JPH04136872A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To form the digital latent images of a pattern which are different in developing color by automatically selecting a generated dotting signal and successively outputting it to a digital scanning system when the digital latent images corresponding to respective developing colors are started to be formed. CONSTITUTION:A laser scanning system 26a drives and modulates a laser beam based on an inputted processing signal, and an analog latent image formed on a photosensitive body 5 is one-dimensionally digitally exposed and one line of digital/analog latent images is formed. As a counter 35 is successively incremented, a selector 34 automatically selects a dotting pattern which is successively set, and a processing signal B is inputted in the laser scanning system 26a. By successively repeating such processing according to the counter value, a dotted pattern and the digital/analog latent image corresponding to the analog image is formed on the photosensitive body 5, and the digital/analog latent image is developed with yellow toner. The digital/analog latent image becomes a visible image of every color and is formed as a multicolor image on a fed recording medium. Thus, the optimum digital/analog image having no color slurring and no evenness of color is formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an analog scanning system that scans and exposes a document to form an analog image on a photoreceptor, and an optical signal that is modulated based on a predetermined image signal. Multicolor image formation includes a digital scanning system that scans a photoreceptor to form a digital image, and forms a multicolor image on a recording medium by developing an electrostatic latent image formed on the photoreceptor with a plurality of developers. It is related to the device.

[Prior Art] Conventionally, in this type of apparatus, a so-called analog copying machine is used, which charges and exposes a photoreceptor of a photoconductive layer to form an electrostatic latent image, and records the image by visualizing it with a powder toner. etc. have been put into practical use.

In addition, in the above-mentioned analog copying fjl, the reflected light obtained by exposing the original is imaged on the photoreceptor by sequentially switching three color separation filters (red (R), green (G), and blue (B)). , cyan (C) and magenta (M), respectively.
), yellow (Y), and sequentially multiple transfer onto a recording medium, color copying machines configured to form three-color analog full-color images have also been put into practical use.

FIG. 7 is a cross-sectional view showing the configuration of this type of multicolor image forming apparatus, in which 5 is a two-layer selenium-based photosensitive drum (photosensitive member) subjected to long-wave toning with Panchroma Dec; 7 is a static eliminator; is a charger.

A document is illuminated by a halogen lamp in an illuminator 1, and a light image is formed on a photoreceptor through a mirror, a lens 21, and a color separation filter 3. 9 to 11 are M (magenta), C (cyan)
, and Y (yellow) developing devices to develop the respective latent images with a magnetic brush. The paper fed from the paper feed unit 18 is wound around a transfer drum 13 made of a dielectric film that has the same diameter as the photoconductor 5 and rotates synchronously, and a toner image is sequentially transferred to the transfer drum 13 by a transfer charger 14. After the specified number of transfers are completed, the paper is statically removed by one separation section 15 and transferred to the fixing section 20.
The paper is then ejected. The toner remaining on the photoreceptor 5 is cleaned by a magnetic brush cleaning 17 via a static eliminator 16. Note that 19°20 is a transfer paper conveyance system.

Here, when an analog electrostatic latent image is visualized using powder toner, problems arise in terms of gradation in the visible image and poor reproducibility of solid areas.

To solve this problem (as a conventional example, select the optimal bias for reproducing high and low density areas for each of MC and Y,
There is a way to overlap two images. However, according to this method, although the color reproducibility is improved, the copying processing speed is halved, resulting in a noticeable decrease in throughput.

On the other hand, as described in Japanese Patent Publication No. 59-22231, etc., there is a recording apparatus having two types of exposure means and halftone signal generation means, in which one of the exposure means is an image exposure means, A recording device comprising an exposure means for exposing a photoreceptor to an original light image, and the other exposure means is a one-dimensional light scanning mechanism that spatially scans the photoreceptor one-dimensionally using a light signal according to an image signal. This makes it possible to improve the gradation and reproducibility of solid areas in an analog electrostatic latent image (hereinafter, the electrostatic latent image formed by the -dimensional optical scanning mechanism will be referred to as a digital/analog latent image).

Since this digital/analog latent image has good gradation, it is also a technique suitable for recording devices that multiplex multiple colors, especially three-color full-color analog copying machines.

[Problems to be Solved by the Invention] However, when multicolor visible images visualized by digital analog latent images are multiplexed, there is a problem that image deterioration such as color unevenness occurs.

This is due to registration misalignment for each color, vibration of mechanical mechanisms, etc. that occur in multicolor image devices such as full-color copying machines.

Hereinafter, the causes and problems of registration misalignment will be explained with reference to FIGS. 8 and 9.

