JP3489707B2 - Optical scanning device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device in which a modulated beam is made incident on the deflecting surface of a polygon mirror.

[0002]

2. Description of the Related Art Heretofore, various methods and apparatuses have been known for forming a multicolor image on a recording medium by transferring an image on a photoconductor exposed by a plurality of different light sources to a transfer body. Since these are multicolor images, first, the process of exposing and developing the photoconductor with the light source of the laser light in which the data is modulated on the photoconductor corresponding to a plurality of colors and then transferring it to the transfer body is performed a plurality of times. The image of each color is transferred to the same position on the transfer body. Therefore, unless these are transferred to the same position on the transfer body, the reproducibility of the image is deteriorated, and the contrast is poor and a blurred image is formed.

The reason why images from different light sources are not transferred to the same position on the photoconductor is that the photoconductor is tilted with respect to the transfer body due to an error in manufacturing and assembling the mechanical parts, the magnification of the optical system is changed, and the optical system is tilted. Changes in the characteristics of the optical system, deviations in the exposure timing of the optical system that exposes the latent image on the surface of the photoconductor, and because the light emission positions of multiple light sources are different, the exposure position on the photoconductor is shifted. .

Among the causes described above, there is known a technique for improving the image shift by mechanically adjusting and correcting the tilt of the photoconductor with respect to the transfer body, and the problem is solved. You can Further, the change in the characteristics of the optical system due to the magnification and the inclination of the optical system is caused by the f-θ characteristic of the f-θ lens, the mirror angle on the optical path, and the same mirror.
The latent image is exposed on the surface of the photoconductor because it is affected by the position , the optical path length after the polygon mirror, the error of the optical housing, etc., and the image transferred to the recording medium through the photoconductor is displaced in the scanning direction. It is necessary to provide an electrical time lag in the exposure timing of the optical system to be adjusted and set so that the image is transferred to the same position on the photoconductor.

From such a point of view, conventionally, as shown in FIG. 8, one polygon mirror 2 and two semiconductor lasers 1A and 1B are used, and a reflecting surface 2 of the polygon mirror 2 is used.
The beams SLo and SRo are made incident on c and 2a, and the emission of the semiconductor laser is detected by the two detectors by the beam detectors 6 and 9. Therefore, the exposure timing can be adjusted by performing the heading of the modulated signal after scanning an appropriate time lag from these detectors and scanning the scanned surfaces 4Aa, 4Ba.

[0006]

However, the above-mentioned conventional technique uses a photodetector based on a beam detector.
I use one. In FIG. 8, the detector 6 detects the beam SLd reflected by the reflecting surface 2c, and the synchronizing signal 10
(FIG. 7) is transmitted, and an appropriate time lag (delay time) t1
Is provided and the modulated beam SLs is sent as n1. Therefore, the reflection surface 2c reflects the laser light to the detector 6 in the forward direction of rotation, and a detection portion (non-image area) for detecting that the reflection surface enters the irradiation area of the semiconductor laser 1A, and this detection portion. After that, a scanning portion (image area) for receiving the modulated beam and scanning the surface to be scanned 4Aa is required.

If the areas of the detecting portion and the scanning portion of the reflecting surface are not sufficient, the detector 6 cannot detect the laser light sufficiently or the surface to be scanned 4Aa by the modulated beam.
If the scanning is insufficient, the image formation on the photoconductor is hindered. Therefore, in the detector 6, the position, the angle toward the reflecting surface, etc. are adjusted so that the detecting portion is located at the leading portion in the rotation direction of the reflecting surface of the polygon mirror, and the scanning portion is located subsequently.

When the adjustment of the mounting position of the detector 6 is completed, the time lag t1 is set by a circuit (not shown). If the time lag t1 is too large, the reflecting surface 2c of the polygon mirror 2 will have a useless margin, and the polygon mirror 2 is set to a size not too large in order to increase the size. Then, after the modulated beam n1, as shown in FIGS. 7A and 7B, the modulated beam is n after a delay time t1 from the synchronization signal 10 by the reflecting surfaces 2d to 2a.
2, n3 ... Are transmitted.

