JP2002214716A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of excellently reproducing all the colors of Y, M, C and K without making the color tone of black between dots and solid different by a simple image forming means. SOLUTION: In this image forming apparatus forming a dot picture corresponding to digital dot picture data by exposing photosensitive material with light, the photosensitive material having color developing layers corresponding to respective images Y, M and C is exposed with different wavelength light by every color developing layer, the respective images Y, M and C are expressed by the respective color developing layers, and an image K is expressed by superimposing the developed colors of Y, M and C so as to form a picture. Exposure to the color developing layers Y, M and C forming the image K is set according to the dot % of the image K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus for producing a dot proof for printing. Here, the proof is an image for checking. For example, the color, character, and position of the image are checked. Then, referring to the halftone proof, it is checked whether or not the image is intended by the user.

[0002]

2. Description of the Related Art In recent years, with the spread of Desk Top Publishing and the like, the work of image editing and page imposition of images input from a scanner on computer software has become common, and full digital editing has become commonplace. .

In such a process, in order to further increase the efficiency, an image setter output for directly outputting image-edited image data to a film, a CTP (Computer to Plate) output for directly recording an image on a printing plate, and Is a computer to cylinder (CTC) for directly recording an image on a printing plate wound on a cylinder of a printing press.

In this case, once a film output or a printing plate output is performed only for the purpose of checking the proof, and printing proofing and proofreading with other proof materials are performed, waste of the film and the printing plate and unnecessary work are increased. There's a problem.

[0005] Therefore, particularly in the process of creating and editing a full digital image by such a computer,
A system called DDCP (Direct Digital Color Proof) for directly outputting a color image is demanded.

[0006] Such a DDCP is used to record digital image data processed on a computer on a plate making film using an imagesetter or the like, perform a final printing operation of directly creating a printing plate by CTP, or perform CTC. Before performing image recording directly on the printing plate wound on the cylinder of the printing press, etc., create a color proof that reproduces the output target indicated by the digital image processed on the computer, and This is for checking text characters and the like.

Therefore, as an apparatus for producing such a color proof, there is provided a drum and a rotation drive mechanism for rotating the drum, and the rotation drive mechanism holds the photosensitive material on the drum while holding the photosensitive material. There has been proposed an image forming apparatus which rotates the drum, performs light exposure according to a digital image signal, and records a halftone image. In this type of device, the light-on amount is set in the saturation region of the characteristic curve of the photosensitive material. As a result, an image (halftone dot) due to light quantity fluctuation
The impact on is reduced. In this case, the image is represented by a binary value of color development ("1") or no color development ("0").

In a conventional device of this type, Y (yellow), M (magenta), C (cyan),
A color image is formed using K (black: black). Among these colors, K can be formed by a combination of Y, M, and C. Therefore, K is represented by superposition of Y, M, and C in order to reduce the cost of the apparatus and simplify the mechanism.

FIG. 6 is an explanatory diagram of the K-version expression. As is clear from the figure, the K version is created by superimposing Y, M and C. When the K plane is realized in this manner, for example, when the dot gain of Y (the difference between the set dot% and the image dot%) is large, as shown in FIG. As shown by hatching, Y becomes blurred. FIG. 8 is an explanatory diagram of the dot gain. The vertical axis is the image halftone percentage, and the horizontal axis is the setting halftone percentage. H is a straight line when the image dot% and the set dot% are equal. The difference ΔG between the straight line H and the actual curve is the dot gain.

As described above, the conventional apparatus has the following problems. The Y, M, and C colors are formed on the three photosensitive layers of the photosensitive material, and correspond to the Y, M, and C versions of the printing, respectively.
When represented by the superposition of M and C, the characteristic curve of the photosensitive material is 3
If the layers vary or the exposure beam qualities corresponding to the three layers vary, the color tone of the solid image differs from that of the halftone dot image on the K plane. Although the color is solid black, the edge of the net has bleeding and the like, and the colors are slightly different between Y, M and C, and the color changes. For this reason, accurate color reproduction of the printed matter cannot be performed, and there is a problem as a proof.

