JP2000103120A - Color image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rewrite data in a time which does not differ from a time by a single beam rewriting method when θ data or gradation data in a memory provided by each laser light is rewritten by each color in terms of a multi-beam rewriting type color image forming apparatus. SOLUTION: In the case where γ data in two memories 1, 2 for image characteristic conversion provided by each LD 31, 32 is rewritten by each color, when the γ data in both of the memories 1, 2 is rewritten to the same data, both of the memories are accessed and when the γ data is rewritten to the different data by each memory, the memories 1, 2 are accessed, independently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a latent image of an image to be printed out by irradiating a photoreceptor with a laser beam, and develops the image through a series of image forming processes such as development, transfer and fixing. The present invention relates to a digital image forming apparatus such as a laser printer, a copying machine, and the like for printing and outputting, and in particular, a multi-beam writing system that forms a latent image by simultaneously irradiating a plurality of laser beams to a photoconductor surface using a plurality of laser light sources. The present invention relates to a color image forming apparatus that forms a latent image and forms a color image using a plurality of developing materials of different colors.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic digital image forming apparatus such as a digital copying machine or a laser printer,
A laser beam from a semiconductor laser is applied to a rotating polygonal mirror (optical deflector) called a polygon mirror, and the laser beam is sequentially deflected by a change in the reflection angle, so that the laser beam is scanned in the main scanning direction and is scanned in the sub-scanning direction. A latent image of an image to be output is formed by irradiating the surface of the photoconductor moving in a direction (a direction orthogonal to the main scanning direction). Since the laser beam is modulated in accordance with the image to be output, an electrostatic latent image corresponding to the image to be output is formed on the photoconductor, and this electrostatic latent image is developed into a toner image. In such a digital image forming apparatus, in order to output an image at a speed comparable to that of an analog high-speed machine, the rotation speed of a polygon mirror that deflects a laser beam and scans on a photoconductor is increased, It is necessary to increase the modulation speed and the like of the semiconductor laser to be modulated. However, there is a limit to the driving speed of the motor for rotating the polygon mirror and the modulation speed of the semiconductor laser, so that it has not always been possible to output an image at a desired processing speed. Therefore, there have been proposed various image forming apparatuses of a multi-beam writing system for writing (recording) a latent image by simultaneously irradiating a photoconductor with a plurality of laser beams by using a plurality of laser light sources (Japanese Patent Laid-Open No. 06-2006).
-331913, JP-A-07-181411, JP-A-07-181412, etc.). According to this method, the speed of writing a latent image on the photoconductor (the amount of information that can be recorded on the photoconductor per unit time) increases, so that the rotation speed of the polygon mirror and the frequency of the image signal can be reduced. Thus, the image forming process can be performed at high speed and stably. Therefore, in a color image forming apparatus, that is, an apparatus that sequentially performs latent image formation and development processing for each color and obtains a color image by superimposing a plurality of developed images, a multi-beam writing method should be used. Is particularly effective in stabilizing the image forming process at high speed.

However, in a color image forming apparatus, it is necessary to form an image by changing γ data and gradation data for each color. In the case of a single beam writing method, the gradation data for each color is converted. A method of switching between memories that are stored in advance in individual memories and read out γ data and gradation data for each color to be formed, and a method of retaining only one color and rewriting the data in the memory according to the output color However, in the case of the multi-beam writing method, it is necessary to have γ data and gradation data for each laser light source. , Resulting in a significant increase in cost and size of the device. In the case of a method in which the memory holds only one color and rewrites the data in the memory according to the output color, the memory access increases as the image formation processing speed (CPM) increases and the number of laser light sources increases. Higher speed is required.

[0004]

The problem to be solved by the present invention is that when the gamma data and the gradation data of the memory provided for each laser light source are rewritten for each color, the gradation data of all the memories are replaced with the same data. In the case of rewriting, all the memories are accessed simultaneously, and in the case of rewriting with different data for each memory, each memory is individually accessed, and the data is rewritten without much time difference from the case of the single beam writing method. It is an object of the present invention to provide a multi-beam writing type color image forming apparatus capable of performing the above operation.

