JPH11208024A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To count pixels in a simple circuit constitution and control an image formation condition with high accuracy. SOLUTION: This image-forming apparatus has a ROS optical part 4 scanning (n) optical beams onto a photosensitive body 50 in accordance with read image signals, a pixel counter circuit 41 counting pixels of an image formed by any one of the (n) optical beams output from the ROS optical part 4, and an operation device 57 controlling a formation condition for the image formed on the photosensitive body 50 in accordance with a counted count of pixels by the pixel counter circuit 41.

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 which scans a plurality of optical beams onto an image carrier to form an image.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, the number of pixels of image data to be formed (the number of pixels that become black)
And controls the amount of toner supplied to the toner dispenser by estimating the amount of consumed toner.

[0003] Japanese Patent Application Laid-Open No. 1-115649 discloses a technique of counting image data by thinning it out at predetermined time intervals from the viewpoint of simplifying a counter circuit for black data in a video signal and a sequence circuit. ing.

Further, from the viewpoint of realizing a high resolution digital image in recent years, a multi-beam system in which a plurality of light beams are used to form an image with a plurality of beams alternately for each line when drawing on a photosensitive member is used. (For example, see Japanese Patent Application Laid-Open No. 8-201711).

[0005]

However, in such a multi-beam type image forming apparatus, when the black data is counted as described above to control the toner replenishment amount or the like, the resolution of the digital image is increased. Accordingly, the configuration of the counter circuit and the like becomes very large.

That is, the number of pixels per unit length is increasing due to the increase in resolution of digital images, and it is necessary to configure a counter circuit or the like corresponding to the number of beams by a multi-beam method. It is becoming larger and more complicated.

FIG. 5 shows an example of a counter circuit compatible with the multi-beam system. In this counter circuit, a first adder A1 for counting black data of A-phase image data corresponding to one of the multi-beams, and a second adder A2 for counting Carry output from the first adder A1
And a first adder B1 for counting black data of B-phase image data corresponding to the other of the multi-beams, and a second adder B1 for counting Carry output from the first adder B1.
It comprises an adder B2 and a third adder AB that adds the outputs of the second adder A2 on the A-phase side and the second adder B2 on the B2-phase side and sends it to the control unit.

C output from each of the first adders A1 and B1
arry is the black data of the image data, for example, 65535.
One is output at the stage of counting. As described above, the multi-beam system has a problem that a circuit for counting image data corresponding to each beam must be provided.

Further, when counting the number of pixels of image data in the multi-beam system, the method disclosed in
Although it is conceivable to reduce the number of image data as disclosed in Japanese Patent No. 15649 to simplify the counting circuit and the like, it is possible to reduce the number of image data and count them.
There is a problem that the precision of counting the number of pixels is deteriorated, and precise control cannot be performed, and sufficient image forming conditions cannot be controlled corresponding to high resolution.

According to the present invention, there is provided an image forming apparatus which can control the number of pixels and control image forming conditions in a multi-beam type image forming apparatus with a simple circuit configuration and without reducing the counting accuracy. The purpose is to provide.

[0011]

SUMMARY OF THE INVENTION The present invention is directed to an image forming apparatus for achieving the above object. That is, the image forming apparatus according to the present invention includes: an optical unit that scans n optical beams toward the image carrier in accordance with the read image signal; and an n optical beam output from the optical unit. The image forming apparatus includes a counter for counting the number of pixels of an image formed by any one of them, and control means for controlling a forming condition of an image to be formed on the image carrier according to the number of pixels counted by the counter.

In the present invention, the number of pixels of an image formed by any one of the n optical beams scanned from the optical means toward the image carrier is counted by the counter. In other words, the number of pixels is counted for each of a plurality of lines in a line along the scanning direction of the optical beam. Since the n optical beams are adjacent to each other, the respective image data are similar, and the number of pixels of the counted line and the number of pixels of the non-counted line are also similar. For this reason, by controlling the image forming conditions based on the number of pixels of the line on which counting has been performed, control can be performed with almost the same accuracy as in the case where control is performed by counting the number of pixels of all lines. Become.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image forming apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a color copying machine which is an embodiment of the image forming apparatus of the present invention.

As shown in FIG. 1, a color copying machine 1 according to this embodiment is roughly divided into a scanner section 2 for reading an image of a document placed on a document table, and an image for processing the read image data. A processing unit 3; a ROS (Raster Output Scanner) optical unit 4 for driving a laser according to the processed image data to irradiate the photoconductor 50 with a light beam;
And an image forming unit 5 for forming an image.

Around the photoreceptor 50 of the image forming section 5, a charging device 51, an electrometer 52 for measuring the potential of the photoreceptor surface, a rotary developing device 53, a transfer device 54, and a cleaner device 55 along the rotation direction. And a discharge lamp 56 are arranged in order. The rotary developing device 53 includes a toner dispensing device 53a that supplies toner images of each color of Bk (black), Y (yellow), M (magenta), and C (cyan) to corresponding developing devices of the rotary developing device. Is provided.

