JP2937615B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used for a facsimile, a digital copier, and the like.

[0002]

2. Description of the Related Art In a facsimile, an image of a document is read by an image sensor, transmitted by a telephone line, and output by an image forming apparatus. Similarly, in a digital copier, a document is read by an image sensor, and an image forming apparatus is driven by a digital signal of the image sensor to output an image.

[0003] In each of these devices, there is a problem that the line of the output image becomes thick and characters and figures become difficult to read. Although this is basically caused by the lack of resolution of the image sensor, it often happens that the details of characters are crushed and difficult to read. For example, problems such as a slanted thin line changing to a bold line, details of minute characters such as "haze" are crushed and cannot be read, and portions such as "black" of characters such as "fungus" are crushed and filled. One of the causes of such a problem is that the threshold value for black / white determination in the image sensor is set to 50% of the total black density.

On the other hand, on the side of the image forming apparatus used in these apparatuses, a normal image forming apparatus is used as it is, and no special attention is paid to crushing of fine characters and thickening of thin lines. This is because an ordinary image forming apparatus is used as it is for a facsimile, a digital copier, or the like.

[0005] In this connection, the prior art is disclosed in Japanese Utility Model Application Laid-Open No. 2-87751, in which the length of the light emitting portion of the LED print head along the main scanning direction is determined by the length of the LED along the main scanning direction. It is proposed that the pitch be 45% or less of the arrangement pitch. However, this apparatus has a problem that a gap is generated between continuous printing dots in the main scanning direction. This is because the dots are separated from each other by using small LEDs, so that the dots are separated and a clear print pattern is obtained.However, even in the case of continuous print dots, a gap that is not sufficiently exposed occurs between the dots, It is unsuitable for printing horizontal lines.

[0006]

SUMMARY OF THE INVENTION The objects of the present invention are as follows: (1) Lines are not thickened, and fine characters and fine figures can be easily read by the naked eye. (3) To provide an image forming apparatus capable of printing substantially continuous gaps without any gaps between the dots while enhancing separation between dots and (3) these results. is there.

[0007]

An image forming apparatus according to the present invention is an image forming apparatus in which a number of light emitting elements are arranged along a main scanning direction, wherein the light emitting elements comprise a main light emitting section and an auxiliary light emitting section.
The main light emitting portion is formed such that one of the length along the main scanning direction and the length along the sub scanning direction is 50% or less of the arrangement pitch of the light emitting elements along the main scanning direction,
The auxiliary light-emitting portion is provided adjacent to the main light-emitting portion along a direction having a length of 50% or less of the arrangement pitch, and the auxiliary light-emitting portion is provided with an electric current passing through an electrode formed so as to traverse the main light-emitting portion. It is characterized in that both the main light emitting unit and the auxiliary light emitting unit emit light with a light emission intensity of the auxiliary light emitting unit weaker than that of the main light emitting unit.

As the light emitting element, for example, an LED of an LED print head may be used. The size of the auxiliary light emitting portion is, for example, 10 to 20 of an arrangement pitch of light emitting elements along one main scanning direction (hereinafter, simply referred to as an arrangement pitch).
%, And a size that can fill the gap between the dots by superimposing the continuous print dots with the output from the adjacent light emitting element is preferable.

[0009]

According to the present invention, the length of the main light emitting portion of the light emitting element is set to 50% or less of the arrangement pitch in either the main scanning direction or the sub-scanning direction. In the conventional light emitting device, the length in the main scanning direction is set to 60 to 70% of the arrangement pitch, and the length in the sub scanning direction is set to 60 to 80%, which is slightly larger than this, except for the Japanese Utility Model Application Laid-Open No. 2-87751. I have.
In the present invention, an auxiliary light emitting unit is provided in addition to the main light emitting unit.
The print output from the auxiliary light emitting unit is small, and does not contribute to printing for isolated print dots. As a result, the separation between dots is improved, and the clarity of the image is improved.

