JP2000249946A - Multibeam scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust beam pitch. SOLUTION: This device is provided with cylindrical lenses 3a and 3b condensing beams 18 and 19 in a sub-scanning direction, an optical path correction means 14 correcting the optical path of the beam 19, a beam splitter 4 aligning the optical axes of the beams 18 and 19, a deflector 5 deflecting the beams 18 and 19, a sensor part 11 detecting the output levels of the beams 18 and 19, a knife edge 13 installed in the optical paths of the beams 18 and 19 between the splitter B and the sensor part 11 so as to shield the beams 18 and 19 advancing to the sensor part 11 from the splitter 4, a knife edge adjustment means 22 moving the edge 13 in the sub-scanning direction and an optical path correction driving means 15 controlling the actions of the correction means 14 and the adjustment means 22 based on the output of the sensor part 11.

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 apparatus such as an electrophotographic apparatus for forming an image by scanning a plurality of beams.

[0002]

2. Description of the Related Art Conventionally, a beam scanning optical system has been used for image writing in an electrophotographic process, and is mounted on a computer, a laser beam printer or a laser facsimile which is an output device of a facsimile. Recently, a demand for a multi-beam scanning device that scans a plurality of beams has been increasing in order to further increase the speed and the resolution.

Hereinafter, a conventional multi-beam scanning apparatus that scans a multi-beam will be described. Here, FIG. 5 is a schematic view showing a conventional multi-beam scanning device.

As shown in FIG. 5, a driving means 20 for driving a first light source 1a to irradiate a beam 18, and a second
A driving means 21 for driving the light source 1b to emit the beam 19 is provided. And the first light source 1
a from the light source a and the beam 19 from the second light source 1b
Is applied, an electrostatic latent image is formed on the scanned surface 10 a of the photosensitive drum 10 that is uniformly charged.

A collimator lens 2a is arranged corresponding to the first light source 1a, and a collimator lens 2b is arranged corresponding to the second light source 1b.
Beams 18 and 19 from these collimator lenses 2
The light is made parallel by a and 2b.

On the optical paths of the beams 18 and 19 passing through the collimator lenses 2a and 2b, cylindrical lenses 3a and 3b for condensing the beams 18 and 19 from the light sources 1a and 1b in the sub-scanning direction, and the light sources 1a and 3b, respectively. A beam splitter 4 for aligning the optical axes of the beams 18 and 19 emitted from 1b is provided. Also, corresponding to the cylindrical lenses 3a and 3b, optical path correcting means 14a and 14b for rotating the respective cylindrical lenses 3a and 3b to adjust the pitch of the beams 18 and 19 in the sub-scanning direction to a predetermined interval are provided. Is provided. This optical path correction means 1
4a and 14b are driven by the optical path correction driving means 15.

Further, a deflection surface 6 is provided on the optical path of the beams 18 and 19 from the beam splitter 4 to the photosensitive drum 10.
A deflector 5 for simultaneously deflecting the two beams 18 and 19, a scanning lens system 7 for condensing the beams 18 and 19 deflected by the deflector 5 onto a surface 10a to be scanned of the photosensitive drum 10, and scanning the beam. Mirrors 8 for guiding the mirrors 18 and 19 to the surface to be scanned 10a are sequentially arranged.

The deflection surface 6 on the optical path of the beams 18 and 19 emitted from the beam splitter 4 in a direction different from that of the deflection surface 6
A sensor unit 11 that detects a pitch interval between the beams 18 and 19 in the sub-scanning direction is disposed at a position optically equivalent to the above. The sensor unit 11 includes a photo sensor 12 having a light receiving surface 16. In addition, the beam splitter 4
A knife edge 13 serving as a reference for beam alignment is arranged between the optical paths of the sensor 11 and the sensor unit 11.

The beam 18, scanned by the deflector 5,
A synchronization detector 9 is arranged to synchronize the main scanning direction 19. And, by this synchronization detector 9,
Irradiation of the beams 18 and 19 corresponding to the image data at the timing of a predetermined time is performed by the driving unit 2 of each of the light sources 1a and 1b.
0,21.

[0010] Members other than the photosensitive drum 10 are housed in a housing 17.

The operation of the multi-beam scanning device configured as described above will be described below.

First, beam scanning on the scanned surface 10a will be described.

