JPH10274744A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of scanning irregularity by the secular change of the pitch of a light beam in sub-scanning operation on a recording material in an inner drum type optical scanning device. SOLUTION: This optical scanning device is composed of light source devices 12, 13 emitting plural light beams 10, 11, an optical deflector 23 provided with a mirror 24 and a driving means 25 for rotating the mirror 24 about a rotary axis almost included in its reflection plane, a platen 27 for bending/holding a recording material 26 on the position subjected to main scanning by light beams 10, 11 reflected/deflected by the optical deflector 23, an optical system for converging the light beams 10, 11 to beam spots on the recording material 26 and sub-scanning means 28, 29 for relatively moving the platen 27 and the optical deflector 23 in the direction parallel with the rotary axis of mirror Z. In this case, a changing means 16 (an optical element having a wedge-shaped cross section) for changing the interval of beam spots in the sub-scanning direction on the recording material 26 is provided.

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 for scanning a recording material with a light beam, and more particularly to scanning a recording material held in a curved state with a light beam whose deflection center is substantially deflected about an axis. The present invention relates to a so-called inner drum type optical scanning device.

[0002]

2. Description of the Related Art As shown in, for example, Japanese Patent Application Laid-Open No. 5-308488, a recording material curved and held on a platen forming a part of a cylindrical inner surface is substantially deflected by a light beam whose deflection center is deflected about an axis. 2. Description of the Related Art A so-called inner drum type optical scanning device that performs main scanning and performs sub scanning by relatively moving a platen and an optical deflector in a direction substantially perpendicular to the main scanning direction is known. This type of optical scanning device can be used to constitute a device for recording image information or the like on a photosensitive recording material or a device for reading recorded information from a recording material on which image information or the like is recorded.

In this inner drum type optical scanning device, as shown in the above-mentioned Japanese Patent Application Laid-Open No. 5-308488, in order to increase the recording speed and the reading speed, a plurality of light scanning devices arranged in the sub-scanning direction are used. It has also been proposed to scan a recording material simultaneously with a light beam. As described above, the inner drum type optical scanning device using a plurality of light beams basically includes a light source device that emits a plurality of light beams, a mirror, and a rotation axis substantially including the mirror within its reflection surface. An optical deflector comprising driving means for rotating the
At a position where main scanning is performed by a plurality of light beams reflected and deflected by the optical deflector, a platen that holds the recording material in a curved state with the rotation axis of the mirror substantially as a curved center,
The plurality of light beams are incident on a mirror of an optical deflector at a tilt angle with respect to a plane perpendicular to the rotation axis in a state where the plurality of light beams are arranged at intervals in a direction parallel to the rotation axis. And a sub-scanning unit for relatively moving the platen and the optical deflector in a direction parallel to the rotation axis of the mirror.

[0004]

In the inner drum type optical scanning device having the above configuration, in actual use, it is necessary to lower the resolution in order to improve the recording speed or to improve the image quality of the recorded image. It is necessary to increase the resolution. Further, there is a problem that scanning unevenness is likely to occur because the sub-scanning pitch of the light beam on the recording material is not controlled to a predetermined value or the sub-scanning pitch changes over time.

In the above-described optical scanning device, since the light beam incident on the mirror of the optical deflector is projected, the light beam is emitted by the mirror where the deflection scanning angle is large, so that the diameter of the focused spot fluctuates. It is concerned. To avoid such a case, it is conceivable to use a mirror having a sufficiently large width in the main scanning direction as the mirror,
Then, the rotational load of the optical deflector increases, and high-speed scanning becomes difficult.

Accordingly, the present invention provides an inner drum type optical scanning device which can change the resolution, can eliminate the scanning unevenness due to the change in the sub-scanning pitch, and does not change the desired focused spot diameter during scanning. The purpose is to provide.

Another object of the present invention is to provide an inner drum type optical scanning device which can set the mirror size of the optical deflector small while achieving the above object.

[0008]

According to the present invention, there is provided an optical scanning device comprising a light source device, an optical deflector, a platen, an optical system, and a sub-scanning means as described above. A means for changing a beam spot interval in the upper sub-scanning direction is provided.

The means for changing the interval between the beam spots can be constituted by, for example, means for changing the interval between a plurality of light beams before entering the optical deflector.

As means for changing the interval between a plurality of light beams, for example, assuming that a telecentric imaging system is used, a plurality of light beams before being incident on an optical deflector are collectively passed. It is possible to use a beam expander or a beam reducer to allow the light beam before being incident on the optical deflector to pass, and to use a parallel flat plate whose inclination angle with respect to the light beam can be changed freely, Further, it is also possible to use an optical element having a wedge-shaped cross section, which allows the light beam before being incident on the optical deflector to pass through and allows the inclination angle with respect to the light beam to be changed freely.

