U.S. patent application number 09/443718 was filed with the patent office on 2001-11-22 for correction control for image forming apparatus and method.
Invention is credited to OHKI, MAKOTO.
Application Number | 20010043258 09/443718 |
Document ID | / |
Family ID | 18246862 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010043258 |
Kind Code |
A1 |
OHKI, MAKOTO |
November 22, 2001 |
CORRECTION CONTROL FOR IMAGE FORMING APPARATUS AND METHOD
Abstract
An image processing apparatus capable of color image formation
with a plurality of color components, which solves a problem of
increment of processing time in monochrome image formation due to
correction on image formation conditions with predetermined patch
formation. For this purpose, in case of monochrome image formation,
even if a tonality control request flag is set, an image formation
sequence is started without performing tonality control. Thus
processing time can be reduced in monochrome image formation.
Inventors: |
OHKI, MAKOTO; (MISHIMA-SHI,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
18246862 |
Appl. No.: |
09/443718 |
Filed: |
November 19, 1999 |
Current U.S.
Class: |
347/115 ;
347/116; 347/132; 347/232; 399/301; 399/38; 399/39; 399/40; 399/46;
399/49 |
Current CPC
Class: |
H04N 1/6033 20130101;
G03G 15/0131 20130101; G06K 15/12 20130101; G03G 15/5058 20130101;
G06K 2215/0094 20130101; G03G 2215/00063 20130101; B41J 2/525
20130101; G03G 2215/0177 20130101; G03G 15/01 20130101; G03G
2215/00059 20130101 |
Class at
Publication: |
347/115 ;
347/116; 347/132; 347/232; 399/38; 399/39; 399/40; 399/46; 399/49;
399/301 |
International
Class: |
B41J 002/385; G03G
015/01; G01D 015/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 1998 |
JP |
10-331721 |
Claims
What is claimed is:
1. An image processing apparatus for forming a color image with a
plurality of color components, comprising: input means for
inputting image data; image formation means for performing image
formation based on said image data; correction means for correcting
image formation conditions in said image formation means; and
control means for avoiding correction by said correction means if
monochrome image formation is performed by said image formation
means.
2. The image processing apparatus according to claim 1, wherein
said correction means further comprises: pattern formation means
for forming a predetermined pattern by said image formation means;
and detection means for detecting pattern information of said
pattern, and wherein said correction means corrects the image
formation conditions based on said pattern information detected by
said detection means.
3. The image processing apparatus according to claim 2, wherein
said correction means forms a predetermined tonality pattern for
each color by said pattern formation means, and detects a density
of said tonality pattern by said detection means.
4. The image processing apparatus according to claim 3, wherein
said correction means corrects a color balance by generating a
look-up table to perform tonality correction for each color based
on the density of said tonality pattern detected by said detection
means.
5. The image processing apparatus according to claim 2, wherein
said correction means forms a predetermined pattern in a
predetermined position for each color by said pattern formation
means, and detects a formation position of said pattern by said
detection means.
6. The image processing apparatus according to claim 5, wherein
said correction means corrects an image formation position for each
color based on the formation position of said pattern detected by
said detection means.
7. The image processing apparatus according to claim 1, further
comprising designation means for inputting image formation
designation, wherein said control means determines whether or not
monochrome image formation is to be performed by said image
formation means based on the image formation designation by said
designation means.
8. The image processing apparatus according to claim 1, wherein
said control means determines whether or not monochrome image
formation is to be performed by said image formation means by
analyzing an image feature of said image data inputted by said
input means.
9. The image processing apparatus according to claim 1, wherein
said correction means corrects said image formation conditions at
predetermined timing.
10. The image processing apparatus according to claim 1, wherein
said input means reads light reflected from an original image and
inputs an image signal.
11. The image processing apparatus according to claim 1, wherein
said image formation means forms a black-and-white image.
12. The image processing apparatus according to claim 1, wherein
said image formation means forms an image by an electrophotographic
method.
13. The image processing apparatus according to claim 2, wherein
said image formation means includes: latent image formation means
for forming an electrostatic latent image on an image holder;
developing means for developing said electrostatic latent image
with developing agents in plural colors to obtain toner images; and
transfer means for plane-sequentially transferring said toner
images in plural colors onto a printing medium held by a medium
holder.
14. The image processing apparatus according to claim 13, wherein
said pattern formation means forms said predetermined pattern on
said image holder.
15. The image processing apparatus according to claim 13, wherein
said pattern formation means forms said predetermined pattern on
said medium holder.
16. The image processing apparatus according to claim 13, wherein
said pattern formation means forms said predetermined pattern on
said printing medium.
17. The image processing apparatus according to claim 2, wherein
said image formation means includes: latent image formation means
for forming an electrostatic latent image on a first image holder;
developing means for developing said electrostatic latent image
with developing agents in plural colors to obtain toner images;
first transfer means for transferring said toner images in plural
colors onto a second image holder; and second transfer means for
transferring said toner images on said second image holder onto a
printing medium held by a medium holder.
