JPS60182863A - Multi-gradation recorder - Google Patents

Abstract

PURPOSE:To attain many multi-gradation expressions even with the picture element matrix of identical size by recording again the new 2nd dot group in the occupied region of the 1st dot group recorded on a recording medium. CONSTITUTION:A motor 1 drives a wire 7 to the left and right so as to scan a carriage fixed thereto left and right. A platen 3 is driven by a pulse motor 2 via gear 9 and feeds a recording paper sheet 5, and when a signal for one row's share is recorded, the paper feed for one row's share is not immediately conducted, and the platen 3 is controlled for paper feed by, e.g., 1/3 or 1/2 of one dot's share. As a result, a dot shifted longitudinally by 1/3 or 1/2 dot's share is recorded duplicatedly on each dot of a line recorded once. Further, the double dot recording shifted laterally is attained by giving a slight delay to the print timing of the return of the carriage.

Description

[Detailed Description of the Invention] [Technical Field] The present invention records dots at predetermined dot positions,
The present invention relates to a multi-gradation recording device that records images having shading.

[Prior Art] Conventionally, it has been widely known that pixels of different sizes are used to express the density of monochrome images or color images. In addition, when achieving such shading using a recording device that cannot change the diameter of the recording dots, the recording dots e per unit area can be changed to obtain the same effect as when changing the dot diameter. There is a known method of obtaining This method is effective when the density of recording dots is increased, although the range of variation in shading is much larger than the method of changing the dot diameter.

In this method of changing the recording dot density, the size of the predetermined matrix corresponds to the maximum dot diameter, and the larger the matrix size, the greater the number of gradations that can be expressed. However, on the contrary,
The disadvantage is that the area occupied by one pixel also increases. Therefore, this method uses an optical illusion to create the appearance of shading, but although it depends on the viewing distance of the recorded image, a high pixel density is required to reproduce a good quality image. Ru.

The conventional problems mentioned above are explained in more detail as follows.

Assuming a matrix including 2×2 dots as shown in FIG. 1, five gradations of light and shade can be expressed using zero dots to four dots. The larger this assumed matrix is, the more gradations can be expressed. For example, an 8×8 matrix can express 65 types of gradations. but,
On the other hand, when expressing a low density, the dot spacing becomes large, so unless the pixel spacing is quite small, the image quality will not improve much, although more gradations can be obtained.

FIG. 2 is a schematic diagram illustrating a method of comparing an input image signal (A) with shading with a threshold matrix pattern and converting shading into density gradation. In other words, the input image (a)
A 2×2 threshold matrix pattern (b) (darkness values for each gradation are distributed in the matrix) is made to correspond to If the darkness value is less than the set darkness value (b), dot recording is performed at that position. In this way, dots are recorded at three locations as shown in FIG.

In this way, density modulation is applied to the grayscale image to obtain a dot pattern image.

However, if an attempt is made to express gradations using the method described with reference to FIGS. 1 and 2, if an mXn matrix is used, only mXn+1 gradations can be expressed.

[Objective] In view of the above-mentioned points, the object of the present invention is to
It is an object of the present invention to provide a multi-gradation recording device capable of expressing more gradations. .

In order to achieve this object, the present invention creates a new second dot within the desired occupied area of the first dot group recorded on the recording medium.
The dot group is recorded again to perform multi-gradation expression.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 shows an embodiment of a carriage scanning printer to which the present invention is applied. Here, l indicates a motor, which drives the wire 7 left and right to cause the carriage 6 fixed thereto to scan left and right. 3 is a platen, and recording paper 5
is wrapped around it. This platen 3 is rotationally driven by a pulse motor 2 via a gear 9. 4 is a frame to which each element is attached, and 8 is a guide shaft of the carriage. Note that circuits and the like for controlling these elements are omitted. Furthermore, the recording head mounted on the carriage 6 may be any head capable of dot recording, such as an inkjet type, wire dot type, or thermal head type.
It can take any form.

On the actual flow side, as soon as one line of recording is completed, the paper is not fed by one line, but is controlled to be fed by 1/3 or 1/2 of one dot, for example. As a result, for each dot (or some of the dots) in a row that has been recorded once, the dots that are shifted by 1/3 dot or 1/2 dot in the vertical direction are re-repeated. Can be recorded. That is, vertically shifted double dot recording can be performed by recording on the forward path of the carriage and recording on the backward path accompanied by paper feeding, and then normal paper feeding can be performed.

In addition, by adjusting the printing timing a little without feeding the paper when recording a path, it is possible to perform double dot recording that is shifted in the horizontal direction.

Further, by performing shift control in the vertical direction and shift control in the lateral direction simultaneously, double dot recording shifted in the diagonal direction can be performed.

FIGS. 4A to 4C are diagrams illustrating the state of dot recording according to this embodiment. First, the outward path is recorded as shown in Figure (B), then the paper is fed by 1/2 dot, and at the same time, the printing timing is delayed by 1/2 ton, and the return path is recorded as shown in Figure (C). As a result, a double dot recording as shown in FIG. 2(A) is obtained.

I-. The minute paper feed mentioned above can be achieved by reducing the drive pulses supplied to the pulse motor, and the printing timing can be delayed by intervening a delay element (not shown) such as a shift register. can. The details will be explained later (see FIGS. 7 to 9).

