JP3441310B2 - Multi-beam scanner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam scanning device that scans a recording medium such as a photoconductor with a plurality of laser beams, and more particularly, a beam pitch of each laser beam on the recording medium has a predetermined value. The present invention relates to a multi-beam scanning device having a control system for controlling the beam.

[0002]

2. Description of the Related Art In a conventional laser printer or an apparatus such as a digital copying machine having a laser printer as a recording unit, generally, a single laser beam emitted from a single laser light source is used as a rotary polygon mirror (polygon mirror). ) And the like are deflected at a constant angular velocity, and an image is formed by scanning the recording medium at a constant velocity via the f-θ lens. By the way, in order to increase the recording speed and perform high-speed recording and printing in an apparatus that forms an image with such a single laser beam, it is necessary to increase the transfer speed of the image information signal for modulating the laser beam, or It is necessary to increase the rotation speed of the rotary polygon mirror. However, the amount of increase in these speeds is naturally limited, and it has been extremely difficult to improve the recording speed with a single laser beam.

Various methods have conventionally been developed to overcome such drawbacks. For example, JP-A-57-673
Japanese Patent Publication No. 75 (see Japanese Patent Publication No. 1-43294, hereinafter referred to as "First Publication") and Japanese Patent Laid-Open No. 61-245174.
Japanese Patent Publication (see Japanese Examined Patent Publication No. 6-94215, hereinafter referred to as "second
Japanese Unexamined Patent Application Publication No. 2004-242242), a method of forming an image by simultaneously scanning a recording medium with a plurality of laser beams that are modulated based on different image information signals is described. In these methods, since images for a plurality of lines are simultaneously formed by a plurality of laser beams, even if the transfer speed of the image information signal or the rotation speed of the rotary polygon mirror is not changed,
It is possible to easily improve the recording speed by the number of laser beams. As a configuration of a laser light source that emits a plurality of laser beams, a plurality of laser light emitting elements arranged in an array in one chip (see the first publication) and a plurality of laser light emitting elements are independent. It is known to be incorporated into an optical unit (see the second publication).

In the structure of the laser light source in which a plurality of laser light emitting elements are arranged in an array in one chip as described in the above-mentioned first publication, the beam interval between the laser beams does not easily change, and the laser It has an advantage that the light source can be easily downsized. However, on the other hand, when the light emission output is increased for high-speed recording, there is a drawback that crosstalk in which light emission of one laser light emitting element in one chip affects other laser light emitting elements is likely to occur. . Also, considering the occurrence of crosstalk, the beam intervals must be separated by at least a few lines. If the beam intervals between the laser beams are separated in this way, the laser beam scanning backward with respect to the moving direction of the recording medium. However, there is a drawback that the image forming process becomes complicated because it is necessary to jump over the image portion formed by the laser beam which is being scanned in advance.

On the other hand, in the structure of the laser light source in which a plurality of laser light emitting elements are independently incorporated in the optical unit as described in the above-mentioned second publication, a large output is possible and the laser light emitting element is also provided. There is no problem of crosstalk between them, and there is an advantage that the wavelength can be shortened for high-definition recording. On the other hand, however, it is difficult to fix the beam spacing between laser beams to a predetermined value because multiple laser light emitting elements are incorporated into the optical unit independently of each other, and the environmental temperature, heat generation of the laser light emitting element itself, etc. This has the drawback that the beam spacing between the laser beams easily changes.

Generally, a laser beam scanning optical system is configured as a magnifying optical system of several tens of times from a laser light emitting element to a recording medium such as a photosensitive member. Therefore, the positioning accuracy between the laser light emitting elements is submicron accuracy. Is required. However, it is actually impossible to secure such mounting accuracy, and in a multi-beam scanning device using a plurality of laser light emitting elements, the beam pitch on the recording medium is controlled to be a predetermined value. Control system is required.