Further, the means for changing the beam spot interval may be constituted by means for changing an angle formed by a plurality of light beams before entering the optical deflector.
As means for changing the angle formed by a plurality of light beams with each other, for example, assuming that a non-telecentric imaging system is used, a plurality of light beams before entering the optical deflector are collectively passed. It is possible to use a beam expander or a beam reducer to allow the light beam before being incident on the optical deflector to pass, and to use a parallel flat plate whose inclination angle with respect to the light beam can be changed freely, Further, it is also possible to use an optical element having a wedge-shaped cross section, which allows the light beam before being incident on the optical deflector to pass through and allows the inclination angle with respect to the light beam to be changed freely.

On the other hand, the means for changing the beam spot interval as described above splits one light beam before being incident on the optical deflector into a plurality of light beams and emits a plurality of light beams. You may comprise so that it may do. As such means, specifically, a multi-frequency AOD (acousto-optic light deflector), and particularly, an AOM (acousto-optic light modulator) that can modulate a light beam is preferable. Used.

Further, in the optical scanning device of the present invention, an aperture plate for passing one or a plurality of light beams before entering the optical deflector and narrowing at least the beam width in the main scanning direction is provided. Is desirable. In such a case, the beam diameter of the light beam in the main scanning direction (1 / e ² diameter:
When Db is the diameter at the position where the light intensity is 1 / e ² of the value of the beam center, and Dl is the opening width of the aperture plate in the main scanning direction,
When the value of Db / Dl is 0.7 to 10, more preferably 1.0
It is desirably in the range of ~ 5.

Further, instead of the opening plate as described above,
A filter may be provided that transmits one or a plurality of light beams before being incident on the optical deflector, and has a characteristic that at least their intensity distribution characteristics in the main scanning direction gradually decrease as they deviate from the beam center. In such a case, the beam diameter of the light beam in the main scanning direction (1 / e ² diameter)
Is Db, the transmittance of the filter is 1 /
When the filter width in the range where the value of 2 is taken is Dl ′,
The value of Db / Dl 'is 0.7 to 10, more preferably 1.
It is desirable to be in the range of 0-5.

In the optical scanning apparatus according to the present invention, a means for measuring a beam spot interval in the sub-scanning direction on the recording material is provided, and the means for changing the beam spot interval is provided with the beam spot interval measurement. Preferably, it is configured to be driven based on the output of the means.

On the other hand, when the optical scanning device of the present invention is applied to an image recording device or the like, a modulating means for modulating the plurality of light beams is provided. In this case, synchronization detecting means for detecting a time interval at which a plurality of beam spots pass through a predetermined position in the main scanning direction is provided, and the modulating means controls each light beam based on an output of the synchronization detecting means. It is desirable to control the modulation start timing of each light beam so that the modulation start positions of the light beams are aligned with each other on the recording material.

Further, in the optical scanning device of the present invention, it is preferable that a means for controlling the light source device to stop driving during a period when the light beam is out of a predetermined scanning range including the effective main scanning area is provided. .

Further, in the optical scanning device of the present invention,
Preferably, means are provided for controlling the overall traveling direction of the plurality of light beams before entering the light deflector.

An optical system for converging a plurality of light beams to a beam spot on a recording material preferably includes an imaging lens inserted in an optical path of the light beam before entering the optical deflector. desirable.

[0020]

As described above, the optical scanning device of the present invention is provided with a means for changing the beam spot interval in the sub-scanning direction on the recording material, so that the operator can improve the recording speed. It is possible to lower the resolution or increase the resolution to improve the quality of the recorded image. Further, when the sub-scanning pitch changes over time, this means can be operated to appropriately correct the sub-scanning pitch. Therefore, according to this optical scanning device, it is possible to eliminate scanning unevenness caused by a change in the sub-scanning pitch.

Further, in the optical scanning device of the present invention, an aperture plate for passing one or a plurality of light beams before entering the optical deflector and narrowing at least the beam width in the main scanning direction is provided. In this case, the width of the mirror of the optical deflector in the main scanning direction can be reduced, thereby realizing high-speed scanning by reducing the rotational load of the optical deflector.

The beam diameter of the light beam in the main scanning direction (1 / e
⁽² diameter) is Db, the beam spot diameter on the recording medium is d, the light wavelength is λ, and the focal length of the optical system is f, the opening width Dl of the aperture plate in the main scanning direction is given by the following equation. .