[0005]

In order to solve the above problems, the invention according to claim 1 uses a plurality of laser light sources,
In a multi-beam writing type color image forming apparatus that simultaneously irradiates a photoconductor with a plurality of laser beams to write a latent image, a memory for image characteristic conversion is provided for each laser light source, and a memory for image characteristic conversion is provided. When the γ data in the memory is rewritten for each color, all the memories for image characteristic conversion can be accessed simultaneously or each memory can be individually accessed. According to the first aspect of the present invention, when the gamma data in the image characteristic conversion memory provided for each laser light source is rewritten for each color, the gamma data in all the image characteristic conversion memories are used. When rewriting to the same data, all the memories for image characteristic conversion are accessed simultaneously, and when rewriting to different data for each memory, each memory is individually accessed, Data can be rewritten without much time difference. However, as the speed of the color image forming apparatus increases and the time interval between the image forming process of the previous color and the image forming process of the next color becomes extremely short, the γ data and the gradation are changed during the transition from the previous process to the next process. It may be difficult to rewrite the key data. Therefore, according to a second aspect of the present invention, in the color image forming apparatus according to the first aspect,
Two lasers for image characteristic conversion are provided for each laser light source, and the memory to be used can be switched for each color. According to the second aspect of the present invention, two memories for image characteristic conversion provided for each laser light source can be alternately accessed, so that the next color can be obtained even during the transition from the previous process to the next process. Γ data and gradation data can be written to the memory, and the conventional memory access speed can be sufficiently used.

According to a third aspect of the present invention, in the color image forming apparatus according to the first or second aspect, a gradation data memory is provided for each color, and gradation data is read from each gradation data memory to convert image characteristics. It is characterized in that, when writing to the memory for writing, all the memories for converting image characteristics can be accessed simultaneously or each memory can be accessed individually. According to the third aspect of the invention, when the gradation data is read out from each gradation data memory and written into the image characteristic conversion memory, the gradation data in all the image characteristic conversion memories is rewritten to the same data. In this case, when all memories are accessed simultaneously and data is rewritten to different data for each memory, each memory is individually accessed, and data can be rewritten without much time difference from the case of the single beam writing method. According to a fourth aspect of the present invention, in the color image forming apparatus according to any one of the first to third aspects, after completion of the image formation, the color image frequently used for the first color in the next image formation. The tone data is written into a memory for converting image characteristics. According to the fourth aspect of the present invention, it is possible to further improve the processing speed in a case where image formation is continuously performed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a main part of a color image forming apparatus according to an embodiment of the present invention, in which two laser diodes (hereinafter, referred to as LDs) 31 and 32 are used as laser light sources. The configuration of a two-beam type laser writing control system for writing a latent image by simultaneously irradiating a photosensitive member (not shown) with two laser beams is shown. This laser writing control system includes each LD 31,
32, each of which has memory 1, 2 for image characteristic conversion, LD control circuits 11, 12, and LD modulation circuits 21, 22;
Image data (1) and (2) sent from an image processing system (not shown) are input to the memories 1 and 2, respectively.
After being converted into gradation data set in the memories 1 and 2, the data is input to the LD control circuits 11 and 12, respectively. Each of the LD control circuits 11 and 12 is an LD control signal (digital signal) corresponding to the inputted gradation data.
Is generated and input to each of the LD modulation circuits 21 and 22. Each L
The D modulation circuits 21 and 22 output an LD modulation signal (analog signal) corresponding to the input LD control signal, and
1. The laser oscillation operation of the LD 32 is controlled. The gradation data set in each of the memories 1 and 2 is rewritten by the gamma memory control circuit 40 and the process control unit 50 for each color.

At this time, the process control section 50 outputs gradation data of each color, an address signal, and a memory selection signal and inputs them to the gamma memory control circuit 40. The gamma memory control circuit 40 generates memory select signals S1 and S2 input to the memories 1 and 2 based on the input memory select signal. Here, when rewriting the grayscale data of both memories 1 and 2 to the same data, both memory select signals S
1 and S2 are both in the write state, and the same gradation data Da is simultaneously written to the specified address Ad output from the gamma memory control circuit 40 and common to both memories.
On the other hand, when rewriting the gray scale data of one of the memories 1 or 2, only the corresponding one of the memory select signals S1 or S2 is in the write state, and the specified address Ad of the one of the memories 1 or 2 is in the write state. The key data Da is written. According to the above embodiment, each LD3
When rewriting the gradation data of the image characteristic conversion memories 1 and 2 provided for each of the memories 1 and 32 for each color, when rewriting the gradation data of both memories 1 and 2 to the same data, the two memories 1 and 2 When accessing simultaneously and rewriting with different data for each of the memories 1 and 2, it is possible to individually access each of the memories 1 and 2 and rewrite data without much time difference as compared with the case of the single beam writing method. .

