JPH10271291A - Pixel density changing method and image forming apparatus - Google Patents

Abstract

(57) [Problem] To emulate a line width faithfully when a laser printer emulates a GL such as an XY plotter. A printer (21) having a control unit (23) that scans a laser beam from a semiconductor laser (1) and irradiates it onto a photoreceptor (5), and changes the number of rotations of a polygon mirror (6) and an image clock to change the image density. , Control unit 23
Controls to change the pixel density of the printer 21 to a pixel density that is an integral multiple of 254 dpi when emulating a GL such as an XY plotter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pixel density changing method for changing and outputting a pixel density between images formed by different image forming methods and an image forming apparatus to which the method is applied.

[0002]

2. Description of the Related Art Conventionally, printers have been provided which scan laser light from a laser light source to irradiate a photosensitive member with light, and form an image by dots using the rotation speed of a polygon mirror and an image clock. The pixel density that determines the resolution in such a printer has conventionally been fixed. On the other hand, changing the pixel density to change the resolution has been proposed, for example, in Japanese Patent Laid-Open No. 61-277255. More recently, for example, 240/300 /
A laser printer that can be set to a plurality of pixel densities of 400/600 dpi has also been proposed.

[0003]

However, when a graphic language (hereinafter, referred to as GL) such as an XY plotter is emulated by the above-described printer, the conventional printer faithfully reproduces the line width. In some cases, the image quality may be reduced due to the increase or decrease of the line width depending on the line width. This will be described with reference to FIG. 5 showing a conventional scanning state using a 400 dpi laser beam and FIG. 6 showing a scanning state using a 600 dpi laser beam. Generally, in a GL such as an XY plotter, the line width can be selected in units of 0.1 mm. Therefore, when emulating with a laser printer, the line width is composed of several dots.
In a pi laser printer, as shown in FIG. 5, two dots are required for a line width of 0.1 mm, three dots for a line width of 0.2 mm, and three dots for a line width of 0.3 mm. It is preferable to use five dots. On the other hand, the conventional 600d
In a pi laser printer, as shown in FIG.
It is preferable that the line width be 2 dots for a line width of mm, 5 dots for a line width of 0.2 mm, and 7 dots for a line width of 0.3 mm. However, if GL is emulated at the pixel density used in the conventional laser printer, at 400 dpi, as shown in FIG.
m line is thicker, 0.2 mm line is thinner,
The 3 mm line will be drawn thicker. Further, as shown in FIG. 6, in the case of 600 dpi, the line of 0.2 mm is drawn almost correctly, but the lines of 0.1 mm and 0.3 mm are drawn narrower, respectively. This is dpi
Represents the number of dots per inch. 400 dpi indicates that there are 400 dots per inch, and when this is applied to the metric system,
This is because the size of the diameter of one dot is not a divisible numerical value.

The present invention has been made in view of such a situation of the prior art, and a first object of the present invention is to reproduce a line width faithfully when a laser printer emulates a GL such as an XY plotter. It is an object of the present invention to provide a method for changing the pixel density that can be performed.

A second object of the present invention is to provide an image forming apparatus capable of changing a pixel density so as to faithfully reproduce a line width when a laser printer emulates a GL such as an XY plotter. It is in.

A third object of the present invention is to provide an image forming apparatus capable of selecting the pixel density in a conventional printer as well as the pixel density conversion according to the present invention.

[0007]

In order to achieve the first object, the first means uses the pixel density of the first image forming apparatus in a different graphic language from that of the first image forming apparatus. In the pixel density changing method for changing to the pixel density of the second image forming apparatus, when emulating the graphic language of the second image forming apparatus, the width of one dot of the second image forming apparatus is equal to the first dot. The pixel density of the first image forming apparatus is changed so as to be an integral multiple of the width of one dot of the image forming apparatus.

