JPH03216679A - Image forming device - Google Patents

Abstract

PURPOSE:To attain fast printing and to obtain a high-resolution gradational image by providing a light emitting means which has plural light emission parts and outputs plural light beams and whose spot shapes are in point or line symmetrical relation, and a light emission control means. CONSTITUTION:The light beams emitted by a 1st laser diode 101a and a 2nd laser diode 101b selectively after passing through a slit 102 are reflected by a 1st mirror 103 and then made incident on a polygon mirror 104. The light beams are shaped into relation of line or point symmetry by passing through the slit 102. Under the light emission control of optical system control parts 205, light beams in different spot shapes are emitted independently or in combination to vary the shape and size of picture elements (dots), so sharp fine dots and sharp lines with good balance can be reproduced stably. Consequently, the fast printing is made possible and the high-resolution gradational image can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image forming device that records an image using a light beam output from a light emitting section, and more specifically relates to an image forming apparatus that records an image using a light beam output from a light emitting section. The present invention relates to an image forming apparatus that improves the image forming apparatus.

[Conventional technology]

Conventionally, when recording means such as image forming apparatuses cannot perform intermediate density recording (in other words, when multi-tone recording cannot be performed), a combination of rIJ and rQ4 recording dots is used to print images in the matrix. An area gradation method is used in which halftones are reproduced in a pseudo manner by changing the area ratio of recorded dots, and a specific example is a dither method.

The dither method creates density by the number of dots per unit area, so it has excellent gradation expression, but has the problem of lower resolution.As a way to solve this problem, we have developed a method that uses dots of light beams. A multi-level dither method has been proposed that expresses gradation by using pulse width modulation to express several gradations of light and shade in one pixel, and also prevents deterioration of resolution by reducing the dither matrix size. However, there is a limit to how short the lighting time of one pixel can be shortened, so the method of pulse width modulating the dots of the light beam has the problem that it is not possible to increase the gradation of one pixel when the recording speed is high. However, it was not always possible to achieve high resolution and multiple gradations.

Therefore, in order to improve gradation and resolution, as shown in Japanese Patent Application Laid-Open No. 63173074, one pixel is composed of two beams divided into two in the sub-scanning direction, and a matrix is formed in the pixel itself. A digital copying apparatus has been proposed that provides gradation.

On the other hand, in recent years, with the development of DTP (disk top publishing, e.g. disk top word processor, etc.), high resolution and multi-gradation are required for image forming devices such as printers. There is. In order to meet these demands, it is necessary to improve the reproducibility of minute dots, but when minute dots are used, when the dots are aggregated, the aggregation becomes poor, and conversely, due to the dot aggregation, large When using dots, there was a problem that small dots could not be reproduced. Therefore,
In order to improve the reproducibility of minute dots and to adequately represent a dot set, consideration has been given to making the spot diameter (dot diameter) variable and using the spot diameter selectively.

For example, as disclosed in Japanese Patent Application Laid-Open No. 63-265642, an image recording apparatus has been proposed which is capable of forming clear, high-quality images by switching the spot diameter of one light beam.

[Problem to be solved by the invention]

However, according to the digital copying device disclosed in Japanese Patent Application Laid-Open No. 63-173074 and the image recording device disclosed in Japanese Patent Application Laid-Open No. 63-265642, high resolution. Although it is possible to realize multiple gradations, for example, according to the digital copying apparatus disclosed in Japanese Patent Application Laid-Open No. 63-173074, the number of gradations divided into two in the sub-scanning direction is
One pixel consists of two beams, and the uniformity of the dots (equal in the main scanning direction and sub-scanning direction) is not sufficient, so there is a problem that minute dots and sharp lines cannot be reproduced satisfactorily. Ta. Also, JP-A No. 63-26564
According to the image recording device of Publication No. 2, by selectively using the spot diameter, for example, the spot diameter can be reduced to improve the reproducibility of minute dots, and conversely, the spot diameter can be increased to obtain a sufficient collection of dots. However, since the spot diameter of one light beam is switched, in other words, one laser diode is controlled and the spot diameter is varied, there is a problem that the stability of the spont diameter is poor. Another problem was that it was not suitable for high-speed printing.

Furthermore, the image recording device disclosed in Japanese Patent Application Laid-open No. 63-265642 and the digital copying device disclosed in Japanese Patent Application Publication No. 63-173074 have the disadvantage that they cannot reproduce quadrilateral lines.