Next, the reflecting surface 2c rotates counterclockwise in FIG. 8, and the detecting portion and the scanning portion of the reflecting surface 2c enter the irradiation area of the semiconductor laser 1B in the same order. Also in that region, the reflection surface 2c has the semiconductor laser 1
The surface to be scanned 4Ba provided corresponding to the surface to be scanned 4Aa to be scanned by A must also be similarly scanned by the synchronized modulated beam. Therefore, also in that area, the detector 9 for detecting whether or not the reflecting surface 2c has entered the area needs to be provided.

Since the detecting portion and the scanning portion of the reflecting surface 2c enter the irradiation area of the semiconductor laser 1B in the same order, the detector 9 is adjusted so as to face the detecting portion. The beam S reflected by the reflecting surface 2c
When the detector 9 detects Rd, the synchronizing signal 11 is sent out as shown in FIG. 7C, an appropriate time lag (delay time) t2 is provided to perform heading, and the modulated beam SRs is sent out as m1. It

Then, when the adjustment of the mounting position of the detector 9 is completed, the time lag t is set by a circuit (not shown).
2 is set. If the time lag t2 is too large,
The reflecting surface 2c of the polygon mirror 2 has a useless margin, and the scanning portion for scanning the surface to be scanned 4Ba may be off the reflecting surface 2c. Then, following the modulated beam m1, FIG.
As shown in (C) and (D), the modulated beams m2 and m are delayed by the reflecting surfaces 2d and 2e after the delay time t2 from the synchronization signal 11.
3 ... is transmitted.

As described above, according to the prior art, since a plurality of detectors are used and the position of each of them is adjusted, the adjustment takes time and becomes a bottleneck in reducing the manufacturing cost. In addition, many adjustment steps are required, and if the adjustment is insufficient, good image formation will be hindered.
In view of such circumstances, an object of the present invention is to provide an optical scanning device with reduced adjustment time. Another object of the present invention is to provide an optical scanning device with a reduced number of parts. Another object of the present invention is to provide an optical scanning device capable of forming an excellent image.

[0013]

SUMMARY OF THE INVENTION The present invention is a polygon mirror.
Of the two modulated beams incident from each of two directions over a first deflecting position where the first modulated beam is incident, a second
In a light scanning device in which a second deflecting position on which a modulated beam is incident is provided on one side of an arbitrary center line passing through the rotation axis of the polygon mirror, the deflecting surface of the polygon mirror has the first deflecting position. The first and second deflection positions are set so that the orbit time of the polygon mirror to reach the second deflection position is longer than the orbit time of the polygon deflection from the second deflection position to the first deflection position. In addition , the beam detecting means is arranged only on the side of the first deflection position to collect the first and second modulated beams, respectively.
And the two-dimensional coordinates X and Y are arranged such that the straight line connecting the scanning center points on the second scanned surface is the X axis and the rotation center of the polygon mirror is located at the positive portion of the Y axis. The mirror is rotating counterclockwise and the first modulation
Beam (one output beam of laser light source) is two-dimensional coordinate
Incident from the third quadrant of the second modulated beam
(The output beam of the other laser light source) is the second coordinate of the fourth
Incident from the quadrant and the first modulated beam causes the first driven beam to travel.
The first state of scanning over the inspection surface and the second modulated beam
A second state of scanning on the second surface to be scanned,
The detection output of the beam detecting means in the first state
In response to controlling the drive of the second modulated beam,
With the same deflecting surface of the polygon mirror as in the first state
The scanning is performed in the second state .

[0014]

[0015]

In addition, a straight line connecting the scanning center points on the first and second scanned surfaces on which the first and second modulated beams are respectively focused is defined as an X axis, and the straight line is located at a positive portion of the Y axis. Two-dimensional coordinate X so that the center of rotation of the polygon mirror comes
When Y is arranged, the polygon mirror is rotating clockwise , and one output beam of the laser light source is a two-dimensional seat.
The other laser light source is incident from the fourth quadrant of the mark
The output beam of is incident from the third quadrant of the two-dimensional coordinates,
A first scanning with a first modulated beam on the first surface to be scanned;
And the second modulated beam on the second surface to be scanned.
And a second state for scanning, in the first state
According to the detection output of the beam detecting means, the second modulation beam
Control the drive of the chamber and it is the same as the first state.
In the second state with the reflecting surface of the polygon mirror
It is also an effective means of the present invention to configure such that scanning is performed .