FIG. 6 is a diagram showing a conventional multi-beam scanning device described in the second publication. As shown in FIG. 6, in the conventional multi-beam scanning device, semiconductor lasers 61a and 61b independently incorporated in an optical unit and laser beams (diffused light) emitted from the semiconductor lasers 61a and 61b are converted into parallel light. Lenses 62a and 62b for
And the lenses 62a and 62b according to the input electric signal.
Of the two laser beams that have respectively passed through the lenses 62a and 62b and the actuators 63a and 63b that drive each of them and adjust the deflection angle thereof, and separate a part of each laser beam from the optical path toward the photosensitive drum 67. And a beam splitter 64. Further, in the optical path from the beam splitter 64 to the photosensitive drum 67, a rotary polygon mirror 65 that deflects the laser beam combined by the beam splitter 64 toward the photosensitive drum 67.
And an f-θ lens 66 for focusing the laser beam deflected by the rotary polygon mirror 65 on the surface of the photosensitive drum 67. Further, in the vicinity of the beam splitter 64, a split detector 68 including a plurality of light receiving elements that receive the laser beams separated by the beam splitter 64, and two laser beams based on the output from the split detector 68 are detected. Differential devices 69a and 69b for controlling the actuators 63a and 63b are provided so that the beam pitch on the surface of the photosensitive drum 67 becomes a predetermined value.

In the conventional multi-beam scanning device, the beam splitter 64 separates a part of the laser beam toward the photosensitive drum 67, and the position of each separated laser beam is detected by the split detector 68. And
Based on the output from the split detector 68, the differentials 69a and 6a
9b controls the actuators 63a and 63b,
The image forming position of each laser beam on the surface of the photosensitive drum 67 moves. Therefore, the beam pitch of the laser beam on the recording medium such as the photosensitive drum 67 can be accurately maintained, and the accuracy of the beam pitch can be improved even when the two semiconductor lasers 61a and 61b are independently incorporated in the optical unit. be able to.

By the way, in the conventional multi-beam scanning device described in the second publication, a split detector 68 as shown in FIG. 7 is used as a sensor for detecting the position of the laser beam. As shown in FIG. 7, the split detector 68 is composed of four light receiving elements 70a to 70d, which is twice the number of laser beams. In FIG. 7, 71a and 71b represent the spots of the two laser beams separated by the beam splitter 64. As shown in FIG. 7, the laser beams 71a and 71b are controlled by a control system including a sensor 68 and differential devices 69a and 69b, of which the center of the laser beam 71a is located between the light receiving element 70a and the light receiving element 70b. And the laser beam 71b is positioned so that its center lies between the light receiving element 70c and the light receiving element 70d.

[0010]

As described above, in the conventional multi-beam scanning device described in the second publication, a sensor for detecting the position of the laser beam has twice the number of laser beams. Number of photo detectors are required. Further, when the laser beam moves beyond the detection range of two light receiving elements adjacent to each other on the sensor, there is a problem that the position of the laser beam cannot be detected.

The present invention has been made in view of the above points, and a sensor can be configured with a smaller number of light receiving elements than in the conventional device, and a laser beam can be significantly generated on the sensor. An object of the present invention is to provide a multi-beam scanning device capable of surely and promptly performing positioning control of a laser beam even when it is displaced.

[0012]

According to the present invention, a plurality of laser light sources for emitting laser beams, and laser beams emitted from the laser light sources provided between the laser light sources and a recording medium are provided. Deflection means for deflecting toward the recording medium so as to scan on the recording medium, and a part of each of the laser beams provided between the laser light source and the deflection means are separated from an optical path toward the recording medium. Separation means, imaging position moving means provided between the laser light sources and the separation means for moving the imaging position of the laser beams on the recording medium, and the separation means separated by the separation means. Detection means for detecting the position of each laser beam from a part of each laser beam, and a beam of each laser beam on the recording medium based on the result detected by the detection means. A control means for controlling the image-forming position moving means so that the pitch becomes a predetermined value, and the detecting means is a light receiving element of a number larger than the number of laser beams emitted from each of the laser light sources, The plurality of light receiving elements arranged in parallel at a pitch optically corresponding to the beam pitch of the laser beam on the recording medium, the control means, among the plurality of light receiving elements of the detection means The image forming position moving means is controlled so that the respective laser beams are positioned between adjacent light receiving elements, and when the image forming position moving means is controlled by the control means, On the recording medium, each of at least two positions formed between adjacent ones of the at least three light-receiving elements of the detection unit that are arranged in parallel is arranged in front of the recording medium. The positioning of each laser beam is sequentially performed by shifting the lighting timing of each laser beam emitted from each laser light source so that each of at least two laser beams separated by a beam pitch is positioned. The present invention provides a multi-beam scanning device.

