JPH04320862A - Printing image quality improvement method - Google Patents

Abstract

PURPOSE:To enable an oblique line near a lateral line or a vertical line to be expressed by a smooth line with a printer which expresses an image by a set of dots such as a wire dot printer, a laser printer, etc. CONSTITUTION:The title system is so constructed that a dot can be printed further at a position shifted vertically and laterally by each half dot width other than lattice like printing positions of the dot, and whether the dot is printed or not can be indicated for each dot irrespective of printing of an neighboring dot. Thereby, since the printing position of the dot can be indicated by a half dot unit, even though an oblique line can be drawn by the same smoothness as that where two times dot density are taken vertically and laterally (i.e., 4 times bit map memory), the bit map memory can be realized with two times.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is capable of producing images (characters,
The present invention relates to a method for improving the image quality of printing in a printing device that expresses graphics, images, etc.

0002

[Prior Art] Printing devices that express images by printing or not printing grid-like dots (main dots) can express horizontal and vertical lines as smooth lines, but diagonal lines can be expressed as smooth lines. could not. The line at this time is shown in FIG.

For this reason, as described in Japanese Patent Laid-Open No. 165865/1983, it is possible to print dots (interpolation dots) even at positions shifted by half a dot width in the vertical and horizontal directions. It has been improved so that even diagonal lines can be expressed as smooth lines by using a method that prints interpolated dots only when dots are printed. In this method, whether or not to print on an interpolation dot is determined depending on the presence or absence of printing on surrounding main dots, so it is possible to improve the image quality of printing without increasing the amount of data to be handled. The line at this time is shown in FIG.

0004

[Problem to be Solved by the Invention] The above publication discloses that the angle 45
A diagonal line that is close to 100 degrees can be expressed as a smooth line, but a diagonal line that is close to a horizontal or vertical line cannot be expressed as a smooth line because the resolution of the interpolation dots cannot be fully utilized.

An object of the present invention is to make it possible to express a diagonal line close to a horizontal line or a vertical line as a smooth line by taking advantage of the resolution of interpolation dots.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a printing device capable of printing on main dots and interpolation dots is used, and whether or not to print on main dots or interpolation dots is independent of whether surrounding dots are printed or not. This allows specification for each individual dot.

Therefore, since it has not only a bitmap memory for storing print information corresponding to the main dots but also a bitmap memory for storing print information corresponding to interpolation dots, the bitmap memory is twice as large as that in the above publication. Requires.

[0008]

[Operation] Dot printing can be specified independently for main dots or interpolation dots, so diagonal lines that shift in half-dot units can be drawn, and overall smoothness can be expressed instead of local smoothness. The line at this time is shown in FIG.

[0009]

[Embodiment] An embodiment of the present invention will be described below in Figs. 1, 4, and 5.
, will be explained with reference to FIG.

FIG. 4 shows a block diagram of the printing apparatus. The host device 4 sends character data such as the size of characters to be printed, character codes, graphic data such as figure and position information, image data such as image and position information, density information, and control codes necessary for printing to the printing device. Transfer to 1. The data such as character, graphic, image data and control codes are transferred to the bus 12 via the host interface 3, and the microprocessor 2 is transferred to the program ROM 7.
The character, figure, image data and control code are interpreted and processed by a program stored in the computer.

The RAM 5 is a memory used by the microprocessor 2 to temporarily store data necessary for processing. The character pattern memory 6 is a memory in which coordinate data indicating the shape of the outline of a character to be printed is stored. The bitmap memory 9 is a memory that stores dot data corresponding to the position of the paper to be printed, and the character pattern data stored in the character pattern memory 6 is processed by the microprocessor 2 according to the algorithm stored in the program ROM 7. Store the converted dot data, or if data for printing a figure is transferred from the host device 4, store the data converted into dots corresponding to the figure, or store the image data sent from the host device 4. used to remember. The print control circuit 10 controls reading out the dot data stored in the bitmap memory 9 at a timing synchronized with the printing by the printer engine 11. The engine interface 8 is a circuit for transferring dot data output from the bitmap memory 9 to the printer engine 11 or for receiving information indicating the status of the printer engine 11 from the microprocessor 2.

FIG. 5 shows the printing paper 22 and printer engine 1.
1 shows the relationship between the main scanning synchronization signal 20 outputted from the bitmap memory 9 and the clock signal 21 used to read dot data stored in the bitmap memory 9. The main scanning synchronization signal 20 is a signal obtained by converting a part of the laser beam being scanned in the printer engine 11 into an electrical signal by a light receiving element such as a photodiode, and
This is a signal that serves as a reference for the writing start position in 2. The phase of the clock signal 21 is synchronized with the rising edge of the main scanning synchronization signal 20, and is used to read data stored in the bitmap memory 9. 1 of clock signal 21
The period corresponds to the length of one dot printed on the printing paper 22 in the main scanning direction. One period is determined by the scanning speed of the laser, and is set to match the length of the dot in the sub-scanning direction. On the other hand, the laser scans once every time the printing paper is fed for half a dot in the sub-scanning direction, and scans twice for one dot.