According to the present invention, as shown in FIG. 4, the single polygon mirror 2 is sandwiched between the condenser lenses (3A, 3B) for scanning on both sides, and as shown in FIG. surface
(First and second scanned surfaces 4Aa, 4Ba) are arranged, and the deflection surface (2a ) of the polygon mirror 2 facing the scanned surface is arranged.
2f) is an optical scanning device which rotates the polygon mirror 2 while causing a beam to enter from the laser light source (1A, 1B) to perform optical scanning.
Of the two modulated beams SLo and SRo which respectively enter the deflecting surfaces 2c and 2a different from each other, the first modulated beam SL
The first deflection position where o is incident (the position deflected by the deflecting surface) and the second deflection position where the second modulated beam SRo is incident (the position deflecting by the deflecting surface) are the rotation axis 21 of the polygon mirror 2. It is provided below the center line R passing through.

The rotation center 21 of the polygon mirror 2 is arranged so as to be displaced above a straight line (X axis) connecting the scanning center points (4Aas, 4Bas) of the respective scanned surfaces (4Aa, 4Ba). In the first embodiment shown in FIG. 1, the deflection surface (reflection surface) of the polygon mirror 2 is
The beam detecting means (beam detector) 6 for detecting the light emission of the laser light source has a first
From the second deflection position (fourth quadrant) to the second deflection position (fourth quadrant) from the second deflection position (fourth quadrant) to the second deflection position (fourth quadrant). It is arranged only on the side of the first deflection position (third quadrant) where the revolution time of the polygon mirror to reach the quadrant) becomes long.

That is, the beam detector 6 is provided on the third quadrant side, the polygon mirror 2 rotates counterclockwise,
In the third quadrant, one of the modulated surfaces (SLs to SLe) of the laser light source causes one of the scanned surfaces (4A
The side where the time from the first state of scanning a) to the second state of scanning the other (4Ba) of the surface to be scanned by the other (SRs to SRe) of the modulated beam of the laser light source in the fourth quadrant becomes faster. To the laser light source (1A, 1B)
Is provided.

That is, since the polygon mirror 2 is rotating in the counterclockwise direction in FIG.
By the rotation of the two surfaces 2b and 2a, the reflecting surface 2c reaches the next modulated beam region (fourth quadrant). On the other hand, when the beam detector 6 is arranged in the fourth quadrant and the polygon mirror 2 is rotated counterclockwise, the reflecting surfaces 2a, 2f, 2e, 2d,
The next modulated beam region (third quadrant) is reached by rotation of 2c and the four surfaces.

A beam detector 6 for detecting the output beam of the one laser light source is provided in the third quadrant, and as shown in FIG. 2, the laser beam emitted by the laser light source 1A is received by the beam detector 6 and Sync signal 10
After a delay time t1 from the generation of the modulated signal SLs, an image signal n1 is transmitted to scan the scanned surface 4Aa, and after a delay time t2 from the synchronization signal 10, the scanned surface 4Aa is scanned to the reflecting surface 2c. 1 reaches the position 2a in FIG. 1, the modulated beam SRs is generated by the same reflecting surface 2c as in the first state, the image signal m1 is transmitted, and the surface to be scanned 4Ba.
To scan.

As described above, the detection output of the beam detector 6 in the first state controls the drive of the modulated beam of the other laser light source in the second state, and the deflection surface is the same as in the first state. Since the optical scanning in the second state is controlled by the (reflecting surface), it is possible to absorb the manufacturing error of each reflecting surface with respect to the rotation center of the beam detector 2.

In the second embodiment shown in FIG. 3, the rotation center 21 of the polygon mirror 2 is set between the scanning center points (4Aas, 4Bas) of the respective scanned surfaces (4Aa, 4Ba) in the fourth quadrant. The beam detector 6, which is arranged above the connecting straight line (X axis) and detects the light emission of the laser light source by reflection from the deflection surface (reflection surface) of the polygon mirror 2, is provided in the fourth quadrant, In the fourth quadrant, the mirror 2 rotates clockwise and one of the modulated beams of the laser light source (SRs to SRe) scans one of the scan surfaces (4Ba) in the fourth quadrant. On the side where the time to reach the second state in which the other (4Aa) of the scanned surface is scanned by the other of the modulated beams (SLs to SLe) of the laser light source becomes faster, the laser light source ( A, 1B) are provided.