[0010] For continuous printing dots, the output from the auxiliary light emitting unit also contributes to printing by superimposing the output from the auxiliary light emitting unit and the output to the adjacent printing dots. The superposition is the superposition of the outputs of the auxiliary light emitting units,
Alternatively, the output of the auxiliary light emitting unit and the output of the main light emitting unit of the adjacent dot may be superimposed. For this reason, continuous printing dots can be printed with almost no gap.

The improvement in the clarity of the dots is to prevent the line from being thickened and to prevent a fine pattern such as a minute character from being filled up. Along with this, characters and the like may change from thick to thin, but even characters that are thin and have small gaps between dots,
People can read clearly. On the other hand, if the thick characters become thicker, the reading becomes difficult. That is, in a system that reads an input image with an image sensor,
The effect on the reading by the naked eye is smaller when the line is thinly deformed than when the line is thickly deformed.

In connection with this, it can be said that in a facsimile, the number of all black images is small, and the printing ratio is usually 7 to 10.
%. That is, with respect to the all black input image, the print quality is deteriorated due to the remaining unprinted space.
There is no need to think. For this reason, even if the dot area of the output image with respect to the isolated print dots is slightly reduced, the influence on the print quality is small.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described using an LED print head as an example. FIG. 1 shows the LED shape of the embodiment. In the figure,
1 is an LED, 2 is a main light-emitting part, 3 and 4 are auxiliary light-emitting parts, and 5 is an electrode. In the image forming apparatus of the embodiment, LE
Many D1s are arranged linearly along the main scanning direction (the left-right direction in FIG. 1). Therefore, LED1 is integrated and LED
As an array, a number of arrays (not shown) are arranged along the main scanning direction. The other points of the LED print head are known, and the description is omitted.

The image forming apparatus of the embodiment is used for, for example, a facsimile or a digital copier. Then, the image forming apparatus is driven by a digital signal from an image sensor (not shown). Although the current image sensor sets the threshold value for white / black at 50% of the total black density, it may be set to about 60 to 70%. As described above, thick lines are a problem in facsimile, and to eliminate this problem, it is only necessary to increase the discrimination threshold value for reading black with an image sensor.

In the LED 1 shown in FIG. 1, the main light-emitting portion 2 emits strong light, and the auxiliary light-emitting portions 3 and 4 emit light weakly. L
The light emitting mechanism of the ED 1 will be described.
A part of the light-emitting current injected into the auxiliary light-emitting portions 3 and 4 reaches the light-emitting surface below the auxiliary light-emitting portions 3 and 4, so that the auxiliary light-emitting portions 3 and 4 emit light weakly. Part of the light emitted from the light emitting surface below the main light emitting unit 2 goes out of the auxiliary light emitting units 3 and 4 to the outside. Therefore, the auxiliary light emitting units 3 and 4 emit light weaker than the main light emitting unit 2.
Here, the reason why the electrode 5 is disposed so as to penetrate the main light-emitting portion 2 is to prevent the shift of the electrode 5 in the vertical direction in the drawing from affecting the light-emitting current.

The image forming apparatus of the embodiment is an A4 300DP
If the resolution is I (dots / inch), the arrangement pitch P of the LEDs 1 along the main scanning direction is 84.6 μm. The length W of the main light emitting portion 2 along the main scanning direction is 50 μm.
m (approximately 60% of the arrangement pitch P), and the preferable range is 4
0 to 60 μm (about 50 to 70% of the arrangement pitch P). The length L of the main light emitting unit 2 along the sub-scanning direction is, for example, 30 to 40 μm. This is 3 for the arrangement pitch P.
It becomes 5 to 50%. As a result, the main light-emitting portion 2 of the embodiment has a shorter length L in the sub-scanning direction than the conventional example.

