JPS6113757A - Image forming method - Google Patents

Abstract

PURPOSE:To reproduce an image with high sharpness and high accuracy by selecting an optical device so that some of chromatic signal levels are equal to a white or black signal level and that other chromatic signal levels are separated from an achromatic color area. CONSTITUTION:The output [Y] given from a CCD42 on which the beams containing R and G components are made incident is inverted at a picture signal processing part and synthesized with the output [R] given from a CCD42 on which the light containing the R component. 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 on lique lines in a figure A have achromatic color levels. The constants (a and b) are selected to satisfy 1/3<k<1. As a result, the chromatic color levels (B and Y) are equal to a black or white level regardless of the constant among all chromatic levels (G, Y, R, M, B and C). Then only the chromatic color levels (C, G, R and M) can be separated from the achromatic color levels (w and b).

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. In all of these, it is necessary to obtain three color information by color separation of three primary colors (blue, B, green, G, and 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 two color information. For example, according to the positive masking method, at the platemaking stage for each color, an uncorrected color separation negative image is superimposed with a separation positive image of the required density created from another color separation negative image. , color correction is performed0 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 the first electrostatic charge image and 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 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 is configured such that the signal level of some chromatic colors is equal to the signal level of black or white regardless of the constant and the signal level of other chromatic colors is separated from the achromatic region. The present invention is characterized in that the constant is selected at the same time as the constant is selected.

According to a preferred embodiment of the present invention, different color information (Al), (A2
), the chromatic information to be separated can be separated on both sides of the achromatic level. One way to bring out 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 A1, an output signal of color information [A1] is output. Similarly, by exposing with A2 color light, an output signal of color information [A2] can be obtained. 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 combining the above two types of color information, one of the color information, for example, [A2], is inverted to form [Te] 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 (A1
) In (A2), chromatic levels are separated on either side of the 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: 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, the photosensitive drum 1, which is uniformly charged between the scorotron chargers, 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. , an electrostatic latent image is formed. Based on the present invention, this electrostatic latent image is composed of image information synthesized so that a part (or specific) chromatic color level and achromatic color level can be separated as described later. .

Therefore, this electrostatic latent image is formed by the developing units 13A and 13B arranged around the photosensitive drum 1 for developing each color.

13C・・・・・・(Actually, as many developing units as the number of colors to be reproduced are arranged. However, in the drawing, three developing units are shown as an example.) Developed. After the visualized toner images of each color are formed on the photoreceptor drum 1, an exposure lamp is used to irradiate the area of the photoreceptor drum 1 where the toner image has been formed before the transfer, and the transfer device is exposed to light. This toner image is transferred onto a recording paper (its path is indicated by a broken line 35) fed from a paper feeder (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 during the toner image formation. Removed by cleaning equipment.

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 passes through the lens 39 and passes through the half mirror.
40, where it is split into lights 32a and 32b. Each element 32a, 32b is a solid-state image sensor, for example, C
CD (Charge Coupled Devi
ce: charge-coupled element) 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 is sent to the latent image forming means 31, and an electrostatic latent image corresponding to the composite signal is formed on the photosensitive drum l.

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 transmitted to the CCD via a red filter RF, for example.
41, the light 32b is made to enter the CCD 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 component is incident, and the CCD 42 into which the light consisting of the R and G components is incident, respectively. Among these methods, CCD
The output (Y) from the CCD 42 is inverted as shown in the figure by the image signal processing section 43 (the inverted signal is indicated by [a]), and further combined with the output (R) from the other CCD 41. Based on this composite signal ([R]-1-1:Y)), the latent image forming means 31 irradiates the photoreceptor drum 1 with a light amount corresponding to the level of each color (image exposure). As a result, electrostatic latent images of each color are formed on the photosensitive layer of the photosensitive drum 1, consisting of potentials corresponding to the composite signal waveform shown in FIG.

The composite signal or electrostatic latent image thus obtained is 1. Achromatic color 1
/bell (wXb) on both sides of the specified chromatic color level (GX
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) are equal to the achromatic color level and cannot be separated. Therefore, each of the above chromatic colors (G, C) is calculated based on 1 achromatic color level.

R, M) can be developed separately from each other to obtain a color image of a desired color (single color or mixed color) (the shaded areas in FIG. 4 represent developable areas, 1 and below).

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

Combined signal -a CR〕+b CY) (However, a and b
are constants: a=1, b=1 in the example of FIG. 4) The level of each image part of each output is as follows.

Image part G Y RM B Cw b [1] 10001101 (Y) T I T T O committee 10 (However, if the difference between W level and b level is taken as 1, then 0
) Therefore, the composite signal:'a(R)+b(Y:I can be expressed as follows (a, b are dynamic ranges).

Image part G Y RM B Cw b b bb b a(R)+b(:C) a+-b --a A+T
b aHere, the absolute values of a and b are arbitrary;
Only the ratio matters, a:b=(1k).The above composite signal can be expressed as follows.