[0010] In order to solve such a problem,
The four plates of Y, M, C, and K may be independently performed for the photosensitive material (four layers) and the exposure (four light sources), but the apparatus becomes complicated and the cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and it is possible to satisfactorily control all colors of Y, M, C, and K by a simple image forming means without changing the black net or solid color tone. It is characterized by providing an image forming apparatus capable of reproducing.

[0012]

According to a first aspect of the present invention, there is provided an image forming apparatus for forming a halftone image corresponding to digital halftone image data by exposing a photosensitive material to light. In the apparatus, a light-sensitive material having a color-forming layer corresponding to each of the Y, M, and C plates is exposed at a different wavelength for each color-forming layer, and the Y, M, and C plates are expressed by each color-forming layer. An image forming apparatus which expresses a K plate by forming a color image and forms an image, wherein the amount of exposure to the Y, M, and C color forming layers forming the K plate is set in accordance with the dot% of the K plate. And

With this configuration, even if the photosensitive material and the exposure beam corresponding to each of the Y, M, and C plates have variations,
All colors of Y, M, C, and K can be satisfactorily reproduced without any difference in black net and solid color tone.

(2) The invention according to claim 2 is characterized in that the setting of the exposure amount of the K plate is different from that of 100% in halftone. With this configuration, it is possible to simplify the setting of the amount of light while securing the effect of color reproduction.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below. In the following description, the meanings of the terms are explained. However, the meanings of the terms in the embodiments are only described, and the meanings of the terms of the present invention are not limited to this description.

(Overall Configuration and Operation of Apparatus) First, the overall configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described.

The image forming apparatus according to the present embodiment is an apparatus that obtains a color proof from a digital image signal in order to obtain a proof that confirms the finish of a printed matter in advance. Specifically, in creating a color print, before creating a printing plate from a digital image signal, create a color proof that simulates an image obtained by printing on a printing plate created from this digital image signal, This is a device for creating a color proof in order to inspect the image indicated by the digital image signal for errors such as errors in layout, colors, characters, etc., and to confirm the finish of the printed matter in advance.

Further, in the image forming apparatus of this embodiment, a roll-shaped silver halide color photographic material is set as a photosensitive material, cut into a sheet at an exposure section, and responded to the aforementioned digital image signal. Then, it is exposed to a light beam, and then developed in a developing section to create a color proof.

FIG. 1 is a schematic diagram showing the internal configuration of the image forming apparatus. The image forming apparatus includes an exposure unit 3 for exposing an image on a photosensitive material, and a development processing unit 4 for developing the exposed photosensitive material.

The interior of the exposure section 3 has the following configuration. The roll set section 10 is a section for loading a magazine 18 containing rolls of the photosensitive material P in a roll form, and is provided at an upper portion of the apparatus main body. The loading of the magazine 18 is performed by opening and closing the paper feed cover 19. The roll setting section 10 of the present embodiment is a section for loading a magazine 18 containing a roll of photosensitive material P, but may be a section that can directly set a roll of photosensitive material.

The magazine 18 set in the roll set section 10 is a magazine containing rolls wound with the photosensitive surface of the photosensitive material P facing outward. When the roll setting section 10 can directly set a roll of photosensitive material, it is preferable to set a roll wound with the photosensitive surface of the photosensitive material P facing outward.

A roller pair 21 and a cutter 22 for cutting the photosensitive material into a predetermined length are provided vertically below the roll set section 10 of the magazine for storing the photosensitive material P. Further, when the magazine is loaded, the roller pair 21
It is arranged at a position close to the outlet of the loaded magazine 18.

The squeeze roller 23 is provided vertically below the roller pair 21 and can be brought into contact with and separated from a drum 30 provided in the main scanning section. The conveying path of the photosensitive material from the outlet of the magazine 18 to the squeeze roller 23 extends substantially vertically downward. When the photosensitive material P is supplied to the drum 30, the squeeze roller 23 is pressed against the drum 30 and applies the supplied photosensitive material P to the drum 3.
0 to the outer peripheral surface. Meanwhile, the squeeze roller 23 stops when the photosensitive material P is fed by a predetermined length, and the photosensitive material P is cut into a sheet of a predetermined length by the cutter 22. Thereafter, the squeeze roller 23 is driven to rotate to bring the photosensitive material P into close contact with the outer peripheral surface of the drum 30.