FIG. 8 is a sectional view of essential parts of the multicolor image forming apparatus shown in FIG. 7, and the same parts as in FIG. 7 are given the same reference numerals. A gripper 23 grips the leading edge of the fed transfer paper P.

In order to reduce the size of the multicolor image forming apparatus shown in FIG. The transfer drum 13 is not spaced sufficiently apart from the transfer drum 13 in the rotating direction of the transfer drum 13. That is, the adsorption position and separation position of the transfer paper P are provided at positions that are not sufficiently spaced apart from the image transfer position in the rotational direction of the transfer drum 13, resulting in the following problems.

(1) As shown in FIG. 8(a), when the transfer paper P is relatively large such as A3 paper, the transfer sheet forming the side surface of the transfer drum 13 is covered by the transfer paper P. When pressed, vibration is applied to the photoreceptor 5, and the latent image of the first color is formed out of position compared to the latent images of other colors.

(2) As shown in FIG. 8(b), the first color transfer image is misaligned with the black color image because the transfer sheet and the transfer paper P are not in close contact with each other.

(3) As shown in Fig. 8(c), when separating the transfer paper P from the transfer sheet, vibrations may be transmitted to the formation of the final color latent image, or a shift may occur in the transfer position, so the final color The transferred image will also be out of alignment with the latent images of other colors.

Due to such a shift in the transfer position, as shown in FIG. 9(b),
As shown in (c), the patterns of each color formed by the same halftone dot signal are slightly shifted, and this causes positions where each color overlaps and positions where they do not overlap to occur at long intervals. Unlike a regular image as shown in FIG. 5A, there is a serious problem in that color moiré or color shift appears, degrading the image quality.

This invention was made in order to solve the above-mentioned problems, and it uses a -dimensional optical scanning mechanism (digital scanning system) to manually generate different image signals for each color component to create different patterns of halftone dots. By generating and inputting signals,
It is an object of the present invention to provide a multicolor image forming apparatus capable of forming an optimal digital/analog image without color shift or color unevenness by performing optimal distributed exposure at digital exposure positions based on halftone signals for each color component.

[Means for Solving the Problems] A multicolor image forming apparatus according to the present invention includes halftone signal generation means for generating a plurality of different halftone signals for each developed color based on a predetermined image signal. , a pattern signal generating means for generating a halftone signal pattern for each developed color to be outputted to the digital scanning system, and a halftone signal generating means based on the halftone signal pattern generated by the pattern signal generating means. A selection means is provided for automatically selecting a halftone signal generated by the means and outputting it to a digital scanning system.

[Operation] In the present invention, when digital latent image formation corresponding to each developed color is started, a halftone signal is generated by the halftone signal generating means based on the halftone signal pattern generated by the pattern signal generating means. The selection means automatically selects the halftone signals and sequentially outputs them to the digital scanning system, thereby making it possible to form a digital latent image with a different pattern for each developing color.

[Embodiment] FIG. 1 is a sectional view illustrating the configuration of a multicolor image forming apparatus showing an embodiment of the present invention, and the same parts as in FIG. 7 are given the same reference numerals.

In the figure, 26 is a digital exposure system, and a laser scanning system 2
6a, scanning mirrors 26b, 26c, etc. In this embodiment, the laser scanning system 26a is composed of a semiconductor laser, a polygon mirror, etc. B is a processed signal (selected halftone signal), the details of which will be described later.

Reference numeral 25 denotes a laser scanning control section, the details of which will be explained with reference to FIG.

FIG. 2 is a control block diagram illustrating the configuration of the laser scanning control section 25 shown in FIG. The frequency is divided by control to produce a predetermined image signal corresponding to each developing material color, in this embodiment, image signal AO (for magenta (M) and for yellow (Y)) 9
The image signal BO (cyan (C)) is output to the shift register 31.

The shift register 31 functions as a halftone signal generation means in this embodiment, and selectively shifts the input image signal A○ or image signal BO to produce the delay amount ○~4 shown in FIG. 3(a). A total of five types of halftone signals AO to A4 (mainly for magenta (M) and yellow (Y)) are generated, and a halftone signal BO (same as the image signal BO) is generated. Note that the image signal AO and the halftone dot signal AO are the same signal.

36 is a zero pulse generator which manually supplies a zero pulse n (mainly for cyan (C)) to the selector 34.

Reference numeral 33 denotes a halftone pattern signal generator (pattern signal generating means in this embodiment), which outputs count values K ((for magenta (M) and for yellow (Y)) generated from the counter 35.
1 to 5) when generating.

