JPS6319969A - Black separating device - Google Patents

Abstract

PURPOSE:To obtain a picture of high quality even in a black/white mode by always select a specific color information signal when the black/white recording processing is selected. CONSTITUTION:The comparators 31 and 32 compare inputs A and B with each other and outputs the results of comparieon (H:A>B, L:A <= B). Then selectors 33 and 34 select the A input (SEL = L) or the B input (SEL = H) and outputs it. A converting ROM 35 outputs a black recording signal (bk) in response to the output (x) of the selector 34 and a mode switch signal BW/FC. In a black/white mode where the signal BW/FC is kept at an H level, the output of an OR gate 36 is also set at an H level and a color information signal (m) is always supplied to a ROM 35 regardless of levels of those color information signals (c), (m) and (y). Then the signal (bk) having concentration proportional to the reflecting concentration of G (green) light to be regenerated. Thus the scattering or the shortage of the maximum concentration of a bright part are eliminated. Then pictures of high quality are obtained even in a black/white mode.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a black separation device for a full-color digital copier/printer, etc., equipped with a monochrome mode (recording using only black toner).

(Conventional technology) Full color recording (cyan, magenta, yellow).

(recorded in black), the color to be reproduced is R (red).

Concentration signals c and m for G (green) and B (blue) light.

Based on the minimum value Min (c, m, y) of y,
A method of determining a skeleton black-like black toner record lbk as shown in FIG. 1 is known. However, when black-and-white recording is performed using the black toner recording layer bk determined by this method (recording using only black toner), there is a drawback that bright areas are skipped and the maximum density is insufficient.

(Purpose) The present invention has been made in view of this background, and it is an object of the present invention to provide a black separation device capable of obtaining high-quality images even in monochrome mode, with a simple configuration, at low cost. The purpose is to

(Structure) For this purpose, the present invention fixes the color information signal to be selected when performing monochrome recording processing, or in other words, always selects a specific color information signal when selecting monochrome recording processing. This is what I did.

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a block diagram of an example of a color image processing device in a full color digital copying machine to which the speculative M device according to the present invention is applied. In the figure, c, m, and y are the signals that separate the colors to be reproduced in the large scale picture, that is, the colors R (red) and G (green) to be reproduced, respectively.

This is an 8-bit color information signal representing the reflection density of B (blue) light. Do you want to perform black and white mode processing in BW/D? (H
(high level) or perform full color mode processing (
This is a mode switching signal for switching between low level and low level.

21 are color information signals c, m, y and mode switching signal BW/
8 represents the recording density of black (Bk) l-toner based on F.
This is a black separation device that outputs a bit black recording signal bk.

Reference numeral 22 indicates a density valve for recording with black toner according to a black recording signal bk outputted by the black separation device 21, and color information signals c, m, y.
This is an under color removing device that performs density correction and outputs 8-bit chromatic axis signals c', m', y' representing the corrected density. 23 is the corrected color information signal c l , m
A so-called masking process is performed based on J, y', and an 8-bit color recording signal C'' representing each recording density of cyan (C), magenta (M), and yellow (Y) toner is generated.

This is a masking processing device that outputs m'' and y''.

As mentioned above, the color image processing device shown in FIG.
Color information signals c, m, y representing the colors to be reproduced are recorded as recording signals bk, c' representing the i3 depth of each toner.

Processing to convert into m″, y″ is performed.

Next, the black separation device will be explained in detail.

FIG. 3 is a circuit diagram of an embodiment of a black separation device according to the present invention.

In the figure, 31.32 is a comparator that compares each 8-bit A and B input and outputs the result (H:A>B, LEA≦B).
36 is an OR gate, 35 is a selector that selects and outputs the B input (EL-L) or B input (SEL-H), and 35 outputs a black recording signal bk according to the output X of the selector 34 and the mode switching signal BW/F. It is a conversion ROM.

In this embodiment, in the full color mode (BW/PC-L), a skeleton black tone black recording signal bk is output. That is, when the mode switching signal BW/F is at Lo- level, the minimum (+!!Min (c, m, y) is selected and input to the conversion ROM 35.

'On the other hand, data as shown in FIG. 4 is recorded at each address (A8 to AO) of the conversion ROM 35. Therefore, in the full color mode (BW/"FC-(A8)-L), a black recording signal bk representing the recording density of black toner is output according to the conversion characteristics shown in FIG.

Next, the case of black and white mode (BW/F (, -H) will be explained. When the mode switching signal BW/FC is at H4gh level, the output of OR gate 36 is also at High level. Therefore, the conversion ROM 35 has color The color information signal m is always input regardless of the magnitude relationship of the information signals C3m and y.On the other hand, in the case of monochrome mode CVI/FC<=A8)-11), the conversion characteristics of the conversion ROM 35 are also It becomes a linear characteristic as shown in Figure B. That is, according to this embodiment, in the monochrome mode, a color information signal m, that is, a black toner recording signal bk having a density proportional to the G (green) light reflection degree of the color to be reproduced is output. Therefore, skipping of bright areas and lack of maximum density are eliminated, so high-quality images can be obtained even in black-and-white mode.

FIG. 5 is a timing chart of the black minute g device shown in FIG.

In the figure, BW/F=1. When (left case), OR
Gate 36 acts as a buffer. Therefore, when color information signals c, m, and y are input, the comparator 31 outputs C and y.
, and outputs the result S.

