JP2001191584A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device which does not require a bit map data storage part using a plurality of large storage capacity DRAMs or the like and a rapidly operating CPU (control processing unit) for controlling/driving the bit map data storage part in a color printer and thereby, significantly save on a manufacturing cost. SOLUTION: A plurality of line memory units storing serial data, which correspond to a plurality of main scanning lines are incorporated in a serial conversion part 33, and multi-gradation image data which is read from an image data memory unit 22 is sequentially converted to bit map data, at a bit map data conversion part 31, which is, in turn, stored in the line memory units. Further, the bit map data is output to a laser drive part 157, synchronized with dot clock pulses generated at a dot clock generating part 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic method for forming an image with binary dots based on multi-valued input image information, and more particularly to storing multi-gradation image data. The present invention relates to an image forming apparatus comprising: an image data storage unit that converts image data into bitmap data; and a serial conversion unit that outputs serial data to a laser driving unit.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus using an electrophotographic system for forming an image with binary dots based on multi-valued input image information, a printer as an output terminal such as a personal computer or a workstation, There are plain paper fax and digital copier.

FIG. 3 shows an example of a block diagram relating to a main process of image data processing in a conventional printer as the image forming apparatus. An outline of an image data processing process in a conventional printer will be described with reference to FIG.

In FIG. 3, image information sent from an external device 2 such as a personal computer or a work station is input to a controller 20 via an interface 10 of the printer 1. Controller 20
Then, in the image information conversion unit 21 as image information conversion means, the input image information is converted into intermediate language or multi-gradation image data called a display list and stored in the image data memory 22.

The display list includes information for distinguishing fonts, images, figures, etc., coordinate positions on recording paper, font type and size, codes for fonts, images themselves for images, and circles for figures. ,ellipse,
Information such as distinction between straight lines and the like, line thickness and the like is included. If the contents of the display list are characters, font ROM
And so on, the bitmap data of the corresponding character is determined. In the case of the image itself, the multi-level image information of the image portion of the image information input from the external device 2 is converted into multi-level image data including the gradation information for each pixel, and then the image data is stored in the image data memory. 22.

When a display list is created for all the input image information, the engine 40 starts printing. When printing is started, a display list for one page stored in the image data memory 22 is sent to the engine control unit 30. The engine 40 includes, for example, a control panel (not shown) and all other systems related to the actual image printing process.

In the engine control unit 30, bit map data representing binary information at each pixel position of the image is sequentially formed from the display list in the bit map data conversion unit 31, and the bit map data for one page is converted into the bit map data. The data is written to the storage unit 32. The bitmap data written in the bitmap data storage unit 32 is sent to the serial conversion unit 33, where the bitmap data is converted into serial data based on the dot clock supplied from the dot clock generation unit 35, and is converted in the main scanning direction (recording paper advance). The direction perpendicular to the direction is synchronized with the dot clock, and the sub-scanning direction (moving direction of the recording paper) is synchronized with the horizontal synchronizing signal, and is serially output as an image signal to the laser drive unit in the engine 40.

[0008]

However, as is well known, in the conventional image forming apparatus configured as described above, a density level is provided by two types of outputs (binary output) of white dots and black dots. In order to express the output of the intermediate gradation (multi-value output), based on the multi-tone image data stored in the image data memory 22, for example, 4 × 4 dots, 8 × 8 dots, 16 × 16 dots, etc. The grid matrix is assumed to be virtually one pixel, and is processed by a systematic dither method such as a halftone dot method, a vortex method, or a Bayer method.
The value is converted into bitmap data, and one page is stored in the bitmap data storage unit 32.

For this reason, the bitmap data storage unit 32
It is necessary to use a large number of DRAMs or the like having a large storage capacity as a memory device used for the printer. In the case of a color printer, Y (yellow), M (magenta),
A memory device corresponding to four colors (cyan) and K (black) is required, and a cost increase for the bitmap data storage unit 32 is unavoidable, which is a problem.