The beams 18 and 19 emitted from the first light source 1a and the second light source 1b in FIG.
The beam is adjusted to a parallel beam by the collimator lenses 2a and 2b. Next, the beams 18 and 19 are narrowed down in the sub-scanning direction by the cylindrical lenses 3a and 3b.

The beams 18 and 19 have their optical axes aligned by the beam splitter 4 and deflected by the deflector 5. The deflected beams 18 and 19 are condensed on the photosensitive drum 10 by the scanning lens system 7 and scan the scanned surface 10a.

Beams 18, 1 for scanning the surface 10a to be scanned
9 passes the synchronization detector 9 provided in front of the print area, so that the timing of writing in the print area is set. Then, based on this timing, a beam irradiation corresponding to the image data is performed on the scanned surface 10a.

In such a multi-beam scanning apparatus, it is important to accurately maintain the interval between a plurality of beams scanned simultaneously, that is, the pitch in the sub-scanning direction (hereinafter, referred to as "beam pitch").

It is desirable that the beam pitch is adjusted to a predetermined interval when assembling the scanning device, and that the beam pitch is maintained for a long period of time. It is difficult to keep only stable. Therefore, a technique has been proposed in which the beam pitch is periodically corrected to ensure the accuracy of the beam pitch. The conventional technique of FIG. 5 which has already been described is also a type of multi-beam scanning apparatus for correcting a beam pitch.

Next, adjustment of the beam pitch in the conventional multi-beam scanning device will be described.

Conventionally, the beam pitch is adjusted in advance by a beam pitch adjusting jig (not shown) provided on the scanned surface 10a when assembling the multi-beam scanning device. Therefore, first, adjustment of the beam pitch when assembling the multi-beam scanning device will be described.

When the necessary components are incorporated in the housing 17, first, the driving means 20 of the first light source 1a causes the beam 18 of the first light source 1a to emit light.
The emitted beam 18 sequentially passes through the collimator lens 2a, the cylindrical lens 3a, and the beam splitter 4, and is separated into a beam 18 toward the deflection surface 6 of the deflector 5 and a beam 18 toward the sensor unit 11. The beam 18 directed to the deflecting surface 6 is used as light for irradiating the scanned surface 10a, and the beam 18 directed to the sensor unit 11 is guided to the photosensor 12 to detect a beam pitch position.

In front of the photosensor 12, a knife edge 13 serving as a reference for beam alignment is provided at a position optically equivalent to the deflection surface 6. Thus, the cylindrical lens 3a is rotated by the optical path correction driving means 15 to move the beam 18 of the first light source 1a in the sub-scanning direction.

Here, FIG. 6 shows the cylindrical lens 3.
FIG. 4 is an explanatory diagram showing a state in which a beam 18 of the first light source 1a is moved in the sub-scanning direction by a.

As shown in FIG. 6, a parallel light beam 18 incident on the cylindrical lens 3a is focused on the optical axis of the cylindrical lens 3a. Here, when the cylindrical lens 3a is moved in the sub-scanning direction (vertical direction in FIG. 6), the incident beam 18 is focused on the optical axis of the moved cylindrical lens 3a, so that the irradiation position on the deflection surface 6 is changed. Be changed. Thus, the first light source 1
The beam 18 from a and the beam 19 from the second light source 1b are respectively moved to predetermined positions in the sub-scanning direction.

On the other hand, the beam 18 traveling to the sensor 11
Is blocked by the knife edge 13. Therefore, the light amount of the beam 18 reaching the photosensor 12 of the sensor unit 11 behind the knife edge 13 changes, and the output level from the photosensor 12 changes.

FIG. 7 shows the optical path correcting means 14a, 1
FIG. 7 is an explanatory diagram showing sensor outputs based on the positional relationship between the positions of beams 18 and 19 in the sub-scanning direction, the optical paths of which are corrected by 4b, and the knife edge 13.

As described above, the knife edge 13 and the beam 1
Since the output level of the photosensor 12 changes depending on the positional relationship with the position 8, the sub-scanning positions of the knife edge 13 and the beam 18 can be known from this output level.

That is, the beam 18 is moved, and the position of the beam 18 is determined based on the output level Va of the photosensor 12. Then, this value is set to a fixed value. However, beam 1
It is necessary to consider the value of 9 predetermined value Vb. The output level Va may be any output level. Thus, the relative position between the knife edge 13 and the beam 18 at the output level Va is determined. Thus, the adjustment of the position of the beam 18 is completed.

