JPS6113756A - Image forming method - Google Patents

Abstract

PURPOSE:To reproduce an image containing chromatic and achromatic colors with high sharpness, high accuracy and easy control, by selecting an optical device so that some chromatic color levels are formed within an achromatic color area and that other chromatic levels can be separated from the achromatic color area. CONSTITUTION:The output [R] given from a CCD41 on which the light containing the R component is made incident is synthesized with the output [Y] obtained by inverting the output [Y] of a CCD42 on which the beams containing R and G components are made incident with picture signal processing. When a/(a+ b)=k (0<k<1) is satisfied (a, b = optional constants), (k) is set at the lateral axis with k[R]+(1-k)[Y] set at the longitudinal axis respectively. Thus the areas of oblique lines show the achromatic color levels as shown in the figure. Here the characteristics of filters to be set at the preceding stages of the CCD41 and 42 are selected. Thus only the chromatic color signals levels (C, G, R and M) can be separated from the achromatic color signal levels (w and b) among all chromatic levels (G, Y, R, M, B and C).

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. be.

2. Prior Art Conventionally, as color image processing, for example, color printing, electrophotography, image signal processing of color scanners, etc. are known. In all of these, it is necessary to obtain three color information by color separation of three primary colors (blue B, green G, red R) for image formation. 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 the color information of 2"'). For example, according to the positive masking method, no correction is made at the stage of plate making for each color. Color correction is carried out by superimposing a separated positive image of the required density created from another color separated negative image on a separated color negative image consisting of .

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 a first electrostatic charge image is modified by applying a charge flow of opposite polarity. 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 an achromatic color level.

3. Purpose of the Invention The purpose of the present invention is to sharply produce images consisting of chromatic colors and achromatic colors.
The object of the present invention is to provide a method that is highly accurate, controllable, and easily reproducible.

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 optical means are selected such that some chromatic (No. 4 levels) of the signal levels are formed within the achromatic region irrespective of the constant and all others are separated from the achromatic region. This is a characteristic feature.

According to a preferred embodiment of the present invention, the chromatic information to be separated is separated on either side of the achromatic level by combining different color information signals in an inverse relationship to each other from the original image. Can be done. 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 one human color, an output signal of color information 1 and 9 is output. Similarly, if you expose it to colored light, you will get an output signal with color information.

These output signals may be the potential of the photoreceptor, or the output voltage or current of the light receiving element, 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 in different wavelength ranges as described above. It can also be obtained by filtering the light from the When the two types of color information described above are combined, one of the color information, for example 0, is inverted and considered as 0, as shown in FIG. here"
"Reversed" may refer to a positive/negative relationship, or may refer to a state in which the electrical polarity is reversed.

In such composite information, for example (At) + [A,), chromatic levels are separated on either side of an achromatic level.

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 for yellow (Y), magenta (M), cyan (C), and 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, the photoreceptor drum 1, which has been uniformly charged by the scorotron charger 30, is not subjected to image exposure by the electrostatic latent image forming means 31 in a pattern corresponding to an original image or a document (not shown). 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 devices 13A, 13B, 113C, . . . for developing each color arranged around the photosensitive drum 1.
(Actually, as many developing units as the number of colors desired to be reproduced are arranged, but in the drawing, three developing units are shown as an example.) Each color or a mixed color is sequentially developed.

The toner images of each color visualized in this way are transferred to the photoreceptor drum 1.
After the toner image is formed on the photoreceptor drum 1 and before the toner image is transferred, the exposure lamp 33 irradiates the area of the photoreceptor drum 1 on which the toner image is formed, and the recording device 34 sends the toner image from the paper feeding device (not shown). Transfer this toner image to paper (the path of which is indicated by a broken line 35) K%. The recording paper is heat-fixed in a fixing device 36 that includes at least one heated roll, and then placed 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 direct image forming apparatus described above, the latent image forming means 3
1 (for example, a laser light source) VC 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 passes through the lens 39 and passes through the half mirror.
40K L1% is drawn, 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 Dev).
ice: charge-coupled device) 41.42, each C
OD output is obtained. These are then processed by the image signal processing section 4.
At this time, for example, the output level of the CCD 42 is inverted and combined with the output of the other CCD 41. This composite signal #i is sent to the latent image forming means 3h, and is placed on the photosensitive drum 1 corresponding to the composite signal #i.
A clear image is formed.

