JPS6113769A - Image forming method - Google Patents

Abstract

PURPOSE:To reproduce a desired image with high sharpness and high accuracy by separating some chromatic color levels from the achromatic color levels after selecting each filter characteristics as well as a constant and at the same time formings specific chromatic color level in a black or white achromatic color area. CONSTITUTION:The light corresponding to an original picture is made incident on CCD41 and 42 respectively via a magenta filter MF and a cyan filter CF. Then the reverse signals of the output [M] of the CCD41 on which the light containing R and B components is made incident and the output [C] of the CCD42 on which the light containing G and B components is made incident are delivered. Here a/(a+b)=k (0<k<1) is satisfied (a, b = optional constants) to obtain a synthetic signal a [M]+b[C']. Then the characteristics of filters set at the preceding stages of the CCD41 and 42 respectively are selected together with the selection of constants (a, b) to satisfy 1/3<k<2/3. Thus only the chromatic signal levels (C, G, R and M) can be separated from the achromatic color levels (w and b) among all chromatic colors (G, Y, R, M, B and C). While chromatic color levels (B and Y) are formed in a black or white achromatic color area.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to an image forming method, particularly an image reading method and printer copying method for simple color discrimination between chromatic colors and achromatic colors, or between chromatic colors. BACKGROUND ART Conventionally, as color image processing, image signal processing for color printing, electrophotography, color scanners, etc. are known. All of these are created by color separation of the three primary colors (Blue B1 Green G Rud R) for image formation (3-1)
It is necessary to obtain color information. For example, according to a known full-color process electrophotographic copying machine, for example, after a photoreceptor is charged with corona, an original image is exposed through a red filter, developed with a cyan developer, and the resulting cyan visible image is once placed on copy paper. Transfer to. Next, the photoreceptor is exposed with a green filter in the same manner as above, and after development with a magenta developer, a magenta visible image is transferred onto the same copy paper in alignment with the cyan image. Further, the same process as above is repeated using a blue filter and a yellow developer, and the image is transferred to match the previous two images. Then, if necessary, the final color image of the print is fixed. On the other hand, masking technology, which is a color correction method in color printing, is known as image processing based on two color information. For example, according to the positive masking method, at the stage of plate making for each color, a separated positive image of the required density created from another color separated negative image is superimposed on a separated color negative image consisting of a single color. Color corrections are being made.

A technique in which such a masking method in printing is applied to electrophotography is disclosed in Japanese Patent Application Laid-Open No. 52-3430. According to this known technique, a first electrostatic charge image is formed on a photoreceptor, a second electrostatic charge image is formed on a photosensitive screen, and a first electrostatic charge image is formed in accordance with the second electrostatic charge image. A technique is known in which the first electrostatic charge image is corrected by irradiating a charge flow with a polarity opposite to that of the first electrostatic charge image. For example, magenta color can be reproduced by this, but this is only based on the premise of color correction. Therefore, it is not intended to separate chromatic colors from achromatic colors, and in particular it is not possible to separate chromatic color levels on either side of the achromatic angle level.

3. OBJECT OF THE INVENTION An object of the present invention is to provide a method that can reproduce images consisting of chromatic colors and achromatic colors clearly, with high precision, and with easy control.

4. Structure of the invention, that is, the image forming method according to the present invention obtains a plurality of image information from an original image by an optical means, multiplies the signal level of each of these image information by an arbitrary constant, and synthesizes it. The signal level of some of the chromatic colors is formed within the achromatic region between the black signal level and the white signal level regardless of the constant, and the signal level of some of the other chromatic colors is The method is characterized in that the optical means is selected and the constant is selected such that a portion is separated from the achromatic region.

According to a preferred embodiment of the present invention, different color information [A1], [N] from the original image are inversely related to each other.
By combining the chromatic information to be separated, it is possible to separate the chromatic information to be separated into both sides of the achromatic color level. One way to extract the different color information mentioned above is to expose the original to light in different wavelength ranges. For example, as shown in FIG. 1, when the original 44 is exposed to light of color A,
An output signal of color information [A,] is output. Similarly,
If exposed to light of a certain color, an output signal of color information [A,] can be obtained. These output signals may be the potential of the photoreceptor, or the output voltage or current of the photodetector, and such output signals may be generated not only by exposure to light in different wavelength ranges as described above, but also by exposure to light from the original. It can be obtained by applying a filter K to the light of K. When combining the two types of color information described above, one of the color information, for example, [A,] is inverted to form [N], as shown in FIG. Here, "inversion" may be a positive-negative relationship, or refers to a state in which the electrical polarity is reversed. Such synthetic information, for example (A, ) -1-
In [A, ), the achromatic color level.

