JP3063265B2 - Printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color superimposing method for a printer which forms a full-color image by superimposing at least three or more colors in a frame-sequential manner.

[0002]

2. Description of the Related Art Conventionally, 3
As a method of superimposing colors of more than one color, there is a method as shown in FIG. FIG. 7 is a perspective view of a conventional color printer, wherein 1 and 1 'are image recording paper, 2 is a paper feeding section of paper 1, 3 is a platen for image printing, 4 is a thermal head, and 5a is a paper. Reference numeral 1 'denotes a sensor for detecting the tip, and reference numeral 6 denotes an ink film.

In this operation, the paper 1 ′ supplied to the platen 3 from the paper supply unit 2 is wound around the platen 3. The paper 1 'is rotated clockwise in FIG. 7 together with the rotation of the platen 3, and its leading end is detected by a sensor 5a attached to one end in the main scanning direction (a direction perpendicular to the paper traveling direction). The print start position is determined based on the detected data. That is, after the leading end of the paper 1 'has passed the sensor 5a, a motor (not shown) is driven by a predetermined number of pulses, and then the thermal head 4 is driven.
Was turned on to print. The above-described printing operation is performed at least three colors, that is, three times or more in a frame sequential manner to obtain a full-color image.

[0004]

However, in the color printer having the above-described configuration, if the thermal head is pressed unevenly or the print paper is obliquely wound around the platen, the paper travels. In some cases, the skew does not proceed at right angles to the main scanning direction, and the skew moves. When printing proceeds in such a state,
Color superposition is good in the vicinity detected by the sensor, but there is a problem that a relatively large deviation occurs in color superposition due to skew on the opposite side of the diagonal line from the vicinity of the sensor detection. .

[0005] As a result, when observing the printed image, as in the case where the paper is printed by applying a rotational force to the paper centering on the vicinity of the sensor detection, dots of each color are detected at other points, especially at a distant place, by the sensor detection. In some cases, the image appeared to be scattered around the circumference with the vicinity as the center. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to minimize color misregistration even when skew of print paper occurs to the same extent as in the related art.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a printer for forming a full-color image by printing three or more colors of ink on a paper to be fed one by one on a plane-by-side basis. Including two sensors arranged in a direction perpendicular to the transport direction of the paper so as to be able to sense the right and left ends near the end of the paper to be fed, respectively, the detection from the two sensors respectively detecting the left and right ends of the paper A printer is characterized in that a reference point for the overlap printing of the ink is calculated based on a signal to determine the position of the first line of the paper printing.

Further, in order to solve the above-mentioned problems, the present invention provides a heating element in which at least one of the two sensors is a line-type sensor which is long in the right-angle direction and can detect a side end of the paper to be fed. Includes a thermal head arranged wider than a predetermined print width, and selectively energizing a heating element of the thermal head based on a detection signal detecting a side edge of the paper. I do.

Further, according to the present invention, in order to solve the above-mentioned problem, in the overlap printing of the nth color, each of the two sensors detects the left and right front ends of the fed paper from a predetermined measurement start point. The detected pulse numbers up to PLn and Prn, respectively, and the pulse number Pfn calculated by the following equation for the larger detected pulse number

[0009]

(Equation 3)

A reference point for the duplicate print on the paper to be fed is determined based on the number of pulses added to the printer. Further, in order to solve the above-mentioned problem, the present invention uses the line-type sensor, and in the overlap printing of the n-th color, each of the two sensors from the predetermined measurement start point sets the paper to be fed. The number of detected pulses until the left and right ends are detected are denoted by PLn and Prn, respectively. The pulse number Pfn calculated by

[0011]

(Equation 4)

A reference point of the overlap printing for the paper to be fed is determined based on the number of added pulses, and a heating element of the thermal head is selectively energized based on a detection signal detecting a side edge of the paper. A printer characterized by the above is provided. More specifically, in order to solve the above-described problem, the present invention provides sensors at both ends of the paper in the main scanning direction to provide the position of the print paper,
Accurately grasp the state such as the degree of skew and calculate the reference position of color superimposition based on the paper detection data by the sensor so that it is near the center of the first line of the print,
After the paper is detected by the sensor, the platen is rotated by the number of pulses calculated from the calculated value, and the paper is fed by the rotation, and then the thermal head is energized to start printing. The above operation is performed for at least three colors in a frame-sequential manner to obtain a full-color image.