To explain this in detail with reference to FIG. 4, the original image 44 has green G% yellow Y as shown in the figure.
It is assumed that the image includes chromatic image portions consisting of red R, magenta M1, evening color B, and cyan C, and achromatic image portions consisting of white gws and black. The light 32arlI corresponding to this original image is transmitted through a red filter RF.
The light from the CD 41 and the light 932b are made to enter the C0D 42 via, for example, a yellow filter YF. As a result,"
Output levels as shown are obtained from the CCD 41 into which the light consisting of the R acid component is incident, and the CCD 42 into which the light consisting of the R1G component is incident, respectively. Among these outputs, the output (Y) from the CCD 42 is inverted as shown in the figure in the image signal processing unit 43 (the inverted signal is denoted as '[Y]), and further synthesized with the output (R) from the other C0D 41. be done.

Based on this composite signal ((R)+(Y)'), the latent image forming means 31 irradiates the photosensitive drum 1 with a light amount corresponding to the level of each color (image exposure). On the photosensitive layer of the photosensitive drum 1, electrostatic latent images of each color are formed with potentials corresponding to the composite signal waveform shown in FIG.

The resulting composite signal or electrostatic latent image has specific chromatic levels (G, C,
R, M) are formed, which can be selectively separated from the achromatic level.

On the other hand, the other chromatic color levels (Y, B) Fi are inseparable from the achromatic color level. Therefore, by developing each of the chromatic colors (G, C, R%M) separately from each other based on the achromatic color level, it is possible to obtain a color image of the desired color (single color or mixed color) (see Fig. 4). The shaded area represents the area that can be developed (same as the bottom two sides).

Here, during the above signal synthesis, each output [R] and (Y
) are each multiplied by an arbitrary constant as shown below.

Combined signal -a (R) + b (Y) (however, a and b
is a constant: In the example of FIG. 4, 1lta; 1, b=1) The level of each image part of each output is as follows.

Image section G Y RM B Cw b (R)10001101 (However, the difference between the W level and the b level is assumed to be 1.

) Therefore, the composite signal: a[R)+b(Y) can be expressed as follows.

Image part G YRM f3 Cwb Here, the absolute values of a and b are arbitrary; only their ratio matters. : (1-k), and the above composite signal can be expressed as follows.

Image part GYRMBCwb This relationship is plotted on the horizontal axis and on the vertical axis K k [R) + (1-k
XY) is shown in FIG. 5(A). In this figure, the shaded area is the achromatic color level (the same applies hereinafter). For example, if a gray (
2), then corresponding to each gray image part, y+'(it(s't)) = 4, (Y(S's
)] = heat qt: [R(ri2))=-”-(Y(r
t))=13, 3 outputs are obtained. However, 2. is gray close to white, f
, is a gray color close to black. When the composite signal of each of these outputs is represented by K in Figure 5 (A), k(R(ri2))+
(1-k) [Y(rt))-shi''tonashi, Figure 5 (A)
It is indicated by the dashed line in the middle.

In other words, all achromatic color levels pass through (,”) in the figure,
It is represented by a straight line included in the above-described shaded area.

As understood from FIG. 5(A), CCD41.42
By selecting the characteristics of each filter to be placed in the front stage of
w, b) level.

On the other hand, the chromatic levels (B, Y) Fi exist within the achromatic region and cannot be separated from the latter region.

FIG. 6 shows an example in which a combination of magenta filter MF and cyan filter CF is used as the filter in FIG. 4. Therefore, the outputs of each CCD 41 and 42 are as shown in the figure.The output of CCU) 42 is inverted to become [C], and when combined with the other output [M], this composite signal (a [M] )-tb(C), also ak [M]
+(1-k)EC]) is as follows.

Image part G Y RM B Cw b When this composite signal is illustrated, it is K p as shown in Fig. 5 (B).
, from the achromatic color level to some chromatic color levels (G, C, R
, M) (in Figure 6, a=b=1
).

