JP2002271622A - Printer and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an printer that can print out a medium tone image and a binary image for characters/a line drawing with quality which is respectively proper to the image, in spite of the simple constitution and can similarly print out even an intermingled image of them. SOLUTION: Upon the receipt of print data from a host computer, the printer discriminates whether a print object in the print data is a multivalued image or data intended as a binary image, such as characters. Then the images are respectively deployed in a multivalued image memory and a binary image memory reserved in a RAM 19. When the images by one page are deployed, a PWM circuit 23 applies PWM processing to the multivalued image data and a smoothing processing section 24 applies smoothing processing to smooth edges of the binary image. An ORing section 25 applies ORing operation to the signals respectively generated and a print section 17 prints out the resulting signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus and a control method therefor, and more particularly to a printing apparatus for printing out data output from a host device such as a host computer and a control method therefor.

[0002]

2. Description of the Related Art Host computers, in particular, recent GUs
In a personal computer equipped with the OS I, an application for creating a document in which a halftone image and a text are mixed can be executed and the document can be printed.

[0003] As for a printing apparatus, a typical one such as a laser beam printer has a high resolution, and the printing quality is becoming higher.

[0004]

Generally, a laser beam printer prints an image in a binary state, but when printing a gradation image such as a photographic image, the size of one dot is determined according to the density. This is achieved by expressing the light and shade by area gradation.

As a typical technique, pulse width modulation (Pu
lse Width Modulation = PWM). This PW
The M technique will be briefly described. A multi-value pixel (for example, 8 bits = 2 bits per pixel) supplied from a host computer or the like
(56 gradations) is modulated into a signal having a pulse width corresponding to the value, and laser light is emitted for a time corresponding to the pulse width. In the case of a laser beam printer, since a laser beam scans on a photosensitive drum at a predetermined speed, dots of an electrostatic latent image having a size depending on the light emission time are formed on the photosensitive drum, and finally the dot is formed. A dot having a size is formed.

In the case of a binary image (two types of maximum density and minimum density) such as characters and line drawings, if the printing resolution is high,
It is well known that edges are smoothed and higher quality output results can be obtained.

However, in the case of a halftone image of a photographic image, a resolution of about 300 dpi is sufficient for practical use. Therefore, even if printing is performed at a high resolution of 1200 dpi or the like as in a recent printer, it is impossible for human eyes to sense that the quality has been dramatically increased, and moreover, more memory is required, and the printing speed is reduced. Etc.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and enables printing of a halftone image and a binary image such as a character and line drawing with a quality suitable for each of them while having a simple configuration. It is an object of the present invention to provide a printing apparatus and a method of controlling the printing apparatus, which can realize this even when both are mixed.

[0009]

In order to solve such a problem, a printing apparatus according to the present invention has the following arrangement. That is, print data output from a higher-level device is received,
A printing device that prints a visible image on a recording medium based on the print data and outputs the data, analyzes the received print data, and outputs the data to be printed as a binary image or a halftone image. Determining means for determining whether there is any data, and developing means for developing binary image data in a binary image memory area and binary image data in a multivalued image memory area based on the determination result of the determining means A smoothing means for generating a binary signal obtained by smoothing an edge of the binary image developed in the binary image memory area, and a gradation value of the multilevel image developed in the multilevel image memory area And a pulse width modulation unit for generating a binary signal having a length corresponding to the signal, and a signal for combining the signals generated by the smoothing unit and the pulse width modulation unit, and printing a visible image based on the combined signal. Means Obtain.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the embodiment, an example in which the present invention is applied to a laser beam printer will be described. However, it goes without saying that the present invention may be applied to other printing methods such as an LED printer.

When printing is performed using the printer according to the embodiment, a corresponding printer driver (software) is installed in the host computer. The printer driver receives from the application running on the host computer via the OS, translates it into a printer language that can be interpreted by the printer,
Perform processing to return to. The OS performs a process of outputting the print data to the printer 1500.

For the sake of simplicity, the printer described below in the embodiment functions as having a recording resolution of 300 dpi when viewed from a host computer (printer driver), and the actual printer engine is 600 dpi. Recording resolution.

Accordingly, the printer 150 according to the embodiment is
0 is required to have a function of converting from 300 dpi to 600 dpi, and this conversion will be clarified below.

FIG. 1 is a structural sectional view of a printer according to the embodiment.