According to the present invention, the width of the light receiving element provided on the outermost side of the plurality of light receiving elements is larger than the width of the light receiving elements provided inside the other light receiving elements. A multi-beam scanning device is provided.

Further, according to the present invention, the control means controls the image forming position moving means based on a difference between output values of the light receiving elements adjacent to each other constituting the detecting means, and the first control section, A second control unit for controlling the image forming position moving unit based on information obtained from all of the plurality of light receiving elements constituting the detection unit, and these first control unit and second control unit are provided. There is provided a multi-beam scanning device characterized by controlling the image forming position moving means by switching.

According to the present invention, the detecting means for detecting the position of each laser beam is composed of the number of light receiving elements which is larger than the number of laser beams emitted from the laser light source, and these light receiving elements are provided for each laser beam. Since they are arranged side by side at a pitch optically equivalent to the beam pitch on the recording medium, it is necessary to use as many light receiving elements as the number of laser beams as in the conventional multi-beam scanning device shown in FIG. No, but a smaller number, eg 1 than the number of laser beams
The detection means can be composed of a large number of light receiving elements.

According to the present invention, the width of the light receiving element provided on the outermost side of the plurality of light receiving elements constituting the detecting means in the juxtaposed direction is the same as the width of the light receiving element provided on the other inner side. The information obtained from all of the plurality of light receiving elements and the first control unit that controls the image forming position moving means based on the difference between the output values of the light receiving elements adjacent to each other that are wider than the width and constitute the detection means Second for controlling the image forming position moving means based on the second
Since the image forming position moving means is controlled by switching between the control unit and the control unit, the laser beam positioning control can be performed reliably and promptly even when the laser beam is largely displaced from the predetermined position to be positioned. You can

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIGS. 1 to 3 are views showing a first embodiment of a multi-beam scanning device according to the present invention. First, the entire multi-beam scanning device will be described with reference to FIG. As shown in FIG. 1, the multi-beam scanning device includes semiconductor laser diodes (laser light sources) 1a and 1b which are modulated according to an image information signal and emit light in a blinking manner.
A lens 2a for collimating a laser beam (diffused light) emitted from the semiconductor laser diodes 1a, 1b,
2b (imaging position moving means) and a deflection angle actuator (imaging position moving means) 3 that drives each of the lenses 2a and 2b in accordance with an input electric signal to adjust the deflection angle thereof.
a, 3b and 2 which have passed through the lenses 2a, 2b, respectively
There is provided a half mirror (separation means) 4 which combines the two laser beams and separates a part of each laser beam from the optical path toward the photosensitive drum 7.

A polygon mirror (deflecting means) 5 for deflecting the laser beam combined by the half mirror 4 and a laser deflected by the polygon mirror 5 are provided in the optical path of the laser beam from the half mirror 4 to the photosensitive drum 7. F-θ for focusing the beam on the surface of the photosensitive drum 7
And a lens 6 are provided. The polygon mirror 5
Is rotated at high speed by a polygon motor (not shown).

On the other hand, in a part of the optical path of the laser beam separated by the half mirror 4, a sensor (detection means) 8 composed of a plurality of light receiving elements for receiving each separated laser beam, and from the sensor 8 are provided. A positioning controller (control means) 9 is provided for controlling the deflection angle actuators 3a and 3b so that the beam pitch of the two laser beams on the surface of the photosensitive drum 7 becomes a predetermined value on the basis of the output of.

