JPH07121592B2 - Image forming apparatus and control method thereof - Google Patents

Description

The present invention relates to an image forming apparatus and a control method thereof, and more specifically, an image forming apparatus and an image forming apparatus for recording an image based on print data from a host apparatus on a predetermined recording medium. It relates to a control method.

[Prior Art] As a device of this type, there is a printing device called a page printer.

This printing device is configured to print with high definition printing information in which characters and images created by image editing by recent desktop publishing are integrated.

In addition, as for the text data, font data having different numbers of constituent dots are provided in advance, and it is possible to print them in combination.

[Problems to be Solved by the Invention] By the way, in the print data output from the host or the like, there is an instruction to print at, for example, 12 points, 10 points, or 6 points. That is, the size of characters included in the same page is not always constant.

Therefore, when printing a small character, for example, when printing a complicated character at 6 points, it is necessary to print with a font pattern with a small number of constituent dots. There was a problem that the quality deteriorated.

The present invention has been made in view of such problems, using the function of variable resolution, even when recording a character of a relatively small size, the character is not crushed,
An object of the present invention is to provide an image forming apparatus and a control method thereof that can output characters of an intended size in high quality.

[Means for Solving the Problem] In order to solve this problem, for example, an image forming apparatus of the present invention has the following configuration. That is, the image forming apparatus has a variable resolution and forms a visible image on a predetermined recording medium on the basis of print data sent from a higher-level device, and stores the information indicating the resolution. Means, control means for controlling access to the font memory for generating a character symbol to be output based on the instruction information stored in the storage means, and control for accessing the font memory by the control means As a result, the character / symbol pattern having a number of dots larger than the number of dots forming the pattern in the case of outputting the character / symbol in the low resolution and having the same size as the output in the low resolution is output in the high resolution. And output control means.

[Operation] In the configuration of the present invention, the control unit accesses the font memory based on the information indicating the resolution stored in the storage unit. The output control means is configured with a number of dots that is larger than the number of dots that form a pattern for outputting a character symbol with low resolution, and the character symbol pattern with the same size as when outputting at the low resolution Output at the resolution.

Embodiments Embodiments according to the present invention will be described in detail below with reference to the accompanying drawings.

<Description of Device Configuration (FIG. 1), FIG. 2)> FIG. 1 shows a schematic configuration of the laser beam printer in the embodiment.

In the figure, 1 is an interface, which is print information (image data, text data, print control parameters, font type for text data, font size, typeface, image dot density code for image data, etc.) processed by a host computer (not shown). ) To receive. A page buffer memory 2 stores print information received via the interface 1 and edits a page while analyzing a code. A work memory 3 stores print control parameters of the printing unit 7 (details will be described later) and the like. Four
Is a font memory, which stores font data having different numbers of constituent dots, for example, for each size and typeface. A bit map memory 5 stores the dot image to be transferred to the printing unit 7. A parallel-serial converter 6 converts parallel data read from the bit map memory 5 into serial data and transfers the serial data to the printing unit 7. A pulse generator 8 generates an image clock corresponding to the set resolution (dot density) and changes the frequency of the image clock transferred to the parallel-serial converter 6 to change the frequency of the main scanning direction. The dot density can be changed (details will be described later).

Reference numeral 9 denotes an MPU, which comprehensively controls page editing and printing processing based on a control program stored in an internal program memory 9a (including a control procedure shown in FIG. 3 described later).
A scanner driver 10 drives a scanner motor (described later) that constitutes the beam scanning system in this embodiment based on speed data corresponding to the resolution set by the MPU 9.

Although the details will be described later, a reference character size S ₀ described later is stored and held in the program memory 9a.

The MPU 9 also functions as a character size detecting means, a reference character size latching means, a character size comparing means, and a density setting means in this embodiment, and image data and text data are page-edited with respect to the page buffer 2 serving as a page memory. Then, the size of the character with respect to the text data edited in the page buffer 2 is detected, the size of the character is compared with the reference character size S ₀ stored in advance, and the dot density for the output page is determined based on this determination result. ,
The dot density designation information is written in the work memory 3. Then, both the image data and the text data are printed by the printing unit 7 according to the density thereof (by controlling the pulse generator 8 and the scanner driver 10).

