JP3019598B2 - Image recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for guiding a plurality of beams to respective scanning lines on a latent image carrier such as a photoreceptor and forming a latent image on the latent image carrier to make the latent image visible. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus that forms an image, and more particularly to an image recording apparatus that realizes both a high-speed scanning mode and a high-quality scanning mode.

[0002]

2. Description of the Related Art In an image recording apparatus such as a copying machine or a printer, a type in which a latent image is formed on a photosensitive member serving as a latent image carrier using a laser beam has been frequently used. Such an apparatus irradiates a laser beam oscillated from a laser oscillating unit onto a rotating polygon mirror that rotates at a high speed, and deflects and moves the laser beam along the axial direction of the photoconductor according to the rotation of the rotating polygon mirror to form an image. An electrostatic latent image is formed by forming an image on each scanning line of the photoconductor via a lens.

[0003] In this type of image recording apparatus, high-speed printing and high-quality printing are required to be realized. As a prior art corresponding to such a demand, a photoconductor is irradiated with a plurality of laser beams. Exposure is already provided. For example, as shown in JP-A-56-110960, a high-speed printing is performed by simultaneously scanning the photosensitive member with a plurality of independently modulatable laser beams.
-74758 or JP-A-61-212818.
As disclosed in Japanese Unexamined Patent Application Publication No. H11-264, there is a device in which a plurality of laser beams are modulated with the same image signal, and a photosensitive member is scanned and exposed a plurality of times to prevent deterioration in image quality.

[0004]

However, in the prior art, only devices that satisfy the sole requirements of high-speed printing or high-quality printing have been provided, respectively. In order to meet the demand, it is necessary to prepare individual devices, and accordingly, there is a technical problem that the installation space and the maintenance cost for a plurality of devices increase. In order to solve such technical problems, a device technology capable of realizing high-speed printing and a device technology capable of realizing high-quality printing are combined, and for example, the relative position of each scanning line on a photoconductor scanned by a plurality of laser beams respectively. It is conceivable to achieve high-quality printing by matching the positions, realize high-speed printing by shifting each scanning line to each other, and switch between both printing modes as necessary.
Changing the relative scanning position of multiple laser beams alone would result in a difference in the exposure amount of each scanning line in high-speed printing or high-quality printing. The technical problem that it is difficult to maintain good quality at all times remains.

The present invention has been made to solve the above technical problems, and is based on the premise that a latent image is formed on a latent image carrier by a plurality of beams, and image quality is improved. It is an object of the present invention to provide an image recording apparatus in which a high-speed scanning mode and a high-quality scanning mode can be selected as needed while always maintaining good conditions.

[0006]

That is, the present invention provides:
As shown in FIG. 1, a plurality (for example, two) of beam generating means 1a and 1b for generating a beam corresponding to an image signal, and a plurality of beams Ba and B from each of the beam generating means 1a and 1b.
b to a corresponding scanning line on the latent image carrier 2 and a plurality of beams Ba and Bb guided by the beam guide 3 to form an electrostatic latent image on the latent image carrier 2. Image forming process means 4 for forming and visualizing this electrostatic latent image
Scanning mode selecting means 5 for selecting one of at least one high-quality scanning mode and at least one high-speed scanning mode.
A relative scanning position changing unit 6 for changing a relative scanning line position of a plurality of beams Ba and Bb guided by the beam guiding unit 3 according to the selected scanning mode; Image signal editing and distributing means 7 for editing and distributing the image signal supplied to each of the beam generating means 1a and 1b, and the beam intensity and latent image generated by the beam generating means 1a and 1b according to the selected scanning mode. Carrier 2
Parameter changing means 8 for changing at least one of the parameters relating to the above image forming process.