18. The image processing apparatus according to claim 17, wherein
said pattern formation means forms said predetermined pattern on
said first image holder.
19. The image processing apparatus according to claim 17, wherein
said pattern formation means forms said predetermined pattern on
said second image holder.
20. The image processing apparatus according to claim 17, wherein
said pattern formation means forms said predetermined pattern on
said medium holder.
21. The image processing apparatus according to claim 17, wherein
said pattern formation means forms said predetermined pattern on
said printing medium.
22. The image processing apparatus according to claim 2, wherein
said image formation means includes: latent image formation means
for forming an electrostatic latent image on a plurality of image
holders; developing means for developing said electrostatic latent
image on the plurality of image holders with developing agents in
different colors to obtain toner images; and transfer means for
plane-sequentially transferring said toner images in different
colors onto a printing medium held by a medium holder.
23. The image processing apparatus according to claim 22, wherein
said pattern formation means forms said predetermined pattern on
said respective plurality of image holders.
24. The image processing apparatus according to claim 22, wherein
said pattern formation means forms said predetermined pattern on
said medium holder.
25. The image processing apparatus according to claim 22, wherein
said pattern formation means forms said predetermined pattern on
said printing medium.
26. The image processing apparatus according to claim 12, wherein
said image formation means forms a color image with yellow,
magenta, cyan and black toner.
27. An image processing method in an image processing apparatus
having image formation means for forming a color image with a
plurality of color components, said method comprising: an input
step of inputting image data; a determination step of determining
whether or not monochrome image formation is to be performed based
on said image data; a correction step of correcting image formation
conditions in said image formation means; and an image formation
step of performing image formation based on said image data by said
image formation means, wherein if it is determined at said
determination step that the monochrome image formation is to
performed, said correction step is not performed.
28. The image processing method according to claim 27, wherein at
said correction step, a predetermined pattern is formed by said
image formation means, pattern information of said pattern is
detected, and the image formation conditions are corrected based on
said detected pattern information.
29. The image processing method according to claim 28, wherein at
said correction step, a color balance is corrected by forming a
predetermined tonality pattern for each color, detecting a density
of said tonality pattern, and generating a look-up table to perform
tonality correction based on said density.
30. The image processing method according to claim 28, wherein at
said correction step, said predetermined pattern is formed in a
predetermined position for each color, a formation position of said
pattern is detected, and an image formation position for each color
is corrected based on said formation position.
31. The image processing method according to claim 27, further
comprising a designation step of inputting image formation
designation, wherein at said determination step, it is determined
whether or not monochrome image formation is to be performed based
on said image formation designation.
32. The image processing method according to claim 27, wherein at
said determination step, it is determined whether or not monochrome
image formation is to be performed by analyzing an image feature of
said input image data.
33. A recording medium containing a control program capable of
forming a color image with a plurality of color components, wherein
said control program including: code of input process for inputting
image data; code of determination process for determining whether
or not monochrome image formation is to be performed based on said
image data; code of correction process for correcting image
formation conditions in image formation means; and code of image
formation process for performing image formation based on said
image data by said image formation means, wherein if it is
determined at said determination process that the monochrome image
formation is to be performed, said correction process is not
performed.
34. A recording medium containing a control program capable of
forming a color image with a plurality of color components, wherein
said control program including: code of determination process for
determining whether or not an object job relates to monochrome
image formation; and code of control process for avoiding execution
of apparatus optimization processing in an image formation
apparatus to perform said job, if it is determined as a result of
determination at said determination process that said job relates
to the monochrome image formation.
35. The recording medium according to claim 34, wherein said
apparatus optimization processing is optimization of density
representation characteristic.
36. The recording medium according to claim 34, wherein said
apparatus optimization processing is optimization of image
formation position for each color component.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image processing
apparatus, an image processing method and a recording medium, and
more particularly, to an image processing apparatus, an image
processing method and a recording medium for color image formation
with a plurality of color components.
[0003] 2. Description of Related Art
[0004] Generally, a color image formation processing apparatus such
as a color copier, a color printer or the like, for color image
formation by using an electrophotographic printing method and the
like, performs specific control which is not performed in a
monochrome copier or printer.
[0005] Generally, to form a full color image in the color image
formation apparatus, yellow (Y), magenta (M), cyan (C) and black
(K) color plane are formed, and the respective planes are finally
overlaid on a print sheet as a transfer material. The quality of
formed image greatly varies depending on the color balance and
relative positional precision of each plane.
[0006] Accordingly, in the electrophotographic color image
formation apparatus, various controls are performed to constantly
obtain image quality at a predetermined level. For example,
feedforward control is performed to preset a development contrast
potential based on the environmental information such as external
temperature/humidity for obtaining an optimum development
characteristic, or feedback control is performed to actually form a
development toner image (hereinafter referred to as a "patch") on
an electrostatic drum or the like, then perform self-diagnostics on
the developing characteristic by detecting the density of the toner
image, and feed back the diagnosis to tonality control parameters.
