JPH0515570U - Image recorder - Google Patents

Abstract

(57) [Abstract] [Object] The present invention relates to an image recording apparatus applicable as both a printer and a facsimile, and particularly provides an image recording apparatus capable of changing the pixel density in the sub-scanning direction as well as in the scanning direction. To aim for things. An image recording apparatus including a print engine that forms an image on a generatrix of a photosensitive drum that rotates in a sub-scanning direction while performing optical output based on video data generated in synchronization with a video clock, A frequency division ratio switching circuit configured to switch a frequency division ratio of an original transmission clock by a pixel density switching signal, a video clock generation circuit configured to generate the video clock by an output pulse from the circuit, and the photoconductor. An image recording apparatus comprising a plurality of oscillation pulses for controlling rotation of a pulse motor for driving a drum, and a pulse switching circuit configured to switch the oscillation pulses by the pixel density switching signal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an image recording device capable of outputting a plurality of image information having different pixel densities, such as a facsimile device having a printer function.

[0002]

[Prior Art]

 Conventionally, the printer function and the facsimile function have been combined, for example, a facsimile function, or a printer function that can be connected to a personal computer and print the document information input to the personal computer can be used in various ways depending on the situation. Facsimile devices are known. In such a facsimile machine with a printer function, it is necessary to match the two machines having originally different generation processes by combining them. The biggest difference is the difference in pixel density.

That is, the pixel density when an original is read by an image sensor incorporated in a facsimile is 200 dpi or 400 dpi, and therefore the resolution of the printing unit output on the called side is the same as that of the read transmission data on the calling side. A pixel density of 200 dpi or 400 dpi is adopted according to the resolution. On the other hand, since the pixel density of the printing software used for laser printers and other page printers is created based on 300 dpi, when the image transmitted at 200 dpi or 400 dpi is output at 300 dpi, the pixel density becomes Since they are different, color unevenness such as white streaks and black streaks is likely to occur in the printed result.

Various methods can be considered to correct such a difference in pixel density. One of them is a technique for changing the rotation speed of a motor that drives a rotary polygon mirror that optically scans a laser beam. As such a technique, for example, in Japanese Patent Laid-Open No. 64-82010, there is provided a frequency dividing means for dividing an output clock having a frequency corresponding to the rotational speed of the rotating polygon mirror, and by changing the frequency division ratio of the frequency dividing means. We have proposed a laser printer configured to change the motor speed and the recording pixel density.

[0005]

[Problems to be solved by the device]

 Certainly, in the above-mentioned conventional technology, by dividing the speed information of the motor that drives the rotary polygon mirror, the scanning speed of the rotary polygon mirror can be diversified and the pixel density can be changed little by little. However, changing the density in the main part of the fan that performs scanning is a large error on the drum bus line on which the beam is printed, even if the speed is adjusted accurately by the frequency division processing described above. However, there is a problem in that the motor control circuit is complicated and the price rises.

Further, in the above-mentioned method, since the density is changed only in the main scanning direction, unless the speed control in the sub-scanning direction is also set, the output speed performance is impaired and the resolution cannot be improved.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an image recording apparatus capable of accurately changing the pixel density in the sub-scanning direction as well as the scanning direction.

[0008]

[Means for solving the problem]

 The present invention is equipped with a print engine that forms an image on the bus line of a photosensitive drum that rotates in the sub-scanning direction while performing optical output based on video data generated in synchronization with a video clock, such as a laser. In an image recording device such as a printer, an LED printer or the like, the pixel density in the main scanning direction can be changed by a frequency division ratio switching circuit configured to switch the frequency division ratio of the original oscillation clock by a pixel density switching signal, and the circuit. The video clock generation circuit is configured to generate the video clock by the output pulse of the above. On the other hand, the pixel density in the sub-scanning direction is changed by rotating the pulse motor for driving the photoconductor drum. A plurality of oscillation pulses for control are prepared, and the oscillation pulses can be switched by the pixel density switching signal. In point configured to perform the pulse switching circuit.

[0009]

[Action]

 According to such a technical means, the pixel density in the main scanning direction is not changed by changing the rotation speed of the polygon mirror, which is a fan for optical scanning, but the pulse of the video clock for generating the video data. Since the width is changed and the print engine does not need to change anything, it is possible to change the pulse density with high accuracy. Further, in the sub-scanning direction, the speed of the motor is not adjusted, but the oscillation pulse for driving the drum is switched based on the oscillation pulse. Therefore, not only an accurate error-free rotation control is possible. No complicated drive control circuit for rotation adjustment is required. Therefore, according to the present invention, the pixel density can be easily switched between the main scanning and the sub scanning without complicating the circuit configuration.