In such technical means, individual devices may be used as the beam generating means 1a and 1b, or a common device capable of generating respective beams by a plurality of image signals may be used. Good. Further, the beam generating means 1a, 1b may generate a light beam, or may generate an ion beam. Further, the latent image carrier 2 includes a beam generation unit 1.
A photoreceptor or a dielectric is used depending on the types of the beams a and 1b.

The beam guiding means 3 is of a type in which the beams Ba, Bb from the beam generating means 1a, 1b are moved and scanned along the scanning line of the latent image carrier 2, and at least the beams Ba, Bb are provided. It is necessary to provide a deflecting means for deflecting and moving Bb and an image forming means for forming a beam deflected by the deflecting means on a scanning line of the latent image carrier 2. A means for correcting the inclination of the deflection surface of the beam path regulating means such as a mirror or the deflecting means may be provided. On the other hand, beams Ba and Bb from the beam generating means 1a and 1b
Without moving and scanning the beam Ba, B in each pixel unit.
b is directly guided on the latent image carrier 2,
An image forming means for forming a beam on the scanning line of the latent image carrier 2 may be provided.

Further, as the image forming process means 4, a charging means for pre-charging the latent image carrier 2 and a latent image formed by beam scanning from the beam generating means 1a and 1b are usually visualized. A developing unit, but a charging unit is not always necessary for a type in which a latent image can be formed only by the beams from the beam generating units 1a and 1b.
In the case of developing a plurality of latent images of different colors with different colors, a plurality of developing means are required. However, the developing method may be all negative developing methods, or the former may be a negative developing method. The latter stage can be appropriately selected, for example, by adopting a positive developing method. Further, in an image forming process in which a plurality of latent images are all developed by a negative developing method, it is preferable to provide a recharging unit from the viewpoint of avoiding a decrease in the latent image contrast due to a decrease in dark potential.

Further, the scanning mode selecting means 5 selects a high image quality scanning mode and a high speed scanning mode. Each of the modes is divided into a plurality of resolutions or the relative scanning position is adjusted appropriately. It can be selected as appropriate, for example.

The relative scanning position changing means 6 includes beam generating means 1a, 1a in accordance with each scanning mode.
b to change the scanning position of the beam, change the rotational speed of the latent image carrier 2 to change the scanning position in the rotational direction of the latent image carrier, or change the rotational speed of the deflecting means to change the latent image carrier. The latent image carrier 2 is changed by changing the scanning area range in the axial direction of the body (in other words, the beam diameter for each pixel), or variably adjusting the position of a component (mirror, lens, etc.) of the beam path regulating means.
Can be changed or the design can be appropriately deflected. In particular, in the high image quality scanning mode, when beams from a plurality of beam generating means 1a and 1b are overwritten on the same scanning line by the same image signal,
It is possible to further improve the sharpness of an image, and it is also possible to use a plurality of beam generating means 1 with the same image signal.
When the beams from a and 1b are written in a slightly shifted form, it is possible to reduce the pitch unevenness between the scanning lines.

The image signal editing and distributing means 7 includes:
The input serial or parallel image signal is edited according to the scanning mode, and the respective beam generating means 1a, 1
b, for example, a configuration in which an image signal editing and distributing circuit dedicated to high-quality scanning mode and an image signal editing and distributing circuit dedicated to high-speed scanning mode are switched and selected according to the scanning mode. do it.

The parameter changing means 8 should be appropriately selected as long as it can appropriately change parameters (beam intensity, charge amount of the charging means, etc.) which become the recording image density of the scanning line according to the scanning mode. Can be.