FIG. 2 is a block diagram of a main part of a color image forming apparatus showing an example of an embodiment of the present invention. The same components as those of the laser writing control system shown in FIG. 1 are denoted by the same reference numerals. This laser writing control system
Each of the LDs 31 and 32 is provided with two memories for image characteristic conversion. That is, the memories 1A and 1B are provided in the signal processing system on the LD 31 side, and the memories 2A and 2B are provided in the signal processing system on the LD 32 side. Memory 1A
And memory 2A, and memory 1B and memory 2B are memories for the same color. The laser writing control system includes, for each of the LDs 31 and 32, a memory selection circuit for selecting a memory to be used for each color, and a data selection circuit for inputting data of the selected memory to the LD control circuit. And a circuit. That is, the memory selection circuit 61 and the data selection circuit 71 are provided in the signal processing system on the LD 31 side.
The signal processing system on the LD 32 side is provided with a memory selection circuit 62 and a data selection circuit 72, respectively. Each memory 1
The gradation data set for A, 1B, 2A and 2B is
The data is rewritten for each color by the gamma memory control circuit 40 and the process control unit 50. At this time, the process control unit 50 outputs the gradation data of each color, the address signal, and the memory selection signal and inputs them to the gamma memory control circuit 40. The gamma memory control circuit 40 receives the memory select signals S1A, S1B, S2A, S2B input to the memories 1A, 1B, 2A, 2B according to the input memory select signals, and the memory select signals input to the memory select circuits 61, 62. S
Create EL. SEL is a memory select signal for selecting a memory (A or B) for inputting image data.
The memory select signals S1A, S1B, S2A, S
Of 2B, S1A and S2A and S1B and S2B alternately enter the write state. That is, each LD 31, 32
When the gradation data of two memories (A, B) provided for each color is rewritten for each color, one of the memories (for example, A side)
Write data to the other memory (for example, B
Side) is alternately written.

Here, for example, when the gray scale data of the memory 1A and the memory 2A is rewritten to the same data, both the memory select signals S1A and S2A are in a write state,
The same grayscale data Da is simultaneously written to an address Ad common to both memories output from the gamma memory control circuit 40. On the other hand, either one of the memories 1A or 2
When the gray scale data of A is rewritten, only one of the corresponding memory select signals S1A or S2A is in a write state, and the designated address A of one of the memories 1A or 2A is written.
The gradation data Da is written to d. A side memory 1
After the completion of the writing of the grayscale data into A and 2A, the memory selection circuits 61 and 62 select the memories 1A and 2A, and the respective image data (1) and (2) are stored in the memories 1A and 2A on the A side, respectively. Is entered. At this time, the data selection circuits 71 and 7
2 also selects the memories 1A and 2A on the A side, and the image data (1) and (2) are gradation-converted by the memories 1A and 2A on the A side and input to the LD control circuits 11 and 12, respectively. You. Similarly, after the end of the writing of the gradation data to the memories 1B and 2B on the B side, the memory selection circuits 61 and 62 set the memory 1
B and 2B are selected, and each image data (1), (2)
Are input to the memories 1B and 2B on the B side, respectively. At this time, the data selection circuits 71 and 72 are also connected to the memories 1B and 2 on the B side.
B is selected, and the image data (1) and (2) are gradation-converted by the memories 1B and 2B on the B side, and each LD control circuit 1
1 and 12, respectively. According to the above-described embodiment, after the A-side memories 1A and 2A are selected and the image forming process of one color is started, the memory is switched to the B-side memories 1B and 2B to switch the γ data and gradation of another color. Data can be written to memory. As a result, the data rewriting process, which has been performed only during the transition from the previous color image forming process to the next color process, can be started before the previous color image forming process is completed. Even if the time interval between the formation process and the next color image formation process is shortened, the time constraint due to the memory access speed can be relaxed.

