JPH054381A - Image recording device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image recording apparatus for converting data of low print density into data corresponding to high print density and printing characters such as characters and symbols with high image quality. [Configuration] The conversion unit 20 provided in the image recording device is
Line memories 1 to 3 for storing data input from the drawing unit 13 via the OR gates 21, 22, and 23, and a selector for sequentially transferring the contents of the line memory 1 to the line memory 2 and the line memory 3. 24, a comparator 25 for comparing the dot pattern output from the line memories 1 to 3 with a pattern stored in advance in the pattern ROM, and a dot data pattern of 300 dpi based on the result of the comparison.
A pattern generator 27 for converting into a dot data pattern of 0 dpi, a data selector 28, a selector 24 for outputting the dot data of each row converted into a double linear density in two steps of an upper stage and a lower stage, It has a control unit 29 for controlling the data selector 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording device such as a laser printer.

[0002]

2. Description of the Related Art In recent years, laser printers have come to be widely used as output devices for computers due to their low noise and high image quality. Laser printers generally have a resolution of 300 dpi and a printing speed of 10 sheets / minute. On the other hand, recently, high image quality of a printer is desired, and a resolution of 600 dpi or higher is required.

[0003]

The dot data corresponding to the dot density (printing density) of 300 dpi is 600 dpi.
When printed with a printer with a print density of i, both vertical and horizontal directions are 1
It will be reduced to / 2. Also, if the number of dots is simply doubled in both the vertical and horizontal directions, the size will not be reduced to 1/2, but the jagged outline of the printed character is 30.
There is no improvement compared to the case of printing with a print density of 0 dpi.

Although high image quality can be achieved by printing bit data corresponding to a print density of 600 dpi at a print density of 600 dpi, the image memory capacity needs to be four times that of a conventional printer having a print density of 300 dpi. Therefore, not only is it expensive, but there is also the problem that conventional application software developed for a computer that outputs bit data corresponding to a printing density of 300 dpi to a printer cannot be used.

In order to deal with this, an apparatus for printing 300 dpi data at a pseudo print density of 600 dpi is described in US Pat. No. 4,847,641. In this device, when the dot pattern in the character to be printed matches the previously stored pattern, the spot size of the light beam is changed or the dot position is slightly moved (for example, 1/3 dot) in the main scanning direction. I am letting you. However, since this apparatus performs signal processing only in the main scanning direction, there is a problem that the image quality is not improved in the sub scanning direction.

The present invention has been made in view of the above problems, and by converting data corresponding to a low print density into data corresponding to a high print density, characters such as characters and symbols can be displayed with high quality. An object is to provide an image recording device capable of printing.

[0007]

An object of the present invention is an image recording apparatus for forming and recording an image with dots for each pixel, and means for receiving dot data having a first dot density, Means for converting the received dot data into dot data having a second dot density by replacing the dots of the pixel of interest with a plurality of dots having a pattern corresponding to the dot pattern of the area including the pixel of interest; And a means for forming an image in accordance with the generated dot data.

[0008]

When dot data having a dot density of 300 dpi is input, for example, a pixel area having a predetermined size, for example, 3
The type of dot pattern in the area of row × 3 columns is identified.
In accordance with this identification result, one dot of the pixel of interest located at the center of the area is replaced with, for example, four dots of 2 rows × 2 columns. By executing this operation for all the pixels, the dot data of 300 dpi is converted into the dot data of 600 dpi.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

In FIG. 2, 10 is a laser printer according to the present invention, and 30 is a host computer. The laser printer 10 includes a controller unit that processes data output from a host computer, and a base engine unit that prints characters and symbols on recording paper according to the data processed by the controller unit. The controller unit includes an interface unit 11 that takes in the dot data and code data of 300 dpi output from the host computer 30, an interpreter unit 12 that decodes the input dot data and code data, data output from the interpreter unit 12 and a memory unit. It is composed of a drawing unit 13 for comparing the font data stored in 14 to generate drawing data, and a conversion unit 20 for converting the data output from the drawing unit 13 into data corresponding to a print density of 600 dpi. It

The base engine unit is an optical system 15 for forming a latent image on the photosensitive drum by a laser beam based on the data output from the controller unit, a developing unit for adhering toner to the latent image and making it visible, and a residual unit. It is composed of a process system 16 including a cleaning unit for removing toner, a fixing system 18 for fixing the toner onto the recording paper, and a paper feeding system 19 for conveying the recording paper.