[0014]

According to the above technical means, when one of at least one of the high-quality scanning mode and the at least one high-speed scanning mode is selected by the scanning mode selecting means 5, the relative scanning position is set. The changing means 6 changes the relative scanning line positions of the plurality of beams Ba and Bb guided by the beam guiding means 3 according to the selected scanning mode, and the image signal editing and distributing means 7 performs the selected scanning. The image signal supplied to each beam generating means 1a, 1b is edited and distributed according to the mode, and the parameter changing means 8 further controls the beam intensity generated by the beam generating means 1a, 1b according to the selected scanning mode. And latent image carrier 2
Change at least one of the parameters for the imaging process above. For this reason, on the latent image carrier 2,
A latent image based on an image signal corresponding to the scanning mode is formed at a relative scanning line position corresponding to the scanning mode, and this latent image is visualized according to an image forming process appropriately adjusted in parameters.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. FIG. 2 shows an embodiment of a laser printer to which the present invention is applied.
The recording is performed at a density of pi (dot / inch). In the figure, reference numeral 10 indicates that the surface is 127 mm.
(5 inches) / sec.
1 is a charging corotron for pre-charging the photosensitive drum, 12 is a laser scanning unit for writing a first latent image and a second latent image on the charged photosensitive drum 10, and 13 is a photosensitive drum 10
A first developing device for developing the first latent image written thereon, 1
Reference numeral 4 denotes a second developing device that develops the second latent image written on the photosensitive drum 10, and reference numeral 15 denotes that the polarity of each toner image on the photosensitive drum 10 is made uniform and the charge on the photosensitive drum 10 is removed. A transfer corotron 16 for transferring a toner image on the photosensitive drum 10 to a recording sheet 17;
18 removes the charge on the recording paper 17 after the transfer step,
A neutralizing corotron 19 for removing the recording paper 17 electrostatically attracted to the photosensitive drum 10, a cleaner 19 for removing residual toner on the photosensitive drum 10, and a neutralizing lamp 20 for removing residual charges on the photosensitive drum 10. In this embodiment,
The first and second developing devices 13 and 14 are not always used, but a latent image written by a plurality of beams B1 and B2 is developed by one developing device (for example, the second developing device 14) as described later. It also employs a simple image forming process.

In this embodiment, the laser scanning unit 12 includes a first semiconductor laser 31 for writing a first latent image in a unit case 30 and a second semiconductor laser 31 for writing a second latent image in the unit case 30. 32 and each semiconductor laser 3
Collimator lenses 33 and 34 for collimating the beams B1 and B2 from the laser beams 1 and 32; a polygon mirror 35 for distributing the beams B1 and B2 from the semiconductor lasers 31 and 32 over the scanning range of the photosensitive drum 10; An fθ lens (corresponding to an imaging lens) 36 for correcting the beams B1 and B2 distributed by the mirror 35 so as to draw a linear locus corresponding to a scanning line on the photosensitive drum 10, and a beam B1 passing through the fθ lens 36 , B2, which are interposed in the optical paths of the light-receiving elements, and reflect the beams B1, B2 toward the respective scanning line positions of the photosensitive drum 10.
Are stored in a predetermined positional relationship. FIG.
The reflection mirrors 38 and 40 are cylindrical mirrors and have a function of correcting the tilt of the polygon mirror 35. Reference numerals 41 and 42 denote optical windows for sealing which are respectively attached to the light outlets of the unit case 30. Further, in this embodiment, the interval between the beams B1 and B2 on the photosensitive drum 10 is 5
It is set to 0.7 mm (799/400 inches).

FIG. 3 shows a drive control system of the laser printer in this embodiment. In the figure, reference numeral 50 denotes the entire laser printer based on a print mode (a high-speed print mode and a high-quality print mode in this embodiment) selected by a mode selection switch (not shown) and image data. A printer controller 51 for controlling the sequence; a laser controller 51 for driving and controlling the first and second semiconductor lasers 31 and 32 based on a power control signal and a video signal from the printer controller 50; A polygon motor control device that rotates the motor 53 for driving the polygon mirror 35 based on the rotation speed instruction signal from the printer 50. The polygon motor control device 54 controls the motor 55 for driving the photosensitive drum 10 based on the rotation speed instruction signal from the printer control unit 50. It is a drum motor control device that is driven to rotate.
Note that the polygon mirror 35 and the photosensitive drum 10 each perform PPL speed control based on a rotation speed instruction signal using an output of a pulse generator attached to a rotating shaft.