Next, the sensor 8 of the multi-beam scanning device will be described with reference to FIG. As shown in FIG. 2, the sensor 8 includes three light receiving elements 8 which is one more than the number of laser beams.
a to 8c, and each light receiving element has a rectangular light receiving surface having the same area. The light receiving element 8
a to 8c are juxtaposed at a pitch optically equivalent to a beam pitch of 0.043 mm of the laser beam formed on the surface of the photosensitive drum 7. In FIG. 2, reference numerals 10a and 1
0b indicates the spots of the two laser beams separated by the half mirror 4. As shown in FIG. 2, the laser beams 10a and 10b are controlled by the positioning controller 9. Among them, the laser beam 10a has its center between the light receiving elements 8a and 8b, and the laser beam 10b is Positioning is performed so that its center is between the light receiving elements 8b and 8c.

Next, the positioning controller 9 of the multi-beam scanning device will be described with reference to FIG. As shown in FIG. 3, the positioning controller 9 controls the beam pitches of the two laser beams on the surface of the photosensitive drum 7 based on the output from the sensor 8 shown in FIG. is there. That is, the positioning control unit 9 includes a signal processing unit 11 for converting a signal output from the sensor 8 and an instruction value from the outside into a control signal, a deflection angle actuator 3a,
A positioning mechanism 13 for positioning the laser beam by adjusting the deflection angles of the lenses 2a and 2b by driving 3b.
And a control unit 12 arranged between the signal processing unit 11 and the positioning mechanism 13 to control the positioning mechanism 13 based on a control signal output from the signal processing unit 11. The control unit 12 is composed of, for example, a low-pass filter, an integrator, a phase compensator, a power amplifier, and the like, and based on an instruction value from the outside (see “0: center” in FIG. 3), for example, on the sensor 8. A control system is configured so that the difference between the output values from the two light receiving elements adjacent to each other is 0 so that the center of the laser beam is positioned between the two light receiving elements adjacent to each other.

Next, the operation of the first embodiment of the present invention having such a configuration will be described.

As shown in FIG. 1, laser beams (diffused light) emitted from the semiconductor laser diodes 1a and 1b.
Passes through the lenses 2a and 2b whose deflection angles are adjusted by the deflection angle actuators 3a and 3b, and becomes parallel light deflected at an appropriate deflection angle. Lenses 2a, 2b
The laser beam that has passed through is combined by the half mirror 4 so that the beam pitch of the laser beam on the surface of the photosensitive drum 7 becomes the same value (0.043 mm) as the printer resolution. The combined laser beam is deflected at a constant angular velocity by a polygon mirror 5 which rotates at a high speed by a polygon motor (not shown), and the laser beam deflected at a constant angular velocity passes through an f-θ lens 6 to form a laser beam on the surface of the photosensitive drum 7. An image is formed on the surface of the photosensitive drum 7 at the same time by scanning at a constant speed in the main scanning direction (direction of arrow S) and combining the laser beams.

On the other hand, a part of the laser beam separated by the half mirror 4 is made incident on a sensor 8 composed of a plurality of light receiving elements 8a to 8c, and based on an output from the sensor 8, a positioning control section 9 outputs 2 The deflection angle actuators 3a and 3b are controlled so that the beam pitch of one laser beam on the surface of the photosensitive drum 7 becomes a predetermined value.

That is, in the positioning control section 9 shown in FIG. 3, the signals output from each of the light receiving elements 8a to 8c of the sensor 8 shown in FIG. 2 and the instruction value from the outside (see "0: central" in FIG. 3). ) Is converted into a control signal by the signal processing unit 11, and based on the converted control signal, the control unit 12 controls the positioning mechanism 13 so that the difference in the amount of light received between the light receiving elements adjacent to each other becomes zero. Is controlled. Then, finally, the deflection mechanism actuators 3a and 3b are driven by the positioning mechanism 13 to move the lenses 2a and 2b.
The deflection angle of b is adjusted to an appropriate value.