Dl = k (Db / Dl) .lambda.f / d Here, the value of k when the slit aperture is used changes according to the value of Db / D1 as shown in FIG. As described above, in order to reduce the width of the mirror of the optical deflector in the main scanning direction, the aperture width Dl must be reduced, and for this purpose, the smaller the value of k, the more advantageous.

When the aperture is not formed, the mirror size of the optical deflector is usually set so that the width of the convergent spot during main scanning does not fluctuate so as not to be twice as large as the diameter of the incident beam. Must be set. At this time, the value of k becomes 2.54, and the mirror size increases.

In general, it is desirable that the value of k is about 2 or less. When the value of Db / Dl is 0.7, the value of k is 2.07. A preferable minimum value of Db / Dl is set. Also, the value of k is 2.07, which is 8
Since it is more preferable that the value is about 5% or less, k = 1.65.
The value of Db / Dl, 1.0, is set to a more preferable minimum value.

On the other hand, if the opening width Dl is too small, the light transmittance at the opening plate decreases, and the light use efficiency decreases. FIG. 17 shows the relationship between the value of Db / Dl and the light transmittance at the aperture plate. The light transmittance is shown as a relative value when the light transmittance without the aperture plate is set to 1. In general, the light transmittance is desirably about 0.1 or more in the above relative value. When the value of Db / Dl is 16, the light transmittance is 0.1.
Since the value is 10, the value of 10 is set as a preferable maximum value of Db / Dl. Further, since it is more preferable that the light transmittance is 0.3 or more of the relative value, the value 5 of Db / Dl at which the light transmittance becomes 0.31 is set as a more preferable maximum value.

The preferred range of the value of Db / Dl described above is the same when the above-mentioned filter is used instead of the aperture plate. However, in this case, a filter width Dl ′ in a range in which the transmittance of the filter takes a half of the maximum value is used instead of Dl.

When the above-mentioned aperture plate is used, a light beam may be emitted at the edge of the aperture and side lobes may be generated. When the above-described filter is used, it is necessary to prevent the generation of the side lobes. Can be.

Although the slit-shaped opening and the filter have been described above, for example, the use of an elliptical opening has almost the same effect in the main scanning direction. It is not limited to a slit-shaped opening.

Further, in the optical scanning device of the present invention, means for measuring the beam spot interval in the sub-scanning direction on the recording material is provided, and the means for changing the beam spot interval is provided by the beam spot interval measuring means. In the case of driving based on the output, the beam spot interval can be automatically corrected.

On the other hand, when the optical scanning device of the present invention is applied to an image recording device or the like, a modulation means for modulating a plurality of light beams, and a time interval for passing a plurality of beam spots at a predetermined position in the main scanning direction. And a modulation detecting means for detecting the modulation start timing of each light beam based on the output of the synchronization detection means so that the modulation start positions of the light beams are aligned with each other on the recording material. In the case of controlling, even if a plurality of beam spots take various positions on the recording material in the main scanning direction, recording start positions on the recording material by the respective light beams are fixed to each other. Therefore, no matter how the positions of the plurality of beam spots fluctuate in the main scanning direction, there is no need to perform any correction.

Further, in the optical scanning device according to the present invention, when a means is provided for controlling the light source device to stop driving while the light beam is out of a predetermined scanning range including the effective main scanning area, The light beam deviating from the effective main scanning area is prevented from being eclipsed by the mirror of the optical deflector to generate stray light.

Also, in the optical scanning device of the present invention, the light beam scanning line on the recording material should originally draw a locus that is entirely included in a plane perpendicular to the mirror rotation axis of the optical deflector. However, if the parallelism between the mirror surface of the optical deflector and the mirror rotation axis is slightly deviated, the light beam scanning line on the recording material is curved so as to partially deviate from the surface. This curvature of the scanning line is generally called bowing.

Therefore, as described above, if means for controlling the overall traveling directions of a plurality of light beams before entering the optical deflector are provided, by correcting the traveling directions of the light beams, The bowing can be eliminated.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an optical scanning device according to a first embodiment of the present invention, and FIGS. 2 and 3 are front views of main parts of the optical scanning device, respectively.
It shows a perspective shape.

As shown in the figure, the optical scanning device includes semiconductor lasers 12 and 13 as light source devices for emitting light beams (laser beams) 10 and 11, respectively, and a collimator for converting the light beams 10 and 11 into parallel light, respectively. Lenses 14 and 15, a wedge-shaped optical element 16 inserted in the optical path of one of the light beams 11, and a beam splitter 17 for setting the two light beams 10 and 11 at a small interval from each other. , Beam expander (or beam reducer) lenses 18 and 19 inserted in the optical paths of the light beams 10 and 11 having passed through the beam splitter 17, and the light beams 10 and
Mirrors 20 and 21 that fold 11 optical paths and these mirrors 2
An imaging lens 22 is inserted between 0 and 21 in the optical path of the light beams 10 and 11.