Here, a specific example of the printer control unit 50 is shown in FIG. In the figure, reference numeral 501 denotes a selector for distributing image data to one of two systems according to a print mode. This selector 501 is a high-speed print data editing and distribution circuit 5 for high-speed print mode.
02 for the high-quality printing mode, and to the high-quality printing data editing and distribution circuit 503.
After editing video signals of even and odd lines different from each other for 1 and 32, the video signals are distributed and transmitted at appropriate timings. On the other hand, the high-quality print data editing distribution circuit 503 includes first and second video signals. After editing the same video signal for the semiconductor lasers 31 and 32, the video signal is distributed and transmitted at appropriate timing. The semiconductor laser 32
The video signal is delayed until the latent image formed on the photosensitive drum 10 by the semiconductor laser 31 substantially reaches the position of the beam 32.

Reference numeral 504 denotes a power control in which light power control signals of the first and second semiconductor lasers 31 and 32 for each print mode are stored in a readable manner in advance, and a power control signal corresponding to the print mode is generated. In this embodiment, the relative light amount of the semiconductor lasers 31 and 32 is adjusted according to the distance between the beams B1 and B2, and the power control signal in the high-quality print mode is set in the high-speed print mode. Is set to の of the power control signal.

Further, reference numeral 505 denotes a polygon motor rotation speed instruction signal generation signal which stores a rotation speed instruction signal of the polygon motor 53 for each print mode in a readable manner and generates a polygon motor rotation speed instruction signal corresponding to the print mode. This is a table, and in this embodiment, a common rotation speed instruction signal is determined for any of the print modes. If there is a print mode in which the dot size (sub-scan density) of each pixel is changed,
The corresponding rotation speed instruction signal may be stored in advance so that switching can be selected.

Further, reference numeral 506 denotes a drum motor rotational speed instruction signal for storing a rotational speed instruction signal of the drum motor 55 for each print mode in a readable manner in advance, and generating a drum motor rotational speed instruction signal corresponding to the print mode. This is a generation table. In this embodiment, the drum motor rotation speed instruction signal in the high quality print mode is set to １ ／ of that in the high speed print mode.

Next, the operation of the laser printer according to this embodiment will be described. ◎ High-speed printing mode If the high-speed printing mode is selected by operating a mode selection switch (not shown), the printer control unit 50 generates various control signals corresponding to the high-speed printing mode as described above, and The signal is sent to the laser controller 51, the polygon motor controller 52, and the drum motor controller 54. Then, as shown in FIG. 5 (a), the image signals in which the beams B1 and B2 from the respective semiconductor lasers 31 and 32 are different even and odd numbers are alternately written on the photosensitive drum 10, and a latent image having a predetermined resolution is obtained. This latent image is developed by the second developing device 14. In this case, both beams are 1000
Each beam is scanned by the photosensitive drum 10
The top is scanned at a pitch of 128 μm (2/400 inch). Beam B2 is 400 ms (40
Write an image signal delayed by 0 scan).