In FIG. 1, reference numeral 1500 denotes a printer main body, which inputs and stores print information (character codes and the like), form information, macro instructions, and the like supplied from an externally connected host computer, and , A corresponding character pattern, form pattern, or the like is created, and an image is formed on a recording medium such as a recording sheet.

Reference numeral 1501 denotes a switch for operation and an LCD.
An operation panel 1000 on which a display is arranged is a printer control unit for controlling the entire printer body 1500 and analyzing print data supplied from a host computer. The printer control unit 1000 mainly generates character patterns corresponding to character information, converts the generated character patterns into video signals, and outputs the video signals to the laser driver 1502. The laser driver 1502 is a circuit for driving the semiconductor laser 1503, and turns on / off a laser beam 1504 emitted from the semiconductor laser 1503 according to an input video signal.
Switch FF. The laser beam 1504 is applied to the rotary polygon mirror 15
At 05, scanning is performed on the electrostatic drum 1506 by swinging in the left-right direction. As a result, an electrostatic latent image is formed on the electrostatic drum 1506. The latent image is formed on the electrostatic drum 1506 by a developing unit 150
After being developed by 7, the image is transferred to recording paper.

A cut sheet is used as the recording paper. The cut sheet recording paper is stored in a paper cassette 1508 mounted on the printer 1500, and is taken into the apparatus by a paper feed roller 1509, transport rollers 1510 and transport rollers 1511. And supplied to the electrostatic drum 1506. The printer body 1500 has at least one or more card slots (not shown) so that an optional font card and a control card (emulation card) having a different language can be connected in addition to the built-in fonts.

FIG. 2 is a block diagram mainly showing the configuration of the printer control unit 1000 in the present embodiment.

In the printer 1500, reference numeral 12 denotes a CPU.
The print unit controls access to various devices connected to the system bus 15 based on a control program or the like stored in the program ROM of the ROM 13 or a control program or the like stored in the external memory 14. Printing unit 17 connected via interface 16
(A laser driver 1502 of the printer engine) to output an image signal as output information. This ROM 1
The program ROM 3 stores a control program of the CPU 12 (including a program corresponding to a flowchart described later). The font ROM of the ROM 13 stores font data and the like used when generating the output information, and is used on the host computer when the data ROM of the ROM 13 does not have the external memory 14 such as a hard disk. Information and the like are stored.

The host computer 3000 is connected to the input unit 18.
And print data (code data and image data) described in a printer-specific language. C
The PU 12 is capable of communicating with a host computer via the input unit 18 and is configured to be able to communicate information in the printer and the like to the host computer. 19
Is a RAM that functions as a main memory, a work area, and the like of the CPU 12, and is configured so that the memory capacity can be expanded by an optional RAM connected to an additional port (not shown).

The RAM 19 has an output information development area,
Used for environmental data storage area, NVRAM, etc. RA
For example, as shown in FIG. 5, the output information development area secured in M19 includes a halftone (multi-value) image frame memory 19a for developing a halftone image and a binary memory for developing a character or line drawing image. There is an image frame memory 19b. The halftone image frame memory 19a has, for example, 8 bits (256 gradations) per pixel, and the binary image frame memory 19b has 1 bit (binary) per pixel. Therefore, the latter has 1/8 the capacity of the former.

The ASIC 22 sequentially analyzes text information from a host computer stored in the RAM 19 and control circuits such as a memory controller such as the ROM 13 and the RAM 19, a DMA controller, an I / F controller, and the like, and, for example, character codes are stored in the font ROM data. Is developed into bitmap data, and is developed in the RAM 19 (bitmap memory). Hard disk (HD), I
The access to the external memory 14 such as a C card is controlled by the ASIC 22. The external memory 14 is connected as an option and stores font data, an emulation program, form data, and the like. Also, 1501
Is a switch and LC for operation on the operation panel described above.
A D display and the like are arranged.

The above-mentioned external memory is not limited to one, and at least one external memory is provided. In addition to the built-in fonts, an optional font card and a plurality of external memories storing programs for interpreting printer control languages of different languages can be connected. May be configured. Further, an NVRAM (not shown) may be provided to store the printer mode setting information from the operation panel 1501.

Reference numeral 23 denotes a multi-valued pixel data (300 dpi) represented by, for example, 8 bits per pixel, and a PWM-modulated signal (a signal corresponding to 300 dpi).
Is a PWM circuit. Although the PWM circuit itself is publicly known, it can be simply realized by the circuit configuration shown in FIG.