The chromatic levels are separated on either side of the .

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

First, in order to understand the color characteristics of the various filters used in the following examples, Figure 2 shows the reflectance of each color of light: yellow (Y), magenta (M), cyan (C), blue (
B), green (G), and red (R).

Next, FIG. 3 is a schematic diagram of essential parts of an example of a color image forming apparatus used to carry out the method of the present invention. In this apparatus, a photosensitive drum 1 uniformly charged by a scorotron charger 30 is subjected to image exposure in a pattern corresponding to an original image or a document (not shown) by an electrostatic latent image forming means 31. A latent image is formed. According to the present invention, this electrostatic latent image
The image information is composed of image information that is synthesized so that the chromatic color level and the achromatic color level can be separated as described later. Therefore, this electrostatic latent image is formed by developing units 13A-13B, 13C, . . . for developing each color arranged around the photosensitive drum 1.
(Actually, as many developing devices as the number of colors desired to be reproduced are arranged, but three developing devices are shown as an example in the drawing.) Each color or a mixed color is sequentially developed. After the toner image of each color visualized in this way is formed on the photoreceptor drum 1, before the toner image is transferred, the exposure lamp 33 irradiates the area of the photoreceptor drum 1 where the toner image is formed, and the transfer device 34 supplies the toner image. This toner image is transferred onto a recording paper (its path is indicated by a broken line 35) fed from a paper device (not shown). The recording paper is heat-fixed by a fixing device 36, which includes at least one heated roll, and then discharged outside the machine.

On the other hand, after the transfer has been completed, the photosensitive drum 1 is neutralized by the static eliminator 37, which was not used during the toner image formation, and the excess toner remaining on the surface is removed by the cleaning that was canceled during the toner image formation. It is removed by device 38.

In the color image forming apparatus described above, the latent image forming means 3
1 (for example, a laser light source) is supplied with an output obtained by processing image information based on reflected light (or transmitted light) 32 from an original image as follows.

That is, the reflected light 32 is guided to a half mirror 40 through a lens 39, where it is split into lights 32a and 32b. Each of the elements 32a and 32b is a solid-state image sensor, for example, a CCD (Charge Coupled D
evice'-charge-coupled device) 41 and 42, and each COD output is obtained. These are then input to the image signal processing section 43, but at this time, for example, CC
The output level of D42 is inverted and output to the other CCD.
It is combined with the output of 41. This composite signal is sent to the latent image forming unit R31, and an electrostatic latent image corresponding to the composite signal is formed on the photosensitive drum 1.

To explain this in detail with reference to FIG. 4, the original image 44 has green color G1 yellow color Y1 as shown in the figure.
It is assumed that the image includes chromatic image portions consisting of red, R1, magenta, M1, blue, B1, and cyan C, and achromatic image portions, consisting of white, W1, and black. The light 32a corresponding to this original image is sent to the CCD 41 via, for example, a magenta filter MF, and the light 32b is sent to, for example, a cyan filter CF.
The light is made incident on the CCD 42 via. As a result, the C CD 41 into which the light consisting of the R%B component entered,
The output levels shown in the figure are obtained from the CCD 42 into which the light consisting of G and B components is incident. Among these outputs, the output (C) from the CCD 42 is inverted as shown in the figure in the image signal processing unit 43 (the inverted signal is indicated by []), and is further synthesized with the output CM from the other CCD 41. be done. And this composite signal (CM)
+CC)), the latent image forming means 31 irradiates the photoreceptor drum 1 with a light amount corresponding to the level of each color (image exposure). An electrostatic latent image of each color is formed from potentials corresponding to the composite signal waveform shown in FIG.

The resulting composite signal or electrostatic latent image has a specific chromatic level (GSC) on either side of the achromatic level (wl, b).
, R, M), which can be selectively separated from the neutral color level.

On the other hand, the other chromatic color levels (Y, B) are equal to the achromatic color level and cannot be separated. Therefore, each of the above chromatic colors (G, C) is calculated based on the achromatic color level.

A color image of a desired color (single color or mixed color) can be obtained by developing the two colors separately (the shaded area in FIG. 4 represents the developable area).

Here, in the above signal synthesis, each output [M] and [at] are respectively multiplied by an arbitrary constant as shown below.

Combined signal = a [M) + b (Te] (However, a and b are constants: in the example of Fig. 4, a = 1, b
=1) The level of each image part of each output is as follows.