High-quality print mode On the other hand, if the high-quality print mode is selected by operating the mode selection switch, the printer control unit 50 generates various control signals corresponding to the high-quality print mode as described above, The various control signals are sent to a laser controller 51, a polygon motor controller 52, and a drum motor controller 54. In this case, the scanning of the beams B1 and B2 does not change at 1000 times / sec, but the speed of the photosensitive drum 10 is reduced by 1 / sec.
2, and the charging potential is increased accordingly. And
The image signal of the beam B2 is 799 ms with respect to the beam B1.
(799 scans) Delayed output. Then, FIG.
As shown in (b), the beams B1 and B2 from the respective semiconductor lasers 31 and 32 overwrite the same image signal on the photosensitive drum 10 to form a latent image having a predetermined resolution (400 dpi). The latent image is developed by the second developing device 14.
At this time, since the same image signal is overwritten, not only the sharpness of the recorded image is improved, but also the beams B1, B
The light amount of No. 2 is １ ／ of that in the high-speed print mode. However, since the latent image having the same latent image contrast as that in the high-speed print mode is formed by overwriting, this latent image was developed by the second developing device 14. However, the recorded image density is maintained at the same level as in the high-speed print mode. Further, by controlling the potential of the developing device, the line width of the recorded image can be adjusted. Further, in this high-quality print mode, in order to eliminate pitch unevenness between the scanning lines, the rotation speed of the photosensitive drum 10 is slightly changed so that the beams B1 and B2 are changed as shown in FIG. The same image signal may be written in a slightly shifted state. In addition, if writing is performed while slightly shifting the writing timing of the beams B1 and B2 in the main scanning direction, pitch unevenness between pixels can be improved.

In the above embodiment, two semiconductor lasers 31 and 32 are used. However, the present invention is not limited to this. From the viewpoint of reducing the number of parts,
For example, as shown in FIG. 6, a semiconductor laser array 60 that can modulate each of the beams B1 and B2 with a plurality of image signals may be used.

FIG. 7 shows an example of various latent image forming states by three systems of beams B1, B2, and B3 each having three polygon motors rotating at the same speed using, for example, three semiconductor lasers. It is another embodiment shown. FIG.
Is, for example, a resolution of 600 dpi (dots / 1) in the main scanning direction.
(In inches), image signals different for each of the beams B1, B2, and B3 are transmitted at a density of 200 dpi in the sub-scanning direction, and the respective beams are projected onto the photosensitive drum 10 by about 142 μm in the sub-scanning direction.
A high-speed printing mode in which scanning and printing are sequentially performed at intervals of (1/600 inch) is shown. In this case, the polygon motor speed is 1, the process speed is 1, and the light amount of one semiconductor laser is 1. The scanning of the beams B2 and B3 by the polygon motors is performed such that each beam scans a predetermined position with respect to the latent image of the beam B1 formed earlier.
Synchronization is performed based on the amount of movement of the photosensitive drum 10, and the image signal is delayed.

FIG. 3B shows a resolution 3 in the main scanning direction.
A high-speed printing mode in which image signals different for each of the beams B1, B2, and B3 are transmitted at a density of 300 dpi in the sub-scanning direction at 00 dpi, and sequentially arranged and scanned to perform printing. The light amount of one semiconductor laser may be set as shown in each drawing.

FIG. 3C shows a resolution of 1200 dpi.
Indicates a high-speed printing mode in which different image signals are transmitted and printed for each of the beams B1, B2, and B3. In this case, the polygon motor speed, the process speed, and the light amount of one semiconductor laser are shown respectively. It may be set as follows.

FIG. 3D shows a high-quality print mode in which the same image signal is transmitted for each of the beams B1, B2, and B3 at a resolution of 300 dpi and each scan line on the photosensitive drum 10 is overwritten. In this case, the polygon motor speed, the process speed, and the light amount of one semiconductor laser may be set as shown in the drawing.

FIG. 5E shows a high-quality print mode in which the same image signal is transmitted for each of the beams B1 and B3 at a resolution of 400 dpi and written with a slight shift. The process speed and the light amount of one semiconductor laser may be set as shown in the drawing.

FIG. 4F shows a similar resolution of 400 dpi.
Shows an example in which the same image signal is sent out for each of the beams B1, B2, and B3, and writing is performed with a slight shift. One scan line image is formed on the upper surface by sequentially combining the two beams. By performing the scanning in this manner, the scanning line pitch on the photosensitive drum 10 can be changed, and moire can be prevented. At this time, if the start timing of the main scanning is finely adjusted for each beam, the dot pitch in the main scanning direction can be changed, so that moiré can be more effectively prevented.

