JPH04150166A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a recording picture with high picture quality by providing a gradation processing unit setting a block comprising plural picture elements and growing a dot in the order of a dot corresponding to a minimum recording picture element position with high priority to the title device. CONSTITUTION:This device is provided with a gradation processing unit 2 receiving a picture data from a digital data output device 1 and implementing gradation processing and with a laser beam printer 3 as a printer receiving a picture data subject to gradation processing by the gradation processing unit 2. Then the gradation processing unit 2 sets a block comprising plural picture elements of a picture data so as to allow a dot to grow a dot in the order of a dot corresponding to a minimum recording picture element position with high priority. Moreover, the printer 3 receives a picture data subject to gradation processing by the gradation processing unit 2 to obtain a recording picture. Thus, the recording picture with high picture quality is obtained.

Description

[Detailed Description of the Invention] FIG. 1 shows a schematic diagram of an image forming apparatus in this embodiment. In FIG. 1, reference numeral 1 denotes a digital data output device as an image data output device, and an image scanner, video camera, etc. (not shown) is connected to the image forming device. The input image data is subjected to A/D conversion and predetermined image processing. In this case, the image data may be temporarily stored in the memory, or may be an interface for image data from a direct communication means. Reference numeral 2 denotes a gradation processing device that receives image data from the digital data output device 1 and performs gradation processing, and 3 indicates a laser beam printer serving as a printer to which image data subjected to gradation processing by the gradation processing device 2 is input. be.

FIG. 2 shows the configuration of the gradation processing device 2. In FIG. 2, 21 is a horizontal sync signal generation circuit that outputs a horizontal sync signal for an image, and 22 is a horizontal sync signal generating circuit that counts horizontal sync signals. The output is 0N every time the horizontal synchronization signal is input.
23 is a horizontal binary counter that switches between OFF and OFF and distinguishes between an even line (OFF) and an odd line (ON). This is a gradation conversion table having pixel levels after gradation conversion as memory addresses.

Here, the gradation conversion table 23 will be explained in more detail using FIGS. 3 and 4. FIG. 3 shows the contents of the gradation conversion table 23. If the input image data is 8 bits (256 levels), 256 addresses are required in the table to create one gradation characteristic, and in this example, two gradation characteristics, an even line and an odd line, are required. , so a total of 512 addresses are required. That is, address 0OHFFH represents the gradation characteristics of even lines, and address 100H-I
FFH represents the gradation characteristics of odd-numbered lines.

FIG. 4 is a graph showing the tone conversion characteristics. When the image density is low, the pixels on the odd lines are not printed and the dot size of the pixels on the even lines is adjusted to reproduce the gradation, and when the image density is high, the dots on the even lines are saturated. The gradation is reproduced by printing and adjusting the dot size of odd-numbered pixels.

In other words, two horizontally adjacent even and odd lines
The characteristics of the gradation conversion table are set so that pixels on even lines are set in one block, and recording dots are grown with priority given to pixels on even-numbered lines.

In particular, in electrophotographic printers, it is better to give priority to the growth of dots of specific pixels than to grow dots of each pixel uniformly, which is more effective against microscopic areas of electrostatic latent images on the photoreceptor. An electric field is generated and the gradation of the recorded image is improved.

In this example, the size of the block is explained as two pixels in the horizontal direction for simplicity, but it is not limited to this (,
It can be set to any size, and the pixel in the block that is preferentially grown in dots is not limited to one (it may be more than one).

Next, the laser beam printer 3 shown in FIG. 1 will be explained in detail using FIGS. 5 to 8.

FIG. 5 is a side sectional view of the laser beam printer 3, FIG. 6 is an explanatory diagram of the operation of photoconductor reference detection, and FIG. 7 is an explanatory diagram of the operation of intermediate transfer member reference detection.

In FIG. 5, 101 is selenium (Se
) or organic photoconductor (OPC) is a photoreceptor coated with a thin film, and two photoreceptor conveying rollers 1
02.103, and is driven by a drive motor (not shown) to rotate in the direction of arrow A.

Around this photoconductor 101, a charger 104, an exposure optical system 105, and a block (
B), cyan (C), magenta (M), yellow (Y)
Developing units 106B, 1106C1106, 106 for each color
Y, intermediate transfer unit 107, photoconductor cleaning device 108, static eliminator 109, and photoconductor reference detection center 1
10 are provided.

The charger 104 is composed of a charging wire 111 made of tungsten wire or the like, a shield plate 112 made of a metal plate, and a grid plate 113.