(Margin below, continued on next page) Image part G Y RM B Cw b CM] 1-! --! -0-2--! -OX [at] 11
o ll (However, the difference between the W level and the b level is assumed to be 1) Therefore, the composite signal: a[:M]+b[C:] can be expressed as follows (a and b are dynamic ranges).

Image part GYRMBCvb a[:M)+b(C) a-)"'"'See 1 pile 82
2 2 z 2 pb 11 & where a
The absolute value of and b is arbitrary, and only the ratio matters. ), and the above composite signal can be expressed as follows.

Image part G Y RM B Cw b k(M)-t(1-k) [shi]
2 2 2 21211 represents this relationship, the horizontal axis represents this relationship, and the vertical axis represents K k(:M)+ (1-
k ) Cσ] is shown in Figure 5.
In this figure, the shaded area is the achromatic color level (hereinafter the same) 0 For example, if there are two gray (g) image areas on the original document, the area corresponding to each gray image area is gt: [R(g,)) [:Y(gl))=Hot 3
The following outputs are obtained: (R(g,)) --(Y(gt):)-3. However, gr is gray close to white, g
! is a gray color close to black. When the composite signal of each of these outputs is shown in FIG. 5(A), kl:R(g, ))+
(1-k)I:Y(g))-Snoring±k("(g"))+(
, 1-k) (Y(g,): l = ", which is indicated by the dashed line in Figure 5. That is, all the achromatic color levels pass through (T, T) in the diagram, and the above It is represented by a straight line included in the shaded area.

As can be understood from Fig. 5, if each filter characteristic to be placed before C0D41.42 is selected and the values of the constants a and b are selected and 1<k<2, then all chromatic colors Among (G, YSR, M, BXC), chromatic colors (C
, G, R, M) can be separated from the achromatic (w, b) levels. On the other hand, the chromatic color level (BSY) is within the achromatic region (between black or white levels) regardless of the above constants, becomes a gray level, and cannot be separated from the achromatic region. Furthermore, if 0(k≦incense), only R and C will be separated, and if old≦k(1), only 01M will be separated.

FIG. 6 shows another example, in which the above-mentioned 32b
, 32a, a cyan filter CF and a yellow filter YF are arranged, respectively. Therefore, as shown in the figure, an output (Y) is obtained from the COD 42, and an output [C] is obtained from the COD 41. By inverting the output (Y), multiplying the dynamic range by 5, and combining it with the output [C] which has the dynamic range multiplied by 8, the achromatic color level w, b
Specific chromatic color levels Y, R and B, C are separated on either side of the image.

This composite signal (a (C) + b (Y'), or k (C) + (1 to k) (Y)) can be expressed as follows.

Image part = G Y R' MBCwb -a+b a a[c)+b[Y) --+b a+' ” ”
b ak(C)+(1-k)[,Y″l-!-1-Eshiki I If a and b are selected within the range of , it is possible to separate specified chromatic color levels (Y, R, , B, C) on both sides of the achromatic color level. Other chromatic color levels (G.

M) is achromatic regardless of a and b above and is equal to 'pel' and cannot be separated. Furthermore, if O<k≦incense, then Y
, B are separated, and if heat≦k(1), only R and C are separated.

In all of the examples shown in FIGS. 3 to 6 above, a plurality of pieces of image information are obtained digitally (as output from a solid-state image pickup device, for example, a CCD) from the original image of a document, and these pieces of information are synthesized. Of course, as other output combinations,
A (M)+b(Y) (a combination of a magenta filter and a yellow filter), etc. can be considered. In addition to the laser light source, the latent image forming means 31 described above may include an LED,
LCD.

A light source using an ECD or the like may be employed, or an electrostatic recording means using a multi-stylus, an ion control electrode, etc.
Direct printing means such as an inkjet or a thermal recording head may be used instead of the means 31 described above. In the case of an inkjet method, the developing device shown in FIG. 3 is not necessary, and images can be directly recorded on recording paper.

Next, another image forming apparatus will be explained with reference to FIG.

However, in this example, parts common to those in FIG. 3 are given common reference numerals and their explanations are omitted.

According to this example, a half mirror 50 is disposed in the path of light from the original image, and the reflected light from the half mirror 50 is made to enter the photosensitive drum 1 via the filter 51, while the half mirror 5o Filter 52 for transmitted light
After the CCD output is processed by the image signal processing section 54, the image information transmitted through the filter 51 and the recording means 55 are processed into the image signal processing section 54. Synchronization is achieved on the photoreceptor 1 by the processing section 54.

