JPH01206367A - Laser beam optical device and image forming device - Google Patents

Abstract

PURPOSE:To allow the title device to have large width of printing density as an image forming device of one machine kind by forming integrally a laser beam source, a laser beam shaping device, a beam scanner and a printing density signal output means to a cartridge. CONSTITUTION:As for an optical device 20, at least the laser beam source 25, the laser beam shaping device 26, the beam scanners 27, 30 and the printing density signal output means 40 are formed integrally to a cartridge. In this state, a printing density signal is outputted to a mechanism control circuit 43 containing a microcomputer of an image forming device body part of a printer, etc., and a cartridge corresponding to each printing density is prepared, and replaced with a body part of the image forming device. In such a way, the printing density having width width can be switched as the image forming device of one machine kind.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser beam optical device for scanning and exposing a photoreceptor to laser light to form an image, and an image forming apparatus equipped with the device.

2. Description of the Related Art Electrophotographic printers that use laser light as a light source usually use a laser light source and a laser beam shaping device.

It is equipped with a laser beam optical device consisting of a beam scanning device. In recent years, in such printers, the print density (DPI: dot/1nch) has increased from 100 to 1
000 range, but if the printing density differs, the entire optical device of the laser beam 11 is different, so the printer itself had to be manufactured as a separate model.

Therefore, Japanese Patent Application Laid-Open No. 59-117372 proposes a system that automatically controls the laser beam diameter, laser modulation frequency, polygon mirror rotation speed for beam scanning, and photoreceptor drum rotation speed all at once, making it possible to switch the printing density. A new printer has been proposed.

However, in the prior art described above, the beam diameter, laser modulation frequency, and polygon mirror rotation speed are changed in one laser beam optical device, resulting in a complicated structure and an increase in the size of the entire device. invite. Furthermore, when changing the rotation speed of the polygon mirror, there is a limit to the rotation speed of the motor; increasing the speed will impair durability, while decreasing the speed will cause uneven rotation. For this reason, a single laser beam optical device has a narrow range of allowable range for switching printing densities, and in order to accommodate a wide range of printing densities, it has been necessary to prepare a model for the printer itself. Furthermore, for example, it has been impossible to print ordinary character information at a low density, and to print important character information and graphic information at a high density, while also changing the color.

Therefore, the main object of the present invention is to provide a laser beam optical device and an image forming device that allow a wide range of changes in print density with a single model and that allow the print density to be changed with a simple operation. be.

Furthermore, another object of the present invention is to provide an image forming apparatus that can process multicolor printing at a print density that corresponds to each color.

Means for Solving the Problems In order to solve the above problems, the laser beam optical device according to the first invention includes at least a laser light source, a laser beam shaping device, a beam scanning device, and a print density signal output means. It is characterized by being integrated into a cartridge.

Further, the image forming device according to the second invention includes a plurality of laser beam optical devices in which at least a laser light source, a laser beam shaping device, a beam scanning device, and a printing density signal output means are integrated into a cartridge. It is characterized by being equipped.

Preferably, the image forming apparatus according to the third invention includes a laser beam optical device in which at least a laser light source, a laser beam shaping device, a beam scanning device, and a print density signal output means are integrated into a cartridge. A plurality of laser beam optical devices are provided, and each laser beam optical device is provided with a developing device for developing a latent image formed on the photoreceptor.

In other words, in the present invention, each component of the laser beam optical device is formed into a cartridge, and a print density signal is output to a mechanical control circuit including a microconvenience in the main body of an image forming apparatus such as a printer. Therefore, by preparing a cartridge that corresponds to each print density and replacing it in the main body of the image forming device, it is possible to switch a wide range of print densities as a single model of image forming device, and the cartridges can be easily maintained in the event of a malfunction. All you have to do is replace it. In addition, in an imaging device equipped with multiple laser beam optical devices, it is possible to use different laser beam optical devices or to exchange devices, and it is possible to use different laser beam optical devices with printing densities depending on the type of image. can. Furthermore, if a developer corresponding to each laser beam optical device is installed, arbitrary information can be developed using different (for example, color) toner in each developer.

Example [Refer to the first embodiment, Figures 1 to 4] FIGS. 1 and 2 show a schematic configuration of an electrophotographic printer.

The printer itself is based on the well-known electrophotographic method, and has a photosensitive drum (1) in the center that can be rotated in the direction of arrow (a), and a charged charge-v (2) around the photosensitive drum (1).