Such control improves the quality of formed image.
[0007] However, upon feedback control by self-diagnostics as
described above, as the settings of the various tonality control
parameters are changed by actually forming a patch or the like and
detecting it, a predetermined period of processing time is
required.
[0008] Further, as the feedback control is most effective when it
is performed immediately before actual image formation, the
feedback control is performed upon occurrence of an image formation
start signal such as a copy start signal, and an actual image
formation sequence such as copying is performed after the
completion of the feedback control. However, if the feedback
control is always performed immediately before the image formation
sequence, a fast copy time (FCOT) as a period between the
depression of a copy key to the discharge of a copy image is
prolonged.
[0009] Accordingly, in the conventional color image formation
apparatus, to minimize the necessary number of execution of
feedback control, the following limitation is posed to the
execution of feedback control. For example, in a case where the
number of output images exceeds a preset number of pages, or the
surrounding environment such as temperature/humidity changes to a
value equal to a predetermined value or greater, otherwise, in a
case where image output has not been performed for a predetermined
period or longer, an execution request indicative of execution of
feedback control is issued. Only if the execution request is
issued, the feedback control by self-diagnostics is performed.
[0010] However, the above conventional color image formation
apparatus has the following problem.
[0011] As described above, the color image formation apparatus
having a plurality of developing units can form and output a
monochrome image such as a black-and-white image. However, as the
feedback control by self-diagnostics is also performed in
monochrome image formation, the FCOT is greatly prolonged even in
monochrome image copy output. As the operability is greatly
degraded, the color image formation apparatus cannot be
satisfactorily used in a monochrome image formation.
SUMMARY OF THE INVENTION
[0012] The present invention has been made to solve the above
problem, and has its object to provide an image processing
apparatus capable of color image formation, an image processing
method and a recording medium, which reduce processing time in
monochrome image output.
[0013] According to one aspect of the present invention, the
foregoing object is attained by providing an image processing
apparatus for forming a color image with a plurality of color
components, comprising: input means for inputting image data; image
formation means for performing image formation based on the image
data; correction means for correcting image formation conditions in
the image formation means; and control means for avoiding
correction by the correction means if monochrome image formation is
performed by the image formation means.
[0014] Further, the correction means further comprises: pattern
formation means for forming a predetermined pattern by the image
formation means; and detection means for detecting pattern
information of the pattern, and the correction means corrects the
image formation conditions based on the pattern information
detected by the detection means.
[0015] For example, the correction means forms a predetermined
tonality pattern for each color by the pattern formation means, and
detects a density of the tonality pattern by the detection means.
At that time, the correction means corrects a color balance by
generating a look-up table to perform tonality correction for each
color based on the density of the tonality pattern detected by the
detection means.
[0016] For example, the correction means forms a predetermined
pattern in a predetermined position for each color by the pattern
formation means, and detects a formation position of the pattern by
the detection means. At that time, the correction means corrects an
image formation position for each color based on the formation
position of the pattern detected by the detection means.
[0017] Further, another object of the present invention is to
provide a printer driver having a novel function.
[0018] According to another aspect of the present invention, the
foregoing object is attained by providing a recording medium
containing a control program capable of forming a color image with
a plurality of color components, wherein the control program
including: code of determination process for determining whether or
not an object job relates to monochrome image formation; and code
of control process for avoiding execution of apparatus optimization
processing in an image formation apparatus to perform the job, if
it is determined as a result of determination at the determination
process that the job relates to the monochrome image formation.
[0019] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same name or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention and, together with the description, serve to explain
the principles of the invention.
[0021] FIG. 1 is a schematic cross sectional view of an image
formation apparatus according to a first embodiment of the present
invention;
[0022] FIG. 2 is a block diagram showing the construction of an
image processing unit 20 of the first embodiment;
[0023] FIG. 3 is a flowchart showing tonality control according to
the first embodiment;
[0024] FIG. 4 is a flowchart showing the tonality control according
to the first embodiment;
[0025] FIG. 5 is a schematic cross sectional view of the image
formation apparatus according to a second embodiment of the present
invention;
[0026] FIG. 6 is a schematic cross sectional view showing the
structure of the image formation unit of the second embodiment;
[0027] FIG. 7 is a perspective view showing the structure of an
image exposure part of the image formation apparatus of the second
embodiment;
[0028] FIG. 8 is a perspective view showing a mechanical
registration correction mechanism in the image exposure part of the
second embodiment;
[0029] FIG. 9 is a flowchart showing registration correction
processing. according to the second embodiment; and
[0030] FIG. 10 is a flowchart showing the registration correction
execution control according to the second embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Preferred embodiments of the present invention will now be
described in detail in accordance with the accompanying
drawings.