Image part G Y RM B Cw This relationship is expressed as 1 on the horizontal axis and k(R]+(1-k)(
If Y:) is taken and shown, it becomes as shown in FIG. 5(A). The shaded area in this figure is the achromatic color level (hereinafter referred to as
similar). For example, if there are two gray (g) image areas on the original document, gl: t-R(7t)) --, [Y(gi)) =
-0. However, gl is a gray close to white, and g2 is a gray close to black. When the composite signal of each of these outputs is shown in FIG. 5(A), k(R(11
'))+(1-k)(Y(=li't))'= ``Second kcR(,Fz))-F(1-k)(Y(,!i'z
):l=early, as indicated by the dashed dotted line in FIG. 5(A).

5 In other words, all achromatic color levels are (-2, -2
) k is represented by a straight line included in the above-mentioned diagonally shaded area.

As understood from FIG. 5(A), CCD41.42
At the same time as selecting each filter characteristic to be placed in the previous stage, the values of the constants a and b are selected, and 1. If <k<1, all chromatic colors (G, YXR, M, B.

Of C), only the signal levels of chromatic colors (C, G, R, M) can be separated from the levels of achromatic colors (wXb). On the other hand, the chromatic color level (B, Y) is equal to the achromatic color level (black or white level) regardless of the above constants and cannot be separated from the latter region.

FIG. 6 shows another example, in which the above-mentioned 32a,
A green filter GF and a red filter R are respectively placed in the optical path of 32b.
F is arranged. Therefore, as shown in the figure, the CCD 42
An output CG) is obtained from the CCD 41, and an output (R) is obtained from the CCD 41. Output (R) that inverts the output [G], multiplies the dynamic range by 5, and multiplies the dynamic range by 8.
When combined, specific chromatic color levels G, C and R, M are separated on both sides of the achromatic color levels w, b.

This composite signal (a[R:l+b(G,:], or k(
R)+(・1−k)I:G)) can be expressed as follows.

Image part G Y RM B Cw b a(R)+b[:G] a+b b OOa a+b
b ak (R) + (1-1c) (G) 1 1-k
0 0 k 1 1-k k This is shown in Figure 5 (
As shown in B), selecting al b in the range 0<k<1 can also separate specific chromatic color levels (G, CXR, M) on both sides of the achromatic color level (6th In the figure, a-b-1). Other chromatic color levels (B, Y)
is equal to the achromatic color level regardless of a and b above, and is inseparable.

FIG. 7 shows an example in which the filters in each optical path are replaced with each other in FIG. 6, but chromatic color levels are formed similarly to FIG. 6. However, the chromatic color levels to be separated are reversed compared to FIG.

In all of the examples shown in FIGS. 3 to 7 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 an original image of a document, and these pieces of information are synthesized. Of course, as other output combinations,
a[:G:]+bl:C] (a combination of a green filter and a cyan filter), a(R)+b(B:] (a combination of a red filter and a blue filter), etc. As the image forming means 31, in addition to the laser light source, L
ED, 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 sensor is placed in the path of light from the original image, and the reflected light from the half-mirror I is made to enter the photosensitive drum 1 via the filter 51, while the half-mirror sensor The transmitted light is made to enter the CCD 53 via the filter 52, and after the COD output is processed by the image signal processing section 54, it is made to be input to an electrostatic recording means 55 such as a multi-stylus or an ion control electrode. When a recording signal is output from the recording means 5 to the photosensitive drum, the image information passing through the filter 51 and the recording means 5
5 is synchronized with the image signal processing section 54 on the photoreceptor 1.

To explain this process with reference to FIG. 9, the filter 51
By using a red filter as a red filter, light from the corresponding image area of the original is incident on the photosensitive layer 56 of the photosensitive drum 1, which is already entirely negatively charged, and selectively eliminates the negative charges on the surface. .

On the other hand, by using a green 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 section 54 and sent to the electrostatic recording means 5.
5 or into an ionic current to the photoreceptor.

Then, when the recorded information by the recording means 55 and the image information on the photoreceptor are combined on the photoreceptor, the white level W and the black level b are obtained as shown in the figure (similar to FIG. 5(B)).
Only specific chromatic color levels G, C, R, and M are separated on both sides of , respectively.

In the examples shown in FIGS. 8 and 9, multiple pieces of image information are obtained digitally on the one hand and analogously on the other hand, but the two pieces of image information are at positive and negative potentials on the photoreceptor. This is an inversion relationship in that it is 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. 10, a reciprocating document tray 61 is provided at the top of the main body of the apparatus, and the document 44 placed on the document table 61 is illuminated by an illumination lamp 62.

63 and 64 are mirrors, 39 is a fixed lens, and 47 is a half mirror. A photosensitive layer 56 is provided on the surface of the drum-shaped photosensitive member 1, and when the photosensitive member 1 rotates clockwise, the photosensitive layer is uniformly charged by a corona charger array.

The space between the photosensitive layers is made of selenium or an organic semiconductor.

Around the photoreceptor 10, there are a charger array for uniformly charging the photoreceptor layer I, and developing devices 48, 49, each containing toner of each color.
...(However, actually GXY, R, M, B.