Magnetic brush developing device (3), transfer charger (4).

A blade type cleaning device (5) and an eraser lamp (6) are installed. The surface of the photoreceptor drum (1) is first charged to a predetermined potential by a charging charger (2), and is then charged to a laser beam optical device (20), which will be described in detail below.
An electrostatic latent image is formed by irradiation with laser light, and the electrostatic latent image is made into a developed image by adhesion of toner by a developing device (3). The toner image is transferred to a transfer charger (
The image is transferred by the electric discharge in step 4) and fixed by heating in the fixing device (11). The copy paper is then discharged onto a paper discharge tray (12).

On the other hand, the photosensitive drum (1) rotates in the direction of arrow (a) even after the transfer, the residual toner is completely removed by the cleaning device (5), the residual charge is erased by the eraser lamp (6),
Prepare for the next copy.

The laser beam optical device (20) is a cartridge equipped with a case (21) having a handle (22), and is removable from the front using a slide rail (not shown) provided at a predetermined position of the printer main body. There is.

Here, the laser beam optical device (20) will be explained in detail with reference to FIGS. 3 and 4.

The laser beam optical device (20) includes a laser diode (25) as a light source, a collimator lens (26), a polygon mirror (27) and its rotation drive motor (28), and an fθ lens (29) inside a case (21). ), a reflective mirror (30), and an SOS sensor (31).

A laser beam with a certain spread emitted from a laser diode (25) is made into parallel light by a collimator lens (26), deflected by a polygon mirror (27), and then sent to an fθ lens (29) and a reflecting mirror (30). The photoreceptor drum 1) is exposed to light in its axial direction, that is, along the main scanning line (L). The SOS sensor (31) has a function to correct recording start position errors for each scan due to errors in mirror surface division of the polygon mirror (27), and uses the photoreceptor drum to detect the image start position in the main scanning direction. (1) It is installed at a position equivalent to the main scanning line (L) on the front surface.

In the above configuration, the relationship between the print density and each optical element can be expressed by the following equation. However, it is assumed here that the printing density is the same in the main scanning direction and the sub-scanning direction.

Beam diameter (d): d=cI/D
...■Polygon mirror rotation speed (R): R" Cx・D・V/N ...■Modulation frequency (f
): f-C,・F-D"・V/N... ■Optical ff1(E): E=C4・P,・N/(F-V)
...■In addition, C+-Ca "Proportionality constant D: Print density■ = Photoconductor circumferential speed N: Number of polygon mirror surfaces F: fθ Lens focal length Pa ' From the laser diode output formula 0, print density (D) Based on this, the beam diameter (d) is determined.

Inside the laser beam optical device (20), for example, the beam diameter (d) can be changed by changing the beam expander or prism, or by changing the focal pressure of the collimator lens (26)!
This can be achieved by changing 1t(F).

In this embodiment, the print density (D) can be changed by replacing the laser beam optical device (20). Therefore, if the circumferential speed (V) of the photoreceptor is constant, the polygon mirror rotation speed (
R), number of polygon mirror surfaces (N).

All or any of the modulation frequency (f), fθ lens focal length (F) may be changed in accordance with the printing density (D) of each laser beam optical device (20).

When the number of polygon mirror surfaces (N) is determined from the above equation 0, the polygon mirror rotation number (R) is determined according to the print density (D). Then, from equation (2), if the modulation frequency (f> is constant, fθ lens focal pressure m (F) is determined. Here, the amount of light on the photoreceptor drum (1) is determined by the printing density (
In order to keep D) constant when changing D), the laser output (Po) can be changed as is clear from equation (2).

On the other hand, modulation frequency (f) and fθ lens focal length (F
) is constant, then according to equation (2), in order to change the printing density (D>), it is sufficient to change the number of polygon mirror surfaces (N) in each laser beam optical device (20).

However, as mentioned above, the focal length (F) of the fθ lens (29) and the number of surfaces (N) of the polygon mirror (27)
In order to change each laser beam optical device (20)
Multiple fθ lenses (29
) and a polygon mirror (27), which is very expensive.

Therefore, from the formulas ■ and ■, the polygon mirror rotation speed (R)
By changing the modulation frequency (f), the printing density (D>) can be easily changed while the fθ lens focal length (F) and the number of polygon mirror surfaces (N) remain constant.

