JPH09240047A - Line width correcting circuit of printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a width of a thin line without influencing the whole of an image by a low costed structure. SOLUTION: An N-dot detection/positional detection circuit 20 detects an image of which the width is N dots based on the number of dots N representing the width of a vertical line to be corrected, and stores its position in a temporary storage 21. A relational operation circuit 22 compares a positional pixel value of a precedent line stored in the temporary storage 21 with the pixel value of the position of the present line detected with the N-dot detection/ positional detection circuit 20. When conformed, the line is detected as a vertical line. Further, a 45 deg. slanting line is detected by comparing the pixels at the pixel positions in 45 deg. slanting direction of the before and after lines. A pulse width adjusting circuit 23 adjusts the pulse width corresponding to positions of the vertical line and slanting line so as to be the same one as the width of a horizontal line according to characteristics of a printer engine 13.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laser printer,
The present invention relates to a line width correction circuit for a printer in a laser copying machine or the like.

[0002]

2. Description of the Related Art Generally, in a laser printing apparatus such as a laser printer or a laser copying machine which forms an image with dots, it is almost impossible to make the dots formed into a perfect circle. In the characteristic that the shape is an ellipse that is long in the horizontal direction, the vertical lines become thicker and the horizontal lines become thicker.
Further, in the characteristic that the beam shape is an elliptical shape that is long in the vertical direction, the vertical lines and the horizontal lines are thin. Therefore, if the beam shape is not a perfect circle, there will be a difference in the thickness of the thin vertical lines and the thin horizontal lines, which will impair the image quality, and if the same original is printed in landscape and portrait, the print results will differ. Make an impression.

The width of the thin line is 600 dpi,
The diameter of one dot is about 100 μm and is 1 or 2 dots. The reason for this is that if the line becomes thicker than that, the relative aspect ratio is apparently improved due to the portion where the dots overlap, and it becomes impossible for the human eye to see the difference, so there is no need to make corrections. .

Conventionally, as this type of method, (1) a method of increasing or decreasing the irradiation time of the laser beam by a certain amount is known. In this method, in the case of a printer engine with a characteristic that dots are elliptical with a long horizontal direction, the pulse that drives the laser diode is cut in order to shorten the irradiation time of laser light, while the dots are long in the vertical direction. In the case of an elliptical printer engine, the pulse is extended in order to lengthen the irradiation time of the laser light.

As another method, (2) a method of correcting with a matching pattern is known. In this method, a matching pattern is performed to extract a line, and the extracted line is thickened or thinned by PWM (pulse width modulation). In addition, as a line extraction method, a smoothing circuit or the like used for the purpose of jaggy correction can be used to perform a matching pattern with a certain window size.

[0006]

However, although the method (1) is effective in correcting the line width, the pulse width is uniformly increased and decreased without classifying lines and non-lines. Is not always effective when viewed as
There is a problem that the image quality is deteriorated.

Further, in the above method (2), since the line is extracted by the matching pattern, the above problem can be solved, but a special circuit is required and the cost becomes high, and because of the PWM method. There is a problem that the frequency is limited.

In view of the above conventional problems, it is an object of the present invention to provide a line width correction circuit for a printer which is inexpensive and can correct the width of a fine line without affecting the entire image.

[0009]

In order to achieve the above object, a first means is a printer for printing image data with dots according to a pulse width, in a horizontal direction indicating a width of a vertical line designated in advance. A detection circuit for detecting the position of the vertical line by detecting pixels of the number of dots and then comparing the pixels at the same pixel positions of the lines before and after, and the pulse corresponding to the position of the vertical line detected by the detection circuit. And a pulse width adjusting circuit for adjusting the width to be the same as the width of the horizontal line.

The second means is characterized in that in the first means, only the position data of the pixels to be compared are stored in the detection circuit.

In a third means, the detection circuit in the first or second means also compares the pixels at the pixel positions in the 45 ° diagonal direction of the preceding and following lines by 45 °.
Is detected, and the pulse width adjusting circuit adjusts the width of the pulse corresponding to the position of the oblique line detected by the detecting circuit to be the same as the width of the horizontal line.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a line width correction circuit of a printer according to the present invention, FIG. 2 is a timing chart for explaining a process of thinning a vertical line and a diagonal line, and FIG. 3 is a vertical line and a diagonal line. 6 is a timing chart for explaining a process of thickening a line.

In FIG. 1, the image data stored in the page buffer 10 is read by the read circuit 11, and only the width of the vertical line and the diagonal line of 45 ° is read from the pulse width adjustment circuit 23 by the video I / F circuit 12. Is adjusted based on the pulse width of the laser beam and then sent to the printer engine 13 to form dots by the laser beam. In this case, the characteristics of the printer engine 13 include one in which the beam shape is an ellipse that is long in the horizontal direction and one in which the beam shape is an ellipse that is long in the vertical direction.