A specific configuration of the printing unit 7 is shown in FIG. The embodiment shows the case of an optical printer that forms an image by exposing and scanning a laser beam on a photoconductor.

In the figure, reference numeral 11 denotes a laser driver, which emits a laser according to an image signal (video signal) output from the parallel-serial converter 6.
Turn 12 ON / OFF (turn on / off laser light generation).

Reference numeral 13 denotes a scanner motor for rotating the polygon mirror 14, which rotates its drive shaft at a rotation speed corresponding to a value set in the scanner driver 10. Reference numeral 15 is a photoconductor that rotates at a constant speed by a drive motor (not shown).
The laser beam reflected by one side surface of the polygon mirror 14 is swept in the axial direction of 15 to form an electrostatic latent image. After that, image formation is performed according to a known electrophotographic method.

Further, in the present embodiment, the dot density at the time of printing is changed, but since the rotation speed of the photoconductor 15 is kept constant in the sub-scanning direction, the rotation number R of the scanner motor 13 and the image input to the laser driver 11 are changed. It is controlled by the frequency f of the signal (frequency of the image clock).

<Description of Principle> The operation principle of the printing apparatus according to the embodiment having the above-described configuration will be described below.

Here, assume a printing apparatus having a printing dot density of 240 dpi. At this time, when printing a 12-point character and a 6-point character, it is necessary to equip the apparatus with a 40 × 40 dot character pattern and a 20 × 20 dot character font pattern.

However, when printing complicated characters at 12 points and 6
Comparing with the case of printing by points, the latter is inferior in quality and looks crushed. In this embodiment,
Even when printing 6-point characters, a 40 × 40 dot character pattern is used. However, simply
If you print based on a 40 x 40 dot character pattern, 12 point characters will be printed, so double the print dot density in this case to 480 dpi for printing. As a result, small characters can be printed with high quality. Specifically, the pulse generator 8 and the scan driver 10
This is achieved by controlling the data set in.

However, since the rotation speed of the photoconductor 15 in the embodiment is fixed, when the printing dot density D _{H of} 240 dpi, the rotation speed R of the polygon mirror 14 and the video clock f are 480 dp.
The i, 300dpi is as follows.

When D _H = 480 dpi, polygon mirror 14 rotation speed = R × 2 video clock = f × 4, and when D _H = 300 dpi, polygon mirror 14 rotation speed = R × 5/4 video clock = f It becomes × 25/16.

It should be noted that if the print dot density is changed from 240 dpi to 480 dpi, it seems that the rotation speed of the polygon mirror 14 should be halved, but with this, the dot density in the sub-scanning direction is halved. I will end up. Therefore, the rotation speed of the polygon mirror is doubled and the video clock is increased four times to obtain a print dot density of 480 dpi in the main scanning direction and the sub scanning direction.

By the way, the printing density when obtaining a 6-point character with a character pattern of 40 × 40 dots can be calculated by the following formula.

That is, Therefore, X = 480, that is, 480 dpi.

<Description of Operation Outline> An operation outline of the present embodiment will be described below based on the principle described above.

It was explained earlier that the MPU9 controls the sequence of the input data analysis and control unit. Data input from the outside is stored in the page buffer 2 via the interface 1. The MPU9 analyzes various commands included in the input data and restores them in the page buffer 2 while reconstructing them as a page buffer. At the same time, various parameters such as the page number and the start address of the page buffer 2 are stored in the work memory 3.

Then, the character size in the data input at this time is detected, and as a result of comparison and determination with the reference character size S ₀ , if the character size is equal to or smaller than the reference character size, it is stored in a predetermined address in the work memory 3. Set the high-density flag provided to "1". If it is larger than the reference character size, nothing is done and the next character size comparison process is executed.
It should be noted that the reference character size is provided to represent the boundary where characters appear to be crushed when the size is smaller than the reference character size, and is not an absolute numerical value, so it is not clarified here.

Now, after comparing the data for one page, the high density flag is checked, and if it is set to "1", the dot density is D _H , and the scanning speed corresponding to it (polygon The rotation speed of the mirror) is R _H , the video clock f _H , and when the flag is “0”, D _L , R _L , and f _L are stored in the work memory 3, respectively.

Regarding the dot density D, the scanner motor speed R, and the video clock f, when the dot density D changes from D1 to DN, the scanner motor speed R and the video clock f are R1 to RN, f1.
It is defined as ~ fN.