To explain this process with reference to FIG. 8, the filter 51
By using a yellow filter as a filter, light from the corresponding image area of the original is incident on the photosensitive layer 56 of the photosensitive drum 1, which has already been negatively charged over the entire surface, and selectively eliminates the negative charges on the surface. . On the other hand, the filter 52
By using cyan filter as ccD
An output as shown in FIG. 53 is obtained, which is processed by an image signal processing section 54 and converted into a voltage applied to an electrostatic recording means 55 or an ion current to a photoreceptor. Then, when the recorded information by the recording means 55 and the image information on the photoreceptor are combined on the photoreceptor, the result is as shown in the figure (same as in FIG. 5).
, only specific chromatic color levels Y, R, and BSC are separated on both sides of the white level W and the black level b, respectively.

In the examples shown in FIGS. 7 and 8, a plurality of pieces of image information are obtained digitally on one side and analogously on the other.
The two pieces of image information have an inverted relationship in that they have positive and negative potentials on the photoreceptor, and are similar to the example described above.

Next, an example in which the present invention is applied to an image forming apparatus using a photosensitive screen will be described.

As shown in FIG.
The document 44 placed on the document table 61 is illuminated by an illumination lamp 62 . 63.6
4 is a mirror, 39 is a fixed lens, and 47 is a half mirror. A photosensitive layer 5 is formed on the surface of a drum-shaped photoreceptor 1.
6 is provided, and when the photoreceptor 1 rotates clockwise, the photosensitive layer 56 is uniformly charged by the corona charger 24.
The photosensitive layer 56 is made of selenium (C is made of an organic semiconductor or the like).

Around the photoreceptor 10, there are a charger 24 that uniformly charges the photoreceptor layer 56, and developers 48 and 49 that contain toner of each color.
... (However, actually G, YSR, M.

A developing device for a desired color among B, C, and b is arranged, and two developing devices are shown as an example in the drawing. ) etc. are arranged.

On the other hand, a cylindrical photosensitive screen drum 17 is disposed on the outside of the photosensitive drum 1 so that the photoconductive layer faces, and this drum 17 is rotated counterclockwise in synchronization with the document table 61 and the photosensitive layer 56. It is arranged so that it can rotate in the direction.

Further, around the outside of the drum 17, a screen charger 28 and a screen charger 69 made of an EL (electroluminescence) plate or an AC corona charger for removing charges remaining on the photosensitive screen drum 17 are provided.
A charged particle source (corona discharger) 19 that projects charged particles to a position facing the photoreceptor 1 inside the photosensitive screen drum 17 is provided.

A portion of the photosensitive screen 17 is shown in FIGS. 10A and 11. As shown in Figure A, a conductive screen 11 made of stainless steel or the like has a large number of fine openings of 10° and has one side exposed, and an insulating layer 13 made of methacrylic resin or the like provided on the other side of the conductive screen. and a conductive layer 14 for bias such as M formed by vapor deposition or the like on this insulating layer.
and a photoconductive layer 15 made of azo dye, selenium, amorphous silicon, cadmium sulfide, zinc oxide, or the like.

Note that the photosensitive screen 17 may have another structure, for example, it may have a layered structure as shown in FIG. 10B. Furthermore, other known layer configurations may also be employed.

FIG. 11 shows a process of selectively depositing charges on the photosensitive drum 1 using the photosensitive screen 17 to form a positive latent image. First, as shown in FIG. 11A, the photoconductive layer 15 is negatively charged over the entire photosensitive screen 17 using the first charger 28, and then the photoconductive layer 15 is charged negatively over the entire photosensitive screen 17.
As shown in the figure, when positive ion particles are projected onto the photosensitive screen 17 from the particle source 19 whose negative charges are selectively annihilated or reduced by the image exposure 32, positive ion particles are generated in the negatively charged areas of the screen 17. It passes through the photosensitive layer 56 and adheres in a predetermined amount in a predetermined pattern on the photosensitive layer 56, forming a positive electrostatic latent image. Note that ■ in Figure 110 is a bias power supply, ■ is a discharge power supply, and ■ is a DC power supply.

FIG. 12 shows an example in which a photosensitive screen 17' having a two-layer structure different from the above is used, and the screen 17' after image exposure is
When negative ion particles are projected onto the photosensitive layer 7' from the charged particle source 19 by the discharge power source 2', the ion particles pass through the exposed area and form a negative electrostatic latent image (negative) on the photosensitive layer 56.

