JPH07221986A - Image processing unit - Google Patents

Abstract

PURPOSE:To attain density control without losing an image balance by providing a setting means setting image quality and a control means controlling the density of an image signal depending on a density area based on an output of the setting means to the processing unit. CONSTITUTION:A LOG transformation circuit 4 transforms a luminance signal into a density signal and it is outputted to a BK generating circuit 5, the circuit 5 generates a BK signal and it is outputted to a gamma-LUT circuit 6. The circuit 6 applies gradation conversion to four color signals in matching with a characteristic of a printer so that a density after print linearly corresponds to an input density signal and provides an output. An operation section 8 outputs a control signal corresponding to the adjustment quantity adjusted by an operation panel to a CPU 9, which outputs a control signal to a gradation adjustment circuit 7. The circuit 7 consists of ROMs provided for each color and density identification and each ROM has a table comprising output values depending on the adjustment characteristic and the table and converts the received density signal and provides an output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus capable of adjusting image quality.

[0002]

2. Description of the Related Art Conventionally, as this type of apparatus, for example, a color gradation adjusting apparatus used in a color copying machine or the like has been known. In such a gradation adjustment device, the gradation of each color is adjusted with the characteristics shown in FIG. 14 for each input density signal.

FIG. 14 is a diagram showing specific characteristics of gradation adjustment. Normally, color conversion is performed with a linear characteristic indicated by b. However, the user likes the gradation characteristics of each color. 14a, by operating the operation panel or the like according to
A characteristic such as c is set, and as a result, gradation adjustment can be performed.

[0004]

However, in such a conventional adjusting apparatus, when there are colors having the same hue but different lightness in the original, that is, colors of the same series but different in darkness, When the color balance adjustment is performed to match a relatively light color, the dark color also changes as a result, and there is a problem that the tint cannot be adjusted as the user intended.

In the background described above, the present invention is
An object of the present invention is to provide an image processing apparatus capable of adjusting the gradation of an image without impairing the balance of the image as a whole.

[0006]

SUMMARY OF THE INVENTION In order to solve the problems conventionally held and to achieve the above object, an image processing apparatus according to the present invention is based on a setting means for setting an image quality and an output of the setting means. , And a control means for controlling the density of the image signal according to the density range.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a digital full-color copying machine which is an embodiment of the present invention.

In FIG. 1, reference numeral 100 is a copying machine main body. When copying an original with this copying machine 100, first,
A document 116 on the platen glass 117 is illuminated by a light source 118, and the CCD 1 converts the reflected light from the document into a light amount signal. The light amount signal is processed by the image processing unit 119 as described later and output to the laser driver 102 as a control signal for driving the semiconductor laser.

The laser driver 102 is a semiconductor laser 10.
3 is a circuit for driving the semiconductor laser 3 and controls the semiconductor laser 103 according to an input control signal to switch ON / OFF. The laser beam 104 output from the semiconductor laser 103 is swung in the left-right direction by the polygon mirror 105 and scans the photosensitive drum 106. This laser light 10
The photosensitive drum 106 on which the latent image is formed by the scanning of 4 is
The image is rotated in the direction indicated by the arrow in the figure, and development is performed for each color by the rotary developing device 112. The figure shows a state in which yellow is being developed.

On the other hand, the recording paper is wound around the transfer drum 113, and is developed by the rotary developing device 112 in order of Y (yellow), M (magenta), C (cyan), and BK (black) every one rotation. By rotating four times in total, four colors are transferred to the recording paper, and the color recording is completed. Then, the recording paper is separated from the transfer drum 113 and fixed by the fixing roller pair 114, and the color image print is completed.

Next, the operation of the image processing section 119 will be described with reference to FIG. In FIG. 2, R (red) obtained from the CCD 1 through a color separation filter (not shown),
The light intensity signals of the three colors G (green) and B (blue) are A /
The digital signal is converted by the D conversion circuit 2 and output to the shading circuit 3. The shading circuit 3
By adjusting the gain of each signal corresponding to each CCD sensor cell, control is performed so as to eliminate variations in the characteristics of the CCD sensor cell groups arranged in a line, and the CCD sensor cells are output to the LOG conversion circuit 4. Then, the LOG conversion circuit 4 converts the R, G, and B luminance signals into C, M, and Y density signals and outputs them to the BK generation circuit 5. The BK generation circuit 5 uses these density signals to generate a BK (black) signal,
The four color signals of C, M, Y and BK are output to the γ-LUT circuit 6. The .gamma.-LUT circuit 6 converts the four color signals into gradations so that the density after printing linearly corresponds to the input density signal according to the characteristics of the printer, and outputs as a serial signal.

