JP2747383B2 - Color balance adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color balance adjusting device such as a full color copying machine or a color printer.

[0002]

2. Description of the Related Art In general, in a full-color copying machine or a color printer, a color image is represented by three color toners of yellow, magenta, and cyan. In this case, as shown in FIG. The color balance must be adjusted so that the .gamma. Characteristics of the colors (original density vs. recording density) are the same. That is, when three colors of gray scale copy are overlapped,
The toner density of the three colors yellow, magenta and cyan must be adjusted in advance so that they have the same gray color.

However, an electrophotographic full color printer
In a copying machine or a color printer, it is very difficult to maintain the color balance initially set by the serviceman because the characteristics of the developer, the photoreceptor, and the transfer intermediate change over time.

Conventionally, this type of color balance adjusting device is configured to adjust the color balance by controlling the surface potential of the photoreceptor and the developing bias by feeding back the image density of each color. .

[0005]

However, in the above-mentioned conventional color balance adjusting device, when the surface potential of the photosensitive member is controlled by feeding back the image density of each color, the characteristics of the photosensitive member vary with time. There is no problem if it deteriorates to
When the development characteristic deteriorates with time, the characteristic does not deteriorate in the low-density region C of the original density, as indicated by the one-dot chain line in FIG.
Since the deterioration occurs in the high density area, the γ characteristic (broken line in the drawing) when the developing bias is corrected shows that the recording density becomes dark in the low density area C. Therefore, the conventional color balance adjusting device has a problem that the color balance of each color cannot be adjusted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a color balance adjusting apparatus capable of automatically adjusting the color balance in all density regions.

[0007]

SUMMARY OF THE INVENTION A color balance adjusting apparatus according to the present invention obtains image information by irradiating an image with a light source, and exposes a photosensitive member based on the image information to form a color image. A color balance adjusting device used in a color image forming apparatus that forms an electrostatic latent image corresponding to first, second, and third colors and visualizes the formed electrostatic latent image as a toner image. Then, for each of the first, second and third colors, the light source lamps are turned off and a blank run is performed.
A first method of forming a toner image in a high-density area and reading the toner density in the high-density area to adjust the toner density in the high-density area of each color by changing the grid voltage of the charger in a state where the lamp is turned on. Adjusting means, and forming a toner image in a low-density area for each of the first, second, and third colors while an optimum grid voltage is applied to the charger by the first adjusting means; A second adjusting means for reading the toner density in the low density area and adjusting the toner density in the low density area of each color by changing the lamp voltage of the light source lamp.

[0008]

[0009]

According to the structure of the present invention, the first adjusting means turns off the light source lamp for each of the first, second and third colors.
With the blank lamp lit, a toner image is formed in a high-density area, and the toner density in the high-density area is read to adjust the toner density in the high-density area for each color by changing the grid voltage of the charger. I do. Also, the second
The adjusting means of the first and second means, in a state where the optimal grid voltage is applied to the charger by the first adjusting means,
And forming a toner image in the low density area for each of the third colors, reading the toner density in the low density area, and adjusting the toner density in the low density area for each color by changing the lamp voltage of the light source lamp. Therefore, the first adjusting means obtains the optimum grid voltage of the charging charger, that is, the optimum surface potential of the photosensitive member in the high-density region, and the second adjusting means uses the optimum surface potential to optimize the light source lamp. The applied voltage is determined in the low density region, and thus the color balance can be automatically adjusted in all the density regions.

[0010]

The following examples of the present invention will clarify such an operation of the present invention, and further clarify other operations of the present invention.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a block diagram showing an embodiment of a high-density region adjusting device of the color balance adjusting device according to the present invention, and FIG. 1B is a low-density region adjusting device of the present invention. Block diagram showing an embodiment of the area adjustment device,
FIG. 2 shows a color provided with the color balance adjusting device of FIG.
FIG. 3 is a schematic diagram showing a copying machine, FIG. 3 is a graph showing characteristics of the infrared sensor shown in FIGS. 1 and 2, and FIG.
FIG. 5 is a flowchart for explaining the yellow adjustment operation of the high-density region adjusting device, and FIG. 5 is a flowchart for explaining the yellow adjustment operation of the low-density region adjusting device of FIG. -

First, a schematic configuration of a color copying machine provided with a color balance adjusting device of the present embodiment will be described with reference to FIG.