Next, the position of the beam 19 is adjusted in the same manner. However, the output level Vb corresponding to the beam position of the second light source 1b is determined based on the output level VL from the photosensor 12 at the beam position where the beam pitch between the beam 19 and the beam 18 is at a predetermined interval L. Set. That is, when the position of the beam 18 determined by the above-described beam pitch adjusting jig is detected, and the output level when the beam 19 is moved from the position to the interval L is VL, the output level Vb becomes It becomes equal to the value of the output level VL. Therefore, the output level Vb can be adjusted using components such as a variable volume so as to correspond to the output level VL obtained by the adjustment.

The beam interval on the deflecting surface 6 is adjusted by directly observing the beam pitch on the surface 10a to be scanned, and optically has the following relationship. Here, FIG. 8 is an explanatory diagram illustrating an optical relationship between the deflection surface 6 in the sub-scanning direction and the scanned surface 10a.

As shown, the beam pitch BP2 on the scanned surface 10a is obtained by multiplying the beam pitch BP1 on the deflection surface 6 by the magnification M of the scanning lens system 7 in the sub-scanning direction. That is, BP2 = M × BP1.

By determining the output levels Va and Vb of the beams 18 and 19 as described above, the beam pitch is adjusted at the time of assembling the multi-beam scanning device. Then, the multi-beam scanning device adjusted in this way is incorporated in the printing device. Thereafter, by periodically adjusting the beam 18 to the output level Va and the beam 19 to the output level Vb, the beam pitch is maintained at the interval L, and high print quality can be always maintained.

As described above, by adjusting the beam pitch at the time of assembling and performing the correction periodically, a multi-beam scanning apparatus that can secure a stable beam pitch even with aging and environmental changes can be obtained.

[0033]

However, in the prior art as described above, since the criterion for determining the position of each beam in the sub-scanning direction is the knife edge, the beam is moved depending on the mounting position of the knife edge. The beam position of the first light source varies among the multi-beam scanning devices. Then, the beam may deviate from the deflection surface of the thin deflector.

In addition, since the optical paths of the beams emitted from the first light source and the second light source must be adjusted, the assemblability and workability are poor, and mass production cannot be performed.

Accordingly, an object of the present invention is to provide a multi-beam scanning device capable of easily adjusting a beam pitch.

It is another object of the present invention to provide a multi-beam scanning device capable of improving mass productivity.

[0037]

To solve this problem, a multi-beam scanning apparatus according to the present invention comprises two light sources for irradiating a beam and two driving means for independently driving the light sources to irradiate the beam. And two collimator lenses that are installed in correspondence with the respective beams emitted from the light source and convert these beams into parallel light, and are installed in correspondence with the respective beams emitted from the collimator lenses, and Two cylindrical lenses for converging light in the sub-scanning direction, an optical path correcting means for moving one of the cylindrical lenses in the sub-scanning direction to correct the optical path of the beam passing through the cylindrical lens, and emitting from the cylindrical lens A beam splitter that makes the optical axes of the two beams coincide with each other and a beam splitter that emits two beams emitted from the beam splitter. A deflector that deflects the beam, a scanning lens system that scans the two beams deflected by the deflector on the surface to be scanned, a synchronization detector that detects synchronization of the two beams in the main scanning direction, and a deflection from the beam splitter. A sensor unit that is provided on an optical path of two beams emitted in directions different from the surface and is optically equivalent to the deflection surface, and that detects an output level of these beams; a beam splitter and a sensor unit; A knife edge installed between the optical paths of the two to block two beams from the beam splitter toward the sensor unit;
A knife edge adjusting unit that moves the knife edge in the sub-scanning direction; and an optical path correction driving unit that controls the operation of the optical path correcting unit and the knife edge adjusting unit based on the output of the sensor unit. Then, the position of the knife edge is determined based on this beam, and then the beam on the side whose optical path is corrected by the optical path correcting means is moved in the sub-scanning direction to adjust the beam pitch.

As a result, the optical path of one beam is fixed, and the position of the knife edge and the position of the other beam are sequentially determined based on this beam position. The beam pitch can be easily adjusted.