Next, read sequentially from the top of the page, and the font memory 4
Is accessed to be converted into dot data and expanded in the bit map memory 5. At this time, since the dot density D is specified in the work memory 3, the font corresponding to the dot density D is selected from the font memory 4 and accessed.

When the development of the character pattern for one page is completed, the scanning speed R and the video clock f are read from the work memory 3, the rotation speed R of the polygon mirror is sent to the scanning driver 10, and the video clock f is sent to the pulse generator. 8 to specify the print density of the printing unit 7.

As described above, the scanner driver 10 controls the scanner motor 13 so that the rotation speed becomes stable at the set polygon mirror rotation speed R, and when the ready state is reached, a signal to that effect is output to the MPU 9. To do. When the video clock f is input, the pulse generator 9 outputs the clock to the parallel-serial converter 6 as a video clock f.

Next, the MPU 9 confirms that the scan driver 10 is in the ready state, and then sequentially reads the data from the bit map memory 5 and outputs it to the parallel-serial converter 6. The parallel-serial converter 6 converts the parallel dot data into serial data according to the clock from the pulse generator 8 and outputs the serial data as a video signal to the printing unit 7 for printing processing.

If the MPU 9 is high-speed and has a sufficient function, the next print information is received from the external controller in parallel with the data transfer to the printing unit 7, expanded to the page buffer 2 and further to the bit map memory 5. It is also possible to execute the expansion processing of.

<Description of Processing Procedure (FIG. 3)> Next, a control processing procedure of the MPU 9 of the embodiment will be described with reference to FIG.

First, in step S1, it is determined whether the input data is a printing parameter, and if YES, the process proceeds to step S2 and the parameter is stored in the work memory. If the determination in step S1 is NO ", that is, if the input data is determined to be character data (character code), the process proceeds to the next step S3, and the character is the standard character size S ₀ or less. If it is determined that the character size is equal to or smaller than the reference character size, the process proceeds to step S4, and the high density flag provided at the predetermined address position of the work area 3 is set to "1". When the determination in step S3 is NO, or after the processing in step S4 is executed, the character data is stored in the page buffer 2 in step S5.
Until it is determined in S6 that the data reception for one page has been completed, the above-described processing from step S1 is repeated.

When the data for one page is stored in the page buffer, the stored various data are reconstructed as page data while being analyzed in step S7, and the page number and the start address of the page buffer are stored in the work memory.
Then, in step S8, it is determined whether the high density flag is "1". And if YES, in step S10,
The dot density D _H , the scanning speed (rotation speed of the polygon mirror) R _H , and the video clock f _H corresponding thereto are stored in the work memory 3, and if NO, the process proceeds to step S9, where the dot density D _L and the corresponding The scan speed R _L and the video clock f _L are stored in the work memory 3. Next, in step S11, the work memory 3 is accessed to read the start address and print dot density of the page buffer 3 corresponding to the page. Thus, for example, it is determined whether the N.times.N dot font pattern is used for a 6-point character and the M.times.M dot font pattern is used for a 12-point character. Then, in step S12, the data is read from the beginning of the page buffer 2 and the font memory 4 is accessed to generate the corresponding dot data, which is expanded in the bit map memory 5. If the input data is image data, it is directly expanded in the bit map memory 5. Thus
The processing in step S12 is repeated until it is determined in step S13 that the development of the character data and the character pattern corresponding to the print dot density has been completed.

When the pattern development for one page is completed, the process proceeds to step S14 to set the scanner rotational speed R previously determined to the scanner driver 10 and the video clock f to the pulse generator 8 respectively. Then, when it is determined in step S15 that the printing unit 7 is in the standby state, step S16
Then, the contents of the bit map memory 5 are read, sequentially output to the parallel-to-serial conversion record, and the printing process is executed. If it is determined in step S17 that the data output for one page has been completed, the process proceeds to step S18, and it is determined whether or not the page printing for the set number of copies has been completed. If NO, the process proceeds to step S11. Return. If YES, the process proceeds to step S19, the high density flag is cleared to "0", and the process returns to the main routine (not shown).

As described above, according to the present exemplary embodiment, it is possible to print with high quality even a character having a reference character size or less, that is, a character that may be crushed when it is smaller than the reference character size.