Then, as described later, the CPU 9 controls the gradation adjusting circuit 7 in accordance with a control signal output from the operating section 8 to adjust the tint. The density signal whose color has been adjusted by the gradation adjustment circuit 7 is converted by the pulse width modulation circuit 10 into a signal corresponding to the light emission time of the laser light according to the density signal, and is output to the laser driver 11.

Next, the operation of the density adjustment in this embodiment will be described. FIG. 3 is a diagram showing the adjustment characteristic in this embodiment, in which the horizontal axis represents the level of the input image signal and the vertical axis represents the modulation amount. In this embodiment, the density range of the density signal is set to a low density range H, levels 0 to 80, and a middle density range M, 60 to 16.
As a high density region S of 0, 80 to 255 were overlapped and divided. The values when dividing these areas are divided according to how the density is perceived, and then overlapped so that the gradations do not become discontinuous when combining the independently set modulation amounts as described below. It is a thing. Further, the values indicated by Δh, Δm, and Δs in the figure are the maximum values of the adjustment amount in each region, and Δh = 10, Δm = 30, and Δh.
s = 50. This follows the effect of gradation change, and it is desirable to adjust the density more finely in the low density region, and conversely,
This is because the high-concentration region does not require such fine adjustment.

FIG. 4 is a view showing an operation panel for adjusting the density as described above, which is provided in the operation unit 8 in FIG. 2, and for example, a liquid crystal display panel is used. In FIG. 2, C, M, Y, and BK are marks for selecting a color to be adjusted, and H, M, and S are marks showing the above-described density range. Then, in order to select the color to be adjusted, the corresponding mark of C, M, Y, BK is pressed to select it. Also, adjustment of each density range is performed by pressing the + and-marks. In the figure, cyan is selected, and the low density H is ± 0, the middle density M is +2, and the high density S is +6.

Next, a method of adjusting gradation characteristics will be described. The gradation characteristic is adjusted by multiplying the value of the characteristic curve shown in FIG. 3 by a ratio according to the modulation amount operated on the operation panel. Table 1 shows the values displayed on the operation panel and the ratios by which the modulation amounts shown in FIG. 3 are multiplied.

[0017]

[Table 1]

In FIG. 2, the operation unit 8 outputs to the CPU 9 a control signal according to the adjustment amount adjusted by the operation panel as described above, and the CPU 9 outputs the control signal to the gradation adjusting circuit 7. The gradation adjusting circuit 7 is composed of a ROM provided for each color and density range. Then, in these ROMs, the adjustment characteristics shown in FIG. 3 and the output values determined based on Table 1 are prepared as a table,
It is converted according to the value of the input density signal and output. It should be noted that all the ROMs whose converted values exceed 255 are clipped to 255.

FIG. 6 shows gradation characteristics when the settings are made as shown in FIG. In the figure, the broken line M represents the amount of modulation in the medium density region, and the broken line S represents the amount of modulation in the high density region. The solid line shows the modulation characteristics obtained by combining these modulation amounts.

As described above, in the present embodiment, the adjustment characteristic is set for each density range, and the density of the image signal is controlled based on this adjustment characteristic. It becomes possible to control.

Further, the gradation adjustment for each density range in the present embodiment and the conventional gradation adjustment shown in FIG. 14 (hereinafter referred to as color balance adjustment) may be performed. This case can also be realized by providing a ROM having a table of color balance adjustment characteristics for each color.

FIG. 6 is a display of the operation panel when the color balance is adjusted, and shows the case where the adjustment amounts are ± 0 for C, +3 for M, −4 for Y, and ± 0 for BK.
FIG. 7 is a diagram showing a configuration example of the gradation adjustment circuit 7 in the present embodiment, which has a ROM 701 for color balance adjustment and a ROM 702 for adjustment by density range, and the output of each ROM is added by an adder 703. Add and output. 8 is a flowchart showing the operation of this embodiment, and the operation of this embodiment will be described below with reference to FIG.

First, the operation panel is displayed as shown in FIG. 6, and the user determines the adjustment amount for each color (step S).
801). When the adjustment by density range is further performed after the adjustment amount is determined, the portion for density range adjustment displayed on the upper right of the operation panel is pressed (step S802). Then, the display of the operation panel changes as shown in FIG. 4, and it becomes possible to perform adjustment for each density range. Therefore, the user determines the color to be adjusted as described above (step S80).
3) Next, the adjustment amount for each density range is determined (step S
804). By configuring as described above, first, the overall image density adjustment is performed by the color balance adjustment,
When it is desired to make finer adjustments, it is possible to make adjustments for each density range, which makes it easier for general users who do not require such fine adjustments. As described above, the output of the gradation adjusting circuit 7 is configured to reflect both the density adjustment by the color balance adjustment and the adjustment for each density range.

