KR0125458B1 - Printer - Google Patents

Abstract

The invention is a device for controlling selective pixel size in a electrophotography development printer. Pulse width controlling part(38) expands video data pulse widths generated from video data generating part(34) differently for one another with different setting times, Option part(40) and multiplexer(42) confirm one of many video data whose pulse width is adjusted to engine(36) selectively and engine(36)prints images pursuant to pixel size of pulse width by exposure for a certain time equivalent to video data pulse width from multiplexer(42).

Description

Pixel size control device of electrophotographic developing method

1 is an engine configuration diagram of a general electrophotographic developing system printer.

2 is a conventional circuit diagram.

3 is an operational waveform diagram of FIG.

4 is a circuit diagram of a pixel size adjusting device according to the present invention.

5 is an operational waveform diagram of FIG.

* Description of the symbols for the main parts of the drawings *

32: clock generator 34: video data generator

36 engine 38 pulse width adjusting section

40: selector 42: multiplexer

44, 46: latch circuit 48, 50: end gate

The present invention relates to an electrophotographic developing printer, and more particularly, to an apparatus for selectively adjusting the size of a pixel in a laser beam printer.

In general, the electrophotographic development method is widely used to output images according to video signals in printers, facsimiles, etc. as well as copiers. An example of an electrophotographic developing printer is a laser beam printer.

1 shows a general engine configuration of a laser beam printer employing an electrophotographic development method. In FIG. 1, the charging unit 14 forms a uniform charge in the photosensitive drum 12. The exposure unit 16 forms an electrostatic latent image on the photosensitive drum 12 by exposing the photosensitive drum 12 according to the input video data. The exposure unit 16 includes a laser oscillator for generating a laser beam according to video data, and a laser scanner for scanning the generated laser beam on the photosensitive drum 12. The developing unit 20 transfers the developer to the electrostatic latent image formed on the photosensitive drum 12. The transfer unit 22 transfers the developer formed on the photosensitive drum 12 to the paper.

The fixing unit 24 fixes the developer transferred to the paper onto the paper. The pickup roller 28 picks up and transfers the paper loaded in the cassette 26. The register roller 30 aligns the sheet conveyed by the pickup roller 28.

2 shows a configuration of a conventional circuit for generating video data and applying it to an engine constructed as described above. In FIG. 2, the clock generator 36 generates a transmission clock signal having a period corresponding to the resolution set by the control of a controller (not shown) of the printer. The video data generator 34 generates video data under the control of the controller and applies it to the engine 36 as shown in FIG. 1 in synchronization with the transmission clock signal. At this time, in the video data of the video data generator 34, a pulse corresponding to each pixel of the image to be printed appears.

Now, as shown in FIG. 3A of the video data of the video data generator 34, the exposure unit 16 of the engine 36 exposes the photosensitive drum 12 when the video data is at a low level. Typically, the exposure unit 16 turns on the laser oscillator when the video data is low level and turns off the laser oscillator when the video data is high level. At the same time, the exposure unit scans the laser beam generated from the laser oscillator to the photosensitive drum 12. Therefore, the exposure time is proportional to the on time T as shown in FIG. 3B of the laser diode, and the pixel size of the electrostatic latent image formed on the photosensitive drum 12 by exposure is proportional to the exposure time.

In this case, the video data is generated corresponding to each pixel so that the size of each pixel to be printed is always fixed to a size corresponding to the set resolution.

Therefore, since the size of the pixel is fixed, the user may not adjust the size of the pixel arbitrarily according to the contents of the printed output. In addition, since the pixels are always the same size, there is a problem that the image quality is reduced when the amount of developer is reduced.

Accordingly, an object of the present invention is to provide a pixel size adjusting device capable of selectively adjusting the size of a pixel.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

4 shows a circuit diagram of a pixel size adjusting device according to the present invention. In FIG. 4, the clock generator 32, the video data generator 34, and the engine 36 are the same as those in FIG. 2 and the same reference numerals are used. The pulse width adjusting unit 38 extends the pulse widths of the video data generated by the video data generating unit 34 for different periods of time, respectively, to generate different pulse widths. The selecting unit 40 and the multiplexer 42 The selector selects and applies one of the plurality of video data whose pulse width is adjusted by the pulse width adjusting unit 38 to the engine 36 in response to the user's selection. The selector 40 generates a selection signal in response to the user's pixel size selection. The multiplexer 42 selects and outputs one of a plurality of video data whose pulse width is adjusted by the pulse width adjusting unit 38 according to a selection signal.