Referring to FIG. 1, a transparent document table 11 for mounting a document P is fixed on an upper surface of a machine frame by an opaque sheet metal 12, and the document table 11 is placed on the document table 11.
An opaque document pressing plate 13 for pressing the upper document P is provided so as to be openable and closable. For example, a document size or the like is printed on the upper surface of the sheet metal 12, and the lower surface of the sheet metal 12 and the document holding plate 13 are printed.
At least one of the lower surfaces is formed as a gray surface by being printed in gray or the like.

An exposure optical system 14 for scanning an image of the original P is disposed below the original mounting table 11, and the exposure optical system 14 has a home position below the sheet metal 12 and a sub-scanning position. Light source lamp 14a for illuminating the lower surface of the document P via the transparent document table 11, and the light reflected by the document P on the photoreceptor 16 as shown by a dashed line in FIG. A plurality of reflectors 14b for guiding to the exposure position A;
It comprises a color separation filter 14c having three primary color filters of red, green and blue, and an imaging lens 14d.

The photosensitive member 16 is formed in a belt shape and is rotatable in a counterclockwise direction in the figure by a driven roller 17 and a driving roller 18. A charging charger 19 is provided upstream of the exposure position A. Are located. In this embodiment, yellow, magenta, and cyan are used as examples of the first, second, and third colors for forming a color image.
Downstream from the exposure position A, in order, a blank lamp 19a for forming a non-image forming area, and a yellow developing tank 20Y,
A magenta developing tank 20M and a cyan developing tank 20Cy are arranged. Further, a black developing tank 20B for performing black-and-white copying or four-color color copying, and a toner image on the photoconductor 16 are transferred intermediately. Intermediate transfer body 21 and cleaning unit
22 and a static elimination lamp 23 are arranged.

The intermediate transfer member 21 is made of polycarbonate.
This is a black film in which the toner is dispersed, and is formed in a belt shape like the photoreceptor 16 and can be rotated clockwise in the figure by first to third rollers 24a to 24c.
It is pressed against the photoreceptor 16 by a roller 25. Downstream of the transfer roller 25, an infrared sensor 26 used for color balance adjustment in this embodiment is disposed.
Reference numeral 24c is in pressure contact with a transfer roller 28 for transferring the toner image on the intermediate transfer member 21 to the transfer paper 27. Infrared sensor
As 26, one that specifically detects only wavelengths of 750 nm or more is selected. FIG. 3 shows the characteristics of an example of such an infrared sensor 26.

The transfer paper 27 is set in advance in a cassette 30 at the lower right in the figure, and is set by a timing roller by feeding rollers 31 and 32.
The sheet is conveyed to the position of 33, and is conveyed to the position of the transfer roller 28 by the timing roller 33 so as to match the toner image on the intermediate transfer member 21. Transfer paper 27 onto which toner image has been transferred
Is transported to the fixing device 35 by the transport belt 34, and the toner
After the image is fixed by the fixing device 35, the image is discharged. Therefore,
The image of the original P is copied onto the transfer paper 27 by the charging-exposure-development-transfer process.

As will be described later, the automatic adjustment device 51 has a reflection value Y measured by the infrared sensor 26 when adjusting the high-density region.
_H, by the reflection value Y _L at low concentration region adjusting each charged Cha - Adjust grid voltage X _H Ja 19, the lamp voltage x _L of the light source lamp 14a, yellow - magenta, color cyan - balance total It is configured to automatically adjust in the density region. Thus, in this embodiment,
An example of the color balance adjusting device includes an automatic adjusting device 51 and an infrared sensor 26.