FIG. 7 shows another example, in which the above-mentioned 32h,
A green filter GF and a red filter are placed in the optical path of 32g.
RF is arranged. Therefore, as shown in the figure, CCD4
From C'CD41, output [R] is output from C'CD41.
I3 can be obtained. If the output CG) is inverted and synthesized, a specific chromatic color level G is created on both sides of the achromatic color level w1 b.
, C, R, and M are separated.

This composite signal (a[:R:]+b(G), or k[R':!ten(1''k)[G)] can be expressed as follows.

Image part G Y RM B Cw b a(R)+b[G:] a+b b Q Q a a
+b b ak(R]+(x-kXG) 1 x-ko
o kl x-kk This is shown in FIG.
SC, RIM) can be separated (a=1, b=1 in the example of FIG. 7).

In all of the examples shown in Figures 3 to 7 above, multiple pieces of image information are digitally extracted from the original image of the manuscript (
This is a combination of the output from a solid-state image sensor (for example, a CCD), and 7. Of course, other output combinations can be considered, such as a[R1]+bCM] (a combination of a red filter and a magenta filter), acY)+bEC) (a combination of a yellow fill and a cyan fill). In addition to the laser light source, the latent image forming means 3J may be a light source using an LED, LCD, ECD, etc., or an electrostatic recording means using a multi-stylus, an ion control electrode, etc., an inkjet, a thermosensitive Direct printing means using a recording head or the like 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 mirrors 5) is made to enter the photosensitive drum 1 via the filter 51. Filter 52 for the transmitted light of 50
The image information enters the CCD 53 via the image signal processing section 54, and then passes through the filter 51 such as a multi-stylus or ion control electrode. Synchronization is achieved on the photoreceptor 1 by 54.

To explain this process with reference to FIG. 9, 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, by using a red filter as the filter 52, an output as shown in the figure is obtained from the CCD 53, which is processed by the image signal processing unit 54 and applied to the electrostatic recording means 55 or to the photoreceptor. into ionic current. Then, when the recorded information by the recording means 55 and the image information on the photoreceptor are combined on the photoreceptor, as shown in the figure (similar to FIG. 5(A)), both sides of the white level W and the black level b are obtained. Only specific chromatic color levels G, C, R, and M are separated, respectively.

In the examples shown in FIGS. 8 and 9, a plurality of pieces of image information are obtained digitally on one side and analogously on the other.
This is similar to the above-mentioned example in that the two pieces of image information have positive and negative potentials on the photoreceptor in an inverted relationship.

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. 10, a reciprocating document table 61 is provided at the top of the main body of the apparatus, and a document 44 placed on the document table 61 is illuminated by an illumination lamp 62.

63.64 is a mirror, 39 is a fixed lens, 47 is No.1-
It's Humira. A photosensitive layer 56 is provided on the surface of the drum-shaped photosensitive member 1, and when the photosensitive member 1 rotates in the opening direction, the photosensitive layer 56 is uniformly charged by the corona charger 24. Photosensitive layer 56#''t is made of selenium, an organic semiconductor, or the like.

Around the photoreceptor 1, there are a charger 24 that uniformly charges the photoreceptor layer 56, and developing devices 48 and 49 containing toner of each color.
...(However, actually e-1G, Y, R, M, B,
C.

A developing device of a desired color is arranged among those of b, 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 be rotated in any direction.

In addition, around the outside of the drum 17, there is a screen charger 28, an EL (electroluminescence) plate for removing charges remaining on the photosensitive screen drum 17, and a screen eliminator made with a tiA'c corona static eliminator. The electric device 69 and the photoreceptor 1 are placed inside the photosensitive screen drum 17.
A charged particle source (corona discharger) 19 that projects charged particles is provided at a position opposite to the .

A photosensitive screen 1, a part of which is shown in FIGS. 11A and 12A, is a conductive screen 11 made of stainless steel or the like, which has a large number of fine openings 10 and has one side exposed.
, an insulating layer 13 made of methacrylic resin or the like provided on the other surface of this conductive screen, and a bias conductive layer 14 such as 7'cA1 provided on this insulating layer by vapor deposition or the like.
and a photoconductive layer 15 made of azo dye, selenium, amorphous silicon, cadmium sulfide, zinc oxide, or the like.

