JPH0465583B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image processing device, and particularly to an image processing device that processes multiple color components.

<Prior Art> In devices that obtain full-color color copies, such as color printers, color copying machines, or color printing machines, conventionally, yellow, magenta, and cyan developers or inks are superimposed on the same image. A copy of the image is obtained. At this time, the black component of the original or the black component of the copied image is a major factor that influences the sharpness of the image.

Conventionally, for example, in a color copying apparatus, black has been represented by uniformly transferring yellow, magenta, and cyan developers at high concentrations to locations corresponding to black areas of a document. However, in this case, the yellow, magenta, and cyan developers are not actually composed only of pure yellow, magenta, and cyan components, but have spectral reflectances as shown in Figure 1. For example, it is known that magenta developer contains equivalent yellow and cyan components, and cyan developer also contains some yellow and magenta components. Even if it appears to have been transferred evenly, the color balance of each color may not be maintained, resulting in a slightly colored black, or because the three colors of developer are layered, the reflected light from the coloring material becomes muddy, resulting in a muddy black. Put it away.

Further, in a full-color digital color printer, if the black component in the target image is printed using black developer or black ink, the reading system may be configured as shown in FIG. 2, for example. In this example, the exposed light L is separated into each color component L _Y , L _M , L _C by a dichroic mirror, and the CCD
8, 9, 10 perform photoelectric conversion, and amplifiers 11, 12,
13, the digital values of each color component obtained through the A/D converters 14, 15, 16 are stored in advance in the memory 2.
Comparators 17, 18, and 19 compare the predetermined digital values stored in pixels ₀ , 21, and 22 to obtain final pixel data DY, _DM , and _DC . If data = "1" is the print level, when D _Y , D _M , and _DC are all "1", that pixel is treated as black component pixel data D _BK .

Processing by such a device can prevent the above-mentioned muddy black, but depending on the settings of the threshold values in the memories 20 to 22, in the case of FIG. If all the dots are replaced with black dots, or if the level of each color is not very high as in the case of Figure 3b, not only are the dots not replaced with black dots, but all the dots of each color are not hit and no dots are hit. You won't be able to get enough of it. For this reason, halftones are also not well reproduced.

Therefore, a method of reproducing the halftone components by performing halftone processing and converting the halftone components into the area ratio of dots and changing the area ratio can be considered, but such a method requires sharpness such as black characters. There also arises a problem in that the edge portions of the character portions deteriorate and the reproduced quality deteriorates.

Further, in the configuration shown in FIG. 2, since black portions are detected using the data outputted from 17 to 19 which have been subjected to halftone processing, a problem arises in that the black portions cannot be extracted with high accuracy.

In view of this point, it is an object of the present invention to provide an image processing device that can reproduce both halftone color images and black areas with high quality.

<Problems to be Solved by the Invention> In order to achieve the above-mentioned objects, the present invention includes: means for generating a plurality of color component signals; digital signals corresponding to the color signal components to reproduce an image corresponding to the color component signals; The first processing mode performs halftone processing suitable for halftone components when performing area gradation processing on the image, and the first processing mode performs halftone processing suitable for halftone components. a second processing mode for converting into an image signal having two emphasized and different states; means for determining a black area from the plurality of color component signals before halftone processing by the processing means; and control means for controlling the processing mode of the processing means to the second processing mode on the condition that the processing means determines a black area.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 4 is a schematic diagram of an image reading device of a digital color copying apparatus according to the present invention. A document placed on a document table 30 is irradiated with light from a document irradiation lamp 31, and reflected light L from the document is reflected by mirrors 32, 3.
3, the light is condensed by a lens 34, transmitted and reflected by dichroic mirrors 35 and 36, and reflected by a mirror 37. The reflected light from the original is converted into B, G, and R components, respectively. color separated,
Each photoelectrically converted by CCD38, 39, 40,
The light quantity components of each color are extracted as electrical signals.
Each of the dichroic mirrors 35 and 36 has a spectral reflection characteristic as shown in FIG.
is coated with an infrared cut filter.
It is designed to reflect only red light, which is a complementary color to cyan. The electrical signals obtained for each color component are input to the reading control circuit 41, and each signal processing is performed.