Further, a method of modulating the width of the black dot to improve the gradation of an output image is also known.
In this case, since the dot width information corresponding to each dot is also stored, it is necessary to further increase the capacity of the memory device, which is a problem.

In addition, such a large-capacity memory is controlled and controlled.
In order to drive, a CPU (Central Processing Unit) that operates at a very high speed is required, which causes a further cost increase, which is a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to convert a line memory for storing a plurality of serial data corresponding to a plurality of main scanning lines into a serial conversion unit. The multi-gradation image data is sequentially converted to bitmap data and output to the laser drive unit, thereby eliminating the need for a bitmap data storage unit for storing bitmap data for one page.
Accordingly, an object of the present invention is to provide an image forming apparatus capable of greatly reducing costs.

[0013]

According to another aspect of the present invention, there is provided an image forming apparatus comprising: an image information converting unit for converting input multi-valued input image information into multi-gradation image data; An image data storage unit that stores the image data, and a serial conversion unit that reads out the image data from the image data storage unit, converts the image data into bitmap data, and outputs the bitmap data as serial data to a laser driving unit.
A laser exposure unit that scans and exposes the image carrier for each main scanning line when driven by the laser drive unit, and that forms an image with binary dots based on multi-valued input image information. A serial memory for storing a plurality of serial data corresponding to a plurality of main scanning lines; and a dot generating a dot clock signal having a frequency that is an integral multiple of a clock signal corresponding to a predetermined resolution. Having a clock signal generator, converting the image data into multi-gradation bitmap data, storing the converted data in the line memory, and then outputting the serial data to the laser driver as serial data synchronized with the dot clock signal. It is characterized by.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a laser beam printer to which the present invention is applied will be described as an example of an embodiment of the present invention with reference to the drawings. In the following description,
The same blocks as those in the conventional example shown in FIG. 3 are denoted by the same reference numerals, and overlapping description will be omitted.

First, the overall configuration of the image forming engine 40 (hereinafter, also simply referred to as an engine) used in the embodiment of the present invention will be described with reference to FIG. The image forming engine 40 used in the embodiment of the present invention is an engine that forms an image of multiple colors (four colors of Y (yellow), M (magenta), C (cyan), and K (black)). It is.

First, the image carrier cartridge 102 detachably provided to the engine 40 will be described. A belt-shaped image carrier (photoconductor) 100 wound around the upper roller 103, the lower roller 105, and the horizontal roller 107 is vertically stretched by the upper roller 103 and the lower roller 105.
Driven in the direction of the arrow.

Further, the image carrier 100 is pressed against the surface where the belt-shaped image carrier 100 moves upward from below in the direction of the closed space CS formed by the image carrier 100, and
A pressing roller 109 is provided as guide means for guiding 00 in the closed space CS direction.

A cleaning means 111 for removing the developer on the belt-shaped image carrier 100 is provided above the surface on which the belt-shaped image carrier 100 moves upward.
In this configuration, the blade 117 is abutted by the counter method, but may be a trail method.

Below the cleaning means 111, a collection box 121 as a collecting means for collecting the developer removed by the cleaning means 111 is provided along the belt-shaped image carrier 100.

Next, an image forming means for forming a latent image on the belt-shaped image carrier 100 will be described. The engine 40 used in the present embodiment is an engine that forms an image of four colors, and therefore has four image forming means for each color. That is, an image exposing unit 125 that forms a latent image for Y (yellow) using laser light on the belt-shaped image carrier 100 and M (magenta) using laser light on the belt-shaped image carrier 100 Image exposure unit 1 for forming a latent image for
27, and an image exposure unit 129 for forming a latent image for C (cyan) on the belt-shaped image carrier 100 using laser light.
And an image exposure unit 131 that forms a latent image for K (black) on the belt-shaped image carrier 100 using laser light.