In addition, developing devices 106B and 1106C1106 for each of the above colors are provided.
, 106Y store toner corresponding to each color. The selection of the toner color is performed using a separation cam 115B, which corresponds to each color and whose both ends are rotatably supported on the body of the machine.
115c, 115M, and 115Y are rotated in response to a color selection signal, and this is done by, for example, bringing the developing device 106B into contact with the photoreceptor 101. The remaining unselected developing devices 1106C5106 and 106Y are spaced apart from the photoreceptor 101.

The intermediate transfer body unit 107 includes a seamless loop belt-shaped intermediate transfer body 116 made of conductive resin or the like, intermediate transfer body conveyance rollers 117 and 118 that support the intermediate transfer body 116, and intermediate transfer body 116. The image forming apparatus includes an intermediate transfer roller 119 disposed opposite to the photoreceptor 101 with an intermediate transfer member 116 in between to transfer the one-henner image on the photoreceptor 101 to the photoreceptor 101 . Here, the surface circumference L1 of the photoreceptor 101 is nominally equal to the surface circumference L2 of the intermediate transfer body 116, but is set so that the relationship L1≦L2 always holds within the range of variation.

122 is an intermediate transfer body cleaning device for scraping off residual toner on the intermediate transfer body 116;
The intermediate transfer member 116 is separated from the intermediate transfer member 116 while a composite image is being formed on the intermediate transfer member 116, and comes into contact with the intermediate transfer member 116 only when it is used for cleaning. A transfer material cassette 123 stores a transfer material 124, and the transfer material 124 is sent out one by one from the transfer material cassette 123 to a paper conveyance path 126 by a half-moon-shaped paper binding roller 125.

Reference numeral 127 temporarily transfers the transfer material 124 to match the position of the composite image formed on the transfer material 124 and the intermediate transfer body 116.
This is a registration roller for stopping and waiting, and is in pressure contact with the driven roller 128.

A transfer roller 129 is used to transfer the composite image formed on the intermediate transfer body 116 to the transfer material 124, and rotates in contact with the intermediate transfer body 116 only when the composite image is transferred to the transfer material 124.

130 is a fixing device consisting of a heat roller 131 and a pressure roller 132 which have a heat source inside, and applies pressure and heat to the composite image transferred onto the transfer material 124 as the heat roller 131 and the pressure roller 132 rotate. Transfer material 124 by
to form a color image.

In FIG. 6, 110 is a seam 101a of the photoreceptor 101.
The photoreceptor reference mark 101b, such as a slit, is placed at a predetermined position relative to the seam 101a of the photoreceptor 101. 121 outputs 0 power from a drive source (not shown).
This is a photoreceptor clutch mechanism that controls the rotation of the photoreceptor by turning it off, and is provided on the drive shaft of the photoreceptor conveying roller 103.

In FIG. 7, 120 is an intermediate transfer body reference detection sensor that detects the reference position of the intermediate transfer body 116, and the reference position is detected by an intermediate transfer body reference mark 116a such as a slit placed at one end of the intermediate transfer body 116. Detect.

With the above device configuration, the photoconductor 101 and the intermediate transfer body 11
6 are each driven by a drive source (not shown), and are controlled so that their circumferential speeds are the same constant speed. Further, an image forming area of the intermediate transfer body 116 is set in advance by an intermediate transfer body reference detection center 120 that detects an intermediate transfer body reference mark 116a for determining a reference position, and within this area, a seam of the photoreceptor 101 is formed. 101a
The positions of the intermediate transfer rollers 119 are adjusted so that they do not overlap, and they are driven in synchronization.

In this state, the charger 104 connected to the high-voltage power supply is first charged! ! A high voltage is applied to the photoreceptor 111 to cause corona discharge, and the surface of the photoreceptor 101 is uniformly charged to about -700V to -800V.

Next, the photoconductor 101 is rotated in the direction of arrow A, and exposure light 4!114 of a laser beam corresponding to a predetermined color among the plurality of color components, for example, black (B), is applied onto the uniformly charged surface of the photoconductor 101. When the exposure optical system 115 irradiates the photoreceptor 101 with the exposure light beam 114, the charge disappears on the portion of the photoreceptor 101 that is irradiated with the exposure light beam 114, and an electrostatic latent image is formed.

At this time, this electrostatic latent image is placed on the photoconductor 101 at a position within the image area on the intermediate transfer body 116 that is preset by a signal from the intermediate transfer reference detection sensor 120 that detects the reference position of the intermediate transfer body 116. It is formed avoiding the seam 101a.

