JPH05278262A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] A simple circuit configuration and simple processing
Toon image is formed. A gradation signal output from a gradation data output control circuit based on a control signal from a sub-scanning direction synchronization control circuit is converted into a pulse signal via a pulse data conversion circuit and a pulse width modulation circuit. One beam point 103 is formed for each halftone dot 101 in the main scanning direction by the generated pulse signal. Further, the pulse width modulation circuit has the beam point 10
A pulse signal is output so that a maximum beam diameter of 3 forms a beam having a width required to inscribe the halftone dot 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image by an electrophotographic process such as a laser printer,
The present invention relates to an image forming apparatus capable of forming a halftone image for expressing an intermediate color.

[0002]

2. Description of the Related Art Conventionally, a method using a dot generator is well known for forming a hood in an image forming apparatus, particularly an electrophotographic image forming apparatus such as a laser printer. There is. Here, FIG. 4 shows a conventional dot generator.
3A and 3B are diagrams showing dots formed on a photoconductor in order to explain the data type, in which 101 is a halftone dot, 102 is a pixel, and 103 is a beam point.

As shown in the figure, in the dot generator system, gradation data is changed by changing the number and size of beam points 103 formed for each halftone dot 101. It expresses gradation. For example, in the figure, each halftone dot 101 consists of 16 pixels 102, four in each of the main scanning direction and the subscanning direction, and each halftone dot has the maximum in the main scanning direction and the subscanning direction. Four each,
A total of 16 beam points 103 are formed.

In order to form such a beam point 103, the gradation data is converted into the number and position of beam points and their respective sizes so as to correspond to the positions of the beam points. A pulse signal having a width corresponding to the pulse position and the size of the beam point is generated and output to the laser diode.
Here, the maximum beam diameter of the beam point 103 is such that at least the pixel 102 is inscribed, and by forming 16 beam points 103 having such a maximum beam diameter on the halftone dot 101, The halftone dot 101 is filled in and the maximum gradation is expressed.

[0005]

However, the image forming apparatus to which the conventional dot generator system is applied has the following problems. (1) Since the gradation data is converted into the number, position and size of a plurality of beam points for each halftone dot, the processing becomes complicated and the circuit for performing the conversion becomes large.

(2) When converting the gradation data into a plurality of beam points, the data concerning the gradation at each of the plurality of beam points is converted.
Data needs to be stored, which increases the required memory capacity.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an image forming apparatus having a relatively simple circuit structure and capable of forming a halftone image by a simple process. To aim.

[0008]

In order to solve the above-mentioned problems, the present invention converts image data into a predetermined pulse signal and creates a latent image consisting of dots in the main scanning direction based on the pulse signal. In the image forming apparatus, the pulse width modulating means is provided with pulse data converting means for converting the gradation data of the image data into pulse data and pulse width modulating means for modulating the pulse width of the pulse data. Based on the output of
The feature is that a desired halftone image is obtained by changing the dot diameter of the dots.

The sub-scanning direction synchronizing means for generating a control signal for synchronizing in the sub-scanning direction and the pulse data converting means based on the control signal output from the sub-scanning direction synchronizing means. Gradation data output control means for controlling the timing of outputting the gradation data, and the pulse width modulation means, based on the pulse signal of the pulse width data conversion means, has a maximum dot diameter of at least a plurality of dots. It is characterized in that it outputs a signal for forming a dot having a width necessary for inscribed in a halftone dot composed of pixels.

The pulse width conversion means outputs a signal for forming a beam for forming a latent image in the main scanning direction.

The image data comprises image data relating to a binary image and image data relating to a halftone image. From the image data, the image data relating to a binary image,
Image data for discriminating whether the image data is related to the hood
Data processing discriminating means, a binary image storage section for storing image data relating to the binary image, and pulse signal generating means for reading out the data in the binary image storage section at a predetermined timing to generate a pulse signal. And a synthesizing means for synthesizing the output of the pulse width modulating means and the output of the pulse signal generating means.

[0012]

The present invention forms the image forming apparatus as described above,
By the output of the pulse width modulation means and the control signal from the sub-scanning direction synchronization means, one dot having a predetermined dot diameter is formed for each halftone dot. Therefore, a simple circuit configuration
Tone images can be formed.