The auxiliary light emitting units 3 and 4 overlap light from the auxiliary light emitting units 3 and 4 with light from the main light emitting unit 2 in the next line when printing two or more dots continuously in the sub-scanning direction. so,
This is for filling gaps between dots. The size of the auxiliary light emitting portions 3 and 4 is preferably 10 to 15 on one side.
μm, which means 12 to 18% of the arrangement pitch P. Generally, it is preferable that the size of the auxiliary light emitting portions 3 and 4 is 10% to 20% on one side with respect to the arrangement pitch P. In the embodiment, the auxiliary light-emitting portions 3 and 4 have a square shape in which the length X in the main scanning direction and the length Y in the sub-scanning direction are equal.

FIG. 2 shows a print output pattern of the embodiment for oblique lines. The broken line in the figure indicates the input image of the document, and here, the input image having a width of less than 2 dots is used. The upper left cell in the figure shows the size of one pixel, and the center of the figure shows the print output pattern in the embodiment. The print output pattern in the conventional example is shown in the lower part of the figure.

In the conventional example, the printing line width is increased.
Such a thick line width fills up the gaps of the precise pattern in the fine characters, and makes reading difficult. In a facsimile, a document is rarely input at a strictly right angle to an image sensor, and is usually input with a slight inclination. For this reason, the horizontal straight line changes to an oblique line, and it is particularly important in facsimile to prevent the line width of the oblique line from increasing.

On the other hand, in the embodiment, the length L of the LED 1 in the sub-scanning direction is set to 50% or less of the arrangement pitch.
The print dots shrink in the sub-scanning direction, and as a result, FIG.
The line width does not increase as shown in FIG. Simply reducing the size of the main light emitting section 2 causes an unexposed gap between the upper and lower adjacent dots. However, in the embodiment, the gap is exposed using the auxiliary light emitting units 3 and 4, and the gap is exposed by superimposing the light from the main light emitting unit 2 on the next line. As a result, for print dots that are continuous in the sub-scanning direction, there is almost no gap between the dots.

FIG. 3 shows a print output pattern in the embodiment for an input pattern mainly composed of horizontal lines. For comparison, FIG. 4 shows an output pattern in the conventional example for the same input image pattern. In the conventional example, a horizontal line having a width smaller than one dot is printed as one dot.
Get fat like. On the other hand, in the embodiment, a printed output pattern that is faithful to the input image is obtained.

FIG. 5 shows the print output patterns of the embodiment and the conventional example for a part of fine characters. The broken line in the figure indicates the input image, the solid line indicates the print output pattern of the embodiment, and the chain line indicates the print output pattern in the conventional example. The shaded portions in the figure indicate portions where the print output pattern in the conventional example is thickened from the input image. What is particularly problematic in this input pattern is the white portion in the center of the figure. In the conventional example, the white part is filled up to a considerable extent,
This makes it difficult to read characters. On the other hand, in the embodiment, although the position of the white portion changes slightly,
It remains with almost the same area as the input image.

FIGS. 6, 7, and 8 show the operation principle of the embodiment. The right part of these figures shows the size of one pixel,
A broken line indicates an output pattern from the image sensor, and a solid line indicates a print output pattern in the embodiment. In the embodiment, since the small main light emitting unit 2 is used, the output pattern for the isolated print dot is slightly smaller than the size of one element as shown in FIG. Next, as shown in FIG. 6, when the printing dots are continuously generated, the light from the auxiliary light emitting units 3 and 4 and the light from the main light emitting unit 2 are superimposed on the next printing line, so that the light is emitted along the sub-scanning direction. The gap between all the printing dots is completely filled. As a result, continuous printing dots can be printed without gaps in the sub-scanning direction. Since the length W of the main light emitting portion 2 in the main scanning direction is slightly smaller than that of the conventional example, the width of the printing dot in the main scanning direction is also slightly reduced. As a result, in the case of a horizontal line having a width of one dot, a slight gap may be generated between printing dots along the main scanning direction. However, superposition of light from surrounding dots contributes to a horizontal line having a width of 2 dots or more, so that there is no gap between print dots along the main scanning direction. FIG. 8 shows a print output pattern in the embodiment for a vertical line having a width of one dot. The gaps between dots in the vertical direction (sub-scanning direction) are exposed and filled by the contribution of light from the auxiliary light emitting units 3 and 4.