The light beams 10 and 11 reflected by the mirror 21 travel diagonally upward. An optical deflector 23 is provided at a position where these light beams 10 and 11 are received. This optical deflector 23
A mirror 24 and a driving means 25 for rotating the mirror 24 about a rotation axis Z substantially included in the reflection surface thereof, and a holding member such that the light beams 10 and 11 are incident on the mirror 24. Fixed to 31. The light beams 10, 11 having entered the mirror 24 are reflected and deflected by the rotating mirror 24.

The optical system composed of the above elements 14 to 22 is
The light beams 10, 11 are arranged so as to be incident on the mirror 24 at an oblique angle with respect to a plane perpendicular to the rotation axis Z in a state where they are arranged at a distance from each other in a direction parallel to the rotation axis Z. I have.

Further, a platen 27 for holding a recording material 26 is provided at a position where the light beams 10 and 11 reflected and deflected by the light deflector 23 are incident. The platen 27 holds the photosensitive recording material 26 in a curved manner with the mirror rotation axis Z as a curved center.

On the other hand, the platen 27 is held movably in a direction parallel to the mirror rotation axis Z. A female screw block 28 is fixed to the platen 27. The female screw block 28 is screwed with a precision screw 29 that constitutes sub-scanning means together with the female screw block 28. Mirror rotation axis Z
The precision screw 29 extending in a direction parallel to the above is rotated forward and reverse by driving means (not shown). When the precision screw 29 rotates in this manner, the female screw block 28 advances and retreats, whereby the platen 27 linearly moves in a direction parallel to the mirror rotation axis Z.

The light beams 10 and 11 are converged by the imaging lens 22 into small beam spots on the recording material 26, respectively. The recording material 26 held as described above is main-scanned by the reflected and deflected light beams 10 and 11 as indicated by the trajectory Q in the drawing. At the same time, platen 27
Moves linearly as described above, and the platen 27 and the optical deflector
The sub-scanning of the light beams 10 and 11 is performed by changing the relative position of 23.

As described above, the recording material 26 is
Although two-dimensional scanning by 10 and 11 is performed, scanning is performed simultaneously by two light beams 10 and 11 that are separated from each other in the sub-scanning direction. Therefore, high-speed scanning is performed compared to scanning with one light beam. Is realized. It is of course possible to simultaneously scan the recording material 26 with three or more light beams. Naturally, the higher the number of light beams, the higher the speed of scanning.

The optical scanning device according to the present embodiment constitutes an image recording device as an example.
13 is modulated and driven by a modulation driving circuit 30 receiving the image signal S. Therefore, the light beams 10 and 11 are directly modulated based on the image signal S, and the image carried by the image signal S is recorded on the recording material 26.

Hereinafter, the scanning trajectories of the light beams 10 and 11 will be described with reference to FIG. Mirror the Z axis as shown
Take the rotation axis of 24, take the Y axis in the normal direction of the mirror 24,
Then, the X axis is set in the mirror plane orthogonal to the Y axis. The incident light a incident obliquely from below in the figure with respect to the normal vector of the mirror surface is reflected obliquely upward by this mirror surface and reflected light b
Becomes

Here, considering the lines a ′ and b ′ that project the rays of the incident light a and the reflected light b onto the XY plane, respectively,
The angle between a and b ′ is θ _a , and the angle between the lines b and b ′ is θ _b . The angles formed by the projected lines a ′ and b ′ and the Y axis are φ _a and φ _b , respectively.

By the vector calculation, the angles θ _a ,
Finding the relationship between θ _b , φ _a and φ _b gives θ _b = −
θ _a , φ _b = φ _a From this, even if the mirror 24 rotates (that is, the X and Y axes rotate), the angles θ _a and θ _b
It can be seen that the made constant regardless of the phi _a. Therefore,
In FIG. 1, it can be seen that the convergent spots of the light beams 10 and 11 scan so as to draw a circular locus in a plane (XY plane in FIG. 4) perpendicular to the mirror rotation axis Z.

As described above, in this type of optical scanning device, when changing the resolution, it is sometimes necessary to change the sub-scanning pitch. Also, the beam spot interval (L in FIG. 1) of the light beams 10 and 11 in the sub-scanning direction on the recording material 26 may change with time, and the sub-scanning pitch may fluctuate.