Also, since the optical path of one beam is fixed, parts related to the fixed beam can be assembled in the same manner as a single beam scanning device, so that assembly is easy and workability is improved. It is possible to improve the mass productivity.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there are provided two light sources for irradiating a beam, two driving means for independently driving the light sources to irradiate a beam, and a light source for irradiating a beam. Two collimator lenses are installed corresponding to the respective beams and collimate these beams, and are installed corresponding to the respective beams emitted from the collimator lenses, and collect these beams in the sub-scanning direction. Two cylindrical lenses, an optical path correcting means for moving one of the cylindrical lenses in the sub-scanning direction to correct an optical path of a beam passing through the cylindrical lens, and an optical axis of the two beams emitted from the cylindrical lens A beam splitter for matching the two beams, a deflector for deflecting two beams emitted from the beam splitter on a deflecting surface, and a deflector for deflecting the two beams. A scanning lens system for scanning the two beams on the surface to be scanned, a synchronous detector for detecting the synchronization of the two beams in the main scanning direction, and two beams emitted from the beam splitter in directions different from the deflection surface A sensor unit that is provided at a position optically equivalent to the deflecting surface on the optical path and detects the output level of these beams, and is installed between the optical paths of the beam splitter and the sensor unit. A knife edge for blocking the two beams directed toward the scanner, a knife edge adjusting means for moving the knife edge in the sub-scanning direction, an optical path correction driving means for controlling the operation of the optical path correcting means and the knife edge adjusting means based on the output of the sensor unit, The position of the knife edge is determined based on the beam on the side not subjected to the optical path correction by the optical path correction unit, and then the optical path correction unit performs the optical path correction. Which is moved to the side of the beam in the sub-scanning direction is a multi-beam scanning device for adjusting the beam pitch, it has the effect that it is possible to adjust the beam pitch easily. Further, there is an effect that it is possible to improve mass productivity.

According to a second aspect of the present invention, in the first aspect of the invention, a plurality of output levels from the sensor unit of the beam whose optical path is to be corrected by the optical path correcting means are set, and one of the output levels is set. This is a multi-beam scanning device that adjusts the beam to a level, and has the effect of enabling high-speed printing by switching the resolution in the sub-scanning direction.

According to a third aspect of the present invention, in the first or second aspect, a condenser lens for condensing a beam on the sensor section is provided between the optical path of the sensor section and the beam splitter. Is a multi-beam scanning device,
This has the effect of reducing the beam direction accuracy and improving the assemblability. Further, there is an effect that the selection range of the photosensor is widened and the cost can be reduced. Further, there is an effect that the S / N ratio of the sensor output level is improved.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a schematic view showing a multi-beam scanning apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory view showing adjustment of a beam pitch, and FIG. 3 is an explanatory view showing a case where a plurality of beam pitches are provided. FIG. 4 and FIG. 4 are explanatory diagrams showing the fluctuation of the optical path when the condenser lens is inserted and when it is not inserted.

As shown in FIG. 1, a driving means 20 for driving a first light source 1a to irradiate a beam 18,
A driving means 21 for driving the light source 1b to emit the beam 19 is provided. And the first light source 1
a from the light source a and the beam 19 from the second light source 1b
Is applied, an electrostatic latent image is formed on the scanned surface 10 a of the photosensitive drum 10 that is uniformly charged.

A collimator lens 2a is arranged corresponding to the first light source 1a, and a collimator lens 2b is arranged corresponding to the second light source 1b.
Beams 18 and 19 from these collimator lenses 2
The light is made parallel by a and 2b.

On the optical paths of the beams 18 and 19 having passed through the collimator lenses 2a and 2b, cylindrical lenses 3a and 3b for condensing the beams 18 and 19 from the respective light sources 1a and 1b in the sub-scanning direction, and the respective light sources 1a and 3b. A beam splitter 4 for aligning the optical axes of the beams 18 and 19 emitted from 1b is provided. In addition, an optical path correcting means 14 is provided corresponding to the cylindrical lens 3b for rotating the cylindrical lens 3b to adjust the pitch of the beam 19 emitted from the second light source 1b in the sub-scanning direction to a predetermined interval. Have been.