Therefore, when printing with the reference character, since it is printed at the normal resolution, the area in which the character pattern is developed (dot space for one page in the embodiment) is smaller than the area when printing at high resolution. The character pattern can be expanded at high speed, and the character pattern expansion process ends accordingly, and as a result, the printing process can be speeded up.

On the other hand, when a small character is printed, the area for expanding the character pattern is widened, and the expansion processing takes time accordingly, but high-quality printing can be maintained.

In the above-mentioned embodiment, the case where the printing mechanism for forming the laser beam modulated by the polygon mirror 14 rotated by the scanner motor 13 on the basis of the image signal is formed on the photoconductor 15 has been described as an example. The same can be applied to an optical printer using the. That is, since in an LED printer using the LED array, thereby arranging the LED at intervals corresponding to dots density in the main scanning direction, for example, dots density D ₁
When to D ₃ required, three types of LED array placed around the photoreceptor, to change the main scanning direction of dots density by selecting them appropriately. Further, in the sub-scanning direction, it is achieved by controlling the time interval (determined by the rotation speed and the dot density of the photoconductor) for lighting the LED array of one line.

In the main scanning direction, the data read from the bit map memory 4 is sequentially latched to a register corresponding to an element for one line of the LED array, instead of converting the video signal to a serial signal, and one line is completed. At that point, the LED array will be turned on. Therefore,
It is necessary to transfer the data for one line to the one-line LED array described above and terminate the process.

In the above example, the characters of text data were explained,
When the image data is included in the same page and the dot density determined by the size of the character and the dot density of the image data are different, the density conversion of the image data is performed according to the dot density of the character. Then you can develop it into a bite map.

Further, in the above example, a plurality of font memories having different dot densities are used for description, but if outline fonts (vector fonts), which have been attracting attention in recent years, are used, only one font type is required (memory capacity can be suppressed. Therefore, it is not always necessary to store a plurality of dot pattern font patterns.

In the embodiment, the reference character size S ₀ is fixed and explained, but it may be changed. For example, it may be freely changed by a control command to that effect from the host, or may be set from the scanning panel of the printing apparatus itself.

[Effects of the Invention] As described above, according to the present invention, the function of varying the resolution is used, and even when storing a character of a relatively small size, the character is not crushed and is intended. It is possible to output high-quality characters in size.

[Brief description of drawings]

FIG. 1 is a block diagram of a laser beam printer in this embodiment, FIG. 2 is a diagram showing an outline of the construction of a printing unit in this embodiment, and FIG. 3 is a flow chart showing the printing processing procedure in this embodiment. In the figure, 1 ... interface, 2 ... page buffer,
3 ... Work memory, 4 ... Font memory, 5 ... Bit map memory, 6 ... Parallel-serial converter, 7
...... Printer, 8 ...... Pulse generator, 9 ...... MPU, 9
a: program memory, 10: scan driver.

Continuation of the front page (56) Reference JP-A 63-235986 (JP, A) JP-A 60-75865 (JP, A) JP-A 63-30932 (JP, A)

Claims (4)

[Claims] 1. An image forming apparatus, which has a variable resolution and which forms a visible image on a predetermined recording medium based on print data sent from a higher-level apparatus, wherein information indicating the resolution is provided. Storage means for storing; control means for controlling access to the font memory for generating a character symbol to be output based on the instruction information stored in the storage means; and access to the font memory by the control means. By controlling the number of dots that is larger than the number of dots that form the pattern when outputting a character symbol with low resolution, and the character symbol pattern having the same size as that at the time of outputting at the low resolution And an output control unit for outputting the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the font memory stores a vector font. 3. A method of controlling an image forming apparatus, wherein the resolution is variable, and a visible image is formed on a predetermined recording medium based on print data sent from a higher-level apparatus. A step of storing information to be stored, a control step of controlling access to a font memory for generating a character symbol to be output based on the instruction information stored in the storage step, and the font by the control step. By controlling the access to the memory, the character / symbol pattern having the same number of dots as the number of dots forming the pattern in the case of outputting the character / symbol at the low resolution and having the same size as the output at the low resolution is displayed. And an output control step of outputting at a high resolution. 4. The method of controlling an image forming apparatus according to claim 3, wherein the font memory stores a vector font.