That is, since the polygon mirror 2 is rotating clockwise in FIG. 3, the reflecting surfaces 2a, 2 are located below the X axis.
By the rotation of the two surfaces b and 2c, the reflecting surface 2a reaches the next modulated beam region (the third quadrant). On the other hand, when the beam detector 6 is arranged in the third quadrant and the polygon mirror 2 is rotated clockwise, the reflecting surfaces 2c, 2d, 2e, 2f, 2
The next modulated beam area (fourth quadrant) is reached by rotation of a and the four surfaces. Therefore, the laser light sources 1A and 1B for generating the modulated beam are arranged so as to face the deflecting surface on the side where the time required for the reflecting surface to go from the first state (fourth quadrant) to the second state (third quadrant) becomes faster. did.

A beam detector 6 for detecting the output beam of the one laser light source is provided in the fourth quadrant, and the emission of laser light from the laser light source 1B is received by the beam detector 6 and delayed from the generation of the synchronizing signal 10. After the time t1, the modulated beam SRs is generated and the image signal n1 is transmitted to scan the surface 4Ba to be scanned, and after the delay time t2 from the synchronization signal 10, the surface 2Ba to be scanned is the reflection surface 2a shown in FIG. At the position 2c, the modulated beam SLs is generated by the same reflecting surface 2a as in the first state, the image signal m1 is sent out, and the scan surface 4Aa is scanned.

As described above, the detection output of the beam detector 6 in the first state controls the drive of the modulated beam of the other laser light source in the second state, and the deflection surface is the same as in the first state. Since the optical scanning in the second state is controlled by the (reflecting surface), it is possible to absorb the manufacturing error of each reflecting surface with respect to the rotation center of the polygon mirror 2.

The beam detecting means receives the reflected light from the polygon mirror and delays the delay time t1 for controlling the drive timing of the modulated beam incident on the first deflection position, and the second deflection position. After a delay time t2 for controlling the drive timing of the modulated beam incident on the laser beam, a plurality of image signal groups are respectively generated to modulate the laser, and the delay times t1 and t2 are
Where T is the time required for one rotation of the polygon mirror and S is the number of deflection surfaces of the polygon mirror, t1 <(T /
S), t2 ≧ (T / S) , and the above first state is set.
According to the detection output of the beam detecting means, the second
Controlling the drive of the modulated beam and at the same time the first state
With the same deflecting surface of the polygon mirror as the above
Performing scanning in the state is also an effective means of the present invention.

In FIGS. 1 and 2, the beam detecting means (beam detector) 6 receives the reflected light from the polygon mirror in the first state, and the deflection surface is rotated in two steps from the first state. Since the plurality of image signal groups are generated and the laser is modulated after the delay time t2 in the second state, the delay time t2 is set to t2> (T / S).

As shown in FIG. 4, the first line LA1 of the image scanned on the photoconductor 4A is transferred to the intermediate transfer body 5 and then rotated toward the photoconductor 4B, so that the photoconductor 4B is rotated.
At the position where the first line LB of the scanned image is in contact with the intermediate transfer body 5 and is transferred to the intermediate transfer body 5 in line with the line LA1, the cue positions in the main scanning direction of both lines are the same. Must be, therefore, this line LA
In FIG. 2, the position where 1 and LB1 coincide with each other is set by the delay time t2 determined by [(2T / S) + ts], and the delay time t2 is larger than the delay time determined by (T / S). .

Therefore, in the case of t2> (T / S), the laser light emitted from the laser light source 1A is received by the beam detecting means 6, and after the delay time t2 from the synchronizing signal 10 thereof,
Modulated beam SR by the same reflecting surface 2c as in the first state
s is generated, the image signal m1 is transmitted, the surface to be scanned 4Ba is scanned, and the driving of the modulated beam of the other laser light source in the second state is controlled, so that the production of each reflecting surface with respect to the rotation center of the polygon mirror 2 is performed. A time that can absorb an error and reaches a second state in which one of the scanned surfaces is scanned by one of the laser light sources to a second state in which the other scanned surface is scanned by the other laser light source. Since each of the laser light sources is arranged so as to face the deflection surface on the side where the speed increases, the polygon mirror can quickly change from the first state to the second state in one rotation of the polygon mirror. It is possible to minimize the influence of fluctuations in the rotation speed of the.

