Electrophotographic apparatus and test pattern recording method

Details Electrophotographic apparatus and test pattern recording method Electrophotographic apparatus and test pattern recording method

1998-12-17

2001-05-22

Pendegrass, Joan (Department: 2852)

Incremental printing of symbolic information

Electric marking apparatus or processes

Electrostatic

C399S032000

Reexamination Certificate

active

06236417

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic apparatus for performing image formation by using plural light beams, which apparatus records a test pattern to detect an abnormal state (or wrong state).
2. Related Background Art
In recent years, a so-called multibeam laser printer which performs image formation by using plural light beams, e.g., plural laser beams and obtains a desired image through an electrophotographic process has been studied.
FIG. 12
shows an example of such the multibeam laser printer, and
FIGS. 13A
to
13
I show operation timing of the printer.
In
FIG. 12
, a laser printer
1
is connected to an external equipment
31
such as a computer or the like, and performs image formation on a recording paper under the control of the equipment
31
. The external equipment
31
supplies various control signals and image information to a video controller
27
, and the controller
27
outputs a video signal. A print control unit
26
is a control circuit for controlling each unit in the printer
1
. When an RDY signal from the external equipment
31
becomes TRUE as shown in
FIG. 13A
, the video controller
27
sets a PRINT signal TRUE as shown in FIG.
13
B. When the PRINT signal becomes TRUE, the print control unit
26
starts to drive a main motor
23
and a polygonal motor
14
as shown in
FIGS. 13F and 13G
. When the motor
23
is driven, a photosensitive drum
17
, fixing rollers of a fixing unit
9
and paper discharge rollers
11
start rotation. Then, the print control unit
26
starts to control a light quantity of a semiconductor laser
13
, and also sequentially performs high-voltage driving of a primary charger
19
, a development unit
20
and a transfer charger
21
.
When a time T
1
elapses from a drive start of the polygonal motor
14
and thus rotation of the motor
14
becomes stable as shown in
FIG. 13G
, the print control unit
26
turns on a paper feed clutch
24
to drive a paper feed roller
5
as shown in FIG.
13
H. Thus, a recording paper sheet
3
within a paper feed cassette
2
is fed toward resist rollers
6
. At timing when the paper
3
reaches the rollers
6
, the unit
26
outputs a VSREQ signal to the video controller
27
as shown in
FIG. 13C
, and also turns off the clutch
24
to stop driving the roller
5
as shown in FIG.
13
H. On the other hand, after the controller
27
expands the image information sent from the external equipment
31
into a dot image and then completes preparation for outputting a VDO signal, the controller
27
confirms that the VSREQ signal in
FIG. 13C
is TRUE. Then, the controller
27
sets a VSYNC signal TRUE as shown in FIG.
13
D. In synchronism with such an operation, after elapsing a time Tv as shown in
FIG. 13E
, the controller
27
starts to output the VDO signal as image data corresponding to one page.
At this time, the print control unit
26
turns on a resist roller clutch
25
after elapsing a time T
3
from rise of the VSYNC signal as shown in
FIG. 13I
, and drives the resist rollers
6
. The rollers
6
are driven for a time T
4
as shown in
FIG. 13I
, i.e., until a trailing edge of the recording paper sheet
3
passes through the rollers
6
. During the time T
4
, the print control unit
26
drives the semiconductor laser
13
according to the VDO signal sent from the video controller
27
.
The semiconductor laser
13
comprises lasers A and B which emit two laser beams, i.e., laser beams A and B respectively. The print control unit
26
drives each laser according to each VDO signal. The two laser beams are reflected by a rotating polygonal mirror
15
and then inclined by a mirror
16
in a scanner unit
7
, and the inclined beams are guided onto each scan path of the photosensitive drum
17
. For example, it is assumed that odd-number lines on the drum
17
are scanned by the laser beam A, while even-number lines are scanned by the laser beam B. As above, when the two laser beams modulated by the respective VDO signals are simultaneously radiated onto the photosensitive drum
17
, a latent image is formed on the drum
17
such that two lines are formed by each beam. By repeating such an operation, the latent image of one page is formed on the drum
17
. A not-shown beam detector is provided on the scan paths of the laser beams A and B and out of an image formation area. The beam detector detects the beams A and B, and generates /BD1 signal and /BD2 signal respectively corresponding to the beams A and B. Modulation timing of the laser beams is controlled on the basis of these two /BD signals.
The latent image formed on the photosensitive drum
17
is developed by the development unit
20
, and then a toner image is transferred onto the recording paper sheet
3
by the transfer charger
21
. After the transfer terminates, the paper
3
is carried to the fixing unit
9
, and the toner image is fixed to the paper
3
. After then, the paper
3
is discharged outward by the paper discharge rollers
11
. In case of continuously printing an image of next page, the print control unit
26
again sets the PRINT signal TRUE after elapsing a time T5 as shown in
FIG. 13B
, and performs the same control as in the printing of the first-page image.
As a test pattern data generation circuit for such the multibeam laser printer, for example, a circuit for generating longitudinal-line test pattern data in a two-beam laser printer will be explained.
FIG. 14
shows a structure of this circuit, and
FIGS. 15A
to
15
J show operation timing of this circuit.
Hereinafter, structure and operation of
FIG. 14
will be explained. A mask signal generation timing setting register
101
is a register which stores therein timing (=counter value) for releasing a /MASK1 signal
124
and a /MASK2 signal
224
necessary in test printing and timing (=counter value) for generating these signals. A storage operation into the resister
101
is performed at the beginning of the test printing.
In
FIG. 14
, in order to obtain horizontal synchronism in the test printing, a /BD1 signal
120
has been inputted in a first phase sync oscillator
102
and a first main-scan counter
103
.
When the /BD1 signal
120
becomes TRUE as shown in
FIG. 15A
, the first main-scan counter
103
is initially reset. Subsequently, the first phase sync oscillator
102
generates an image clock signal (CLK1 signal)
121
in synchronism with the /BD1 signal
120
as shown in FIG.
15
B. The CLK1 signal
121
is inputted to the first main-scan counter
103
and also to a counter
106
for generating test pattern data. Since the counter
103
counts the number of clock pulses, a first main-scan counter value
122
increases as time elapses. By a first comparator
104
, the value
122
is compared with a counter value
123
for releasing a mask set in the mask signal generation timing setting register
101
. On the other hand, a value of the counter
106
at this time is kept “0”, because a /writing inhibition signal
126
is TRUE and thus the counter
106
is continued to be cleared.
Subsequent to the /BD1 signal
120
, a /BD2 signal
220
changes its state from FALSE to TRUE as shown in FIG.
15
F. Thus, in the same manner as in the above first main-scan counter
103
, a second main-scan counter
203
is reset, a second phase sync oscillator
202
generates a second image clock pulse signal (CLK2 signal)
221
as shown in
FIG. 15G
, and the counter
203
counts the number of clock pulses. Even in a second comparator
204
, a mask release value
223
of the laser B and a second main-scan counter value
222
are compared with each other. As a result, while the value
222
is smaller than the value
223
, the /MASK2 signal
224
is kept TRUE.
When the first main-scan counter value
122
reaches the mask release value, a mask of the laser A is released as shown in
FIG. 15C
, and the /MASK1 signal
124
is inputted to a gate
105
.
At this time, when a /TOPE signal
125
being FALSE is inputted to the gate
105
, the four-bit first counter
106
starts counting

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