FIG. 1 is a block diagram showing the configuration of the conversion unit 20. As shown in FIG.
Line memories 1 to 3 for storing the data input via the R gates 21, 22, and 23, a selector 24 for sequentially transferring the contents of the line memory 1 to the line memory 2 and the line memory 3, and a line memory Comparator 25 for comparing the dot patterns output from 1 to 3 with the patterns stored in the pattern ROM in advance. 300 based on the comparison result.
A pattern generator 2 for converting a dot data pattern of dpi into a dot data pattern of 600 dpi
7. A data selector 28 for outputting the dot data of each row converted to the double linear density twice and outputting the dot data in the upper stage and the lower stage separately, and a control unit 29 for controlling the selector 24 and the data selector 28. FIG. 3 is a time chart showing the operation timing of the conversion unit 20. As shown in the figure, every time the horizontal synchronizing signal HSYNC is input to the control unit 29, that is, every two scan lines, a SELECT signal is sent from the control unit 29 to the selector 24.
The dot data DI stored in the line memory 1 is sequentially transferred to the line memory 2 and the line memory 3.

The comparator 25 has three rows from the line memories 1 to 3 ×
The dot patterns in the three rows of areas are read and compared with the patterns stored in the pattern ROM to identify the type of the read pattern. As shown in FIG. 4, the pattern generator 27 replaces one dot of the central pixel (target pixel) of the area with four dots according to the type of the identified pattern. The pattern generated by the pattern generator 27 is output via the data selector 28 as data for each scan, that is, as image output data D0 corresponding to a print density of 600 dpi.

FIG. 5A shows the printing result of the character "W" by the conventional printer having the printing density of 300 dpi, and FIG. 5B shows the printing result of the character "W" by the printer of this embodiment.
The dot data of dpi is converted into the dot data of 600 dpi, and the same character "W" is printed.
From these figures, it is understood that the image quality is greatly improved by converting the dot data of 300 dpi into the dot data of 600 dpi by the above processing.

Next, another configuration example of the conversion unit 20 is shown in FIG.
In the figure, 240 is a selector corresponding to the selector 24 in FIG. 1, 210 is a shift register for storing dots in a region of 9 columns × 7 rows, 220 is a FIFO (first in first out memory),
250 is a decision circuit having the functions of the pattern ROM 26, the comparison circuit 25 and the pattern generator 27 of FIG. 1, 280 is an output buffer corresponding to the data selector 28 of FIG.
This is a timing control unit corresponding to the control unit 29.

In order to convert the input data DI corresponding to 300 dpi into 600 dpi data, 600 dpi
It is necessary to adapt the two scans at 1 to the one scan at 300 dpi. Therefore, the image input data DI corresponding to the print density of 300 dpi is written in the FIFO 220 and the shift register 210 through the selector 240 only during odd-numbered line scanning in each scan at 600 dpi. During even line scanning, the data in the FIFO 220 is repeatedly output. That is, when scanning even lines, the FIF
One row (a1 to a7) of dot data is output from O220 to the selector 240. As a result, the contents of the shift register 210 are updated, and the target pixel is also sequentially shifted by one column.

As in the case of FIG. 1, one dot is divided into four dots by the decision circuit 250, and the four dot data indicating whether these dots are white or black are output to the output buffer. From 280, the upper two dot data and the lower two dot data are separately output during even line scanning and odd line scanning.

FIG. 7 is a diagram showing the contents of data stored in the shift register 210. The dot data a44 of the pixel of interest is converted by the determination circuit 250 into four dot data c1 to c4 having values corresponding to the contents of the dot data a10 to a88 of the peripheral pixels. As shown in FIG. 8, c1, c
2 is dot data of pixels on the left and right of the odd line, and c3 and c4 are dot data of pixels on the right and left of the even line, respectively.

FIG. 9 shows the circuit configuration of the determination circuit 250. As shown in the figure, the determination circuit 250 includes coincidence gates A1 to An and OR gates O1 to O4. Shift register 210
The dot data a10 to a88 in the inside are coincidence gates A1 to An.
Is input to each. Each match gate is provided with an inverter corresponding to each basic pattern on the upper side of FIGS. The dot data representing white is inverted by the inverter and input to the coincidence gate.