In the second means, the first image forming apparatus in the first means scans a laser beam from a laser light source and irradiates the photosensitive member with a laser beam, and changes the number of rotations of a polygon mirror and an image clock. The second image forming apparatus comprises an XY plotter, wherein the second image forming apparatus comprises an XY plotter.

The third means is the second means, wherein the second means
When the pixel density is changed from the first image forming apparatus to the first image forming apparatus, the first image forming apparatus changes the pixel density to 254.
It is characterized in that the pixel density is changed to an integer multiple of dpi.

In a pixel density changing method for a printer, which scans a laser beam from a laser light source and irradiates the photosensitive member with light, and changes the number of rotations of a polygon mirror and an image clock to change the image density, a XY plotter or the like is used. When the graphic language is emulated, the pixel density of the printer is changed to an integer multiple of 254 dpi.

In order to achieve the second object, the fourth means scans a laser beam from a laser light source and irradiates the photoreceptor with the laser beam, and changes the rotation speed of the polygon mirror and the image clock to change the image clock. In an image forming apparatus having a control unit for changing the density to form an image, the control unit may control the X
When a graphic language such as a Y plotter is emulated, control is performed so as to change the pixel density of the printer to a pixel density that is an integral multiple of 254 dpi.

In order to achieve the third object, a fifth means is characterized in that the control unit can select a pixel density other than an integer multiple of 254 dpi.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment of the present invention will be described. 1 is a schematic diagram showing a mechanical configuration of an optical writing unit of the laser printer, FIG. 2 is a system block diagram showing an electrical schematic configuration of the laser printer, and FIG. 3 is a diagram showing a scanning state by a 254 dpi laser beam. FIGS. 4A and 4B are explanatory diagrams showing a scanning state by a 508 dpi laser beam. Since the image forming unit can be a conventionally known image forming unit, the description and illustration of the configuration will be omitted.

First, referring to FIG. 1, the mechanical configuration of the optical writing unit of the laser printer will be described together with its operation. The laser beam emitted from the semiconductor laser (LD) 1 is:
The light is converted into parallel light by the collimating lens 2. Next, the excess light is cut by the aperture 3 having the slit portion corresponding to the size of the dot diameter to be formed, and the beam is shaped. The shaped laser beam is first
The laser beam in the main scanning direction (x direction) is condensed on the drum-shaped photoreceptor 5 so as to have a predetermined shape and size by the cylinder lens 4, and the main scanning is performed by the polygon mirror 6 as the first mirror. Scanning is performed in the direction x (the major axis direction of the photoconductor 5). Further, the constant angular velocity movement is made into a constant velocity movement by the pair of Fθ lenses 7, and the field curvature is corrected. Next, the angle of the laser beam is changed by the second mirror 8, and the second
The light is condensed in the sub-scanning direction (y direction) (rotation direction of the photoconductor 5) by the cylinder lens 9, and is irradiated onto the photoconductor 5.

In addition to the laser beam for forming an image, the laser beam reflected by the third mirror 10 from the polygon mirror 6 to obtain a laser beam for synchronization detection once per scan. To the third cylinder lens 1
The signal is sent to the optical fiber 12 through the optical fiber 1. The laser beam sent to the optical fiber 12 is detected by a light receiving block 3 on an engine control board (not shown), and controls the emission start timing of the laser beam for image formation for each scan.

As shown in the system block diagram of FIG. 2, an electrical schematic configuration of the laser printer 21 includes a printer unit 21 and a scanner unit 22. The printer unit 21 includes a control unit 23 and an image forming unit 24. Become. The control unit 23 converts the image read by the scanner unit 22 into a digital code signal, converts the converted digital code signal into data corresponding to dots, stores the converted data in a memory or the like, and changes the pixel density to a desired pixel density. Perform control. The image forming section 24 forms an image based on the dot-corresponding data stored in the control section 23.

Next, the change of the pixel density will be described.