The delay time t2 is determined by the polygon mirror 2
Is equal to the moving time of the deflecting surface during one rotation of
It is also possible to set 2 = (T / S). In this case, as shown in FIG. 5, the polygon mirror 2 is represented by a triangular shape or a quadrangular shape.
Alternatively, in the case where the deflecting surfaces are adjacent to each other like 2d ″ and 2a ″, and in the case of the quadrangular shape shown in FIG. 6, the synchronization signal from the detector 6 as in (A) in the third quadrant causes (B) The modulated beam n1 is transmitted after the delay time t1 shown in (1), and the delay time t2 = (T / S) as shown in (C).
The modulated beam m1 is subsequently emitted.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Only.

The optical scanning device according to the embodiment of the present invention is shown in FIG.
As shown in FIG. 3, the photosensitive members 4A and 4B forming the surface to be scanned are arranged on both sides of the single polygon mirror 2 via condensing lenses (3A and 3B) for scanning, respectively. On the deflection surface of the polygon mirror 2 facing the laser light source (1
The polygon mirror 2 is rotated while the beam is incident from A and 1B) to perform optical scanning.

As shown in FIG. 1, laser light sources 1A, 1B
Light rays from the polygon mirror 2 and scanning condenser lens 3
A, 3B, reflection mirrors 7A, 7B, and the like are used as an optical scanning system to form a photosensitive drum (photoconductor) 4A, which is an image carrier.
An electrostatic latent image is carried on 4B. In addition, the photosensitive drum 4A,
Although not shown, 4B is provided with a charger for charging the drum, a developing device (for example, black color and magenta color), a cleaning blade for removing residual toner, and the like.

The surfaces of the photosensitive drums 4A and 4B are in contact with the intermediate transfer sheet 17 (outer surface), and the intermediate transfer sheet is a resistor having a volume resistivity in the medium resistance region of 10 ¹⁰ to 10 ¹⁴ Ωcm, and has a thickness of It is molded of polycarbonate, polyimide, polyetheretherketone or the like having a thickness of about 150 μm.

Therefore, the photosensitive drums 4A and 4B are sequentially developed one by one from the developing device for each rotation of the drum and transferred to the intermediate transfer sheet 17 by Coulomb force. After the transfer of one color is completed, the photosensitive drum removes toner with a cleaning blade (not shown), and then another color is developed on the photosensitive drum. Specifically, the photosensitive drum 4
The black color is transferred from A to the intermediate transfer sheet 17 and then rotated to the position of the photosensitive drum 4B.
Cyan color 7 is transferred from the photosensitive drum 4B.

After transferring the black color to the intermediate transfer sheet 17, the photosensitive drum 4A removes the residual toner with a cleaner, develops the magenta color, and transfers the magenta color to the intermediate transfer sheet 17. Similarly, on the photosensitive drum 4B, after transferring the cyan color, residual toner is removed by a cleaner, and yellow is developed, so that the transfer is performed.

Next, details of the optical scanning device used in the image forming apparatus that operates as described above will be described. FIG. 1 shows a first embodiment of the optical scanning device according to the present invention. As shown in FIG. 1, the rotation center 21 of the polygon mirror 2 is the scanning center point (4Aas) of each surface (4Aa, 4Ba) to be scanned. , 4B
beam detecting means (beam detector) 6 for detecting the light emission of the laser light source, which is arranged above the straight line (X axis) connecting as) and is reflected by the deflection surface (reflection surface) of the polygon mirror 2. , Are arranged to receive the reflected light in the third quadrant.

That is, since the polygon mirror 2 is rotating in the counterclockwise direction in FIG.
By the rotation of the two surfaces 2b and 2a, the reflecting surface 2c reaches the next modulated beam region (fourth quadrant). On the other hand, when the beam detector 6 is arranged in the fourth quadrant and the polygon mirror 2 is rotated counterclockwise, the reflecting surfaces 2a, 2f, 2e, 2d,
The next modulated beam region (third quadrant) is reached by rotation of 2c and the four surfaces.

