiates a laser beam based on the detection signal of the paper sensor
107
and the paper
102
is made to pass between the photosensitive body drum
108
and the transferring roller
109
synchronously with the rotation of the photosensitive body drum
108
. The toner image transferred onto the surface of the paper
102
is fused and fixed on the surface of the paper
102
by heating and pressurizing operations of the fixing device
110
. The paper
102
on which the toner image has been fixed is discharged to the paper discharge tray
118
by the paper discharge rollers
112
. After the surface of the photosensitive body drum
108
has faced the paper
102
, the surface is cleared of residual toner by means of a cleaner
126
and is thereafter reused for forming electrostatic latent images and toner images.
As shown in
FIG. 9
, the scanning motor
120
, the scanning mirror
121
, the reflecting mirrors
122
a
to
122
c
(note that the reflecting mirrors
122
b
and
122
c
are omitted from the drawing), the laser irradiating unit
123
and a start sensor
124
make up an optical unit
201
in the laser printer. The scanning mirror
121
scans a laser beam from the laser irradiating unit
123
which has been modulated based on the image data while steady-state rotation in a direction shown by arrow CW, driven by the scanning motor
120
. The reflecting mirrors
122
a
to
122
c
transmit the laser beam which has been scanned by the scanning mirror
121
to the photosensitive body drum
108
. The scanned laser beam is further received by the start sensor
124
. Upon receipt of the laser beam, the start sensor
124
outputs a SYNC signal. This SYNC signal is used for creating reference timing for outputting image data to the laser irradiating unit
123
.
FIG. 10
is a block diagram showing an arrangement of a control unit of the laser printer. The control unit of the laser printer is composed of the optical unit
201
, a synthesizing circuit
202
, an image data generating circuit
203
and a load device
204
, which are connected with a CPU
209
having a ROM
207
and RAM
208
through a interface
205
. The optical unit
201
inputs the SYNC signal output by the start sensor
124
to the image data generating circuit
203
and the CPU
209
. The CPU
209
creates a LEND signal based on the SYNC signal which is then output to the synthesizing circuit
202
. Based on the SYNC signal, the image data generating circuit
203
outputs the image data to the synthesizing circuit
202
. The synthesizing circuit
202
outputs a video signal synthesized from the LEND signal and the image data to the laser irradiating unit
123
of the optical unit
201
. The laser irradiating unit
123
irradiates a laser beam based on the Video signal.
FIG. 11
is timing charts for each signal of the control unit of the laser printer. The SYNC signal for creating the reference timing for outputting image data to the laser irradiating unit
123
may be, for instance, a low level signal output from a time at which the start sensor
124
receives the laser beam. Therefore, in order to generate the SYNC signal, a laser beam needs to be irradiated from the laser irradiating unit
123
. On the other hand, in order to accurately reproduce image data by using the photosensitive body drum
108
, only the laser beam modulated by the image data should be transmitted to the surface of the photosensitive body drum
108
. For this purpose, the CPU
209
sets the LEND signal, which is output to the synthesizing circuit
202
during a period of time TA beginning shortly time t
1
at which the SYNC signal has been input until time t
2
, to “H”. This period of time TA is sufficient for the laser beam to cross the photosensitive body drum
108
in an axial direction.
The image data generating circuit
203
, on the other hand, starts output of image data to the synthesizing circuit
202
at time t
3
when a period of time TB has elapsed after time t
1
at which the SYNC signal has been input. This period of time TB is a period of time in which an irradiating position of a scanning light of the laser beams moves from a position at which the light is received by the start sensor
124
to a position at which the light faces the photosensitive body drum
108
. The Video signal synthesized from the LEND signal and the image data is output from the synthesizing unit
202
to the laser irradiating unit
123
. It should be noted that the laser irradiating unit
123
terminates irradiation of a laser beam when the Video signal is “H” and irradiates a laser beam when the Video signal is “L”.
In this manner, a Video signal of level “L” is input into the laser irradiating unit
123
for continuously irradiating a laser beam within a specified period of time when the laser beam is irradiated at a position at which it is received by the start sensor
124
. On the other hand, when the laser beam is irradiated at a position at which it faces the photosensitive body drum
108
, the LEND signal is set to “H” level and the Video signal corresponding to the image data is input to the laser irradiating unit
123
so that a laser beam modulated based on the image data is irradiated onto the surface of the photosensitive body drum
108
. Such control of signals which are input to a light source of the laser irradiating unit or the like is similarly performed not only for laser printers but also for optical apparatuses using
Le N.
Nixon & Vanderhye P.C.
Pham Hai C.
Sharp Kabushiki Kaisha
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