[0013]

[Action] In the present invention places the reference point of the superposition of colors in the vicinity of the center of the first line of the paper printed (7 _1, 7 _2, 7 _3), there since the print start reference point of each color ( In FIG. 3), the distance from the apparent center of rotation due to the skew of the paper to the farthest point where the color misregistration becomes maximum can be made shorter than before. Therefore, even if the skew occurs to the same degree, the apparent radius of gyration is smaller than in the prior art, so that the deviation due to the superposition of colors can be minimized.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an embodiment of the present invention; FIG. FIG. 1 is a perspective view of a color printer according to a first embodiment of the present invention, FIG. 2 is a view for explaining correction of printing in a sub-scanning direction (paper advancing direction), and FIG. FIG. 4 is a perspective view of a color printer according to a second embodiment of the present invention for performing correction and printing, and FIG. 5 is a diagram for detecting a specific pixel when a line sensor is used according to the embodiment of FIG. FIG. 6 is an explanatory diagram of the deviation of the paper in the main scanning direction.

First, the outline of the present invention will be described with reference to FIG. 1, 1 'is an image recording paper, 2 is a paper feeding unit of the paper 1, 3 is a platen for image printing, 4 is a thermal head, 5a is a sensor for detecting one end of the paper 1',
Reference numeral 6 denotes an ink film, and these components are the same as those of the prior art shown in FIG. The present invention
A sensor 5b for detecting the front end of the paper 1 'is disposed near the side opposite to the sensor 5a.

Next, the operation of the color printer will be described with reference to FIG. The platen 3 is driven by a motor (not shown), and the amount of rotation is monitored by an encoder (not shown). When the paper 1 'reaches the sensors 5a and 5b, the leading edge detection sensors 5a and 5b installed at both ends of the papers 1 and 1' in the main scanning direction can detect the position by blocking the optical path thereof. The ink film 6 is sandwiched between the thermal head 4 and the platen 3, and is wound up with the rotation of the platen 3 during printing and moves at the same speed as the paper 1 '.

Next, a first embodiment of the present invention will be described in detail with reference to FIGS. In the printer of FIG. 1, paper 1 ′ supplied from a paper supply unit 2 is wound around a platen 3. In the printing of the first color, when the leading ends of the paper 1 'are detected by the sensors 5a and 5b, the number of pulses from a certain measurement start point (for example, line A in FIG. 2) is set to PL1, Pr1, respectively. A sensor that detects the leading edge of paper 1 'with a delay (the sensor with the larger value of PL1 or Pr1)
, The platen 3 is rotated by a predetermined number of pulses Pf1 to print the first line 7 ₁ (FIG. 3) (FIG. 2).
(C)). After printing a predetermined number of lines, paper 1
Passes through the thermal head 4 and the tip is detected by the sensors 5a and 5b.

Similarly, the second color print is represented by the pulse number PL when the leading edge of the paper 1 'is detected by each of the sensors 5a and 5b from a certain measurement start point (for example, line A in FIG. 2).
2, Pr2. The platen 3 is rotated by a Pf2 pulse shown in the following equation from the sensor through which the paper 1 'has passed with a delay.

