Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1999-02-16
2001-06-05
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S245000, C347S138000
Reexamination Certificate
active
06243128
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus having an image writing device for writing a latent image on a surface of a photoconductor by deflecting a light beam by way of an optical defector and exposing the surface of the photoconductor with the deflected light beam, and more particularly to an image forming apparatus in which adjustment of a scanning direction of the light beam so as to be at a right angle relative to a direction in which a surface of the photoconductor moves such that a rectangular latent image is easily formed.
2. Discussion of the Background
It is well known that digital copying machines using electrophotography include an image writing device for writing a latent image on a surface of a photoconductor by deflecting a light beam by way of an optical defector and exposing the surface of the photoconductor with the deflected light beam.
FIG. 1
illustrates an example of such a digital copying machine. In
FIG. 1
, digital copying machine
100
includes an image reading device
111
, a printing device
112
and an automatic document feeding device
113
. The automatic document feeding device
113
separates each of the original document sheets set in the automatic document feeding device
113
and feeds the separated sheets to a contact glass
114
into a reading position. After an image of the original document is read, the automatic document feeding device
113
discharges the sheet from the reading position on contact glass
114
.
FIG. 2
is a sectional drawing illustrating image reading device
111
. Image reading device
111
includes a first carriage A having a light source including an illuminating lamp
115
, a reflecting mirror
116
, and a first mirror
117
(shown in FIG.
1
). A second carriage B of image reading device
111
includes a second mirror
118
and a third mirror
119
. When reading an original document placed on contact glass
114
, first carriage A travels at a constant speed while second carriage B travels at a speed half that of first carriage A, thereby optically scanning the original document on the contact glass
114
. The original document on contact glass
114
is illuminated by illuminating lamp
115
and reflecting mirror
116
. As shown in
FIG. 1
, the light reflected by the original document is directed to a charge-coupled device (CCD)
122
by a lens
121
via first mirror
117
, second mirror
118
, third mirror
119
, and a color filter
120
. CCD
122
converts the received light image to electrical signals and outputs analog image signals representing the image of the original document. Referring again to
FIG. 2
, after the image of the original document is read, first carriage A and second carriage B return to respective home positions (represented by the solid line depictions) from the positions where image reading ends (represented by the line-and-dot line depictions). CCD
122
may be configured such that three arrays of CCD elements are arranged for R (red), G (green) and B (blue), respectively, for reading a original color document.
Referring now to
FIG. 1
, the analog image signals output from CCD
122
are converted into digital image signals by an analog-to-digital converter (not shown) and various kinds of image processing, such as converting multi-value data into binary data and vice versa, gradation level conversion, magnification ratio change, image editing and so on, are applied to the digital image signals by an image processing circuit included on image processing board
123
.
In order to prepare photoconductor drum
125
to receive a latent image, photoconductor drum
125
is driven by a drive unit (not shown) and the surface of the photoconductor drum
125
is uniformly charged by a charging device
126
. After the digital image signals have been processed with image processing board
123
, they are sent to a semiconductor circuit board (not shown), and a latent image is formed on the surface of photoconductor drum
125
according to the digital image signals with an image exposure operation performed by a laser beam scanning device
127
. The latent image on the photoconductor drum
125
is then developed with toner to form a visible toner image by developing device
128
.
A transfer sheet is fed to a registration roller
136
from a selected one of sheet cassettes
133
,
134
and
135
, toward the photoconductor drum
125
at a timing to register the leading edge of the transfer sheet with the leading edge of a toner image formed on the surface of the photoconductor drum
125
. The toner image on photoconductor drum
125
is transferred onto the transfer sheet with transfer device
130
. The transfer sheet carrying the toner image is separated from the photoconductor drum
125
with separating device
131
and is conveyed by conveying device
137
to fixing device
138
, where the toner image is fixed onto the transfer sheet. The transfer sheet carrying the fixed toner image is then discharged onto an exit tray
139
. The surface of the photoconductor drum
125
is cleaned with cleaning device
132
after the transfer paper is separated such that residual toner is removed from the surface of photoconductor drum
125
.
FIG. 3
is a schematic drawing illustrating the construction of the laser beam scanning device
127
and the relative positions of scanning device
127
and photoconductor drum
125
. Laser beam scanning device
127
includes a semiconductor laser unit
140
having a semiconductor laser. A laser beam light emitted from the semiconductor laser is converted to a parallel light flux with a collimate lens (not shown) in the semiconductor laser unit
140
. The parallel light flux is then reformed to a predetermined shape by passing through an aperture (not shown) in the semiconductor laser unit
140
. The reformed light flux is converged in the sub scanning direction with cylindrical lens
141
and is thereby directed onto a surface of a polygonal mirror
142
. Polygonal mirror
142
is formed in a polygonal shape and is rotated at a constant speed in a fixed direction with motor
143
(illustrated in FIG.
1
). The rotation speed of the polygonal mirror
142
is determined according to the rotation speed of the photoconductor drum
125
, the writing resolution of the laser beam scanning device
127
, and the number of surfaces of the polygonal mirror
142
.
The laser beam directed onto the polygonal mirror
142
is deflected by a reflecting surface of the polygonal mirror
142
at an equiangular velocity and is thereby directed into an f&thgr; lens
144
. The f&thgr; lens
144
is configured to convert the laser beam deflected by the polygonal mirror
142
at equiangular velocity so as to scan the surface of the photoconductor drum
125
at a constant linear velocity. The laser beam is directed to the surface of the photoconductor drum
125
via reflecting mirror
145
and dust-proof glass
146
. The f&thgr; lens
144
also has a surface tilt correcting function, which causes a portion of the laser beam passing through f&thgr; lens
144
at positions out of the image forming area, to be reflected by a synchronization detection mirror
147
so as to be detected by a synchronization detection sensor
148
. The synchronization detection sensor
148
outputs a detect signal in accordance with the collision of the laser beam thereupon such that a synchronization signal for aligning a writing start position for each scanning in the main scanning direction (indicated by an arrow in
FIG. 3
) is obtained.
Laser beam scanning device
127
, as described above, is attached to a housing of a main body of the digital copying machine
100
such that a latent image is formed on the surface of the photoconductor drum
125
with the laser beam in a rectangular form having a right angle at each comer, i.e., when a rectangular latent image formed on the surface of the photoconductor drum
125
with the laser beam and the latent image is developed with toner, one side of the rectangular toner image is perpendicular to the direction
Le N.
Nguyen Lamson D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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