In the figure, reference numeral 60 denotes a D / A converter for converting digital data into an analog signal.
Reference numeral 22 denotes a halftone image frame memory 19 in the RAM 19.
The data (8 bits) of 300 dpi developed in a is received in synchronization with a clock clk (half the frequency of the clock when output to the printer engine), and is converted into an analog signal. Reference numeral 61 denotes a triangular wave generating circuit for generating an analog triangular wave signal.
Generates a square wave signal. 62 is a comparator, D /
The signal from the A converter 60 is compared with the signal from the triangular wave generation circuit 61, and the comparison result is output. Therefore,
The signal output from this comparator is a signal having a pulse width corresponding to the pixel value. The signal output from the comparator is supplied to the OR gate 25, and the carrier clock at this time is output at twice the frequency of the clock clk.

Since the printer engine is 600 dpi, the number of lines scanned by the laser beam is 300 dpi.
Is twice as large as In the embodiment, the PWM processing is performed by 300
Output is performed twice per line of dpi.

Returning to FIG. 2, reference numeral 24 denotes a smoothing processing unit for inputting 300 dpi binary pixels (character / line drawing pixels) and interpolating them to generate 600 dpi pixels. The processing content will be described with reference to FIG.

As described above, the printer according to the present embodiment is 300 when viewed from the host computer.
It looks like a printer with a recording resolution of dpi,
The printer engine unit has a 600 dpi engine. The data from the binary image frame memory 19b is one bit per pixel, and the resolution of the pixel is 300 dpi. Therefore, if the image is directly output to a 600 dpi printer engine, the size is reduced by half in both the vertical and horizontal directions (vertical and horizontal).

Therefore, in the main scanning direction, the input 300d
One pixel of pi is interpolated into two pixels of 600 dpi. In the sub-scanning direction, output is performed twice per line at 300 dpi to prevent the size from changing. However, in this state, the edge of the binary image is 300 dp.
Therefore, as shown in FIG. 7, the pixel of interest of the line of interest is generated and output by performing an interpolation process, as shown in FIG. The interpolation process is 300
It will be output twice for one line of dpi,
In the first case, a 600 dpi pixel is generated from the relationship between the previous line and the line of interest, and in the second time, a 600 dpi pixel is generated from the relationship between the line of interest and the next line (known BD). Just count the signals). The figure shows the interpolated pixels at the second output timing. It can be seen that the edges can be made smoother as shown. When this processing is performed, a signal indicating whether the interpolation is the first interpolation or the second interpolation for a 300 dpi line (1 bit is sufficient) and the sum of the corresponding binary pixel values of the two lines are performed. Those skilled in the art will understand that the present invention can be realized by a look-up table table that outputs one bit with respect to a three-bit input.

The PWM circuit 23 and the smoothing processing unit 2
4 is supplied to the OR unit 25.
The OR unit 25 calculates the logical sum of the two input signals and outputs the result to the printer engine (printing unit 17). FIG. 3 is an example of two input signals and a logical sum of the two signals.

Now, in the above configuration, an operation processing procedure (a program processed by the CPU 12) of the printer 1500 in the embodiment will be described with reference to a flowchart of FIG.

It is assumed that the input unit 18 has a reception buffer, and the received print data is sequentially stored in the reception buffer (the processed data is overwritten with the data received later).

First, in step S1, data is input from the reception buffer, and it is analyzed in step S2.
Determine the type. If it is determined that the command is a character code or a line drawing command, the process proceeds to step S3, where a character pattern (binary) is generated by referring to a font ROM or the like, and stored in the binary image frame memory 19b in the RAM 19. The image is developed at the position specified by the print control command, and the process returns to step S1.

If the received data is a multi-valued image (such as a photographic image), the multi-valued image is developed at the position specified by the control command in the multi-valued image frame memory 19a. Return to S1.

Hereinafter, this processing is repeated, and when a command indicating the page end is finally detected in step S2,
Since the image development processing for one page has been completed in the multi-valued image frame memory 19a and the binary image frame memory 19b, these two
Output of two memories. As a result, the multi-valued pixels developed in the multi-valued image frame memory 19a are subjected to PWM conversion by the PWM circuit 23, and are converted to the binary image frame memory 19a.
The binary pixel expanded to b is subjected to the smoothing process. Upon receiving these two signals, the OR unit 25 performs a logical OR operation and outputs the logical sum to the printer engine (printing unit 17).

As a result, the halftone image is substantially 300
Good tone reproduction is possible by performing image formation by the PWM conversion of dpi, and the edge of a binary image such as a character or a line drawing is subjected to a smoothing process to output a high-quality character or a line drawing without jaggies. become. Further, even if a binary image and a multi-valued image coexist, printing can be performed with optimal processing for each.