[0010]

【Example】

 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a printer control circuit according to an embodiment of the present invention. Reference numeral 1 is a decision circuit composed of an inverter 2 and AND gates 3a and 3b, 4 is a program counter, 5 is a flip-flop circuit which generates video clocks Vc1 and Vc2 based on the counter pulse CP from the program counter 4, and 6 is a call. An image control system that generates video data based on the image information transmitted from the facsimile machine on the side or the character code transmitted from the personal computer side, and serially outputs the video data to the printer engine side while synchronizing the video data with the video clock. Control circuit, 8 is a semiconductor laser that outputs a laser beam modulated based on the serially output video data, 9 is a polygon mirror that optically scans a laser focused through a lens system 19 in the main scanning direction, 10 is on the drum bus while focusing the scanning beam An F.theta. Lens for forming an image, 11 a photosensitive drum, 12 a pulse motor for driving the drum 11, 13 an oscillation pulse selection circuit, in which oscillation clocks 14a, 14b corresponding to 300 dpi and 400 dpi are built-in. The output pulse from any one of the clocks can be selected based on an image switching signal described later.

Next, the operation of the above embodiment will be described by dividing it into a pixel density conversion method in the main scanning direction and a pixel density conversion method in the sub scanning direction. FIG. 2 is a timing chart for explaining the pixel density conversion operation in the main scanning direction. For example, when a switching signal maintained at LOW is input to the program counter 4 through the determination circuit 1, the program counter 4 outputs a counter pulse CP2 every three reference clocks CLK, and the counter pulse CP2 is flip-flopped. The video clock VC2 obtained by dividing the reference clock CLK by 3 is output by passing through the clock 5 in FIG. Then, in the present embodiment, by setting the reference clock so that the video clock VC2 divided by 3 corresponds to 400 dpi, the video clock VC2 that matches the pixel density of the fax machine is generated.

On the other hand, by switching the switching signal to Hi, the program counter 4 is switched so that the counter pulse CP1 is output for every four reference clock CLK numbers, and the counter pulse CP1 is passed through the flip-flop 5, whereby the reference pulse CP1 is output. A video clock VC1 obtained by dividing the clock CLK by 4 is output, and as a result, a 300 dpi video clock VC1 that matches the pixel density of the printer is generated. Then, in synchronization with the generated video clock, a laser beam modulated based on the video data output to the printer engine side is imaged on the polygon mirror 9 from the semiconductor laser 8 and is optically scanned, while the photosensitive drum is being scanned. A latent image with a predetermined pitch is formed on the 11 bus lines.

On the other hand, the switching signal is also input to the oscillation pulse selection circuit 13, and the oscillation pulse corresponding to 300 dpi is generated in the circuit 13 based on the Hi signal, and the circuit 13 based on the LOW signal. It is also possible to change the pixel density in the sub-scanning direction by selecting the oscillation pulse corresponding to 400 dpi and driving the pulse motor 12 based on the corresponding oscillation pulse.

It is possible to obtain various pulse outputs by switching the counter value of the program counter 4 in the circuit of FIG. 1 or by encoding the pixel density switching signal. It can correspond to.

[0015]

【effect】

 As described above, according to the present invention, it is possible to provide an image recording apparatus capable of accurately changing the pixel density in the sub-scanning direction as well as in the main scanning direction. As a result, a recording apparatus that can be used both as a printer and as a facsimile is simple. It is possible to provide with various circuit configurations. It has various remarkable effects.

[Brief description of drawings]

FIG. 1 is a block diagram of a printer control circuit according to an embodiment of the present invention.

FIG. 2 is a timing chart diagram in the block diagram of FIG.

[Explanation of symbols]

 4 Frequency division switching circuit 5 Video clock generation circuit 11 Photoreceptor drum 12 Pulse motor 13 Pulse switching circuit

Claims (1)

[Scope of utility model registration request] 1. An image recording apparatus comprising a print engine for forming an image on a bus line of a photosensitive drum rotating in a sub-scanning direction while performing optical output based on video data generated in synchronization with a video clock. A frequency division ratio switching circuit configured to switch a frequency division ratio of an original oscillation clock by a pixel density switching signal, a video clock generation circuit configured to generate the video clock by an output pulse from the circuit, An image recording apparatus comprising a plurality of oscillation pulses for controlling the rotation of a pulse motor for driving the photosensitive drum, and a pulse switching circuit configured to switch the oscillation pulses by the pixel density switching signal.