Therefore, the beam detector 6 is provided so as to receive the reflected light in the second quadrant, the polygon mirror 2 rotates counterclockwise, and one of the modulated beams (SLs to SLs) of the laser light source in the third quadrant. SLe) scans one side (4Aa) of the surface to be scanned from the first state in the fourth quadrant by the other modulated beam of the laser light source (SRs to SRe) to the other side (4) of the surface to be scanned.
The laser light sources (1A, 1B) are provided on the side where the time to reach the second state of scanning Ba) becomes faster.

Then, as shown in FIG.
The laser beam emitted by A is received by the beam detector 6, and after a delay time t1 from the generation of the synchronization signal 10,
The modulated surface SLs is generated, the image signal n1 is transmitted to scan the scanned surface 4Aa, and after the delay time t2 from the synchronization signal 10, the reflective surface 2c scanned on the scanned surface 4Aa is located at the position 2a in FIG. Therefore, the same reflecting surface 2 as in the first state
The modulated beam SRs is generated by c and the image signal m1 is transmitted to scan the surface to be scanned 4Ba.

Next, the reflection surface 2d for scanning the surface to be scanned 4Aa receives the laser light emitted from the laser light source 1A by the beam detector 6, and after the delay time t1 from the generation of the synchronizing signal 10, the modulated beam SLs. Is generated to send the image signal n2 to scan the scan surface 4Aa, and after the delay time t2 from the synchronization signal 10, the scan surface 4Aa is scanned and the reflection surface 2d reaches the position 2a in FIG. Modulated beam SRs is generated by the same reflecting surface 2d as in the first state, and image signal m2 is transmitted to scan surface 4Ba.
To scan. After that, the same operation is repeated by the reflecting surfaces 2e to 2b.

FIG. 3 shows a second embodiment of the optical scanning device according to the present invention. As shown in FIG.
The rotation center 21 of each of the scanning surfaces (4Aa, 4Ba)
A straight line (X) connecting the scanning center points (4Aas, 4Bas) of
The beam detecting means (beam detector) 6 arranged to be displaced above the axis) is reflected by the deflecting surface (reflecting surface) of the polygon mirror 2, and detects the light emitted from the laser light source. It is arranged to receive light.

That is, since the polygon mirror 2 is rotating clockwise in FIG. 3, the reflecting surfaces 2a, 2 are located below the X axis.
By the rotation of the two surfaces b and 2c, the reflecting surface 2a reaches the next modulated beam region (the third quadrant). On the other hand, when the beam detector 6 is arranged in the third quadrant and the polygon mirror 2 is rotated clockwise, the reflecting surfaces 2c, 2d, 2e, 2f, 2
The next modulated beam area (fourth quadrant) is reached by rotation of a and the four surfaces.

Therefore, the beam detector 6 is provided so as to receive the reflected light in the fourth quadrant, and the polygon mirror 2 rotates clockwise so that one of the modulated beams (SRs to SRe) of the laser light source in the fourth quadrant. From the first state in which one of the surfaces to be scanned (4Ba) is scanned by
In the third quadrant, the other of the modulated surfaces of the laser light source (SLs to SLe) causes the other of the scanned surface (4A
The laser light sources (1A, 1B) are provided on the side where the time to reach the second state of scanning in (a) becomes faster.

As described in the first embodiment, the laser beam emitted from the laser light source 1A is received by the beam detector 6, and the modulated beam SLs is generated after a delay time t1 from the generation of the synchronizing signal 10 to generate an image. The signal n1 is sent to scan the scanned surface 4Ba, and after the delay time t2 from the synchronization signal 10, the scanned surface 4Ba is scanned and the reflective surface 2a reaches the position 2c in FIG. Modulated beam SLs is generated by the same reflecting surface 2c, an image signal m1 is transmitted, and the surface to be scanned 4Aa is scanned. After that,
A similar operation is repeated by the reflecting surfaces 2f to 2b.