[0019]

(Equation 5)

The printing of the first line 7 ₂ (FIG. 3) of the second color is performed (FIG. 2C). Similarly, in the third color print, a certain measurement start point (for example, A in FIG. 2)
Line 3), when the number of pulses when the leading end of the paper 1 'is detected by the respective sensors 5a and 5b is represented by PL3 and Pr3, the platen 3 has a Pf3 pulse shown by the following equation from the sensor that the paper 1' has passed with a delay. To

[0021]

(Equation 6)

The first line 7 ₃ (FIG. 3) of the third color is printed by rotating (FIG. 2C). As described above, when the front end of the paper 1 'is detected by the sensors 5a and 5b installed at both ends in the main scanning direction and the correction is performed as described above, the reference point of the color superposition is set as shown in FIG. the first line 7 each color _1, 7 _2, 7 ₃ can be in the center.

FIG. 4 shows a second embodiment of the present invention. Therefore, components having the same functions as in the first embodiment are given the same numbers. In this embodiment, at least one of the sensors arranged at both ends in the main scanning direction uses the line-type sensor 5c. The line type sensor 5c includes a plurality of detection pixels arranged in parallel in the main scanning direction,
′ Can be simultaneously detected.

In the case where the line type sensor 5c detects the leading edge of the paper 1 ', as shown in FIG. 5, if the detection is not performed by a predetermined detection pixel of the sensor 5c, when the paper 1' skews, Since there is a difference in the number of measurement pulses, the detection pixel of the line-type sensor 5c is determined, and the tip of the paper 1 'is detected based on a signal from the pixel. Also,
The thermal head 4 'is provided with a heating element which is larger by several dots at both ends than the print width. Therefore, even if the relative positional relationship between the paper 1' and the thermal head 4 'is slightly shifted in the main scanning direction, power is supplied. The heating element can be moved to print at a predetermined position on the paper.

The correction of the color superposition according to the present embodiment in the printer configured as described above is performed as follows. Note that the same method as in the first embodiment is used for the correction of the color superposition in the sub-scanning direction. In the printing of the first color, the number of pulses from a certain measurement start point when the leading edge of the paper 1 'is detected by a specific pixel of the sensor 5a and the line-type sensor 5c is denoted by PL1 and Pr1, respectively. The first line is printed by rotating the platen 3 by a predetermined number of pulses Pf1 from a sensor that detects the leading end of the paper 1 'with a delay (the sensor having the larger value of PL1 or Pr1).

Immediately before printing the first line , the side edge of the paper 1 'is detected by the line type sensor 5c.
Since the size of the paper 1 'is known in advance, the heating element to be energized of the thermal head 4' is determined based on the detection data so that the print position is at the center of the paper 1 'in the main scanning direction. That is, as shown in FIG. 6, when the side end of the paper 1 'is detected by the line type sensor 5c to be shifted by d dots from the predetermined position, the heating element to be energized of the thermal head is shifted by d dots to perform printing. Then, the printing position is distributed in the main scanning direction with respect to the paper 1 ', so that the margin can be made uniform.

The correction in the main scanning direction is performed for all the print lines during the printing operation, and the deviation in the main scanning direction is performed based on the deviation of one dot of the heating element of the thermal head 4 '. Line type sensor 5c is 1
When the displacement of the dots is detected, the heating element of the thermal head 4 'is shifted by one dot. When the printing of all the lines of the first color is completed, the end of the paper 1 ′ passes through the thermal head 4 ′ and then the leading end passes through the thermal head 4 ′ again, and the sensor 5 a and the line-type sensor 5 c
Is transported to the position where the tip is detected.

Similarly, in the printing of the second color, when the specific pixel of the sensor 5a and the line type sensor 5c detects the leading edge of the paper 1 'from a certain measurement start point, the number of pulses up to that point is represented by PL2, Pr2, respectively. I do. So, paper 1
The platen 3 is rotated by the Pf2 pulse shown in the following equation from the sensor from which the

[0029]

(Equation 7)

The first line of the second color is printed.
As for the correction in the main scanning direction, the heating element of the thermal head 4 'is selectively energized based on the side edge detection data of the line sensor 5c so that the margin in the main scanning direction is constant as in the first color. Let it. In the printing of the third color, similarly to the correction of the second color, the number of pulses from when a certain pixel of the sensor 5a and the specific pixel of the line-type sensor 5c detects the leading edge of the paper 1 'is P, respectively.
L3 and Pr3. Then, the platen 3 is moved by the pulse Pf3 shown in the following equation from the sensor from which the leading end of the paper 1 'has passed late.