FIG. 11 is a conversion pattern corresponding to a basic pattern for diagonal line processing, FIG. 12 is a conversion pattern corresponding to a basic pattern for singular point processing, and FIG. 13 is a conversion pattern corresponding to a basic pattern for curve processing. FIG. 14 shows a basic pattern for notch / acute angle processing and a corresponding conversion pattern, respectively, and the number of matching gates is equal to the number of basic patterns. When the pattern of the input dot data matches one of the basic patterns, the dot data a of the pixel of interest
44 is converted into four dot data having a predetermined value and is output from one of the coincidence gates. For example, when the input pattern matches the basic pattern unique to the match gate A1, the data c11, c21, c31, c41 is output from the match gate A1.

The OR gate O1 has data c11, c12, ...
The logical sum of c1n is output as dot data c1, the OR gate O2 outputs the logical sum of data c21, c22, ..., C2n as dot data c2, and the OR gate O3 is output as data c.
, C3n are output as dot data c3, and the OR gate O4 outputs the data c41, c42, ..., C4n.
Is output as dot data c4. The output buffer 280 outputs the data c1 to c output from the determination circuit 250.
4 is output to the base engine unit in synchronization with the timing signal shown in FIG. For example, the timing signals VEO and HE
When all O are "1", the divided dot c1 on the left side of the odd line is output.

15 to 18 are logical expressions showing the operation of determining the divided dot data c1 to c4 from the dot data of the peripheral pixels of the judgment circuit 250. In the figure, the symbol * is a logical product, the symbol /
Indicates inversion, and the symbol + indicates logical sum.

[0023]

According to the image recording apparatus of the present invention, the dot of the target pixel is replaced with a plurality of dots having a pattern corresponding to the dot pattern of the area including the target pixel, so that the dot data of low print density can be printed highly. Since it is configured to convert the density dot data, the image quality can be improved with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an example of a conversion unit of a laser printer according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of the laser printer of FIG.

FIG. 3 is a time chart of the conversion unit in FIG.

FIG. 4 is an explanatory diagram of a pattern generation operation of the conversion unit in FIG.

FIG. 5 is a diagram showing print results of a conventional printer and a printer according to the present invention.

FIG. 6 is a block diagram showing the configuration of another example of the conversion unit of the laser printer according to the present invention.

7 is an explanatory diagram of contents of a shift register of the conversion unit in FIG.

FIG. 8 is an explanatory diagram of divided dots.

9 is a circuit diagram of a determination circuit of the conversion unit in FIG.

10 is an explanatory diagram of a timing signal supplied to the output buffer of the conversion unit in FIG.

FIG. 11 is a diagram showing a conversion pattern corresponding to a basic pattern for diagonal line processing.

FIG. 12 is a diagram showing a basic pattern for singular point processing and a corresponding conversion pattern.

FIG. 13 is a diagram showing a conversion pattern corresponding to a basic pattern for curve processing.

FIG. 14 is a diagram showing a conversion pattern corresponding to a basic pattern for cutting and acute angle processing.

15 is a diagram showing a logical expression representing an operation of dividing a dot of a target pixel from dot data of peripheral pixels of the determination circuit of FIG.

16 is a diagram showing a logical expression representing an operation of dividing a dot of a target pixel from dot data of peripheral pixels of the determination circuit of FIG.

17 is a diagram showing a logical expression representing an operation of dividing a dot of a target pixel from dot data of peripheral pixels of the determination circuit of FIG.

18 is a diagram showing a logical expression representing an operation of dividing a dot of a target pixel from dot data of peripheral pixels of the determination circuit of FIG.

[Explanation of symbols]

 10 Laser printer 20 Converter 21 to 23 OR gate 24 Selector 25 Comparator 26 Pattern ROM 27 Pattern generator 28 Data selector 29 Control unit 210 Shift register 220 FIFO 240 Selector 250 Judgment circuit 280 Output buffer 290 Timing control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H04N 1/387 101 8839-5C (72) Inventor Yukiko Kamei 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka No. Sharp Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. An image recording apparatus for forming and recording an image with dots for each pixel, comprising means for receiving dot data having a first dot density, and dots for a target pixel. Means for converting the received dot data to dot data having a second dot density by replacing the dot data with a plurality of dots having a pattern corresponding to the dot pattern of the region including the target pixel; and the converted dot data. An image recording apparatus, which is provided with means for forming an image in response thereto.