Further, since the pulse signal for the binary image generated by the pulse signal generating means and the pulse signal for the halftone image generated by the pulse width modulating means are combined by the combining means, a simple circuit configuration is provided. Thus, it is possible to form an image in which a binary image and a halftone image are mixed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an image forming apparatus according to the present invention. In the figure, 10 is an image data processing unit,
20 is a V-RAM for binary image, 30 is a video data output circuit, 40 is a gradation data storage memory, 50 is a gradation data output control circuit, 60 is a sub-scanning direction synchronization control circuit, and 70 is A pulse data conversion circuit, 80 is a pulse width modulation circuit, 90
Is a video signal synthesis circuit. 2 is a diagram showing the configuration of a laser printer including the image forming apparatus 100 according to the present invention.

The laser diode 110 is driven by the output of the image forming apparatus 100, and the laser diode 11 is driven.
The laser light emitted from 0 is reflected by the rotary polygon mirror 120 and reaches the printing unit 130. Such a rotating polygon mirror 1
A rotation of 20 forms a latent image for one line in the main scanning direction. The printing unit 130 is exposed to laser light to form a latent image on the photoconductor 131, a charger 132 for uniformly charging the photoconductor 131, and a developing unit 133 for forming a toner image.
The transfer charger 134 applies a reverse potential to transfer the toner image on the sheet, a charge eliminating section 135, and a cleaning unit 136. A sheet (not shown) is conveyed onto the sheet conveying path P, and an image is formed on the sheet by applying a reverse potential by the transfer charger 134.

For the image forming apparatus 100, the control unit 150 controls the image processing command, the line synchronization signal LS, and the mode.
The line synchronization signal LS is output to each of the input / output terminals 140. The signal LS is for controlling the rotation of the motor 140 that rotates the photoconductor 131.

Next, the image forming apparatus 100 will be described. When the image processing command COM is input to the image data processing unit 10, the image data processing unit 10 causes the command COM
Is related to a binary image or a halftone image. If it is a binary image, the image data is expanded in the V-RAM 20 for binary image. The data of the V-RAM 20 for binary image is the video data output circuit 3 at a predetermined timing.
It is output to 0, converted into a predetermined pulse signal, and output to the video signal synthesis circuit 90.

If the image processing command COM is related to a halftone image, it is stored in the gradation data storage memory 40 as gradation data. When it is desired to express N gradations as a whole, the gradation data is the data represented by Log ₂ N bits. For example, when it is desired to represent 128 gradations, the data is 7 bits. Gradation data storage memory 40
The gradation data stored in is stored in the gradation data output control circuit 5
It is output to 0. Further, it is sent from the gradation data output control circuit 50 to the pulse data conversion circuit 70 according to the synchronizing signal Sync.

Here, FIG. 3 is a diagram showing dots formed on the photoconductor in order to explain the beam points for forming the halftone image of the present invention. As shown in the figure, each halftone dot 101 consists of 16 pixels 102, four in each of the main scanning direction and the sub-scanning direction, and one beam dot 103 is provided for each halftone dot 101. It is formed. Therefore, considering the sub-scanning direction, one beam point 103 is formed every four lines. The beam diameter of the beam point 103 is uniquely determined from the gradation data. When the gradation data has the minimum value, it has the minimum beam diameter, and when it has the maximum value, the maximum beam diameter. -It becomes the diameter. Such beam point 10
The maximum beam diameter of 3 is set such that the beam point 103 can inscribe the halftone dot 101. At such a maximum beam diameter, the halftone dots 101 are filled, and the maximum gradation is displayed.

As described above, when forming a halftone image, the beam point 103 is generated every four lines in the sub-scanning direction, so that the sub-scanning direction synchronization control means 60 performs line synchronization. When the signal LS is input and the line is to form the beam point 103, the synchronizing signal Sync is output to the grayscale data output control circuit 50.

Sync signal from the gradation data output control circuit 50
The gradation data output in accordance with Sync is converted into data relating to the pulse width in the pulse data conversion circuit 70, and the pulse width data is further pulse amplitude modulated (PWM) in the pulse width modulation circuit 80. , PWM signals are output to the video signal synthesis circuit 90.

Next, the processing sequence of the image forming apparatus according to the present invention will be described. Here, FIG. 5 is a diagram showing each output signal at points (a) to (e) of the image forming apparatus 100 shown in FIG. As shown in the figure, the line sync signal LS
Indicates that the "L" level pulse is output every time the processing in the main scanning direction is completed, that is, when a new image is formed in the sub scanning direction, and that it is the start of a new line. Informing the circuit 60. In addition, V- for binary images
The data expanded in the RAM 20 is sent to the video data output circuit 30 according to the signal LS, and the binary image pulse signal is output to the video signal synthesis circuit 90.