The peripheral speed of the drum 30 at the time of paper feeding is 2 m
/ Sec or less (especially 1 m / sec or less). As a result, the toner can be stably fed to the drum 30, the adhesion to the drum 30 is increased, and the retention by suction is improved. Also,
The peripheral speed of the drum 30 during paper feeding is 2 cm / sec or more (especially
cm / sec or more). Thereby, the feeding time can be reduced, and the image recording time and the image recording time interval can be reduced. In the device of the present embodiment, the speed is 0.1 m / sec.

The surface substrate of the squeeze roller 23 is made of rubber in the apparatus of the present embodiment, but is not limited thereto, and may be an elastic material from the viewpoint of the adhesion of the photosensitive material P to the drum 30. preferable. Thereby, the photosensitive material P sufficiently adheres to the drum by the elastic deformation of the surface substrate of the squeeze roller 23.

The drum 30 is rotatable by a squeeze roller 23. When the photosensitive material P is fed, the photosensitive material P is fixed on the outer peripheral surface by air suction while being rotated by the squeeze roller 23. When the fixing of the photosensitive material P on the outer peripheral surface of the drum 30 is completed, the squeeze roller 23 is separated from the drum 30. When the squeeze roller 23 separates from the drum 30, the rotation driving mechanism of the drum 30 rotates the drum 30 at a higher rotation speed than the rotation speed during the close contact operation, so that the photosensitive material P is main-scanned during recording. It rotates at a high speed while fixing the photosensitive material P on the outer peripheral surface.

The peripheral speed of the drum 30 during image recording is
It is preferably at least 3 m / sec (particularly at least 5 m / sec, more preferably at least 10 m / sec). Thereby, the image recording time can be shortened. The peripheral speed of the drum 30 during image recording is preferably 70 m / sec or less (particularly 50 m / sec or less). Thereby, the peripheral speed of the drum 30 is stabilized,
The time required to stabilize the peripheral speed is shortened, and the cost of the device is reduced, and the device becomes safe. In the apparatus of the present embodiment, the peripheral speed of the drum 30 during image recording is about 30 (m / sec).

The optical unit 400 is disposed so as to face the drum 30, and is driven by the sub-scanning mechanism 300.
It moves parallel to the 0 axis of rotation. Also, the optical unit 40
0 writes an image on the photosensitive material P on the drum 30 by an LED chip in response to a digital signal.

The rotation direction of the drum 30 having the photosensitive material P fixed on the outer peripheral surface is set as the main scanning, and the rotation axis direction of the drum 30 is set as the sub-scanning. Is recorded on the photosensitive material P.

The paper discharge section 50 has a peeling guide 51 that can be brought into contact with and separated from the drum 30. The peeling guide 51 is usually
When the drum 30 is stopped after being separated from the drum 30 and the image writing is completed, the peeling guide 51 comes into contact with the drum 30, and the squeeze roller 23 is pressed against the drum 30.
The squeeze roller 23 is driven to rotate to rotate the drum 30, and the peeling guide 51 peels the photosensitive material P from the drum 30.

The peripheral speed of the drum 30 when peeling the photosensitive material from the drum 30 is preferably 2 m / sec or less from the viewpoint of stable peeling and prevention of breakage of the tip of the photosensitive material. 0.01m /
It is preferably at least seconds. In the device of the present embodiment,
The peripheral speed of the drum 30 when peeling the photosensitive material from the drum 30 is about 0.05 to 0.1 m / sec.

When the peeling of the photosensitive material P is completed, the peeling guide 51 is separated from the drum 30. Then, the paper discharge unit 50
Sends the peeled photosensitive material P to the development processing unit 4. Also,
The development processing unit 4 includes a color development processing unit 42, a bleach-fix processing unit 43, a stabilization processing unit 44, a drying unit 45, and a discharge tray 4
6 is provided. Then, the photosensitive material P is developed and discharged.

