JPH0754963B2 - Image processing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image processing apparatus, and more particularly to a color image processing apparatus.

2. Description of the Related Art In an apparatus that obtains a full-color image, such as a color printer, a color copying machine, or a color printing machine, a yellow, magenta, or cyan developer or ink has been used to form a color image on the same image. There is. At this time, the black component of the original document or the black component of the copied image becomes a large factor that influences the sharpness of the image.

2. Description of the Related Art Conventionally, for example, in a color copying machine, yellow, magenta, and cyan developers are uniformly transferred to a portion corresponding to a black area of a document with high density to represent black.
However, each of the yellow, magenta, and cyan developers is not actually composed of pure yellow, magenta, and cyan components only, and has a spectral reflectance as shown in FIG. There is. For example, it is known that magenta developers contain corresponding yellow and cyan components, and cyan developers also contain some yellow and magenta components. Therefore, even when yellow, magenta, and cyan are evenly transferred, the color balance of each color cannot be obtained, and the color becomes black with some color. Alternatively, since the three color developers are superposed, the reflected light of the coloring material becomes turbid, and as a result, turbid black is obtained.

In a full-color color printer in which each pixel of yellow, magenta, and cyan can be controlled in dot units, as described above, the area of the black document is printed with yellow, magenta, and cyan at high density and uniformly to produce black. Has been realized. However, since the black portion has a color gradient and turbidity, a black coloring material is also used, and when each pixel data in the same pixel of yellow, magenta, and cyan has a level of a predetermined density or more, It is conceivable to print the color material and yellow, magenta, and cyan at the same time to express black. However, as it is, all the color materials of yellow, magenta, cyan, and black are overlaid on the same pixel, so that the color material is not well placed and the turbidity of the color cannot be fundamentally solved.

In a color printer that reproduces halftones using dot data of "1" and "0", halftones are usually reproduced by a dither method or the like. This dither method is well known and will not be described. In this case, it is possible to make a relatively appropriate expression when expressing only the halftone image, but for example, in the case of an image in which a halftone image and characters or lines are mixed, these characters and lines have sharpness. It has the drawback of being lost. Therefore, when black characters are printed on a halftone image such as a map, the characters are not clearly reproduced. On the other hand, when trying to reproduce the character sharply, the reproducibility of the halftone is extremely deteriorated.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an image processing apparatus capable of performing good image reproduction even in a black area of a document and reducing the capacity of a storage unit. To aim.

Examples Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing the entire embodiment of the present invention. The dichroic mirror 1 reflects the reflected light L reflected by the document.
And 2 separate the color into B (blue) and G (green) components,
In addition, the R (red) component is extracted using the mirror 3 coated with an infrared cut filter with a multilayer film.

Each color-separated light is photoelectrically converted by CCD (charge coupled device) 7, 8, 9 and then amplified by amplifiers 10, 11, 12 and based on the timing of clock φ sent from clock generator 16. Perform A / D conversion.

A / D converters 13, 14, 15 using the first comparator group 17, 18, 19
The digital value of each color pixel output from the CPU and the data in the dither ROMs 26, 27 and 28 in which threshold values are stored in a dither matrix are compared to obtain binary data of each color. Since this dither processing is performed by a well-known method, description thereof will be omitted. Note that 29, 30, and 31 are the dithers corresponding to the pixel positions on the image.
It is an address generator for reading the data in ROM.

In synchronization with the clock φ, the binary pixel data of each color output from the comparators 17, 18, 19 is stored in the page memory 33 for each color image. An address generator 32 supplies address information for storing pixel data for each of yellow, magenta, and cyan. 34 is a memory for each pixel data 33
It is a control circuit for controlling the storage state and read-out to and from.

On the other hand, the output values from the A / D converters 13, 14, 15 are compared with the set values of the digital switches 23, 24, 25 in the second comparator group 20, 21, 22. Then, the comparator output signals 50, 51, 52
When all the values in are "1", the pixel is "black"
Therefore, it is stored in the black memory in the memory 33 in the same manner as the binary pixel data of yellow, magenta, and cyan. As described above, the image data stored in each image information memory in the memory 33 is sequentially read in the order of yellow, magenta, cyan, and black, and the laser beam from the laser light source 39 is modulated. Reference numeral 38 is a laser driver, and 37 is a modulation circuit.