Since the constructions of the image exposure units 125, 127, 129, and 131 as the four optical writing units are the same, the image exposure unit 125 will be described with reference to FIGS. Description is omitted.

In FIG. 1, a serial image signal output from an engine control unit 30 is sent to a laser driving unit 157, and the laser driving unit 157 modulates and drives a laser beam emitted from a laser light source 133 based on the serial image signal.

The laser light emitted from the laser light source 133 is reflected by the movement of the rotating surface of the polygon mirror 137, is scanned, passes through the fθ lens 139 and the cylindrical lens 141, and passes through the photosensitive surface of the belt-shaped image carrier 100. Scan and expose. By this scanning exposure, an electrostatic latent image is formed on the photosensitive surface of the belt-shaped image carrier 100.

Here, the moving speed of the belt-shaped image carrier 100 is, for example, 600 dots / inch (hereinafter, dot).
/ Inch is referred to as dpi), the laser beam is synchronized so that the surface moves to the image exposure section 125 by 1/600 inch each time the laser beam scans one line. Is modulated so that a light dot hits every inch. As a result, the number of dots per square inch (dpi) is 600 × 600,
A resolution of 600 dpi will be obtained.

At the start of each scan, before the laser beam reaches the belt-shaped image carrier 100, the laser beam detection mirror 148
The laser beam reflected by the optical fiber 149 is sent to the main scanning synchronization signal detection unit 156, where it is converted into an electric signal called a main scanning synchronization signal, and the output of data related to scanning and other data are compared. It is used for synchronization, and is also used for control and test functions of other printers.

Next, the image forming cartridge 135 detachably provided in the image forming apparatus will be described. In the image forming cartridge 135, four developing means for developing the electrostatic latent images of each color formed on the belt-shaped image carrier 100 are provided. That is, a developing unit 142 for developing the latent image formed by the image exposure unit 125, a developing unit 143 for developing the latent image formed by the image exposure unit 127, and an image exposure unit 129
And a developing unit 147 for developing the latent image formed by the image exposure unit 131.

The four developing units 142, 143, 14
5 and 147 have the same configuration, the developing unit 142 will be described, and the description of the other developing units will be omitted. 151, 1
A screw 52 stirs and conveys the Y toner conveyed from a toner supply device (not shown) together with a carrier.
A supply roller 53 supplies a two-component developer composed of a toner and a carrier to the developing sleeve 155. The developing sleeve 155 supports a two-component developer, and the belt-shaped image carrier 1
And then reversely develops the electrostatic latent image on
0, a toner image is formed.

Further, in the image forming cartridge 135, corresponding to the developing units 142, 143, 145 and 147 of the respective colors, there are provided band electrodes of charging means for applying a charge to the belt-shaped image carrier 100. . That is, the band electrode 1 for Y
61, M band electrode 163, C band electrode 165
And the band electrode 167 for K.

On the other hand, the charging means for each color in the present embodiment has grids 171, 173, 175, and 177 for controlling the charging potential on the belt-shaped image carrier 100. These grids 171, 173 Reference numerals 175 and 177 are provided on the image carrier cartridge 102 side.

The paper supply unit 181 is provided with a paper supply cassette 183 in which the transfer paper P is stored. The transfer paper P in the paper feed cassette 183 is carried out by the conveyance roller 185, nipped and conveyed by the conveyance roller pair 187 and the timing roller 188, and fed to the transfer unit 191.

The transfer section 191 includes a transfer pole 193 for transferring the toner image on the belt-shaped image carrier 100 to the transfer paper P by corona discharge, and a belt-shaped image carrier 1 by AC discharge.
A separation pole 195 for separating the transfer paper P from the sheet P is provided.

Reference numeral 200 denotes a fixing unit that applies heat and pressure to the transfer paper P by sandwiching a roller pair 201 including a heat roller and a pressure roller to fuse the toner to the transfer paper P. And a transport roller pair for nipping and transporting the transfer paper P to the discharge tray 211. Reference numeral 220 denotes a paper feed path through which transfer paper P of another size conveyed from a paper feed unit provided outside the apparatus passes.