Polygon mirror rotation speed (R) is determined by printing density (D) from formula 0.
is proportional to. Then, the modulation frequency (f) is proportional to the square of the print density (D) according to equation (2).

As described above, if the laser beam optical device (20) is prepared for each printing density (D>), it becomes possible to switch the printing density (D) simply by replacing this optical cartridge.

As mentioned above, each laser beam optical device (20)
In order to correspond to changes in printing density (D), it is most practical to change the polygon mirror rotation speed (R) and modulation frequency (f). In this embodiment, an oscillation circuit (40) consisting of a basic clock generation circuit (40a) and a frequency dividing circuit (40b) is provided in the laser beam optical device (20), and this increases the rotational speed of the polygon mirror (27). (R), which controls the modulation frequency (f) of the laser diode (25).

Specifically, as shown in FIG. 4, the frequency data output from the oscillation circuit (40) is transmitted to the laser beam optical device (20).
), which rotates the polygon mirror motor (28) at a predetermined rotation speed (R) set for each laser beam optical device (20). Further, the modulation frequency data (f) output from the oscillation circuit (40) is input to the image control section of the mechanical control circuit (43) including a microcomputer on the printer main body side, where the character generator (44)
> is combined with the image data from 〉 and input to the laser diode drive circuit (42) as LD data (pulse width and pulse on/off), and the laser diode (25)
emit modulated light.

On the other hand, another signal that is input from the laser beam optical device (20) to the mechanical control circuit (43) provided on the printer body side is that when the polygon mirror (27) reaches a certain rotation speed, the drive circuit There is a lock signal outputted from (41) and a 5O3 (synchronization) signal outputted from SOS sensor (31) for determining the image scanning start position. Furthermore, the mechanical control circuit (43) includes a paper sensor (45) installed in the paper feed cassette (10) shown in FIGS. 1 and 2 to determine the image area.
The paper size signal from

Note that the basic clock generation circuit (40a) may be provided in the mechanical control circuit (43) on the blink body side. In addition to the polygon mirror (27), a galvanometer mirror, a porographic scanner, etc. can be used as the beam scanning device.

By the way, the printing density (D) is determined not only by the number of rotations of the polygon mirror (R) as described above, but also by the number of polygon mirror surfaces (N).
It changes even if you change it. In other words, if the number of polygon mirror surfaces (N) is increased in order to achieve a predetermined printing density (D), the polygon mirror rotation speed (R) may be lowered. When using ball bearings, the polygon mirror rotation speed (R) is 10. The limit is approximately OOOrpm, and as the print density (D) increases, the permissible range is exceeded. In such a case, increasing the number of polygon mirror surfaces (N) will increase the rotation speed (R) to 10.000 rpm.
It can be set within a permissible range of m or less.

As shown in Fig. 4, the modulation frequency data (f) and polygon mirror rotation frequency data (R) from the laser beam optical device (20) are transmitted to the mechanical control circuit (43) on the main body side.
), and the printing density (D) of the laser beam optical device (20) is shown on the main body side using these two data. Other signals may be used as the signal indicating the printing density (D). By instructing the print density (D) to the printer main body side, the image area, in other words, the number of dots for a specified paper size and the number of dots from the scanning start point to the end point are clarified.

The print density signal may also be input to the character generator (44) via the mechanical control circuit (43) so that a pattern corresponding to the print density (D) is output.

Further, in the above description, it is assumed that the print density in the main scanning direction and the print density in the sub-scanning direction are the same, but at least one of them can be changed independently. That is, if the above-mentioned equations (1) to (2) are considered separately into the printing density (DM) in the main scanning direction and the printing density (D, ) in the sub-scanning direction, the following is obtained.

Beam diameter in main scanning direction (dM) ' dM=cs/DM
...■ Beam diameter in sub-scanning direction (ds) 'ds-C
-/Da...■Polygon mirror rotation speed (R): R==cy・D,・V/N...
■Modulation frequency (f): f=c,・F'DM'Ds・V/N =C1・F-DM-R...■In addition, from the C6~Co" proportionality constant■,■formula, the main scanning direction , printing density in the sub-scanning direction (D
The beam diameters (dM) and (ds) in the main scanning direction and sub-scanning direction are determined based on M) and (D. Both beam diameters (
When dM) and (dl) are different, the laser beam pattern becomes an ellipse.