Although the OR unit 25 in FIG. 2 outputs a logical sum of the two signals, the image data of the character data is output when a multi-valued pixel exists (when the density is not 0). The bus 27 may be invalidated (in the case of the embodiment, it is assumed that “0” data is output from the smoothing processing unit 24, but it goes without saying that there is no problem if the bus is invalidated using another method. ). Conversely, when only the character data converted into image data is input to the printing unit 17, the image data bus 27 of the image data is invalidated (in the case of the present invention, as described above, the "0" data output from the PWM 23). However, there is no problem if the bus is invalidated by another method as described above.)

In the embodiment, the PWM circuit 23, the smoothing processing unit 24 and the OR
The part 25 is divided and described.
Needless to say, there is no problem even if it is built in the 22 or the like to form one block. In order to obtain PWM by digital processing, a clock having a frequency 256 times that of the input clock is prepared, and every time one pixel is input, a signal having a length corresponding to the value is output as high.

In the embodiment, a monochrome image of 8 bits per pixel has been described as an example of a halftone image. However, the present invention is not limited to this. In particular, when the present invention is applied to a color printer, a multi-tone color image can be recorded by allocating 8 bits to each of CMYK, which is a recording color component, and performing PWM modulation on each of them. It can also be output in 8 colors (including white).

Although the embodiment has been described with an example of a printer directly connected to a host computer, print data may be received from a plurality of host computers via a network or wirelessly and printed.

In the embodiment, the print data is 300d
Pi is intended to be data, and the engine section of the printer has been described as 600 dpi, but the present invention is not limited to these values.

[0042]

As described above, according to the present invention, it is possible to print a halftone image and a binary image such as a character line drawing with a quality suitable for each of them, while having a simple structure, and to mix each of them. This can be realized in the same manner.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a printer according to an embodiment.

FIG. 2 is a block diagram of a printer control unit and its periphery according to the embodiment;

FIG. 3 is a timing chart showing an output waveform of image data in the embodiment.

FIG. 4 is a flowchart illustrating an operation processing procedure of the printer according to the embodiment.

FIG. 5 is a diagram showing the contents of a RAM 19 in the embodiment.

FIG. 6 is a diagram showing a specific configuration of a PWM circuit 23 in the embodiment.

FIG. 7 is a diagram for explaining the operation content of a smoothing processing unit 24 in the embodiment.

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Claims (5)

[Claims] 1. A printing device that receives print data output from a higher-level device, prints a visible image on a recording medium based on the print data, and outputs the visible image. Determining means for determining whether the data to be printed out is a binary image or a halftone image; a binary image memory area for the binary image data based on a determination result of the determining means; Expanding means for expanding the multi-valued image data in the memory area for multi-valued image; smoothing means for generating a binary signal obtained by smoothing edges of the binary image expanded in the memory area for the binary image; A pulse width modulation means for generating a binary signal having a length corresponding to a gradation value of the multi-valued image developed in the multi-valued image memory area; and a pulse width modulation means for generating the binary signal. Signal And the printing apparatus characterized by comprising a printing means for printing a visible image based on the synthesized signal. 2. The printing method according to claim 1, wherein the print data is print data for a first resolution, and the printing unit prints at a second resolution higher than the first resolution.
A printing device according to claim 1. 3. The apparatus according to claim 2, wherein the smoothing means includes means for interpolating and generating a pixel value corresponding to the second resolution in accordance with the first and second resolution ratios.
A printing device according to claim 1. 4. The apparatus according to claim 1, wherein the determination unit determines whether there is halftone image data in the received print data or whether there is a command for drawing a character / line image. The printing device according to the above. 5. A control method for a printing apparatus, which receives print data output from a host device, prints a visible image on a recording medium based on the print data, and outputs the visible image. A determination step of analyzing and determining whether the data to be printed out is a binary image or a halftone image; and based on the determination result of the determination step, the binary image data A developing step of expanding the memory area and the multi-valued image data into a multi-valued image memory area; and a smoothing step of generating a binary signal obtained by smoothing edges of the binary image expanded in the binary image memory area. A pulse width modulation step of generating a binary signal having a length corresponding to a gradation value of the multi-valued image developed in the multi-valued image memory area; a smoothing step and the pulse width modulation step Generated by Combines the signals, the control method for a printing apparatus characterized by comprising a printing step of printing a visible image based on the synthesized signal.