Next, the control by the control unit 12 will be specifically described with reference to FIG. For example, the control unit 12 outputs the output value based on the amount of light received by the light receiving element 8a on the sensor 8 and the light receiving element 8b.
The positioning mechanism 13 is controlled so that the difference from the output value based on the amount of received light is zero, and the center of the laser beam 10a is positioned between the light receiving elements 8a and 8b. Similarly, the positioning mechanism 13 is controlled so that the difference between the output value based on the amount of light received by the light receiving element 8b on the sensor 8 and the output value based on the amount of light received by the light receiving element 8c is controlled to 0, whereby the laser beam The center of 10b is positioned between the light receiving elements 8b and 8c. Here, the light receiving element 8
Since a to 8c are juxtaposed at a pitch that optically corresponds to the beam pitch on the surface of the photosensitive drum 7, the laser beams 10a and 10b are positioned on the sensor 8 so that the surface of the photosensitive drum 7 is positioned. Laser beam 10 on
The image forming positions of a and 10b also have a predetermined beam pitch of 0.043.
They are positioned so that they are spaced by mm.

It should be noted that in FIG. 2, 2 is placed on the light receiving element 8b.
The two laser beams 10a and 10b are depicted as being positioned together, but when the control unit 12 performs positioning control, these laser beams 10a and 10b are
10b does not light up at the same time. That is, for example, the positioning of each laser beam is sequentially performed on a trial basis using a period other than the period for image recording, or the period during which the laser beam is not lit during image recording is found and the positioning of each laser beam is sequentially performed. By doing so, the lighting timings of the two laser beams 10a and 10b are shifted.

As described above, according to the first embodiment of the present invention, the plurality of light receiving elements 8a to 8c on the sensor 8 are optically arranged at the beam pitch at which the laser beam is positioned on the surface of the photosensitive drum 7. By arranging in parallel at a corresponding pitch, like the conventional multi-beam scanning device shown in FIG. 6,
It is possible to use a smaller number, for example, 1 than the number of laser beams, without using a light receiving element that is twice the number of laser beams.
The sensor 8 can be composed of as many light receiving elements as possible.

In the first embodiment of the present invention, the image formation is performed by using two laser beams, but it is also possible to form the image by a larger number of laser beams. In this case, the number of light receiving elements forming the sensor 8 can be reduced more effectively. Also,
As the imaging position moving means, the lenses 2a and 2b used in the existing scanning optical system are the deflection angle actuator 3
Although the structure driven by a and 3b is adopted, an optical element such as a reflection mirror or parallel glass is newly added in the optical path between the semiconductor laser diodes 1a and 1b and the half mirror 4 to drive these optical elements. By doing so, the imaging position of the laser beam on the surface of the photosensitive drum 7 may be moved.

[Second Embodiment] Next, a second embodiment of the multi-beam scanning device according to the present invention will be described with reference to FIGS. The second embodiment of the present invention is different from the second embodiment except that the structures of the sensor and the positioning control unit are different.
Others are substantially the same as those of the first embodiment shown in FIGS. 1 to 3. In the second embodiment of the present invention, FIGS.
The same parts as those of the first embodiment shown in FIG.

First, a sensor according to the second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 4, the sensor 14 includes five light receiving elements 14a to 14e, and the same light receiving elements 14b to 14d as in FIG.
The width of the light receiving element 14b in the juxtaposed direction is outside the
Light receiving elements 14a, 1 having a width larger than the width of 14d in the juxtaposed direction.
4e is provided.

The light-receiving elements 14a and 14e are not provided separately from the light-receiving elements 14b and 14d, but rather the light-receiving elements 14a and 14b and the light-receiving elements 14d and 14d.
14e are integrally formed, and light receiving elements 14d and 14e that are integrated with light receiving elements 14a and 14b that are integrated
You may make the width | variety of the parallel installation direction large. In addition, these light receiving elements 14a and 14e (or the light receiving element 1 integrated with
Light receiving elements 14d and 14e integrated with 4a and 14b)
The width of the sensor 1 in the juxtaposition direction is large enough to correspond to the moving range in which the laser beam is supposed to move. For example, when the light receiving elements are juxtaposed at 0.043 mm intervals, the sensor 1
It is preferable that the width of the entire No. 4 in the juxtaposed direction is about 1 mm.