The laser beam forms a respective latent image on the photosensitive drum (not shown), Y (yellow), M (magenta), C (cyan), the transfer of each color material B _k (black), a color with image To get

FIG. 3 is a detailed circuit diagram of the modulation circuit 37 and the laser driver 38 shown in FIG. The laser light source 39 emits laser light when the transistor 42 is on. The current supplied to the laser light source 39 is about 40 to 50 milliamperes, and the constant current circuit 40 stabilizes the current.

When the output of the OR gate 46 is "1", the transistor 42 is turned off, so that laser light is not emitted. On the other hand, when the output of the OR gate 46 is "0", the transistor 42 is turned on and laser light is emitted. The control signal CNTL sent from another control circuit (not shown) is “1” when the black signal B _k is being read from the memory 33, other signals Y (yellow), M (magenta), It is held at "0" when C (cyan) is being read.

AND gate 45 when control signal CNTL is "0"
As a result, the black signal B _k is blocked, and the Y, M and C signals are sent to the OR gate 46 via the AND gates 43 and 44. On the other hand, when B _k is “1”, that is, in a black pixel,
The Y, M, and C data are not output. In this way, the output of Y, M, C data is controlled by the B _k data. And when printing black, keep CNTL = "1", B _k
Only data is output.

Effects As described above, according to the present embodiment, a black image having a predetermined density or higher is extracted based on the data representing each color image, and halftone reproduction processing is performed on the extracted black image. Since it is not performed, black characters and black lines can be sharply reproduced with an easy configuration, and by controlling so that the yellow, magenta, and cyan dots do not overlap the black dots, the color It is possible to improve the turbidity and the mounting condition of the coloring material.

[Effects of the Invention] As described above, according to the present invention, since the first storage means for storing the digitally processed color component signals of a plurality of colors for one page is included, when forming a plurality of color component images. In addition, it is not necessary to scan the original a plurality of times, and a full-color image can be formed by reading the color component signal once stored in the first storage means for one page a plurality of times. Since the determination result of 1 is also stored for one page corresponding to the color component signal, the black area can be reproduced well.

Further, since the information amount of the A / D-converted multi-valued color component signal is reduced and then stored in the first storage means, the first storage means is different from the case where the multi-valued color component signal is stored as it is. While reducing the capacity of the
Since it is performed based on the multi-valued color component signal before the amount of information is reduced, it is possible to accurately determine.

[Brief description of drawings]

FIG. 1 is a diagram showing the spectral reflectance of a coloring material, FIG. 2 is a configuration diagram showing an entire embodiment of the present invention, and FIG. 3 is a detailed circuit diagram of the modulation circuit and laser driver shown in FIG. Is. 1,2,3 …… dichroic mirror, 4,5,6 …… mirror, 7,8,9 …… charge coupled device, 10,11,12 …… amplifier, 13,14,15 …… A / D conversion Device, 16 …… Clock generator, 17,18,19,20,21,22 …… Comparator, 23,24,25 …… Digital switch, 26,27,28 …… ROM, 29,30,31,32 ...... Address generator, 33 ...... Image page memory, 34 ...... Control circuit, 35 ...... AND gate, 37 ...... Modulation circuit, 38 ...... Laser driver, 39 ...... Laser light source, 40 ...... Current source, 41 , 42 …… transistor, 43,44,45 …… and gate, 46 …… OR gate, 47,48 …… inverter, R1, R2 …… resistor, 50,51,52 …… comparator output signal.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03F 3/08 A G03G 15/01 115 B41J 3/04 101 A

Claims (1)

[Claims] 1. A photoelectric conversion means for photoelectrically converting reflected light reflected by an original to generate color component signals of a plurality of colors, and a plurality of color component signals generated by the photoelectric conversion means are digitalized for each color component. A / D conversion means for converting into a signal and outputting a plurality of multi-valued color component signals, and processing the plurality of multi-valued color component signals output by the A / D conversion means in block units of a predetermined size, and Processing means for reducing the amount, first storage means for storing one page of a plurality of color component signals processed by the processing means, and a plurality of multi-valued color component signals output by the A / D conversion means A second storage for storing a determination unit for determining a black region of the original from the color component signal before the amount of information is reduced by the processing unit, and a determination result of the black region for one page by the determination unit. Means and the second memory A control unit for suppressing the output of the color component signals of a plurality of colors read from the first storage unit in the black region by using the determination result of the black region read from the stage, and the output is controlled by the control unit. And an image forming unit that sequentially forms an image in accordance with the generated color component signals of a plurality of colors.