[0031]

(Equation 8)

The first line of the third color is printed by rotating. The correction in the main scanning direction is performed in the same manner as the first color and the second color. As described above, the sensors 5a and 5c are provided at both ends in the main scanning direction, and at least one of the sensors 5a and 5c is constituted by the line-type sensor 5c to perform correction in both the sub-scanning direction and the main scanning direction as described above. In this way, the reference point for superimposing the colors is set to the first color for each color.
The center of the line can be set, and the margin in the main scanning direction can be made uniform.

[0033]

As described above, according to the present invention,
By arranging sensors at both ends in the main scanning direction and performing correction in the sub-scanning direction, the reference point for color superposition can be set at the center of the first line for each color. Can be reduced.

In addition, since at least one of the sensors disposed at both ends in the main scanning direction is a line type sensor, the printing in the main scanning direction can be corrected at the same time, so that the margin in the main scanning direction can be made uniform. It has an effective effect. Furthermore, according to the sub-scanning direction correction method used in the present invention, there is an advantage that it is easy to manufacture since there is no need to align the sensors installed at both ends in the main scanning direction.

[Brief description of the drawings]

FIG. 1 is a perspective view of a color printer according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of print correction in a sub-scanning direction.

FIG. 3 is an explanatory diagram when printing is performed with correction in the sub-scanning direction according to the embodiment of FIG.

FIG. 4 is a perspective view of a color printer according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram for detecting a specific pixel when a line sensor is used according to the embodiment of FIG. 4;

FIG. 6 is an explanatory diagram of paper deviation with respect to the main scanning direction.

FIG. 7 is a perspective view of a conventional color printer.

[Explanation of symbols]

1,1', ₁ 1, 1 _2, 1 _3: Paper 2: sheet feeding part 3: platen 4,4': thermal head 5a, 5b: sensor 5c: the line sensor 6: ink film 7 _1, 7 _2, 7 ₃ : First line of print

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41J 2/325 B41J 11/00 B41J 11/42 B41J 13/00

Claims (2)

(57) [Claims] 1. A printer for forming a full-color image by sequentially printing three or more colors of ink on a paper to be fed one by one in a frame-sequential manner, wherein left and right front ends near the edge of the paper to be fed are respectively detected. And a reference point for overlapping printing of the ink based on detection signals from the two sensors which respectively detect the right and left ends of the paper. with calculated and to position the first line of printing of the pane over path a, in the overlap printing of the n color, a predetermined measurement start
From the point of view of each of the two sensors
The number of detection pulses until the right and left ends are detected is PLn
, And Prn, and the larger the number of detected pulses,
The number of pulses Pfn calculated from To the feeding paper based on the number of added pulses
A printer for determining a reference point for the duplicate print . 2. A heating apparatus according to claim 1, wherein at least one of said two sensors is a line-type sensor which is long in said right-angle direction and is capable of detecting a side end of said paper to be fed. A thermal head, wherein a heating element of the thermal head is selectively energized based on a detection signal detecting a side edge of the paper , and the line-type sensor is used, and the overlapping of the n-th color is performed. Step
In the lint, the two sensors from a predetermined measurement start point
Each of the sensors detects the left and right ends of the paper to be fed.
The number of detection pulses up to the detection is PLn and Prn, respectively.
The number of pulses, which is calculated by the following equation for the person not the size of the number of pulses
Pfn ( Equation 2) To the feeding paper based on the number of added pulses
Determine the reference point of the duplicate print, and determine the side edge of the paper.
Heat of the thermal head based on the detection signal that
2. The printer according to claim 1 , wherein the body is selectively energized .