The transfer device 54 has a configuration in which a transfer corotron 54b, a charge removing corotron 54c, a peeling corotron 54d, and the like are arranged along a transfer drum 54a. (Not shown), the toner image formed on the photoconductor 50 is transferred.

Further, a fixing device 7 is disposed below the transfer device 54 in the sheet conveyance direction so as to fix the toner image transferred to the sheet.

Next, the function of each part of the color copying machine will be described with reference to the block diagram of FIG. First, in the scanner section 2, the original is irradiated with the exposure lamp L, and the reflected light is read by the CCD 21 and amplified by the amplifier 22 to an appropriate level. Thereafter, the A / D converter 23 converts the digital image data into 8-bit or 10-bit digital image data.

After the shading correction unit 24 and the gap correction unit 25 perform predetermined correction on the image data, the density converter 26 converts the reflectance data into density data.
The converted image data is sent to the image processing unit 3.

The image processing section 3 performs basic image processing as a color copying machine, that is, color signal conversion, black reproduction (UC
R), MTF processing, etc., to generate image data of four colors of Y (yellow), M (magenta), C (cyan), and B (black). That is, the color signal conversion unit 31 performs color conversion,
Next, the scanner unit 2 and the image forming unit 3 in the gamma correction unit 32
The gradation conversion of each color is performed in accordance with the gradation characteristics of the above.

The image data is converted into analog data by a D / A converter 33, and is output by a comparator 34 to a triangular wave generator 35.
The signal is compared with a signal of a predetermined period sent from the controller and pulse width modulation is performed to perform binarization.

The patch signal generating means 36 generates a plurality of reference patch image signals having different densities, which are patches for controlling image density. Further, in the selector 37, D /
One of the image data converted into analog data by the A converter 33 and the patch image signal generated by the patch signal generating means 36 is selected and sent to the comparator 34.

The selector 37 selects analog image data at the time of normal copying, and when a patch creation instruction is issued from the arithmetic unit 57 of the image forming unit 5 and a patch image signal is output from the patch signal generating means 36, the selector 37 selects the analog image data. Select a patch image signal.

In the multi-scan system for generating a plurality of laser beams, the D / A converter 22, the comparator 34, the triangular wave generator 35, the patch signal generating means 36, and the selector 37 each have a plurality of sets (laser beams). (For the number) (only a part is shown).

The ROS optical section 4 is controlled by a pixel number counter circuit 41 for counting the number of pixels output from one comparing section 34 of the image processing section 3 and an arithmetic unit 57 of the image forming section 5 to vary the amount of laser light. Laser light variable device 4
2 and a laser drive circuit 43. The laser drive circuit 43 receives the signal 2 from the comparator 36 of the image processing unit 3.
On / off control of the laser 44 is performed based on the digitized data.

This laser light is deflected by the polygon mirror 45 and guided to the photoreceptor 50 of the image forming section via the fi lens 46 and the reflection mirror 47.

The result of counting the number of pixels by the pixel counter circuit 41 is sent to the arithmetic unit 57, and is used for controlling the supply amount of each color toner of the toner dispensing device 53a.

Around the photoreceptor 50 of the image forming section 5, a charging device 51, an electrometer 52, a rotary developing device 53, a transfer device 54, a cleaner device 55, and a discharging lamp 56
Are arranged in order. The electrometer 52 measures the potential on the photoconductor 50 in order to control the photoconductor potential. The optical sensor S detects the density of the patch transferred onto the belt B of the intermediate transfer device 56, and the arithmetic device 57 controls image forming conditions according to the output of the electrometer 52 and the optical sensor S.
The charge amount varying device 58 changes the charge amount of the charging device 51 under the control of the arithmetic device 57. Further, the developing bias variable device 53b changes the developing bias.

FIG. 3 is a view for explaining binarization of image data by pulse width modulation in the comparator 34 (see FIG. 2). That is, the input analog image data is compared with a triangular wave, and a portion where the analog image data is larger than the triangular wave is set to "0" to turn off the laser, and a portion where the analog image data is small is set to "1" and the laser is turned on. The data from the comparator 34 to the ROS optical unit 4
Will be sent to

In the color copying machine 1 having such a configuration, an image is formed according to a well-known xerographic process. That is, first, the rotating photoconductor 50 is uniformly negatively charged by the charging device 51, and a first color latent image is formed on the surface of the photoconductor 50 by the laser beam.

In the portion of the latent image written by the laser beam, the first color (Bk:
The negatively charged black toner is developed by the developing device of (black). Next, the developed image is transferred from the sheet tray 8 by the sheet transfer device 6 to a sheet (not shown) wound around the transfer drum 54a and transferred by the transfer corotron 54b.

At this time, the image remaining on the photoconductor 50 without being transferred is removed by the cleaner device 55, and the photoconductor 50 is removed.
Is discharged by the discharge lamp 56. Next, the photoconductor 50 is uniformly negatively charged again by the charging device 51, and the image formation of the second color (Y: yellow) is performed in the same manner as the first color.

