JPS6148871A - Formation of polychromatic image - Google Patents

Abstract

PURPOSE:To suppress the rise of the cost of a device by reproducing the achromatic color part of an original only with black toner and improving its picture quality, and detecting light of specific wavelength and discriminating between a chromatic color image part and the achromatic color image part. CONSTITUTION:The chromatic color image part varies in reflection factor with colors in a <=700nm wavelength range, but has high reflection factors to all colors in a >=700nm wavelength range, but the reflection factor of a black part is high in the >=700nm wavelength range. This difference is utilized to turn on the light emission part of an LED array 3 when a chromatic latent image faces the light emission part, but when an achromatic color latent image faces it, the light emission part is not turnd on to discharge the charge of the achromatic color latent image, which is then erased. Only the chromatic color latent image is left on a photosensitive body 1 by said erasing operation and visualized with black dot toner BLT at a black development part 4, and the developed image is transferred to transfer paper 24 where a chromatic color visible image is already transferred. Thus, the achromatic color latent image is formed of only black color toner BLT, so a sharp achromatic color visible image having no color shift is obtained.

Description

[Detailed description of the invention] Strings] L year I 1 The present invention relates to a multicolor image forming method using a copying machine.

Prior Art Various types of multicolor image forming methods have been proposed to obtain multicolor images of two or more colors from a multicolor original.
And it has been put into practical use. The most common method is to separate the original image using three types of color separation filters: red, blue, and green, and form corresponding latent images on a photoreceptor. In this method, a visible image is created using cyan toner, yellow toner, and magenta toner, and these are sequentially transferred onto the same transfer material in an overlapping manner. In order to reproduce a black or gray achromatic image area on a document using this method, visible images of each color obtained from three types of toner are transferred onto a transfer material in a superimposed manner. Complete the gray visible image. However, the black or gray visible image obtained from such mixed colors is not pure black or pure gray, and has poorer reproducibility than the visible image obtained from black toner alone, making it difficult to obtain a high-quality image. is difficult to obtain. In addition, when visible images of different colors are transferred one after another onto the same transfer material, if they shift even slightly, color shift may occur in the completed black or gray visible image, resulting in a blurred and unsightly image. will be possible. Black image areas are often thin line images such as characters, and if there is a color shift in such an image, it becomes difficult to decipher it.

The following method has been proposed to eliminate the above drawbacks. In other words, by preparing two photoreceptors and separating the original image using a color separation filter, a visible image consisting of toner of each color is sequentially formed on the first photoreceptor. The visible image obtained from the upper achromatic image area is electrostatically transferred to a second photoreceptor, and the transferred visible images on the first photoreceptor are sequentially transferred onto the same transfer material. On the other hand,
Separately from these operations, an achromatic visible image consisting only of black toner corresponding to the achromatic image portion is obtained on the first photoreceptor, and this is transferred onto the same transfer material. This method has three unique
It is intended to form an achromatic visible image using only black toner, rather than layering seed toner to obtain an achromatic visible image. When transferring the visible image of each color, it is difficult to electrostatically transfer 100% of the visible image to the second photoreceptor, and toner remains on the first photoreceptor. Therefore, it is difficult to obtain an achromatic visible image completely from black toner alone, and it cannot be said that the above-described drawbacks can be completely solved.

One object of the present invention is to further improve the above-mentioned conventional drawbacks, to further improve the reproducibility of black or gray achromatic image areas in original images, and to provide a multifunction device capable of obtaining high-quality visible images. An object of the present invention is to provide a color image forming method.

In order to achieve the above object, the present invention provides 700 images from a manuscript.
By detecting light with a wavelength of nm or more.

Distinguish between an achromatic image portion consisting of at least one of black and gray and a chromatic image portion in the original image.

When copying an achromatic image area, use 4:F T[
i. Before or after exposing the surface of the photoconductor to light from the original to form an electrostatic latent image, or at the same time, do not form electrostatic latent images corresponding to both chromatic image areas discriminated by an eraser, or After the wart is formed, it is erased and the remaining electrostatic latent image is visualized using black toner only. When copying both chromatic image areas, the uniformly charged surface of the photoconductor is exposed to light from the original. before or after forming an electrostatic latent image.
Alternatively, we propose a configuration in which, at the same time, an erase device does not form an electrostatic latent image corresponding to the identified achromatic image area, or erases it after formation, and visualizes the remaining electrostatic latent image with toner other than black. It is something to do.