When generating cyan (C), CPU3 according to 1 to 2)))
The halftone pattern set in the RAM of No. 2 (Fig. 3 (c)
)? One of the halftone patterns aO to a4 or the halftone pattern bOn is output to the selector 34 based on the halftone pattern bOn. In this embodiment, five types of halftone signals A0 to A4 are prepared for resolution 40.
This is to make it compatible with 0DP■. In addition, counter 35
is counted up based on a horizontal synchronization signal input from a horizontal synchronization signal generator (not shown).

The selector 34 functions as a selection means in this embodiment, and selects one of the outputs of the shift register 31 based on an arbitrary halftone pattern output from the halftone pattern signal generator 33 for each developed color. Select your own l1Ll1,
It is output to the amplifier 37 as a pulse signal C. amplifier 37
The 1i pulse signal C is converted into a pulse signal B for driving a semiconductor laser, and is input to the laser scanning system 26a shown in FIG.

Hereinafter, with reference to FIG. 4, a digital/analog exposure process related to the multicolor image forming apparatus according to the present invention will be explained.

FIG. 4 is a schematic diagram showing the results of digital/analyzer exposure processing in the multicolor image forming apparatus according to the present invention; FIG.
) indicates the image forming pattern of the second color cyan (C),
FIG. 2C shows an image forming pattern of the third color, 1' yellow (Y). Note that the screen angle (26,6°) in the image forming pattern for the first color, magenta (M), and the screen angle (-26,6°) in the image forming pattern for the final color, yellow (Y), are respectively used for the second color. Cyan (C)
is different from the screen angle (0,0'').

First, when the halftone exposure process for the first color (in this embodiment, the developed color is magenta) is started, the CPtJ32 divides the high speed clock so that the pulse pattern generator 30 generates the image signal AO. When the pulse pattern generator 30 is controlled and the image signal AO generated in the shift register 31 is manually inputted, the image signal AO shown in FIG.
) is set in the halftone pattern signal generator 33. At this time, the counter 35 is set to "1".

Next, the shift register 31 shifts the image signal AO in synchronization with the high-speed clock, and processes the image signal AO as shown in FIG. 3(a).
- Generate halftone signals AO~△4. At this time, the selector 34 automatically selects the halftone signal Δ0 based on the halftone pattern aO set in the halftone pattern signal generator 33, and sends the processed signal B to the laser scan shown in FIG. System 2
6a.

In the laser scanning system 26a, a semiconductor laser is modulated and driven based on the input processing signal B, and an analog latent image formed on the photoreceptor 5 is one-dimensionally formed through a polygon mirror, an fθ lens, a collimator lens, etc. (not shown). Digital exposure is performed to form a digital latent image for one line.

Next, when the counter 35 is sequentially incremented by "1", the selector 34 is sequentially set to the halftone pattern a2. Halftone pattern a4° halftone pattern al,
The halftone pattern a3 produces the halftone signal A2. Halftone signal A4. The halftone signal A1 and the halftone signal A3 are automatically selected, and the processed signal B is input to the laser scanning system 26a shown in FIG. 1 in the same manner as described above. This process is performed using a count value K (1 to 5)
By sequentially repeating this, a digital/analog latent image corresponding to the halftone dot pattern and analog image shown in FIG. 4(a) is formed on the photoreceptor 5, and this digital/analog latent image is developed with magenta toner.

Next, when the second color halftone exposure process is started, the CPU
32 is a pulse pattern generator 3 which divides the high speed clock.
The pulse pattern generator 30 is controlled so that the image signal BO is generated from 0, and when the generated image signal BO is input to the shift register 31, the CPU 32 is set to generate the image signal BO as shown in FIG. 3 (1). The halftone dot pattern bo is set in the halftone dot bang signal generator 33. At this time, the counter 35 is set to "1".

Next, the shift register 31 passes the image signal BO in synchronization with the high-speed clock, and creates the network shown in FIG. 3(b).
1] Generates a 0 signal. At this time, the selector 34 automatically selects the halftone signal bo and the zero pulse alternately based on the halftone patterns bo and n set in the halftone pattern signal generator 33, and converts the processed signal B into the first The laser scanning system 26a shown in the figure is manually operated.

When this process is repeated for count values K(1, 2) in sequence, a digital/analog latent image corresponding to the halftone dot pattern and analog image shown in FIG. 4(b) is formed on the photoreceptor 5, and this digital/analog latent image The image is developed with cyan toner.

Furthermore, when the halftone exposure process for the third color (in this embodiment, the developing color is yellow) is started, the CPU 32 divides the high speed clock so that the pulse pattern generator 30J generates the image signal AO. When the pulse pattern generator 30 is controlled and the generated image signal Δ0 is input to the shift register 31, the CPU 32 is set to
) is set in the halftone pattern signal generator 33. At this time, the counter 35 is set to "1".