Next, the drum 30 and the optical unit 40
2 is a plan view showing the periphery of the drum 3
0 and the periphery of the optical unit 400 will be described. FIG. 2 is a diagram showing the periphery of the drum and the optical unit of the apparatus of the present invention. The drum 30 has shaft portions 31 at both ends of its rotating shaft.
32 are provided, and shaft portions 31, 32 of the drum 30 are provided.
Is rotatably supported on a support base 34 via a bearing. The rotation drive mechanism for rotating the drum 30 about the rotation axis is a drive pulley 35 provided on one shaft portion 32 of the drum 30, and an output pulley which is dynamically connected to the drive pulley 35 via a belt 36. 38 and an output pulley 38
And a belt 36. The drum rotation motor M6 rotates the output pulley 38, and transmits a driving force to the driving pulley 35 via the belt 36 to rotationally drive the drum 30. I have.

A rotary encoder 37 is provided on one shaft of the drum 30 and further outside the position where the drive pulley 35 is provided, and a pulse signal output from the rotary encoder 37 is used for writing control. Used. The other shaft 31 of the drum 30 is connected to a suction blower 39.

Since the drum 30 is a hollow body made of aluminum and has a number of suction holes penetrating from the outer peripheral surface of the drum 30 to the inside, the inside of the drum 30 is depressurized by the operation of the suction blower 39. Thus, the photosensitive material P can be fixed on the surface of the drum 30 by air suction.

The diameter of the drum 30 is set to a value of 10 from the viewpoint of the usefulness of the color proof to be produced, curl, exposure accuracy, and the like.
cm or more, and an LED chip or
In order to obtain a good image easily and at high speed in an optically conjugate relationship between the LED light source (unit) having the LED chip and the photosensitive material, the distance is preferably 15 cm or more (particularly 20 cm or more). Equipment cost, equipment size,
The thickness is preferably 1 m or less (particularly 50 cm or less, more preferably 40 cm or less) from the viewpoints of manufacturability for obtaining the required exposure accuracy and a small adverse effect of thermal expansion. In addition, in the apparatus of this embodiment, it is 29 cm.

The width of the drum 30 (the length of the outer peripheral surface of the drum 30 in the rotation axis direction) is preferably 30 cm or more (particularly 50 cm or more) from the viewpoint of the usefulness of the color proof to be produced. Equipment cost, equipment size,
From the viewpoint of manufacturability to obtain the required exposure accuracy, 1.
It is preferably 5 m or less (especially 1 m or less). As a result, there is no need for special mechanical strength, so that the cost is reduced,
Further, since the machine weight is not large and the installation place is not particularly limited, it can be installed at a highly convenient position. In addition, in the apparatus of this embodiment, it is about 60 cm.

The sheet width of the photosensitive material P to be exposed (the length of the photosensitive material P in the direction of the rotation axis of the drum 30) depends on the cost of the apparatus, the size of the apparatus, and the manufacturability for obtaining the required exposure accuracy. To 1.5 m or less, so that the size in the drum axis direction can be small, and the weight for obtaining the structural accuracy and strength required for the drum itself, the drum mounting portion, and the optical scanning portion can be reduced. , It is possible to eliminate the need to select an installation location. In addition, it is preferably at least 25 cm (especially 50 cm or more) from the viewpoint of the usefulness of the produced color proof.

The length of the sheet of the photosensitive material P to be exposed (the length of the photosensitive material P in the rotating direction of the drum 30) is determined from the viewpoints of the apparatus cost, the apparatus size, and the manufacturability for obtaining the required exposure accuracy. To a maximum of 2 m or less (especially 1.5 m or less), so that the size in the radial direction of the drum can be small, and the influence of thermal expansion of the drum is small.
Processing accuracy can be easily obtained, the weight required for obtaining the required structural accuracy and strength can be reduced, and the installation location can be selected. In addition, it is preferably at least 25 cm or more from the viewpoint of the usefulness of the produced color proof.

The sheet size of the photosensitive material P to be exposed is preferably 0.06 square m or more (particularly 0.12 square m or more) from the viewpoint of the usefulness of the produced color proof. Further, the size is preferably 3 m 2 or less (especially 2 m 2 or less), whereby the size of the device can be reduced and the weight for obtaining the required structural strength can be reduced to any location.