In the above configuration, the ordinary color
When copying is performed, the image of the document P is scanned three times, separated into three colors by the color separation filter 14c, and an electrostatic latent image of each color is formed on the photosensitive member 16. The electrostatic latent images of each color on the photoreceptor 16 are visualized in each toner by a yellow developing tank 20Y, a magenta developing tank 20M, and a cyan developing tank 20Cy, which are complementary colors of the respective colors of the color separation filter 14c. Each toner image is transferred onto the intermediate transfer member 21. In addition, when performing normal color copying, the black developing tank 20B and the infrared sensor 26 are not used.
Only B is used.

Next, a detailed configuration of the color balance adjusting device of this embodiment will be described with reference to FIG. This color balance adjusting device functionally comprises a high density region adjusting device 50H as shown in FIG. 1A and a low density region adjusting device 50L as shown in FIG. 1B. More specifically, as shown in FIG.
Is composed of a high density adjusting portion 51H of the automatic adjusting device 51 and an infrared sensor 26. As shown in FIG. 1B, the low density region adjusting device 50L is a low density adjusting portion 51L of the automatic adjusting device 51. It comprises an infrared sensor 26. Here, the high-density region adjustment device 50H and the low-density region adjustment device 50L
Means that the infrared sensor 26, the comparison circuit 52, and the memory 53 can be constituted by common hardware (or software).

The high density region adjusting device 50H shown in FIG.
In, yellow light source lamp 14a off in a state where the blank lamp 19a lit -, magenta, each toner in the high concentration region of the cyan - concentration Y _H is detected by the infrared sensor 26, a high density of each color by the comparison circuit 52 Area reference value A _H ,
B _H and C _H , respectively. Each color of toner - high-voltage transformer 55 a voltage value X _H of changing the grid voltage Ja 19 - Concentration Y _H and the reference value A _H, B _H, grid voltage control circuit 54 is charged tea as C _H matches instructs the grid voltage X _H when the match is stored in the memory 53 as the optimum value.

The low-density region adjusting device 50L shown in FIG.
Then, with the light source lamp 14a turned on and the optimal grid voltage adjusted by the high-density area adjusting device 50H applied to the charging charger 19, yellow, magenta,
Each toner in the low concentration region of the cyan - concentration Y _L infrared sensor
26, and are compared by the comparison circuit 52 with the reference values A _L , B _L , and C _L of the low-density areas of each color. Each color of toner - command concentration Y _L and the reference value A _L, B _L, source voltage control circuit 56 so that C _L to match the voltage value X _L to change the lamp voltage of the light source lamp 14a to light source 57 and the lamp voltage X _L when the match is stored in the memory 53 as the optimum value.

Next, the detailed operation of the color balance adjusting device 51 will be described with reference to FIGS. First, in the initial state, the ideal γ characteristics of yellow, magenta, and cyan as shown in FIG. 6 are set by the serviceman.
In this case, the same charge tea Regardless high concentration region and the low concentration region - and grid voltage X _H Ja 19, the light source lamp 14
When a is off (at the time of adjusting the high density area), each reference value A _H of the infrared sensor 26 at the time of yellow, magenta, and cyan adjustment,
B _H, C _H a light source lamp 14a is applied voltage X _L (at low concentration area adjustment) yellow - magenta, the reference value A _L of the infrared sensor 26 at the time of the cyan adjustment, B _L, is C _L memory 53 Is stored in Then, first, manually or by turning on the power,
The automatic color balance adjustment mode for the high density area as shown in FIG. 4 is started, and then the automatic color balance adjustment mode for the low density area as shown in FIG. 5 is started.

[0025] First, in step S1 shown in FIG. 4, the grid voltage X _H of the initial value charged Cha - is applied to Ja 19, in the subsequent step S2, yellow as well as to turn on the blank lamp 19a - the developer tank 20Y Launch and then
In step S3, the intermediate transfer member is
Detecting reflected value Y _H of 21. In this case, the light source lamp 14a
Does not light.