Next, the positioning controller in the second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 5, the positioning control unit 16 uses the sensor 1 shown in FIG.
Based on the output from 4, the beam pitch of the two laser beams on the surface of the photosensitive drum 7 is controlled to be a predetermined value. That is, the positioning control unit 16 drives the deflection angle actuators 3a and 3b and the signal processing unit 17 that converts the signal output from the sensor 14 and the instruction value from the outside into a control signal, and the lenses 2a and 2b.
A positioning mechanism 22 for adjusting the deflection angle of the laser beam to position the laser beam, and a positioning mechanism 22 arranged between the signal processing unit 17 and the positioning mechanism 22 based on a control signal output from the signal processing unit 17. Control unit 18 for controlling
And have.

Further, in the control unit 18, a precise positioning control unit (first control unit) 19 for controlling the positioning mechanism 22 based on the difference between the output values of the light receiving elements adjacent to each other on the sensor 14, and the sensor Coarse positioning control section (second control section) 20 for controlling the positioning mechanism 22 based on information obtained from all the plurality of light receiving elements on the sensor 14, and information obtained from all of the plurality of light receiving elements on the sensor 14. The control mode determination unit (determination unit) 21 determines whether to select the precise positioning control unit 19 or the rough positioning control unit 20 based on the above.

Next, the operation of the second embodiment of the present invention having the above structure will be described.

As shown in FIG. 5, in the control unit 18 of the positioning control unit 16, first, similarly to the control unit 12 shown in FIG. 3, positioning is performed based on the difference between the output values of the light receiving elements adjacent to each other on the sensor 14. The precise positioning control unit 19 that controls the mechanism 22 and the coarse positioning control unit 20 that controls the positioning mechanism 22 based on the information obtained from all of the plurality of light receiving elements on the sensor 14 are controlled by the control mode determination unit 21. Switching is performed based on the information obtained from all of the plurality of light receiving elements on 14.

The coarse positioning control section 20 is for moving the position of the laser beam, which is largely deviated from the predetermined position to be positioned, to a large amount and to move it quickly to the vicinity of the predetermined position. The coarse positioning control unit 20 firstly, for example, first detects a plurality of light receiving elements 14a to 14e on the sensor 14.
It is determined that the laser beam is present on the light receiving element having the largest output value by comparing the output values of the above. Next, the positioning mechanism 22 is controlled by determining in which direction the laser beam should be moved to a predetermined position to be positioned based on the position of the laser beam thus determined.
In FIG. 4, for example, the light receiving element 14b and the light receiving element 14c
When the laser beam 15a is positioned between the position and the position and the output value of the light receiving element 14d is the largest, the rough positioning control unit 20 causes the positioning mechanism 22 to move the laser beam upward in the drawing. Control.

As another method, the coarse positioning control section 20 outputs the output of one of the light receiving element groups in the two light receiving element groups divided by the light receiving elements on which the laser beam should be positioned on the sensor 14 as a boundary. The positioning mechanism 22 may be controlled by using the difference between the sum of the values and the sum of the output values of the other light receiving element group as information obtained from all the plurality of light receiving elements. That is, in FIG. 4, for example, when the laser beam 15a is positioned between the light receiving elements 14b and 14c, the sum of the output values of the light receiving elements 14a and 14b and the sum of the output values of the light receiving elements 14c, 14d and 14e. Then, the positioning mechanism 22 is controlled based on this difference.

Here, the control mode determination unit 21 is, for example,
The output values of a plurality of light receiving elements on the sensor 14 are compared with each other, it is determined that the laser beam is present on the light receiving element having the largest output value, and the laser beam thus determined is determined between the light receiving elements to be positioned. The fine positioning control section 19 is selected when the light receiving elements are on both sides of the above, and the rough positioning control section 20 is selected otherwise. Then, either control signal output from the fine positioning control unit 19 or the rough positioning control unit 20 based on such selection is input to the positioning control mechanism 22.