In the apparatus of this embodiment, the width and length of the photosensitive material P to be exposed are 57 cm × 3.
It corresponds to the size of 5cm, 57cm x 70cm, 57cm x 85cm, and in the case of the size of 57cm x 35cm,
When the effective image area is 55.5 cm x 33.7 cm, an A3 size image can be reproduced. In the case of 57 cm x 70 cm, the effective image area is 55.5 cm x 67.4 cm, and an A2 size image can be reproduced. 57 cm x 85 cm Size, the effective image area is 55.5 cm × 82.8 cm and B2
Can reproduce the image of the size.

Next, the sub-scanning mechanism 300 for moving the optical unit 400 to perform sub-scanning will be described with reference to FIG. The optical unit 400 is fixed to the metal belt 340, and is guided by a pair of guide rails 341 and 342 provided in parallel with the rotation axis of the drum 30 and can move in parallel with the rotation axis of the drum 30. The metal belt 340 is wound around a pair of pulleys 343 and 344,
Reference numeral 4 is directly connected to a rotation shaft 345 of the drive motor M7.
When the drive motor M7 rotates the rotating shaft 345, the pulley 344 fixed to the rotating shaft 345 rotates,
The metal belt 340 wound around the pulley 3 and the pulley 344 rotates. Then, the rotation of the metal belt 340 causes the optical unit 400 to move parallel to the rotation axis of the drum 30.

The drive motor M7 is connected to the optical unit 4
When the optical unit 400 is moved backward, the rotation speed is faster than that during the forward movement, and the optical unit 400 is returned at a faster moving speed than when the forward movement. In order to make it rotate, it is driven at high speed.

The optical unit 400 stops at the sub-scanning reference position, starts sub-scanning from this position, and returns to the sub-scanning reference position when the sub-scanning is completed with a movement amount corresponding to the image size.

As shown in FIG. 2, a rotary encoder 37 for detecting the rotational position of the drum 30 is mounted coaxially with the rotation shaft 90 of the drum 30. The rotary encoder 37 outputs a pulse signal, and outputs a tip position signal of the photosensitive material P from a tip position sensor S9 that detects the tip position of the photosensitive material P. Based on these signals,
The writing control and the rotation control of the drum rotation motor M6 are performed. The drum rotation motor M6 rotates the drum 30 at high speed using a servomotor.

The image recording density of the image recorded on the photosensitive material P is 600 dpi or more (especially 1000 dpi or more, further 1200 dpi or more) in both the main scanning direction and the sub-scanning direction from the viewpoint of the reproducibility of gradation by a halftone image. )
In addition, from the viewpoint of saturation of reproducibility of gradation by a halftone dot image, image recording speed, and apparatus cost, it is 10,000 dpi or less in both the main scanning direction and the sub-scanning direction (particularly, 500 dpi).
0 dpi or less). The image recording density of the image recorded on the photosensitive material in the apparatus of this embodiment is 2000 dpi in both the main scanning direction and the sub-scanning direction.

One halftone dot is 100 or more (especially 2 dots).
(00 or more) is preferable because the reproduction is close to halftone dots of actual printing. Further, it is preferable that one halftone dot is recorded from 5000 or less (especially, 2000 or less) pixels because the handling of image data is easy and the image data can be processed at high speed.

In FIG. 1, a RIP 200 provided outside the apparatus 1 and connected to the apparatus 1 converts Y, M, and C digital images in raster image format from image data for electronic plate making which is the basis of electronic plate making. The halftone image data is generated in order (surface-sequential) for each color. Then, it is preferable to reproduce from the image data for electronic plate making by a set of halftone dots having the same screen ruling as the printed matter, and to reproduce the pixel gain amount by approximating that of the printed matter. This allows
In addition to being able to faithfully reproduce a printed halftone dot image, there is a merit that a tone jump, a moiré, and a defect of an image, which are common problems in electronic plate making image data, can be accurately reproduced and calibrated. Of course, the rough calibration does not require faithful reproduction up to that point, and rough calibration is possible with a halftone image.

Then, the RIP 200 sends the generated digital halftone dot image data to the image data I / F (interface) unit 500 in order (surface-sequential) for each color. The image data I / F unit 500 converts the raster image format raster image data of each color (Y, M, C) created by the RIP 200 into an exposure format for each of the number of scanning lines simultaneously recorded in one main scan. And the image data I /
It is stored in an external storage device (not shown) attached to the F section 500. Then, the digital halftone image data converted into the exposure format for each scanning line (for one main scan) is stored in an external storage device attached to the image data I / F section 500 for one color of Y, M, and C. Image data I / F
The unit 500 reads out pixel data including all data of Y, M, and C in an exposure format for each scanning line, and transmits data of all colors to the image recording control unit 100 simultaneously (dot-sequentially).