The pulse width adjusting unit 38 is an embodiment for delaying the pulse width of the video data by a predetermined multiple of the transmission clock signal period and includes the latch circuits 44 and 46 and the AND gates 48 and 50. The latch circuits 44 and 46 sequentially delay the video data of the video data generator 34 during one cycle of the transmission clock signal of the clock generator 32. The AND gate 48 logically multiplies the video data of the video data generator 34 and the delayed video data of the latch circuit 44. The AND gate 50 logically multiplies the video data of the video data generator 34 and the delayed video data of the latch circuit 46.

When the transmission clock signal generated by the clock generator 32 of FIG. 4 is equal to that of FIG. 5A, the video data generator 34 synchronizes with the transmission clock signal as shown in FIG. 5B of FIG. Is generated, the generated video data is simultaneously applied to the multiplexer 42 and the latch circuit 44. Then, the latch circuit 44 latches the input video data by the transmission clock signal to delay output for t time as shown in FIG. 5C, and the latch circuit 46 receives the delayed video data from the latch circuit 44. By latching by the transmission clock signal, as shown in FIG. Therefore, the video data output from the latch circuit 46 is in a state where the original video data is delayed for 2t time. Here, t time corresponds to one period of the transmission clock signal.

Accordingly, in AND gate 48 which logically multiplies the video data of the video data generator 34 and the delayed video data of the latch circuit 44, the video data of which the pulse width is delayed and extended by t time as shown in FIG. Output to the multiplexer 42. In addition, the AND gate 50, which logically multiplies the video data of the video data generator 34 and the delayed video data of the latch circuit 46, displays the video data whose pulse width is delayed and extended by 2t time as shown in FIG. Output to the multiplexer 42.

When the user selects the pixel size in the above state, the selector 40 generates a selection signal corresponding to the pixel size and applies it to the multiplexer 42. Therefore, the multiplexer 42 includes video data in which the pulse width of the video data generator 34 is not adjusted, video data in which the pulse width is extended by t hours of the AND gate 48, and 2t time of the AND gate 50. One of the video data having the extended pulse width is selected and output according to the selection signal.

The engine 36 then performs exposure for a time corresponding to the pulse width of the video data output from the multiplexer 42 to print an image composed of pixels of a size corresponding to the pulse width of the video data.

Therefore, the size of the pixel is adjusted by the user's selection. Although the pulse width of video data is extended by a certain multiple of the transmission clock signal in order to adjust the size of the pixel, it can be expanded or reduced as desired by using a monostable multivibrator, counter or timer circuit. It may be noted that may be.

As described above, the present invention has the advantage that the user can selectively adjust the pixel size. In addition, when the amount of the developer is decreased, the size of the pixel can be used to compensate for the deterioration in image quality.

Claims (4)

In an electrophotographic developing system printer, video generating means for generating a transmission clock signal having a period corresponding to a set resolution and video data generated by synchronizing the transmission clock signal with video data indicated by a pulse corresponding to each pixel of an image. A pulse width adjusting means for generating a plurality of video data having different pulse widths by extending the data generating means and the pulse width of the video data for a predetermined time period, and the plurality of video data having the pulse widths adjusted. Selecting means for selecting and outputting one of the pixels according to the user's pixel size selection, and exposing the selected pixel for a time corresponding to the pulse width of the video data outputted from the selecting means. Characterized by comprising an engine for printing an image made of pixels. Pixel size controller. The pixel size adjusting device according to claim 1, wherein the pulse width adjusting means extends the pulse width of the video data by a predetermined multiple of the transmission clock signal period. In an electrophotographic developing system printer, video generating means for generating a transmission clock signal having a period corresponding to a set resolution and video data in which pulses corresponding to each pixel of an image appear in synchronization with the transmission clock signal. First delay means for delaying outputting said video data for one period of said transmission clock signal, and second delaying means for delaying outputting delayed video data of said first delaying means for one period of said transmission clock signal. Means for logically multiplying the video data of the video data generating means and the delayed video data of the first delay means, the video data of the video data generating means and the delayed video data of the second delay means. A second logical gate to multiply, the video data generating means and the first and second logical gates A selection means for selecting and outputting any one of the output video data corresponding to the pixel size selection of the user, and exposing the video data for a time corresponding to the pulse width of the video data output from the selecting means. And an engine for printing an image composed of pixels of a size corresponding to the width. 4. The pixel size adjusting device according to claim 3, wherein the first and second delay means are latch circuits for respectively latching and delaying input data by the transmission clock signal.