FIG. 6 shows an example of a circuit for creating a clock signal 21 synchronized with the main scanning synchronization signal 20 shown in FIG. 5, and is a part of the print control circuit 10. The oscillator 31 is an oscillator that oscillates at a frequency higher than the frequency of the clock signal 21, for example eight times, and the frequency is divided by the frequency divider 32 to obtain the clock signal 21. Here, the main scanning synchronizing signal 20 is connected to the reset terminal of the flip-flop of the frequency divider 32, and each time the main scanning synchronizing signal 20 is input, the flip-flop is reset at a rising edge and the phases are synchronized. Further, the signal delay circuit 33 is a circuit that delays the clock signal 21 by half a dot, and generates the delayed clock signal 23 shown in FIG. The selector 34 is a circuit that selects the clock signal 21 or the delayed clock signal 23 depending on the reading location of the bitmap memory.

[0014] Hereinafter, specific operations will be explained using an example of printing a figure as shown in Fig. 1. Host device 4
sends graphic data and control codes to the host interface 3, and the microprocessor 2 sends the program ROM 7
The graphic data and control code are interpreted and processed by a program stored in the computer, and information corresponding to the graphic is drawn in the bitmap memory 9. After the drawing is completed, the microprocessor 2 issues a print start request to the printer engine 11 via the engine interface 8. Printer engine 11 sends main scanning synchronization signal 20 to engine interface 8 . The print control circuit 10 receives this main scanning synchronization signal 20 and generates a clock signal 21 based on it. Here, when printing grid-like dots (main dots), dot data is read out in synchronization with the clock signal 21, but dots (interpolated When printing dots), the dot data is read out using the delayed clock signal 23 delayed by half a dot from the signal delay circuit 33. The printing paper is fed half a dot in the sub-scanning direction while a line of main dots is being printed, and then a line of interpolation dots is printed. Thereby, the interpolation dots can be printed at positions shifted by half a dot width in the vertical and horizontal directions with respect to the main dots.

Printer engine 11 used in this embodiment
The following modifications can be made to the printer engine, which expresses images based only on whether or not the main dots are printed. First, while printing one line, the printing paper was fed by one dot width in the sub-scanning direction, but the paper was fed by half a dot width. The spot diameter is made smaller than before by taking into consideration the degree of overlap between the main dots and interpolation dots.

On the other hand, the printer engine used in the publication described in the prior art section has, in addition to the above modifications, a means for generating interpolated dots (a group of registers for storing the surrounding main dots of a certain interpolated dot, a register group for storing surrounding main dots, A circuit that generates interpolated dots based on the data, a line buffer that stores the generated interpolated dots, etc.) is required, and there are many points that need to be modified. According to this embodiment, a conventional printer engine can be slightly modified without requiring a special printer engine;
Also, when printing lines of interpolated dots, the clock signal 21 is delayed by half a dot to read out the dot data, and by adding a circuit that reads the dot data and doubling the bitmap memory capacity, it is possible to print diagonal lines similar to horizontal or vertical lines. Even in the case of , the resolution of interpolation dots can be utilized to express smooth lines.

[0017]

[Effects of the Invention] According to the present invention, since the dot printing position can be specified in half-dot units, the dot density is twice as smooth both vertically and horizontally (i.e., four times as large as the bitmap memory). Although it is possible to draw a diagonal line with , the bitmap memory can be doubled (the bitmap memory corresponding to the main dots and the bitmap memory corresponding to the interpolation dots).

[Brief explanation of drawings]

FIG. 1 is a diagram when lines are drawn using the method according to the present invention.

FIG. 2 is a diagram when a line is drawn using only main dots.

FIG. 3 is a diagram when lines are drawn using the method disclosed in Japanese Patent Application Laid-Open No. 60-165865.

FIG. 4 is a block diagram of a printing device according to an embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between printing paper, main scanning synchronization signals, and clock signals.

FIG. 6 is a diagram showing an example of a circuit for creating a clock signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Printing device, 2...Microprocessor, 3...Host interface, 4...Host device, 5...RAM, 6...Character pattern memory, 7...Program ROM, 8...Engine interface, 9...Bitmap memory, 10...
Print control circuit, 11... printer engine, 12... bus,
20... Main scanning synchronization signal, 21... Clock signal, 22... Printing paper, 23... Delayed clock signal, 31... Transmitter, 32
... Frequency divider, 33... Signal delay circuit, 34... Selector.

Claims (1)

[Claims] Claim 1: In a printing device where the dots are arranged in a grid pattern and an image is expressed by whether or not the dots are printed, it is possible to further print dots at positions shifted by half a dot width in the vertical and horizontal directions, and to print the dots. A printing image quality improvement method characterized in that whether to print or not can be specified for each individual dot regardless of whether surrounding dots are printed or not.