[0032] <First Embodiment>
[0033] FIG. 1 is a schematic cross sectional view showing the
structure of an image formation apparatus according to a first
embodiment of the present invention. The image formation apparatus
performs full-color image formation by an electrophotographic
method based on an image signal obtained by reading an
original.
[0034] At an operation unit 40, when a copy key (not shown) is
depressed, an original 35 placed on a glass plate 31 is irradiated
with light outputted from an exposure lamp 32a. Then light
reflected from the original 35 is guided by a plurality of mirrors
32b and a lens 33, and forms an image on a full color sensor 34
having a 3-line CCD.
[0035] The full color sensor 34 comprises CCD line sensors of red
(R), green (G) and blue (B) colors arranged a predetermined
distance away from each other in a subscanning direction. Each line
sensor has an array of photoreceptors. The full color sensor 34
separates the reflection light image entered from the original 35
into a plurality of pixels by using a plurality of photoelectric
transducers, and generates photoelectric conversion signals (color
separation image signals) in accordance with the densities of the
respective pixels.
[0036] The RGB image signals generated by the full color sensor 34
are sent to an image processing unit 20, then subjected to image
processing such as tonality correction to be described later and
PWM, and sent, as an image signal comprising magenta (M), cyan (C),
yellow (Y) and black (K) color components, to an exposure device
103.
[0037] Reference numeral 1 denotes an image holder i.e., an
electrostatic drum which rotates in an arrow direction in FIG. 1.
Image formation means is arranged around the electrostatic drum.
The image formation means may have an arbitrary construction,
however, in this embodiment, has a primary charger 2 to uniformly
charge the surface of the electrostatic drum 1, the exposure device
103 to expose the electrostatic drum 1 and form electrostatic
latent images, a rotary developer 3a to develop the electrostatic
latent images on the electrostatic drum into visible Y, M and C
color toner images, and a fixed developer 3k containing a K color
developing agent.
[0038] The exposure device 103 has a laser driver 102 to control
laser beam emission by a semiconductor laser. The exposure device
103 forms electrostatic latent images on the electrostatic drum 1
by irradiating the electrostatic drum with optical images obtained
by color-separating a color image or images corresponding to the
optical images.
[0039] The rotary developer 3a holds three developers 3y, 3m and 3c
respectively containing a Y color developing agent, an M color
developing agent and a C color developing agent, around the
rotatably-supported approximately cylindrical body of the rotary
developer 3a. When the body of the rotary developer 3a rotates, a
developer, containing a developing agent of a color corresponding
to an electrostatic latent image on the electrostatic drum 1, is
conveyed to a developing position opposite to the periphery of the
electrostatic drum 1, to develop the electrostatic latent image,
thus visualizing the latent image as a toner image. Similarly, an
electrostatic latent image corresponding to the K color is
developed by the fixed developer 3k and is visualized.
[0040] Note that the image formation apparatus of the present
embodiment also performs monochrome image formation by using only
the fixed developer 3k as well as color image formation using the
rotary developer 3a and the fixed developer 3k.
[0041] The toner image formed on the electrostatic drum 1 is
transferred onto an intermediate drum 30 by a transfer charger 4a
in a position opposite to the electrostatic drum 1 via the
intermediate drum 30. This operation is repeated for the other
colors. Thus a full color image of 4 color components is formed on
the intermediate drum 30.
[0042] On the other hand, a print sheet (transfer material) P fed
from a paper feeder (not shown) is electrostatically attracted to a
transfer material holding belt 5. The full color image formed on
the intermediate drum 30 is transferred onto the print sheet P by a
transfer charger 4b, and color-mixture fixed onto the print sheet P
by a fixer 70. The print sheet is discharged to the outside the
apparatus.
[0043] Numeral 6 denotes a cleaner to clean residual toner on the
electrostatic drum 1.
[0044] Note that numeral 80 denotes a reflective type optical
sensor (hereinafter referred to as a "density sensor") to detect
the density of a patch pattern formed on the intermediate drum
30.
[0045] FIG. 2 is a block diagram showing the construction of the
image processing unit 20.
[0046] The RGB image signals outputted from the full color sensor
34 are converted by an A/D converter 202 for respective color
components into, e.g., 8-bit (0-255 level: 256 levels) RGB digital
signals. The RGB digital signals are inputted into a shading
corrector 203. To remove variation in sensitivities of the
respective photoreceptors arrayed in the full color sensor 34,
general shading correction is performed on the RGB digital signals
to optimize the gain in correspondence with the respective
photoreceptors.
[0047] Note that computer-generated (monochrome or color) image
data displayed on, e.g., a CRT display, is inputted from an
external device (not shown) such as a computer via an external
input interface 213 in accordance with necessity.