Next, the selector 33 selects either c or y according to S+ and outputs the result Y1. Next, the comparator 32 outputs Y,
and m are compared and the result S2 is output.

Next, the selector 34 selects one of Y, , m in response to S2 and outputs the result Y2. Next, the black generator 35 outputs a black recording signal bk in accordance with Y2.

On the other hand, when BW/lower = H (right case), OR gate 3
The output of No. 6 is fixed at H. Therefore, selector 34
always selects m and outputs the result Yz ("m).

As described above, as shown in FIG. 5, the color information signals c and m.

A delay time tI + t2 occurs from when y is input until the black recording signal bk is determined, but by latching the black recording signal (bk) with the synchronization signal (CLK), the phases are aligned in Fig. 5. (Synchronization signals and latches are not shown in FIG. 3).

Note that in FIG. 5, the shaded area represents the data transfer period.

As described above, in this embodiment, the black toner recording density is determined using a specific color information signal in the monochrome mode. This is the minimum value Mi of the color information signal as in full color mode.
Using n(C, m, y), a highly saturated color (Mirt (
c, m, y) ”-0) (7) There is a high possibility that information will be lost.

Further, as described above, in this embodiment, the recording density of black toner is determined using the color information signal m in the monochrome mode. This is because the human eye's sensitivity to visible light wavelengths is not uniform, and among R (red), G (green), and B (blue) light, G (green)
Maximum sensitivity to light. Therefore, it is better to determine the recording density of black toner using the color information signal m representing the reflection density of G (green) light, since it better matches the characteristics of the human eye.

Further, according to this embodiment, the black separation device for full-color recording can be realized by only slightly improving it, so that the structure is simple, the reliability can be improved, and it can be achieved at low cost.

FIG. 6 is a circuit diagram showing another embodiment of the black separation device.

In this embodiment, XOR (exclusive OR) gates 36 and 37 are provided.

Mode switching signal BW/ in black and white mode (BW/Fte-H)
When Tc'' is High level, XOR gate 36.3
7 operates as an inverter. Therefore, comparators 31, 32, selectors 33, 341, XOR gate 36
．． 37 are color information signals c and m.

The maximum value of y Max (c, m, y) is output to the conversion ROM 35.

On the other hand, in the case of black and white mode ((BW/FC(-A8) -H), the conversion characteristics of the conversion ROM 35 also become linear characteristics as shown in FIG. 4B. That is, according to this embodiment, in the black and white mode, , color information signals c, m, y, that is, R of the color to be reproduced
A black toner recording signal bk having a density proportional to the maximum reflection density for (red), G (green), and B (blue) light is output.

FIG. 7 is a timing chart of the black separation device shown in FIG. In Fig. 7, when BW/FC-L (7) (
In the left case), the XOR gates 36, 37 act as buffers. Therefore, when the color information signals C9m,y are input,
The comparator 31 compares C and y and outputs the result S. The selector 33 selects either c or y according to Sl and outputs the result Y. The comparator 32 outputs the result Y.
and m are compared and the result S2 is output. Next, selector 3
4 selects one of Y, . On the other hand, in the case of BW/FC-H (right case), the XOR gates 36 and 37 work as inverters, so the selector 33 selects either c or y according to da, and outputs the result Y. In addition, the selector 34 is set to 2.
Selects one of Yl and m according to the result and outputs the result Y2.

As mentioned above, as shown in FIG. 7, there is a delay time t from when the color information signals c, m, y are input until the black recording signal bk is determined.
However, by latching (bk) the black recording signal with the synchronization signal (CLK), the phases are matched in FIG. 7 (the synchronization signal and the latch are not shown in FIG. 6). Note that in FIG. 7, the shaded area represents the data transfer period. If you try to determine the black toner recording density using the minimum value Min (c, m, y) of the color information signal as in full color mode, there will be many dropout colors (for example, high chroma colors are rn, )'
) 20, so no information is recorded]. However, if the black toner recording density is determined using the maximum value Max (c, m, y) of the color tone signal as in this embodiment, the above-mentioned problem can be prevented.

(Effects) According to the present invention, by fixing the selected color information signal when performing monochrome recording processing, dropout colors can be reduced and high quality images can be obtained.

Further, since the processing for full-color recording and black-and-white recording can be executed by the same black separation device, the configuration is simple and can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram for determining the amount of black toner recorded in skeleton black tone according to a conventional example, FIG. 2 is a block diagram of an example of a color image processing device, and FIG. 3 is a diagram according to the first embodiment. A circuit diagram of the black separation device, FIG. 4 is a conversion characteristic diagram of the black signal in each mode according to the present invention, FIG. 5 is a timing chart of the black separation device, and FIG. 6 is a black separation device according to the second embodiment. FIG. 7 is a timing chart thereof. 21...Black separation device, 31.32.33,34°36
... Selection means, 35... Conversion means. Kuyo0 ■O:. Figure 6

Claims (1)

[Claims] A color information signal representing the spectral reflection density of the color to be reproduced, a mode switching signal for selecting full-color recording processing or black-and-white recording processing, and a mode switching signal among the color information signals according to at least the color information signal and the mode switching signal. A black separation device comprising a selection means for selecting one of the above, and a conversion means for converting into a black recording signal representing a black recording amount and outputting the signal in accordance with at least the selected color information signal and the mode switching signal, The black separation device is characterized in that the selection means always selects a specific color information signal from among the color information signals when selecting monochrome recording processing.