FIG. 3 is a block diagram of a main part of a color image forming apparatus showing an example of an embodiment of the present invention. The same components as those of the laser writing control system shown in FIGS. 1 and 2 are denoted by the same reference numerals. The laser writing control system includes a gradation data memory (memory Bk8) for each color.
1, a memory Y82, a memory C83, and a memory M84). When reading gradation data from each gradation data memory and writing it to each image characteristic conversion memory 1, 2, both memories 1, 2 are accessed simultaneously. It is configured such that each of the memories 1 and 2 can be individually accessed. To this end, a data selection circuit 70 and an automatic data switching control circuit 80 are provided. Each gradation data memory 81, 8
2, 83 and 84, the reference gradation data of each color are sequentially input in advance through the gamma memory control circuit 40. When starting the image forming operation, the process control unit 50 first outputs a write start signal ST to the automatic data switching control circuit 90 to write the gradation data of the first color into the memories 1 and 2. Automatic data switching control circuit 90
Receives the write start signal ST, outputs read address data Rad and inputs the read address data Rad to the gamma memory control circuit 40. When the gamma memory control circuit 40 receives the read address data Rad, the gamma memory control circuit 40 stores the address Ad1 specified by Rad common to all memories in each gradation data memory 8.
1, 82, 83, and 84, and output to each gradation data memory 8
1, 82, 83, and 84 output gradation data of each color. The gradation data of each color is input to the data selection circuit 70. At this time, the automatic data switching control circuit 90 outputs the color selection signal CS to the data selection circuit 70, and the data selection circuit 70 selects the gradation data from the gradation data memory specified by the color selection signal CS. Then, the data is output to the automatic data switching control circuit 90.

An automatic data switching control circuit 90 generates write address data Wad and outputs the write address data Wad to the memories 1 and 2 in synchronization with the gradation data input from the data selection circuit 70. Here, both memories 1 and 2
When the gray scale data is rewritten to the same data, both memory select signals S1 and S2 are in a write state, and the same gray scale for the same color is stored in the address Ad2 common to both memories output from the gamma memory control circuit 40. Data is written simultaneously. On the other hand, when rewriting the grayscale data of one of the memories 1 or 2, the memory selection signal MS for selecting the memory 1 or 2 and the address data Ad2 are sent from the gamma memory control circuit 40 to the automatic data switching control circuit 90. Is output. The automatic data switching control circuit 90 activates only the memory select signal S1 or S2 of one of the memories 1 or 2 selected by the memory select signal MS. As a result, the gradation data is written to the specified address Ad2 of one of the memories 1 and 2. Each time the image forming process for the previous color is started, the above-described gradation data writing operation is performed by switching the gradation data by the color selection signal CS, and is completed when the gradation data for all the colors has been written. I do.

According to the above embodiment, when reading out the gradation data of each color from each of the gradation data memories 81, 82, 83 and 84 and writing them to the memories 1 and 2 for image characteristic conversion, the two memories 1 and 2 are used. When rewriting the same grayscale data to the same data, both memories 1 and 2 are accessed simultaneously, and when rewriting to different data for each memory 1 and 2, each memory 1 and 2 is individually accessed and Data can be rewritten without much time difference from the case of the beam writing method. Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, after completion of image formation, that is, every time the image forming process for all colors is completed, the gradation data of the color frequently used for the first color in the next image formation is converted to the image characteristic. If the data is written in the conversion memories 1 and 2, the processing speed in the case where image formation is continuously performed can be further improved. (Corresponding to claim 4) In the above example, a two-beam type laser writing control system including two LDs as laser light sources has been described, but this does not limit the present invention in any way. The number of light sources may be three or more.