The features of the embodiment will be described. In the embodiment, a small main light emitting section 2 is used. Therefore, the line width does not increase. In some cases, the line width is reduced. However, even if the line width is reduced, it does not hinder reading of characters and the like. For example, even if the area of the dots forming the character is reduced, the character is changed from a thick character to a thin character, and there is no problem in reading the character. On the other hand, if the line becomes thicker, for example, in the case of a fine character, the gaps between the dots constituting the character are filled up, and reading becomes extremely difficult. Thus, from the viewpoint of the difficulty of reading with the naked eye, a narrower line width has less adverse effect than a thicker line width.

Next, in the embodiment, the auxiliary light-emitting portions 3 and 4 are used so as to prevent an unexposed gap from occurring between printing dots that are continuous in the sub-scanning direction. Therefore, when there is a print pattern that covers a large number of dots, the contour of the pattern is slightly reduced in the embodiment, but an unexposed area does not remain inside the pattern. Therefore, a clear and faithful pattern to the original image can be obtained.

[0026]

Embodiment 2 FIGS. 9 and 10 show a second embodiment. FIG.
, 21 is a new LED, 22 is a new main light emitting unit, and 23, 24, 25, 26 are square auxiliary light emitting units arranged along four corners of the main light emitting unit 22. Resolution 3
When the arrangement pitch P is 84.6 μm at 00 DPI, the length L of the main light emitting portion 22 along the sub-scanning direction is, for example, 30 to 40 μm (35 of the arrangement pitch P) as in the embodiment of FIG.
), And the width W along the main scanning direction is 30
The size is reduced to ４０40 μm. To compensate for this, four auxiliary light emitting units 23, 24, 25 and 26 are provided so as to contribute to both the main scanning direction and the sub-scanning direction. Auxiliary light emitting section 23,
The size of 24, 25, 26 is, for example, 10 to 15 on one side.
μm square.

FIG. 10 shows a print output pattern according to the second embodiment. The input image read by the image sensor is shown on the left side of the figure, and the print output pattern is shown on the right side of the figure.

As a result of reducing the size of the main light emitting section 22, the output pattern for isolated printing dots is reduced in size. For a print pattern that is continuous in the sub-scanning direction,
By superimposing the light beams of 3, 24, 25, and 26, the gap between the dots is filled, and a substantially continuous print output pattern is obtained. Next, for the third pattern in the figure, the auxiliary light emitting units 23, 24, 25,
An almost continuous printing pattern is obtained also in the main scanning direction by the contribution of light from. As shown in FIG. 4, for printing dots that are continuous in a square shape, the gap between the printing dots is exposed to light from the auxiliary light emitting units 23, 24, 25, and 26, and a substantially continuous printing output is obtained. A pattern is obtained.

[0029]

Embodiment 3 FIGS. 11 and 12 show a third embodiment. In the embodiment of FIG. 1, the length L of the main light emitting portion 2 along the sub-scanning direction is reduced, and the auxiliary light emitting portions 3 and 4 are provided so as to contribute to the sub-scanning direction to compensate for this. However, there is no distinction between the main scanning direction and the sub-scanning direction of the original document. If the original input in the main scanning direction is tilted by 90 degrees, the input will be in the sub-scanning direction. Therefore, as shown in FIG. 11, a main light emitting section 32 which is vertically long and whose width W in the main scanning direction is shorter than length L in the sub scanning direction may be used. In FIG. 11, 31 is a new LED, 32 is a new main light emitting unit, 33, 34, 3
Reference numerals 5 and 36 denote new auxiliary light emitting units. Array pitch P is 8
When the width is 4.6 μm, the width W of the main light emitting portion 32 is, for example, 3
0 to 40 μm is preferable, and the length L along the sub-scanning direction is
Is preferably, for example, about 40 to 60 μm. The auxiliary light emitting units 33, 34, 35, 36 have, for example, one side of 10 to 15
The one having a size of about μm is used.