The developer of the desired color is placed in C1b, but in the drawing, 2
Two developing devices are shown as an example. ) 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. It is arranged so that it can rotate in the direction.
Further, around the outside of the drum 17, there is a screen charger row and an EL (electroluminescence) plate or A for removing the electric charge remaining on the photosensitive screen drum 17.
Screen static eliminator 69 made from C corona static eliminator etc.
A charged particle source (corona discharger) 19 that projects charged particles is provided inside the photosensitive screen drum 17 at a position facing the photoreceptor IK.

As part of the photosensitive screen 17 is shown in FIGS. 11A and 12A, the photosensitive screen 17 is a conductive screen 1 made of stainless steel or the like having a large number of fine openings 10 and having one side exposed.
1, an insulating layer 13 made of methacrylic resin or the like provided on the other surface of the conductive screen, and a conductive layer 14 for bias such as M provided on this insulating layer by vapor deposition or the like,
The photoconductive layer 15 is made of azo dye, selenium dye, 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. 11B.
Furthermore, other known layer configurations may also be employed.

FIG. 12 shows a process of selectively depositing charges on the photosensitive drum 1 through 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 between the chargers, and then, as shown in FIG. 12'B, by image exposure 32. The negative charge is selectively eliminated or reduced.

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 adhere to the photosensitive layer portion in a predetermined pattern in a predetermined amount to form a positive electrostatic latent image.

Note that vl in FIG. 120 is a bias power supply, v2 is a discharge power supply, and V3 is a DC power supply.

FIG. 13 shows an example in which a photosensitive screen 17' having an i-layer structure different from the above is used, and the screen 17' after image exposure is
7', when negative ion particles are projected from the charged particle source 19 to the discharge power source v2', the ion particles pass through the exposed area and form a negative electrostatic latent image (negative) on the photosensitive layer 56. do.

Next, an image forming process using the photosensitive screen 17, for example the screen shown in FIG. 12, 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 is negatively charged, and then the image is irradiated with 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 green filter GF are arranged. As a result, a predetermined amount of negative charge is left in a predetermined pattern on the photosensitive screen 17 and the photosensitive layer portion as shown in the figure. Next, 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, causing the negative charge on the photosensitive layer to and,
A new combined electrostatic charge image is formed by 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, charges of positive or negative polarity are selectively left on the photosensitive layer 56 with a predetermined amount of charges, and as in FIG. 5(B), on both sides of the achromatic color levels W and b. Positive chromatic color level (G,
C) and a negative chromatic color level (RIM) are separated to form an electrostatic latent image. Other chromatic color levels (Y, B'
) is equal to the achromatic color level and is inseparable.

In this process, when the charge image (image information [G]) on the photosensitive layer 56 after image exposure and the charge image (image information [R]) on the photosensitive screen 17 are combined, The polarity of the image information (R) is reversed by positive ion particles from the particle source 19, resulting in composite information [G]+[R].

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, the present invention, when multiple pieces of image information obtained by optical means are multiplied by an arbitrary constant and synthesized, some of the chromatic color levels become the achromatic color level regardless of the constant. The desired chromatic color and achromatic color, because the optical means and the above constants are chosen so that the levels of other chromatic colors are equally and separable from the achromatic region,
And the chromatic colors are clearly separated 1lII￥L, 6
Can form images.

Therefore, a desired image can be reproduced clearly and with high precision and with easy control.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a basic process diagram during image formation, and FIG. 2 (A) and (B)
, (C), (D), (E), and (F) are spectral diagrams of each color of light, Figure 3 is a schematic diagram of the image forming apparatus, and Figure 4 is image formation using the apparatus shown in Figure 3. Figures 5 (A) and (B) are graphs showing each composite signal, Figures 6 and 7 are process diagrams for other image forming processes, and Figure 8 is a graph for other image forming apparatuses. A schematic diagram, FIG. 9 is a process diagram of image formation using the apparatus of FIG. 8, FIG. 10 is a schematic diagram of another image forming apparatus, and FIGS. 11A and 11B are part of a photosensitive screen. Enlarged sectional view; - Figures 12A, 12B, and 12C are process diagrams of an image forming process using a photosensitive screen; Figure 13 is a process diagram of an image forming process using another photosensitive screen; FIG. 14 is a process diagram when forming an image using the apparatus shown in FIG. 10. In addition, in the symbols shown in the drawings, 1...... Photosensitive drum 13A, 1
3B, 13CX48.49 Sichuan/Que developer 17...
......Photosensitive screen 19...
・・・・・・Charged particle source 31.55・・・・・・・・・
...Latent image forming means 40.47...
・・ Guicroic mirror 41.42.53・・・・
...... CCD (charge-coupled device) 43, charge... Image signal processing unit 44...
・・・・・・Original image or manuscript51.52,
yJr, RF, 9/cF, CF-song---7ih
p- Evil......This is a photosensitive layer. Agent Patent Attorney Hiroshi Aisaka 5 (A) Figure (B) 0'L ] Figure 10 Figure 12A Figure 12C q Figure 13 q Figure 14 Juku

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 selecting the optical means and selecting the constant such that the signal level of the chromatic color is equal to the signal level of black or white regardless of the constant and the signal level of other chromatic colors is separated from the achromatic region; An image forming method characterized by: 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.