Next, a second embodiment of the present invention will be described. In FIG. 9, the low-concentration range H is +8, the middle-concentration range M is -8,
The adjustment curve when the high concentration range S is adjusted to +8 is shown. In this case, the adjustment curve shown by the solid line in FIG. 9 is obtained, but as is clear from the figure, the gradation adjustment is discontinuous. In particular, in the portion where the input image signal level is 70 to 85, the characteristic is downward-sloping and the gradation change is inverted in this portion, which results in a solarization effect as the characteristic of the output image signal, resulting in an unnatural image. Therefore,
In this embodiment, when extreme gradation adjustment is performed on the operation panel in this way and the characteristic of downward sloping occurs, the CPU 9 judges this and the operation panel displays "abnormal image". I will display it. This allows the user to recognize that the output image is unnatural when such gradation adjustment is performed.

Further, when the CPU 9 determines that the adjustment characteristic is not normal such as the rightward falling, the rightward falling is eliminated on the apparatus side as indicated by the alternate long and short dash line A in FIG. 8 and the normal adjustment characteristic is obtained. If the characteristic is changed to, it becomes possible to perform normal image adjustment in the form closest to the image desired by the user.

If the adjustment characteristic is abnormal, the user is allowed to judge whether the characteristic may be automatically corrected after displaying that the image is an abnormal image. The adjustment may be redone.

The above operation will be described with reference to the flowchart of FIG. 10 in the case where the color balance adjustment is included. First, the color balance is adjusted by the display on the operation panel shown in FIG. 6 (step S101). Next, when the adjustment for each density range is performed, the display portion is pressed to change to the panel for performing the adjustment for each density range (step S10).
2). Then, after determining the color to be adjusted (step S
103), the adjustment amount is determined for each density range (step S
104). Next, it is determined whether the adjustment characteristic determined in step S104 is normal (step S105), and if normal, the characteristic is converted and output as it is.

If it is determined in step S105 that the adjustment characteristic is not normal, an abnormal image is displayed on the operation panel (step S106). And
Whether or not the adjustment characteristic is automatically changed on the device side is displayed on the operation panel, and if the user can change it, the CPU
By changing the read address of the density area-specific ROM 702 by 9, the characteristic is corrected so that it becomes a normal adjustment characteristic as described above, and is output (step S107). When the user refuses to change the characteristic on the device side in step S107, the fact that the change in the adjustment amount is supported is displayed on the operation panel (step S108), and the process returns to step S104.

In the above-described embodiment, the message is displayed when the adjustment characteristic is abnormal. However, any message that can be recognized by the user may be used. It may be possible to notify by sound such as buzzer or chime, or by light such as LED. Further, if the adjustment characteristic is abnormal, the device may arbitrarily perform the correction after the display.

Further, in the above-mentioned embodiment, the case where the curve is sloping down to the right is taken as the case where the adjustment characteristic is abnormal. In such a case, similar image quality abnormality may be recognized, and even in such a case, it is possible to notify the user of the abnormal image by similarly issuing a warning.

Next, a third embodiment of the present invention will be described. In the above-described first and second embodiments, the density adjustment is performed based on the adjustment characteristics shown in FIG. 3, but in this case, there are cases where the density is increased and where it is decreased as shown by the broken line in FIG. It is conceivable that the degree of modulation in the vertical direction (angle of the modulation characteristic with respect to the straight line) differs from that in the unadjusted state shown by the straight line in the figure, and the image quality after adjustment is deteriorated. In order to avoid this, as shown by the solid line in FIG. 11, when the density is increased or decreased in each density range, it is desirable to set the modulation characteristics so that the characteristics change symmetrically with respect to the straight line. .

Therefore, in the present embodiment, as shown in FIG. 12, as the modulation characteristic, an adjustment characteristic different from the adjustment characteristic shown in FIG. 3 is newly set, and the case of increasing and decreasing the density of FIG. The adjustment characteristic is symmetrical in the vertical direction with respect to the straight line.

By setting the adjustment characteristics in this way, the density change becomes symmetrical when the density is raised and when the density is lowered, and the image quality after density adjustment is not deteriorated.