[0026] In step S4, the detected value Y _H and the high concentration region of the yellow - comparing the reference value A _H. If the reference value A _H > the detection value Y _H , the amount of toner attached has decreased from the initial state, so the flow branches to step S5 to increase the grid voltage X _H (+ α), and returns to step S1. . On the other hand, when the reference value A _H <detection value Y _H is toner - since the amount of deposition is increased from the initial state, reducing the grid voltage X _H branches to step S6 (-.alpha.), step Return to S1.

In step S4, if the reference value A _H = the detection value Y _H , the amount of toner adhered is the same as that in the initial state, so the process proceeds to step S7, where the grid voltage X _H
Is corrected as the grid voltage X _Hy in the yellow high concentration area, and the correction value X _Hy is stored in the memory 53 (step S
8). Although not shown in the figure, the correction values X _Hm ,
_{Find XHc} . The correction values X _Hy , X _Hm , and X _Hc correspond to the reference value D in the high density region in FIG.

The grid voltage correction value X _Hy ,
X _Hm, when obtaining the X _Hc, instead charging Cha - a grid voltage of Ja 19 value _{X H + α1, X H +} α2, X H -α1
, The grid voltage X _H closest to the reference value A _H may be corrected as yellow, magenta, and cyan grid voltages X _Hy , X _Hm , and X _Hc . Also, the initial value of the grid voltage in this color balance adjustment mode should not be the same as the grid voltages X _Hy , X _Hm , and X _Hc at the time of normal copying, for example, X _H = X _H
A different value may be used as + kα.

[0029] Next, in step S9 shown in FIG. 5, the light source lamp 14a illuminates an initial value X _L, the lower surface of the sheet metal 12 by the light source lamp 14a does not move when the lower surface of the sheet metal 12 is printed in gray When the lower surface of the original pressing plate 13 is printed in gray, the light source lamp 14a moves to illuminate the lower surface of the original pressing plate 13. Therefore, the light source lamp 14a illuminates the gray document.

In the following step S10, the color separation filter 14c
The blue filter is selectively disposed in the optical path and the yellow developing tank 20Y is selectively driven. Therefore, gray document is illuminated by the light source lamp 14a of the applied voltage X _L Bull - through the filter is guided to the exposure position A of the photoreceptor 16, an electrostatic latent image corresponding to the gray document on the photoreceptor 16 It is formed. Then, this electrostatic latent image is visualized by a toner in a yellow developing tank 20Y and transferred onto the intermediate transfer member 21.
The surface of the photoconductor 16 is charged by the charging charger 19 at the grid voltage X _Hy in the high-density region described above.
The transfer paper 27 is not used.

[0031] Then, in step S11, it detects a reflected value Y _L of the low concentration region of the intermediate transfer body 21 by the infrared sensor 26, then compared with the reference value A _L of the low concentration region (step S12). When the reference value A _L <the detection value Y _L , the amount of adhered toner has increased from the initial state.
Branches to step S13 lamp voltage X _L, for example, 1V
(= Α) increases and returns to step S9. On the other hand, the reference value A _L
> In the case of the detection value Y _L is toner - since the amount of deposition of is reduced from the initial state, the branch to the lamp voltage X _L, for example, 1V (= α) decreases in step S14, the flow returns to step S9.

In step S12, if the reference value A _{L is} equal to the detected value Y _L , the amount of toner adhered is the same as in the initial state.
_L is corrected as the lamp voltage X _{Ly in} the low concentration region of yellow, and the correction value X _Ly is stored in the memory 53 (step S1).
6). Although not shown, the correction values X _Lm and X _Lc of the low-density region of the lamp voltage are similarly calculated for magenta and cyan.
Ask for. The correction values X _Ly , X _Lm , and X _Lc correspond to the reference value E in the low-density area in FIG. 6 and are used as reference values for normal copying.

In the above example, good results were obtained when the values were as follows.