That is, in the first and second embodiments, the second deflection position (fourth quadrant or fourth quadrant) from the first deflection position (third quadrant or fourth quadrant) on which the modulated beam is incident. From the orbiting time of the polygon mirror to reach the third quadrant, the second deflection position (the fourth quadrant or the third quadrant)
Only on the first deflection position side (third quadrant or fourth quadrant) where the orbit time of the polygon mirror from the quadrant) to the first deflection position (third quadrant or fourth quadrant) becomes long. And the drive output of the modulated beam of the other laser light source in the second state is controlled by the detection output of the beam detector 6 in the first state, and the deflection surface (reflection surface) is the same as in the first state. Since the optical scanning in the second state is controlled by the above, it is possible to absorb the manufacturing error of each reflecting surface with respect to the rotation center of the beam detector 2.

Further, in the above description, the embodiment in which the number of deflecting surfaces of the polygon mirror 2 is six has been described, but the present invention is not limited to this. In FIG. 5, the Y-axis is symmetrical, and in the case of a triangular shape, the deflection surface 2c ′,
2a 'is located, and in the case of a square shape, the deflection surfaces 2d ", 2
a ″ is located and in the case of a pentagon, the deflection surfaces 20d and 20a
Is located. Therefore, it can be applied to the case of a triangular shape, a quadrangular shape, or a polygonal shape other than these.

Then, the delay times t1 and t2 are
Where T is the time required for one rotation of the polygon mirror and S is the number of deflection surfaces of the polygon mirror, t1 <(T /
S) and t2 ≧ (T / S).

As described above with reference to FIGS. 1 and 2, the beam detecting means (beam detector) 6 includes the first
The reflected light from the polygon mirror in the state is received, and after a delay time t2 in the second state due to the rotation of the deflecting surface in two steps from the first state, a plurality of image signal groups are generated to modulate the laser. Is configured. Therefore, the delay time t2 is set to t2> (T / S).

It is also possible to set t2 = (T / S). In that case, as shown in FIG. 5, the deflecting surface 2c 'represents a polygonal mirror 2 in a triangular or quadrangular shape. 2a ′ or 2d ″, 2a ″, the case where the deflection surfaces are adjacent to each other, and in the case of the quadrangular shape shown in FIG. 6, the synchronization signal from the detector 6 as shown in FIG. , (B), the modulated beam n1 is transmitted after the delay time t1, and as shown in (C), the modulated beam m1 is transmitted after the delay time t2 = (T / S). This is the same for the triangular shape, and
The same applies to polygonal shapes other than triangular and quadrangular.

As described above, in the present embodiment, since a plurality of photoconductors are scanned by the same reflecting surface of the polygon mirror, it is possible to absorb the manufacturing error of each reflecting surface with respect to the rotation center of the polygon mirror. Opposing the deflection surface on the side where the time from the first state in which one of the scanned surfaces is scanned by one of the laser light sources to the second state in which the other of the scanned surfaces is scanned by the other laser light source becomes faster Since each of the laser light sources is arranged,
It is possible to quickly change from the first state to the second state in one rotation of the polygon mirror, and it is possible to minimize the influence of fluctuations in the rotation speed of the polygon mirror. Further, it is possible to adjust the distance between the contact positions of the intermediate transfer member and the photoconductor and the error such as the photoconductor diameter.

[0053]

As described above in detail, the present invention can provide an optical scanning device which can reduce the adjustment time by reducing the number of parts and can perform accurate image formation.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an optical scanning device according to the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of the optical scanning device.

FIG. 3 is a configuration diagram showing a second embodiment of the optical scanning device according to the present invention.

FIG. 4 is a configuration diagram showing an embodiment of an image forming apparatus provided with an optical scanning device according to the present invention.

FIG. 5 is a configuration diagram showing another embodiment of a polygon mirror.

FIG. 6 is an explanatory diagram illustrating an operation of FIG.

FIG. 7 is an explanatory diagram illustrating an operation of a conventional example.

FIG. 8 is a configuration diagram showing an optical scanning device according to a conventional example.