Further, on the optical path of the beams 18 and 19 from the beam splitter 4 to the photosensitive drum 10, a deflecting surface 6 is provided.
A deflector 5 for simultaneously deflecting the two beams 18 and 19, a scanning lens system 7 for condensing the beams 18 and 19 deflected by the deflector 5 onto a surface 10a to be scanned of the photosensitive drum 10, and scanning the beam. Mirrors 8 for guiding the mirrors 18 and 19 to the surface to be scanned 10a are sequentially arranged.

The deflection surface 6 on the optical path of the beams 18 and 19 emitted from the beam splitter 4 in a direction different from that of the deflection surface 6
A sensor unit 11 that detects a pitch interval between the beams 18 and 19 in the sub-scanning direction is disposed at a position optically equivalent to the above. The sensor unit 11 includes a photo sensor 12 having a light receiving surface 16. In addition, the beam splitter 4
A knife edge 13 serving as a reference for beam alignment is arranged between the optical paths of the sensor 11 and the sensor unit 11.

Corresponding to the knife edge 13, a knife edge adjusting means 22 for moving the knife edge 13 in the sub-scanning direction and adjusting the position thereof is provided. The optical path correcting means 14 and the knife edge adjusting means 22 are driven by the optical path correcting driving means 15.

A condensing lens 23 for condensing beams 18 and 19 on the light receiving surface 16 of the photosensor 12 is disposed between the optical path between the beam splitter 4 and the photosensor 12.

The beam 18 scanned by the deflector 5
A synchronization detector 9 is arranged to synchronize the main scanning direction 19. And, by this synchronization detector 9,
Irradiation of the beams 18 and 19 corresponding to the image data at the timing of a predetermined time is performed by the driving unit 2 of each of the light sources 1a and 1b.
0,21.

Members other than the photosensitive drum 10 are housed in a housing 17.

The beam scanning in the multi-beam scanning device configured as described above will be described.

The beams 18 and 19 emitted from the first light source 1a and the second light source 1b, respectively, are adjusted to parallel beams by the collimator lenses 2a and 2b, and are narrowed down in the sub-scanning direction by the cylindrical lenses 3a and 3b. Then, the optical axes are aligned by the beam splitter 4 and deflected by the deflector 5. Deflected beam 1
Numerals 8 and 19 are condensed on the photosensitive drum 10 by the scanning lens system 7 and scan the scanned surface 10a.

The beams 18, 1 for scanning the surface 10a to be scanned
9 passes the synchronization detector 9 provided in front of the print area, so that the timing of writing in the print area is set. Then, based on this timing, a beam irradiation corresponding to the image data is performed on the scanned surface 10a.

Since the scanned surface 10a moves in the sub-scanning direction (perpendicular to the beam scanning direction), a two-dimensional image is written on the scanned surface 10a. For such beam scanning, a single beam 1
Same as 1-beam scanning device scanning at 8 and 19, but
In a multi-beam scanning device, a plurality of beams 18, 1
Since 9 is scanned, the image forming speed can be increased and the image quality can be increased.

Next, adjustment of the beam pitch will be described.

The adjustment of the beam pitch is performed after necessary components are assembled in the housing 17.

The beam 18 from the first light source 1a has a fixed optical path, and therefore, this beam 18 becomes a reference beam. Therefore, assembling of parts not related to the beam 19 emitted from the second light source 1b is performed in a manner similar to that of the single beam scanning device, and assemblability is improved.

For adjusting the beam pitch, first, the reference beam 18 (the beam 19 when the optical path of the beam 19 emitted from the second light source 1b is fixed) is emitted. Thereby, a part of the beam 18 is guided to the sensor unit 11 that detects the beam position.

When the beam 18 is guided as described above,
The knife edge 13 is moved in the sub-scanning direction by the knife edge adjusting means 22. Then, along with the movement of the knife edge 13, the beam 18 traveling from the beam splitter 4 to the sensor unit 11 is blocked by the knife edge 13, the output level from the photo sensor 12 changes, and stops at the predetermined output level Vn. Therefore, the output level Vn in consideration of the output level of the beam 19 is set to a fixed value.

With the above operation, the position of the knife edge 13 is determined. At this time, the position of the beam 18 on the scanned surface 10a is detected by a beam pitch position adjusting jig (not shown).