At this time, the optical element 16 having a wedge-shaped section is swung in the direction of arrow R in FIG.
When the inclination angle with respect to 10 and 11 is changed, the angle between these light beams 10 and 11 before entering the mirror 24 of the optical deflector 23 changes, so that the beam spot interval L can be set to a predetermined value. it can. Thereby, it is possible to eliminate the scanning unevenness caused by the change in the sub-scanning pitch.

The spot diameter and the sub-scanning pitch may be changed simultaneously by operating the wedge-shaped optical element 16 and changing the magnification of the beam expander (or beam reducer) lenses 18 and 19, or The sub-scanning pitch may be changed by changing only the magnification of the lenses 18 and 19.

As shown in FIGS. 2 and 3, a beam spot interval measuring means 40 is provided outside the effective main scanning range, and a means for oscillating the optical element 16 is provided. If driven based on the output of the means 40, the beam spot interval L can be automatically corrected.

An example of the beam spot interval measuring means 40 will be described below with reference to FIG. This beam spot interval measuring means 40 is an aperture plate having a triangular aperture 41a.
41 and the spot 10 of the light beam 10 through the opening 41a.
s, and a photodetector 42 for detecting the spot 11s of the light beam 11. Here, the edge of the opening 41a is sharpened like a knife edge. Also beam spot
10s and 11s are sufficiently separated in the main scanning direction (the left-right direction in FIG. 5) so that they are not simultaneously detected by the photodetector 42.

In measuring the beam spot interval,
During the period when the light beams 10, 11 pass over the aperture plate 41, the driving of the semiconductor lasers 12, 13 is controlled such that the intensity of the light beams 10, 11 takes a predetermined constant value. In this case, the waveform of the output signal of the photodetector 42 is basically as shown in FIG. The pulse-shaped waveform that rises first over time is due to the detection of the beam spot 10s, and the pulse-shaped waveform that rises next is:
This is due to the detection of the beam spot 11s.

At this time, the distance d between the beam spot 10s and the beam spot 11s in the sub-scanning direction is
Assuming that the main scanning speed of s and 11s is v, the angle between the oblique edge of the opening 41a and the main scanning direction is ξ, and the time widths of detecting the beam spots 10s and 11s are Δt1 and Δt2, respectively, d = ｛v · (Δt1-Δt2) · tan ・ / 2.

Even when three or more light beams are used, the distance between the beam spots in the sub-scanning direction can be determined in the same manner as described above.

As described above, the beam spots 10s and 11s
When the light beams 10 and 11 are separated from each other in the main scanning direction, the recording start points of the light beams 10 and 11 on the recording material 26 are shifted if the modulation start timings of the light beams 10 and 11 are aligned. Hereinafter, the point of preventing such a problem from occurring will be described.

As shown in FIGS. 2 and 3, a synchronization detecting means 43 is provided outside the effective main scanning range. As shown in FIG. 7, the synchronization detecting means 43 includes a shielding plate 44 having a sharp edge 44a through which the beam spots 10s and 11s pass, such as a knife edge, and an edge 44a of the shielding plate 44.
Light detector 45 that detects beam spots 10s and 11s through
And a signal processing circuit 46 to which the output signal Sy of the photodetector 45 is input.

During the period when the light beams 10, 11 pass over the photodetector 45, the driving of the semiconductor lasers 12, 13 is controlled so that the intensity of the light beams 10, 11 takes a predetermined constant value. Is done. In this case, the output signal Sy of the photodetector 45
Is basically as shown in FIG. The pulse-shaped waveform that rises first as time elapses is due to the detection of the beam spot 10s, and the pulse-shaped waveform that rises next is due to the detection of the beam spot 11s.

Therefore, the signal processing circuit 46 causes an interval (t2) between the times t1 and t2 when these pulse waveforms rise.
−t1) is obtained, and a signal St indicating this time interval is input to the modulation driving circuit 30 as shown in FIG. Modulation drive circuit
Reference numeral 30 denotes a modulation start timing for the light beam 11 (that is, for the semiconductor laser 13) based on the signal St.
The time (t2−t1) is delayed from the start of the modulation of the light beam 10 (that is, the semiconductor laser 12). Thereby, the recording start positions on the recording material 26 by the light beams 10 and 11 are aligned with each other.

By doing so, the beam spot 10
No matter how the positions of s and 11s fluctuate in the main scanning direction, there is no need to make any corrections.