[0048] A LOG converter 204, having a look-up table (LUT) comprising
a ROM or the like, converts the input RGB luminance signals into
CMY density signals.
[0049] A masking UCR unit 205 extracts a black component signal K
from the CMY image signals, and performs matrix calculation on the
CMYK image signals to correct color mixture in printing color
materials in a printer. Further, the masking UCR unit 205 outputs
the 8-bit M, C, Y and K color component plane-sequential image
signals upon each reading operation of a reader. Note that matrix
coefficients used in the matrix calculation are set by a CPU
209.
[0050] An LUT unit 206 performs density correction on the input
CYMK image signals for respective color components by using a gamma
look-up table (.gamma.-LUT) so as to adjust the image signals to an
ideal tonality characteristic of the printer. Note that the
.gamma.-LUT comprises a RAM or the like, and the contents of the
.gamma.-LUT are set by the CPU 209.
[0051] A pulsewidth modulator (PWM) 207 outputs pulse signals
having pulsewidths corresponding to the levels of the image signals
inputted from the LUT unit 206. As described above, the pulse
signals are inputted into the laser driver 102 to drive the
semiconductor laser, in the exposure device 103.
[0052] Numeral 208 denotes a pattern generator holding
predetermined patch pattern information for density correction in
the present embodiment. The pattern generator 208 directly outputs
the information to the PWM 207 for patch detection processing to be
described later.
[0053] Note that numeral 210 denotes a ROM holding a control
program described later with reference to the flowcharts. The
control program is read onto a RAM 211 and executed by the CPU 209.
The RAM 211 serves as a work area for the CPU 209.
[0054] In the present embodiment, as tonality control to maintain
the quality of formed full color image, especially tint and
gradation, a plurality of predetermined patch patterns are
generated for the respective CMYK colors on the intermediate drum,
and the .gamma.-LUT in the LUT unit 206 is generated based on
density values detected by the density sensor 80.
[0055] FIG. 3 is a flowchart showing patch formation control for
controlling formation of tonality patch upon color image formation
or monochrome image formation.
[0056] First, when the copy key or the like is depressed at the
operation unit 40 and a print start signal is inputted at arbitrary
timing, then the CPU 209 receives the signal, and determines
whether or not a flag (tonality control request flag) is set at a
tonality control request address ensured on the RAM 211, i.e.,
whether or not the value of the flag is "1" (step S201).
[0057] If the value of the flag is "1", the CPU 209 issues a
tonality control execution request signal, and executes tonality
control (step S202). Then, the tonality control request flag is
reset (set S203) and then an image formation sequence is performed
(step S204).
[0058] On the other hand, if the value of the tonality control
request flag is "0", the image formation sequence is performed
(step S204) without execution of the tonality control, and image
output is performed.
[0059] In the present embodiment, if any of the following
conditions is satisfied, the value of the tonality control request
flag becomes "1", i.e., the tonality control execution request is
issued.
[0060] a. the number of pages of output images after previous
control is over 200
[0061] b. the ambient temperature has changed by 7 degrees or more,
and the ambient humidity has changed by 15% or more
[0062] c. image output has not been performed for 1 hour or
longer.
[0063] Note that variables based on these conditions (the number of
output pages, the ambient temperature/humidity, the elapsed time
and the like) and the tonality control execution request are reset
(step S203) after the execution of tonality control at step
S202.
[0064] In the present embodiment, the tonality patches formed on
the intermediate drum 30 are 8 patches based on predetermined image
signal level (0-255 level). The respective color patches are
sequentially transferred onto the intermediate drum 30. When the
final color patch has been transferred, the density sensor 80
detects the densities of the respective patches. Note that the
output voltage of the density sensor 80 ranges from 0 to 5 V. The
output voltage is A/D converted to represent the density range
0-2.0 by 10 bits (0-1023 level).
[0065] By generating .gamma.-LUTs for the respective colors based
on the obtained density information, desired density tonality
characteristics can be maintained for the respective colors.
Accordingly, in case of color mixture, excellent color balance can
be maintained.
[0066] Note that the processing speed of the image formation
apparatus of the present embodiment is 117 mm/sec. The diameter of
the electrostatic drum 1 is 62 mm, and that of the intermediate
drum is 186 mm.
[0067] In the present embodiment, to form the tonality patches on
the intermediate drum 30, first, the intermediate drum 1 is rotated
once to perform stabilization processing on the electrostatic drum
1 and the intermediate drum 30. Then, to perform actual tonality
patch formation for 4 colors and density measurement, the
intermediate drum 30 is rotated 5 times. Further, to perform
postprocessing such as cleaning on the electrostatic drum 1 and the
intermediate drum 30, the intermediate drum 30 is rotated once. In
this manner, to form the tonality patches, the intermediate drum 30
must be rotated 7 times, and it takes about 35 sec to complete this
rotation control.
[0068] In the image formation apparatus of the present embodiment,
image formation using, e.g., black color, i.e., black-and-white
copying is possible. Generally, the FCOT (elapsed time from the
depression of the copy key to the discharge of copy image) in
black-and-white copying is about 14 sec. Accordingly, if the
above-described tonality control (S202) is performed in
black-and-white copying, the FCOT is about 50 sec, almost 4 times
of that in normal copying. In comparison with the FCOT in normal
color copying which is about 30 sec, the FOCT is nearly twice. That
is, in black-and-white copying characterized by FOCT shorter than
that in color copying, the operability is very poor.
[0069] In the present embodiment, upon depression of the copy key,
the execution of tonality control is controlled in accordance with
color image formation or monochrome image formation, to maintain a
short FCOT in monochrome image formation.
[0070] FIG. 4 is a flowchart showing the patch formation control in
a case where formation of the tonality patch patterns is controlled
in consideration of monochrome image formation.
[0071] First, when the copy key or the like is depressed at the
operation unit 40 and the print start signal is inputted at
arbitrary timing, the CPU 209 receives the signal, and determines
whether the print start signal is a color image formation request
or monochrome image formation request (step S301). Note that the
color/monochrome image formation request may be designated by a
user with keys (not shown) at the operation unit 40, or it may be
arranged such that prescanning is performed on an original and it
is determined whether or not the original is a color original or
monochrome original. In a case where image formation is performed
based on an image signal inputted from the external device such as
a computer via the external input I/F 213, it may be determined
whether or not the image signal represents a monochrome image based
on header information added to the image signal or by analyzing the
image signal.
[0072] If the print start signal is a color image formation
request, the tonality control request flag on the RAM 211 is
determined (step S302). If the value of the flag is "1", the
tonality control is performed (step S303). Then the tonality
control request flag is reset (step S304) and the image formation
sequence is performed (step S305).
[0073] On the other hand, if it is determined at step S301 that the
print start signal is a monochrome image formation request and if
it is determined at step S302 that the value of the tonality
control request flag is "0", the image formation sequence is
performed (S305) without tonality control, and image output is
performed.
[0074] That is, in the present embodiment, in case of monochrome
image formation, even if the tonality control request flag is set,
the tonality control is not performed. This avoids increment of the
FCOT in monochrome image formation.
[0075] Note that in the present embodiment, the tonality control is
performed by forming the tonality patches on the intermediate drum
30, however, the tonality control of the present invention is not
limited to this arrangement. For example, the tonality patches may
be formed on the electrostatic drum 1, or it may be arranged such
that the tonality patches are formed on the print sheet P and the
densities of the tonality patches are detected by reading the print
sheet P. Further, as long as the image formation apparatus has a
transfer belt, the tonality patches may be formed on the transfer
belt. Otherwise, the tonality patches may be formed in plural
positions including the intermediate drum 30 for tonality control.
Further, the present invention is applicable to an image formation
having a transfer drum which directly holds the transfer sheet P
without the intermediate drum 30 and performs transfer, or an image
formation apparatus having plural electrostatic drums.
[0076] As described above, according to the present embodiment, in
an image formation apparatus capable of color/monochrome image
formation by an electrophotographic method, tonality control is not
performed in monochrome image formation. Thus, increment of FCOT of
monochrome image formation can be prevented.
[0077] <Second Embodiment>
[0078] Next, a second embodiment of the present invention will be
described below.
[0079] FIG. 5 is a schematic cross sectional view of the image
formation apparatus according to the second embodiment. The image
formation apparatus has 4 image formation units, YU, MU, CU and KU,
for color or monochrome image formation. That is, laser beams (L1
to L4) based on the respective color components of original image
read by the reader (not shown) are emitted from the exposure device
103, and scan on electrostatic drums in the image formation unit
YU, MU, CU and KU for the respective colors.
[0080] These image formation units YU, MU, CU and KU have a
construction as shown in FIG. 6. In FIG. 6, each image formation
unit has the rotatably-supported electrostatic drum 1. The primary
charger 2, a developer 3, the transfer charger 4, the cleaner 6 and
a pre-exposure device 7 are provided around the electrostatic drum
1. The transfer material holding belt 5 as transfer material
conveyance means is provided below the electrostatic drum 1. The
transfer material holding belt 5 conveys the print sheet P fed from
a paper feeder 50 to the position of the transfer charger 4 of each
respective image formation unit.
[0081] Hereinbelow, the image formation process in the image
formation apparatus according to the second embodiment will be
described. First, in each image formation unit, the primary charger
2 negatively charges the electrostatic drum 1 uniformly, then the
operation of the laser beam exposure device 103 as image exposure
means forms an electrostatic latent image corresponding to a
color-separated image exposure pattern. The electrostatic latent
images are developed with respective yellow (Y), magenta (M), cyan
(C) and black (K) toner, thus visualized.
[0082] More specifically, each of the developers 3 for the
respective colors has a developing sleeve which holds
negatively-charged color toner and conveys the toner to a
developing area near the electrostatic drum 1. The toner is
attached to the electrostatic latent image formed on the
electrostatic drum 1 by a developing electric field formed by a
developing bias voltage applied to the developing sleeve and a
surface potential of the electrostatic drum 1 (negative
development). Thus, the electrostatic latent image is visualized as
a toner image.
[0083] The respective visible images are sequentially transferred
onto the print sheet P held on the transfer material holding belt 5
by the operation of the transfer charger 4, and a full color image
is formed on the print sheet P. When the image formation has been
completed, the print sheet P is removed from the transfer material
holding belt 5 and sent to the fixer 70. The transferred toner
images of the full color image are fixed onto the print sheet P at
once. Thus a desired full color image is obtained.
[0084] Then the print sheet P is discharged onto a discharge tray
(not shown). In each image formation unit, the cleaner 6 removes
residual toner on the electrostatic drum 1, then the pre-exposure
device 7 discharges the residual surface potential on the
electrostatic drum 1, in preparation for subsequent latent image
formation.
[0085] In this manner, in the image formation apparatus having the
plural image formation units, as images in different colors are
sequentially transferred onto the same print sheet P, the transfer
image positions in the respective image formation units might shift
from an ideal reference position. For example, if such positional
shift occurs in color image formation, respective color toner
images are overlaid in relatively shifted positions. The positional
shift causes difference in tint and further causes color shift,
which greatly degrades the image quality.
[0086] It is considered that the above color shift occurs due to
the following factors:
[0087] a. shift in relative writing start timing in each image
formation unit
[0088] b. shift in attachment angle of optical scanning system
[0089] c. shift in scanning line length due to difference in
optical path length from the optical scanning system to the
electrostatic drum in the respective image formation units.
[0090] In the image formation apparatus of the second embodiment,
to prevent the occurrence of color shift, so-called registration
correction is performed. Next, a construction to perform the
registration correction in the image formation apparatus of the
second embodiment will be described with reference to FIGS. 7 and
8. FIG. 7 is a perspective view showing the structure of an image
exposure part of the image formation apparatus. FIG. 8 is a
perspective view showing a mechanical registration correction
mechanism in an optical scanning system of the image exposure
part.
[0091] As shown in FIG. 8, among reflection mirrors provided in the
middle of the optical path in each image formation unit, a pair
mirror 200, having mirrors 106 and 107 provided with a
predetermined distance therebetween and at a predetermined angle,
is adjusted in arrows E' and F' directions with respect to the
apparatus main body, to correct the shift amount.
[0092] That is, by moving the pair mirror 200 in the arrow E'
direction, the optical path length of a scanning line 102 can be
changed without changing the position of the scanning line 102
image-formed on the electrostatic drum 1. Further, by moving the
pair mirror 200 in the arrow F' direction, the position and angle
of image formation on the electrostatic drum 1 can be corrected
without changing the optical path length of the scanning line 102.
Note that the movement of the pair mirror 200 in the arrows E' and
F' directions can be made by respectively controlling actuators 27
and 28.
[0093] In FIG. 7, numerals 315 and 316 denote registration marks
transferred onto the print sheet P or the transfer material holding
belt 5. The registration marks are detected by sensors LSF and LSR.
The sensors LSF and LSR comprise sensors (CCD sensors) 313 and 314
for reading the registration marks 315 and 316 and optical systems
309 and 310 for guiding images of the registration marks 315 and
316 to the sensors 313 and 314. That is, the amount of current
positional shift is calculated based on signals obtained by reading
the registration marks 315 and 316 transferred on to the transfer
material holding belt 5 by the sensors (CCD sensors) 313 and
314.
[0094] FIG. 9 is a flowchart showing registration correction
processing according to the second embodiment. First, the
registration marks 315 and 316 are formed in each image formation
unit (step S901). The sensors LSR and LSF read the registration
marks 315 and 315 transferred onto the transfer material holding
belt 5 (step S902). The amount of positional shift of the image
formation unit is calculated based on the read values (step S903),
and the amount of registration correction is calculated (step
S904). Then, correction is performed based on the amount of
registration correction. For example, by correcting tilting shift
by using the actuator 28 (step S905), the positional shift due to
the above factor b can be corrected. Further, by correcting the
magnification shift (shift in optical path length) by using the
actuator 27 (step S906), the positional shift due to the above
factor c can be corrected.
[0095] Further, in addition to the mechanical correction at steps
S905 and S906, electrical correction at steps S907 and S908,
correction on top margin and left margin by adjusting scanning
timing, can correct the positional shift due to the above factor
a.
[0096] Note that in the present embodiment, if any of the following
conditions is satisfied, a registration correction request is
issued.