Next, an image forming process using the photosensitive screen 17, for example the screen shown in FIG. 11, will be explained with reference to FIG. However, in this figure, the screen is shown schematically.

First, the entire surface of the photosensitive screen 17 and the photosensitive layer 56 are negatively charged, and then imagewise exposed to light from the original 44 .

At this time, a cyan filter CF and a yellow filter YF are respectively arranged after the half mirror. As a result, a predetermined amount of negative charges are left on the photosensitive screen 17 and the photosensitive layer 56 in a predetermined pattern as shown. Then, when positive ion particles 4 are projected from the charged particle source 19, these positive ion particles pass through the negatively charged area of the photosensitive screen 17 and reach the photosensitive layer 56, and the negative ion particles on the photosensitive layer 56 reach the photosensitive layer 56. A new combined electrostatic charge image is formed by the charges and the positive charges that have passed through the photosensitive screen 17 (the bias of the photosensitive screen 17 is omitted in the drawing).

As a result, a predetermined charge amount of positive or negative polarity is selectively left on the photosensitive layer 56, and as in FIG. Coloring level (
An electrostatic latent image is formed in which the negative chromatic color level (YSR) and the negative chromatic color level (YSR) are separated. Other chromatic color levels (G,
M) is equal to the achromatic color level and is not separable.

In this process, when the charge image (image information [C]) on the photosensitive layer 56 after image exposure and the charge image (image information [Y]) on the photosensitive screen 17 are combined,
The polarity of the positive ion particle image information [Y) from 9 is reversed to become composite information (C)+('Y).

Although the present invention has been illustrated above, the embodiments described above can be further modified based on the technical idea of the present invention.

For example, there may be three or more types of image information to be combined, and for this purpose the optical means may be changed in various ways. Furthermore, the method of synthesizing image information is not limited to the method described above.

6. Effects of the Invention As described above, when a plurality of image information obtained by optical means is multiplied by an arbitrary constant and combined with each other, some of the chromatic color levels fall within the achromatic color area regardless of the constant. Since the optical means and the above constants are selected so that the chromatic color level can be separated from the achromatic color area, each image can be created with the desired chromatic color and achromatic color, and the chromatic colors clearly separated from each other. Can be formed. Therefore, a desired image can be reproduced clearly and with high precision, and can be easily controlled.

[Brief explanation of the drawing]

The drawings show examples of the present invention, and FIG. 1 is a basic process diagram during image formation, and FIG. 2 (4) and (B)
, (0, (C), (G), (G) are each spectrum diagram of each color of light, Figure 3 is a schematic diagram of the image forming device, and Figure 4 is the image forming time using the device in Figure 3. Fig. 5 is a graph showing the composite signal, Fig. 6 is a process diagram of another image forming process, Fig. 7 is a schematic diagram of another image forming apparatus, Fig. 8 is a graph showing the apparatus of Fig. 7. FIG. 9 is a schematic diagram of another image forming apparatus, FIG. 10A is
Figure 10B is an enlarged 4-sectional view of a portion of the photosensitive screen, Figures 11A, 11B, and 11C are process diagrams of an image forming process using the photosensitive screen, and Figure 12 is another photosensitive screen. FIG. 13 is a process diagram of an image forming process using the apparatus shown in FIG. 11. In addition, in the symbols shown in the drawings, 1...... Photosensitive drums 13A, 13B, 13C, 48, 49...
・Developer 17......Photosensitive screen 19...Charged particle source 31.55... ...Latent image forming means 40.4
7・・・−・・・・・・Dichroic mirror 41.42
．． 53...CCD (charge coupled device) 43.5
4... Image upper bow processing section 44...
・・・・・・・・・Original image or manuscript51.5
2, YF, MF, CF...-Filter 56...
・・・・・・・・・・・・Photosensitive layer.

Claims (1)

[Claims] 1. A plurality of image information is obtained from the original image by optical means, and the signal level of each of these image information is multiplied by an arbitrary constant and synthesized. At this time, some of the signal levels of chromatic colors are chromatic color signal level is formed within the achromatic color region between the black signal level and the white signal level regardless of the constant, and at least a portion of the other chromatic color signal level is from the achromatic color region. An image forming method characterized in that the optical means and the constant are selected so as to be separated. 2. A method as claimed in claim 1, in which the chromatic levels to be separated are formed on both sides of the achromatic level. 3. The method according to claim 1 or 2, wherein the plurality of image information includes image information that is in an inverse relationship to each other at least when they are combined.