Next, the operation of the above configuration will be described. When the belt-shaped image carrier 100 is driven in the direction of the arrow, first, a predetermined charging potential is applied to the belt-shaped image carrier 100 by the Y charging means including the band electrode 161 and the grid 171.

Next, an electrostatic latent image is formed on the belt-shaped image carrier 100 by the image exposure section 125. Then, the toner in the developer carried on the developing sleeve 155 of the developing section 142 moves onto the belt-shaped image carrier 100 due to the Coulomb force, and a toner image is formed on the belt-shaped image carrier 100.

The same operation is performed for the remaining colors, that is, M,
Performed for C and K, and Y, on the belt-shaped image carrier 100
M, C, and K toner images are formed. On the other hand, the paper feeding unit 181
Then, the transfer paper P is conveyed toward the transfer unit 191 by the conveyance roller 185 and the conveyance roller pair 187.

The fed transfer paper P is timing-adjusted with the toner image on the belt-shaped image carrier 100 by a timing roller 188, and is then fed to the transfer unit 191 in a synchronized manner. Charged by pole 193,
The toner image on the belt-shaped image carrier 100 is transferred to the transfer paper P.

Further, the transfer paper P is separated from the belt-shaped image carrier 100 by the charge eliminating action of the separation pole 195.

Next, the transfer paper P is heated in the fixing unit 200,
The toner is pressed, the toner is fused to the transfer paper P, and is discharged onto the discharge tray 211 by the pair of transport rollers 210.

The belt-shaped image carrier 10 after the transfer is completed.
The surplus toner on 0 is removed by the blade 117 of the cleaning unit 111 and stored in the collection box 121.

Next, the image data processing step in the laser printer according to the present invention will be described with reference to FIG. 1 which is a block diagram showing the main steps of the image data processing.

First, the configuration and operation of each processing block shown in FIG. 1 will be described. The image information converter 21 converts the color image information sent from the external device 2 via the interface 10 into four colors (Y (yellow), M (magenta), C (cyan), and K (black)) for each color. After that, the multi-valued image information corresponding to each color is converted into multi-gradation image data including gradation information for each pixel at a predetermined resolution. In this embodiment, the predetermined resolution is set to 200 dpi.

The image data memory 22 stores the image information conversion unit 2
An image data memory for each color which stores multi-tone image data of 200 dpi corresponding to each color output from 1 and is n times as large as a main scanning synchronization signal output from a synchronization signal sub-scanning direction counter 37 described later. The image data for one line in the main scanning direction of the 200 dpi multi-tone image data is output to the bitmap data conversion unit 31 at each timing of the 1 / n synchronization signal having a cycle. In this embodiment, n =
3 is set.

The bitmap data conversion unit 31 performs a process such as a systematic dithering method such as a halftone dot method, a vortex method, or a Bayer method on the multi-gradation image data, and outputs 3 × 3 pixels per pixel.
Converted to binary bitmap data of dots, 200d
The image data for one line in the main scanning direction of the multi-tone image data of Pi is output to the serial conversion unit 33 as bitmap data for three lines of 600 dpi.

The serial conversion section 33 is composed of a line memory corresponding to each color for storing three lines of 600 dpi bitmap data, stores it as parallel data for three lines, and then stores the main scan synchronization data detected by the synchronization signal detection section. The data is output to the laser driver 157 as serial data for each line in synchronization with the signal.

The dot clock generator 35 generates a clock signal 3VCLK having a frequency three times the frequency of the clock signal VCLK corresponding to a predetermined resolution.
The serial converter 33 sends dot data of one line of serial data to the laser driver 157 in synchronization with 3VCLK.