The above method is for detecting light at a deflection scanning speed at the time of actually recording an image. When the interval between pulse-shaped waveforms is detected by setting the deflection scanning speed for detecting light to be ε times the deflection scanning speed for recording an image, the detected interval (t2−t1) is multiplied by ε. Alternatively, data indicating the value may be stored in a memory in advance, and the modulation start timing at the time of recording may be set using this value.

Also, using the detection system shown in FIG.
From the times t1 and t2, the recording start timing in the main scanning direction can be taken.

In this embodiment, as shown in FIG. 1, the light beams 10, 11 before being incident on the optical deflector 23.
And an aperture plate 50 for narrowing at least the beam width in the main scanning direction is provided. Such an opening plate 50
Is provided, the width of the mirror 24 of the optical deflector 23 in the main scanning direction can be reduced, whereby the rotational load of the optical deflector 23 can be reduced and high-speed scanning can be realized. The preferred range of the opening width Dl of the opening plate 50 in the main scanning direction is as described above.

Further, instead of such an aperture plate 50, the light beams 10, 11 before being incident on the optical deflector 23 are transmitted, and their intensity distribution characteristics at least in the main scanning direction are changed as they deviate from the beam center. The same effect can be obtained by using a filter having a gradually decreasing characteristic.

In this embodiment, as shown in FIG. 1, an AOD (acousto-optic light deflection) for controlling the overall traveling direction of the light beams 10 and 11 between the mirror 20 and the imaging lens 22 is used. Element) 51 is provided. In the inner drum type optical scanning device, the scanning line called bowing described above may be curved. In this case, the AOD 51 is driven in accordance with the scanning line curvature characteristic, and the light beam 10, This bowing can be eliminated by deflecting 11 at high speed.

Further, for example, by utilizing the modulation drive circuit 30 described above, the light beams 10 and 11 are scanned in a predetermined scanning range including the effective main scanning area (for example, between the synchronization detecting means 43 and the beam spot interval measuring means 40). The scanning of the semiconductor lasers 12 and 13 can be stopped during a period outside the scanning range. This prevents the light beams 10 and 11 deviating from the predetermined scanning range from being emitted by the mirror 24 of the optical deflector 23 and causing stray light.

Next, another embodiment of the present invention will be described. FIG. 9 shows a part of an optical scanning device according to a second embodiment of the present invention, and FIG. 10 shows an enlarged view of a main part thereof. In these figures, the same elements as those in FIG. 1 are denoted by the same reference numerals, and the duplicate description thereof will be omitted (the same applies hereinafter).

In the second embodiment, an optical deflector
A mirror 60 having a reflection surface inclined with respect to the mirror rotation axis Z is fixed to the holding member 31 to which the mirror 23 is fixed. The three light beams 61, 62, 63 travel substantially parallel to the mirror rotation axis Z, are reflected by the mirror 60, and enter the mirror 24 of the optical deflector 23.

In such a configuration, even if the mirror 60 moves in a direction parallel to the mirror rotation axis Z, the light beams 61, 62, 63 reflected there always have a fixed direction with respect to the optical deflector 23. Incident. Therefore, in this case, the holding member 31 is moved in a direction parallel to the mirror rotation axis Z by a driving unit (not shown), whereby the light beams 61, 62, and 63 are sub-scanned.

FIG. 11 shows a part of an optical scanning device according to a third embodiment of the present invention. In the third embodiment, the moving block 65 holds the optical deflector 23, the fixed mirror 64, and the synchronization detecting means 43, and the moving block 65 is parallel to the rotation axis of the mirror 24 of the optical deflector 23. In the direction (perpendicular to the plane of the paper)
2, 63 sub-scans are performed.

FIG. 12 shows a part of an optical system of an optical scanning device according to a fourth embodiment of the present invention. In the fourth embodiment, the light beams 10 and 11 emitted from the semiconductor lasers 12 and 13 are combined into a state close to one light beam by the beam splitter 17. In the optical path of one light beam 11, an optical element 70 having a wedge-shaped cross section that can swing in the direction of arrow R in the figure is inserted.

In this configuration, when the optical element 70 is swung, the angle between the light beams 10, 11 before entering the optical deflector changes. So that these light beams
The spots 10 and 11 change the interval in the sub-scanning direction on the recording material.

FIG. 13 shows a part of an optical system of an optical scanning device according to a fifth embodiment of the present invention. In the fifth embodiment, the light beams 10, 11 emitted from the semiconductor lasers 12, 13 are slightly diverged or converged when passing through the collimator lenses 14, 15, respectively. Thereby, the light beams are grouped into a state close to one light beam. In the optical path of one light beam 11, a parallel flat plate 71 that can swing in the direction of arrow R in the figure is inserted.