As described above, since it is necessary to form the data for every 4 lines in the sub-scanning direction for the halftone image, the sub-scanning direction synchronization control circuit 60 causes the sub-scanning direction synchronization control signal LS. The synchronizing signal Sync is sent to the grayscale data output control circuit 50 every time the "L" level pulse is input four times. The gradation data output control circuit 50 outputs the sync signal Sync
Upon receiving the L "level pulse output, the gradation data of a predetermined line is read from the gradation data storage memory 40 and output to the pulse data conversion circuit 70. Further, as described above, the pulse data is converted. Conversion circuit 70 and pulse width modulation circuit 80
A predetermined halftone signal is sent to the video signal synthesizing circuit 90 via.

In the video signal synthesizing circuit 90, the pulse signal of the binary image and the halftone signal are added, and the laser diode 11 is output as a synthesized video data output signal.
It is output to 0.

In this embodiment, the case where the image forming apparatus according to the present invention is applied to the laser printer has been described. However, the present invention is not limited to this, and as long as the dot diameter of dots formed by a predetermined pulse signal can be changed in the main scanning direction, such as an electrostatic printer or an inkjet printer, the present invention is applicable. It is obvious that the image forming apparatus can be applied.

[0026]

As described above, according to the present invention, the following excellent effects can be obtained. (1) Since the hood is represented as one dot for each halftone dot,
The process for forming the screen is simplified, and the screen image can be formed with a simple circuit configuration.

(2) Conventionally, in order to express N gradations, information of log N / m ² bit steps is required for each dot, whereas in the present invention, Log ₂ N bits are required. Therefore, the memory capacity to be stored in the gradation data storage memory can be reduced.

(3) In order to synthesize the pulse signal relating to the binary image generated in the video data output circuit and the pulse signal relating to the halftone image generated by the pulse width modulation circuit in the video signal synthesizing circuit, An image in which a binary image and a halftone image are mixed can be formed with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a configuration of a laser printer including an image forming apparatus according to the present invention.

FIG. 3 is a diagram showing dots formed on a photoconductor in order to explain a beam point of the present invention.

FIG. 4 is a diagram showing dots formed on a photoconductor in order to explain a conventional dot generator system.

5 is a diagram showing output signals (a) to (e) of the image forming apparatus shown in FIG.

[Explanation of symbols]

 10 image data processing unit 20 binary image V-RAM 30 video data output circuit 40 gradation data storage memory 50 gradation data output control circuit 60 sub-scanning direction synchronization control circuit 70 pulse data conversion Circuit 80 Pulse width modulation circuit 90 Video signal synthesis circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G06K 15/00 H04N 1/40 B 9068-5C

Claims (4)

[Claims] 1. An image forming apparatus for converting image data into a predetermined pulse signal and forming a latent image consisting of dots in the main scanning direction based on the pulse signal, the gradation data of the image data. A pulse data conversion means for converting the pulse data into pulse data, and a pulse width modulation means for modulating the pulse width of the pulse data. Based on the output of the pulse width modulation means, the dot diameter of the dot is determined. An image forming apparatus, wherein a desired halftone image is obtained by changing the image forming apparatus. 2. A sub-scanning direction synchronizing means for generating a control signal for synchronizing in the sub-scanning direction, and the pulse data converting means based on the control signal output from the sub-scanning direction synchronizing means. The gradation data
Gradation data output control means for controlling the timing of outputting the data, based on the pulse signal of the pulse width data conversion means,
The image according to claim 1, wherein the pulse width modulation means outputs a signal for forming a dot having a width required to inscribe a dot having a maximum dot diameter of at least a plurality of pixels. Forming equipment. 3. The image forming apparatus according to claim 2, wherein the pulse width conversion means outputs a signal for forming a beam for forming a latent image in the main scanning direction. 4. The image forming apparatus according to claim 2, wherein the image data is an image data and a hard image relating to a binary image.
The image data relating to the screen image, from the image data, the image data relating to the binary image,
Image data for discriminating whether the image data is related to the hood
A data processing discriminating means, a binary image storage section for storing image data relating to the binary image, a pulse signal for reading out the data of the binary image storage section at a predetermined timing, and generating a pulse signal. An image forming apparatus comprising: a generation unit, and a combination unit that combines the output of the pulse width modulation unit and the output of the pulse signal generation unit.