The image recording control unit 100 transmits the transmitted Y,
Control is performed so that an image is exposed on the photosensitive material P based on image data obtained by converting pixel data including all data of M and C into an exposure format for each scanning line.

FIG. 3 is a schematic diagram showing an example of the optical configuration of the optical unit 400 of the image forming apparatus according to the present invention. The optical unit 400 includes a red LED unit 4
20, a green LED unit 421 and a blue LED unit 422 are arranged.

Part of the light from the red LED unit 420 is reflected by the mirror 425, passes through the dichroic mirrors 426, 427, and enters the imaging optical system 431. Also, some light from the green LED unit 421 is
The light is reflected by the dichroic mirror 426, passes through the dichroic mirror 427, and enters the imaging optical system 431. Further, a part of the light from the blue LED unit 422 is reflected by the dichroic mirror 427 to form the image forming optical system 431.
to go into. The imaging optical system 431 includes the red LED unit 420, the green LED unit 421, and the blue L
An image is exposed on the photosensitive material P by an imaging optical system in which the lens of the ED unit 422 and the photosensitive material on the drum 30 are conjugate.

The image forming optical system 431 in FIG.
The front lens, which is the light emitting portion of each of the LED units 420 to 422, and the photosensitive surface of the photosensitive material P are configured to be substantially optically conjugate. In addition, while having such a conjugate relationship, at the position of the photosensitive material P, the LED
It also serves as a reduction optical system in which light from the units 420 to 422 is reduced and projected.

Next, the electrical configuration of the exposure unit 3 of the image forming apparatus will be described with reference to FIG. FIG. 4 is a circuit diagram showing an embodiment of the present invention. 1 to 3 are denoted by the same reference numerals. As shown in FIG. 4, the image recording control unit 100 includes a CPU 101 for controlling each unit,
RAM 102 storing various tables, image data I
The data processing unit LUT 103, the LED units 420 and 421, which sequentially convert the exposure format transmitted from the / F unit 500 and supply them to the drivers D420 to D422.
Drivers D420 to D422 for driving 422 are arranged.

The sensors connected to the CPU 101 include a rotary encoder 37 for detecting the rotational position of the drum 30, a tip position sensor S9 for detecting the tip position of the photosensitive material P, and the LED units 420 and 42.
1,422 temperature sensors 490 and the like. The actuator group includes a drum rotation motor M6, a sub-scanning drive motor M7, and LED units 420 and 42.
1,422 fans 2300 and the like are driven under the control of the CPU 101.

A density sensor 480 is provided to detect the density obtained on the photosensitive material P by exposure from the LED chip of each LED unit. And
A predetermined test patch is recorded and developed, and the photosensitive material P discharged to the paper discharge tray 46 by the operator is supplied to the density sensor 4.
By setting to 80, the density characteristic value of the photosensitive material can be obtained.

In the present invention, when an image is exposed on the photosensitive material P, the photosensitive material P having a color forming layer corresponding to each of the Y, M, and C plates is exposed at a different wavelength for each color forming layer. ,
It is assumed that each of the M and C plates is expressed, and the K plate is formed by superimposing Y, M and C. As described above, in the case of forming an image, the amount of exposure to the Y, M, and C
This is set according to the halftone% of the plate.

FIG. 5 is a block diagram showing an embodiment of the present invention. 1 to 4 are denoted by the same reference numerals. In the figure, reference numeral 200 denotes a halftone decomposing unit which receives image data and outputs Y, M, C, K plane data and K halftone% data, and the RIP in FIG. 4 corresponds to this. 103 is Y, M,
This is an exposure amount setting unit that receives the C and K plane data and the K halftone% data and sets the exposure amount, and the LUT in FIG. 4 corresponds to this. In FIG. 5, the image data I / F section 500 existing between the RIP 200 and the LUT 103 is omitted. 600
Is the amount of Y-colored light output from the exposure setting unit 103,
Exposure light source for exposing the photosensitive material P by receiving the amount of coloring light and the amount of coloring C, R, G, BLEDs 420 to 422 in FIG.
Corresponds to this. The operation of the circuit thus configured will be described as follows.