In this configuration, when the light beam 11 is slightly converged, when the parallel plate 71 is swung, the actual image position of the light beam 11 before entering the optical deflector is shown in FIG.
As shown by M1 and M2 in FIG. 14, it moves in a direction perpendicular to the optical axis. Thus, the spots of the light beams 10 and 11 change the interval in the sub-scanning direction on the recording material.

In this configuration, when the light beam 11 is slightly converged, if the parallel plate 71 is swung, the virtual image position of the light beam 11 before entering the optical deflector is shown in FIG.
As shown by N1 and N2 in FIG. 15, it moves in a direction perpendicular to the optical axis. Thus, the spots of the light beams 10 and 11 change the interval in the sub-scanning direction on the recording material.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an optical scanning device according to a first embodiment of the present invention.

FIG. 2 is a front view showing a main part of the optical scanning device of FIG. 1;

FIG. 3 is a perspective view showing a main part of the optical scanning device of FIG. 1;

FIG. 4 is an explanatory diagram illustrating a scanning locus of a light beam in the optical scanning device of FIG. 1;

FIG. 5 is a plan view showing a beam spot interval measuring unit used in the optical scanning device of FIG. 1;

FIG. 6 is a waveform chart showing an output signal waveform of the beam spot interval measuring means of FIG.

FIG. 7 is a plan view showing synchronization detection means used in the optical scanning device of FIG. 1;

FIG. 8 is a waveform chart showing an output signal waveform of the synchronization detecting means of FIG. 7;

FIG. 9 is a schematic perspective view showing a part of an optical scanning device according to a second embodiment of the present invention.

FIG. 10 is a perspective view showing a main part of the optical scanning device of FIG. 9;

FIG. 11 is a front view showing a part of an optical scanning device according to a third embodiment of the present invention.

FIG. 12 is a side view showing an optical system of an optical scanning device according to a fourth embodiment of the present invention.

FIG. 13 is a side view showing an optical system of an optical scanning device according to a fifth embodiment of the present invention.

14 is a schematic diagram illustrating movement of a beam spot in the sub-scanning direction in the apparatus of FIG.

15 is a schematic diagram illustrating movement of a beam spot in the sub-scanning direction in the apparatus of FIG.

FIG. 16 shows the relationship between the k value that determines the opening width Dl of the aperture plate that can be used in the present invention in the main scanning direction and the ratio (Db / Dl) of the beam diameter Db of the light beam in the main scanning direction to the opening width Dl. Graph

FIG. 17 is a graph showing the relationship between the light transmittance of the aperture plate and the ratio (Db / Dl).

[Explanation of symbols]

 10, 11, 10A, 10B Light beam 12, 13 Semiconductor laser 14, 15 Collimator lens 16 Wedge-shaped optical element 17 Beam splitter 18, 19 Lens 20, 21 Mirror 22 Imaging lens 23 Optical deflector 24 Optical deflector Mirror 25 Optical deflector drive means 26 Recording material 27 Platen 28 Female screw block 29 Precision screw 30 Modulation drive circuit 40 Beam spot interval measuring means 43 Synchronous detection means 50 Aperture plate 51 AOD 60 Fixed mirror 61, 62, 63 Light beam 64 Fixed mirror 65 Moving block 70 Wedge-shaped optical element 71 Parallel plate

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[Procedure amendment]

[Submission date] March 24, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

On the other hand, if the opening width Dl is too small, the light transmittance at the opening plate decreases, and the light use efficiency decreases. FIG. 17 shows the relationship between the value of Db / Dl and the light transmittance at the aperture plate. The light transmittance is shown as a relative value when the light transmittance without the aperture plate is set to 1. In general, the light transmittance is desirably about 0.1 or more in the above relative value. When the value of Db / Dl is 16, the light transmittance is 0.1.
Since it is 10, this 16 value is set as a preferable maximum value of Db / Dl. Further, since it is more preferable that the light transmittance is 0.3 or more of the relative value, the value 5 of Db / Dl at which the light transmittance becomes 0.31 is set as a more preferable maximum value.