Then, the printing density in the sub-scanning direction (D3) is determined by the polygon mirror rotation speed (R) and the number of polygon mirror surfaces (N) from the formula (■).
determined by Note that, as in the case described above, the circumferential speed (V) of the photoreceptor is constant. Therefore, to change the printing density (D3) in the sub-scanning direction, the polygon mirror rotation number (R
) and/or the number of polygon mirror surfaces (N).

On the other hand, the print density (DM) in the main scanning direction depends on the modulation frequency (f), fθ lens focal length (F), and polygon mirror rotation speed (R) according to equation 0. Therefore, if the polygon mirror rotation speed (R) is changed when changing the printing density (D3) in the sub-scanning direction, the printing density (D3) in the main scanning direction (
DM) will also be changed accordingly. In order to avoid this and maintain the print density (DM) in the main scanning direction at a predetermined value, the modulation frequency (f) and/or the fθ lens focal length (F) may be changed. For example, when changing the polygon mirror rotation speed (R) to double in order to double only the printing density (DS) in the sub-scanning direction, if the modulation frequency (f>) is also doubled, the main The print density (DM) in the scanning direction does not change.

Conversely, when changing only the print density (DM) in the main scanning direction, it is sufficient to change only the modulation frequency (f), for example. In this case, the print density (D3) in the sub-scanning direction is not changed.

From the above, the printing density (DM) in the main scanning direction and sub-scanning direction
, (os) can also be changed independently.

Hereinafter, print density in the main scanning direction and sub-scanning direction <DM).

An example of the circuit configuration within the laser beam optical device (20) in the case where (Ds) is changed independently will be explained based on FIG. Components in this figure that are similar to those in FIG. 4 described above are given the same reference numerals, and only the different points will be explained.

In the configuration of FIG. 5, in addition to the configuration of FIG. 4,
A polygon mirror surface number data generation circuit (47) is provided within the laser beam optical device (20). This circuit (47
) indicates the number of polygon mirror surfaces (N) of the laser beam optical device (20) to the mechanical control circuit (43) on the printer main body side.

The mechanical control circuit (43) recognizes the print density (DM) in the main scanning direction from the polygon mirror rotation speed data (R) and laser diode modulation frequency data (f) from the oscillation circuit (40). On the other hand, the print density in the sub-scanning direction (
D3) as polygon mirror rotation frequency data (R), number of polygon mirror surfaces (N) and mechanical control circuit (43
) is recognized based on the photoreceptor circumferential speed data (V) stored within the range. Then, communication is carried out with the character generator (44) according to these printing densities (DM) and (DI) to create desired LD data.

With this configuration, the main scanning direction.

It becomes possible to independently control the print density (1)1) and (Ds) in the sub-scanning direction. For example, in the facsimile 03 standard, the main scanning direction is 8 pixels/mm, but the sub-scanning direction is 3.58 lines/mm, and there is information about 7.7 lines/mm. If you prepare a compatible laser beam optical system (W(20)), you can obtain an output image according to the information without image editing. When using the same laser beam optical device (20), the printing density (DM) in the main scanning direction is the same, but the printing density (D,) in the sub-scanning direction is different, so the image expands and contracts in the sub-scanning direction. Even in such a case, a laser beam optical device (2
0), image expansion and contraction can be prevented.

As described above, in the first embodiment, if cartridges with various print densities are prepared, the print density can be changed by simply replacing them, and the print density can be changed as a single printer model. It can have a large width. Furthermore, even in the event of a failure, the cartridge can be replaced, making maintenance easy.

[Refer to the second embodiment and FIG. 6] Next, a second embodiment of the present invention will be described.

This second embodiment includes a plurality of sets of the laser beam optical device (20) and the electrophotographic image forming section in the first embodiment to enable multicolor image formation.

FIG. 6 shows this second embodiment, in which the electrophotographic section (A),
(A') are arranged in series.

In the figures, the same reference numerals are given to the same members as in the first embodiment, and all the parts in the second stage electrophotographic section (A') are given the same reference numerals (゛). The copy paper is conveyed in the direction of arrow (c) as shown by the two-dot chain line, and the second electrophotographic section (A) is placed over the image transferred in the first electrophotographic section (A).
In A'), the images are transferred one on top of the other.