According to this configuration, an achromatic image portion can be reproduced using only black toner, and not only can a clear achromatic visible image be obtained, but also it is possible to suppress an increase in the cost of an apparatus that implements this method.

Next, the present invention will be explained in detail, but before explaining its specific configuration, the basic principle of the present invention will be explained.

The original image to be copied is formed using printing ink, toner, or various other color materials, and the reflectance of each color is as illustrated in FIG.

Figure 1 shows the wavelength on the horizontal axis and the reflectance of the original image on the vertical axis.
The broken line W is for the white part of the manuscript, the solid line Y is for the yellow part, the dashed line C is for the cyan part, the solid line M with a Δ mark is for the magenta part, the solid line G with a 0 mark is for the green part, and the X mark is added. The solid line B shows the light reflectance distribution of the blue part, and the two-dot chain line BL shows the light reflectance distribution of the black part. Comparing the reflectance of the achromatic image area, that is, the black area BL in FIG. However, all of them show high reflectance in the wavelength range of 700 nm or more. On the other hand, the reflectance of the black part is low even in the wavelength range of 700 nm or more. Therefore, by using this difference, it is possible to easily distinguish between the chromatic image part and the achromatic image part of the original image. FIG. 2 shows an example of a copying machine constructed based on this principle.

In FIG. 2, an original 13 on which a color image is formed is placed on a contact glass 14 provided at the top of the main body of the copying machine.
is placed, and this original 13 is illuminated and scanned in the same way as in a normal copying machine. That is, a light source 15 disposed below the contact glass 14 illuminates the original 13 while scanning and moving together with the first mirror 16, and the reflected light is reflected by the mirror 17, which also scans, and illuminates the imaging lens 18. and reaches the infrared transmitting mirror 19. At this time, near-infrared light of 700 nm or more included in this reflected light passes through the infrared transmitting mirror 19, and visible light is reflected by the mirror 19.

One image of the near-infrared light component that has passed through the infrared transmitting mirror 19 forms an image on the infrared sensor array 20, which determines whether the document image is chromatic or achromatic for each minute portion. be judged.

Now, to simplify the explanation, suppose that a chromatic image area CI and an achromatic image area Nl such as black characters are formed on the original 13 as shown in FIG. 3, and the light source 15 moves in the direction of the arrow X. The near-infrared light reflected by both image parts and reaching the infrared transmitting mirror 19 passes through the mirror 19, reaches the infrared sensor array 20, and enters each of its light receiving parts. The output of array 20 is the fourth
As shown in the figure, the comparison means 30 compares the array 2 with a predetermined threshold value, and the array
It is determined whether the light incident on the light receiving section 0 is from both chromatic image areas or from the achromatic image area. In this case, a large amount of near-infrared light enters the infrared sensor array 20, so
The output is higher than the threshold value, so it is determined that it is a chromatic image portion, and the output is sent to the erase device on/off control means 34, where an erase operation, which will be described later, is performed.

When the light source 15 illuminates the achromatic image area NI of the original 13, as can be seen from FIG. However, the detection level of the sensor array, that is, its output becomes lower than the threshold of the comparing means 30, and the determining means 31 determines that the image is an achromatic image portion.

In this way, the chromatic and achromatic image portions and the achromatic image portions of the original image are determined, and the information is stored in the storage means 32 (FIG. 4).

On the other hand, the visible light reflected by the infrared transmitting mirror 19 exposes the photoreceptor 1, but at this time, one color separation filter, for example, the red filter 21R, of the filter device 21 having multiple types of filters is connected to the mirror 19. The light that is brought into the optical path between the photoreceptor 1 and reflected by the mirror 19 passes through the red filter 21R.

At this time, the photoreceptor 1 rotates counterclockwise, and the surface of the photoreceptor 1 is uniformly charged positively or negatively by a charger 2 in advance. Therefore, by the above-mentioned exposure, an electrostatic latent image corresponding to the original image excluding the white background part and the red image part of the original is formed, as in a normal color copying machine. At this time, charges also remain on the photoreceptor portion corresponding to the achromatic image portion NI of the original, and a latent image is formed, but this latent image is erased by the erase device as described below.