The third color (M: magenta) and the fourth color
Developed images of four colors up to the color (C: cyan) are transferred to transfer drum 54
a is sequentially transferred to the sheet on a. After the transfer, the sheet is peeled off from the transfer drum 54a by the peeling corotron 53d and is fixed by the fixing device 7 to complete the color copy. Also,
A static elimination corotron 54c is arranged around the transfer drum 54a, and removes extra charges on the sheet and the transfer drum 54a after the transfer of each color or after the sheet is separated.

In the color copying machine 1 according to the present embodiment,
In particular, the pixel number counter circuit 41 of the ROS optical unit 4 is characterized in that the number of pixels can be counted with a simple circuit configuration, and precise control of image forming conditions can be performed.

FIG. 4 is a block diagram illustrating a pixel counter circuit applied to the color copying machine 1 of the present embodiment. That is, in the pixel number counter circuit, in a multi-beam system that outputs two-phase laser light, a first adder A1 that counts image data of one (for example, A phase) and an output from the first adder A1 And a second adder A2 for counting the number of Crys to be performed.

That is, there is no adder for counting the B-phase image data counted in the conventional counter circuit (see FIG. 5), and only the A-phase image data is counted.

The first adder A1 is composed of a 16-bit adder, and generates gradation data of A-phase image data (for example, 0 to 0).
255) are all added. The object to be added is a range excluding the margin erased portion of the original to be read.

Then, the 16-bit first adder A1 outputs F
When it becomes ULL (FFFF = 65535), Car
ry is output by one, and the Carry is added by the 16-bit second adder A2. The first adder A1
The second adder A2 is cleared when the PageSync signal indicating the point in time when image input to one page is completed becomes inactive.

The signal output from the second adder A2 is sent to the arithmetic unit 57 (see FIG. 2), where the signal is a multiple corresponding to the number of laser beams. For example, in a multi-beam system that outputs two laser beams of A and B phases, the signal output from the second adder A2 is doubled.

The amount of toner supplied by the toner dispensing device 53a (see FIG. 2) is controlled based on the doubled value.

Here, the resolution is 600 SPI (Sampling p).
er inch) color copier, the interval between A-phase and B-phase is 4
2 μm, and the fineness of the actual image data is coarser than this.
0%. Therefore, as in the above-described pixel number counter circuit, even if only the A-phase image data is counted and doubled to obtain the number of pixels in the entire image data, the error from the actual number of pixels in the entire image data is It will be very small.

That is, the configuration of the pixel number counter circuit only needs to count the A-phase image data only, and the image forming condition is controlled by simply doubling the counted pixel number. Even if the control is performed by counting the number of pixels in the entire image data, the control can be performed with the same accuracy.

Further, the number of adders can be reduced as compared with the conventional pixel number counter circuit shown in FIG.
The frequency at which the number of pixels is counted can be reduced by the adder, and the circuit configuration can be simplified.

In the actual control, the arithmetic unit 57 (see FIG. 2) doubles the count of the A-phase image data, calculates the toner supply time by multiplying the toner supply time conversion coefficient, and sends the toner to the rotary developing device 53. Is controlled by the toner dispensing device 53a (see FIG. 2) for supplying the toner.

The pixel number counter circuit shown in FIG. 4 is not limited to this, as an example. Also, A phase and B
When a screen having a different ratio of the image data from the phase is used, an operation corresponding to the ratio may be performed.

Further, in the present embodiment, the case of the multi-beam system for outputting two laser beams of A phase and B phase has been described, but the case of the multi-beam system for outputting two or more laser beams is described. The same is true for That is, the same applies if the number of pixels of the image data is counted for one of the n laser beams and the value is multiplied by n to perform control.

[0047]

As described above, the image forming apparatus of the present invention has the following effects. That is, in a so-called multi-beam type image forming apparatus that scans a plurality of optical beams toward an image carrier according to a read image signal, the number of pixels of an image can be reduced with a simple circuit configuration without lowering accuracy. To control the image forming conditions. As a result, it is possible to provide an image forming apparatus that can sufficiently respond to a demand for higher resolution.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a color copying machine.

FIG. 2 is a block diagram of a color copying machine.

FIG. 3 is a diagram illustrating pulse width modulation by a comparator.

FIG. 4 is a block diagram illustrating a pixel counter circuit.

FIG. 5 is a block diagram illustrating a conventional pixel number counter circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Color copier, 2 ... Scanner part, 3 ... Image processing part, 4 ... ROS optical part, 5 ... Image forming part, 6 ... Paper conveying device, 7 ... Fixing device, 8 ... Paper tray, 41 ... Pixel number counter Circuit, A1: first adder, A2: second adder

Claims (3)

[Claims] An optical unit that scans n optical beams toward an image carrier in accordance with a read image signal; and one of n optical beams output from the optical unit. A counter that counts the number of pixels of the image formed by the image forming apparatus, and control means that controls conditions for forming an image to be formed on the image carrier according to the number of pixels counted by the counter. Image forming apparatus. 2. A condition for forming an image to be formed on the image carrier based on a value obtained by multiplying the number of pixels counted by the counter by n corresponding to the number n of the optical beams. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled. 3. The image forming apparatus according to claim 1, wherein the control unit controls the formation condition by controlling a toner supply amount to a developing unit that performs development on the image carrier. apparatus.