The VCLK main scanning direction counter obtains a clock signal VCLK corresponding to a predetermined resolution by dividing the frequency of the 3VCLK clock signal output from the dot clock generating unit 35 to 1/3, and obtains an image data memory. 22. The image data memory 22 sends out 200 dpi multi-tone image data to the bitmap data converter 31 in synchronization with the clock signal VCLK.

The synchronizing signal sub-scanning direction counter 37 divides the frequency of the main scanning synchronizing signal by １ ／ to obtain a ３ synchronizing signal having a triple cycle, and
2.

Next, the overall operation of the printer 1 according to the present invention configured as described above will be described.

In FIG. 3, image information sent from the external device 2 is input to the controller 20 via the interface 10. In the controller 20, the image information conversion unit 21 separates the image information corresponding to each color, converts the image information into multi-gradation image data, and stores it in the image data memory 22.

When all the input image information is converted into multi-gradation image data and stored in the image data memory 22, the engine 40 is started to start image formation.

When the start of the image formation starts, the multi-gradation image data stored in the image data memory 22 expresses the gradation of one pixel. For example, the data is sent to the engine control unit 30 as 8-bit parallel data. Here, the parallel data transmitted from the image data memory 22 is:
In synchronization with the clock signal VCLK corresponding to the predetermined resolution, image data for one line in the main scanning direction of 200 dpi multi-tone image data is sent to the engine control unit 30 every three times the period of the main scanning synchronization signal. I have.

In the engine control unit 30, the bitmap data conversion unit 31 sequentially forms bitmap data representing binary information at each pixel position of the image by referring to a lookup table (not shown).
The data is sequentially sent to the serial conversion unit 33 as bit parallel data in synchronization with a clock signal 3VCLK three times VCLK.

When the bit map data for three lines is written into the line memory corresponding to each color of the serial conversion unit 33, it is converted into serial data based on the triple dot clock signal 3VCLK supplied from the dot clock generation unit 35. The main scanning direction (direction perpendicular to the recording paper traveling direction) is synchronized with the dot clock, and the sub-scanning direction (recording paper traveling direction) is synchronized with the horizontal synchronizing signal. Output to the drive unit.

[0054]

As described above in detail, according to the embodiment of the present invention, a line memory for storing a plurality of serial data corresponding to a plurality of main scanning lines is provided in the serial conversion section, and the multi-gradation is performed. A large-scale bitmap data storage device that stores bitmap data for one page used in a conventional image forming apparatus because image data is sequentially converted to bitmap data and output to a laser driving unit. By using a small-scale line memory device and a low-speed CPU device without the need for an image forming apparatus, it is possible to execute processing equivalent to that of the conventional apparatus, and it is possible to provide an image forming apparatus capable of significantly reducing costs. This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing main steps of image data processing in a laser printer according to the present invention.

FIG. 2 is a configuration diagram illustrating a configuration of an image forming engine that forms a multicolor image in the laser printer according to the present invention.

FIG. 3 is a block diagram illustrating an example of a main process of image data processing in a conventional printer.

[Explanation of symbols]

 Reference Signs List 1 laser printer 2 external device 10 interface 20 controller 30 engine control unit 31 bitmap data conversion unit 33 serial conversion unit 40 engine

Claims (1)

[Claims] An image information conversion unit for converting input multi-valued input image information into multi-gradation image data; an image data storage unit for storing the image data; And a serial conversion unit that converts the data into bitmap data and outputs it to the laser drive unit as serial data.A laser exposure unit that scans and exposes the image carrier for each main scanning line under the drive of the laser drive unit. And an image forming apparatus that forms an image with binary dots based on multi-valued input image information,
The serial conversion unit includes a line memory that stores a plurality of the serial data corresponding to a plurality of the main scanning lines, and a dot clock that generates a dot clock signal having a frequency that is an integral multiple of a clock signal corresponding to a predetermined resolution. Having a signal generator, converting the image data into multi-tone bitmap data, storing the converted data in the line memory, and outputting the serial data to the laser drive unit as serial data synchronized with the dot clock signal. Characteristic image forming apparatus.