The illustrated erase device consists of a light emitting diode array (hereinafter referred to as an LED array) 3 having a large number of light emitting sections arranged in a direction perpendicular to the paper surface of FIG. 2, and corresponds to an achromatic image area NI. Electrostatic latent image (referred to as achromatic latent image)
When passing through the light-emitting portion of the LED array 3, the LED array 3 is controlled by the control means 34 based on the information input from the determination means 31 to the control means 34 as described above, so that the LED array 3 is moved to the light-emitting portion facing the achromatic latent image. Only the latent image emits light at the right timing, and the charge of the latent image is dissipated. This is an erase operation.

Latent image corresponding to both chromatic image parts CI (referred to as chromatic latent image)
When passing through LED array 3, based on the previous information, LE
The light emitting parts of the D array 3 do not emit light, and therefore a chromatic latent image remains.

As in a normal color copying machine, the electrostatic latent image left as described above is visualized by the cyan toner CT when it passes through the cyan developing device 7 containing the toner CT. At this time, since the achromatic latent image has already been erased, toner will not adhere to this latent image.

A transfer drum 8 that is placed opposite to the photoreceptor 1 and rotates clockwise.
A transfer paper 24 supplied from a paper feeder 22 is wound around the paper, and the cyan visible image formed on the photoreceptor as described above is transferred to this transfer paper 24 by the action of the transfer charger 9. be done.

After the visible image has been transferred, the photoreceptor l is subjected to a static neutralizing action by a static neutralizing charger 10, residual toner is cleaned by a cleaning device 11, and if necessary, static neutralizing action is performed by another static neutralizing charger 12, and one copying cycle is completed. finish.

Subsequently, a second copying operation is performed in the same manner as described above, but at this time a color separation filter other than red, such as blue filter 21B, in filter device 21 is brought into the optical path. Therefore, a latent image corresponding to the light from the document transmitted through the filter 21B is formed on the photoreceptor 1, and this latent image is made visible by the yellow toner YT of the yellow developer 5. In this case, the infrared sensor array 20 performs a detection operation, and the achromatic latent image corresponding to the achromatic image portion of the document is erased by the LED array 3, just as in the first operation described above. ,
Yellow toner does not adhere to the achromatic latent image and become a visible image.

Next, the yellow visible image is superimposed and transferred onto the transfer paper 24 onto which the cyan visible image was previously transferred, and after the static elimination and cleaning operations are completed, the third operation begins. The third operation is the same as the previous operation except that the green filter 21G is brought into the optical path. Therefore, the green filter 21
Among the latent images formed in response to the light passing through G, the achromatic latent image is erased, and the remaining latent image is transferred to the magenta developer 6.
The image is visualized using magenta toner MT. This visible image is also transferred onto the transfer paper 24 onto which the visible image was previously transferred.

As mentioned above, by the three copying operations, the images are printed on the transfer paper 24.
A visible image consisting of cyan, yellow, and magenta color toners, that is, a chromatic visible image is formed. However, an achromatic visible image has not yet been formed.

An achromatic visible image is formed by the fourth copying operation, but in this operation, the light is not exposed through the red, blue, and green filters 21R, 21B, and 21G of the filter device 21 at all, or through the ND filter 21N. Body 1 is exposed. Alternatively, you can expose through a red, blue or green filter.

In short, an achromatic latent image may be formed by leaving charges on the photoreceptor portion corresponding to the achromatic image portion NI of the document. During the fourth operation, unlike the operations up to the third time, the chromatic latent image corresponding to the tangible color image portion of the document is erased in the following manner.

The inverting unit 33 inverts the information stored in the storage unit 32 when the chromatic image area and the achromatic image area of the document were previously discriminated, and the control unit 34 controls the LED array 3 to emit light based on this information. selectively emit light. That is, LED
When the chromatic latent image faces the light emitting part of the array 3, the light emitting part emits light.

On the other hand, when the achromatic latent images face each other, no light is emitted, and the charge on the chromatic latent images disappears. This erase operation leaves only the achromatic wI image on the photoreceptor 1, and this latent image is visualized by the black toner BLT of the black developer 4. This black visible image is superimposed and transferred onto the transfer paper 24 onto which the chromatic visible image was previously transferred. In this way, the achromatic latent image is not formed by overlapping yellow, magenta, and cyan toners, but is formed only by black toner, so that a clear achromatic visible image without one color shift can be obtained.