Note that the photosensitive screen 17t may have a different structure, for example, it may have a layered structure as shown in Fig. mllB. Furthermore, other known layer configurations may also be employed.

FIG. 12 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. 12A, the photoconductive layer 15 is negatively charged over the entire photosensitive screen 17 by the charger 28, and then, as shown in FIG. 12B, the negative charge is removed by image exposure 32. selectively eliminate or reduce.

Next, as shown in FIG. 12C, when positive ion particles are projected onto the photosensitive screen 17 from the charged particle source 19,
Positive ion particles pass through the negatively charged area of the screen 17 and are deposited in a predetermined amount on the photosensitive layer 56 in a predetermined pattern.
Forms a positive electrostatic latent image.

In addition, in FIG. 12C, ■S is a bias power supply, ■t is a discharge power supply, and Vs is a DC power supply.

FIG. 13 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 from the charged particle source 19 to the discharge power source 7, the ion particles pass through the exposed region and form a negative electrostatic latent image (negative) on the photosensitive layer.

Next, an image forming process using the photosensitive screen 17, for example the screen shown in FIG. 14, 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 red filter R is installed at the rear stage of the half mirror.
F and a yellow filter Yr are arranged. 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. And then,
When positive ion particles are projected from the charged particle source 19, the positive ion particles pass through the negatively charged area of the photosensitive screen 17 and reach the photosensitive layer 56, and the negative charges on the photosensitive layer 56 and the photosensitive A new combined electrostatic charge image is formed by the positive charges that have passed through the screen 17 (the bias of the photosensitive screen 17 is omitted in the drawing). As a result, charges of positive or negative polarity are selectively left on the photosensitive layer 56 with a predetermined charge amount, and the achromatic color level W
and positive chromatic color levels (R) on both sides of b.

An electrostatic latent image is formed in which the negative chromatic color levels (G, C) are separated.

In this process, when the charge image (image information [R]) on the photosensitive layer 56 after image exposure is combined with the charge image (image information [Y]) on the photosensitive screen 171, The polarity of the image information (Y) is reversed by the positive ion particles from the image information (R)+[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 the optical means may be changed in various ways for this purpose. 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 chromatic color levels are ignored regardless of the constant. Since the optical means is selected such that the other chromatic color levels are formed within the chromatic region and can be separated from the achromatic region, the desired chromatic color and achromatic color,
Moreover, six images can be formed with chromatic colors clearly separated from each other. Therefore, a desired image can be reproduced clearly and with high precision and with easy control.

[Brief explanation of the drawing]

The drawings show examples of the present invention, and FIG. 1 is a basic process diagram at the time of image formation, and FIGS. 2(A) and (B)
), (C included (Dχ(E), (F) are each spectrum diagram of each color of light, Figure 3 is a schematic diagram of the image forming apparatus, Figure 4 is the image forming time using the apparatus shown in Figure 3) Process diagrams, Figures 5 (A) and (C) are graphs showing each composite signal, Figures 6 and 7 are process diagrams for other image forming processes, and Figure 8 is for other image forming apparatuses. 9 is a schematic diagram of an image forming process using the device shown in FIG. 8, and FIG. 10 is a schematic diagram of another image forming device. FIGS. 11A and 11B are a portion of a photosensitive screen. 12A, 12B, and 12C are process diagrams of an image forming process using a photosensitive screen, and Figure 13 is a process diagram of an image forming process using another photosensitive screen. , FIG. 14 is a process diagram of image formation using the apparatus shown in FIG. 10. In the reference numbers 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 40.47... dichroic mirror 41.4
2.53...CCD (charge coupled device)43.
54... Image signal processing section 44... Original image or original 51.52, YF, RF, MF, C
F, GF... Filter 56... Photosensitive layer. Agent Patent Attorney Hiroshi Aisaka Figure 10 Figure 11A Figure 118 Figure 12A Figure 12C q Figure 13 Figure 14 ↓ 8 (Currently appointed [)]

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 A method for forming an image, characterized in that the optical means are selected such that, regardless of the constant, the signal level of a chromatic color is formed within the achromatic region and all others are separated from the achromatic region. 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.