On the other hand, the developing device 106B containing black toner that contributes to development is moved to the separation cam 115B by the color selection signal.
Due to the rotation of , it is pushed in the direction of arrow B and comes into contact with the photoreceptor 101 . With this contact, toner adheres to the electrostatic latent image portion formed on the photoreceptor 101 to form a toner image, and development is completed. The developing device 106B that has completed development is moved to the separation cam 115B.
As a result of the 180 degree rotation of the photoreceptor 101, the photoreceptor 101 moves from the contact position to the separation position.

The toner image formed on the photoreceptor 101 by the developing device 106B is transferred onto the intermediate transfer member 116 by applying high pressure to an intermediate transfer roller 119 placed in contact with the photoreceptor 101. Residual toner that has not been transferred from the photoconductor 101 to the intermediate transfer body 116 is removed by the photoconductor cleaning device 1.
The charge on the photoreceptor 101 after the residual toner is scraped off by the static eliminator 109 is removed by the static eliminator 109 .

Next, when the color cyan (C), for example, is selected, the separation cam 115C rotates, and this time the developing device 106C is connected to the photoreceptor 10.
Press in the direction of 1 to bring it into contact with the photoreceptor 101 and press cyan (C).
Start developing. In the case of a copying machine or printer that uses four colors, the above-mentioned developing operation is sequentially repeated four times, and toner images of four colors B, C, M, and Y are superimposed on the intermediate transfer member 116 to form a composite image.

The composite image formed in this way is transferred from the transfer material cassette 123 to the paper transport path by bringing the paper transfer roller 129, which has been separated so far, into pressure contact with the intermediate transfer member 116 and applying high pressure to the paper transfer roller 129. The image is transferred all at once onto the transfer material 124 that is sent along the line 126. In this way, the transfer material 124 to which the toner image has been transferred is transferred to the fixing device 1.
30, where it is fixed by the heat of the heat roller 131 and the clamping pressure of the pressure roller 132, and is output as a color image.

The residual toner on the intermediate transfer body 116 that has not been completely transferred onto the transfer material 124 by the paper transfer roller 129 is removed by the intermediate transfer body cleaning device 122 . The intermediate transfer member cleaning device 122 is located at a distance from the intermediate transfer member 116 until one composite image is obtained;
After the composite image is transferred onto the transfer material 24 by the paper transfer roller 129, they come into contact and residual l/toner is removed.

With the above operations, recording of one color image is completed, and a high quality color recorded image is obtained.

Note that the printer is not limited to the electrophotographic method using a laser beam of this embodiment, but may be a thermal transfer method, an inkjet method, or the like.

Further, an LED method, a single liquid crystal shutter method, etc., which are the same electrophotographic method, may be used.

Although this embodiment deals with a full-color printer in which gradation reproduction is important, it is of course possible to use a single-color printer.

Further, in this embodiment, a method of superimposing the color image on the intermediate transfer member was adopted, but a method of superimposing the color image on a photoreceptor or a method of superimposing it on transfer paper may also be used.

(Effects of the Invention) As explained above, the present invention includes an image data output device that processes and outputs transmitted or accumulated image data, and a block consisting of a plurality of pixels on the image data,
a gradation processing device that grows dots in the block in order from a dot corresponding to a minimum distributed pixel position with a high priority according to a spatially predetermined priority order; Since the image forming apparatus is constituted by a printer that inputs image data and obtains a recorded image, it is possible to obtain a high quality recorded image.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an image forming apparatus in an embodiment of the present invention, FIG. 2 is a block diagram showing a gradation conversion device, FIG. 3 is an explanatory diagram of a gradation conversion table, and FIG. 4 is a gradation conversion table. Characteristic diagram of the table, Figure 5 is a side sectional view of the laser beam printer,
FIG. 6 is an explanatory diagram of the operation of photoconductor reference detection, and FIG. 7 is an explanatory diagram of the operation of intermediate transfer member reference detection. 1... Digital data output device, 2... Gradation conversion device, 3... Laser beam printer. Figure N Transition 5 Bun Mei En Cloud Δ ゛(→Figure Figure

Claims (1)

[Claims] An image data output device that processes and outputs transmitted or accumulated image data, and a block consisting of a plurality of pixels on the image data are set, and priorities are determined according to a spatially predetermined priority within the block. An image forming apparatus comprising: a gradation processing device that grows dots in order from a dot corresponding to a minimum recording pixel position with a high value; and a printer that inputs gradation-processed image data from the gradation processing device to obtain a recorded image. Device.