The image data enters the net decomposition unit 200. The network decomposing unit 200 analyzes the image data and calculates Y, M, C, K
Get version data. In addition, K halftone dot% data obtained during the analysis of the image data is obtained. Then, the halftone decomposing unit 200 outputs the Y, M, C, K version data and the K version halftone% data. The exposure amount setting unit 103 sets these Y, M, C, K
Exposure amount corresponding to plate data, and K plate dot% for K plate
In response to the data, the exposure amount to the Y, M, and C color forming layers forming the K plane is set according to the halftone data of the K plane.

More specifically, the exposure amount to the color forming layer is adjusted for each of Y, M, and C according to the halftone% data of the K plane. For example, as shown in FIG. 7, the dot gain of Y is high, and Y + M + C
In the case of yellow image, if Y, M and C are colored so that the solid color of K becomes the target color, the dot gain of Y is high and the yellow color is blurred in the halftone image , And Y (in the case of negative paper.
In the case of positive paper, increase the exposure). In this way, the amount of coloring light for each of Y, M, and C is adjusted, and the exposure light source 60 is adjusted.
Give to 0. In the case of FIG. 7, the exposure amount of Y is set smaller than the standard state (in the case of negative paper; in the case of positive paper, it is set large). As a result, the obtained image is an image having good reproducibility without color blur as shown in FIG.

As described above, according to the present invention, Y, M, C
Even if the photosensitive material P and the exposure beam corresponding to each plate have variations, the net of K and the solid color tone do not differ, and Y,
All colors of M, C and K are reproduced well.

In this case, if the setting of the exposure amount of the K plane is made different from the halftone dot 100%, the light amount setting can be made simple while securing the effect of color reproduction.

In the above-described embodiment, the case where K halftone dot% data is created by the halftone decomposing unit 200 is taken as an example. However, the present invention is not limited to this, and is created by the exposure setting unit 103. You can also do so.

[0064]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first aspect of the invention, even if the photosensitive material and the exposure beam corresponding to each of the Y, M, and C plates have variations,
All colors of Y, M, C, and K can be satisfactorily reproduced without any difference in black net and solid color tone.

(2) According to the second aspect of the invention, it is possible to simplify the setting of the amount of light while securing the effect of color reproduction. As described above, according to the present invention, there is provided an image forming apparatus capable of favorably reproducing all the colors of Y, M, C, and K by a simple image forming means without different black net and solid color tone. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the internal configuration of a device of the present invention.

FIG. 2 is a diagram showing the periphery of a drum and an optical unit of the apparatus of the present invention.

FIG. 3 is a diagram showing an embodiment of an optical system.

FIG. 4 is a circuit diagram showing an embodiment of the present invention.

FIG. 5 is a block diagram showing an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a K-version expression.

FIG. 7 is an explanatory diagram of a problem of the conventional device.

FIG. 8 is an explanatory diagram of a dot gain.

[Explanation of symbols]

 103 Exposure Setting Unit (LUT) 200 Halftone Decomposition Unit (RIP) 600 Exposure Light Source

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hajime Nozawa 1 Sakuracho, Hino-shi, Tokyo Konica Corporation F-term (reference) 2H106 AA47 AA76 AA80 AA85 AB04

Claims (2)

[Claims] 1. An image forming apparatus for forming a halftone image corresponding to digital halftone image data by exposing a photosensitive material to light, comprising: a photosensitive material having a color forming layer corresponding to each of Y, M, and C plates; An image forming apparatus for exposing at a different wavelength for each color-forming layer, expressing each of the Y, M, and C plates in each color-forming layer, and expressing a K-plate by superimposing the Y, M, and C colors to form an image. An image forming apparatus, wherein the amount of exposure to the Y, M, and C color forming layers that form the K plate is set in accordance with the dot percentage of the K plate. 2. The image forming apparatus according to claim 1, wherein the setting of the exposure amount of the K plate is different from that of the halftone dot at 100%.