Claims (23)

[Claims] 1. An optical deflector comprising: a light source device for emitting a plurality of light beams; a mirror; and a driving means for rotating the mirror about a rotation axis substantially included in a reflection surface thereof; A platen for curving and holding a recording material with the rotation axis substantially at the center of curvature at a position where main scanning is performed by the plurality of light beams reflected and deflected by the device; and Incident on the mirror at an angle to the plane perpendicular to the axis of rotation, with the light beams converging on a small beam spot on the recording material. An optical system for moving the platen and the optical deflector relative to each other in a direction parallel to the rotation axis. Optical scanning apparatus, wherein a means for changing the beam spot interval countercurrent provided. 2. The optical scanning device according to claim 1, wherein the means for changing the beam spot interval is a means for changing the interval between a plurality of light beams before entering the optical deflector. 3. A beam expander or a beam reducer for changing the interval between a plurality of light beams before entering the optical deflector, the beam expander or the beam reducer passing the light beams together. Optical scanning device. 4. A means for changing the interval between a plurality of light beams before entering the light deflector is a parallel flat plate which transmits the light beams and is capable of changing the inclination angle with respect to the light beams. The optical scanning device according to claim 2, wherein: 5. A wedge-shaped optical section in which means for changing the interval between a plurality of light beams before entering the optical deflector transmits the light beams and the inclination angle with respect to the light beams is changeable. 3. The device according to claim 2, wherein the device is an element.
The optical scanning device according to claim 1. 6. The optical scanning device according to claim 1, wherein the means for changing the beam spot interval is means for changing an angle formed by a plurality of light beams before entering the optical deflector. . 7. A beam expander or a beam reducer for changing an angle formed by a plurality of light beams before entering the light deflector, the beam expander or the beam reducer passing the light beams together. 7. The optical scanning device according to 6. 8. A means for changing an angle formed by a plurality of light beams before entering the light deflector, wherein the means for transmitting the light beams is a parallel flat plate which is capable of changing the inclination angle with respect to the light beams. 7. The optical scanning device according to claim 6, wherein: 9. A wedge-shaped cross section in which means for changing the angle formed by a plurality of light beams before entering the light deflector transmits the light beams and makes the inclination angle with respect to the light beams variable. The optical scanning device according to claim 6, wherein the optical scanning device is an optical element. 10. The light source device according to claim 1, wherein the means for changing the beam spot interval is configured to form a part of the light source device by branching one light beam before entering the optical deflector. The optical scanning device according to any one of claims 1 to 9, wherein: 11. The optical scanning device according to claim 10, wherein the means for changing the beam spot interval is a multi-frequency AOD. 12. The optical scanning device according to claim 11, wherein the multi-frequency AOD has an AOM function. 13. An aperture plate for passing one or a plurality of light beams before entering the optical deflector and narrowing at least the beam width thereof in the main scanning direction. 13. The optical scanning device according to any one of items 1 to 12. 14. When the beam diameter (1 / e ² diameter) of the light beam in the main scanning direction is Db and the opening width of the aperture plate in the main scanning direction is Dl, the value of Db / Dl is 0.7. The optical scanning device according to claim 13, wherein the optical scanning device is in a range from 16 to 16. 15. The optical scanning device according to claim 14, wherein the value of Db / Dl is in a range of 1.0 to 5. 16. A filter that transmits one or a plurality of light beams before entering the optical deflector and has a characteristic that at least their intensity distribution characteristics in the main scanning direction gradually decrease as they deviate from the beam center. The optical scanning device according to claim 1, wherein the optical scanning device is provided. 17. The beam diameter (1 / e ² diameter) of the light beam in the main scanning direction is Db, and the filter width in a range where the transmittance of the filter takes a value from a maximum value to a half thereof is D.
17. The optical scanning device according to claim 16, wherein the value of Db / Dl 'is in the range of 0.7 to 16, where 1'. 18. The optical scanning device according to claim 17, wherein the value of Db / Dl ′ is in a range from 1.0 to 5. 19. A means for measuring a beam spot interval in the sub-scanning direction on the recording material is provided, and the means for changing the beam spot interval is driven based on an output of the beam spot interval measuring means. 19. The optical scanning device according to claim 1, wherein the optical scanning device is configured as follows. 20. A synchronous detecting means for detecting a time interval at which the plurality of beam spots pass a predetermined position in the main scanning direction, and a modulation start position of each light beam is recorded on the basis of an output of the synchronous detecting means. 2. A modulating means for modulating each light beam while controlling the modulation start timing of each light beam so as to be aligned with each other on the material.
The optical scanning device according to any one of items 1 to 17, wherein 21. A control device for controlling the light source device to stop driving during a period when the light beam is out of a predetermined scanning range including an effective main scanning area. The optical scanning device according to claim 1. 22. The optical scanning device according to claim 1, further comprising means for controlling the overall traveling directions of the plurality of light beams before entering the light deflector. apparatus. 23. An optical system for converging the plurality of light beams to a beam spot on the recording material, comprising an imaging lens inserted in an optical path of the light beam before entering the light deflector. 23. The optical scanning device according to claim 1, wherein: