Multi-color image forming apparatus and method of setting image data for same

An image forming method and an image forming apparatus in which a plurality of kinds of toner images are supported on an image support member, the method comprising the steps of: forming, on the basis of first image data, a first toner image on the image support member with first toner; detecting the first toner image so as to output a detection signal; forming, on the basis of second image data, a second toner image on the image support member with second toner which is different from the first toner; and executing, by an output of the detection signal, a program for setting conditions for forming the second toner image.

BACKGROUND OF THE INVENTION 
The present invention relates to adjustment of image quality in an image 
forming apparatus such as a copying apparatus, a page printer, etc. 
In color copying apparatuses employing an electrophotographic process, 
toner images of primary colors of yellow (Y), magenta and cyan (C) are 
sequentially formed and are placed on each other so as to form a color 
copied image. In the known color copying apparatuses, density of the toner 
image of each color, i.e. state of development by the toner of each color 
is an important factor in determination of color reproducibility (image 
quality). 
Therefore, in the known color copying apparatuses, an AIDC pattern 
(reference toner image for adjusting development density) for the toner of 
each color is produced on a photosensitive member at a predetermined 
timing such that densities of the AIDC patterns are detected by respective 
photoelectric type AIDC sensors. In response of the detection signals, 
setting values of corona charging quantity for the photosensitive member, 
amount of exposure for charge erasing, developing bias voltage, etc. are 
changed in image forming processes of respective colors at the time of 
copying such that image quality is adjusted. 
However, in the known color copying apparatuses, since the AIDC patterns 
corresponding to the toners of Y, M and C, respectively are sequentially 
produced, a long period is required for adjusting image quality, thereby 
resulting in delay in start of copying. Furthermore, the known color 
copying apparatuses have such a drawback that although the AIDC patterns 
occupy a small area, the toners of the respective colors are consumed for 
producing the AIDC patterns. 
SUMMARY OF THE INVENTION 
Accordingly, an essential object of the present invention is, with a view 
to eliminating the above mentioned inconveniences, to minimize consumption 
of toner and reduce period required for adjusting image quality. 
In order to accomplish this object of the present invention, an image 
forming apparatus provided with a plurality of developing means having 
different developing colors for developing latent images on a 
photosensitive member, respectively according to the present invention 
comprises: an image quality adjustment table for storing interrelations of 
image forming characteristics for the respective developing means; wherein 
a density of an image developed by a specific one of the developing means 
is detected such that image forming conditions of the remaining developing 
means are set in accordance with the detected density by using the image 
quality adjustment table. 
The image quality adjustment table stores the interrelations of the image 
forming characteristics of a plurality of the developing means having the 
different developing colors, respectively. A latent image for image 
quality adjustment is formed on the photosensitive member and is developed 
by the specific developing means. By detecting the density of the image 
developed by the specific developing means, an imaging state of the 
specific developing means is detected. By referring to the image quality 
adjustment table, imaging states of the remaining developing means can be 
detected from the imaging state of the specific developing means without 
the need for performing development for image quality adjustment by using 
the remaining developing means. Furthermore, the image forming conditions 
of the remaining developing means are set such that the imaging states of 
the remaining developing means are made proper.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, there is shown in FIG. 1, a copying 
apparatus 1 according to one embodiment of the present invention. At a 
corona charging portion from which exposure light (scanning light) from an 
optical system 27 is intercepted, namely, at an image nonforming portion, 
a latent image APE of an AIDC pattern AP is formed on a surface of a 
photosensitive drum 3 through selective charge erasing by an editing 
eraser 5. When the AIDC pattern AP is produced, a grid voltage VG of a 
corona charger 4 is set to a specific value to change the surface of the 
drum 3 at a predetermined latent image voltage-potential (Vo). 
As shown in FIG. 2, the editing eraser 5 is constituted by an LED array in 
which a number of LEDs 5a are linearly arranged in a holder extending in 
an axial direction of the photosensitive drum 3. The editing eraser 5 is 
arranged to partially erase a latent image or electric charge on the 
photosensitive drum 3 by controlling turning on of the respective LEDs 5a. 
When the latent image APE of the AIDC pattern AP is formed by the editing 
eraser 5, control is performed such that LEDs 5a corresponding to a width 
L1 of the latent image APE are turned off for a period corresponding to a 
length L2 of the latent image APE and turned on during the remaining 
period, while the remaining LEDs 5a held in the ON state. The latent image 
APE is developed into the AIDC pattern AP by developing devices 6 to 9. 
Density of the produced AIDC pattern AP is detected by an AIDC sensor 73. 
The developing devices 6, 7, 8 and 9 contain developers (mixtures of toner 
and carrier) of colors of yellow (Y), magenta (M), cyan (C) and black 
(BK), respectively. In order to control the developers such that toner 
concentrations of these developers are maintained at fixed values at all 
times, toner concentration sensors (ATDC sensors) 71y, 71m, 71c and 71k 
are provided, respectively. The developing devices deposit the above color 
toners (Y), (M), (C) and (BK) in accordance with predetermined bias 
voltages as the well-known conventional developing devices. 
A transfer belt 11 is provided for temporarily holding toner images 
developed on the photosensitive drum 3 by the developing devices 6 to 9 so 
as to transfer (secondary transfer) the toner images onto a copy paper 
sheet P. The transfer belt 11 is trained over a plurality of rollers 12 to 
16 and is supported so as to be rotated counterclockwise (in the direction 
of the arrow M4) while being held in contact with the photosensitive drum 
3 at all times. 
A transfer charger 17 for transferring (primary transfer) the toner images 
onto the transfer belt 11 from the photosensitive drum 3 is provided 
inside the transfer belt 11. Meanwhile, outside the transfer belt 11 are 
provided a transfer charger 20 for secondary transfer, a charge eraser 21 
for separating the copy paper sheet P from the transfer belt 11 and a belt 
cleaner 19 having a fur brush 19a for cleaning an outer surface of the 
transfer belt 11. The fur brush 19a is movably provided so as to be 
selectively brought into pressing contact with the transfer belt 11 at the 
time of cleaning and spaced away from the transfer belt 11. 
Meanwhile, belt mark sensors 72 and 72s for detecting rotational angular 
positions of the transfer belt 11 are fixedly provided along the transfer 
belt 11 between the rollers 15 and 16 and between the rollers 12 and 13, 
respectively. An optical platform glass 28 and a detector 101 for 
detecting size of an original document D placed on the original platform 
glass 28 are provided at an upper face of the copying apparatus 1. 
Furthermore, the optical system 27 is provided at an upper portion of the 
copying apparatus 1. The optical system 27 is substantially constituted by 
a scanner 30, a main lens 35, a mirror device 36 for performing color 
separation exposure, a fixed mirror 37 and a color image sensor 38 and 
scans the original document D a&: the time of forward travel of the 
scanner 30 so as to effect exposure of the photosensitive drum 3. The 
scanner 30 is reciprocatingly provided below the original platform glass 
28 so as to be reciprocated in the forward direction of the arrow M5 and 
in the backward direction of the arrow M6. The main lens 35 is adjusted in 
position in accordance with copying magnification. The fixed mirror 37 is 
provided for guiding to an exposure point on the photosensitive drum 3, 
scanning light L reflected by mirrors attached to the mirror device 36. 
The color image sensor 38 is provided for receiving the scanning light L 
transmitted through the mirrors of the mirror device 36. 
The scanner 30 is constituted by a first slider 31 and a second slider 32. 
The first slider 31 includes an exposure lamp 33 and a mirror 34, while 
the second slider 32 includes mirrors 35a and 35b. The exposure lamp 33 is 
capable of changing its exposure amount in accordance with an applied 
voltage thereto. Completion of backward travel of the scanner 30, namely 
return of the scanner 30 to a reference position (home position) is 
detected by a scanner home switch 74 formed by a photosensor. 
The mirror device 36 has a half mirror 36ND and three filter mirrors 36YB, 
36MG and 36CR. In the half mirror 36ND, ratio of transmission to 
reflection of the scanning light L is 6:4. The half mirror 36ND and the 
filter mirrors 36YB, 36MG and 36CR extend radially from a shaft 36a and 
axially along the shaft 36a in parallel with the shaft 36a so as to be 
circumferentially spaced 90.degree. from each other. Upon rotation of the 
mirror device 36, one of the mirrors 36ND, 36YB, 36MG and 36CR is 
positioned through selective changeover. In the mirror filters 36YB, 36MG 
and 36CR corresponding to toners of colors of Y, M and C, respectively, 
each of color separation filters of blue (B), green (G) and red (R) is 
deposited on a surface of a mirror such that the mirror and each color 
separation filter are formed integrally. 
In exposure scanning for image formation, a reflecting surface of a 
selected one of the half mirror 36ND and the filter mirrors 36YB, 36MG and 
36CR is so positioned as to be inclined clockwise through about 10.degree. 
relative a vertical plane such that the scanning light L is guided to the 
exposure point on the photosensitive drum 3. Meanwhile, in preliminary 
scanning for reading images of the original document D, which is performed 
prior to exposure scanning, the half mirror 36ND is selected and is 
positioned vertically so as to intersect with a direction of incidence of 
the scanning light L at right angles so as to improve modulation transfer 
function (MTF) of the image sensor 38, i.e. image forming power. In order 
to determine a home position of the mirror device 36, a sensor 77 is 
provided for detecting rotational position of the mirror device 36. In 
FIG. 1, the filter mirror 36CR is selected and is positioned at its image 
forming position. 
Hereinbelow, the half mirror 36ND and the filter mirrors 36YB, 36MG and 
36CR may be referred to as "an ND filter, a B filter, a G filter and an R 
filter on the basis of their color separation characteristics, 
respectively or whole of these mirrors may be referred to as "a mirror 
36b". 
On the other hand, an upper paper cassette 42 containing the copy paper 
sheets P and a lower paper cassette 43 containing the copy paper sheets P 
are loaded into a lower portion of the copying apparatus 1. By opening a 
door 41a on a left side face of the copying apparatus 1, a manual paper 
feeding opening 41 for performing manual feed of the copy paper sheets P 
is uncovered. The upper paper cassette 42, the lower paper cassette 43 and 
the manual paper feeding opening 41 are selectively used for paper 
feeding. In the upper and lower paper cassettes 42 and 43, pickup rollers 
44 and 45 for picking up the copy paper sheets P one sheet by one sheet, 
paper size sensors 81 and 82 for detecting size of the copy paper sheets P 
and paper empty sensors 83 and 84 for detecting depletion of the copy 
paper sheets P are provided, respectively. Meanwhile, a manual feed sensor 
87 for detecting insertion of the copy paper sheet P is provided at the 
manual paper feeding opening 41. 
The copy paper sheet P fed from the upper paper cassette 42 is transported 
by paper feeding rollers 47 to timing rollers 46 where the copy paper 
sheet P is set in waiting state. Likewise, the copy paper sheet P fed from 
the lower paper cassette 43 is conveyed by paper feeding rollers 48 and 47 
to the timing rollers 46 where the copy paper sheet P is set in waiting 
state. Meanwhile, the copy paper sheet P inserted into the manual paper 
feeding opening 41 is carried to the timing rollers 46 by manual paper 
feeding rollers 49. In the vicinity of the paper feeding rollers 47, there 
is provided a paper sensor 85 for detecting presence and absence of the 
copy paper sheet P in a paper feeding passage R1 between the paper feeding 
rollers 47 and the timing rollers 46. In the vicinity of the timing 
rollers 46, there is provided a timing sensor 86 for detecting a leading 
edge of the passing copy paper sheet P. 
The copy paper sheet P in waiting state is further transported 
synchronously with the transfer belt 11 upon rotation of the timing 
rollers 46. Thus, secondary transfer of a toner image from the transfer 
belt 11 to the copy paper sheet P is performed at a transfer position. 
Subsequently, the copy paper sheet P is carried to a fixing unit 51 by a 
transport belt 50 having a linear distance corresponding to that of an 
A4-sized copy paper sheet. 
The fixing unit 51 is constituted by an upper roller 52 and a lower roller 
53 so as to fix the toner image on the copy paper sheet P by fusing the 
toner image. The upper roller 52 has heater lamps 54 and 55, while the 
lower roller 53 has a heater lamp 56. Temperature sensors 91 and 92 each 
formed by a thermistor are, respectively, provided in the vicinity of the 
upper and lower rollers 52 and 53. The copy paper sheet P having a desired 
copied image formed thereon by fixing of the toner image is carried to a 
sorter 2 by discharge rollers 57 so as to be ejected onto a copy receiving 
tray 61 or a sorting ben 62 in the sorter 2. A discharge sensor 88 is 
provided in the vicinity of the discharge rollers 57. 
The copying apparatus 1 of this embodiment is provided with a return device 
60 which is used for refixing at the time of copying in OHP mode. The 
return device 60 includes a transport mechanism 58 having a return passage 
R2, a changeover claw 59 and a paper sensor 89 for detecting the copy 
paper sheet P to be returned. In FIG. 1, the copying apparatus 1 further 
includes a main motor 24 for driving portions associated mainly with feed 
and transport of the copy paper sheets P, a PC motor 25 for driving the 
photosensitive drum 3, the transfer belt 11, etc. and a cooling fan 26. 
In the copying apparatus 1 of the above described arrangement, it is 
possible to form a monochromatic copied image of each of the colors of Y, 
M, C and BK, a composite monochromatic copied image of each of the colors 
of R (Y and M), G (Y and C) and B (M and C) in which the toner images of 
two of the primary colors are placed on each other and a color (full 
color) copied image in which the toner images of the primary colors are 
placed on one another. Changeover of such copying modes is performed by 
using various switches arranged on an operating panel (not shown). 
When the monochromatic copied image or the composite monochromatic copied 
image is formed, exposure scanning of the original document D is performed 
by using the half mirror 36ND and a latent image formed on the 
photosensitive drum 3 is developed by using one of the developing devices 
6 to 9 in accordance with a designated color so as to be transferred onto 
the transfer belt 11. In the case of the composite monochromatic copied 
image, exposure scanning of the same original document P is again 
performed by the half mirror 36ND and a toner image developed by using 
another on of the copying devices 6 to 9 is transferred onto the transfer 
belt 11 on which the toner images of the two colors are placed on each 
other. 
Meanwhile, when the color copied image is formed, the toners of the four 
colors of Y, M, C and BK are sequentially used in the copying apparatus 1 
so as to improve reproducibility of a black portion. Namely, exposure 
scanning is performed for the same copy paper sheet P a total of four 
times and the B, G, R and ND filters and the developing devices 6 to 9 are 
selectively changed over at the time of each scanning such that formation 
of latent images obtained by color separation of the original document D 
and development of the latent images are performed. Then, the toner images 
are sequentially transferred onto the transfer belt 11 such that the toner 
images of the respective colors are placed on one another on the transfer 
belt 11. 
When the toner images of the respective colors are placed on one another 
(hereinbelow, referred to as "multiple transfer"), the respective toner 
images are required to be transferred at an identical position on the 
transfer belt 11. Thus, in the copying apparatus 1 of this embodiment, 
timing of start of travel of the scanner 30, namely, timing of start of 
formation of the latent images on the photosensitive drum 3 is controlled 
on the basis of timing of generation of a belt mark signal S10 from the 
belt mark sensor 72 or 72s. 
Meanwhile, in the case of formation of the color copied image, preliminary 
scanning is performed so as to discriminate the images of the original 
document D into a color image portion having chromatic colors and a 
monochromatic image portion formed by only achromatic colors. At the time 
of image formation by the toners of Y, M and C, the latent image 
corresponding to the monochromatic image portion is erased by the editing 
eraser 5 prior to development. On the contrary, at the time of image 
formation by the toner of BK, the latent image corresponding to the color 
image portion is erased prior to development. Namely, the color image 
portion is reproduced by multiple transfer of the toners of Y, M and C, 
while the monochromatic image portion is reproduced by only the toner of 
BK. As a result, in the case of an image of characters or lines having a 
small line width, which are usually depicted in black, it becomes possible 
to obtain a clear copied image free from delicate positional 
noncoincidence of the color. Furthermore, in the case of a multicolor 
image such as a color photograph, it becomes possible to obtain a natural 
copied image having excellent reproducibility of the colors. 
FIG. 3 shows the AIDC sensor 73. The AIDC sensor 73 is constituted by a 
light emitting diode 73a and a photosensor 73b. The light emitting diode 
73a is disposed such that light emitted by the light emitting diode 73a is 
directed towards the photosensitive drum 3. Meanwhile, the photosensor 73b 
is so disposed as not to receive light of regular reflection effected by 
the photosensitive drum 3. Namely, in the case where toner adheres to the 
surface of the photosensitive drum 3, light from the light emitting diode 
73a is subjected to irregular reflection by the toner and thus, is 
received by the photosensor 73b. As a result, the photosensor 73b outputs 
a detection signal S1. However, in the case where there is no toner on the 
surface of the photosensitive drum 3, light from the light emitting diode 
73a is not incident upon the photosensor 73b. 
FIG. 4 shows one example of relation between amount QT of toner adhering to 
the photosensitive drum 3 and the detection signal S1. As the amount QT of 
the toner adhering to the photosensitive drum 3 becomes larger, 
accordingly, density of the toner image becomes higher, quantity of light 
received by the photosensor 73b is increased further. Meanwhile, magnitude 
of the detection signal S1 outputted by the photosensor 73b is increased 
in response to increase of the amount QT of the toner adhering to the 
photosensitive drum 3. Such relation between the amount QT of the toner 
and the detection signal S1 applies to the toners of the colors of Y, M, C 
and BK substantially identically. On the other hand, variations of the 
amount QT of the toner caused by environmental changes of temperature or 
humidity or lapse of time are different from one another in the toners of 
the colors of Y, M, C and BK mainly due to differences in components of 
the toners. 
FIG. 5 shows one example of relation between humidity in the copying 
apparatus 1 and the amount QT of each of the toners of the respective 
colors adhering to the photosensitive drum 3. Generally, the amount QT of 
the toner adhering to the photosensitive drum 3 is inclined to increase in 
response to rise of humidity for the following reason. Namely, in response 
to rise of humidity, quantity of charging of the toner in the developer is 
reduced, so that quantity of charging of the photosensitive drum 3 is 
increased relative to quantity of charging of the toner and thus, a larger 
amount of the toner particles adhere to the photosensitive drum 3. 
However, degree of above mentioned increase of the amount QT of the toner 
adhering to the photosensitive drum 3 in response to rise of humidity is 
different from one another in the toners of the respective colors and is 
arranged in reducing order of Y, M, C and BK. 
Meanwhile, in order to obtain proper reproducibility of colors of a copied 
image, it is necessary to maintain the amount QT of each of the toners of 
the respective colors at a predetermined value. To this end, an image 
quality adjustment table GT corresponding to characteristics of the toners 
of the respective colors shown in FIG. 5 is provided in the copying 
apparatus 1 as shown in FIG. 7. On the basis of the image quality 
adjustment table GT, detection result of the detection signal S1 is fed 
back to control for the corona charger 4, the exposure lamp 33, etc. such 
that image quality is adjusted. 
FIG. 6 shows one example of relation between the detection signal S1 and a 
grid voltage VG of the corona charger 4, while FIG. 7 shows contents of 
the image quality adjustment table GT. When the detection signal S1 of the 
AIDC sensor 73 exceeds a reference value of, for example, 7 V due to 
increase of the amount QT of the toner caused by rise of humidity in the 
copying apparatus 1, etc., the grid voltage VG of the corona charger 4 is 
lowered so as to decrease quantity of charging of the photosensitive drum 
3 such that the amount QT of the toner is reduced. In addition, a voltage 
VL for turning on the exposure lamp 33 is lowered so as to obtain proper 
density gradient. On the contrary, when the detection signal S1 is lower 
than the reference value, the grid voltage VG and the voltage VL are 
raised. 
For example, when the detection signal S1 exceeds the reference value in a 
range between 0.25 and 0.74 V as shown in FIG. 7, the grid voltage VG and 
the voltage VL are lowered by 40 V and 4 V, respectively for image 
formation of Y. Meanwhile, in the case of image formation of M, the grid 
voltage VG and the voltage VL are, respectively, lowered by 30 V and 3 V. 
Furthermore, also in image formation of C and BK, the grid voltage VG and 
the voltage VL are lowered. By changing setting values of the grid voltage 
VG and the voltage VL for the respective colors in the image quality 
adjustment table GT as described above, the amount QT of each of the 
toners of the colors of Y, M, C and BK is corrected to a proper value and 
thus, a copied image having excellent reproducibility of each color can be 
obtained. 
Interrelation among amounts of the toners of the colors of Y, M, C and BK 
adhering to the photosensitive drum 3 due to environmental changes is 
stored in the image quality adjustment table GT. Therefore, when the 
setting values of the image quality adjustment table GT are changed, it is 
not necessary to produce the AIDC patterns AP for all the four colors. 
Thus, the AIDC pattern AP is required to be produced for only one of the 
four colors and the image forming conditions of other colors may be set in 
accordance with the detection signal S1 on the basis of the image quality 
adjustment table GT. In this embodiment, the AIDC pattern AP is produced 
only for the toner of the color of Y and the toners of other colors of M, 
C and BK are corrected based on the detection signal S1 for the toner of 
the color of Y. 
FIG. 8 shows a control circuit 400 of the copying apparatus 1. The control 
circuit 400 includes a CPU 401 acting as a main unit for controlling whole 
operation of the copying apparatus 1, a controller 402 for not only 
controlling drive of various portions such as the scanner 30, the exposure 
lamp 33, the main lens 35 and the corona charger 4 but controlling the 
editing eraser 5 so as to produce the AIDC pattern AP and an image 
processor 100 for performing image processing by using various switches 
403 and a display unit 404 provided on the operating panel (not shown), 
the color image sensor 38, etc. Although not specifically shown, sensors 
including the AIDC sensor 73, the scanner home switch 74 and the sensor 77 
for detecting rotational position of the mirror device 36 are connected to 
the CPU 401 through proper interfaces. The CPU 401 incorporates a memory 
for storing programs, data, the image quality adjustment table GT, etc. 
Meanwhile, control circuits for a regulator of the exposure lamp 33 and the 
corona charger 4, which constitute a portion of the controller 402, each 
have a data line of several bits to be controlled by the CPU 401 such that 
output voltages of the regulator of the exposure lamp 33 and the corona 
charger 4 are varied by changing data from the CPU 401. 
Hereinbelow, operation associated with adjustment of image quality in the 
copying apparatus 1 is described with reference to flow charts of FIGS. 9 
and 10. FIG. 9 is a main flow chart schematically showing operation of the 
CPU 401. When a program is started upon turning on of a power source, 
initialization of registers and peripheral interfaces are performed at 
step #1 and an internal timer for determining length of one routine of the 
CPU 401 is set at step #2. Then, image forming processing associated with 
an electrophotographic process, which includes production of the AIDC 
pattern AP, is performed at step #3 and scanning processing for scanning 
the original document D is performed at step #4. Subsequently., belt mark 
detecting processing for determining timing of multiple transfer is 
performed at step #5. Thereafter, data on the exposure lamp 33 is 
outputted at step #6 and data on the grid voltage VG is outputted at step 
#7. At step #8, a series of sequential operation constituted by various 
processings such as paper feeding processing for controlling feed and 
transport of the copy paper sheets P, manual paper feeding processing for 
determining timing of manual feed of the copy paper sheets P through the 
manual paper feeding opening 41, temperature processing for adjusting 
temperature of the fixing unit 51, belt cleaning processing for cleaning 
the transfer belt 11, lens processing for controlling displacement of the 
main lens 35 in accordance with copying magnification, input processing 
for receiving signals from operational keys on the operating panel OP, 
etc. is performed. 
After these processings have been executed, it is judged at step #9 whether 
or not the internal timer has counted a preset period. In the case of 
"YES" at step #9, the program flow returns to step #2. Thus, length of one 
routine of the CPU 401 is set to a fixed value and the processings of 
steps #2 to #9 are repeated as long as the power source is held in the ON 
state. 
FIGS. 10a to 10j show image forming processing. In this routine, an imaging 
state indicated by a count of a state counter is initially checked at step 
#20 and the following processings are performed in accordance with the 
imaging state. Meanwhile, initial state immediately after turning on of 
the power source and waiting state after completion of copying operation, 
the imaging state is set to "0". In the imaging state "0", it is initially 
judged at step #21 whether or not a print key is in the ON state. In the 
case of "YES" at step #21, the main motor 24 and the PC motor 25 are 
turned on at step #22 so as to start rotational drive of the various 
portions of the copying apparatus 1, for example, the photosensitive drum 
3. Then, a motor rise timer for waiting for stable rotation of the main 
motor 24 and the PC motor 25 is set at step #23 and the imaging state is 
set to "1" at step #24. 
In the imaging state "1", the motor rise timer is updated at step #31 upon 
completion of counting of the preset period by the motor rise timer and it 
is judged at step #32 whether or not the motor rise timer has counted the 
preset period. In the case of "YES" at step #32, a request (retreat 
request) for rotation of the mirror device 36 is made at step #33 so as to 
form the latent image APE of the AIDC pattern AP. Thus, the half mirror 
36ND is displaced to a retreat position so as to intercept scanning light 
of the scanner 30. Thereafter, a request for production of the AIDC 
pattern AP is made at step #34 and the imaging state is set to "2" at step 
#35. 
In the imaging state "2", it is judged at step #41 whether or not the 
request for production of the AIDC pattern AP is made. In the case of 
"YES" at step #41, the developing device 6 for the toner of the color of Y 
for producing the AIDC pattern is turned on at step #42. Subsequently, the 
corona charger 4 and the editing eraser 5 are turned on at step #43, a 
rise timer is set at step 44 and the imaging state is set to "3" at step 
#45. At this time, the grid voltage VG of the corona charger 4 assumes a 
fixed value determined for producing the AIDC pattern AP. A preset period 
of the rise timer is determined based on width of the corona charger 4 and 
distance from the corona charger 4 to the editing eraser 5 such that the 
AIDC pattern AP is produced at a position on the photosensitive drum 3 
corresponding to the preset period of the rise timer. 
In the imaging state "3", the rise timer is updated at step #51. When it is 
found at step #52 that the rise timer has counted the preset period, 
eraser data for producing the AIDC pattern AP is outputted to the editing 
eraser 5 at step #53 such that formation of the latent image APE of the 
AIDC pattern AP is started. Subsequently, a pattern production timer for 
determining the length L2 of the AIDC pattern AP is set at step #54 and 
the imaging state is set to "4" at step #55. 
In the imaging state "4", the pattern production timer is updated at step 
#61. When it is found at step #62 that the pattern production timer has 
counted a preset period, the corona charger. 4 and the editing eraser 5 
are turned off at step #63. Thus, the latent image APE is formed at a 
predetermined position on the photosensitive drum 3 as shown in FIG. 2. 
Thereafter, a delay timer is set at step #64, a sensor arrival timer is 
set at step #65 and the imaging state is set to "5" at step #66. The delay 
timer has a preset period corresponding to a distance from the editing 
eraser 5 to the developing device 6 for the toner of the color of Y, while 
the sensor arrival timer has a preset period during which the AIDC pattern 
AP reaches a detection position of the AIDC sensor 73. 
In the imaging state "5", the delay timer is updated at step #71. If it is 
found at step #72 that the delay timer has counted the preset period, the 
developing device 6 for the toner of the color of Y is turned off at step 
#73. Subsequently, the sensor arrival timer is updated at step #74. If it 
is found at step #75 that the sensor arrival timer has counted the preset 
period, a pattern reading counter for counting the number of reading of 
the AIDC pattern AP is cleared at step #76 and the imaging state is set to 
"6" at step #77. In this embodiment, the pattern reading counter counts 10 
times. 
In the imaging state "6", the detection signal S1 of the AIDC sensor 73 is 
initially read out at step #81. Then, the pattern reading counter is 
updated at step #82 and it is judged at step #83 whether or not the 
pattern reading counter has counted 10 times. In the case of "YES" at step 
#83, the detection data of 10 times at step #81 is averaged at step #84. 
Detection is performed 10 times in view of scatter of the detection signal 
S1. By averaging the detection data of 10 times, reliability of the 
detection data is improved. Thereafter, a difference between the averaged 
detection data of step #84 and a reference value is calculated at step #85 
and thus, it becomes possible to learn how far the density of the current 
toner image deviates from the reference density. Subsequently, correction 
data of the corona charger 4 and the exposure lamp 33 in image formation 
of the respective colors is determined at step #86. This correction data 
is read out from the image quality adjustment table GT on the basis of the 
difference calculated at step #85. As described above, the correction data 
of the colors of Y, M, C and BK corresponding to the value of the 
detection signal S1 is stored in the image quality adjustment table GT. 
Thus, by producing the AIDC pattern AP of one color, it is possible to 
determine the correction data of all the remaining colors. Thereafter, the 
imaging state is set to "7" at step #87. 
In the imaging state "7", a decision is made at step #91 as to whether a 
copy mode designated by the operating panel is a monochromatic mode or a 
full color mode. The subsequent processing is performed in accordance with 
the decision of step #91. If it is found at step #91 that the 
monochromatic mode is designated, a request (ND request) for rotation of 
the mirror device 36, which is a flag for demanding positioning of the 
half mirror 36ND, is set at step #92. Thus, the half mirror 36ND is 
positioned to its image forming position. Subsequently, the corona charger 
4 and the exposure lamp 33 are turned on at step #93, output of the fur 
brush 19a for cleaning the transfer belt 11 is turned on at step #94 and a 
request for starting scanning of the scanner 30 is set at step #95. 
Thereafter, one of the developing devices 6 to 9 selected by the operating 
panel is turned on at step #96 and the imaging state is set to "8" at step 
#97. 
In the imaging state "8", if it is found at step #111 that scanning of the 
original document D has been completed, the corona charger 4 and the 
exposure lamp 33 are turned off at step #112, the developing device in 
operation is turned off at step #113 and the imaging state is set to "9" 
at step #114. 
In the imaging state "9", it is judged at step #121 whether or not a 
request for the next copy is made. In the case of "NO" at step #121, 
output of the fur brush 19a is turned off at step #122, the main motor 24 
and the PC motor 25 are turned off at step #123 and the imaging state is 
reinstated to "0" at step #124. Thus, the copying apparatus 1 is set in 
waiting state. Meanwhile, in the case of "YES" at step #121, the imaging 
state is reinstated to "7" at step #125. 
On the other hand, if it is found at step #91 of the imaging state "7" that 
the full color mode is designated, a request (home request) for 
positioning the half mirror 36ND to its home position so as to allow the 
image sensor 38 to read the original document D is set at step #98. 
Thereafter, the exposure lamp 33 is turned on at step #99 and output of 
the fur brush 19a is turned on at step #100. Subsequently, a request for 
preliminary scanning is made at step #101 and the imaging state is set to 
"10" at step #102. 
In the imaging state "10", if it is found at step #131 that preliminary 
scanning has been completed, the exposure lamp 33 is turned off at step 
#132 and a request (B request) for rotation of the mirror device 36, which 
is a flag for positioning the filter mirror 36YB to its image forming 
position, is set at step #133. Subsequently, a mark detecting permission 
for starting scanning at the time of turning on of the belt mark sensors 
72 and 72s is set at step #134 and the imaging state is set to "11" at 
step #135. 
In the imaging state "11", it is judged at step #141 whether or not the 
scanner 30 has started scanning in response to the belt mark signal S10. 
In the case of "YES" at step #141, output of the fur brush 19a is turned 
off at step #142 and the developing device 6 for the toner of the color of 
Y is turned on at step #143. Then, the imaging state is set to "12" at 
step #144. 
In the imaging state "12", if it is found at step #145 that scanning has 
been completed, the corona charger 4 and the exposure lamp 33 are turned 
off at step #146 and the developing device 6 for the toner of the color of 
Y is turned off at step #147. Subsequently, a request (G request) for 
rotation of the mirror device 36, which is a flag for positioning the 
filter mirror 36MG to its image forming position, is set at step #148 and 
the imaging state is set to "13" at step #149. 
In the imaging states "13" to "18", a series of processings for forming the 
toner images of the colors of M, C and BK, respectively are performed in 
the same manner as the above described formation of the toner image of the 
color of Y. Namely, the developing devices 7, 8 and 9 corresponding to the 
respective colors are turned on and off, the exposure lamp 33 and the 
corona charger 4 are turned off upon completion of scanning of the scanner 
30, the filter mirror 36CR or the half mirror 36ND corresponding to the 
subsequent scanning is positioned, etc. 
Meanwhile, if it is found at step #178 of the imaging state "18" that a 
request for the next copy is not made, the main motor 24 and the PC motor 
25 are turned off at step #179 and the mark detecting permission is reset 
at step #180. Then, the imaging state is reinstated to "0" at step #181. 
In the above described embodiment, by using the image quality adjustment 
table GT which preliminarily stores the correction data corresponding to 
variations of humidity, density of each of the toner images of the 
respective colors is adjusted. Therefore, it is not necessary to provide a 
humidity sensor for detecting humidity in the copying apparatus 1. 
Meanwhile, in the above described embodiment, the AIDC pattern AP is 
produced by using the developing device 6 of the color of Y. However, one 
of the remaining developing devices 7 to 9 or one of the developing 
devices 6 to 9 selected for copying may also be used. In the latter case, 
the correction data may be determined at step #86 in accordance with one 
of the developing devices 6 to 9 to be used. 
Furthermore, in this embodiment, setting of the grid voltage VG and the 
voltage VL is changed in accordance with the detection signal S1 such that 
amounts of the toners of the respective colors adhering to the 
photosensitive drum 3, i.e. densities of the respective toner images are 
adjusted. However, densities of the toner images of the respective colors 
may also be adjusted by changing setting of developing biases at the 
developing devices 6 to 9 or both the developing biases at &:he developing 
devices 6 to 9 and the voltage VL or the grid voltage VG. 
In this embodiment, the image quality adjustment table GT which stores the 
correction data corresponding to the toners of the colors of Y, M, C and 
BK is provided. However, in the case where toners in which degrees of 
variations of amounts QT of the toners are identical with each other are 
employed, the correction data can be used in common for these toners. 
Meanwhile, in this embodiment, adjustment of image quality in the copying 
apparatus 1 is described by way of example. However, the present invention 
can also be applied to an image forming apparatus such as a page printer 
in which image formation is performed by an electrophotographic process. 
Furthermore, in this embodiment, contents of the image quality adjustment 
table GT can be selected in accordance with characteristics of variations 
of the amount QT of the toner due to environmental changes such as 
humidity, temperature, etc. or deterioration of the photosensitive drum 3 
with time. In addition, constructions, shapes, dimensions, materials, etc. 
of the respective portions of the copying apparatus 1 can be modified 
variously. 
In accordance with the present invention, it becomes possible to not only 
minimize consumption of the toner for adjustment of image quality but 
reduce a period required for performing adjustment of image quality. 
Although the present invention has been fully described by way of example 
with reference to the accompanying drawings, it is to be noted here that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless otherwise such changes and modifications depart 
from the scope of the present invention, they should be construed as being 
included therein.