As described above, according to the second embodiment of the present invention, the plurality of light receiving elements 14a to 14e on the sensor 14 are provided.
Of the light receiving elements 14a, 14e provided on the outermost side
(Or the width of the light receiving elements 14d and 14e integrated with the integrated light receiving elements 14a and 14b) in the juxtaposed direction is made larger than the width of the other light receiving elements 14b to 14d in the juxtaposed direction. It is possible to easily detect where the laser beam is even when the laser beam is largely deviated from the predetermined position to be positioned on the sensor 14. Therefore, reliable positioning control of the laser beam can be performed. In addition, when the width of the light receiving elements 14a and 14e in the juxtaposed direction is made larger than the moving range of the laser beam, the position of the laser beam to be positioned can be detected regardless of where the laser beam is positioned. More reliable positioning control of the beam can be performed.

Further, according to the second embodiment of the present invention, the fine positioning controller 19 or the rough positioning controller 20 is selected according to the position of the laser beam on the sensor 14 to control the laser beam positioning. By performing the above, even if the laser beam is largely deviated from the predetermined position to be positioned, the coarse positioning control unit 20 can promptly detect the position of the laser beam, and the laser beam can be reliably and promptly detected. Positioning control can be performed.

In the second embodiment of the present invention, the positioning control unit 16 controls based on the output from the sensor 14 shown in FIG. 4, but the sensor 8 shown in FIG. The same control may be performed based on the output. Further, the control mode determination unit 21 is not arranged at the subsequent stage of the fine positioning control unit 19 and the coarse positioning control unit 20 as shown in FIG. 5, but is provided with the signal processing unit 17 and the fine positioning control unit 19 or the coarse positioning control unit. You may make it arrange | position between 20 and.

By using the multi-beam scanning device according to the first or second embodiment of the present invention, an inexpensive laser printer, a digital copying machine or the like having high performance can be provided.

[0045]

As described above, according to the present invention,
The detecting means can be constituted by a smaller number of light receiving elements than the conventional multi-beam scanning device. Further, even if the laser beam is largely deviated from the predetermined position to be positioned, the laser beam positioning control can be performed reliably and promptly.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a multi-beam scanning device according to the present invention.

FIG. 2 is a diagram showing a configuration of a sensor of the multi-beam scanning device shown in FIG.

3 is a block diagram showing a configuration of a positioning control unit of the multi-beam scanning device shown in FIG.

FIG. 4 is a diagram showing a configuration of a sensor in a second embodiment of a multi-beam scanning device according to the present invention.

FIG. 5 is a block diagram showing a configuration of a positioning control unit in a second embodiment of a multi-beam scanning device according to the present invention.

FIG. 6 is a diagram showing a conventional multi-beam scanning device.

7 is a diagram showing a configuration of a sensor of the conventional multi-beam scanning device shown in FIG.

[Explanation of symbols]

1a, 1b Semiconductor laser diode 2a and 2b lenses 3a, 3b Deflection angle actuator 4 half mirror 5 polygon mirror 6 f-θ lens 7 Photosensitive drum 8,14 sensor 8a to 8c, 14a to 14e Light receiving element 9,16 Positioning controller Laser beams 10a, 10b, 15a, 15b 11, 17 Signal processing unit 12, 18 Control unit 13,22 Positioning mechanism 19 Precision positioning controller 20 Coarse positioning controller 21 Control mode determination unit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaki Takahashi 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center Co., Ltd. (72) Inventor Hideki Ito Small, Saiwai-ku, Kawasaki-shi, Kanagawa Muko Toshiba Town 1 Co., Ltd. within the Toshiba Research and Development Center (72) Inventor Yuji Suzuki Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture 1 Kobayashi Research and Development Center (72) Inventor Ken Komiya Kawasaki, Kanagawa Prefecture 70, Yanagimachi, Sachi-ku, Tokyo (72) Inventor, Toshiba Yanagimachi Plant (72) Koji Tanimoto, 70, Yanagi-cho, Sachi-ku, Kawasaki, Kanagawa Prefecture Incorporated, Toshiba Yanagimachi Plant (72) Inventor, Takashi Shiraishi 70 Yanagimachi, Sachi-ku, Shizu, Ltd. Inside the Yanagimachi Plant of Toshiba Corporation (56) References JP-A-3-225315 (JP, A) JP-A-2-160212 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) G02B 26/10 B41J 2/44 H04N 1/113