High concentration region; initial grid voltage X _HY : -400 to -300 V Grid voltage at the time of adjustment X _H : -200 to -300 V X _HY = X _HY + kα k = 1.0 to 1.5 Reference value A _H , B _H, C _H: Macbeth density of 0.6 to 1.0 low density region; initial lamp voltage X _LY: 60~70V gray document: gray Macbeth density of 0.2 to 0.4 - reference value _{a L, B L, C L} : Macbeth Therefore, in the above embodiment, when adjusting the high-density region, the light source lamp 14a is turned off, and the grid voltage of the charging charger 19 is changed to obtain the optimum grid voltage. Is adjusted, the voltage of the light source lamp 14a is turned on to obtain the optimum lamp voltage. As shown in FIG.
There is an effect that the recording density does not become dark in the low density area C even if the developing characteristic deteriorates with time.

In the above embodiment, the charging charger 19
Since the surface potential of the photoreceptor 16, which greatly affects the amount of exposure, is adjusted first, the adjustment can be performed quickly. If the lamp voltage of the light source lamp 14a is adjusted first, it is possible to correct for contamination of the optical system 14, etc., but the grid voltage of the charging charger 19 will be increased later. Therefore, the color balance is deviated.

[0036]

As described above, the first adjusting means controls the light source run for each of the first, second and third colors.
With the lamp turned off and the blank lamp turned on, a toner image in the high density area is formed, and the toner density in the high density area is read to change the toner density in the high density area for each color by changing the grid voltage of the charger. Adjust. The second adjusting unit forms a toner image in a low density area for each of the first, second and third colors in a state where the optimal grid voltage is applied to the charging charger by the first adjusting unit. At the same time, the toner density in the low density area is read, and the toner density in the low density area of each color is adjusted by changing the lamp voltage of the light source lamp. Therefore, the first adjusting means obtains the optimum grid voltage of the charging charger, that is, the optimum surface potential of the photoconductor in the high density region,
The second adjusting means uses the optimum surface potential to determine the optimum applied voltage of the light source lamp in the low density region, and thus the color balance can be automatically adjusted in all the density regions.

[0037]

As described above, according to the present invention, a convenient color balance adjusting device capable of automatically adjusting the color balance in all density regions can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a color balance adjusting device according to the present invention.

FIG. 2 shows a color provided with the color balance adjusting device of FIG.
FIG. 1 is a schematic configuration diagram illustrating a copying machine.

FIG. 3 is a graph showing characteristics of the infrared sensor shown in FIGS. 1 and 2;

FIG. 4 is a flowchart for explaining the yellow adjustment operation of the high-density region of the color balance adjustment device of FIG. 1;

FIG. 5 is a flowchart for explaining the yellow adjustment operation of a low-density region of the color balance adjustment device of FIG. 1;

FIG. 6 is a graph showing an optimal color balance.

FIG. 7 is a graph showing a change in color balance with time and an operation of a conventional color balance adjustment device.

[Explanation of symbols]

 16 Photoreceptor 20Y, 20M, 20Cy Developing tank 26 Infrared sensor 50H High density area adjustment device 50L Low density area adjustment device 51 Automatic adjustment

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kawamoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Tsuyoshi Miyamoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-63-106763 (JP, A) JP-A-2-257166 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/01 G03G 15 / 01-15/01 117

Claims (1)

(57) [Claims] An image is obtained by irradiating an image with a light source, and a photoreceptor is exposed based on the image information to form a color image according to first, second, and third colors. A color balance adjusting device used in a color image forming apparatus for forming an electrostatic latent image and visualizing the formed electrostatic latent image as a toner image, wherein the first, second, and third colors are used. Turn off the light source lamp for each color
A first method of forming a toner image in a high-density area and reading the toner density in the high-density area to adjust the toner density in the high-density area of each color by changing the grid voltage of the charger in a state where the lamp is turned on. Adjusting means, and forming a toner image in a low-density area for each of the first, second, and third colors while an optimum grid voltage is applied to the charger by the first adjusting means; A second adjustment unit that reads the toner density in the low-density area and adjusts the toner density in the low-density area for each color by changing the lamp voltage of the light source lamp.