FIG. 6 shows an example of this reading control circuit. The video signals V _Y , V _M , V _C of each color read by the CCDs 38 , 39 , 40 and photoelectrically converted are output in synchronization with a clock φ output from an oscillation circuit (not shown), and are outputted by amplifiers 41 , 42 , 43 . After each amplification, level adjustment is performed at 44, 45, and 46 to obtain video signals V _Y ', V _M ', and V _C '. The video signals V _Y ′, V _M ′, and V _C ′ obtained here are input to the subsequent circuit and also input to the black component extraction circuit 70 to become yellow, magenta, and cyan pixel signals. , here the black component is extracted. V _Y ′, V _M ′, V _C ′ are variable resistors 52, 53,
54 and the comparators 49, 50, 5
When a signal with a level higher than the threshold is input, the output of the comparator becomes "1". Note that this threshold value is variable for each of B, G, and R. When all of the video signals V _Y ', V _M ', and V _C ' exceed their respective thresholds, the outputs of the comparators 49, 50, and 51 all become "1".
Therefore, the transistors 55, 56, and 57 are turned on, so the inputs of the OR gate 58 are all "0", and the output of the OR gate 58 is "0" and input to the switching input S of the analog multiplexer 48.
Therefore, if any one of the video signals V _Y ', V _M ', and V _C ' is below the threshold value, the signal S is "1". Therefore, when all of the video signals are at a high level, that is, when the yellow, magenta, and cyan components are of high density, they are extracted as black components, and the signal S remains at "0" during that time. The above situation is shown in FIG. The section of CK3 in which the video signals V _Y ', V _M ', and V _C ' synchronized with the clock φ all exceed the respective threshold values is the BK component, and shows that S=0.

As mentioned above, the video signals V _Y ′, V _M ′, and V _C ′ are
In addition to being used to extract the BK component, these signals themselves are yellow, magenta, and cyan color signals, and each signal is a signal S that is in the interval "0" of the BK component of the signal, and is connected to the input ports (I ₁ , I ₃ , I ₅ , I ₇ ) and a signal that becomes "1" switches the connection between (I ₂ , I ₄ , I ₆ , I ₉ ) and the output port (O ₁ , O ₂ , O ₃ , O ₄ ). The analog multiplexer 48 connects and disconnects the signals.
Note that 47 is a delay circuit that compensates for the signal delay in the black component extraction circuit. Now S = “1”, therefore,
In sections other than the black component, 48 output ports O ₁ , O ₂ ,
Video signals V _Y ', V _M ', V _C ' and "0" level as BK components are connected to O ₃ and O ₄ , and the yellow, magenta, and cyan components of each signal are sent to the A/D converter 5.
After being A/D converted at 9, 60, 61, the threshold values and comparators 63, 64, 6 are stored in advance as a dither matrix in memories 66, 67, 68.
After being compared and binarized in step 5, the binarized pixel data _DY , _DM , and _DC are stored in a printer section (not shown) or a storage device such as a disk file. The timing is taken at 62 and the BK pixel data (=0) is
Selected later. On the other hand, in the black component section where S = "0", I ₁ , I ₃ , I ₅ , I ₇ are connected to the outputs 0 ₁ , 0 ₂ , 0 ₃ , 0 ₄ of 48, and the outputs 0 ₁ , 0 ₂ , 0 ₃ are all "0" as video signals V _Y ′, V _M ′, V _C ′.
is output, and "1" is output as the black component to output _O4 .
is output. The output “0” of output 0 ₁ , 0 ₂ , 0 ₃ is
A/D converters 59, 60, 61, comparators 63, 6
4 and 65, each data D _Y , D _M , D _C = 0, and the black component = "1" is selected at the subsequent stage as black data D _BK = 1 by timing at the gate 62. Ru. As a result, in the multiplexer 48, the yellow, magenta, and cyan data are blank in the black component part of the document, and in the non-black part, the yellow, magenta, and cyan data are processed as data with each density, and the black component will be blank, and in the subsequent stage, it will be automatically selected and controlled so that black pixels do not overlap with other pixels when printing.