In these examples, the scanning density is adjusted in the main scanning direction by changing the modulation frequency of the beam.
The scanning density adjustment in the sub-scanning direction is performed by changing one or both of the speed of the polygon motor and the moving speed (process speed) of the photosensitive drum 10.

Further, the photosensitive drum 1 in a dry copying machine or the like
In the above embodiment, when the rotation speed (process speed) or the light amount of the photosensitive drum 10 is changed in the same manner as the developing conditions based on the charging potential of 0, the latent image potential, and the developing device potential, the charging potential and The developing parameters such as the potential of the developing device are changed so that the latent image formed on the photosensitive drum 10 is correctly visualized.

In the second embodiment, individual polygon motors are scanned for each beam in synchronization with each other. However, as in the first embodiment, each polygon motor is scanned using one polygon motor. Can be scanned simultaneously. In this case, it is necessary to adjust the distance between the beams according to the scanning mode and the scanning density so as to have a predetermined relationship. For example, the angle of the mirror or the angle of the transmission transparent glass plate is set on each optical path of the beams B2 and B3. Means may be provided for shifting the beam by changing, and adjustment may be performed according to each mode. At this time, fine adjustment of the speed of the photosensitive drum 10 may be used in combination with the first embodiment, so that the relative positions of the beams have a predetermined relationship.

[0034]

As described above, according to the present invention, the latent image writing pattern by the beam on the latent image carrier is switched in accordance with the high-speed scanning mode or the high-quality scanning mode. Since the image forming process adapted to the mode can be realized, it is possible to perform high-speed scanning and high-quality scanning while always maintaining a good recording image density. Therefore, the high-speed scanning mode and the high-quality scanning mode can be compatible with one apparatus, and the installation space and maintenance cost of two apparatuses conventionally required can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an image recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a laser printer to which the present invention is applied.

FIG. 3 is a block diagram illustrating a drive control system of the laser printer according to the embodiment.

FIG. 4 is a block diagram illustrating a specific example of a printer control unit according to the embodiment.

FIG. 5 is an explanatory diagram showing an example of a beam writing pattern in each print mode of the laser printer according to the embodiment.

FIG. 6 is an explanatory view showing a modification of the laser printer according to the embodiment of FIG. 2;

FIG. 7 is an explanatory diagram showing an operation example of each print mode according to another embodiment of the laser printer to which the present invention is applied.

[Explanation of symbols]

1a, 1b: beam generating means, 2: latent image carrier, 3: beam guiding means, 4: image forming process means, 5: scanning mode selecting means, 6: relative scanning position changing means, 7: image signal editing and distribution Means, 8 ... Parameter changing means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/44 G03G 15/04 G03G 21/00

Claims (1)

(57) [Claims] A plurality of beam generating means (1a, 1b) for generating a beam corresponding to an image signal, and a plurality of beams (Ba, Bb) from each of the beam generating means (1a, 1b) are transferred to a latent image carrier. (2) Beam guide means (3) leading to the corresponding scanning line above, and a plurality of beams (Ba, Bb) guided by the beam guide means (3), rest on the latent image carrier (2). An image forming apparatus for forming an electrostatic latent image and visualizing the electrostatic latent image;
A scanning mode selecting unit (5) for selecting one of at least one high-quality scanning mode and at least one high-speed scanning mode, and guided by a beam guiding unit (3) according to the selected scanning mode. Scanning position changing means (6) for changing the relative scanning line positions of the plurality of beams (Ba, Bb) and the beam generating means (1a, 1b) according to the selected scanning mode. Image signal editing and distributing means (7) for editing and distributing the image signal;
According to the selected scanning mode, the beam generating means (1a,
Beam intensity generated in 1b) and latent image carrier (2)
An image recording apparatus comprising: a parameter changing unit (8) for changing at least one of the parameters relating to the image forming process described above.