In this second embodiment, the laser beam optical system El (
20) and (20') are each replaceable, and it is also possible to replace them with laser beam optical devices of other printing densities. For example, the first stage laser beam optical device (20
) is 200DPI, the first stage developer (3) contains black toner, and the second stage laser beam optical device (
20') is 300 DPI and the second stage developer (3') contains red toner, a 200 DPH image is formed in black and a 300 DPH image is formed in red. That is, lines that require high resolution can be formed in red, and normal characters can be formed in black, for example.

Here, when the laser beam optical devices (20) and (zo') are replaced with each other, the 200DPI image is red and the 30DPI image is red.
A 0DPI image will be formed in black. By separately preparing a laser beam optical device with a different printing density (for example, 400 DPI) and replacing it, an image with that printing density can be formed in black or red.

[Third Embodiment, See FIG. 7] Next, a third embodiment of the present invention will be described with reference to FIG. 7.

In this third embodiment, one photoreceptor drum (1) is surrounded by one
Stage charger (2) and laser beam optical device (
20), a developing device filled with developer containing color toner (
3), second stage charger (2゛) and laser beam optical device (20'), developing device (3') filled with developer containing black toner, transfer charge ~ (4), cleaning device (5) ) and an eraser lamp (6).

In this device, a toner image is formed by a laser beam optical device (20') and a developing device (3') in an overlapping manner on the toner image formed by a laser beam optical device (20) and a developing device (3), and then transferred. The toner image is transferred onto the copy paper in one transfer step by the charger (4).

Laser beam optical device (20) in this third embodiment
, (20') are the same as those in the second embodiment, and although detailed explanation thereof will be omitted, the third embodiment can also obtain the same effects as the second embodiment.

[Other Examples] Note that the laser beam optical device and image forming apparatus according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

For example, as in the second and third embodiments, there is not only a configuration in which each image forming element is arranged to form a two-color image, but also a configuration in which the printing density is simply set for one set of image forming elements. Different or the same laser beam optical devices may be installed and selectively operated to perform image formation. In such cases, if one laser beam optical device is used frequently, it is recommended to discard that optical device and replace it with the one that is used less frequently, and install a new optical device in its place. It is possible.

As is clear from the above description, the present invention provides at least a laser light source and a laser beam shaping device.

Since the beam scanning device and the print density signal output means are integrated into a cartridge, if cartridges with various print densities are prepared, it is possible to switch the print density by simply replacing them. As an image forming device, it is possible to have a wide range of printing density. Furthermore, even in the event of a failure, the cartridge can be replaced, making maintenance easy. In particular, switching the printing density is effective in multicolor printers equipped with a plurality of laser beam optical devices.

[Brief explanation of the drawing]

1 to 4 show a first embodiment of the present invention.
The figure is a schematic configuration diagram of the printer, the second figure is a perspective view, and the third figure is a schematic diagram of the printer.
The figure is a perspective view of the laser beam optical device, and FIG. 4 is a block diagram of the control circuit. FIG. 5 is a block diagram of a control circuit as a modification of the first embodiment. FIG. 6 is a schematic diagram of a printer according to a second embodiment of the present invention, and FIG. 7 is a schematic diagram of a printer according to a third embodiment of the present invention. (3)...Developer, (20)...Laser beam optical device, (21)...Case, (25)...Laser diode, (26)...Collimator lens, (27)
... Polygon mirror, (2B) ... Mirror motor, (29) ... fθ lens, (40) ... Oscillator circuit, (41) ... Mirror drive circuit, (42) ...
・Laser diode drive circuit, (43)...Mechanical control circuit, (47)...Polygon mirror surface number data generation circuit. Patent applicant Takeshi Morishita, patent attorney representing Minolta Camera Co., Ltd. - Figure 1 Figure 2

Claims (1)

Claims: 1. A laser beam optical device characterized in that at least a laser light source, a laser beam shaping device, a beam scanning device, and a print density signal output means are integrated into a cartridge. 2. An image forming apparatus characterized by comprising a plurality of laser beam optical devices in which at least a laser light source, a laser beam shaping device, a beam scanning device, and a printing density signal output means are integrated into a cartridge. 3. While having a plurality of laser beam optical devices in which at least a laser beam source, a laser beam shaping device, a beam scanning device, and a printing density signal output means are integrated into a cartridge, each laser beam optical device An image forming device comprising a developing device for developing a latent image formed on a photoreceptor.