Other operations are the same as the copying operations up to the third time.

The transfer paper onto which the chromatic visible image and the achromatic visible image have been transferred is removed from the transfer drum 8, and then the visible image is fixed by the fixing device 25, and then discharged outside the machine.

According to the above-described configuration, not only can a clear intangible color visible image without turbidity be obtained, but also it is possible to suppress an increase in the cost of the copying machine. That is, to distinguish between the chromatic color image portion and the shadowless color image portion of the document.

Although it is possible to use a light-receiving element having a light-receiving section that is sensitive to light in different wavelength ranges, the cost of such an element is high. However, in the configuration shown in FIG. 2, an element capable of detecting light at a distance of 7001 m or more may be used, and the cost of such an element is generally low.

Examples of such elements include the infrared sensor array mentioned above,
An infrared CCD or the like that can sense infrared light can also be used.

In the illustrated embodiment, a black portion is shown as an achromatic image portion, but it goes without saying that a gray amorphous color image portion can be similarly reproduced using only black toner. Furthermore, the discriminated information is stored in the storage means, and the chromatic latent image is erased based on this information, but the discriminating operation is also performed when an achromatic visible image is formed, and the chromatic latent image is erased based on the information. It is also possible to do this without using the storage means, and the achromatic latent image may also be erased based on the information once stored. Alternatively, the discrimination operation can be performed only once, the information stored, and a predetermined latent image can be erased during each copying operation. In this case, the original can be pre-scanned separately from the exposure operation of the photoreceptor. Discrimination operations can also be performed by doing this.

In addition, in the illustrated example, an LED array is used as the erase device, but it is not a device that has an LED array, an FL lamp or a PLZT switching array, and a light source, or a device that emits light (a multi-stylus that can selectively erase charges on a photoconductor). It is also possible to use the following as appropriate.

The present invention is applicable not only to the case of reproducing a full-color image as in the embodiment, but also to the case of reproducing an original image of two or more colors. When copying an image, the filter device @21 can be omitted.

The toner used may be other than yellow, cyan, and magenta.

Further, any suitable lamp can be used as a light source for illuminating the original, but halogen lamps emit light energy that is infrared (700 nm or more), as shown in Figure 5.
Therefore, using this lamp is particularly advantageous because the light from the document contains a large amount of infrared or near-infrared light, making it easier to detect with an infrared sensor or infrared COD.

The erase operation for erasing the electrostatic latent image may be performed not after the latent image is formed, but after the photoreceptor is charged and before development, before or simultaneously with the latent image. You can also do this.

According to the present invention, it is possible to reproduce the details of an achromatic image of an original using only black toner, and to improve the image quality.
Since the chromatic image portion and the achromatic image portion are determined by detecting light with a wavelength of 00 nm or more, an advantage is obtained in that the rise of the varnish 1 in the apparatus can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a graph showing an example of the relationship between the reflectance of an original image and wavelength, FIG. A schematic diagram showing an example. Figure 4 is a block diagram of a device that distinguishes between a chromatic color image part and an amorphous color image part and controls the erase device. Figure 5 shows the specific energy and wavelength of light emitted by a halogen lamp. It is a graph showing an example of the relationship. ■...Photoreceptor 13...Original Nl...
Achromatic color image area CI...Chromatic color image area BLT, YT
, MT, CT...1-ner Figure 3 ↓X

Claims (1)

[Claims] Distinguish between an achromatic image area consisting of at least one of black and gray in an original image and a chromatic image area by detecting light with a wavelength of 700 nm or more from the original; When copying an image area, an eraser is used to copy the uniformly charged surface of the photoreceptor before or after exposing it to light from the original to form an electrostatic latent image, or at the same time.
When copying both chromatic image areas by not forming an electrostatic latent image corresponding to the identified chromatic image area, or by erasing it after formation and visualizing the remaining electrostatic latent image using only black toner, , before or after exposing the uniformly charged surface of the photoreceptor to light from the original to form an electrostatic latent image, or at the same time by an eraser.
Multicolor image formation characterized by not forming an electrostatic latent image corresponding to the determined achromatic image area, or erasing it after formation, and visualizing the remaining electrostatic latent image with a toner other than black. Method.