In this way, the apparent recording density can be increased. In the example shown in FIG. 4, although a 2×2 matrix is used, it is possible to express as many as 9 gradations. That is,
By staggering the dot recording, the number of pixels increases from four to eight.

According to the present invention as described above, when an mXn matrix is used, the number of dots is increased to 2mn. As a result, the apparent number of gradations of I-1 is (2mn+1
).

FIG. 5 is a diagram illustrating a method for obtaining a density modulation image using the present embodiment shown in FIGS. 3 and 4. FIG. Here, (a) shows the input image signal, and (b) shows the threshold value matrix. That is, here, a threshold value matrix is prepared in which two levels of threshold values are associated with each pixel. Then, when each input image signal is above the lower threshold, one dot is recorded, and when it exceeds the higher threshold,
Dot recording of the shifted return trip is performed. That is, for an input image signal (a) having a density of nine gradations as shown in FIG.
This corresponds to each pixel one by one. In the illustrated input image signal (a), the two pixels on the left side are the lower ones, so that only the forward dot recording is performed. On the other hand, since the pixel 1- on the right both exceeds the two threshold values, double dot recording is performed in the forward and backward passes. Furthermore, since the lower right pixel is below either darkness value, no recording is performed. In this way, the density image of 4 pixels can be transformed into an 8-step density modulation dot diagram.

FIG. 6(A) is a density modulation dot diagram when the dark value matrix pattern (b) is applied to all the input image signals (a) shown in FIG.

Figure 6 (B) is a density modulation dot diagram when a conventionally known five-gradation threshold matrix pattern (c) is applied to the input image signal (a) shown in Figure 5.

As is clear from comparing FIGS. 6(A) and 6(B), this example has characteristics that have not been seen in the past, such as the opacity of the recording paper and the number of expression gradations. are doing.

FIG. 7 shows a control circuit for controlling the printer shown in FIG. Here, 11 is a ROM that stores the processing program, +2 is a RAM, +3 is a timer, and 14 is a Pr
A (Peripheral rnteface Ada)
pter), +5 is cr+u that controls the whole, +e is the pass line, +7 is the entire printer shown in the third figure (f), and 1st is the recording head 18 and pulse motor 2 built into the printer.
Drivers 21 and 22 that drive 0 are pass lines.

8(A) and (B) show the driver 18 shown in FIG.
2 shows a pulse train sent from to the pulse motor 20. Here, (A) in the same figure is a normal sending pulse train for performing one-line paper feed J, and (B) in the same figure is for “l/2-line paper feed.”
The transmission pulse train for performing this is shown. In this way, a desired paper feed length can be set by adjusting the number of sending pulses.

FIGS. 9A to 9C are timing charts for delaying the recording timing for the recording pad 18 shown in FIG. Now, when the reference signal shown in FIG. 5A is introduced to obtain the drive pulse shown in FIG. On the other hand, when the drive pulse is obtained with a delay of time t (counted by the timer 13) as shown in FIG. 1C, dot recording is performed with a lateral deviation of 172 dots.

FIG. 10 is a flowchart showing the operation of the control circuit shown in FIG. 7. Each step 5l-37 in this figure
has already been explained, so a detailed explanation will be omitted. Then, the subroutines shown in steps S2 and S3 create recording data according to the program stored in the ROM II, and temporarily store the results in the old RA 2.

Although the above description has been made using a carriage scanning type printer as an example, it goes without saying that the present invention can also be applied to a line scanning type dot printer.Furthermore, it is of course applicable not only to monochrome printers but also to dot type color printers.

[Effects] As explained above, according to the present invention, high gradation expression is possible even with a small matrix configuration, so a high-quality halftone dot image can be obtained.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams explaining conventional gradation expression technology, Figure 3 is a schematic configuration diagram showing an embodiment of the present invention, and Figure 4 (
A) to (C) are diagrams explaining the density modulation according to the present invention, FIG. 5 is a diagram explaining the operation when this embodiment is applied to an actual input image signal, and FIGS. 6 (A) and (B) are diagrams explaining the density modulation according to the present invention. 7 is a control circuit diagram for controlling the printer shown in FIG. 3; and FIG. 8 is a diagram illustrating a comparison between this embodiment and the conventional technology. (and Figure 9(A) ~(
C) C) A timing diagram explaining the operation of FIG. 7. FIG. 10 is a flowchart showing the control procedure of this embodiment. DESCRIPTION OF SYMBOLS 1... DC motor, 2... Pulse motor, 3... Platen, 4... Frame, 5... Recording paper, 6... Carriage, 7... Wire, 8... Guide Shaft, 9...gear. Patent Applicant Canon Co., Ltd. Representative Patent Attorney Yoshi Tani - Fig. 1 1234 Fig. 3 5 t+6 87 Fig. 5 Fig. 6 Fig. 7 B) Fig. 8 - "■" ------- No. 9 figure

Claims (1)

[Scope of Claims] A multi-level recording medium characterized in that a new second group of dots is recorded again in the area occupied by the first group of dots recorded on a recording medium to perform multi-gradation expression. Key recording device. (Hereafter, margin)