In this embodiment, before A/D converting the analog signal obtained from the CCD, each color component signal is sampled to create a black component, and during this time,
Although we adopted a method of switching each color signal using a multiplexer, other methods, such as sampling the digital value of each color after A/D conversion to create a black component, are also possible. It can be easily inferred that the same effect can be obtained even if the switch is made with .

In the embodiments described above, the means for generating a plurality of color component signals are used as CCDs 38, 39, and 40 in FIG.
And so.

a first processing mode that performs halftone processing suitable for halftone components when performing area gradation processing on digital signals corresponding to the color signal components in order to reproduce images corresponding to the color component signals; a sixth processing means having a second processing mode for converting into an image signal having two different states in which the black component is emphasized and suppressing deterioration of the edge portion in order to reproduce an image with high sharpness of the black component; Dither matrix 6 for performing processing suitable for halftone components shown in the figure
6, 67, 68, A/D converter 59, 60, 61
and “1” and “0” indicating level-enhanced black areas.
The circuit includes a gate 62 for generating a signal, that is, an image signal having two different states.

Further, the processing means is provided with means for determining a black area from a plurality of color component signals before halftone processing.
The circuit shown in 0 is used.

Further, a control means for controlling the processing mode of the processing means to the second processing mode on the condition that the discrimination means discriminates a black area is set to I ₁ , I 3 , I 5 , I 1 , I ₃ , I ₅ , A multiplexer 48 whose state is switched to select _I7 is used.

In addition, this device performs the above-mentioned signal processing on the color component signals read from the CCD, but it also processes the image data for each color stored in other scanner devices or other memory devices. hand,
It is also possible to perform similar data processing.

Furthermore, a device that creates a BK component from image data for each color and determines whether yellow, magenta, and cyan data in the same pixel area are valid or invalid based on this BK component also blocks the transmission of the signal. Needless to say, it is included in the circuit.

As explained above, according to this embodiment, it is possible to extract a black component without turbidity with a simple configuration, and to reproduce an image with high sharpness of the black component.
In addition, since all data of each color component is blank in the black part, it is possible to reproduce an image without turbidity.

<Effects of the Invention> According to the present invention described above, since the black area is determined from a plurality of color component signals before halftone processing, the processing efficiency is higher than when determining the black area after halftone processing. When performing area gradation processing on digital signals, the first mode performs halftone processing suitable for halftone components, and the second mode for black components enables accurate discrimination between halftone color images and black areas. Both of these can be reproduced with high quality, suppressing the deterioration of the edge parts of black parts in particular, and emphasizing the black component, so that, for example, the sharpness of black text parts is also improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the spectral reflectance of the developing material, Fig. 2 is a block diagram showing the signal processing circuit of a conventional image processing device, and Fig. 3 is a diagram showing the relationship between the threshold value of each color component and the color component of a pixel. 4 is a schematic configuration diagram of an image reading device used in an embodiment of the present invention, FIG. 5 is a diagram showing the spectral reflectance of a dichroic mirror, and FIG.
The figure is a block diagram showing the signal processing circuit of the image processing apparatus according to this embodiment, and FIG. 7 is a diagram showing the relationship between each color signal and the black signal. In the figure, 38 to 40 are CCDs, 47 is a delay circuit, 48 is a multiplexer, and 59 to 61 are A/Ds.
Converters 66-68 are dither ROMs.

Claims (1)

[Scope of Claims] 1. Means for generating a plurality of color component signals, a means for generating a plurality of color component signals, when performing area gradation processing on a digital signal corresponding to the color signal components in order to reproduce an image corresponding to the color component signals; A first processing mode that performs halftone processing suitable for the image, and an image signal that has two different states in which edge degradation is suppressed and the black component is emphasized to reproduce an image with high sharpness of the black component. processing means having a second processing mode for converting; means for determining a black area from the plurality of color component signals before halftone processing by the processing means; an image processing apparatus, comprising: a control means for controlling a processing mode of the image processing mode to the second processing mode.