Now, assuming that the scanning frequency of one line in the x direction of the photosensitive member 5 is fv, fv = (dpi / 25.4) × v (1) However, the pixel density is dpi / 25.4.
Is the number of dots per 1 mm.

The rotation speed Rm of the polygon mirror 6 is represented by the following formula: Rm = fv × (60 / n) (2) Here, n is the number of surfaces of the polygon mirror 6, and one line is scanned by one line.

From the above equations (1) and (2), Rm is expressed by the following equation.

Rm = (dpi / 25.4) × (v / n) × 60 (3) ∴dpi∝ (Rm / v) (4) By the way, the photosensitive member 5 shown in FIG. The line write width L is
The effective scanning rate is 100% from one end of one surface of the polygon mirror 6 to the end, but is actually about 70% due to the lens configuration and the like. Assuming that a scanning rate for scanning the effective image width is ER, an image clock w of the effective image width is expressed by the following equation.

W = (fv / ER) × L × (dpi / 25.4) (5) When the time required for one dot is obtained from the above equation (5), (1 / W) = (ER /Fv)÷[L×(dpi/25.4)] (6) Therefore, when these expressions are arranged, the following expressions are obtained.

W = (fv / ER) × L × (dpi / 25.4) = (dpi / 25.4) × (v / ER) × L × (dpi / 25.4) (7) ∝w∝dpi ² × v (8) ∴dpi∝ (Rm / v) ∝√ (w / v) (9) In order to change the pixel density (dpi), the above (1) )
From the relationship of Expression (9) obtained from Expression or Expression (8),
At least two of the pixel clock w, the rotation speed Rm of the polygon mirror 6, and the linear velocity v of the photoconductor 5 must be changed. Therefore, when the laser printer emulates a GL such as an XY plotter (not shown), the control unit 23 changes the rotation number Rm of the polygon mirror and the pixel clock w to change the pixel density to 254 dpi.
The pixel density is changed to an integral multiple of. For example, if the pixel density is 254 dpi, one dot is obtained for a line width of 0.1 mm, and as shown in FIG. 3, one dot is obtained for a line width of 0.1 mm and two dots is obtained for a line width of 0.2 mm. If the dots have a line width of 0.3 mm and are composed of three dots, they can be drawn with the correct line width.

On the other hand, when the minimum line width is set to 0.05 mm and the subsequent line width is set to a multiple of 0.05 mm, the pixel density is set to 508 which is twice 254 dpi.
dpi may be used. Thereby, as shown in FIG.
2 dots for a line width of 0.1 mm, 4 dots for a line width of 0.2 mm, and 6 dots for a line width of 0.3 mm
By using dots, it is possible to draw with a correct line width, and if drawing with one dot, a line width of 0.05 mm can be obtained. Similarly, if you want to further reduce the minimum line width,
If the pixel density is set to 762 dpi, which is three times 254 dpi, or 1016 dpi, which is four times, the former is about 0.03 m
m, the latter can draw a fine line of 0.025 mm.

As described above, in the laser printer, G
When emulation of L is performed, it is possible to specify a line width as faithfully as an XY plotter, thereby improving image quality. However, some users desire the same image as the image output by the conventional printer. In particular, when the user adjusts the line width or the like while viewing the output image, the image may be different from the image that the user is imagined because a faithful image is drawn. Therefore, the control unit 2
3 has the same pixel density as that of the conventional printer, for example, 400 dpi or 600 dpi shown in FIGS.
Pi can be set by the user.

In the above-described embodiment, a description has been given of the case where the line width is 0.1 to 0.3 mm. Although the pixel density is shown as 245 dpi and twice as high as 508 dpi, the same effect can be obtained when the pixel density is tripled and quadrupled as described above. The same effect can be obtained if it is an integer multiple of 254 dpi.

In this embodiment, the change of the pixel density between the inch base and the millimeter base is described. However, any change between the pixel base and the arbitrary pixel density base may be realized by an integral multiple of one dot. Needless to say.