Claims (10)

(57) [Claims] 1. A plurality of laser light sources for emitting laser beams, said laser light sources provided between said laser light sources and a recording medium so that said laser beams emitted from said laser light sources are scanned on said recording medium. Deflection means for deflecting toward the recording medium; separation means provided between the laser light sources and the deflection means for separating a part of each laser beam from an optical path toward the recording medium; and each laser light source. And an image forming position moving means for moving the image forming position of each of the laser beams on the recording medium, and a part of each of the laser beams separated by the separating means. Detecting means for detecting the position of each laser beam, and based on the result detected by the detecting means, the beam pitch of each laser beam on the recording medium is set to a predetermined value. Thus, the control means for controlling the image forming position moving means, the detection means is a number of light receiving elements greater than the number of laser beams emitted from each of the laser light sources, It is composed of a plurality of light receiving elements arranged in parallel at a pitch optically equivalent to the beam pitch on the recording medium, the control means, of the plurality of light receiving elements of the detection means of the adjacent light receiving elements The image forming position moving means is controlled so that the respective laser beams are positioned in between, and when the image forming position moving means is controlled by the control means, the detecting means is continuously operated. At least two positions formed between adjacent ones of at least three light-receiving elements arranged in parallel are separated by the beam pitch on the recording medium. A multi-beam characterized by sequentially positioning each laser beam by shifting the lighting timing of each laser beam emitted from each laser light source so that each of at least two laser beams is positioned. Scanning device. 2. The multi-beam scanning device according to claim 1, wherein the number of the light receiving elements is one more than the number of laser beams emitted from each of the laser light sources. 3. A light-receiving element provided on the outermost side of the plurality of light-receiving elements has a width in the juxtaposed direction larger than a width in the juxtaposed direction of other light-receiving elements provided inside. The multi-beam scanning device according to claim 1 or 2. 4. The multi-beam scanning device according to claim 3, wherein a width of the light receiving element provided on the outermost side in the juxtaposed direction is larger than a moving range of the laser beam. 5. The control means controls the image forming position moving means on the basis of a difference between output values of light receiving elements adjacent to each other constituting the detecting means.
5. The multi-beam scanning device according to any one of 4 to 4. 6. The control means includes a first control portion for controlling the image forming position moving means based on a difference between output values of light receiving elements adjacent to each other, which constitutes the detecting means, and the detecting means. On the basis of information obtained from all of the plurality of light receiving elements constituting the detection means, a second control section for controlling the image forming position moving means based on information obtained from all of the plurality of light receiving elements constituting And a determination unit that determines which of the first control unit and the second control unit is selected, the determination unit being adjacent to each other in which the laser beam is to be positioned among the plurality of light receiving elements. When it is determined that the laser beam is present on at least one of the matched light receiving elements, the first control unit is selected, while the laser beam is placed on any of the adjacent light receiving elements. When it is determined that there is no The multi-beam scanning device according to any one of claims 1 to 4, wherein the second control unit is selected in the case of the above. 7. The second control unit uses, as the information obtained from all of the plurality of light receiving elements, information on which light receiving element of the plurality of light receiving elements has a laser beam. 7. The multi-beam scanning device according to claim 6. 8. The multi-beam scanning device according to claim 7, wherein the second control unit determines that the laser beam is present on the light receiving element having the largest output value among the plurality of light receiving elements. . 9. The second control unit uses, as information obtained from all of the plurality of light receiving elements, one of the two light receiving element groups divided based on the light receiving element on which the laser beam is to be positioned. 7. The multi-beam scanning device according to claim 6, wherein a difference between a sum of output values of the element group and a sum of output values of the other light receiving element group is used. 10. The multi-beam scanning device according to claim 6, wherein the determination unit determines that the laser beam is present on the light receiving element having the largest output value among the plurality of light receiving elements.