[0014]

As described above, the present invention exhibits the following excellent effects. According to the first aspect of the present invention, there is provided a color image forming apparatus of a multi-beam writing system for writing a latent image by simultaneously irradiating a plurality of laser beams to a photoconductor using a plurality of laser light sources. When rewriting the gamma data and gradation data of the image characteristic conversion memory provided for each light source for each color, when rewriting the gamma data and gradation data of all the memory for image characteristic conversion to the same data, the image characteristics All memories for conversion can be accessed at the same time, and when rewriting to different data for each memory, it can be accessed individually for each memory, so
Data can be rewritten without much time difference from the case of the single beam writing method. According to the second aspect of the present invention, in the first aspect, two memories for image characteristic conversion are provided for each laser light source so that both memories can be accessed alternately. The gamma data and gradation data of the next color can be written to the memory even during the period other than when the process is shifted to the next process, and the conventional memory access speed can be sufficiently used. According to the third aspect of the present invention, in the first or second aspect, a gradation data memory is provided for each color, and when reading gradation data from each gradation data memory and writing the gradation data to a memory for image characteristic conversion, When rewriting grayscale data of all memories for image characteristic conversion to the same data, all memories can be accessed at the same time, and when rewriting to different data for each memory, it can be accessed individually for each memory. Therefore, data can be rewritten without much time difference from the case of the single beam writing method. Claim 4
According to the described invention, in claim 1, 2 or 3,
After completion of image formation, gradation data of a color frequently used for the first color in the next image formation process is written to the memory for image characteristic conversion, so that the operation sequence for image formation is smoothed. The processing speed in the case where image formation is continuously performed can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a color image forming apparatus showing an example of an embodiment of the present invention.

FIG. 2 is a main part block diagram of a color image forming apparatus showing an example of the embodiment of the invention described in claim 2;

FIG. 3 is a main block diagram of a color image forming apparatus showing an example of the embodiment of the invention described in claim 3;

[Explanation of symbols]

 1, 2: Memory for image characteristic conversion 1A, 1B: Memory for image characteristic conversion 2A, 2B: Memory for image characteristic conversion 11, 12: LD control circuit 21, 22: LD modulation circuit 31, 32: Laser diode (Laser light source) 40: Gamma memory control circuit 50: Process control unit 61: Memory selection circuit 62: Memory selection circuit 70: Data selection circuit 71: Data selection circuit 72: Data selection circuit 80: Automatic data switching control circuit 81, 82 , 83, 84: gradation data memory

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/23 B41J 3/00 B 5C066 5/907 G06F 15/68 310A 5C072 9/69 H04N 1/04 104Z 5C07 9/804 9/80 B 9/808 F term (reference) 2C262 AA05 AA17 AB19 BB03 BC01 GA09 GA10 GA11 GA12 GA13 GA14 GA15 GA36 GA39 2C362 BA51 BA66 CA16 CA28 CA29 CA30 CA37 CB75 CB77 5B057 CA01 CB01 CE11 CH04 CH07 CH11 CH11 AA17 AB04 DD10 FA02 FA03 FB01 FD02 FD03 FE04 FE08 GA02 GA05 GB01 GD09 GE04 5C055 AA07 BA06 BA08 EA05 EA06 FA02 FA05 HA17 5C066 AA05 CA01 CA23 EC05 GA01 HA02 KE09 KE11 KF01 KF05 KG01 A03H03 A033

Claims (4)

[Claims] 1. A multi-beam writing type color image forming apparatus for writing an image by simultaneously irradiating a plurality of laser beams to a photoconductor using a plurality of laser light sources, wherein image characteristic conversion is performed for each laser light source. When rewriting the γ data of the image characteristic conversion memory for each color, all the memories for image characteristic conversion can be accessed simultaneously or each memory can be accessed individually. A color image forming apparatus. 2. The color image forming apparatus according to claim 1, wherein two memories for image characteristic conversion are provided for each laser light source, and the memories to be used can be switched for each color. 3. A gradation data memory is provided for each color, and when reading gradation data from each gradation data memory and writing the gradation data to a memory for image characteristic conversion, all the memories for image characteristic conversion are accessed simultaneously. 3. A color image forming apparatus according to claim 1, wherein each of said memories can be individually accessed. 4. The image processing apparatus according to claim 1, wherein after completion of image formation, gradation data of a color frequently used for the first color in the next image formation is written in a memory for image characteristic conversion. The color image forming apparatus according to any one of claims 1 to 3.