[0097] a. when time elapsed since the power-down of the apparatus
is 30 minutes; when the elapsed time is 1 hour; thereafter,
whenever 1 hour has elapsed
[0098] b. after restart due to occurrence of so-called jam such as
print sheet jam.
[0099] Note that in the second embodiment, upon execution of the
registration correction, it takes about 30 sec to complete
calculation processing, mirror position adjustment and the
like.
[0100] In the 4-drum image formation apparatus of the second
embodiment, monochrome image formation, i.e., the black-and-white
copying can be performed. As in the case of color copying, the FCOT
(elapsed time from the depression of copy key to the discharge of
copy image) in black-and-white copying is about 15 sec in normal
operation. Since color shift does not occur in black-and-white
copying, registration correction is not required. However, if
registration correction is performed even in black-and-white
copying based on the above conditions a and b, the FCOT greatly
increases.
[0101] In the second embodiment, upon depression of the copy key,
the execution of registration correction is controlled in
accordance with color image formation or monochrome image
formation, for maintaining the FCOT in monochrome image
formation.
[0102] FIG. 10 is a flowchart showing the registration correction
control in consideration of monochrome image formation. First, when
the copy key or the like is depressed at the operation unit 40 and
the print start signal is inputted at arbitrary timing, the CPU
(not shown) receives the signal, and determines whether the print
start signal is a color image formation request or a monochrome
image formation request (step S601). Note that the color/monochrome
image formation request may be designated by the user with the keys
(not shown) at the operation unit 40, or it may be arranged such
that prescanning is performed on an original and it is determined
whether or not the original is a color original or monochrome
original.
[0103] If it is determined at step S601 that the print start signal
is a color image formation request, it is determined whether or not
a flag (registration correction request flag) is set at a
registration correction request address ensured on the RAM (not
shown), i.e., the value of the flag is "1" (step S602). If the
value of the flag is "1", the CPU issues a registration correction
execution request signal, and performs registration correction
(step S603). Then the registration correction request flag is reset
(step S604), and the image formation sequence is performed (step
S605).
[0104] On the other hand, if it is determined at step S601 that the
print start signal is a monochrome image formation request, and if
the value of the registration correction request flag is "0", the
image formation sequence is performed (step S605) without execution
of the registration correction, and image output is performed.
[0105] In the second embodiment, upon formation of a monochrome
image, even if the registration correction request flag is set,
registration correction is not performed. This avoids increment of
the FCOT in monochrome image formation.
[0106] Note that in the second embodiment, the registration
correction is performed on the transfer material holding belt 5,
however, the registration correction control of the present
invention is not limited to the above arrangement. For example, the
present invention is applicable to registration correction for
respective colors in an image formation apparatus having only one
image formation unit.
[0107] As described above, according to the second embodiment, in
an image formation apparatus capable of color/monochrome image
formation by an electrophotographic method, registration correction
is not performed in monochrome image formation. Thus, increment of
the FCOT in monochrome image formation can be prevented.
[0108] <Other Embodiments>
[0109] The present invention can be applied to a system constituted
by a plurality of devices (e.g., a host computer, an interface, a
reader and a printer) or to an apparatus comprising a single device
(e.g., a copy machine or a facsimile apparatus).
[0110] Further, the object of the present invention can be also
achieved by providing a storage medium storing program code for
performing the aforesaid processes to a system or an apparatus,
reading the program code with a computer (e.g., CPU, MPU) of the
system or apparatus from the storage medium, then executing the
program.
[0111] In this case, the program code read from the storage medium
realize the functions according to the embodiments, and the storage
medium storing the program code constitutes the invention.
[0112] Further, the storage medium, such as a floppy disk, a hard
disk, an optical disk, a magneto-optical disk, CD-ROM, CD-R, a
magnetic tape, a non-volatile type memory card, and ROM can be used
for providing the program code.
[0113] Furthermore, besides aforesaid functions according to the
above embodiments are realized by executing the program code which
are read by a computer, the present invention includes a case where
an OS (operating system) or the like working on the computer
performs a part or entire processes in accordance with designations
of the program code and realizes functions according to the above
embodiments.
[0114] Furthermore, the present invention also includes a case
where, after the program code read from the storage medium are
written in a function expansion card which is inserted into the
computer or in a memory provided in a function expansion unit which
is connected to the computer, CPU or the like contained in the
function expansion card or unit performs a part or entire process
in accordance with designations of the program code and realizes
functions of the above embodiments.
[0115] For example, in a case where a printer driver to control a
printer has the above-described function, if it is determined that
an object print job relates to monochrome (e.g., black-and-white)
image formation, the above-described calibration (density
correction optimization processing) and registration adjustment
(optimization processing on image formation position for each color
component) are not performed.
[0116] In this case, even if the need for those optimization is
notified to the printer driver side from the printer side, the
notification is ignored.
[0117] Accordingly, it is necessary to authorize the printer driver
to permit predetermined apparatus optimization.
[0118] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
* * * * *