The present invention has been made in view of the above, and is capable of stably reproducing clear, well-balanced fine dots and sharp lines, capable of high-speed printing, and with high resolution.
The first objective is to be able to obtain a multi-tone image.

A second purpose is to be able to reproduce the lines of a quadrilateral.

[Means to solve the problem]

In order to achieve the above-mentioned first object, the present invention includes a light emitting means that has a plurality of light emitting sections and outputs a plurality of light beams whose spot shapes are respectively point-symmetric or line-symmetric; An image forming apparatus comprising: a control means for performing predetermined light emission control of a light emitting means; and a plurality of light beams being emitted singly or in combination to change the shape and size of a pixel (dot) under the light emission control of the control means. It is intended to serve.

Furthermore, in order to achieve the above-mentioned second object, an image forming apparatus is provided in which the above-mentioned spot shape has a straight line portion parallel to the sub-scanning direction.

[Operation] In the light emission control of the light emitting device, the control means of the image forming apparatus of the present invention selectively selects a plurality of light beams whose spot shapes are point symmetrical or line symmetrical, either singly or in combination. This method clearly reproduces minute dots and dot groups. Furthermore, the plurality of light emitting sections of the light emitting means are switched to output light beams with different spot shapes stably and at high speed. Furthermore, a rectangular line is reproduced by using a light beam in the shape of a slot 1 having a straight line portion parallel to the sub-scanning direction.

〔Example〕

Hereinafter, the image forming apparatus of the present invention will be described in detail based on the drawings.

FIG. 1 shows an embodiment of an image forming apparatus according to the present invention, and to simplify the explanation, only the configuration of an optical system (semiconductor laser light source device) which is a main part of the present invention is shown. In this embodiment, an example in which an fθ lens and a polygon mirror are used as a semiconductor laser light source device will be described.

The semiconductor laser light source device includes an I laser diode lo1a and a second laser diode IO1b that output a light beam (laser beam), and a first laser diode 10fa.
and a slit 102 that corrects the spont shape of the light beam output from the second laser diode 10lb into a point-symmetrical relationship; a first mirror 103 that reflects the light beam that has passed through the slit 102 in a predetermined direction; a polygon mirror 104 that scans the reflection direction of the light beam reflected by the mirror, fθ lenses 105a and 105b that make the light beam scanned by the polygon mirror 104 enter the second mirror 106 and the third mirror 107, and the A first synchronization sensor 108a and a second synchronization sensor 108b for temporally correcting the laser diode 101a and the second laser diode 10lb, and optical system control for controlling the light emission of the first laser diode 101a and the second laser diode 10lb. 205 (see FIG. 2).

Note that the light beams from the first laser diode 101a and the second laser diode 10lb pass through the slit 102 to form a spot shape (shape having a line-symmetric relationship) as shown in FIG.

FIG. 2 is an explanatory diagram showing the flow of print data (image information). The print data input to the input buffer 201 is converted into a conversion table 2 under the control of the microprocessor 203.
At step 02, information for each dot is converted into bitmap dot information. Although details are omitted, this dot information includes on/off information for each don I and information about what kind of spot is used. Based on this dot information, corresponding data is written into the first output buffer 204a and the second output buffer 204b. Under the control of the optical system control unit 105, the first laser diode 101a and the second laser diode 10lb start writing data in the first output pumper 204a and the second output huffer 204b from the same position and at the same time, thereby changing the shape. A latent image can be formed by combining two spots with different values.

The operation of the above configuration will be explained.

The light beams selectively emitted from the first laser diode 101a and the second laser diode 10lb pass through the slit 102, are reflected by the first mirror 103, and enter the polygon mirror 104. This light beam is scanned by a polygon mirror 104 and fθ lenses 105a, 1
05b, the second mirror 106 and the third mirror 1
It is incident on 07. The light beam incident on the second mirror 106 is transmitted to the first synchronization sensor 108a and the second synchronization sensor 10.
8b and is used to synchronize each line. As a result, temporal correction of the first laser diode 101a and the second laser diode 10lb is performed,
Writing can be started from the same position at the same time, and it is possible to prevent misalignment of the first laser diode 101a and the second laser diode 10lb in the main scanning direction. Further, the light beam incident on the third mirror 107 is reflected to form an electrostatic latent image on a photoreceptor (not shown).