Next, the light emission from the first light source 1a is stopped, and the beam 19 is emitted from the second light source 1b. Then, the optical path correcting means 14 causes the cylindrical lens 3
b is moved in the sub-scanning direction, and while monitoring the position of the beam 19 with the beam pitch position adjusting jig, the optical path correcting means 14 is stopped at a position where a predetermined beam pitch is obtained. The predetermined level Vb of the beam 19 is adjusted to the sensor output value at this time.

As described above, the predetermined level Vn corresponding to the stop position of the knife edge 13 and the predetermined level Vb corresponding to the beam 19 are set at the time of assembling the multi-beam scanning apparatus, so that when the multi-beam scanning apparatus is mounted, it is always mounted on the printing apparatus. It is controlled to be at this level.

Next, adjustment of the beam pitch will be described.

The distance between the beam 18 of the first light source 1a and the knife edge 13 is x, the distance between the beam 19 of the second light source 1b and the knife edge 13 is y, and the distance between the beam 18 and the beam 19 is x + y. This x + y is the beam pitch (for example, 42 μm at a resolution of 600 dpi).

As described above, conventionally, the beams 18 and 19 are moved based on the knife edge 13 to adjust the beam pitch. On the other hand, in the present invention, the position of the knife edge 13 is determined based on the position of the beam 18, and thereafter, the beam 19 is
Is determined.

The multi-beam scanning device thus adjusted is mounted on a printing device, and the beam pitch is adjusted each time printing is started or periodically. The periodic control of the beam pitch adjusts the position of the knife edge 13 by the knife edge adjusting means 22 so that the output level of the photo sensor 12 with respect to the beam 18 becomes Va. Then, the position of the beam 19 is adjusted by the optical path correcting means 14 until the output level of the photosensor 12 at the beam 19 becomes Vb with respect to the position of the knife edge 13 thus adjusted. Since the beam pitch is adjusted within a few seconds when the deflector 5 reaches a predetermined speed, the first printing speed is not delayed.

As described above, according to the present embodiment, the optical path of one beam is fixed, and the position of knife edge 13 and the position of the other beam are sequentially determined based on this beam position. It is only necessary to adjust the missing beam, and the beam pitch can be easily adjusted.

Also, since the optical path of one beam is fixed, parts related to the fixed beam can be assembled in the same manner as a single beam scanning device, so that assembly is easy and workability is improved. It is possible to improve mass productivity.

With the above configuration, the beam pitch can be stably maintained regardless of the aging of the apparatus and the environmental change.

Here, by providing a plurality of levels for determining the beam position of the second light source 1b, the beam pitch can be set to an arbitrary interval.

FIG. 3 shows a case where a plurality of beam pitches are provided.

In FIG. 3, when the sensor output levels when the beam 19 is provided at distances L1, L2, and L3 from the beam 18 are V1, V2, and V3, the output levels Vb for stopping the beam 19 are V1, V2, and V3. By selecting any one of V3, the beam pitch can be switched to an arbitrary value.

If the beam pitch can be switched in this way, it is advantageous when it is desired to switch the resolution in the sub-scanning direction. For example, in a multi-beam scanning device having a beam pitch of only 600 DPI, the resolution is set to 1200 DPI.
When it is desired to change the scanning to one beam, the beam pitch is 600 DPI.
The conventional printing speed is reduced to 1/4. On the other hand, in the case of the present multi-beam scanning device, 600 DPI is set to 1
When switching to 200 DPI, two-beam scanning becomes possible by switching the beam pitch.
There is a merit that can be output with 2.

Further, a condenser lens 23 is provided between the beam splitter 4 and the photo sensor 12 so that the photo sensor 1
By condensing the beam on the second light receiving surface 16, the accuracy of the optical path to the photo sensor 12 can be reduced, and the assemblability can be improved.

That is, as shown in FIG. 4A, when the condenser lens 23 is inserted, the function of guiding the beam to the photosensor 12 works, so that even if the optical path to the photosensor 12 varies, The beam can be guided in a stable manner, the directional accuracy of the beam can be reduced, and the assemblability can be improved. In addition, since a photosensor 12 having a small light receiving area can be used, the selection range of a general-purpose photosensor is widened, and there is a cost advantage. Furthermore, since most of the light beam amount is incident on the photosensor 12, the S / N ratio of the sensor output level can be improved.