FIG. 12 shows a print output pattern in the embodiment of FIG. As shown in the upper part of FIG. 12, a print output pattern that is slightly reduced vertically is obtained for an isolated print dot. Next, the auxiliary light emitting units 33, 34,
By superimposing the lights from 35 and 36, a line that fills the gap along the main scanning direction is obtained. For the last pattern in FIG. 12, the gap between the printing dots along the main scanning direction is defined by the auxiliary light emitting units 33, 34, 35, and 3.
6, and fills the gap between the printing dots along the sub-scanning direction with the auxiliary light emitting portions 33 to 36.
The print output pattern partially filled with the light from the above is obtained.

In the embodiment, an LED print head has been described as an example, but an EL head can be obtained by replacing the LED with an EL element.

[0032]

According to the present invention, (1) there is no thickening of lines, fine characters and fine figures can be easily read by the naked eye, and (2) continuous printing dots are substantially interposed between printing dots. (3) To provide an image forming apparatus capable of increasing the separation between dots as a result of these, and printing continuous print dots without gaps between print dots.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating a shape of an LED light emitting unit of an image forming apparatus according to an embodiment.

FIG. 2 is a characteristic diagram showing a print output pattern with respect to oblique lines in an image forming apparatus according to an embodiment and a conventional example.

FIG. 3 is a characteristic diagram illustrating a print output pattern for a read input image indicated by a broken line in the image forming apparatus according to the embodiment;

FIG. 4 is a characteristic diagram showing a print output pattern with respect to a read input image indicated by a broken line in a conventional image forming apparatus.

FIG. 5 is a characteristic diagram illustrating a print output pattern for a read input image indicated by a broken line in the image forming apparatus according to the embodiment;

FIG. 6 shows a square 4 in the image forming apparatus of the embodiment.
Characteristic diagram showing print output pattern for connected model input image

FIG. 7 is a characteristic diagram illustrating a print output pattern with respect to an isolated print dot in the image forming apparatus according to the embodiment.

FIG. 8 is a characteristic diagram showing a print output pattern with respect to a vertical line model input image in the image forming apparatus of the embodiment.

FIG. 9 is a plan view illustrating a shape of an LED light emitting unit of the image forming apparatus according to the second embodiment.

FIG. 10 is a characteristic diagram illustrating a print output pattern for a model input image in the image forming apparatus according to the second embodiment.

FIG. 11 is a plan view showing the shape of an LED light emitting unit of the image forming apparatus according to the third embodiment.

FIG. 12 is a characteristic diagram illustrating a print output pattern for a model input image in the image forming apparatus according to the third embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 LED 2 main light-emitting part 3, 4 auxiliary light-emitting part 5 electrode 21 LED 22 main light-emitting part 23, 24, 25, 26 auxiliary light-emitting part 31 LED 32 main light-emitting part 33, 34, 35, 36 auxiliary light-emitting part

Claims (1)

(57) [Claims] 1. An image forming apparatus in which a number of light emitting elements are arranged along a main scanning direction, wherein the light emitting elements include a main light emitting section and an auxiliary light emitting section, and the main light emitting section extends along the main scanning direction. Either the length or the length along the sub-scanning direction is formed as a length of 50% or less of the arrangement pitch of the light emitting elements along the main scanning direction; Both the main light-emitting portion and the auxiliary light-emitting portion are assisted by a current passing through an electrode that is provided adjacent to the main light-emitting portion and that is formed so as to traverse the main light-emitting portion. An image forming apparatus, wherein the light emitting unit emits light at a lower intensity than the main light emitting unit.