[0028]

As is apparent from the above description, according to the first aspect of the present invention, when the graphic language of the second image forming apparatus is emulated, one dot of the second image forming apparatus is emulated. Since the pixel density of the first image forming apparatus is changed so that the width becomes an integral multiple of the width of one dot of the first image forming apparatus, the line width of the second image forming apparatus is changed. The image can be faithfully reproduced by the first image forming apparatus, and the image quality can be greatly changed.

According to the second aspect of the present invention, the first image forming apparatus scans the laser light from the laser light source and irradiates the photosensitive member with the laser light, and changes the rotation speed of the polygon mirror and the image clock. A second image forming apparatus comprising a laser printer for forming an image by changing an image density;
According to the second aspect of the present invention, the pixel density can be easily changed from the inch-based pixel density of the XY plotter to the millimeter-based pixel density of the laser printer, and an image can be faithfully reproduced.

According to the third aspect of the invention, when the pixel density is changed from the second image forming apparatus to the first image forming apparatus, the first image forming apparatus changes the pixel density to 254 dpi.
Since the pixel density is changed to an integral multiple of the pixel density, the pixel density can be easily changed from an inch base to a millimeter base.

According to the invention described in claim 4, since the control section only controls the pixel density to be changed to an integer multiple of 254 dpi, the present invention can be carried out without greatly improving the conventional printer. The structure is simple and can be provided at low cost.

According to the fifth aspect of the present invention, the control unit includes
Since a pixel density other than an integral multiple of 54 dpi can be selected, an image equivalent to the conventional image can be provided to a user who desires the same image as the conventional image.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a mechanical configuration of an optical writing unit of a laser printer according to an embodiment of the present invention.

FIG. 2 is a system block diagram illustrating an electrical schematic configuration of the laser printer of FIG. 1;

FIG. 3 is an explanatory diagram showing a scanning state by a 254 dpi laser beam in the present invention.

FIG. 4 is an explanatory diagram showing a scanning state by a 508 dpi laser beam in the present invention.

FIG. 5 is an explanatory diagram showing a scanning state using a conventional 400 dpi laser beam.

FIG. 6 is an explanatory diagram showing a scanning state using a conventional 600 dpi laser beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 5 Photoconductor 6 Polygon mirror 21 Printer 22 Scanner part 23 Control part 24 Image forming part

Claims (5)

[Claims] 1. A pixel density changing method for changing a pixel density of a first image forming apparatus to a pixel density of a second image forming apparatus using a graphic language different from that of the first image forming apparatus. When the graphic language of the second image forming apparatus is emulated, the width of one dot of the second image forming apparatus is an integer multiple of the width of one dot of the first image forming apparatus. A pixel density changing method, wherein the pixel density of the first image forming apparatus is changed. 2. The image forming apparatus according to claim 1, wherein the first image forming apparatus scans a laser beam from a laser light source and irradiates the laser beam on a photosensitive member.
2. The pixel according to claim 1, wherein the image forming apparatus comprises an image forming apparatus for forming an image by changing the image density by changing the rotation speed of the polygon mirror and the image clock, and the second image forming apparatus comprises an XY plotter. How to change the density. 3. When the pixel density is changed from the second image forming apparatus to the first image forming apparatus, the first image forming apparatus changes the pixel density to a pixel density that is an integral multiple of 254 dpi. The pixel density changing method according to claim 2, wherein 4. An image having a control unit that scans a laser beam from a laser light source and irradiates the photoreceptor onto a photoreceptor, and changes the number of revolutions of a polygon mirror and an image clock to change an image density to form an image. In the forming apparatus, the control unit may set a pixel density of the printer to 254d when emulating a graphic language such as an XY plotter.
An image forming apparatus which controls so as to change the pixel density to an integral multiple of pi. 5. The image forming apparatus according to claim 1, wherein the control unit can select a pixel density other than an integer multiple of 254 dpi.