[0079]

As described above, according to the present invention, the optical path of one beam is fixed, and the position of the knife edge and the position of the other beam are sequentially determined based on this beam position. It is only necessary to adjust a beam that does not exist, and an effective effect that the beam pitch can be easily adjusted can be obtained.

Further, according to the present invention, since the optical path of one beam is fixed, parts related to the fixed beam can be assembled in the same manner as a single-beam scanning device. However, there is an advantageous effect that the workability is good, the workability is good, and the mass productivity can be improved.

By setting a plurality of output levels of the beam whose optical path is to be corrected by the optical path correcting means, it is possible to obtain an effective effect that high-speed printing can be performed by switching the resolution in the sub-scanning direction.

By providing a condensing lens between the optical path of the sensor section and the beam splitter, the beam can be stably guided to the photosensor by the condensing lens, so that the directional accuracy of the beam can be relaxed and the assembling property can be reduced. An effective effect of improving is obtained.

Further, by providing the condenser lens, a photosensor having a small light receiving area can be used, so that an effective effect that the selection range of the photosensor can be widened and the cost can be reduced can be obtained.

Further, by providing a condenser lens,
Since most of the beam light quantity is incident on the photo sensor, an effective effect of improving the S / N ratio of the sensor output level can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing adjustment of a beam pitch.

FIG. 3 is an explanatory diagram showing a case where a plurality of beam pitches are provided.

FIG. 4 is an explanatory diagram showing a change in an optical path when a condenser lens is inserted and when it is not inserted.

FIG. 5 is a schematic diagram showing a conventional multi-beam scanning device.

FIG. 6 is an explanatory diagram showing a state where a beam of a first light source is moved in a sub-scanning direction by a cylindrical lens.

FIG. 7 is an explanatory diagram showing a sensor output based on a positional relationship between a position in a sub-scanning direction of a beam whose optical path has been corrected by an optical path correcting unit and a knife edge.

FIG. 8 is an explanatory diagram showing an optical relationship between a deflection surface in a sub-scanning direction and a surface to be scanned.

[Explanation of symbols]

 1a First light source 1b Second light source 2a, 2b Collimator lens 3a, 3b Cylindrical lens 4 Beam splitter 5 Deflector 6 Deflection surface 7 Scanning lens system 9 Synchronous detector 10a Scanned surface 11 Sensor unit 13 Knife edge 14 Optical path correction Means 15 Optical path correction driving means 20, 21 Driving means 22 Knife edge adjusting means 23 Condensing lens

Claims (3)

[Claims] 1. Two light sources for irradiating a beam, two driving means for independently driving the light source to irradiate a beam, and installed in correspondence with each of the beams emitted from the light source. Two collimator lenses for collimating the beams, two cylindrical lenses installed corresponding to the respective beams emitted from the collimator lenses, and condensing these beams in the sub-scanning direction; Optical path correction means for moving the cylindrical lens in the sub-scanning direction to correct the optical path of the beam passing through the cylindrical lens; a beam splitter for matching the optical axes of the two beams emitted from the cylindrical lens; A deflector for deflecting two beams emitted from the splitter on a deflecting surface; A scanning lens system for scanning two beams on the surface to be scanned, a synchronization detector for detecting synchronization of the two beams in the main scanning direction, and two beams emitted from the beam splitter in directions different from the deflection surface A sensor unit provided on the optical path and optically equivalent to the deflecting surface, for detecting the output level of these beams, and installed between the optical paths of the beam splitter and the sensor unit; A knife edge that shields two beams from the splitter toward the sensor unit, a knife edge adjustment unit that moves the knife edge in the sub-scanning direction, an optical path correction unit and the knife edge adjustment unit that are output from the sensor unit. Optical path correction driving means for controlling the operation of the knife edge based on the beam on the side of which optical path correction is not performed by the optical path correction means. Position is determined, then the multi-beam scanning apparatus according to claim moving the side of the beam optical path compensation in the sub-scanning direction by adjusting the beam pitch by the optical path correction means. 2. The apparatus according to claim 1, wherein a plurality of output levels from the sensor section of a beam whose optical path is corrected by the optical path correcting means are set, and the beam is adjusted so as to be any one of the output levels. Item 2. The multi-beam scanning device according to Item 1. 3. The multi-beam scanning device according to claim 1, wherein a condensing lens for condensing a beam on the sensor unit is provided between an optical path between the sensor unit and the beam splitter. apparatus.