[Explanation of symbols]

1 Laser light source (1A, 1B) 2 polygon mirror 3 Condensing lens (3A, 3B) 4 photoconductors (4A, 4B) 5 Intermediate transfer body 6 Beam detector

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-6-217086 (JP, A) JP-A-4-313776 (JP, A) JP-A-60-28619 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G02B 26/10 B41J 2/44

Claims (3)

(57) [Claims] 1. A first deflected position of a first modulated beam, and a second deflected beam of a second modulated beam, of the two modulated beams respectively entering the polygon mirror from two directions.
The deflection position of the polygon mirror is provided on one side of an arbitrary center line passing through the rotation axis of the polygon mirror, and the deflection surface of the polygon mirror is set to the second deflection position from the first deflection position. The first and second deflection positions are set so that the revolution time of the polygon mirror to reach the first deflection position is longer than the revolution time of the polygon mirror. The beam detecting means is arranged only on the deflecting position side, and a straight line connecting the scanning center points on the first and second scanned surfaces on which the first and second modulated beams are focused is defined as an X axis, When the two-dimensional coordinates X and Y are arranged so that the rotation center of the polygon mirror is located at the positive portion of the Y axis, the polygon mirror is rotating counterclockwise and the first modulated beam is the two-dimensional image. Enter from the third quadrant of coordinates
And the second modulated beam is projected onto the two-dimensional coordinates.
Incident from the fourth quadrant of the first modulated beam
The first state of scanning on the surface to be scanned of the
A second state in which the second surface to be scanned is scanned with
The detection of the beam detecting means in the first state
If the drive of the second modulated beam is controlled according to the output,
Both of the polygon mirrors that are the same as the first state
The scanning in the second state is performed on the deflecting surface.
An optical scanning device, characterized in that. 2. A first deflected position of a first modulated beam, and a second modulated beam of a second modulated beam, of the two modulated beams respectively entering the polygon mirror from two directions.
The deflection position of the polygon mirror is provided on one side of an arbitrary center line passing through the rotation axis of the polygon mirror, and the deflection surface of the polygon mirror is set to the second deflection position from the first deflection position. The first and second deflection positions are set so that the revolution time of the polygon mirror to reach the first deflection position is longer than the revolution time of the polygon mirror. The beam detecting means is arranged only on the deflecting position side, and a straight line connecting the scanning center points on the first and second scanned surfaces on which the first and second modulated beams are focused is defined as an X axis, When the two-dimensional coordinates X and Y are arranged so that the rotation center of the polygon mirror is located at the positive portion of the Y-axis, the polygon mirror is rotating clockwise, and the first modulated beam has the two-dimensional coordinates. Enter from the 4th quadrant of
And the second modulated beam is projected onto the two-dimensional coordinates.
Incident from the third quadrant of the first modulated beam
The first state of scanning on the surface to be scanned of the
And a second state in which the second surface to be scanned is scanned with a beam.
The detection of the beam detecting means in the first state
If the drive of the second modulated beam is controlled according to the output,
Both of the polygon mirrors that are the same as the first state
The scanning in the second state is performed on the deflecting surface.
An optical scanning device, characterized in that. 3. A first deflected position of a first modulated beam, and a second deflected beam of a second modulated beam, of the two modulated beams respectively entering the polygon mirror from two directions.
The deflection position of the polygon mirror is provided on one side of an arbitrary center line passing through the rotation axis of the polygon mirror, and the deflection surface of the polygon mirror is set to the second deflection position from the first deflection position. The first and second deflection positions are set so that the revolution time of the polygon mirror to reach the first deflection position is longer than the revolution time of the polygon mirror. The beam detecting means is arranged only on the deflecting position side, and the beam detecting means receives the reflected light from the polygon mirror and controls the driving timing of the first modulated beam incident on the first deflecting position. Incident at the delay time t1 and the second deflection position
By modulating the laser to generate the second modulated beams each of a plurality of image signal group after a delay time t2 that controls the drive timing of the delay time t1 and t2 are satisfied the following formula, the first The first scanned object with a modulated beam
The beam detecting means in a first state of scanning on a surface
Drive of the second modulated beam is controlled according to the detection output of
And the same polygon mirror as in the first state.
Second deflected beam on the second deflection surface
Keru you to a second state for scanning the Menjo to perform the scan
An optical scanning device, characterized in that the. t1 <(T / S), t2 ≧ (T / S) where T: time required for one rotation of the polygon mirror, S:
Number of deflection surfaces of polygon mirror