The N dot detection / position detection circuit 20 is preset with the number of dots N indicating the width of the vertical line to be corrected, and the N dot detection / position detection circuit 20 is read by the read circuit 11 from the page buffer 10. When an image with a width of the number of dots N is detected for the output line, the position is stored in the temporary storage device 21.

The comparison operation circuit 22 compares the pixel value of the position of the previous line stored in the temporary storage device 21 with the pixel value of the position of the current line detected by the N dot detection / position detection circuit 20. If they match, a vertical line is detected. Also, if the pixel position at the beginning of the current line is displaced by one pixel from the previous line, it is represented by Y = X / 2.
It is detected as an oblique line of 5 °, or as an oblique line of 45 ° represented by Y = −X / 2 when it is displaced by one pixel.

As a characteristic of the printer engine 13, when the beam shape is an elliptical shape that is long in the horizontal direction, the vertical lines and the diagonal lines are thicker than the horizontal lines. Therefore, as shown in FIG. Based on the above, the pulse width adjusting circuit 23 shortens only the pulse width at the positions of the vertical line and the diagonal line. On the contrary, when the beam shape is an ellipse that is long in the vertical direction as a characteristic of the printer engine 13, the vertical lines and the diagonal lines are thinner than the horizontal lines. Therefore, based on the detection result of the comparison calculation circuit 22, as shown in FIG. Then, the pulse width adjusting circuit 23 increases only the pulse width at the positions of the vertical line and the diagonal line. Therefore, since only the beam shapes corresponding to the vertical lines and the diagonal lines are corrected to be circular, the widths of the vertical lines and the diagonal lines become the same.

2 and 3 show the case where the line width (video data) is 1 (= N) dot clock width, and this video data is delayed according to the characteristics of the printer engine 13. Then, in FIG. 2, the horizontal direction of the beam is shortened by ANDing the video data and the delay data, while in FIG. 3, the horizontal direction of the beam is lengthened by ORing the video data and the delay data. Therefore, according to the above-described embodiment, since the vertical lines and the diagonal lines are detected and only the beams corresponding to the vertical lines and the diagonal lines are corrected, the width of only the thin lines can be reduced without affecting the entire image with an inexpensive configuration. Can be corrected.

[0018]

As described above, according to the first aspect of the invention, the number of pixels in the horizontal direction indicating the width of the vertical line designated in advance is detected, and then the pixels at the same pixel position on the preceding and following lines are detected. The position of the vertical line is detected by comparing pixels, and the pulse width corresponding to the position of the vertical line is adjusted to be the same as the width of the horizontal line. Therefore, an inexpensive configuration does not affect the entire image. The width of the thin line can be corrected.

According to the second aspect of the invention, since only the position data of the pixels to be compared are stored, the capacity of the memory at the time of comparison can be reduced.

According to the third aspect of the invention, the 45 ° diagonal line is detected by comparing the pixels at the 45 ° diagonal pixel positions of the preceding and following lines, and the pulse width corresponding to the diagonal line position is detected. Is adjusted to be the same as the width of the horizontal line, the width of the thin line can be corrected without affecting the entire image with an inexpensive configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a line width correction circuit of a printer according to the present invention.

FIG. 2 is a timing chart for explaining a process of thinning a vertical line and an oblique line.

FIG. 3 is a timing chart for explaining a process of thickening a vertical line and a diagonal line.

[Explanation of symbols]

 13 Printer Engine 20 N Dot Detection / Position Detection Circuit 21 Temporary Storage Device 22 Comparison Arithmetic Circuit 23 Pulse Width Adjustment Circuit

Claims (3)

[Claims] 1. A printer that prints image data with dots according to pulse width, detects pixels of the number of dots in the horizontal direction indicating the width of a vertical line designated in advance, and then detects the same pixel position in the preceding and following lines. A detection circuit that detects the position of a vertical line by comparing pixels, and a pulse width adjustment circuit that adjusts the width of the pulse corresponding to the position of the vertical line detected by the detection circuit to be the same as the width of the horizontal line. And a line width correction circuit for the printer. 2. The line width correction circuit for a printer according to claim 1, wherein the detection circuit stores only position data of pixels to be compared. 3. The detection circuit also includes four lines in front and back lines.
A 45 ° diagonal line is detected by comparing pixels at pixel positions in the 5 ° diagonal direction, and the pulse width adjustment circuit also determines the width of the pulse corresponding to the position of the diagonal line detected by the detection circuit as a horizontal line. 3. The line width correction circuit for a printer according to claim 1, wherein the line width correction circuit adjusts the line width to be the same as the line width.