FIG. 4(a) shows a specific example in which the two spots described above are combined to form a dot, and FIG. 4(b) shows a timing chart thereof. As shown in the figure, uniform dots can be formed in the main scanning direction and the sub-scanning direction by combining symmetrically shaped spots. In addition, Fig. 5 (a
), (b), the first laser diode 1
0. By starting the line using a light beam of 1a (spot shape) and switching to a light beam of 10lb from the second laser diode (spot shape) in the middle,
You can draw a quadrilateral line whose four sides are sharp straight lines.

In addition, as shown in Figure 6(a), not only black dots but also white dots can be drawn in a well-balanced manner.
The entire image can be made clearer.

Furthermore, by changing the combination of spots such as the hexagonal dots shown in FIG. can be used selectively.

As mentioned above, in the image forming apparatus of this embodiment, the shape and size of the dots can be varied, so it is possible to freely reproduce fine dots and sharp lines with good clarity, and high Images with high resolution and multiple gradations can be obtained.

In this example, the spot shape was line-symmetrical, but as shown in FIG. 7(a), the spot shape was point-symmetrical, and dots were formed using this as shown in FIG. 7(b). You can also get the same effect.

Further, in this embodiment, the light beams of the first laser diode 101a and the second laser diode 10lb are passed through the slit 102 to form a spot shape as shown in FIG. Of course, a method of outputting a light beam having a predetermined spot shape each time the laser diode 10lb emits light may also be used.

〔Effect of the invention〕

As described above, the image forming apparatus of the present invention has a plurality of light emitting sections and a light emitting means that outputs a plurality of light beams whose bont shapes are point-symmetric or line-symmetric, respectively; A control means for controlling predetermined light emission of the light emitting means, and a plurality of light beams are emitted singly or in combination by the light emission control of the control means, and a pixel (dot) is emitted.
By changing the shape and size of the printer, it is possible to stably reproduce clear, well-balanced minute dots and sharp lines, and also enables high-speed printing to obtain high-resolution, multi-gradation images. I can do it.

Further, since the spot shape described above has a straight line portion parallel to the sub-scanning direction, it is possible to reproduce a quadrilateral line.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the image forming apparatus of the present invention, FIG. 2 is an explanatory diagram showing the flow of print data (image information) of the image forming apparatus of the present invention, and FIG. 3 is an explanatory diagram of the embodiment. An explanatory diagram showing the spot shape of the light beams of the first laser diode and the second laser diode, FIG.
FIG. 4(b) is a timing chart of dot formation in FIG. 4(a), FIGS. 5(a) and (b) are explanatory diagrams and timing charts showing the formation of quadrilateral lines, and FIG. 6(a)
6(b) is an explanatory diagram showing a hexagonal dot, FIG. 7(a) is an explanatory diagram showing an example of a point-symmetric spot shape, and FIG. 7(b) is an explanatory diagram showing a hexagonal dot. FIG. 7 is an explanatory diagram showing dots using the spot shape of FIG. 7(a). Explanation of symbols L O 1 a---Lth laser diode 1 0 l
b-1-1 Second laser diode 1 0 2 --- Slit- 103-11 11 First mirror 1 0 4
---・． Polygon mirror 105a, lO5b---fθ lens 106--111 2nd mirror 107--13rd mirror 108a---1st synchronization sensor 1 0 8 t)-----1 2nd synchronization sensor 2 0
1---One-person buffer 20 2--One conversion table 203--One microprocessor 204a--One first output buffer 204 b. ---1st output bath sofa 205--
- Optical system control section

Claims (3)

[Claims] (1) In an image forming apparatus that records an image using a light beam output from a light emitting section, the image forming apparatus has a plurality of light emitting sections, and the spot shapes of the plurality of light beams are point symmetrical or line symmetrical. What is claimed is: 1. An image forming apparatus comprising: a light emitting device that outputs a light emitting device; and a control device that performs predetermined light emission control of the light emitting device. (2) The image forming apparatus according to claim 1, wherein the control means causes the plurality of light beams to emit light singly or in combination, and changes the shape and size of a pixel (dot). (3) The image forming apparatus according to any one of claims 1 and 2, wherein the spot shape has a straight line portion parallel to the sub-scanning direction.