Next, the shift register 31 shifts the image signal AO in synchronization with the high-speed clock, and generates the halftone signal AO-A4 shown in FIG. 3(a). At this time, selector 3
4 is a laser scanning system 26 that automatically selects the halftone signal AO based on the halftone pattern a○ set in the halftone pattern signal generator 33 and outputs the processed signal B as shown in FIG.
Enter a.

The laser scanning system 26a modulates and drives a semiconductor laser based on the input processing signal, and scans the photoreceptor 5 via a polygon mirror, an fθ lens, a collimator lens, etc. (not shown).
The analog latent image formed is one-dimensionally exposed digitally to form a digital latent image for one line. Next, when the counter 35 is sequentially incremented by "1", the selector 34 is sequentially set to the halftone pattern a3.11.
21 dot pattern al, halftone pattern a4. The halftone pattern a2 produces a halftone signal A3. Halftone signal Al, halftone signal A4. The halftone signal A2 is automatically selected, and the processed signal B is input to the laser scanning system 26a shown in FIG. 1 in the same manner as described above. When this process is repeated sequentially for each count value K (1 to 5), a digital/analog latent image corresponding to the halftone pattern and analog image shown in FIG. 4(C) is formed on the photoreceptor 5, and this digital/analog latent image is developed with yellow toner.

The digital/analog latent image formed in the manner described in 1 becomes a visible image for each color and is formed as a multicolor image on the fed recording medium. This makes it possible to form an optimal digital/analog image without color shift or color unevenness.

Although the above embodiment has been described using a three-color full-color multicolor image forming apparatus as an example, it goes without saying that the present invention can be applied to any device capable of outputting a multicolor image of two or more colors. For example, FIG. 5(a).

As shown in (b), magenta (M) + cyan (C),
Even with combinations such as cyan (C) + yellow (Y) or yellow (Y) + magenta (M), dispersion exposure can be performed with different patterns for each developed color, and as above, optimal digital analog images without color shift and color unevenness can be achieved. Formable roar.

Further, in the above embodiment, a case has been described in which halftone exposure is performed after exposing the original, but the exposure order of the two different scanning exposure systems may be reversed to the above or may be performed simultaneously.

Furthermore, in the above embodiment, the CPU 32 automatically selects each halftone signal, not shown in FIG. As described above, the pattern is not limited to the above embodiment, and the patterns shown in FIGS. 6(a) to 6(C) may be used, and may be set as appropriate.

[Effect of the Invention 1] As explained above, the present invention provides a halftone signal generation means for generating a plurality of different halftone signals for each developed color based on a predetermined image signal, and a digital scanning system. a pattern signal generating means that generates a halftone signal pattern to be outputted for each developed color; and a halftone signal generating means that generates a halftone signal pattern based on the halftone signal pattern generated by the pattern signal generating means. Since we are equipped with a selection means that automatically selects the dot signal and outputs it to the digital scanning system, even if registration deviation for each color or vibration of the mechanical mechanism occurs, the digital dot signal by the dot signal for each color component can be It is possible to perform fractional exposure at each exposure position optimally to form an optimal multicolor digital/analog image free from color shift and color unevenness.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating the configuration of a multicolor image forming apparatus showing an embodiment of the present invention, and FIG. 2 is a control block diagram illustrating the configuration of the laser scanning control section shown in FIG. 1. 3 is a diagram illustrating the operation of FIG. 2, FIG. 4 is a schematic diagram showing the result of digital/analyzer exposure processing in the multicolor image forming apparatus according to the present invention, and FIGS. A schematic diagram showing a digital image based on another halftone signal pattern related to a color image forming apparatus, FIG. 7 is a sectional view showing the configuration of this type of multicolor image forming apparatus, and FIG. FIG. 9 is a cross-sectional view of main parts of the multicolor image forming apparatus, and is a schematic diagram showing an example of multicolor image output. In the figure, 25 is a laser scanning control section, and 26 is a digital exposure system. Figure (a) b)

Claims (1)

[Claims] An analog scanning system that scans and exposes a document to form an analog image on a photoconductor, and a digital scanning system that scans a photoconductor with an optical signal modulated based on a predetermined image signal to form a digital image, In a multicolor image forming apparatus that develops an image formed on a photoreceptor with a plurality of developing materials to obtain a multicolor image, a plurality of different types of halftone dot signals are generated for each developed color based on the predetermined image signal. a halftone signal generating means for generating a halftone signal pattern for each developing color; A multicolor image forming apparatus comprising: a selection means for automatically selecting a halftone signal generated by the halftone signal generation means based on a signal pattern and outputting the selected halftone signal to the digital scanning system.