Further, based on the same idea, as shown in FIG. 13, the final adjustment characteristic may be set by vertically determining the modulation amount for each density range from the unadjusted state. Good. However, in this case, in order to obtain the curve of the adjustment characteristic, it is necessary to newly calculate the adjustment amount for the straight line shown in FIG. 12 and then add it to the straight line to obtain the final adjustment characteristic.

As described above, even when the density adjustment is performed based on the adjustment characteristics shown in FIG. 13, there is no fear of deterioration of the image quality after the density adjustment as in the above-described embodiment.

Although the ROM is used in the gradation adjusting means in the above-mentioned embodiment, the ROM is limited to this as long as it has a so-called look-up table (LUT) function for performing an output corresponding to the input image signal. is not.
Further, only the adjustment characteristic as shown in FIG. 3 may be stored in the ROM, which may be prepared for each color, and the ratio shown in Table 1 may be input from the external control means and added last. .

[0037]

As is apparent from the above description, the present invention is effective in detecting the density of an image signal and controlling the density.
Since the density of the image signal is controlled according to the density range, the density of the image can be controlled without impairing the overall balance of the image.

In another invention of the present application, the image quality is adjusted based on the adjustment characteristics set for each color and density range, and if the adjustment characteristics are abnormal, a message to that effect is displayed. Since it is configured as described above, it is possible to perform fine image quality control for each density range, and to let the user recognize that the image quality becomes abnormal due to the adjustment characteristics set by the user. .

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a color copying machine that is an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image processing unit in the color copying machine of FIG.

FIG. 3 is a diagram showing an example of adjustment characteristics in the embodiment of the present invention.

FIG. 4 is a diagram showing a display of an operation panel in the embodiment of the present invention.

FIG. 5 is a diagram showing an adjustment characteristic in which the adjustment characteristics of respective density regions are integrated in the gradation adjustment circuit.

FIG. 6 is a diagram showing a display of an operation panel in the present invention.

FIG. 7 is a diagram showing a configuration of a gradation adjustment circuit according to an embodiment of the present invention.

FIG. 8 is a flow chart for explaining an embodiment of the present invention.

FIG. 9 is a diagram showing another example of adjustment characteristics set on the operation panel.

FIG. 10 is a flow chart for explaining an embodiment of the present invention.

FIG. 11 is a diagram showing another example of adjustment characteristics in the embodiment of the present invention.

FIG. 12 is a diagram showing an example of the adjustment characteristics shown in FIG. 11 for each density range.

FIG. 13 is a diagram showing still another example of the adjustment characteristic in the embodiment of the present invention.

FIG. 14 is a diagram for explaining a conventional technique.

[Explanation of symbols]

 7 Gradation adjustment circuit 8 Operation unit 9 CPU

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 1/46 H04N 1/40 D 1/46 Z

Claims (10)

[Claims] 1. An image processing apparatus comprising: setting means for setting the image quality; and control means for controlling the density of an image signal according to the density range based on the output of the setting means. 2. The adjusting characteristic is set for each density range by the setting means, and the control means controls the density of the image signal based on the adjusting characteristics for each density range. The image processing device described. 3. The image processing apparatus according to claim 2, wherein the control unit has an integration unit that integrates adjustment characteristics set for each of the density regions. 4. The image processing apparatus according to claim 2, further comprising a characteristic detection unit that detects whether or not the adjustment characteristic set by the setting unit is normal. 5. The image processing apparatus according to claim 4, further comprising an operation panel for operating the control means,
An image processing apparatus, which displays on the operation panel according to an output of the characteristic detection unit. 6. The image processing apparatus according to claim 4, further comprising a correction unit that corrects the adjustment characteristic according to the output of the characteristic detection unit. 7. The image processing apparatus according to claim 2, wherein the adjustment characteristic is different when the density is increased and when the density is decreased. 8. A color copying machine provided with the image processing apparatus according to claim 1. 9. A setting means for setting the image quality, a first control means for controlling the density of the image signal based on the output of the setting means, and an image according to the density range based on the output of the setting means. An image processing apparatus comprising: a second control unit that controls the density of a signal. 10. An operation panel that adjusts the density of an image signal for each color and density area, and a plurality of gradation characteristics set for each density area based on the output from the operation panel. A gradation adjustment circuit that controls the density of the image signal, an integrated circuit that integrates the plurality of gradation characteristics, and detects whether the gradation characteristics integrated by the integrated circuit are normal and abnormal. An image processing apparatus, comprising: a detection unit that displays a message on the operation panel in response to the detection.